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Title
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Long-Term Nuclear Waste Forecasting for Liquid-Fueled Nuclear Reactors: A Comprehensive Long-term Analysis of Liquid-Fueled Nuclear Reactor Fission and Transmutation Products and Associated Environmental Concerns
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Date
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2016
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Creator
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Taylor, Greg S
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Subject
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Environmental Studies
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extracted text
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LONG-TERM NUCLEAR WASTE FORECASTING FOR LIQUIDFUELED NUCLEAR REACTORS:
A COMPREHENSIVE LONG-TERM ANALYSIS OF LIQUID-FUELED
NUCLEAR REACTOR FISSION AND TRANSMUTATION PRODUCTS AND
ASSOCIATED ENVIRONMENTAL CONCERNS
By
Greg S. Taylor
A Thesis
Submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
June 2016
i
© 2016 by Greg Taylor. All rights reserved.
ii
This Thesis for the Master of Environmental Studies Degree
By
Greg Taylor
has been approved for
The Evergreen State College
by
________________________
Kathleen Saul
Member of the Faculty
______________________
Date
iii
Abstract
Nuclear energy doesn’t have the best track record when it comes to environmental
safety, so when a new technology comes along promising to be the “end all” solution to
the worlds energy woes, skepticism is advised. Since the late 1990’s, Liquid Fueled
Nuclear Reactors [LFNR] have become a more popular topic within the energy science
community. Since the early work at Oak Ridge National Laboratory by Alvin Weinberg
to the more recent Liquid Fluoride Thorium Reactor [LFTR] designs, the literature has
shown the technical viability of LFNR tech. However little analysis into the long-term
waste, and how that waste will affect both the Earth and its collective inhabitants. This
thesis provides the framework necessary to understand the differences between Solid
Fueled Nuclear Reactors [SFNR] and LFNR, from the perspective of waste output. By
understanding what comes out the “back end” of a LFNR facility, policy makers can
better evaluate the long-term impacts of the technology. As the primary opposition to
nuclear energy is the very dangerous, long-lived fission waste generated by nuclear
reactors, and the most touted “fact” about LFNR systems is their drastically reduced
production of high-level waste and extremely high energy density, it seems prudent to
analyze the expected waste output to verify the claim itself. Through detailed
examination, this thesis will show that the available data does appear to support the
claims being made about LFNR tech and will provide a foundation for future research.
This analysis shows LFNR waste mass is in fact as much as 32x less volume than
comparative SFNR waste, the volume of long-lived waste produced by LFNR is a lower
overall portion of the final waste mass in general, and LFNR facilities would be safer to
operate, in terms of “potential catastrophic failure” chance.
Table of Contents
Table of Contents ............................................................................................................... iv
1.1)
List of Figures .................................................................................................... vii
1.2)
List of Tables ..................................................................................................... viii
Acknowledgements ............................................................................................................. x
2)
Introduction ................................................................................................................. 1
3)
History of Liquid Fueled Nuclear Reactors ................................................................ 4
4)
5)
6)
3.1)
Pre 2000................................................................................................................ 4
3.2)
2000 - Future ........................................................................................................ 8
Reactor Characteristics & Chemistry........................................................................ 11
4.1)
Solid Fueled Reactors Core Chemistry .............................................................. 11
4.2)
Liquid Fueled Reactors Core Chemistry ............................................................ 13
Model ........................................................................................................................ 17
5.1)
Chosen Variables................................................................................................ 18
5.2)
Assumptions Made ............................................................................................. 23
5.3)
Other Considerations .......................................................................................... 25
5.4)
Considerations .................................................................................................... 27
Findings..................................................................................................................... 30
6.1)
Uranium-233 [233U] Waste Analysis .................................................................. 41
6.1.a)
Gaseous ....................................................................................................... 42
iv
6.1.b)
Stable Solids................................................................................................ 43
6.1.c)
90 Day Resting Period ................................................................................ 44
6.1.d)
100 Year Resting Period ............................................................................. 45
6.1.e)
Lifetime Entombment ................................................................................. 46
6.2)
Uranium-235 [235U] Waste Analysis .................................................................. 47
6.2.a)
Gaseous ....................................................................................................... 48
6.2.b)
Stable Solids................................................................................................ 49
6.2.c)
90 Day Resting Period ................................................................................ 50
6.2.d)
100 Year Resting Period ............................................................................. 51
6.2.e)
Lifetime Entombment ................................................................................. 52
6.3)
Plutonium-239 [239Pu] Waste Analysis .............................................................. 53
6.3.a)
Gaseous ....................................................................................................... 54
6.3.b)
Stable Solids................................................................................................ 55
6.3.c)
90 Day Resting Period ................................................................................ 56
6.3.d)
100 Year Resting Period ............................................................................. 57
6.3.e)
Lifetime Entombment ................................................................................. 58
6.4)
Plutonium-241 [241Pu] Waste Analysis ............................................................ 59
6.4.a)
Gaseous ....................................................................................................... 60
6.4.b)
Stable Solids................................................................................................ 61
6.4.c)
90 Day Resting Period ................................................................................ 62
v
6.4.d)
100 Year Resting Period ............................................................................. 63
6.4.e)
Lifetime Storage.......................................................................................... 64
6.5)
Summary of Sections 6.1 – 6.4 .......................................................................... 65
6.6)
Expected LFNR waste output ............................................................................ 67
6.6.a)
233
U LFNR Waste Output ........................................................................... 71
6.6.b)
235
U LFNR Waste Output ........................................................................... 73
6.6.c)
239
Pu LFNR Waste Output .......................................................................... 75
6.6.d)
241
Pu LFNR Waste Output .......................................................................... 77
6.7)
LFNR/SFNR Comparison .................................................................................. 79
7)
Discussion ................................................................................................................. 82
8)
References ................................................................................................................. 85
9)
Appendix ................................................................................................................. 100
9.1)
Terminology ..................................................................................................... 100
9.2)
Fission Product Data [By Isotope] ................................................................... 107
9.3)
Fission Product Yields [By Fissile Isotope] ..................................................... 114
9.3.a)
Uranium-233 [233U] .................................................................................. 115
9.3.b)
Uranium-235 [235U] .................................................................................. 116
9.3.c)
Plutonium-239 [239Pu]............................................................................... 117
9.3.d)
Plutonium-241 [241Pu]............................................................................... 118
vi
1.1) List of Figures
Figure 1 - Solid-Fueled Nuclear Reactor [SFNR] Operational Diagram ......................... 11
Figure 2 - Liquid-Fueled Nuclear Reactor [LFNR] Operational Diagram ....................... 14
Figure 3 - Simplified Fission Waste Breakdown Comparison ......................................... 38
Figure 4 - Uranium-233 [233U] Complete Fission Cycle .................................................. 39
Figure 5 - Side-By-Side Comparison of Fission Products ................................................ 65
Figure 6 - Color Codes for Fission Product Distribution Figures ................................... 114
Figure 7 - Uranium-233 [233U] Fission Product Distribution, by Element ..................... 115
Figure 8 - Uranium-235 [235U] Fission Product Distribution, by Element ..................... 116
Figure 9 - Plutonium-239 [239Pu] Fission Product Distribution, by Element ................. 117
Figure 10 - Plutonium-241 [241Pu] Fission Product Distribution, by Element ............... 118
vii
1.2) List of Tables
Table 1 - Fuel Isotope Fission / Absorption Ratios .......................................................... 37
Table 2 - Uranium-233 [233U] Gaseous Waste Mass ........................................................ 42
Table 3 - Uranium-233 [233U] Stable Solid Waste Mass .................................................. 43
Table 4 - Uranium-233 [233U] 90 Day Decay Waste Mass ............................................... 44
Table 5 - Uranium-233 [233U] 100 Year Decay Waste Mass............................................ 45
Table 6 - Uranium-233 [233U] Lifetime Entombment Waste Mass .................................. 46
Table 7 - Uranium-235 [235U] Gaseous Waste Mass ........................................................ 48
Table 8 - Uranium-235 [235U] Stable Solid Waste Mass .................................................. 49
Table 9 - Uranium-235 [235U] 90 Day Decay Waste Mass ............................................... 50
Table 10 - Uranium-235 [235U] 100 Year Decay Waste Mass.......................................... 51
Table 11 - Uranium-235 [235U] Lifetime Entombment Waste Mass ................................ 52
Table 12 - Plutonium-239 [239Pu] Gaseous Waste Mass .................................................. 54
Table 13 - Plutonium-239 [239Pu] Stable Solid Waste Mass ............................................ 55
Table 14 - Plutonium-239 [239Pu] 90 Day Decay Waste Mass ......................................... 56
Table 15 - Plutonium-239 [239Pu] 100 Year Decay Waste Mass ...................................... 57
Table 16 - Plutonium-239 [239Pu] Lifetime Entombment Waste Mass ............................ 58
Table 17 - Plutonium-241 [241Pu] Gaseous Waste Mass .................................................. 60
Table 18 - Plutonium-241 [241Pu] Stable Solid Waste Mass ............................................ 61
Table 19 - Plutonium-241 [241Pu] 90 Day Decay Waste Mass ......................................... 62
Table 20 - Plutonium-241 [241Pu] 100 Year Decay Waste Mass ...................................... 63
Table 21 - Plutonium-241 [241Pu] Lifetime Storage Waste Mass ..................................... 64
Table 22 - Reactor Burnup Comparisons.......................................................................... 67
viii
Table 23 - Uranium-233 [233U] Complete Full Cycle Analysis ........................................ 71
Table 24 - Uranium-233 [233U] Post-Fission Cumulative Waste...................................... 72
Table 25 - Uranium-235 [235U] Complete Full Cycle Analysis ........................................ 73
Table 26 - Uranium-235 [235U] Post-Fission Cumulative Waste...................................... 73
Table 27 - Plutonium-239 [239Pu] Complete Full Cycle Analysis .................................... 75
Table 28 - Plutonium-239 [239Pu] Post-Fission Cumulative Waste ................................ 75
Table 29 - Plutonium-241 [241Pu] Complete Full Cycle Analysis .................................... 77
Table 30 - Plutonium-241 [241Pu] Post-Fission Cumulative Waste .................................. 77
Table 31 - Fission Product Data...................................................................................... 107
ix
Acknowledgements
I gratefully acknowledge the assistance and patience s of Kathleen Saul of The
Evergreen State College. Without her patience and support I never would have completed
this thesis. Kathleen’s kooky comments throughout my drafts always helped break up the
tedious monotony of a good 12 hour writing session in the wee hours of the night.
I would also like to acknowledge the earlier work in the field by Kirk Sorenson, Gordon
McDowell, and of course Alvin Weinberg; who collectively established the framework
on which all of my work has followed.
Most importantly, I thank my wife Julie Taylor. I subjected her to countless hours
of scientific jargon over dinner and she never left me when I would disappear from “the
real world” for days on end during feverish spells of reading article after article to find
that ONE thing I couldn’t find. She is an amazing woman and without her standing
behind me, I would have never gotten this far.
And I thank my cohort, who listened to me go on and on about “why every hippy
should support nuclear power” for two years! Many of you provided me with “thought
bubbles” that would have never occurred to me otherwise, and I believe my work is better
for it.
x
2)
Introduction
It has become an irrefutable fact that the global community will not meet any
realistic carbon reduction targets without a drastic, and relatively rapid, large-scale shift
in energy production methods (Olivier, Janssens-Maenhout, Muntean, & Peters, 2013).
The recent United Nations Climate Change Conference in Paris saw leading scientists,
from around the world and across nearly all academic spectrums, come together in an
attempt to create realistic global climate change goals. It has becoming overwhelmingly
obvious that the global community will not meet the carbon reduction targets without a
drastic, and relatively rapid, large-scale shift in energy production methods. Energy
production is the single largest carbon producing industry, with some estimates showing
an annual global output in excess of 13.8 billion tons in 2012 (Olivier, JanssensMaenhout, Muntean, & Peters, 2013). This value represents 40% of the 34.5 billion tons
of carbon released globally in 2012, directly from the burning of fossil fuels. The energy
market must become an active participant in reducing carbon emissions if any hope of
slowing or halting climate change can exist (Baynes, et al., 2015).
Leading thinkers from around the world, including Bill Gates (Conca, 2015;
Zhao, Yang, Xiao, & Zhou, 2013), Elon Musk (Musk, 2007), and Taylor Wilson
(TEDtalks, 2013), have identified the Liquid-Fueled Nuclear Reactor [LFNR] as a viable
candidate for energy dense, low-waste, near-zero carbon output energy production. Bill
Gates belief in Molten Salt Reactors [MSR], a type of LFNR technology, led to his
decision to expand LFNR research in 2012, after six years of intensive research into the
Traveling Wave Reactor [TWR] (Huke, et al., 2015). Ore extraction, processing, and
waste processing account for all of the carbon output of LFNR (Herring, MacDonald,
1
Weaver, & Kullberg, 2001). LFNR operate under fundamentally different conditions
than traditional Solid Fueled Nuclear Reactors (SFNR). These differences
include, but are not limited to; more efficient fuel burnup, reduced volumes of
high-level waste, shorter lived waste, and drastically safer operating conditions
(Serp J. , et al., 2014).
While standard SFNR utilize solid uranium [U] or plutonium [Pu] ceramic pellets
as fuel, LFNR utilize a liquid solvent to dissolve the fissile/fertile isotopes to create a
“fuel salt” (Delpech, et al., 2009). Fuel salts offer numerous advantages over solid fissile
fuels, the most crucial being a far more efficient burnup ratio (Zhao, Yang, Xiao, &
Zhou, 2013). One of the most efficient SFNR ever built, the Fort Saint Vrain High
Temperature Reactor [HTR] achieved a burnup of 170 Gwd/t {~18.7%} (Carlson & Ball,
2016). A well designed LFNR style reactor, such as the proposed LFTR, has been
projected to achieve burnups as high as 881 Gwd/t {97%} (Ahmad, McClamrock, &
Glaser, 2015).
Very little has been published providing thorough analysis regarding exactly what
the composition of high-level LFNR waste would be (Ashley, 2012). As with SFNR
waste, many questions regarding the waste composition, traits, and sequestration
requirements exist. I could locate no comprehensive analysis of LFNR waste, however
many claims around the technology have been made through digital media since 2012. To
fill this gap, this thesis will provide a comprehensive long-term waste analysis of all
fission and transmutation products that created by an LFNR.
First, a brief recap of the history of LFNR technology will provide background
information about the technology. Second, a summary of current and future LFNR
2
projects will create framework to relate the urgency of further LFNR research. Third, a
brief technical introduction of LFNR technology. Fourth, the chosen model
characteristics for this thesis design. Fifth, a detailed summary, by fissile fuel type,
including waste product categorization and analysis. Finally, comparisons between
LFNR, SFNR, and traditional coal energy cycles will establish a framework in which to
differentiate the technologies.
3
3)
History of Liquid Fueled Nuclear Reactors
3.1) Pre 2000
In the earliest days of the Manhattan Project, scientists considered the idea of
using a liquid fuel substrate in nuclear reactors, but rejected the concept due to the
technological limitations of the era (Rosenthal, Kasten, & Briggs, 1970). Manufacturing
technologies at the time were limited, and Liquid Fueled Nuclear Reactors [LFNR]
requires extremely specific tolerances to ensure ongoing safe operating conditions.
Liquid fuels offer strong negative void coefficients [Appendix 9.1], and as such, can be
passively cooled even in the event of a catastrophic system failure (Schludi, 1963). The
Air Force turned to Oak Ridge National Laboratory [ORNL] to learn what liquid coolants
could meet the unique requirements of liquid fueled reactors (Sorensen, 2014). In 1952,
Ray Briant, a chemist at ORNL, had been working on a beryllium-oxide [BeO]
moderated sodium [Na]-cooled reactor with solid fuel (Grimes, 1967). Unfortunately,
with this configuration, the reactor was unable to maintain long-term operation. The solid
fuel pellets failed to handle the incredible heat stresses of the system, designed to
maintain a temperature of 1600º F (Grimes, 1967). In addition, because even the slightest
exposure to water or water vapor results in a violent thermal reaction, a Na coolant is
inherently dangerous to handle (Ashley, 2012).
Briant came up with the idea of combining a liquid salt coolant, which would act
as both a coolant and solvent, directly with the fissile fuel and the beryllium moderator
[Appendix 9.1] (Sorensen, 2014). The research team eventually realized they could likely
use the fluoride of an alkali as the solvent (Sorensen, 2014). At the time, little knowledge
4
regarding fluoride salts had yet been established (Sorensen, 2014).) Briant and his team
then converted a small research reactor and tested the viability of a fluoride-cooled core.
The ORNL team learned that the use of a liquid fuel salt created several
conditions ideal for a stable long-life nuclear reactor (Engel & Haubenreich, 1970).
Gaseous fission products that would normally cause instability within the reactor, such as
the nuclear poisons [Appendix 9.1] xenon-137 [137Xe] and krypton-90 [90Kr], could be
allowed to off-gas from the fuel mass naturally using the existing pumping action of the
reactor (Scott & Eatherly, 1970). The fuel salt could then be subjected to a series of
electro-chemical reactions that allowed for the separation of individual elements, and for
the removal of fission products and transuranic isotopes from the fuel mass (Delpech, et
al., 2009). The fuel salt could also “self-regulate” [Appendix 9.1], due to the specific
thermal expansion characteristics of the fuel (Elsheikh, 2013). This expansion reduces the
likelihood of a fission reaction while increasing the likelihood of a neutron absorption,
resulting in a core that would naturally cool itself when excessive temperatures are
reached. Fuel salts would not require the addition of control rods or burnable poisons
[Appendix 9.1], further reducing the overall waste mass (Heuer, et al., 2014). Finally,
thorium [Th], uranium [U], and plutonium [Pu] form tetrafluorides that are highly stable
and will readily dissolve in lithium-beryllium fluoride salt [FLiBe], the ideal solvent for
the high temperature environment (Nuttin, et al., 2005).
The ORNL Molten Salt Reactor Experiment [MSRE] research team, led by
Physicist Alvin Weinberg, believed the LFNR concept showed great promise (Weinberg
& Briant, 1957). The MSRE operated for nearly five years without any major incident,
demonstrating that a fluoride salt/fuel combination could work reliably (Engel &
5
Haubenreich, 1970). The MSRE showed the liquid core to be ideally suited for utilizing
fertile 232Th to generate 233U (Rosenthal, Kasten, & Briggs, 1970). The byproducts of a
LFNR, regardless of the chosen fuel type, have half-lives measured in decades and
centuries, versus millennia (Uhlíř, 2007). This distinction was not lost on the intellectuals
within the nuclear research community.
In early 1973, the Nixon administration fired Weinberg, specifically due to his
vocal advocacy of the LFNR technology and opposition to the Liquid Metal Fast-Breeder
Reactor [LMFBR] (Weinberg A. , 1994). Following Weinberg’s rather public
termination, all research into LFNR effectively became blacklisted and Weinberg’s
research team moved on to other projects (Sorensen, 2014). The Department of Energy
[DOE] and Department of Defense [DOD] cancelled funding for the MSRE project in
late 1973, in favor of the Fast Breeder Reactor research (Waltar & Reynolds, 1981). At
the time, the LMFBR design was more desirable to the DOD, as 239Pu, a weapons grade
fissile isotope, was produced by the LMFBR in relative abundance. (Bauman, et al.,
1980). In 1972 ORNL published a technical paper entitled ORNL-TM-7202 which is now
recognized as the “benchmark” for all modern LFNR advancements. This technical paper
examined the potential of using a weakly enriched 235U fuel salt, but made no attempt to
address reprocessing waste or removal of fission products (Engler, Bauman, & Dearing,
1980).
Scientists at the Kurchatov Institute in the USSR also conducted some research
into Molten Salt Reactors [MSR] in the 1970’s (Novikov, 1994). Although the Soviet
scientific team never constructed a reactor, they concluded that no physical nor
technological obstacles prevented the practical implementation of MSR for commercial
6
power generation (Novikov, 1994). The Soviets abandoned this line of research shortly
after the 1986 Chernobyl disaster in response to international outcry against nuclear
development (Novikov, 1994).
Britain’s Atomic Energy Research Establishment [AERE] conducted MSR
research between 1964 and 1973 at its National Laboratories (Martin, 2014). The AERE
chose to focus research funds on a lead-cooled MSFR concept using a chloride based salt
and plutonium (Martin, 2014). Funding for AERE’s MSR research was cut in 1974 after
the success a competing development project, the Prototype Fast Reactor [PFR] in
Dounreay, UK (Martin, 2014).
Practically no research was conducted into LFNR between 1976 and 2000
(McDowell, 2014). In 2016 Carlo Rubbia, former General Director of the European
Organization for Nuclear Research [CERN] stated his belief that the main reason
Thorium research was cut in the 1970’s is the same reason the technology is so attractive
today, LFNR do not produce fissile mass that can be used for weapons production
(Rubbia, 2016). As of 2015, the Aircraft Reactor Experiment [ARE] and MSRE are the
only molten-salt reactors to have been operated. The lack of research and lack of
operating experience has resulted in the development of significant gaps in the body of
knowledge regarding liquid fueled nuclear reactors.
7
3.2) 2000 - Future
Seaborg Technologies, based in Copenhagen, announced in March 2015 an
innovative design for a Liquid Fueled Nuclear Reactor [LFNR], “The Wasteburner” or
Seaborg Mark II, designed to operate off existing high-level nuclear waste and thorium
[Th] (Seaborg Technologies, Unknown). The company aims to use the reactor primarily
for high-level radiological waste reduction, with energy production being a side effect of
the process.
A Canadian company, Terrestrial Energy Inc., has been developing the Integral
Molten Salt Reactor (IMSR) (Terrestrial Energy, Unknown). The IMSR is being
designed as a small-scale modular reactor, ranging between 80 and 600 Mw of thermal
power. Small-scale modular reactors could be an integral part in future distributed
electrical “smart” grids, allowing high-output localized power generation. These
distributed grids would drastically reduce the need for infrastructure to distribute power
over large areas.
Research conducted by private companies from Japan, Russia, Australia, the
United States, Finland, and China have generated renewed interest in LFNR technology
in recent years (World Nuclear Association, 2016). The FUJI MSR, a 100-200 Mw
LFNR style reactor, is being developed by a consortium of Japanese, US, and Russian
scientists (Harper, 2013). The research group estimates it will take 20 years to develop a
full-size commercial reactor.
In 2011, the Chinese Academy of Sciences (CAS) announced they too had
formally begun a MSR research program (Halper, 2015). The CAS research team is
developing both an experimental liquid-fluorine fueled 2 Mw research plant and a 2 Mw
8
pebble-bed solid-thorium/MSR hybrid (Halper, 2015). The estimated completion data of
both CAS projects was delayed in 2012 until 2017 (Harper, Completion Date Slips for
China's Thorium Molten Salt Reactors, 2012).
Ratan Kumar Sinha, Chairman of the Atomic Energy Commission of India, stated
in 2013 the Bhabha Atomic Research Centre [BARC] had successfully tested several
molten salt loops [Appendix 9.1] (Jha, 2013). India has a “50-year plan” to convert all of
their primary energy infrastructure to 232Th/233U, a proposal that has resulted in
significant backlash from the nuclear community (Wong, 2015).
In the private sector, FLiBe Energy founded in 2011 to develop a commercial
Liquid Fluorine Thorium Reactor [LFTR] utilizing lithium-beryllium fluoride [FLiBe]
salts (FLiBe Energy, Unknown). FLiBe Energy is developing a 20-50 Mw LFTR for use
in powering military bases (Waldrop, 2012). Transatomic Power, a startup created by
MIT Ph.D. students Leslie Dewan and Mark Massie, with Russ Wilcox of E Ink, is
working to develop the Waste-Annihilating Molten Salt Reactor (WAMSR) (Transatomic
Power, Unknown). Like the Seaborg Mark II, the WAMSR is designed primarily as a
waste-reduction technology, with power generation being a side-effect of the process.
Transatomic Power successfully received $2.5 million in venture capital funding in 2015
to fund further development of the WAMSR (Billings, 2015).
The Alvin Weinberg Foundation, a British non-profit dedicated to Thorium
energy education and advocacy, was formally launched in the House of Lords in
September of 2011 (The Alvin Weinberg Foundation, Unknown). The Evaluation and
Viability of Liquid Fuel Fast Reactor System project [EVOL] released its final report in
2014 (Centre National De La Recherche Scientifique, 2014). EVOL examined a number
9
of European MSR concepts [FHR, MOSART, MSFR, & TMSR] and provided
assessment of how the EU MSR concepts fit into potential Generation V technology.
While the current state of LFNR can be difficult to assess, due to the very recent
and often proprietary nature of the research, it is clear that interest is growing on a global
scale, with India, China, Finland, and the United States taking the lead in recent
innovations. Citizen scientists such as Kirk Sorenson [Nasa 2000-2010; founder of FLiBe
Energy], John Kutsch [Director of Thorium Energy Alliance], Gordon McDowell
[Filmmaker], Dr. Kiki Sanford [Science Communicator; Neurophysiologist], Dr. Robert
Hargrave [Director of ThorCon Power; Physicist], Dr. Alex Cannara [Programmer;
Author], and Dr. Bogdan Maglich [Nuclear Physicist; Inventor] have been participating
in LFNR research through private and online research collectives dedicated to advancing
and advocating LFNR technology. Several TED talks over the past few years, including
those of Elon Musk (Edison Electric Institute, 2015), Bill Gates (TEDTalks, 2010), and
young prodigy Taylor Wilson (TEDtalks, 2013), have brought the idea of thorium based
LFNR reactors into mainstream scientific discussion.
10
4)
Reactor Characteristics & Chemistry
For the sake of comprehension, information on Solid Fueled Nuclear Reactors
[SFNR] has been provided to establish some framework required to understand Liquid
Fueled Nuclear Reactors [LFNR].
4.1) Solid Fueled Reactors Core Chemistry
All existing nuclear reactors use a coolant, generally water, flowing past solidfuel elements within a reactor core to transport heat generated through fission to the
steam generator. The steam then powers turbines to generate electricity [Figure 1]. Water
possesses a general low thermal capacity, a vaporization point of only 212° F, and a
vapor expansion capacity of 1700 to 1, making it a less than ideal coolant for the
extremes usually found within the core of a nuclear reactor (Perrow, 2011).
Figure 1 - Solid-Fueled Nuclear Reactor [SFNR] Operational Diagram
Solid fuel bundles are a complicated assembly of ceramic fuel pellets, protective
jackets, and physical supports (Shapiro & Fratoni, 2016). Nonporous ceramic material
encases the fuel pellets, which can contain Thorium-232 [232Th], Uranium-235 [235U],
Uranium-238 [238U], Plutonium-239 [239Pu], and/or Plutonium-241 [241Pu]. Fuel pellets
11
are designed to capture the fission products within the confines of the pellet. These
pellets are stacked inside rods wrapped in zirconium alloy cladding, completely sealed at
both ends and filled with an inert gas such as helium to improve thermal transfer between
the pellets and the cladding (Frost, 2013). The cladding serves as a second barrier to
prevent the exchange of fission products between the fissile mass and the coolant.
Assembled rods are assembled into fuel bundles, which can vary in exact size/shape
depending on reactor design.
Fuel bundles will stay in the reactor core for three to five years before being
removed for cooling and eventual sequestration. Upon removal from the reactor core, the
fuel bundles contain between 81.3-97.4% unconsumed fuel. Due to the increasing
concentration of fission products [Appendix 9.2] within the pellets, the fuel can no longer
sustain a chain reaction and therefore cannot be used to generate power efficiently. It can
take as long as 12 years for fuel bundles to cool to a temperature at which they can be
safely sequestered or reprocessed (Hippel, 2001).
12
4.2) Liquid Fueled Reactors Core Chemistry
In a Liquid-Fueled Nuclear Reactor [LFNR] the coolant, fuel, and waste are
combined in a single fluid (Delpech, et al., 2009). The compound FLiBe, a mixture of
lithium fluoride [LiF] and beryllium fluoride [BeF2], has been identified as a viable
solvent for this application (Ingersoll, 2005). FLiBe has a melting point of 858° F and a
boiling point of 2606° F, allowing the salt to remain a stable liquid at atmospheric
pressure (Ingersoll, 2005). It has heat capacity and flow characteristics similar to those of
water, allowing existing pump technology to efficiently cycle the fuel mass through the
reactor components.
LFNR can utilize 232Th, 235U, 238U, 239Pu, and/or 241Pu as fuel (Nuttin, et al.,
2005). Most current research into the technology focus on the 232Th/233U fuel cycle, as the
233
U fission cycle results in the creation of very few transuranic isotopes and practically
no proliferation-ready isotopes [Appendix 9.3]. A 233U LFNR would require an initial
input of around 1-part fissile fuel to 2-parts fertile fuel (Bauman, et al., 1980). The fissile
mass, likely, 235U is used to initiate the chain reaction, while the fertile mass, likely 232Th,
would steadily be converted to 233Th through transmutation (Delpech, et al., 2009). 233Th,
with a half-life of only 22 minutes, decays into protactinium-233 [233Pa] through beta
decay [Appendix 9.1] (Brown, Dixon, & Rogers, 1968). The 233Pa, with a half-life of 27
days, will decay to 233U through beta decay. The 233U, a fissile element, eventually
replaces the 235U within the initial fuel mass and the reactor becomes self-sustaining,
requiring only periodic addition of fertile fuel (Bauman, et al., 1980). Excess 233U can be
removed from the reactor and used to initiate other LFNR.
13
In a single-fluid LFNR, the singular fuel mass would contain the coolant,
moderator, fissile fuel, fertile fuel, and fission products. This concept, though
technologically easier than a dual-fluid reactor, presents significant long-term challenges.
Many of the lanthanide fission products are difficult to chemically separate from
Thorium, because of the similarity of their chemical properties (Bauman, et al., 1980).
Figure 2 - Liquid-Fueled Nuclear Reactor [LFNR] Operational Diagram
In a dual-fuel LFNR [Figure 2], the core consists of an inner core chamber
containing the fissile mass surrounded by an outer core chamber, called the “fertile
blanket” (Huke, Armin, et al., 2014). Operators inject 232Th into the outer blanket where
it will absorb a neutron to become 233Pa. The 233Pa, now chemically distinct from the
fertile 232Th, can be removed from the fertile mass through electrochemical precipitation
and allowed to “rest” for around 90 days (Huke, et al., 2015). This resting period allows
the 233Pa to fully decay to 233U, which can then be removed as uranium hexafluoride
[UF6] through fluorination. The UF6 is then reduced uranium tetrafluoride [UF4], which
can be injected into the inner core. Keeping the fission products in the fissile core entirely
separate from the outer fertile core drastically increases the long-term efficiency of the
reactor (Huke, Armin, et al., 2014).
14
Regardless of the LFNR design used, the fuel salt runs through a continuous
series of electrochemical precipitation reactions while the reactor operates (Delpech, et
al., 2009). The continuous removal of individual fission products and reintroduction of
unconsumed fissile isotopes ensures the reactor operates at very near 97% burnup
(Nuttin, et al., 2005). This process also allows for potentially valuable isotopes, such as
those used for advanced scientific research or medical treatments, to be removed and
utilized (Chuvilin & Zagryadskii, 2009). For example, a number of the fission products
represent significant value for advanced cancer treatments, specifically Bismuth-213
[213Bi] and Technetium-99m [99mTc] (Knapp, 2012).
In a sense, a well-designed LFNR could be likened more to a factory than a power
plant. Electricity production would be just on, of many, products created. Many of the
fission products are exceptionally valuable for a wide variety of applications in
manufacturing, medical treatments, advanced research, and space travel. The ability to
create non-weaponizable 238Pu, currently the most expensive isotope (per gram) on the
planet is of extreme interest to any organization that wishes to send any probe or
spacecraft beyond the orbit of Mars (Ahmed, McClamrock, & Glaser, 2015). However,
individual elements have different handling and storage requirements, and safe operation
of the facility would require meeting all of these individual requirements. LFNR plants
would likely employ as many chemists and machinists as they would nuclear engineers.
Understanding the full impact of any reactor is incredibly complex. One must
consider not only the characteristics of the mass upon removal from the reactor, but a
series of decay reactions that will continue to alter the overall waste mass for millennia.
15
To attempt to create equitable points of comparison, the following model has been
created to facilitate examination.
16
5)
Model
To create models that can be compared easily, nearly every isotope present within
the waste mass must be examined both individually and as a collective mass. While some
fission products are incredible stable, others are violently reactive, explosive, radioactive,
highly toxic, and/or pyrophoric. Many are stable under most conditions, but the extreme
temperatures utilized by a reactor can allow for seemingly unpredictable behaviors. The
following model attempts to combine any and all characteristics that may affect the final
waste mass whenever possible. The final analysis, following this section, was generated
from the collective data to help the reader understand the incredibly complicated
interactions occurring and the complex chemistry of the final waste. Individual variables
and rationale are described as necessary.
17
5.1) Chosen Variables
Element and Isotopic Information collected from CRC Handbook of Chemistry
and Physics, 96th Edition (Haynes, 2015). Includes:
Atomic Number – The number of protons within the atomic nuclei of any
element.
Element Symbol – As accepted by International Union of Pure and Applied
Chemistry [IUPAC]
Common Name – As accepted by IUPAC.
Isotope – Number of protons and neutrons within the atomic nuclei of any
element. Most elements have multiple isotopes.
Physical State (Gas or Liquid) – For pure elemental state only.
Demand was determined by a thorough search of peer reviewed papers to
identify potentially valuable products. Rated as: No, Sometimes, Yes. All
isotopes identified as “Sometimes” or “Yes” will be cited as needed.
Individual isotopic traits were collected from multiple sources. Unless otherwise
marked, the information was collected from the CRC Handbook of Chemistry and
Physics (Haynes, 2015).
Ratings for the following statistics are: No (no risk) | Sometimes (conditional risk)
| Yes (high risk). Includes ratings for each isotope:
Reactivity – How likely is the isotope to react violently with other elements?
Explosiveness – Does the isotope present an explosion hazard under
conditions that could exist in a LFNR operation?
18
Pyrophoricity [Appendix 9.1] – How likely is the isotope to have a
pyrophoric reaction?
Biological Danger – Is the isotope toxic or does it represent a specific, nonradiation based hazard to living organisms?
Radioactivity was determined based upon the half-lives of the individual
isotope. When possible, radioactivity data was confirmed through peerreviewed sources, and will be cited as such. All elements whose half-lives are
below 345 billion years [3.45E+11] are marked as “radioactive”. 345 billion
years was chosen as it is 31 times the length of the known universe. 31 halflives will result in the decay of 99.999999999% of the original mass, leaving
less than one billionth of a percent of the original isotope. Any element with a
half-life in excess of [3.45E+11] are marked as “observational stable”, as little
to no decay will occur during any time frame relevant to living organisms.
Fissile and Fissionable were recorded as “yes” or “no”. In most cases, this
data was recorded from the CRC Handbook of Chemistry and Physics, 96th
Edition (Haynes, 2015). In cases where the CRC handbook did not provide
data, specific citations will be noted.
All isotopes are rated by Proliferation Threat based on whether or not the
isotope can be used to make a nuclear weapon. In all cases, this was determined through
peer reviewed sources, which will be noted when applicable.
All Half Life, Daughter Elements, and Decay Modes were recorded from the
International Atomic Energy Agency [IAEA] Nuclear Data Services (IAEA). IAEA half-
19
life data was chosen based on data consistency, frequency of citation in peer reviewed
articles, and completeness of data set. Types of Decay are listed as:
α
Alpha Decay
β−
Beta Decay
CD
Cluster Decay
SF
Spontaneous Fission
β−β−
IT
Isomeric Transitions
EC
Electron Capture
Double Beta Decay
Likelihood of Creation (of daughter elements) is provided when possible,
specific citations will be provided when necessary.
Time to 99.999999999% Decay was calculated by multiplying half-life by 31.
“N/A” is used to signify stable elements.
Long term decay yields were calculated using the following values:
30 Days =
8.22E-2
90 Days =
2.47E-1
180 Days =
4.93E-1
1 Year =
1E+0
2 Years =
2E+0
3 Years =
3E+0
5 Years =
5E+0
10 Years =
1E+1
20 Years =
2E+1
30 Years =
3E+1
50 Years =
5E+1
100 Years =
1E+2
500 Years =
5E+2
1,000 Years =
1E+3
5,000 Years =
5E+3
10,000 Years =
1E+4
20
The fissile isotopes 233U, 235U, 239Pu, and 241Pu were chosen for analysis. These
isotopes were chosen based on their ability to sustain a viable chain reaction. Expected
fission and transmutation products were grouped into 5 categories based on safe
sequestration time periods, as determined by half-life.
The fission waste categories are:
Gaseous Products – All isotopes that can be removed from fuel salts through
passive outgassing.
Stable Solids – All stable isotopes, where no radioactive sister isotopes are
present (Elements where multiple isotopes can be present and are chemically
identical).
90 Day Rest Period – All isotopes that will fully decay ~31(t1⁄2) in less than
90 days after removal from the fuel mass.
100 Year Rest Period – All isotopes that will require a 100-year
sequestration period to fully decay ~31(t1⁄2)
Lifetime Entombment – All isotopes that will require more than 100-year
sequestration. 100 years was chosen as the cutoff for this category as the
timeframe represents a length of time beyond any currently identified
sequestration technology. As such, all products with exceptionally long halflives and the transuranic isotopes will essentially require permanent
entombment.
Fuel Mass Transmuted – The expected percentage of transmutation during
fission cycle. Fission/Absorption ratios were recorded from the IAEA Nuclear
21
Data Services and confirmed through peer reviewed articles (Lammer &
Nichols, 2008).
For purposes of clarity within this document, “Transmuted” will be used to
define “nuclear transmutation through neutron absorption”.
Isotopes created specifically after undergoing fission will be defined as “Fission
Products”.
Isotopes created through nuclear decay will be defined as “Decay Products”.
22
5.2) Assumptions Made
The following assumptions underlie the model presented for this thesis:
In any case where an element exists within expected fission yields where an
isotope of that element is radioactive, all sister isotopes are grouped under the
classification of the most dangerous isotope within the set. Because isotopes of the same
element possess nearly identical chemical, electrical, and physical properties, any
attempted isotopic separation would be expensive, inefficient, and likely would not result
in total removal of the dangerous isotopes. In these cases, explanation of potential
separation procedures will be given only if any isotope is classified as “in demand”.
Generally, this would be due to an isotope being used in research, spaceflight, or medical
applications. Otherwise, the assumption that the element will require sequestration until
full decay ~31(t1⁄2) has occurred.
In cases where an isotopes full decay period exceeds 345 billion years, the isotope
is considered “observationally stable”. Though a nearly immeasurable amount of decay
will occur during the life of the isotope, the volume would be so minimal as to represent
no risk, other than those posed by the chemical traits of the isotope.
In cases where a decay chain may result in an isotope that may transition between
solid and gaseous state, or vice-versa, specific gas storage criteria and sequestration
durations will be provided.
The generally accepted standard “safe decay time” within the nuclear research
community is 25(t1/2), which will result in the decay of all but one hundred-millionth of a
percent of the initial isotope. For this analysis, 31(t1/2) was chosen, since this represents
decay down to one billionth of a percent. Because many of the shorter lived fission
23
products that require under ninety days to decay to a stable isotope, it seems reasonable to
simply increase holding time by several weeks to ensure a far more complete decay. In
addition, since many of the fission products may have commercial value, there is no
reason to risk accidental introduction of potentially damaging radiation into the final
saleable product. For all analysis in this thesis, the assumed “safe” decay state of all
elements will be 31(t1/2).
Finally, in all cases for which conflicting data was found during the review of
peer reviewed work, the “most dangerous” assumption was always assumed to be true,
unless the stated fact is called into question by any subsequent work. This will provide
the “worst case scenario” calculation in all cases. While in some cases literature has
reported conflicting data, because of the extreme hazard to living organisms presented by
radioactive waste, this thesis will always lean towards the “Safest” possible
recommendation. In all cases where the possibility of a hazardous event occurring
(reaction, explosion, fire hazard, toxicity, and criticality risk [See Appendix 9.1]) exceeds
0.00001%, the risk is considered “yes”. The exception to this assumption occurs when
any isotope was identified to possess a given trait only when in a physical state that
would not be seen in a LFNR system or subsequent sequestration / use. In such cases, the
trait will be marked “no”.
24
5.3) Other Considerations
This analysis conducted for this thesis does not examine transuranic isotopes
heavier than 241Pu. The potential creation of these elements is acknowledged as
“transmuted isotopes”. This decision was made based on three facts:
First, because the liquid nature of the fuel salt allows for continuous removal of
individual isotopes through electro chemical precipitation, it is very likely that reactors
will be designed to extract nearly all 238Pu produced through transmutation. 238Pu is
absolutely critical in radioisotopic generators, currently the only viable method of
producing power beyond the orbit of Mars, to any human exploration beyond the orbit of
Mars [where solar panels can no longer produce enough power] (Hamley, 2016). This
trait alone makes 238Pu the most valuable isotope on planet Earth, with an estimated value
of $8 million per kilogram (Harvey, 2015). Therefore, very little if any of the fuel mass
would likely be allowed to reach a heavier isotopic weight than 238Pu.
Second, several transuranic isotopes created through transmutation are critical for
modern devices. For example, all modern ionizing-type smoke detectors and in advanced
nuclear batteries incorporate americium-241 [241Am] in very small amounts (Navratil,
Schulz, & Seaborg, 1990). Californium-252 [252Cf] is used as a neutron source for
initiating nuclear reactors as well as for neutron radiography, which is used to verify the
strength of welds and check corrosion levels of metal surfaces (Martin, Knauer, & Balo,
2000). These applications ensure that with proper design, the few transuranic isotopes
that would be created would be removed from the fissile mass and used almost
immediately.
25
Third, LFNR style reactors allow for a near total burnup of all transuranic
isotopes (which are always fissile/fissionable) (Zhao, Yang, Xiao, & Zhou, 2013). Since
overall production of these isotopes would be very low in LFNR systems, any unusable
transuranic isotopes created through transmutation could be reinjected into the fissile core
for subsequent burnup.
26
5.4) Considerations
Determining the final compound in which the various isotopes will be extracted
and chemically stabilized for use or sequestration is critical. Many of the isotopes created
can exist in many compounds, and in the form of gases, liquids, and solids. These final
compounds depend on the specific chemistry of each series of reactions, and could vary
considerably between individual reactor facilities. This is due to the wide variety of
precipitation, catalytic, reduction, and oxidation reactions that could be used to extract
individual elements or isotopes. Different facilities may choose differing extraction
agents, and as such could alter the final form from perhaps an oxide to a fluoride. Both
are chemically stable, but occur due to different electro-chemical processes being utilized
by the individual facility.
That said, in most cases the chosen reactions would likely be based primarily on
the market cost of the reagents and as such a “most likely choice” can often be assumed.
Most isotopes will require some stabilizing prior to market usage, sequestration, or
lifetime entombment (Nagasaki & Nakayama, 2015). Depending on the isotope, the
actual compound chosen may vary, but it will ideally be a stable compound which is
highly resistant to corrosion (Nagasaki & Nakayama, 2015). Some fission products, such
as oxygen [O], fluorine [F], carbon [C], iodine [I], and sodium [Na] are highly reactive,
and will form compounds very quickly after creation (Kleykamp, 1988). For example, it
is unlikely that any fluorine gas created, in the reactor or through nuclear decay, would
ever be found as free fluorine (Gouverneur & Seppelt, 2015). When possible, any
assumptions as to the “likely” process or outcome will be provided, along with necessary
27
supporting data. It should be noted that this aspect of the analysis is by no means 100%
accurate, and has been provided only to create a frame of reference.
For any isotopes in which the ~31(t1⁄2) is equal to or below one hour [1.14E-04],
the isotope will be treated as “non-existent” in this analysis. These isotopes would never
be seen outside of the fuel salt, as they would completely decay before any physical
samples could be collected and processed. In these cases, the longer lived daughter
products will be acknowledged. Effort has been made to recognize very short-lived, and
therefore highly radioactive, products that will be created during sequestration. For many
of these very-short lived isotopes, no amount sufficient for analysis has likely ever been
created in any usable capacity, and, as such, some gaps in the scientific body of
knowledge can exist.
Any fission products created through spontaneous fission are identified by
“Various”. These fission products can be comprised of any binary or ternary set of
isotopes and will follow the same distribution normally exhibited from fission.
Spontaneous fission has been effectively ignored for this analysis, as all isotopes capable
of spontaneous fission would be returned to the fissile core for burnup.
The “estimated 100% burnup” of 909 Mwd/t was determined by averaging the
energy densities of 233U, 235U, 239Pu, and 241Pu. Actual energy density of individual fuel
masses would fluctuate somewhat depending on specific fuel composition and fissile
isotopes chosen.
What follows is a summary of the collective data assembled for the above
computer model. The Findings section will first explain the primary categories under
which all fission products are grouped for this thesis. Next, each fissile fuel type will be
28
examined individually, to provide the necessary framework for understanding the final
section. Third, each complete fuel cycle will be examined in full (accounting for all
transmutation chains). Finally, a comparison waste analysis of LFNR, SFNR, and
traditional coal will show directly how LFNR compares to existing dominant energy
technologies.
29
6)
Findings
After completing the data collection phase, the computer model showed that all
fission products could be grouped into six categories. These categories were chosen
based on isotopic composition, chemical characteristics, and account for all decay chains
that will occur within the waste. Therefore, all products within each category will not be
subject to potentially dangerous interactions with other products within the category.
After all fission and decay products were categorized, the following categories
were chosen for extended explanation based on relevance:
NOTE: Specific isotopic composition will be given in the following section.
Gaseous Products – This category includes all gaseous products created through
the fission process. Gaseous fission products will exit the fuel mass naturally through
natural off-gassing, and can be collected immediately for a cool-down storage period.
The exact mechanism for the removal of gaseous products could vary based on individual
Liquid-Fueled Nuclear Reactor [LFNR] design, however it would operate in a similar
fashion to existing Solid-Fueled Nuclear Reactor [SFNR] gas removal systems. This cool
down period also allows for the very small volume of radioactive decay products created
to be safely removed.
While the gaseous fission products are generally stable, a portion of the mass will
be 135Xe, which will undergo 31(t1/2) to 135Cs in approximately 12 days (Allan & Nuttall,
1997). Caesium is highly toxic, pyrophoric, reactive, and radioactive, and as such must be
added to in the lifetime entombment mass. Following a 30-day resting period, the
remaining mass of Xe and Kr can be sold for industrial manufacturing, as both are in high
demand (Herman & Unfried, 2015).
30
Stable Solids – This category includes all solid-isotopes that:
1. Are not, and will not ever decay into, a gaseous product,
2. Are chemically different from all isotopes present in the fuel/waste mass that
are radioactive, or
3. Are not in any way radioactive, and will not require any sequestration period
to become stable.
Companies involved in advanced electronics manufacturing and other specialized
industries have created a high demand for all stable isotopes created through fission.
Though often very little of an individual isotope is created through fission, to eliminate
waste these isotopes should be removed in their elemental form or converted to a stable
oxide for subsequent distribution.
All isotopes in the stable solids category are chemically distinct from any
radioactive isotopes within the waste mass, and as such can be removed through specific
series of electrochemical reactions, eliminating the need for excessive reprocessing or
cleaning. Most of the stable solids are mildly toxic, but no serious storage hazards exist.
It should be noted that 113Cd and 115In are technically radioactive, but are considered
observational stable because their half-lives exceed the age of the known universe. As
such, the decay that will occur is so slowly it will have no bearing on any foreseeable
human civilization.
90 Day Rest Period – This category accounts for ~15% of the total waste mass
from the fission process. These isotopes are highly radioactive, with relatively short halflives, and, as such, require very careful handling and storage. This category includes all
solid-isotopes that
31
1. Are radioactive,
2. Are solid,
3. Will undergo 31(t1/2) in less than 90 days, from the point of removal from the
fuel mass, and/or
4. Are chemically identical to any isotope that meets conditions a, b, and/or c.
While not all of the rhodium [Rh] and iodine [I] isotopes produced are
radioactive, the majority [~90%] are highly radioactive. The short half-lived 105Rh
(Pierson, 1965), 127Te (Day, Eakins, & Voigt, 1955), and 135I give off significant
quantities of Beta particles and associated energies during decay.
The most dangerous isotope in this category, by far, is 135I. 135I is very prone to
biological uptake, where it takes residence within the bones and cartilage of the organism
(Bustad, 2013). The subsequent beta decay will cause tremendous damage to surrounding
living tissues. 135I is one of the isotopes of most concern in the case of an accidental
discharge of high-level waste into the environment. In addition, 135I will decay into 135Xe
[a gas], which will further decay to 135Cs, a very long-lived radioactive solid. This phase
transition from solid gas solid makes 135I particularly difficult to store safely.
With approximately 80% of this mass undergoing the decay-phase transition process
[Solid Gas Solid], sequestration of the waste mass requires very specific
engineering. The solid mass must rest for at least nine days in a liquid suspension to
allow the 135I to decay to 135Xe. Upon its creation, the 135Xe will be removed through
natural off-gassing and collected. The 135Xe must rest an additional 12 days to undergo
31a(t1/2) to decay to 135Cs. The 135Cs must then be added to the lifetime entombment
waste mass, and the remaining products can be sold for manufacturing.
32
After a decay period of 90 days, the remaining mass from this category will be
comprised of stable palladium-105 [105Pd] and 127I a. Both of these isotopes are currently
in demand in the global marketplace and represent no significant hazards to humans.
100 Year Rest Period – This category was selected based on the volume of
material that degrades within the timeframe and the general half-lives of the isotopes
within the mass. Though some isotopes decay much sooner, the actual portion of those
isotopes to the total mass is very low. The average safe-decay time of this mass is ~72
years. While not as radioactive as isotopes in the “90 days” category, these isotopes are
still very dangerous to living organisms. This category includes all solid-isotopes that
1. Are radioactive,
2. Are solid,
3. Will undergo 31 half-lives in between 90 days and 100 years,
4. Are chemically identical to any isotope that meets conditions a, b, and/or c.
All isotopes of promethium [Pm] are highly unstable, and will undergo 31(t1/2)
within 81.5 years.
In fact, all Pm will decay in less than 5 years, with the exception of 147Pm.
However, because the isotopes are chemically identical, effective separation of these
isotopes can be done only after they have undergone decay. All Pm will decay to
Samarium [Sm], and some of that will eventually decay to Neodymium [Nd]. Because
Pm, Sm, and Nd are very chemically similar, early elemental separation of the isotopes in
this mass is unfeasible. All Sm isotopes can be considered effectively stable, owing to
their extremely long half-lives. Both Sm and Nd are in high demand for industrial
manufacturing.
33
The antimony-125 [125Sb] present within the waste mass has a similar decay
period to 147Pm, requiring just shy of 85 years to undergo ~31(t1⁄2). 125Sb will decay to the
metastable element tellurium-125m [125mTe). All 125mTe will undergo isomeric transition
within three years, decaying to stable 125Te. Te is in strong demand for a variety of
industrial manufacturing processes, ranging from advanced electronic components to
vulcanization of rubber for tires (Royal Society of Chemistry, Unknown).
Stable ruthenium-101 [101Ru] comprises nearly two thirds of the Ru mass. The
remainder is highly radioactive 103Ru and 106Ru, which require 32 years to undergo
~31(t1⁄2). 103Ru will decay to stable rhodium-105 [105Rh], a highly sought after element
used in anti-corrosion metal coatings (Royal Society of Chemistry, Unknown). 106Ru will
decay to the unstable 106Rh, which will rapidly decay to stable palladium-106 [106Pd].
A 100 year resting period is assumed to ensure that absolutely no radioactive isotopes or
dangerous decay products are released. After safe decay, this entire mass is safe for use in
industrial manufacturing.
No gaseous products are produced through decay of this portion of the waste
mass.
Lifetime Entombment – This category was selected based on the general halflives of the isotopes within the mass. For all intents and purposes, isotopes in this
category will require storage for a timespan longer than the entirety of human existence
to date. As such, it has been assumed that waste requiring more than 100 years will
effectively require indefinite entombment. Many other nuclear waste analyses, including
those used to define current “safe storage standards” for high-level waste, will often
divide waste into categories of 500, 1000, 2500, 5000, and 10000 years as well. Given the
34
extreme risk presented by the waste, and the extreme instability of human society in
general, this thesis assumes the safest option in these cases will be permanent
entombment for all products requiring longer than 100 years to safely decay. This
category includes all solid-isotopes that:
1. Are radioactive,
2. Are solid,
3. Will not undergo 31 half-lives in under 100 years,
4. Are chemically identical to any isotope that meets conditions a, b, and/or c.
While caesium-133 [133Cs] is stable, all other isotopes of Cs are not (D'auria, et
al., 1978). The very small portion of 234Cs will decay into stable gaseous 234Xenon, which
can be vented safely and presents no risks (Alexander, Bennett, Srinivasan, & Manuel,
1968). The remaining mass will eventually decay to stable isotopes of bismuth [Bi], but
this will require 935 years. In addition, radioactive caesium will emit gamma rays during
decay, requiring strong radiation shielding to prevent risk to living organisms (Ghys,
1960). The ability to emit gamma rays also creates some demand for radioactive caesium
for use in irradiating food, as a gamma source neutron spectroscopy, and as a gamma
source for some forms of cancer treatment (Bick & Prinz, 2000). Caesium is also highly
reactive, pyrophoric, and very toxic to living organisms and must be stored with care.
The technetium -99 [99Tc] within the waste mass is one of the most difficult
fission products to deal with (Ojovan & Lee, 2013). Technetium can form anionic
compounds easily, making it highly mobile when released into the environment
(Dickson, Harsh, Lukens, & Pierce, 2015). Anions are all considered bases as they can
accept a H+, making them very reactive and likely to form compounds in aqueous
35
solutions (Sheppard & Thibault, 1990). Most isotopic separation processes utilize the fact
that cations are easier to remove through electrochemical processes. Often anionic
pertechnetate, the form in which Tc exists during extraction, will be totally unaffected by
electrochemical processes (Dickson, Harsh, Lukens, & Pierce, 2015). Tc therefore
represents a significant challenge for high-level waste sequestration. The extremely long
half-life, penchant for releasing X-rays when decaying, and extreme mobility in the
environment, make Tc the prime source for most radiative release from the waste mass
after 1000 years (Cohen, 1977).
99
Tc is a viable candidate for disposal through transmutation (Tommasi, Delpech,
Grouiller, & Zaetta, 1995). By exposing 99Tc to high energy neutrons, such as those
produced from a nuclear chain reaction, highly unstable 100Tc can be created through
transmutation of 99Tc. 100Tc, with a 31(t1/2) of 8.27 minutes, will rapidly decay to stable
ruthenium-100 [100Ru]. This method of disposal is generally inefficient, given the energy
required to generate free neutrons and because the 99Tc must first be extracted from highlevel waste, a process currently illegal in many countries (Tommasi, Delpech, Grouiller,
& Zaetta, 1995). On the other hand, the use of transmutation for 99Tc disposal would
reduce the volume of waste requiring lifetime entombment by 26.5%.
All samarium [Sm] isotopes within the waste mass must be permanently
entombed, although only 151Sm is radioactive. Because all Sm isotopes possess identical
chemical traits, efficient removal of all 151Sm cannot be ensured. All 151Sm will undergo
31(t1/2) within 2750 years, decaying to europium-151 [151Eu]. 151Eu, while technically
radioactive, can be considered “effectively stable”, owing to its half-life exceeding the
36
age of the known universe. 151Eu created by decay cannot be effectively removed, owing
to the presence of other radioactive isotopes of Eu within the waste mass.
Like samarium [Sm], all palladium [Pd] isotopes in the waste mass must be
permanently entombed due to the presence of 107Pd. 107Pd will undergo 31(t1/2) in
approximately 2 billion years, decaying to stable Silver-107 [107Ag].
Isotopes of europium [Eu] possess the widest variety of half-lives among all
fission products. The most radioactive isotope, 155Eu will undergo 31(t1/2) in 148 years,
decaying to stable gadolinium-155 [155Gd]. 154Eu will undergo 31(t1/2) in 267 years,
decaying through beta decay primarily to stable 154Gd. A minute portion [0.02%] will
undergo electron capture and decay to stable samarium-154 [154Sm]. 153Eu is stable. 152Eu
will undergo 31(t1/2) in 420 years, decaying to stable 152Sm [72.36%] or “effectively
stable” 152Gd [27.64%] through electron capture and beta decay. 151Eu, the longest lived
unstable isotope of Eu, can be considered effectively stable with a 31(t1/2) of 143
quintillion years.
Table 1 - Fuel Isotope Fission / Absorption Ratios
Fuel
233U
235U
239Pu
241Pu
Thermal Cross-Section
(in Barns)
587 ± 3 *
693 ± 5 *
1007 ± 8 ǂ
1373 ± 11 Θ
* = (Block, Harvey, & Slaughter, 1960)
ǂ = (Safford & Havens, 1961)
Θ = (IAEA, n.d.)
Likelihood of
Fission
Absorption
~ 66.14% ~ 33.86%
~ 72.76% ~ 27.24%
~ 93.62%
~ 6.38%
~ 98.88%
~ 1.12%
Transmuted Mass – This
category covers the portion of the
fissile mass that will be transmuted
[Appendix 9.1] into heavier elements
or isotopes. LFNR’s would allow for all heavier isotopes to be reinserted into the fissile
core for further transmutation or burnup. All transmuted isotopes heavier than thorium232 [232Th], that are not in demand for a specific purpose [such as americium and
californium], would be returned to the inner core for eventual burnup.
37
The likelihood of a fission event occurring upon a neutron collision, as opposed to
a neutron absorption resulting in transmutation, increases with isotopic weight [Table 1].
Note that the general availability and volume of pre-fission waste increases
exponentially with isotopic weight. Thorianite, the most efficient source of 232Th, the
precursor to 233U, yields an average of 12% Th by weight, resulting in ~8.3 tons of prefission waste per ton of usable Th (Dunstan & Blake, 1905). The highest uranium bearing
ore on Earth, from the Cigar Lake deposit in
the Athabasca Basin of Canada, yields 18%
raw uranium (Fayek, Janeczek, & Ewing,
1997). 235U only represents 0.72% of the
natural uranium, with the remainder
comprised of undesirable 238U. To extract a
ton of 235U will result in ~1,389 tons of prefission waste per ton.
Plutonium-239 [239Pu] is much rarer
than uranium in nature, as 239Pu will only
exist in miniscule trace amounts naturally on
Earth. The process of creating Pu is highly
inefficient. Consider that to create Pu, 238U
must undergo transmutation by being
irradiated with high-energy neutrons. Due to
the sheer amount of energy required, this
Figure 3 - Simplified Fission Waste Breakdown
Comparison
usually occurs inside a nuclear reactor. From
38
most reactor grade fuels containing around 20% 235U, an average yield of around one
gram 239Pu will be produced for every 1 Megawatt day of power generated (Edlund,
1975). To produce one ton of 239Pu would requires nearly 1 Terawatt days of power,
requiring the fission of ~24.5 tons of fuel. In all, one ton of Pu would produce ~34,000
tons of mining/processing waste, to speak nothing of the highly irradiated fission waste
generated in the process.
As a transmutation product of 239Pu, 241Pu is even more rare. With an average
absorption rate of only ~6.38%, one ton of 241Pu would produce over 530,000 tons of
mining/processing waste and over 15 times the volume of highly irradiated fission waste
generated by 239Pu.
Figure 3 shows the general disposition of
high-level waste generated within the reactor.
It should be noted that Figure 3 shows the
general types of waste generated for the fission
of each specific fissile isotope. To correctly
calculate the composition of a given fuel mass,
Figure 4 - Uranium-233 [233U] Complete Fission
Cycle
the fission products of all portions of the
fission process must be combined. For
example, [Figure 4], 233U fission products account for 66.14% of the total waste mass,
72.76% of the remaining 33.86% [after 233U cycle] of transmuted mass will undergo
fission as 235U, 93.62% of that transmuted mass will undergo fission as 239Pu, and so on.
It therefore stands to reason that in an “ideal world”, nuclear fission should be conducted
with the lightest fissile isotope possible to avoid excessive production of transuranic
39
isotopes. With heavier isotopes, such as 241Pu, yields of transuranic and radioactive
isotopes in the final waste mass will be significantly higher.
Since the transuranic waste isotopes are all highly radioactive, frequently
pyrophoric, toxic, and will eventually lead to the creation of new highly-radioactive
decay products, minimizing production of transuranic isotopes is critical to ensure the
long-term environmental safety of a reactor design.
Based on the categories defined above, the following analysis will examine the
specific chemistry of each fissile isotope.
40
6.1) Uranium-233 [233U] Waste Analysis
Of the four viable fissile fuel types shown in Figure 3 above, the 233U fission
cycle produces the lowest volume of long-lived radioactive waste. Note that this section
only refers to fission products produced directly by 233U fission, and does not include
fission products created through subsequent fission of transmuted isotopes. Refer to
section 6.5 for complete Liquid-Fueled Nuclear Reactor [LFNR] fuel cycle analysis.
41
6.1.a)
Gaseous
Table 2 - Uranium-233 [233U] Gaseous Waste Mass
% of
Mass
Isotope
Common
Name
Symbol
Atomic
Number
The gaseous products created through
36
Kr
Krypton
83
5.39
54
Xe
Xenon
131
19.16
134
33.49%
135
6.52%
136
35.44%
the 233U fission cycle represent a total of
18.81% of the waste mass. The waste mass can
be reduced immediately by the natural offgassing of Kr and Xe.
42
6.1.b)
Stable Solids
Table 3 - Uranium-233 [233U] Stable Solid Waste Mass
Atomic
Number
Symbol
Common
Name
Isotope
% of
Mass
The stable solid fission products created
through the 233U fission cycle represent a total
42
Mo
Molybdenum
95
40.11%
47
Ag
Silver
109
0.25%
of 15.87% of the waste mass. The primary
48
Cd
Cadmium
113
0.08%
49
In
Indium
115
0.09%
60
Nd
Neodymium
143
145
37.61%
21.72%
154
155
156
157
158
>0.00%
>0.00%
0.08%
0.04%
0.01%
160
161
162
163
164
>0.00%
>0.00%
>0.00%
>0.00%
>0.00%
64
66
Gd
Dy
Gadolinium
Dysprosium
67
Ho
Holmium
165
>0.00%
68
Er
Erbium
166
167
>0.00%
>0.00%
isotopes within the stable solid mass are 95Mo,
143
Nd, and 145Nd, comprising 99.4% of the
total.
The remaining 0.6% of the stable solids is a
mixture of Ag, Cd, In, Gd, Dy, Ho, and Er.
43
6.1.c)
90 Day Resting Period
Table 4 - Uranium-233 [233U] 90 Day Decay Waste Mass
Atomic
Number
Symbol
Isotope
% of
Mass
Common
Name
The fission products created through the
233
45
Rh
Rhodium
103
105
>0.00%
8.19%
under 90 days represent a total of 6.08% of the
52
Te
Tellurium
127
1.60%
53
I
Iodine
127
135
7.54%
82.67%
U fission cycle which will undergo 31(t1/2) in
waste mass. The primary isotopes within this
mass are 105Rh, 127I, and 135I, comprising 98.4%
of the total.
44
6.1.d)
100 Year Resting Period
Table 5 - Uranium-233 [233U] 100 Year Decay Waste Mass
Ruthenium
% of
Mass
Ru
Isotope
Symbol
44
Common
Name
Atomic
Number
The fission products created through
101
46.60%
103
23.11%
106
3.62%
51
Sb
Antimony
125
1.72%
61
Pm
Promethium
147
13.53%
148
>0.00%
148m
>0.00%
149
11.43%
the 233U fission cycle which will undergo
31(t1/2), between 90 days and 100 years
represent a total of 6.81% of the waste mass.
The primary isotopes within this mass are
those of Ru and Pm, comprising 98.3% of the
total.
45
6.1.e)
Lifetime Entombment
Table 6 - Uranium-233 [233U] Lifetime Entombment Waste Mass
55
62
63
Cs
Sm
Eu
% of
Mass
Tc
Pd
Isotope
Symbol
43
46
Common
Name
Atomic
Number
The fission products created through
Technetium
99
26.53%
Palladium
105
>0.00%
107
0.62%
108
0.41%
Caesium
Samarium
Europium
133
32.06%
134
>0.00%
135
0.03%
137
36.83%
147
>0.00%
148
>0.00%
149
>0.00%
150
>0.00%
151
1.70%
152
1.15%
151
>0.00%
152
>0.00%
153
0.56%
154
>0.00%
155
0.12%
the 233U fission cycle which will not undergo
31(t1/2) in less than 100 years represent a total
of 18.56% of the waste mass. The primary
isotopes within this mass are those of 99Tc,
133
Cs, and 137Cs, comprising 95.4% of the
total.
46
6.2) Uranium-235 [235U] Waste Analysis
Of the four viable fissile fuel types, the 235U is the only isotope that exists in
natural ore on Earth. 235U exists as approximately 0.7% of natural ore, and is rarely
enriched beyond 20% for energy production. Under normal circumstances, this results in
significant transuranic isotope production through transmutation of fertile 238U in the fuel.
Isotopes created through transmutation of non-fissile isotopes are not included in this
analysis. Also note that this section only refers to fission products produced by 235U
fission, and does not include fission products created through subsequent fission of
transmuted isotopes. Refer to section 6.5 for complete LFNR fuel cycle analysis.
47
6.2.a)
Gaseous
Table 7 - Uranium-235 [235U] Gaseous Waste Mass
% of
Mass
Isotope
Common
Name
Symbol
Atomic
Number
The gaseous products created through
36
Kr
Krypton
83
3.04%
54
Xe
Xenon
131
16.44%
134
44.51%
135
1.46%
136
34.56%
the 235U fission cycle represent a total of
17.63% of the waste mass. Collecting the
naturally off-gassed Kr and Xe would reduce
the waste mass by 1/5th.
48
6.2.b)
Stable Solids
Table 8 - Uranium-235 [235U] Stable Solid Waste Mass
Atomic
Number
Symbol
Common
Name
Isotope
% of
Mass
The stable solid fission products created
through the 235U fission cycle represent a total
42
Mo
Molybdenum
95
39.57%
47
Ag
Silver
109
0.19%
of 16.53% of the waste mass. The primary
48
Cd
Cadmium
113
0.09%
49
In
Indium
115
0.07%
60
Nd
Neodymium
143
145
36.08%
23.84%
154
155
156
157
158
>0.00%
>0.00%
0.09%
0.04%
0.02%
160
161
162
163
164
>0.00%
>0.00%
>0.00%
>0.00%
>0.00%
64
66
Gd
Dy
Gadolinium
Dysprosium
67
Ho
Holmium
165
>0.00%
68
Er
Erbium
166
167
>0.00%
>0.00%
isotopes within the stable solid mass are 95Mo,
143
Nd, and 145Nd, comprising 99.49% of the
total.
The remaining 0.51% of the stable
solids are a mixture of Ag, Cd, In, Gd, Dy, Ho,
and Er.
49
6.2.c)
90 Day Resting Period
Table 9 - Uranium-235 [235U] 90 Day Decay Waste Mass
Atomic
Number
Symbol
Isotope
% of
Mass
Common
Name
The fission products created through the
235
45
Rh
Rhodium
103
105
>0.00%
13.14%
under 90 days represent a total of 7.43% of the
52
Te
Tellurium
127
0.38%
53
I
Iodine
127
135
1.78%
84.70%
U fission cycle which will undergo 31(t1/2) in
waste mass. The primary isotopes within this
mass are 105Rh, 127I, and 135I, comprising
99.62% of the total.
50
6.2.d)
100 Year Resting Period
Table 10 - Uranium-235 [235U] 100 Year Decay Waste Mass
Ruthenium
% of
Mass
Ru
Isotope
Symbol
44
Common
Name
Atomic
Number
The fission products created through
101
47.37%
103
27.80%
106
3.70%
51
Sb
Antimony
125
0.32%
61
Pm
Promethium
147
10.90%
148
>0.00%
148m
>0.00%
149
9.91%
the 235U fission cycle which will undergo
31(t1/2), between 90 days and 100 years
represent a total of 10.92% of the waste mass.
The primary isotopes within this mass are
those of Ru and Pm, comprising 98.3% of the
total.
51
6.2.e)
Lifetime Entombment
Table 11 - Uranium-235 [235U] Lifetime Entombment Waste Mass
55
62
63
Cs
Sm
Eu
% of
Mass
Tc
Pd
Isotope
Symbol
43
46
Common
Name
Atomic
Number
The fission products created through
Technetium
99
30.31%
Palladium
105
>0.00%
107
0.74%
108
0.27%
Caesium
Samarium
Europium
133
33.05%
134
>0.00%
135
>0.00%
137
31.30%
147
>0.00%
148
>0.00%
149
>0.00%
150
>0.00%
151
2.07%
152
1.32%
151
>0.00%
152
>0.00%
153
0.78%
154
>0.00%
155
0.16%
the 235U fission cycle which will not undergo
31(t1/2) in less than 100 years represent a total
of 20.26% of the waste mass. The primary
isotopes within this mass are those of 99Tc,
133
Cs, and 137Cs, comprising 94.66% of the
total.
52
6.3) Plutonium-239 [239Pu] Waste Analysis
239
Pu is the lightest transuranic isotope capable of maintaining a fission chain
reaction. Since 239Pu is used in high-yield nuclear weapons production, 239Pu has become
one of the most highly regulated isotopes on the planet. Global stockpiles of weaponsgrade Pu in 2014 were 505±10 tons in 2014 (Glaser & Mian, 2015). These existing 239Pu
stockpiles could be utilized in LFNR facilities for energy production, an idea that has
been proposed to support global nuclear weapons anti-proliferation (Gat & Engel, 2000).
Creation of 239Pu through transmutation of 238U requires vast amounts of energy and
produces enormous volumes of high-level waste. From an environmental perspective, Pu
is a poor choice for energy production, simple due to the sheer amount of energy that
must be consumed simply to create the isotope. Though Pu does in fact release more
energy upon undergoing fission, when factoring in the energy required just to make the
isotope the resource cost becomes much larger.
Isotopes created through transmutation of non-fissile isotopes are not included in
this analysis. It should be noted that this section only refers to fission products produced
by 239Pu fission, and does not include fission products created through subsequent fission
of transmuted isotopes. Refer to section 6.5 for complete LFNR fuel cycle analysis.
53
6.3.a)
Gaseous
Table 12 - Plutonium-239 [239Pu] Gaseous Waste Mass
% of
Mass
Isotope
Common
Name
Symbol
Atomic
Number
The gaseous products created through
36
Kr
Krypton
83
1.50%
54
Xe
Xenon
131
19.51%
134
38.74%
135
5.45%
136
34.80%
the 239Pu fission cycle represent a total of
19.77% of the waste mass. This allows for a
nearly immediate mass reduction of one-fifth
by collection of naturally off-gassing Kr and
Xe.
54
6.3.b)
Stable Solids
Table 13 - Plutonium-239 [239Pu] Stable Solid Waste Mass
Atomic
Number
Symbol
Common
Name
Isotope
% of
Mass
The stable solid fission products created
through the 239Pu fission cycle represent a total
42
Mo
Molybdenum
95
34.38%
47
Ag
Silver
109
10.41%
of 14.09% of the waste mass. The primary
48
Cd
Cadmium
113
0.58%
49
In
Indium
115
0.29%
60
Nd
Neodymium
143
145
31.35%
21.22%
154
155
156
157
158
>0.00%
>0.00%
0.89%
0.53%
0.30%
160
161
162
163
164
>0.00%
0.04%
0.02%
0.01%
>0.00%
64
66
Gd
Dy
Gadolinium
Dysprosium
67
Ho
Holmium
165
>0.00%
68
Er
Erbium
166
167
>0.00%
>0.00%
isotopes within the stable solid mass are 95Mo,
143
Nd, and 145Nd, and 109Ag comprising 97.36%
of the total.
The remaining 2.64% of the stable solids are a
mixture of Cd, In, Gd, Dy, Ho, and Er.
55
6.3.c)
90 Day Resting Period
Table 14 - Plutonium-239 [239Pu] 90 Day Decay Waste Mass
Atomic
Number
Symbol
Isotope
% of
Mass
Common
Name
The fission products created through the
239
45
Rh
Rhodium
103
105
>0.00%
44.51%
in under 90 days represent a total of 12.69% of
52
Te
Tellurium
127
0.70%
53
I
Iodine
127
135
3.29%
51.50%
Pu fission cycle which will undergo 31(t1/2)
the waste mass. The primary isotopes within
this mass are 105Rh, 127I, and 135I, comprising
99.3% of the total.
It should be noted that, when compared to fission of U isotopes, 239Pu will
produce much more 105Rh and less 135I. As iodine is more prone to biological uptake than
150
Rh, this does slightly reduce the risk to living organisms posed from this mass.
56
6.3.d)
100 Year Resting Period
Table 15 - Plutonium-239 [239Pu] 100 Year Decay Waste Mass
Ruthenium
% of
Mass
Ru
Isotope
Symbol
44
Common
Name
Atomic
Number
The fission products created through
101
30.53%
103
35.36%
106
22.01%
51
Sb
Antimony
125
0.57%
61
Pm
Promethium
147
5.37%
148
>0.00%
148m
>0.00%
149
6.16%
the 239Pu fission cycle which will undergo
31(t1/2), between 90 days and 100 years
represent a total of 19.77% of the waste
mass. The primary isotopes within this mass
are those of Ru, comprising 87.9% of the
total.
Note that when compared to fission of U isotopes, 239Pu will produce much more
106
Ru.
57
6.3.e)
Lifetime Entombment
Table 16 - Plutonium-239 [239Pu] Lifetime Entombment Waste Mass
55
62
63
Cs
Sm
Eu
% of
Mass
Tc
Pd
Isotope
Symbol
43
46
Common
Name
Atomic
Number
Fission products created through the
Technetium
99
22.83%
Palladium
105
>0.00%
107
12.19%
108
7.91%
Caesium
Samarium
Europium
133
25.69%
134
>0.00%
135
0.05%
137
24.57%
147
>0.00%
148
>0.00%
149
>0.00%
150
>0.00%
151
2.71%
152
2.12%
151
>0.00%
152
>0.00%
153
1.33%
154
>0.00%
155
0.61%
239
Pu fission cycle which will not undergo
31(t1/2) in less than 100 years represent a
total of 27.30% of the waste mass. The
primary isotopes within this mass are those
of 99Tc, 107Pd, 108Pd, 133Cs, and 137Cs,
comprising 93.19% of the total.
58
6.4) Plutonium-241 [241Pu] Waste Analysis
241
Pu is the second-lightest transuranic isotope capable of maintaining a fission
chain reaction. Creation of 241Pu through transmutation of 238U is incredibly energy
intensive and produces enormous volumes of high-level waste, far more-so than 239Pu,
and is rarely a “desired” product within the reactor. Significant global stockpiles of 241Pu
exist, the remnants of decades of weapons grade 239Pu production. Most attempts to
estimate total global volumes have failed due to the long-time secrecy and often poor
record keeping throughout the Cold War. Due to 241Pu’s 14.29-year half-life, significant
quantities of americium-241 [241Am] likely exists within these existing waste stockpiles.
241
Am is very valuable as a necessary component in many modern smoke detectors and
for the construction of micro-scale nuclear batteries. Americium could be extracted from
these masses through isotopic separation processes prior to injection in the core, or
simply injected into the core to undergo burnup. Because of the ability for a LFNR to
achieve very near complete burnup of transuranic isotopes, LFNR facilities could be used
to actively eliminate high-level transuranic waste stockpiles, and at the same time
produce significant quantities of energy.
Isotopes created through transmutation of non-fissile isotopes are not included in
this analysis. Additionally, this section only refers to fission products produced by 241Pu
fission, and does not include fission products created through subsequent fission of
transmuted isotopes. Refer to section 6.5 for complete LFNR fuel cycle analysis.
59
6.4.a)
Gaseous
Table 17 - Plutonium-241 [241Pu] Gaseous Waste Mass
% of
Mass
Isotope
Common
Name
Symbol
Atomic
Number
The gaseous products created through
36
Kr
Krypton
83
1.10%
54
Xe
Xenon
131
17.01%
134
43.22%
135
1.24%
136
37.42%
the 241Pu fission cycle represent a total of
18.23% of the waste mass. This allows for a
nearly immediate mass reduction of 1/5th by
collection of naturally off-gassing Kr and Xe.
60
6.4.b)
Stable Solids
Table 18 - Plutonium-241 [241Pu] Stable Solid Waste Mass
Atomic
Number
Symbol
Common
Name
Isotope
% of
Mass
The stable solid fission products created
through the 241Pu fission cycle represent a total
42
Mo
Molybdenum
95
26.51%
47
Ag
Silver
109
17.37%
of 14.90% of the waste mass. The primary
48
Cd
Cadmium
113
1.00%
49
In
Indium
115
0.24%
60
Nd
Neodymium
143
145
30.79%
22.01%
154
155
156
157
158
>0.00%
>0.00%
1.16%
0.91%
0.62%
160
161
162
163
164
>0.00%
0.06%
>0.00%
>0.00%
>0.00%
64
66
Gd
Dy
Gadolinium
Dysprosium
67
Ho
Holmium
165
>0.00%
68
Er
Erbium
166
167
>0.00%
>0.00%
isotopes within the stable solid mass are 95Mo,
143
Nd, and 145Nd, and 109Ag comprising 96.68%
of the total.
The remaining 3.32% of the stable solids are a
mixture of Cd, In, Gd, Dy, Ho, and Er.
61
6.4.c)
90 Day Resting Period
Table 19 - Plutonium-241 [241Pu] 90 Day Decay Waste Mass
Atomic
Number
Symbol
Isotope
% of
Mass
Common
Name
The fission products created through the
241
45
Rh
Rhodium
103
105
0.00%
45.91%
in under 90 days represent a total of 13.29% of
52
Te
Tellurium
127
0.31%
53
I
Iodine
127
135
1.44%
52.34%
Pu fission cycle which will undergo 31(t1/2)
the waste mass. The primary isotopes within
this mass are 105Rh, 127I, and 135I, comprising
99.69% of the total.
It should be noted that like 239Pu, when compared to fission of U isotopes, 241Pu
will produce much more 105Rh and less 135I. As Iodine is more prone to biological uptake
than 150Rh, this does slightly reduce the risk to living organisms posed from this mass.
62
6.4.d)
100 Year Resting Period
Table 20 - Plutonium-241 [241Pu] 100 Year Decay Waste Mass
Ruthenium
% of
Mass
Ru
Isotope
Symbol
44
Common
Name
Atomic
Number
The fission products created through
101
28.52%
103
31.01%
106
27.95%
51
Sb
Antimony
125
0.21%
61
Pm
Promethium
147
5.54%
148
>0.00%
148m
>0.00%
149
6.76%
the 241Pu fission cycle which will undergo
31(t1/2), between 90 days and 100 years
represent a total of 19.77% of the waste
mass. The primary isotopes within this mass
are those of Ru, comprising 87.48% of the
total.
It should be noted that like 239Pu, when compared to fission of uranium isotopes,
239
Pu will produce much more 106Ru.
63
6.4.e)
Lifetime Storage
Table 21 - Plutonium-241 [241Pu] Lifetime Storage Waste Mass
55
62
63
Cs
Sm
Eu
% of
Mass
Tc
Pd
Isotope
Symbol
43
46
Common
Name
Atomic
Number
The fission products created through
Technetium
99
19.60%
Palladium
105
>0.00%
107
15.96%
108
12.31%
Caesium
Samarium
Europium
133
21.97%
134
>0.00%
135
>0.00%
137
22.27%
147
>0.00%
148
>0.00%
149
>0.00%
150
>0.00%
151
2.98%
152
2.34%
151
>0.00%
152
>0.00%
153
1.77%
154
>0.00%
155
0.79%
the 241Pu fission cycle which will not
undergo 31(t1/2) in less than 100 years
represent a total of 30.61% of the waste
mass. The primary isotopes within this mass
are those of 99Tc, 107Pd, 108Pd, 133Cs, and
137
Cs, comprising 92.11% of the total.
64
6.5) Summary of Sections 6.1 – 6.4
Figure 5 shows all four
fissile fuel options compared
side-by side. It should be noted
that for the lightest fissile
isotope, 233U, results in nearly
Figure 5 - Side-By-Side Comparison of Fission Products
45% mass that can be considered
“safe” in under 90 days. Conversely 241Pu, the heaviest fissile isotope, produces only 40%
mass that can be considered “safe” in 90 days.
This distinction cannot be emphasized enough. While a difference of only 5%
may seem insignificant, the fission and decay products present within the 100 year and
lifetime entombment masses are among the most dangerous isotopes known by humans.
Many of the long lived isotopes, especially technecium-99 [99, antimony-125 [125Sb],
tellurium-125m [125mTe), caesium [Cs], and samarium-151 [151Sm] are very easily
mobilized through the environment upon release. This contamination can become even
faster when the release occurs in or near an aquatic environment.
While many of the fission products within the “stable solids” and “90 day” groups
are toxic, and therefore do represent a danger upon environmental release. That said,
many of these fission products are in high demand for manufacturing of all sorts of
goods, and as such will likely not simply be disposed of. This makes the disposal and/or
recycling of these products no different than natural mined elements.
Every single fission product within the “gaseous”, “stable solids”, and “90 day”
categories has high demand for modern manufacturing. So while these masses must be
65
handled carefully initially, after an appropriate “safe resting period” [as required by each
individual isotope], they can effectively be considered a resource, versus a waste product.
This distinction is important because in a SFNR the same fission products would exist
within the spent fuel, but they would be directly combined with the more dangerous
isotopes within the fuel pellets. This combined solid state makes effective and safe
reprocessing incredibly complicated and dangerous in general. In the LFNR, the elements
would be separated from each other, allowing for individual masses to safely decay
without risking contamination from longer lived radioisotopes. This drastically reduces
the complexity of waste sequestration, reprocessing, and eventual entombment for LFNR
waste.
Now, we will examine the complete LFNR waste cycle for each fissile fuel,
including all secondary and tertiary fission events.
66
6.6) Expected LFNR waste output
To determine the waste composition created by a fission reactor the following
factors have been defined:
Table 22 - Reactor Burnup Comparisons
Initial Fuel Composition - The
Reactor Design
Burnup Efficiency
~[Gwd/t] (per ton) %
Theoretical Maximum
909
100.0
LFTR
863
95.1
Areva EPR
65
7.2
Westinghouse CAP-1400
59
6.6
Mitsubishi APW
62
6.8
South Korean AP-400
55
6.1
VVER 1200
70
7.7
Hualong One
45
5.0
Areva NP Kerena
65
7.2
Indian AHWR
24
2.6
Indian AHWR-LEU
64
7.0
Chinese HTR-PM
90
9.9
120
13.2
Reduced-Moderation Water Reactor
45
5.0
IRIS
80
8.8
Gidropress VVER-1500
BN-1200
60
6.6
Fort Saint Vrain HTR
170
18.7
Very High-Temperature Reactor
100
11.0
AHTR
156
17.2
ratio of elements that will be dissolved
within the fuel salt in the fissile core. For
example, in a proposed Liquid Fluorine
Thorium Reactor [LFTR], the initial fuel
mass would be comprised of FliBe salt
with a total of ~2.01% of the fuel mass
being comprised of fissile 235U and fertile
232
Th. Once the initial volume of 235U has
undergone fission, there should be no need
for any further addition of fissile fuel, as
all necessary fissile fuel would then be
supplied by the transmutation of 232Th to
233
U. In a traditional uranium fueled Light Water Reactor (LWR), the initial fuel
composition would be comprised of, at most, 20% 235U with the remainder being fertile
238
U.
Reactor Burnup Ratio - The burnup ratio of the reactor determines the volume
of fissile fuel that will undergo fission before no longer being usable within the core.
With solid-fueled reactors, burnup is much lower due to the overall inefficiency of fission
in solid fuels and the need to remove from the core the growing quantities of nuclear
67
poisons contained within the solid fuel. In LFNR systems, the nuclear poisons are
constantly removed from the fuel mass through electrochemical precipitation, and
processed as necessary. This allows for a much more complete burnup of the fissile mass
than would be possible in any SFNR.
Table 22 shows the reactor burnup ratios of many currently operating and
proposed reactor models. All burnup ratios were retrieved from the published literature
provided by the manufacturers or public patent records. The burnup ratios provided were
derived from published sales literature and other public technical information, and have
only been provided to create a frame of reference for analysis. Actual real-world
performance may vary from the published literature.
Fission Thermal Spectrum – The operating temperature of a reactor directly
affects the efficiency of sustained fission within the reactor. Most SFNR are forced to
operate below the ideal thermal range, due to the low vaporization point of the water
coolant. A water-cooled SFNR operates at a maximum of 599oF, well below the efficient
thermal spectrum, whereas LFNR reactors operate well within the effective thermal range
of fission, approximately 1300°F to 1600°F. The higher temperature the core can
maintain, the more efficient the burnup of the reactor will be.
The following summary compares the total lifecycle fission outputs for each
fissile isotope, based on the analysis provided in sections 6.1 - 6.5. For individual isotopic
fission product data, please refer back to sections 6.1 - 6.4. Additional assumptions
underlying sections 6.6.a – 6.6.d:
A FLiBe carrier will be utilized as the fuel carrier (solvent), coolant, and
moderator. This salt will contain 34% beryllium fluoride [BeF2] and 66%
68
lithium fluoride [7LiF]. FLiBe was chosen due to its extreme chemical
stability and imperviousness to radiation. Even when exposed to extreme
temperatures and high levels of radiation, FLiBe will not burn, explode, or
decompose (Delpech, Cabet, Clim, & Picard, 2010). These traits mean that the
FLiBe can be reused for decades, very likely longer than the operating life of
the reactor. Note: All 6Li must be removed from the FLiBe prior to use in the
reactor, as 6Li is known to produce radioactive tritium [4H] when exposed to
neutrons. 6Li exists as approximately ~7.5% of natural lithium.
The LFNR reactor will utilize a dual-core design to facilitate the most
efficient isotopic separation of the waste mass. All fissile, transuranic,
actinide, and lanthanide isotopes will be contained to the inner fuel mass until
removal and processing.
The outer core will utilize a constant electrochemical separation process to
ensure all protactinium-233 [233Pa] created through transmutation of 232Th is
removed from the core before it decays to fissile 233U. 233Pa has a half-life of
only 25.6 days and a 31(t1/2) time of 2.17 years. After a resting period of 25
days to allow 233Pa to decay to 233U. The 233U will be extracted and injected
into the inner core.
The fissile fuel salt mass will be constantly pumped through a series of
electrochemical precipitators, ensuring that all fission products and
transmuted isotopes are removed from the core before being subjected to
further irradiation or being transmute to isotopes heavier than 240Pu.
69
All elements within the fuel mass will be separated through electrochemical
precipitation when possible (as described in sections 6.1 through 6.4).
Separate components of the waste will be processed in the manner most
efficient for each specific element, avoiding unwanted chemical reactions
whenever possible and ensuring the long-term stability of all dangerous
isotopes.
The LFNR electrical output calculation relies on a combined open-air
Brayton-Rankine cycle (Zohuri, McDaniel, & De Oliveira, 2015). The openair Brayton-Rankine cycle allows for a 46% thermal/electrical conversion
efficiency.
70
233
6.6.a)
U LFNR Waste Output
Table 23 - Uranium-233 [233U] Complete Full Cycle Analysis
U-233
U-235
Pu-239
Pu-241
100.00
33.87
9.23
0.59
18.81
17.63
19.77
18.23
15.87
16.53
14.09
14.90
6.08
7.43
12.69
13.29
6.81
10.92
19.77
21.85
18.56
20.26
27.30
30.61
233
Transmuted
Mass (%)
Lifetime Decay
Mass (%)
100-Year
Decay Mass (%)
90-Day Decay
Mass (%)
Stable Solid
Mass (%)
Gaseous
Mass (%)
Fissile Mass
% of Fissile
Mass Remaining
Utilization of
33.86
27.24
6.38
1.12
U as the primary
fissile mass, created
through transmutation
of fertile 232Th, results
in the smallest
volume of high-level waste products. Use of 233U as primary fuel will result in 2.7 times
less transuranic isotopes than 235U, 10 times less than 239Pu, and 160 times less than 241Pu.
Less long lived waste decreases the overall volume of mass that must be safely stored for
long periods of time, it also reduces the resources necessary to handle the mass in
general. All around, less long-lived waste increases the efficiency of any reactor design.
Less fuel required, less waste output, less resources required to handle safe storage, less
environmental risk if an accidental release were to occur, and less cost associated with
the entire endeavor.
The 233U fission cycle results in the highest volume of gaseous and stable solids of
any fissile fuel, allowing for a nearly immediate reduction of the total fuel mass of
47.82%. 6.52% of the mass will be comprised of 135Xe, which will decay to 135Cs in
around 72 days. This 6.52% of the gaseous mass must be added to the mass requiring
lifetime entombment.
The 90-Day mass will be comprised of 82.67% 135I, which will decay to 135Cs.
This 82.67% of the 90-Day mass must be added to the mass requiring lifetime
entombment.
71
Table 24 - Uranium-233 [233U] Post-Fission Cumulative Waste
12.46%
28.12%
Transuranic
Remaining Mass
Lifetime Decay
Remaining Mass
9.85%
100-Year Decay
Remaining Mass
26.71% 22.85%
90-Day Decay
Remaining Mass
Stable Solid
Mass Remaining
Gaseous
Mass Remaining
The transuranic mass will be
0.01%
After Adjustment Mass
24.97% 22.85%
1.71%
12.46%
38.01%
added to the lifetime decay mass due
to high levels of radioactivity and
long half-lives. The lifetime mass
therefore accounts for a total of
38.01% of the total waste mass.
Assuming a burnup rate equal to a LFTR design of 863.5 Gwd/t [95.10%], 4.9% of
the fissile mass will remain entirely unchanged. This mass could be reinserted into the
fissile fuel mass indefinitely.
It should be noted that 39.72 Terawatt days [Twd] is equivalent to 5% of the
global electrical demand in 2014 (IEA, 2015).
If one were to assume the complete burnup of 100 tons of 233U (which is far more
than any singular reactor would require at any one time) after burnup the fissile mass
would create:
24.97 tons of Stable Gaseous Mass requiring no safe storage period
22.85 tons of Stable Solid Mass requiring no safe storage period
1.71 tons requiring a 90-Day safe storage period
12.46 tons requiring a 100 safe storage period
38.01 tons requiring Lifetime Entombment
4.9 tons of unchanged 233U fissile mass
86.35 Terawatt days [Twd] of thermal energy
39.72 Twd of electrical energy
72
235
6.6.b)
U LFNR Waste Output
Table 25 - Uranium-235 [235U] Complete Full Cycle Analysis
U-235
Pu-239
Pu-241
100.00
27.24
1.74
17.63
19.77
18.23
16.53
14.09
14.90
7.43
12.69
13.29
10.92
19.77
21.85
20.26
27.30
30.61
Transmuted
Mass (%)
Lifetime Decay
Mass (%)
100-Year
Decay Mass (%)
90-Day Decay
Mass (%)
Stable Solid
Mass (%)
Gaseous
Mass (%)
Fissile Mass
% of Fissile
Mass Remaining
Use of 235U as
27.24
6.38
1.12
primary fuel will
result in 3.74% times
less transuranic waste
than 239Pu, and 59
times less than 241Pu. 235U can be utilized both without the presence of 238U (as highly
enriched U) or as reactor grade uranium (containing up to 95% fertile 238U), the latter
producing significantly more high-level waste. This analysis assumes the excess 238U will
be removed to prevent excessive transuranic production and reduce the viability of
utilizing LFNR for the creation of weapons-grade Pu-239.
Table 26 - Uranium-235 [235U] Post-Fission Cumulative Waste
Lifetime Decay
Remaining Mass
11.11%
16.68%
28.23%
After Adjustment Mass
22.97% 20.62%
1.70%
16.68%
38.02%
Transuranic
Remaining Mass
100-Year Decay
Remaining Mass
23.33% 20.62%
90-Day Decay
Remaining Mass
Stable Solid
Mass Remaining
Gaseous
Mass Remaining
The 235U fission waste can be
0.02%
quickly reduced by a total fuel mass
of 47.82%. 1.46% of the mass will be
comprised of 135Xe, which will decay
to 135Cs in around 72 days. This
1.46% of the mass must be added to the lifetime entombment mass.
The 90-Day mass will be comprised of 84.7% 135I, which will decay to 135Cs. This
84.7% of the 90-Day mass must be added to the mass requiring lifetime entombment.
The transuranic mass will be added to the lifetime decay mass due to high levels of
radioactivity and long half-lives. The lifetime mass therefore accounts for a total of
38.02% of the total waste mass.
73
Assuming burnup rate equal to the LFTR design rate of 863.5 Gwd/t [95.10%],
4.9% of the fissile mass will remain entirely unchanged. This mass could be reinserted
into the fissile fuel mass indefinitely with proper reprocessing. Removal of all 238U prior
to injection of U into the fissile core is crucial for minimization of overall transuranic
production through the transmutation of 238U. Excess 238U could be utilized in the fertile
core to generate 239Pu, however the potential for nuclear proliferation makes this option
undesirable.
It should be noted that 39.72 Terawatt days [Twd] is equivalent to 5% of the
global electrical demand in 2014 (IEA, 2015).
If one were to assume the complete burnup of 100 tons of 235U (which is far more
than any singular reactor would require at any one time) after burnup the fissile mass
would create:
22.97 tons of Stable Gaseous Mass requiring no safe storage period
20.62 tons of Stable Solid Mass requiring no safe storage period
1.70 tons requiring a 90-Day safe storage period
16.68 tons requiring a 100 safe storage period
38.02 tons requiring Lifetime Entombment
4.9 tons of unchanged 233U fissile mass
86.35 Terawatt days [TWd] of thermal energy
39.72 TWd of electrical energy
74
6.6.c)
239
Pu LFNR Waste Output
Table 27 - Plutonium-239 [239Pu] Complete Full Cycle Analysis
Transmuted
Mass (%)
Lifetime Decay
Mass (%)
100-Year
Decay Mass (%)
90-Day Decay
Mass (%)
Stable Solid
Mass (%)
Gaseous
Mass (%)
% of Fissile
Mass Remaining
Fissile Mass
Use of 239Pu
as a fissile fuel is
generally undesirable,
because heavier
Pu-239 100.00% 19.77% 14.09% 12.69% 19.77% 27.30% 6.38%
Pu-241 6.38% 18.23% 14.90% 13.29% 21.85% 30.61% 1.12%
isotopes are more
likely to transmute into heavier transuranic isotopes. The appeal of utilizing 239Pu as a
fuel source is the potential for active elimination of existing nuclear weapon stockpiles.
Environmentally speaking, the waste volume produced from 239Pu production is
significant, though is not included in this section of the analysis.
Table 28 - Plutonium-239 [239Pu] Post-Fission Cumulative Waste
20.93% 15.04% 13.54% 21.16% 29.26%
After Adjustment Mass
20.67% 15.04%
6.57% 23.16% 36.56%
Transuranic
Remaining Mass
Lifetime Decay
Remaining Mass
100-Year Decay
Remaining Mass
90-Day Decay
Remaining Mass
Stable Solid
Mass Remaining
Gaseous
Mass Remaining
The 239Pu fission waste can be
0.07%
nearly immediate reduced by a total
mass of 35.71%. 1.24% of the mass
will be comprised of 135Xe, which will
decay to 135Cs in around 72 days. This
1.24% of the gaseous mass must be added to the mass requiring lifetime entombment.
The 90-Day mass will be comprised of 51.5% 135I, which will decay to 135Cs. This
51.5% of the 90-Day mass must be added to the mass requiring lifetime entombment.
The transuranic mass will be added to the lifetime decay mass due to high levels of
radioactivity and long half-lives. The lifetime mass therefore accounts for a total of
36.56% of the total waste mass.
75
Assuming burnup rate equal to a LFTR design of 863.5 Gwd/t [95.10%], 4.9% of
the fissile mass will remain entirely unchanged. This mass could be reinserted into the
fissile fuel mass indefinitely with proper reprocessing.
It should be noted that 39.72 Terawatt days [Twd] is equivalent to 5% of the
global electrical demand in 2014 (IEA, 2015).
If one were to assume the complete burnup of 100 tons of 239Pu (which is far more
than any singular reactor would require at any one time) after burnup the fissile mass
would create:
20.67 tons of Stable Gaseous Mass requiring no safe storage period
15.04 tons of Stable Solid Mass requiring no safe storage period
6.57 tons requiring a 90-Day safe storage period
23.16 tons requiring a 100 safe storage period
36.56 tons requiring Lifetime Entombment
4.9 tons of unchanged 233U fissile mass
86.35 Terawatt days [Twd] of thermal energy
39.72 Twd of electrical energy
76
241
6.6.d)
Pu LFNR Waste Output
Table 29 - Plutonium-241 [241Pu] Complete Full Cycle Analysis
Transmuted
Mass (%)
Lifetime Decay
Mass (%)
100-Year
Decay Mass (%)
90-Day Decay
Mass (%)
Stable Solid
Mass (%)
Gaseous
Mass (%)
Fissile Mass
% of Fissile
Mass Remaining
241
Pu is the
most undesirably of
all fissile fuel, as
heavier isotopes are
Pu-241 100.00% 18.23% 14.90% 13.29% 21.85% 30.61% 1.12%
more likely to transmute into more dangerous transuranic isotopes. The appeal of
utilizing 241Pu as a fuel source is the potential for active elimination of existing high-level
nuclear waste remaining from past nuclear projects. Environmentally speaking, the waste
volume produced from 241Pu production is significant, though is not included in this
analysis.
Table 30 - Plutonium-241 [241Pu] Post-Fission Cumulative Waste
Lifetime Decay
Remaining Mass
13.29%
21.85%
30.61%
After Adjustment Mass
18.00% 14.90%
6.33%
21.85%
38.92%
Transuranic
Remaining Mass
100-Year Decay
Remaining Mass
18.23% 14.90%
90-Day Decay
Remaining Mass
Stable Solid
Mass Remaining
Gaseous
Mass Remaining
The 241Pu fission waste can be
1.12%
nearly immediate reduced by a total
mass of 47.82%. 1.24% of the mass
will be comprised of 135Xe, which
will decay to 135Cs in around 72 days.
This 1.24% of the gaseous mass must be added to the mass requiring lifetime
entombment.
The 90-Day mass will be comprised of 52.34% 135I, which will decay to 135Cs.
This 52.34% of the 90-Day mass must be added to the mass requiring lifetime
entombment.
The transuranic mass will be added to the lifetime decay mass due to high levels
of radioactivity and long half-lives. The lifetime mass therefore accounts for a total of
38.92% of the total waste mass.
77
Assuming burnup rate equal to a LFTR design of 863.5 Gwd/t [95.10%], 4.9% of
the fissile mass will remain entirely unchanged. This mass could be reinserted into the
fissile fuel mass indefinitely with proper reprocessing.
It should be noted that 39.72 Terawatt days [Twd] is equivalent to 5% of the
global electrical demand in 2014 (IEA, 2015).
If one were to assume the complete burnup of 100 tons of 241Pu (which is far more
than any singular reactor would require at any one time) after burnup the fissile mass
would create:
18.00 tons of Stable Gaseous Mass requiring no safe storage period
14.90 tons of Stable Solid Mass requiring no safe storage period
6.33 tons requiring a 90-Day safe storage period
21.85 tons requiring a 100 safe storage period
38.92 tons requiring Lifetime Entombment
4.9 tons of unchanged 233U fissile mass
86.35 Terawatt days [Twd] of thermal energy
39.72 Twd of electrical energy.
78
6.7) LFNR/SFNR Comparison
This section is provided solely to provide some context for evaluating LFNR
waste production. It is very difficult to directly compare LFNR waste production to that
of traditional SFNR. In a LFNR system, all fission products are actively removed from
the fuel mass. Removing fission products eliminates the constantly generated nuclear
poisons, ensuring the fission chain reaction can be sustained with a minimum of energy
loss. This isotopic separation also ensures that all fissile isotopes remain in the core and
will not be removed until they are consumed.
In a SFNR, the fission products generally remain trapped within the solid fuel
pellets. Trapping these fission products within the solid fuel helps prevent the release of
fission products and transuranic elements into the reactor vessel or the environment.
Eventually, fission products will be present in high enough quantities to actually inhibit
the fission process. This “spent” fuel, generally after 1.5-3 years within the core, must be
replaced by fresh fuel. Often as little as 3% of the fissile mass within the fuel mass has
been consumed through fission, leaving as much as 97% fuel unconsumed.
For the following assumptions will be made for the following comparison:
A fuel mix of 5% 235U and 95%238U. This is comparable to modern reactorgrade fuel used in reactors around the world.
Fuel will be left within the core until the fuel contains 0.9% 235U, 0.6% 239Pu,
0.4% 238Pu/240Pu, and 95% 238U. The remaining 3.1% is comprised of fission
products and very small quantities.
79
As is the case for most modern spent solid fuel, the fuel mass will not be
isotopically separated. Therefore, the entire fuel mass must be permanently
entombed.
Electrical output is based on the assumption that a combined open-air
Brayton-Rankine cycle will be utilized (Zohuri, McDaniel and De Oliveira
2015). The open-air Brayton-Rankine cycle allows for a 46%
thermal/electrical conversion efficiency.
The reactor uses pressurized light water as primary coolant.
Based on of 100 tons of 235U, after burnup this theoretical SFNR would create:
2439 tons of waste requiring Lifetime Entombment
86.35 Terawatt days [Twd] of thermal energy
39.72 Twd of electrical energy
This quick comparison shows even a very efficient uranium fueled SFNR will
generate significantly higher volumes of waste requiring Lifetime Entombment. In this
example, the theoretical SFNR would generate more than 64 times the mass of high-level
waste. In addition, numerous radioactive isotopes are created through neutron irradiation
of impurities within the coolant. Neutron bombardment of water also leads to tritium [3H]
and carbon [14C] production, both radioactive isotopes capable of forming gaseous and
liquid compounds. This irradiated coolant is classified as low-level radioactive waste, as
most fission products within the mass will decay in less than 500 years. This additional
waste mass has been left out of this comparison since this comparison seeks only to
examine the products produced within the core itself. It should be noted that the mass of
80
this reactor-generated low-level waste can be in excess of 45 times the high-level waste
mass.
81
7)
Discussion
As outlined in section 3.2, liquid fueled nuclear reactors [LFNR] have become a
popular topic in the nuclear science world since renewed interest began in the late 1990’s.
The data shows that while the volume of dangerous isotopes within LFNR waste mass is
significant, the manner in which individual elements can be extracted from the fuel salt
greatly reduces the volume of waste requiring long term storage as well as the threat
presented by radioactive decay. Long lived unstable isotopes are still produced, but can
be separated from the less dangerous fission products and entombed far more easily than
can be accomplished with any Solid-Fueled Nuclear Waste [SFNR] waste. The high-level
waste reduction of 64 times for 235U fission is very significant: While these high-level
wastes still represent very serious threat to living organisms for thousands of years, the
drastic reduction in their volume when compared to SFNR is perhaps the strongest
advantage the LFNR technology offers.
This analysis shows that from a numbers standpoint, LFNR tech shows incredible
promise as a truly near-zero carbon energy source. In a world currently being ravaged by
the effects of global climate change, where so much attention is being directed towards
the big carbon producing industries, LFNR appears to offer a large-scale solution that
could have significant impact on the global carbon output. In addition to the waste
analysis within this thesis, existing analysis of the technical operating parameters, show
that LFNR offer an unprecedented level of safety for a nuclear reactor. As incidents like
Chernobyl and Fukushima have shown, water cooled reactors are inherently dangerous
and prone to violent failure. Similar incidents would be impossible from a LFNR style
reactor, as the reactor cannot achieve the temperatures required to phase change the
82
fluoride salts from liquid to gaseous state. Combined with very low expansion
characteristics, the use of fluoride salts results in operating conditions no more dangerous
than a typical coal fired power plant.
As another tool for comparison, consider what the impacts of coal based energy
would be. To generate the same energy as 100 tons of 233U would require the combustion
of 350 million tons of high-grade anthracite coal. In a modern “clean coal” plant, this mass of
coal would result in the release of [but not limited to]:
2 Gt (gigatonnes) of Carbon Dioxide [CO2] (~20% current global CO2 output)
115, 507 tons of Sulfur Dioxide [SO2]
200 Mt of Nitrogen Oxide [NO]
122,000 tons of airborne particulates
53,000 tons of airborne hydrocarbons
175,000 tons of Carbon Monoxide [CO]
27.5 tons of Arsenic
14 tons of Lead
0.5 tons of Cadmium
86.35 Terawatt days [Twd] of thermal energy
39.72 Twd of electrical energy
Caveats: LFNR technology shows incredible promise for a world desperately in
need of a near-zero carbon high-energy density power source to meet the constantly
growing global demand. LFNR technology still requires significant research before largescale implementation will be viable. The very high temperatures of the reactor core
require very specific engineering solutions to ensure components do not degrade or
become seriously damaged during ongoing operation, potentially creating a release of
83
dangerous isotopes. Until recently, manufacture of the graphite components was
incredibly difficult. Advancements in 3D printing technology may offer a cost effective
and reliable manufacturing method for these components (Dalton, 2016).
In addition, with some fissile fuel types, there is a definite risk for potential nuclear
proliferation. In the case of the 233U cycle, the natural presence of protactinium with it’s half-life
of around 25 days effectively “contaminates” the fissile mass, making it unusable for weapons
production (Brown, Dixon, & Rogers, 1968). This natural “anti-proliferation” aspect of the 233U is
often cited as a reason to support LFNR development (Gat & Engel, 2000).
The inability for the fuel salt mass to enter a “meltdown” state is another clear advantage
over SFNR. The natural thermal characteristics give the fuel mass a strong negative void
coefficient. Upon overheating, the thermal cross-section of fertile isotopes within the mass will
increase, resulting in increased transmutation and decreased fission. This reaction creates a
condition often cited as “self-regulating”, and is an important safety feature that does not exist
within standard SFNR.
A major hindrance to the technology is the general lack of funding for associated
research. Research dollars are almost always limited, and similar projects must frequently
compete for the limited funds. In addition, the very fact that fissile isotopes are radioactive makes
research time consuming, costly, and creates inherent risk to the researchers. This limits the
number of researchers with the access to the resources, facilities, and knowledge bases necessary.
While many of the claims about LFNR may be incorrect, or at times highly misleading,
the math shows that LFNR does appear to offer the traits to make it a valuable partner in halting
or even repairing anthropogenic climate change. In this case, the proof does appear to be in the
pudding.
84
8)
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9)
Appendix
9.1) Terminology
Alpha Particle – Governed by the Nuclear Force and Electromagnetic Force.
Radiative decay that emits a highly-charged Helium-4 [4H] nucleus. Will result in
transmutation to an element 2 protons lighter and 2 less neutrons than the decayed atom.
Generally, only seen in heavier isotopes.
Beta Particle – Mediated by the weak force. Radiative decay caused by 1) a
neutron within the atomic nucleus gaining a positive charge and creating an electron and
electron antineutrino or 2) A proton within the atomic nucleus becoming a neutron,
creating a positron and electron neutrino.
Boson – One class of subatomic particles that comprise the universe, the other
being Fermions. Bosons can occupy the same space at the same time. A good example of
a Boson would be a Photon.
Burnable Poison – Used in some reactors that do not require control rods.
Burnable poisons, such as boron or gadolinium, are added to fuel piles to control core
flux. Burnable poisons are consumed throughout the operating of a reactor. LFNR do not
require burnable poisons.
Burnup – The total volume of mass converted to energy through fission in a
nuclear reactor. Burnup is represented as 𝑥 = 𝐺𝑤𝐷 ⁄𝑡 [Gigawatt Days / Tons of fuel].
Cluster Decay – Rare form of nuclear decay in which an atomic nucleus emits a small
number of neutrons and protons, larger than an alpha particle but smaller than a
traditional binary fission fragment. Ternary fissions, which are also extraordinarily rare,
will also emit fission products of similar size.
100
Coolant – A substance, generally a liquid or gas, used to transfer heat generated
within the reactor core to heat exchangers.
Control Rod – Used in SFNR to control reactor core. Made of elements capable
of absorbing neutrons without reacting; such as boron, sliver, indium, and cadmium.
Control rods must be physically or mechanically manipulated.
Criticality – All fissile isotopes have a point of “criticality”. Criticality is
determined by the density, size, shape, enrichment, temperature, and proximity of nearby
substances. For example, U-233 has a criticality of mass of 15 kg in a spherical
configuration, assuming no surrounding moderators or neutron reflectors which could
increase criticality. Therefore, care must be taken to ensure no volume of any fissile or
fissionable isotope is allowed to reach a state of criticality. Upon going critical, the fissile
mass will begin emitting very strong high levels of gamma rays, X-rays, alpha particles,
and beta particles. Many deaths have occurred due to accidentally created criticalities.
Worst case scenario (though unlikely), would be fissile mass creating a thermonuclear
detonation. The volume of material and specific circumstances for this scenario make it
nearly impossible to occur without deliberate intent.
Daughter Isotope – Any isotope that is created through the decay of another
isotope.
Decay – The process in which an unstable isotope “ejects” either a neutron,
proton, electron, subatomic particles, or radiates energy to become a lighter isotope and
eventually become a stable isotope. Decay is measured in “Half-Lives”.
Double Beta Decay – Mediated by the Weak Force. Radiative decay caused by 1)
Two neutrons within the atomic nucleus gaining a positive charge and creating two
101
positrons and two electrons or 2) Two protons in the atomic nucleus becoming neutrons,
creating two neutrinos and two electrons.
Electromagnetic Force - One of the four fundamental forces of nature. The other
three being Gravity, Strong Force, and Weak Force. Responsible for most phenomenon in
the known universe. At an atomic level, electromagnetic force explains the interactions
between positive, negative, and neutral particles.
Element – Classification for individual atoms. Element number is equal to the
number of protons in the atomic nucleus.
Fermion – One class of subatomic particles that comprise the universe, the other
being Bosons. Fermions are particles that cannot occupy the same space at the same time.
Electrons are a good example of a Fermion, as two electron’s orbiting an atomic nucleus
cannot follow the exact same path or they would collide (if not naturally repelled by their
negative charges.)
Fertile – An isotope that can accept a neutron to become a fissile isotope. Fertile
isotopes include: Thorium-232, Uranium-234, Uranium-238, Plutonium-238, Plutonium241.
Fissile – An isotope that can be split by a thermal neutron with enough reliability
to sustain a chain reaction, generating energy and fission products. Fissile isotopes
include: Uranium-233, Uranium-235, Plutonium-239, and Plutonium-241
Fissionable – An isotope that, though incapable of sustaining a chain reaction,
can achieve fission with any type of neutron, even with very low probability. All isotopes
heavier than Uranium 233 are fissionable.
102
Gamma Decay – Release of highly charged ionizing radiation. Very dangerous to
living organisms. In nuclear chemistry, all electromagnetic radiation emitted during
nuclear decay is referred to as gamma rays, regardless of lower energy threshold. Caused
by release of nucleonic binding energy.
Half Life – The amount of time required for 50% of an unstable isotope to decay
into a lighter isotope.
Isometric Transition – Radiative decay associated with Gamma Decay. Upon a
Gamma emission, there is a chance the gamma ray will excite an electron around the
nuclei, in which case the atom will eject a high-energy electron (Internal Conversion).
This differs from a Beta Decay, in that the electron is not newly created by the event.
Does not result in a change of isotope, but does release gamma radiation. Possible during
any gamma decay reaction. Internal conversion does not relate to decrease in atomic
mass, and therefore does not result in transmutation directly, but can result in a lighter
isotope.
Isotope – Classification for elements that have the same number of protons, but
differing number of neutrons. Most elements have several isotopes, however often only a
few are stable.
Lanthanides – Elements with atomic numbers between 57 and 71. These
elements all share similar chemical traits with Lanthanum, hence their name. Lanthanides
are extraordinarily rare in nature, and are involved with no known biological processes.
All non-radioactive lanthanides are considered to be of very low toxicity.
103
Moderator – A medium used to slow fast neutrons generated by fission,
converting them to thermal neutrons capable of sustaining a nuclear chain reaction.
Common moderators are water, graphite, deuterium oxide, or Beryllium.
Negative Void Coefficient – The likelihood of a reaction increasing or
decreasing depending on the presence of voids within the reactor core. This can occur
due to coolant loss or other malfunctions within a reactor. A void coefficient of “0.0” is
considered stable. Negative void coefficient can be used as a final safety measure, as a
strongly negative coefficient will result in a core quickly cooling and ceasing fission
upon reactor failure.
Nuclear Poison – aka Neutron Poison. An isotope with a very large neutron
absorption cross-section. Presence of nuclear poison within a reactor can reduce
efficiency of chain reaction. Common nuclear poisons are: Xenon-135, Samarium-149,
Boron, Dysprosium, Europium, Gadolinium, Hafnium, and Iodine.
Nuclear Transmutation – The conversion of one element/isotope to an another
element/isotope through neutron absorption or nuclear decay.
Proliferation-Ready – Any isotope that can be used to create nuclear weaponry.
U-235, Pu-239, Pu-241 are the most desired weapons grade fissile isotopes. Most other
fissile isotopes are too prone to spontaneous fission to be safe for use in bomb cores.
Pyrophoric – Any compound that is likely to spontaneously ignite when exposed
to air, and often water. Most metals are pyrophoric when in a state with large exposed
surface areas [such as when powdered or sliced thinly].
Salt Loop – A single, sealed system designed to circulate the fuel mass between
the core and heat exchangers. A single core reactor would have a 3 loop system (hot-salt
104
loop, cold-salt loop, cold loop). Fissile isotopes and fission products would be isolated to
the hot-salt loop. In a dual core reactor (inner fissile core and outer fertile blanket), the
primary hot-salt loop would circulate only fluid from the inner core (fissile isotopes and
fuel salt) and the secondary hot-salt loop would be used to circulate the outer fertile fuel
salt.
Self-Regulate – In nuclear chemistry, “self-regulate” refers to certain reactor
configurations that will result in some degree of natural fission regulation without outside
manipulation.
Sister Isotope – Isotopes of the same atomic number, and hence the same number
of protons.
Spontaneous Fission – A form of fission that can occur without being induced by
a neutron. All element larger than 232Th and several unstable actinide fission products
can undergo spontaneous fission. Products of spontaneous fission can include any of the
isotopes produced through an induced fission, and can be binary or ternary events.
However, due to the exceedingly rare occurrence of spontaneous fission, the products can
effectively be ignored. What cannot be ignored is the potential for criticality when storing
any volume of any concentrated isotope capable of both achieving a fission reaction
AND a spontaneous fission reaction.
Strong Force / Strong Interaction / Strong Nuclear Force – One of the four
fundamental forces of nature. The other three being Gravity, Electromagnetism, and
Weak Force. Strong Force is the most powerful force of the fundamental forces; being
around 100 times stronger than electromagnetism, approximately a million times stronger
than weak force, and 1038 times stronger than gravity. Strong Force operates only at
105
distances under one femtometer, or approximately the width of one proton. For fission to
occur, a neutron must travel within 1 femtometer of the nuclei for Strong Force to bind to
the nuclei. This mass change will then induce the effects of the Weak Force, resulting in
fission.
Transuranic – All elements larger than Uranium-238. Though transuranic
elements may have been created through stellar formation, all are highly radioactive and
possess half-lives significantly shorter than the age of the Earth (4.5 Billion years). All
transuranic elements no longer exist naturally on Earth, as any that may have once been
created have long since decayed. Not all transuranic isotopes are fissile, but all are
fissionable.
Weak Force / Weak Interaction / Weak Nuclear Force – One of the four
fundamental forces of nature. The other three being Gravity, Electromagnetism, and
Strong Force. Weak Force refers to the manner in which subatomic particles (Bosons and
Fermions) interact. Weak Force is responsible for all radioactive decay and is crucial in
fission itself. Weak force has the smallest range of effect of the fundamental forces.
Weak Force always works to arrange the subatomic particles that comprise matter into
the most energetically stable configuration possible.
106
9.2) Fission Product Data [By Isotope]
Decay Mode
Likelihood of Creation (%)
N
N 7.07E-08 Ne-23
β−
14
N
N
N
N
STABLE
N
N
N
N
N
STABLE
N
N
Y
N
N
N 1.18E-06 Na-23
β−
100
N
N
N
Y
N
N
N 6.43E-06 Na-24
β−
100
N
N
N
N
Y
N
N
N 1.91E-08 Na-25
β−
N
N
N
N
Y
N
N
N 6.25E-09 Na-25
β−
0.1
N
N
N
N
N
Y
N
N
N 6.25E-09 Na-26
β−
99.9
S
Y
Y
Y
Y
N
N
N
N
N
S
Y
Y
Y
Y
N
Y
N
N
N 1.71E-03 Mg-24
β−
100
25
S
N
Y
Y
Y
N
Y
N
N
N 1.87E-06 Mg-25
β−
26
S
N
Y
Y
Y
N
Y
N
N
N 3.42E-08 Mg-26
β−
24
S
Y
Y
Y
Y
N
N
N
N
N
STABLE
25
S
Y
Y
Y
Y
N
N
N
N
N
STABLE
26
S
Y
Y
Y
Y
N
N
N
N
N
STABLE
28
S
N
Y
Y
Y
N
Y
N
N
N 2.39E-03
Al-28
β−
100
30
S
N
Y
Y
Y
N
Y
N
N
N 1.06E-08
Al-29
β−
100
30
S
N
Y
Y
Y
N
Y
N
N
N 1.06E-08
Al-30
β−
6
28
S
N
Y
Y
Y
N
Y
N
N
N 4.26E-06
Si-28
β−
100
29
S
N
Y
Y
Y
N
Y
N
N
N 1.25E-05
Si-29
β−
30
S
N
Y
Y
Y
N
Y
N
N
N 1.14E-07
Si-30
β−
28
S
Y
Y
N
N
N
N
N
N
N
STABLE
29
S
Y
Y
N
N
N
N
N
N
N
STABLE
30
S
Y
Y
N
N
N
N
N
N
N
STABLE
32
S
N
Y
N
N
N
Y
N
N
N 1.53E+02
P-32
β−
6
C
Carbon
14
G
Y
N
N
N
N
Y
N
N
N 5.73E+03
7
N
Nitrogen
14
G
Y
N
N
N
N
N
N
N
N
8
O
Oxygen
20
G
N
Y
Y
N
N
Y
N
N
N 4.28E-07
9
F
Fluorine
20
G
N
Y
Y
N
Y
Y
N
N
23
G
N
Y
Y
N
Y
Y
N
23
G
N
Y
Y
N
Y
Y
20
G
Y
N
N
N
N
22
G
Y
N
N
N
23
G
N
N
N
24
G
N
N
25
G
N
26
G
N
26
G
23
24
10
11
Ne
Na
Neon
Sodium
12 Mg Magnesium
13
14
Al
Si
Aluminum
Silicon
Half Life (years)
Proliferation Threat?
N
Fissionable?
86
Fissile?
β−
Radioactive
N 7.07E-08 Ne-22
Biologically Dangerous
100
N
Pyrophoric
β−
Explosive
N 3.54E-07 Ne-20
Reactive
100
Demand
β−
Gas/Solid (G/S)
F-20
Isotope
100
Common Name
β−
Symbol
N-14
Atomic Number
Daughter Element
Table 31 - Fission Product Data
STABLE
STABLE
107
34
S
N
Y
N
N
N
Y
N
N
N 8.78E-08
P-34
β−
32
S
Y
Y
Y
Y
Y
Y
N
N
N 3.91E-02
S-32
β−
34
S
N
Y
Y
Y
Y
Y
N
N
N 3.96E-07
S-34
β−
32
S
Y
Y
Y
N
N
N
N
N
N
STABLE
34
S
Y
Y
Y
N
N
N
N
N
N
STABLE
83
G
Y
N
N
N
N
N
N
N
N
STABLE
42 Mo Molybdenum
95
S
Y
N
N
N
N
N
N
N
N
STABLE
43
Tc
Technetium
99
S
N
N
N
N
N
Y
N
N
N 2.11E+05 Ru-99
44
Ru
Ruthenium
99
S
Y
N
N
N
Y
N
N
N
N
STABLE
101
S
Y
N
N
N
Y
N
N
N
N
STABLE
103
S
N
N
N
N
Y
Y
N
N
106
S
Y
N
N
N
Y
Y
N
103
S
Y
N
N
N
N
N
105
S
N
N
N
N
N
106
S
N
N
N
N
105
S
Y
N
N
106
S
Y
N
107
S
N
108
S
107
15
16
36
45
46
47
P
S
Kr
Rh
Pd
Ag
Phosphorus
Sulfur
Krypton
Rhodium
Palladium
Silver
>0.0
β−
100
N 1.08E-01 Rh-103
β−
100
N
N 1.02E+00 Rh-106
β−
100
N
N
N
Y
N
N
N 4.04E-03 Pd-105
β−
100
N
Y
N
N
N 9.45E-07 Pd-106
β−
100
N
N
N
N
N
N
STABLE
N
N
N
N
N
N
N
STABLE
N
N
N
N
Y
N
N
N 6.50E+06 Ag-107
β−
100
Y
N
N
N
N
N
N
N
N
STABLE
S
Y
N
N
N
N
N
N
N
N
STABLE
109
S
Y
N
N
N
N
N
N
N
N
STABLE
β−
100
β−
100
STABLE
48
Cd
Cadmium
113
S
Y
N
Y
N
Y
Y
N
N
N 8.04E+15 In-113
49
In
Indium
113
S
Y
N
N
N
N
N
N
N
N
115
S
N
N
N
N
N
Y
N
N
N 4.41E+14 Sn-115
STABLE
50
Sn
Tin
115
S
Y
N
N
N
N
N
N
N
N
51
Sb
Antimony
125
S
N
N
N
N
Y
Y
N
N
N 2.76E+00
52
Te
Tellurium
125
S
Y
Y
Y
Y
Y
N
N
125m
S
N
Y
Y
Y
Y
Y
N
127
S
N
Y
Y
Y
Y
Y
127
S
Y
Y
N
N
N
135
S
N
Y
N
N
N
131
G
Y
Y
Y
N
134
G
Y
Y
Y
135
G
N
Y
Y
136
G
Y
Y
133
S
Y
S
N
S
S
53
54
55
I
Xe
Cs
Iodine
Xenon
Caesium
134
135
STABLE
Te125m
β−
N
N
N
N 1.57E-01 Te-125
IT
100
N
N
N 1.07E-03
β−
100
N
N
N
N
Y
N
N
N 7.50E-04 Xe-135
β−
100
N
N
N
N
N
STABLE
N
N
N
N
N
N
STABLE
N
N
Y
N
N
N 1.04E-03 Cs-135
β−
100
Y
N
N
N
N
N
N 2.17E+21
Y
N
Y
Y
N
N
N
N
Y
N
Y
Y
Y
N
N
N 2.07E+00 Ba-134
β−
100
N
Y
N
Y
Y
Y
N
N
N 2.07E+00 Xe-134
EC
<0.1
N
Y
N
Y
Y
Y
N
N
N 2.30E+06 Ba-135
β−
100
100
STABLE
I-127
STABLE
STABLE
108
S
Y
Y
N
Y
Y
Y
N
N
N 3.02E+01 Ba-137
β−
S
Y
Y
N
Y
Y
Y
N
N
N 3.02E+01
β−
134
S
Y
Y
N
Y
Y
N
N
N
N
STABLE
135
S
Y
Y
N
Y
Y
N
N
N
N
STABLE
137
S
Y
Y
N
Y
Y
N
N
N
N
STABLE
137m
S
N
Y
N
Y
Y
Y
N
N
N 4.86E-06 Ba-137
140
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
143
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
144
S
Y
Y
Y
Y
Y
N
N
N
N 2.29E+15 Ce-140
145
S
Y
Y
Y
Y
Y
N
N
N
N
147
S
Y
Y
N
N
N
Y
N
N
148
S
N
Y
N
N
N
Y
N
148m
S
N
Y
N
N
N
Y
Y
N
N
N
Y
137
56
Ba
Barium
58
Ce
60
Nd Neodymium
Cerium
61 Pm Promethium
62 Sm
63
Eu
64 Gd
66
Samarium
Europium
Gadolinium
Dy Dysprosium
Ba137m
5
95
IT
100
α
100
N 2.62E+00 Sm-147
β−
100
N
N 1.47E-02 Sm-148
β−
100
N
N
N 1.13E-01 Sm-148
β−
95
N
N
N 1.13E-01 Pm-148
IT
5
β−
100
STABLE
S
N
149
S
N
Y
N
N
N
Y
N
N
N 6.06E-03 Sm-149
147
S
Y
Y
Y
Y
N
Y
N
N
N 1.06E+11 Nd-143
α
100
148
S
Y
Y
Y
Y
N
Y
N
N
N 7.00E+15 Nd-144
β−
100
149
S
Y
Y
Y
Y
N
Y
N
N
N
STABLE
150
S
Y
Y
Y
Y
N
Y
N
N
N
STABLE
151
S
N
Y
Y
Y
N
Y
N
N
N 8.88E+01 Eu-151
β−
100
152
S
Y
Y
Y
Y
N
Y
N
N
N
STABLE
154
S
Y
Y
Y
Y
N
Y
N
N
N
STABLE
151
S
N
Y
Y
Y
N
Y
N
N
N 4.62E+18 Pm-147
α
100
152
S
N
Y
Y
Y
N
Y
N
N
N 1.35E+01 Sm-152 EC/β−
S
N
Y
Y
Y
N
Y
N
N
N 1.35E+01 Gd-152
153
S
Y
Y
Y
Y
N
N
N
N
N
154
S
N
Y
Y
Y
N
Y
N
N
154
S
N
Y
Y
Y
N
Y
N
155
S
N
Y
Y
Y
N
Y
152
S
N
Y
Y
Y
Y
154
S
Y
Y
Y
Y
155
S
Y
Y
Y
156
S
Y
Y
157
S
Y
158
S
160
72.4
β−
27.6
N 8.59E+00 Gd-154
β−
100
N
N 8.59E+00 Sm-154
EC
>0.1
N
N
N 4.76E+00 Gd-155
β−
100
Y
N
N
N 1.08E+14 Sm-148
α
100
Y
N
N
N
N
STABLE
Y
Y
N
N
N
N
STABLE
Y
Y
Y
N
N
N
N
STABLE
Y
Y
Y
Y
N
N
N
N
STABLE
Y
Y
Y
Y
Y
N
N
N
N
STABLE
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
161
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
162
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
163
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
164
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
STABLE
109
67
Ho
Holmium
165
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
68
Er
Erbium
166
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
167
S
Y
Y
Y
Y
Y
N
N
N
N
STABLE
72
Hf
Hafnium
186
S
N
N
N
Y
Y
Y
N
N
N 4.95E-06 Ta-186
β−
73
Ta
Tantalum
186
S
N
Y
Y
N
Y
Y
N
N
N 2.00E-05 W-186
β−
74
W
Tungsten
186
S
Y
N
Y
Y
Y
N
N
N
N
STABLE
80
Hg
Mercury
204
S
Y
Y
N
N
Y
N
N
N
N
STABLE
205
S
N
Y
N
N
Y
Y
N
N
N 9.78E-06 Tl-205
β−
100
206
S
N
Y
N
N
Y
Y
N
N
N 1.55E-05 Hg-205
β−
100
205
S
Y
Y
Y
Y
Y
N
N
N
N
206
S
N
Y
Y
Y
Y
Y
N
N
N 7.99E-06 Pb-206
β−
100
207
S
N
Y
Y
Y
Y
Y
N
N
N 9.08E-06 Pb-207
β−
100
209
S
N
Y
Y
Y
Y
Y
N
N
N 4.11E-06 Pb-209
β−
206
S
Y
N
N
Y
Y
N
N
N
N
STABLE
207
S
Y
N
N
Y
Y
N
N
N
N
STABLE
208
S
Y
N
N
Y
Y
N
N
N
N
STABLE
209
S
N
N
N
Y
Y
Y
N
N
N 3.71E-04 Bi-209
β−
100
210
S
N
N
N
Y
Y
Y
N
N
N 2.22E+01 Bi-210
β−
100
S
N
N
N
Y
Y
Y
N
N
N 2.22E+01 Hg-206
α
>0.1
211
S
N
N
N
Y
Y
Y
N
N
N 6.87E-05 Bi-211
β−
100
212
S
N
N
N
Y
Y
Y
N
N
N 1.21E-03 Bi-212
β−
100
209
S
Y
N
N
N
N
Y*
N
N
N 1.90E+19 Tl-205
α
100
210
S
N
N
N
N
N
Y
N
N
N 1.37E-02 Po-210
β−
S
N
N
N
N
N
Y
N
N
N 1.37E-02 Tl-206
α
>0.1
S
N
N
N
N
N
Y
N
N
N 4.07E-06 Tl-207
α
99.7
S
N
N
N
N
N
Y
N
N
N 4.07E-06 Po-211
β−
0.3
S
N
N
N
N
N
Y
N
N
N 1.15E-04 Po-212
β−
64.1
S
N
N
N
N
N
Y
N
N
N 1.15E-04 Tl-207
α
35.9
S
N
N
N
N
N
Y
N
N
N 1.15E-04 Po-211
β−
>0.1
S
Y
N
N
N
N
Y
N
N
N 8.67E-05 Po-213
β−
97.9
S
Y
N
N
N
N
Y
N
N
N 8.67E-05 Tl-209
α
2.1
215
S
N
N
N
N
N
Y
N
N
N 1.45E-05 Po-215
β−
100
210
S
Y
Y
N
N
Y
Y
N
N
N 3.79E-01 Pb-206
α
100
211
S
N
Y
N
N
Y
Y
N
N
N 1.64E-08 Pb-207
α
100
212
S
N
Y
N
N
Y
Y
N
N
N 9.48E-15 Pb-208
α
100
213
S
N
Y
N
N
Y
Y
N
N
N 1.16E-13 Pb-209
α
214
S
N
Y
N
N
Y
Y
N
N
N 5.21E-12 Pb-210
α
215
S
N
Y
N
N
Y
Y
N
N
N 5.65E-11 Pb-211
α
100
S
N
Y
N
N
Y
Y
N
N
N 5.65E-11 At-215
β−
>0.1
S
N
Y
N
N
Y
Y
N
N
N 4.60E-09 Pb-212
α
81
82
83
Tl
Pb
Bi
Thallium
Lead
Bismuth
211
212
213
84
Po
Polonium
216
STABLE
110
85
At
Astatine
S
N
Y
N
N
Y
Y
N
N
N 4.60E-09 Rn-216
β−
>0.1
215
S
N
N
N
N
Y
Y
N
N
N 3.17E-12 Bi-211
α
100
217
S
N
N
N
N
Y
Y
N
N
N 1.02E-09 Bi-213
α
100
S
N
N
N
N
Y
Y
N
N
N 1.02E-09 Rn-217
β−
>0.1
S
N
N
N
N
Y
Y
N
N
N 1.78E-06 Bi-215
α
97
S
N
N
N
N
Y
Y
N
N
N 1.78E-06 Rn-219
β−
3
216
G
N
Y
N
N
Y
Y
N
N
N 1.43E-12 Po-211
α
217
G
N
Y
N
N
Y
Y
N
N
N 1.71E-11 Po-213
α
218
G
N
Y
N
N
Y
Y
N
N
N 1.11E-09 Po-214
α
219
G
N
Y
N
N
Y
Y
N
N
N 1.26E-07 Po-215
α
220
G
N
Y
N
N
Y
Y
N
N
N 1.76E-06 Po-216
α
G
N
Y
N
N
Y
Y
N
N
N 1.76E-06 Ra-220
β−
>0.1
S
N
Y
N
Y
Y
Y
N
N
N 9.32E-06 At-217
α
99.9
S
N
Y
N
Y
Y
Y
N
N
N 9.32E-06 Ra-221
β−
0.1
S
N
Y
N
Y
Y
Y
N
N
N 9.32E-06 Tl-207
CD
>0.1
S
N
Y
N
Y
Y
Y
N
N
N 9.32E-06
S
N
Y
N
Y
Y
Y
N
N
N 4.19E-05 Ra-223
β−
100
S
N
Y
N
Y
Y
Y
N
N
N 4.19E-05 At-219
α
>0.1
220
S
N
Y
N
N
Y
Y
N
N
N 5.68E-10 Rn-216
α
100
221
S
N
Y
N
N
Y
Y
N
N
N 8.88E-07 Rn-217
α
S
N
Y
N
N
Y
Y
N
N
N 8.88E-07 Pb-207
CD
S
N
Y
N
N
Y
Y
N
N
N 8.88E-07
S
N
Y
N
N
Y
Y
N
N
N 1.21E-06 Rn-218
α
S
N
Y
N
N
Y
Y
N
N
N 1.21E-06 Pb-208
CD
S
N
Y
N
N
Y
Y
N
N
N 1.21E-06
S
Y
Y
N
N
Y
Y
N
N
N 3.13E-02 Pb-209
S
Y
Y
N
N
Y
Y
N
N
N 3.13E-02
S
N
Y
N
N
Y
Y
N
N
N 9.95E-03 Rn-220
α
S
N
Y
N
N
Y
Y
N
N
N 9.95E-03 Pb-210
CD
S
N
Y
N
N
Y
Y
N
N
N 9.95E-03
225
S
N
Y
N
N
Y
Y
N
N
N 4.08E-02 Ac-225
α
226
S
N
Y
N
N
Y
Y
N
N
N 1.60E+03 Rn-220
α
S
N
Y
N
N
Y
Y
N
N
N 1.60E+03 Th-226 β−β−
S
N
Y
N
N
Y
Y
N
N
N 1.60E+03 Pb-212
S
N
Y
N
N
Y
Y
N
N
N 1.60E+03
227
S
N
Y
N
N
Y
Y
N
N
N 8.03E-05 Ac-227
β−
225
S
N
Y
N
N
Y
Y
N
N
N 2.74E-02 Fr-221
α
S
N
Y
N
N
Y
Y
N
N
N 2.74E-02 Bi-211
CD
>0.1
S
N
Y
N
N
Y
Y
N
N
N 2.74E-02
S
Y
Y
N
N
Y
Y
N
N
N 2.18E+01 Th-227
β−
98.6
219
86
87
Rn
Fr
Radon
Francium
221
223
88
Ra
Radium
222
223
224
89
Ac
Actinium
227
100
C-14
>0.1
C-14
>0.1
C-14
C-14
α
CD
>0.1
>0.1
C-14
CD
>0.1
C-14
C-14
111
90
Th
Thorium
S
Y
Y
N
N
Y
Y
N
N
N 2.18E+01 Fr-223
α
226
S
N
Y
N
Y
Y
Y
N
N
N 5.82E-05 Ra-222
α
227
S
N
Y
N
Y
Y
Y
N
N
N 5.12E-02 Ra-223
α
228
S
N
Y
N
Y
Y
Y
N
N
N 1.91E+00 Ra-224
α
S
N
Y
N
Y
Y
Y
N
N
N 1.91E+00 Pb-208
CD
S
N
Y
N
Y
Y
Y
N
N
N 1.91E+00 O-20
229
S
N
Y
N
Y
Y
Y
N
N
N 7.34E+03 Ra-225
α
230
S
N
Y
N
Y
Y
Y
N
N
N 7.54E+04 Hg-206
CD
S
N
Y
N
Y
Y
Y
N
N
N 7.54E+04 Ne-24
S
N
Y
N
Y
Y
Y
N
N
N 7.54E+04 Ra-226
α
S
N
Y
N
Y
Y
Y
N
N
N 7.54E+04 Various
SF
S
N
Y
N
Y
Y
Y
N
N
N 2.91E-03 Pa-231
β−
S
N
Y
N
Y
Y
Y
N
N
N 2.91E-03 Ra-227
α
234
S
N
Y
N
Y
Y
Y
N
N
N 6.60E-02 Pa-234
β−
231
S
N
Y
N
N
Y
Y
N
N
N 3.28E+04 Ac-227
α
S
N
Y
N
N
Y
Y
N
N
N 3.28E+04 Ti-207
CD
>0.1
S
N
Y
N
N
Y
Y
N
N
N 3.28E+04 Ne-24
S
N
Y
N
N
Y
Y
N
N
N 3.28E+04 Pb-208
CD
>0.1
S
N
Y
N
N
Y
Y
N
N
N 3.28E+04
233
S
N
Y
N
N
Y
Y
N
N
N 7.39E-02 U-233
β−
234
S
N
Y
N
N
Y
Y
N
N
N 7.65E-04 U-234
β−
S
N
Y
N
N
Y
Y
N
N
N 7.65E-04 Various
SF
S
N
Y
N
Y
Y
Y
N
Y
N 6.89E+01 Th-228
α
S
N
Y
N
Y
Y
Y
N
Y
N 6.89E+01 Pb-208
CD
>0.1
S
N
Y
N
Y
Y
Y
N
Y
N 6.89E+01 Ne-24
S
N
Y
N
Y
Y
Y
N
Y
N 6.89E+01 Hg-204
CD
>0.1
S
N
Y
N
Y
Y
Y
N
Y
N 6.89E+01 Mg-28
S
Y
Y
N
Y
Y
Y
Y
Y
N 1.59E+05 Th-229
S
Y
Y
N
Y
Y
Y
Y
Y
N 1.59E+05 Pb-209
CD
>0.1
S
Y
Y
N
Y
Y
Y
Y
Y
N 1.59E+05 Ne-24
S
Y
Y
N
Y
Y
Y
Y
Y
N 1.59E+05 Hg-205
CD
>0.1
S
Y
Y
N
Y
Y
Y
Y
Y
N 1.59E+05 Mg-28
S
Y
Y
N
Y
Y
Y
Y
Y
N 1.59E+05 Various
SF
>0.1
S
N
Y
N
Y
Y
Y
N
Y
N 2.46E+05 Th-230
α
S
N
Y
N
Y
Y
Y
N
Y
N 2.46E+05 Hg-206
CD
>0.1
S
N
Y
N
Y
Y
Y
N
Y
N 2.46E+05 Mg-28
S
N
Y
N
Y
Y
Y
N
Y
N 2.46E+05 Hf-184
CD
>0.1
S
N
Y
N
Y
Y
Y
N
Y
N 2.46E+05 Ne-26
S
N
Y
N
Y
Y
Y
N
Y
N 2.46E+05 Ne-24
S
N
Y
N
Y
Y
Y
N
Y
N 2.46E+05 Various
SF
>0.1
231
91
92
Pa Protactinium
U
Uranium
232
233
234
1.4
100
>0.1
>0.1
>0.1
>0.1
F-23
>0.1
112
S
Y
Y
N
Y
Y
Y
Y
Y
Y 7.04E+08 Th-231
α
S
Y
Y
N
Y
Y
Y
Y
Y
Y 7.04E+08 Hf-186
CD
>0.1
S
Y
Y
N
Y
Y
Y
Y
Y
Y 7.04E+08 Ne-25
S
Y
Y
N
Y
Y
Y
Y
Y
Y 7.04E+08 Ne-24
S
Y
Y
N
Y
Y
Y
Y
Y
Y 7.04E+08 Various
SF
>0.1
S
N
Y
N
Y
Y
Y
N
Y
N 2.34E+07 Th-232
α
S
N
Y
N
Y
Y
Y
N
Y
N 2.34E+07 Various
SF
>0.1
237
S
N
Y
N
Y
Y
Y
N
Y
N 1.85E-02 Np-237
β−
100
238
S
N
Y
N
Y
Y
Y
N
Y
N 4.47E+09 Th-234
α
S
N
Y
N
Y
Y
Y
N
Y
N 4.47E+09 Pu-238
CD
>0.1
S
N
Y
N
Y
Y
Y
N
Y
N 4.47E+09 Various
SF
>0.1
239
S
N
Y
N
Y
Y
Y
N
Y
N 4.46E-05 Np-239
β−
237
S
N
Y
N
Y
Y
Y
Y
Y
Y 2.14E+06 Mg-30
CD
S
N
Y
N
Y
Y
Y
Y
Y
Y 2.14E+06 Tl-207
S
N
Y
N
Y
Y
Y
Y
Y
Y 2.14E+06 Pa-233
α
S
N
Y
N
Y
Y
Y
Y
Y
Y 2.14E+06 Various
SF
238
S
N
Y
N
Y
Y
Y
N
Y
N 5.80E-03 Pu-238
β−
239
S
N
Y
N
Y
Y
Y
N
Y
N 6.45E-03 Pu-239
β−
240
S
N
Y
N
Y
Y
Y
N
Y
N 1.18E-04 Pu-240
β−
238
S
Y
Y
Y
Y
Y
Y
N
Y
N 8.77E+01 U-234
α
S
Y
Y
Y
Y
Y
Y
N
Y
N 8.77E+01 Hg-206
CD
>0.1
S
Y
Y
Y
Y
Y
Y
N
Y
N 8.77E+01 Si-32
S
Y
Y
Y
Y
Y
Y
N
Y
N 8.77E+01 Yb-180
CD
>0.1
S
Y
Y
Y
Y
Y
Y
N
Y
N 8.77E+01 Mg-30
S
Y
Y
Y
Y
Y
Y
N
Y
N 8.77E+01 Mg-28
S
Y
Y
Y
Y
Y
Y
N
Y
N 8.77E+01 Various
SF
>0.1
S
N
Y
Y
Y
Y
Y
Y
Y
Y 2.41E+04 U-235
α
S
N
Y
Y
Y
Y
Y
Y
Y
Y 2.41E+04 Various
SF
S
N
Y
Y
Y
Y
Y
N
Y
N 6.56E+03 U-236
α
S
N
Y
Y
Y
Y
Y
N
Y
N 6.56E+03 Hg-206
CD
>0.1
S
N
Y
Y
Y
Y
Y
N
Y
N 6.56E+03 Si-34
S
N
Y
Y
Y
Y
Y
N
Y
N 6.56E+03 Various
SF
>0.1
S
N
Y
Y
Y
Y
Y
Y
Y
N 1.43E+01 AM-241
β−
100
S
N
Y
Y
Y
Y
Y
Y
Y
N 1.43E+01 U-237
α
>0.1
S
N
Y
Y
Y
Y
Y
Y
Y
N 1.43E+01 Various
SF
>0.1
S
N
Y
Y
Y
Y
Y
N
Y
N 3.75E+05 U-238
α
S
N
Y
Y
Y
Y
Y
N
Y
N 3.75E+05 Various
SF
235
236
93
94
Np
Pu
Neptunium
Plutonium
239
240
241
242
>0.1
>0.1
>0.1
>0.1
113
9.3) Fission Product Yields [By Fissile Isotope]
Fission product yield tables have been color-coded for quick-reference.
Color codes are:
≤90 Day to >100
Gaseous
Stable Solid
Fissile
>90 Day Decay
Lifetime Storage
Year Decay
Figure 6 - Color Codes for Fission Product Distribution Figures
114
Uranium-233 [233U]
20%
18%
16%
14%
12%
10%
8%
6%
4%
2%
0%
36
42
43
44
45
46
47
48
49
51
52
54
55
60
61
62
63
64
66
67
68
91
92
Percentage of Waste Mass
9.3.a)
Atomic Number
Figure 7 - Uranium-233 [233U] Fission Product Distribution, by Element
115
9.3.b)
Uranium-235 [235U]
Percentage of Waste Mass
18%
16%
14%
12%
10%
8%
6%
4%
2%
36
42
43
44
45
46
47
48
49
51
52
54
55
60
61
62
63
64
66
67
68
91
92
0%
Atomic Number
Figure 8 - Uranium-235 [235U] Fission Product Distribution, by Element
116
Plutonium-239 [239Pu]
20%
18%
16%
14%
12%
10%
8%
6%
4%
2%
0%
36
42
43
44
45
46
47
48
49
51
52
54
55
60
61
62
63
64
66
67
68
91
92
Percentage of Waste Mass
9.3.c)
Atomic Number
Figure 9 - Plutonium-239 [239Pu] Fission Product Distribution, by Element
117
Plutonium-241 [241Pu]
20%
18%
16%
14%
12%
10%
8%
6%
4%
2%
0%
36
42
43
44
45
46
47
48
49
51
52
54
55
60
61
62
63
64
66
67
68
91
92
Percentage of Waste Mass
9.3.d)
Atomic Number
Figure 10 - Plutonium-241 [241Pu] Fission Product Distribution, by Element
118
