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OCR for page 141
6
Long-Term Disposition
INTRODUCTION
Long-term disposition of the excess plutonium from dismantled nuclear
weapons the third stage in the process beginning with dismantlement of
weapons and intermediate storage of fissile materials will be a long, complex,
and expensive endeavor.
· All of the plausible options stretch out over decades, counting both the time
required to get ready to begin and the time needed to complete the disposi-
tion campaign.
· All options are likely to involve a net economic cost, rather than providing a
net profit from this material.
· All options involve unresolved issues and risks of uncertain magnitude.
· None of the options is sufficiently developed to be chosen as the preferred
approach until outstanding questions are answered.
This chapter offers not a final answer but a road map for arriving at one; it
is intended to provide guidelines for the necessary national and international
debate to come, to narrow the focus of attention to the subset of options most
likely to minimize risks, and to provide plausible end points for the dismantle-
ment and storage activities now under way.
141
OCR for page 142
142 LONG-TERM DISPOSITION
In considering this situation, the committee has reached the following set
of recommendations:
· Because of the long times required for all disposition options, Missile ma-
terial storage arrangements lasting well over a decade will be an essential part
of any disposition policy (see Chapter 5~. These storage arrangements should be
designed to meet the same stringent standards of security and accountability
applied to stored weapons, and they should include international monitoring.
Because of the uncertainties surrounding all disposition options, these inter-
mediate storage approaches must be designed to be capable of extension for
many decades if necessary. The appropriate arrangements for intermediate
storage are to a large extent decoupled from long-term disposition decisions
and are currently more urgent.
· Storage should not be extended indefinitely. Because of the liabilities of
indefinite storage of excess weapons material for the nonproliferation and arms
reduction regimes, the risk of breakout involved in such storage, and the risks
of theft in the event of a breakdown in government authority, there are sub-
stantial reasons to pursue other disposition approaches that provide additional
barriers against use of this material in weapons. Indeed, one of the key criteria
by which disposition options should be judged is the speed with which they can
be accomplished, and thus the degree to which they curtail the risks of pro-
longed storage.
· Disposition options other than extended storage should be pursued only if
they reduce overall security risks compared to leaving the material in storage,
when both the final form of the material and the risks of the various processes
needed to get to that state are considered. In the current unsettled circumstances
in Russia, this minimum criterion is not trivial.
· To the extent practicable, safeguards and security measures should main-
tain the "stored weapons standard" of accounting and security throughout the
disposition process. The process must take place under agreed monitoring and
security that form part of the overall regime for management of fissile materials
described in previous chapters.
.
· An appropriate standard for the ilna1 product or clsposltlon options IS
that they transform the weapons plutonium into a physical form that is at least
as inaccessible for weapons use as the much larger and growing stock of pluto-
nium that exists in spent fuel from commercial nuclear reactors. (This existing
problem will itself change over time as the radioactivity decays, repositories or
monitored retrievable storage sites become available, and approaches to safe-
guards and security and nuclear fuel cycles evolve.) Incurring substantial addi-
tional costs, complexities, risks, or delays in order to go further and eliminate
the excess weapons plutonium completely or nearly so would not be justified
OCR for page 143
LONG-TERM DISPOSITION 143
unless the same approach were to be taken with the global stock of civilian
plutonium.
· The two most promising alternatives for the purpose of meeting the spent
fuel standard are:
1. The spent fuel option, which has several variants. The principal one is
to use the plutonium as once-through fuel in existing civilian nuclear power
reactors or their evolutionary variants. Candidates for this role are U.S. light-
water reactors (LWRs), Russian LWRs, and Canadian deuterium-uranium
(CANDU) reactors. The use of European and Japanese reactors already licensed
for civilian plutonium should also be considered for Russian weapons
plutonium.
2. The vitrification option, which would entail combining the plutonium
with radioactive high-level wastes as these are melted into large glass logs. The
plutonium would then be roughly as difficult to recover for weapons use as plu-
tonium in spent fuel.
A third option, burial in deep boreholes, has until now been less thor-
oughly studied than options 1 and 2, but could turn out to be comparably
attractive.
Further research is needed to answer important outstanding questions concern-
ing each of these three options.
· For the spent fuel option, existing or partly completed reactors are pre-
ferred over newly built reactors, to avoid the delay and capital cost of building
entirely new facilities. If problems of licensing and public approval for existing
reactors prove insurmountable, one or more new reactors might be built on a
government-owned site; if so, these should be reactors of sufficiently well-
proven design so as not to create additional technical and licensing uncertain-
ties. Reactors of more advanced design examined by the committee do not offer
sufficient advantages for this mission to offset the delays and extra costs their
use would entail.
· Although the spent fuel standard applied to excess plutonium is an ap-
propriate goal for next steps, further steps should be taken to reduce the prolif-
eration risks associated with nuclear power and the global stock of plutonium,
including plutonium in spent fuel. Options for near-total elimination of pluto-
nium may have a role to play in the longer-term effort to reduce the risks posed
by global plutonium stocks. Research on defining and exploring these options
should be continued at the conceptual level.
' The spent fuel option, in which the weapons plutonium would actually be converted to spent
fuel, should not be confused with the spent fuel standard: it is merely one means of meeting that
standard. As discussed later, spent plutonium fuels would have some differences from ordinary spent
fuels, including higher plutonium concentrations.
OCR for page 144
144 LONG-TERM DISPOSITION
· Institutional issues in managing plutonium disposition may be more
complex and difficult to resolve than the technical ones. The process must be
carefully managed to provide adequate safeguards, security, transparency, and
protection for environment, safety, and health; to obtain public and institutional
approval, including licenses; and to allow adequate participation in the decision
making by all affected parties, including the U.S. and Russian publics and the
international community. Adequate information must be made available to give
substance to the public's participation. A more effective decision making proc-
ess to address these issues is needed within both the U.S. and the Russian gov-
ernments, as discussed in Chapter 1.
· It is important to begin now to build consensus on a road map for deci-
sions concerning long-term disposition of excess weapons plutonium. Because
disposition options will take decades to carry out, it is critical to develop op-
tions that can muster a sustainable consensus.
The remainder of this chapter outlines the considerations that led to these
conclusions. It begins by describing the categories into which the many techni-
cal options for long-ten disposition can be divided and the criteria for judging
among them. It then goes on to discuss each option and how it fares under
those criteria. Finally, it outlines the committee's recommendations.
THE RANGE OF CHOICE
The options for long-term disposition can be divided into three broad
classes, as illustrated in Figure 6-1:
1. Indefinite Storage: In this approach, the plutonium would continue to
be stored in directly weapons-usable form indefinitely, with no specific decision
concerning whether, when, and how storage would be terminated.2 During
such storage, safeguards and security would provide the primary barrier to pro-
liferation. Political measures, such as a formal commitment to non-weapons use
and continuing safeguards, would provide the primary barrier to reuse of the
material for weapons by the state from whose weapons the material came. Al-
though intermediate storage is essential to all disposition options, for reasons
already mentioned the committee does not recommend that it be extended in-
definitely.
2. Minimized Accessibility: In this concept, barriers would be created
physical, chemical, or radiological to make the steps needed to use the pluto-
nium in weapons (acquisition of the plutonium, processing, weapon manufac-
ture) more difficult either for potential proliferators or for the state from whose
2In separating "indefinite" storage from "inte~ediate" storage, this report uses "indefinite" to
mean approaches in which storage itself is considered the disposition option, and no end point to the
storage has been defined. In this nomenclature, storage would be considered "intermediate" even if it
lasted for several decades, if the material were awaiting processing in a chosen disposition option.
OCR for page 145
LONG-TERM DISPOSITION 145
Indefinite
Storage
~ Materials Remain in Weapons
/ Usable Form Barriers to Reuse
/ in Weapons Based on Politics and
Secutity Measures
Intermediate
Storage
FIGURE 6-1 Plutonium disposition
Minimized
Accessibility
Physical, Chemical, or
Radialogical, Barriers Reduce
Availability for Weapons Use
Elimination ~
Material Nearly \
Completely Removed from \
Human Access \
OPTIONS
Use
Reactors (no reprocessing
JO required)
/ LWR, CANDU, LMR,
MHTGR, etc.
Disposal
Vitrification
Deep Borehole
Underground Explosion
Sub-Seabed
Repository Burial
Use
Reactors (reprocessing
required)
LWR, CANDU,
LMR, MHTGR, etc.
An Disposal
Space Launch
Ocean Dilution
weapons it came. The plutonium would continue to exist, and some form of
safeguards would continue to be required. The spent fuel, vitrification, and
deep-borehole approaches are examples.
3. Elimination: In this concept, the plutonium would be removed from hu-
man access completely, or nearly so, for example, by fissioning the plutonium
atoms or by launching it into deep space. The point in such a process at which
the plutonium can be considered "eliminated" for example, whether burning
99 percent of the plutonium would be sufficient- is somewhat arbitrary, but
any "elimination" option should ensure that retrieving enough plutonium for a
nuclear explosive from whatever remains would be extremely difficult. One
plausible standard is to describe any option in which only a few grams of plu-
tonium would remain in a large truckload of waste as an elimination option.3
3 The International Atomic Energy Agency (IAEA), for example, considers that materials no
longer require safeguards if the remaining fissile material in them has been "consumed," or so diluted as
to be "practically irrecoverable" for weapons use. Quantitative measures for termination of safeguards,
which might provide one standard for judging when to consider fissile material "eliminated," have not
yet been finalized. Interview with Thomas Shea, IAEA Safeguards Division, August 1993. See, for
example, A. Fattah and N. Khlebnikov, "A Proposal for Technical Criteria for Termination of
OCR for page 146
146 LONG-TERM DISPOSITION
Use or Disposal. A complementary categorization is whether the pluto-
nium would be used or disposed of. The use options would fission some frac-
tion of the plutonium in power reactors, converting its energy content into elec-
tricity. The disposal options would throw away the plutonium's energy content.
Since plutonium is more expensive to use as nuclear fuel than widely available
low-enriched uranium, either the use or the disposal options would require a
subsidy. The different signals relating to civilian nuclear power that would be
sent by using excess plutonium or throwing it away are discussed in more detail
below.
U.S. and Russian Contexts. It is possible-even likely that the optimal
approaches to long-term plutonium disposition will be different in the United
States and Russia. The risks involved in storing, handling, processing, and
transporting plutonium are much higher in Russia under present circumstances,
and the two countries' economies and plutonium fuel policies are different.
Most of the key officials responsible for these issues in the Russian government
strongly prefer options that use surplus weapons plutonium to generate electric-
ity in reactors; it would be difficult to convince Russia to pursue disposal op-
tions in the near term (though perhaps not impossible, particularly with suf-
ficient financial incentives).
Although U.S. and Russian disposition approaches may differ, rough paral-
lelism in the timing and scale of long-term disposition would be desirable, so
that both nations' available plutonium stocks would remain comparable. After
long-term disposition, neither nation's excess plutonium should be much more
accessible for use in weapons than the other' s.
While the United States and other industrialized countries cannot dictate
particular disposition options to Russia, they will have a significant influence
on Russian decisions in a variety of ways ranging from simply setting an ex-
ample on the one hand, to financial assistance, negotiated agreements to pursue
particular approaches, or outright purchase of former Soviet weapons pluto-
nium on the other.
Other Forms of Military Plutonium. The primary focus of this report is the
excess weapons plutonium resulting from arms reductions, which is initially in
the form of pits from dismantled nuclear weapons. Both the United States and
Russia, however, also have large quantities of military plutonium in scrap and
residues from past operations of their nuclear weapons complexes, most of
which are also likely to be considered excess. Although the amount of pluto-
nium in these forms is smaller than the amount in pits that will result from
arms reductions, the volume is much greater; the variety of forms of material is
wide; and the environment, safety, and health (ES&H) risks are substantial for
Safeguards for Materials Characterized as Measured Discards," Journal of Nuclear Materials
Management, May 1991.
OCR for page 147
LONG-TERM DISPOSITION 147
some forms. Even characterizing the constituents of these materials accurately
is difficult.
Some of these materials can readily be processed to plutonium metal or
oxide that could then be fed into many of the disposition options described be-
low. Some reactor options (typically the more advanced ones that would take
longer to bring on-line) are more capable than others of handling variations in
the form of the initial fuel feed, though there are materials that none of the re-
actor options could plausibly handle. Moreover, processing of some of these
materials would raise difficult environmental issues of its own. The vitrification
option, described below, may be a particularly promising approach for stabiliz-
ing and ultimately disposing of the plutonium in these less tractable forms.
CRITERIA FOR DISPOSITION OPTIONS
Security issues should be the primary criteria for choice among the
long-term disposition options. Each long-term disposition approach generates
risks and opportunities with respect to theft, rearmament, and the arms reduc-
tion and nonproliferation regimes that depend on political and technical factors
that will evolve over the long time periods involved in disposition. The commit-
tee judges the following security risks related to long-term disposition choices
to be of greatest concern:
Risks of Storage: Prolonged storage of excess weapons plutonium would
mean a continuing risk of breakout, as well as of theft from the storage site. In
addition, extended storage of large quantities of excess fissile materials, par-
ticularly in the form of weapons components, could undermine the arms reduc-
tion and nonproliferation regimes. Thus, long-term disposition options should
minimize the time during which plutonium is stored in accessible forms. The
timing for each long-term disposition option is dependent on three factors: its
technical readiness or uncertainty, the speed with which public and institutional
approval could be gained, and the time required to implement it once developed
and approved.
Risks of Handling: Nearly all disposition options other than indefinite stor-
age require processing and usually transportation of plutonium, in ways that
could increase access to the material and complicate accounting for it, thus in-
creasing the potential for diversion and theft. In order to ensure that the overall
process reduces net security risks, an agreed and stringent standard of security
and accounting must be maintained throughout the disposition process, ap-
proximating as closely as practicable the security and accounting applied to
intact nuclear weapons. The committee calls this the "stored weapons stan-
dard." Hence, choices among long-ten disposition options should be weighted
in favor of those that minimize:
OCR for page 148
148 LONG-TERM DISPOSITION
· the number of transport steps, and the risks involved in each;
· the number of sites at which plutonium is handled, and the risks at each
of those sites; and
· any processing steps with high accessibility and low accountability.
Risks of Recovery: A third key security criterion for judging disposition
options is the risk of recovery of the plutonium after disposition. The committee
believes that options for the long-term disposition of weapons plutonium should
seek to meet a "spent fuel standard" that is, to make this plutonium roughly
as inaccessible for weapons use as the much larger and growing quantity of
plutonium that exists in spent fuel from commercial reactors. Options that left
the plutonium more accessible than this existing stock would mean that this
material would continue to pose a unique safeguards problem indefinitely.
Conversely, as long as civilian plutonium exists and continues to accumulate,
options that went further than the spent fuel standard and sought to eliminate
the excess weapons plutonium entirely would provide little additional security,
unless the same were done with the much larger amount of civilian plutonium.
Thus, options for the next steps in long-term disposition of weapons plutonium
shouldfocus on those in the "minimized accessibility" class.
Over the longer term, however, steps should be taken to go beyond the cur-
rent spent fuel standard, to further reduce the accessibility for use in weapons of
the entire global stock of plutonium. Elimination options are among the pos-
sibilities for this purpose and could be seen as a second, long-term step for all
plutonium (both military and civilian).
The difficulty of using plutonium in spent fuel for nuclear explosives arises
from its chemical dilution in the fuel (with plutonium typically consisting of
roughly 1 percent of the spent fuel weight); the radioactivity of the fission
products with which the plutonium is mixed (which, for years after the fuel
leaves the reactor, would give anyone attempting to the handle the spent fuel
without appropriate protection a lethal dose of radiation within minutes); and
the isotopic composition of the plutonium (which includes more of the less de-
sirable isotopes of plutonium than weapons-grade material does, somewhat
complicating the construction of nuclear explosives). (See "How Accessible is
Plutonium in Spent Fuel?" p. 150.) Eventually, physical barriers will be im-
posed as well, when this material is consigned to geologic repositories; these
physical barriers will have to compensate for the long-term decline of the radio-
logical barrier.
Chemical barriers alone, such as diluting the plutonium or combining it
chemically with other elements, will not be sufficient to match this combination
of chemical, radiological, and isotopic barriers, and therefore cannot meet the
spent fuel standard. Thus, the leading options the committee has examined in-
volve both chemical and radiological barriers (in the case of the spent fuel and
vitrification options) or substantial physical barriers (in the case of the
deep-borehole option).
OCR for page 149
LONG-TERM DISPOSITION 149
The three security criteria just outlined represent a kind of coarse filter for
disposition options: any option that cannot bring the weapons plutonium to the
spent fuel standard within a few decades with low to moderate security risks
along the way does not deserve further consideration.
Signals Relating to Civilian Nuclear Fuel Cycles. The goal of long-term
disposition should be not only to ensure that the plutonium from dismantled
weapons is not reused in weapons, but also to reduce net security risks from all
fissile materials. Thus, policymakers must be attentive to possible indirect ef-
fects that the choice of disposition options might have on the proliferation risks
posed by other fissile materials in the world, as well as its direct effects on the
surplus weapons material. The political signals sent by the choice of particular
disposition approaches might encourage the development and use of more pro-
liferation-resistant nuclear fuel cycles; encourage the use of more proliferation-
prone nuclear fuel cycles; or serve to set a standard for improved safeguards
and security for other fissile materials.
Under the Carter administration, the United States decided not to reprocess
civilian plutonium or pursue plutonium fuel cycles, and launched a major in-
ternational effort to convince other countries that' such separated plutonium fuel
cycles were uneconomical and posed significant proliferation risks. Elements of
that policy were incorporated in the Nuclear Non-Proliferation Act of 1978,
which remains U.S. law. Although the Reagan and Bush administrations re-
versed the Carter administration's opposition to domestic use of separated plu-
tonium, for economic reasons none 'has ensued. Both of these administrations
continued to strongly oppose plutonium separation in countries judged to pose
proliferation risks, while raising no objections to continuing plutonium separa-
tion programs in Japan and Europe. On September 27, 1993, the Clinton ad-
ministration announced a nonproliferation initiative that makes clear that,
while the United States will not interfere with reprocessing in Japan and
Europe, "the United States does not encourage the civil use of plutonium and,
accordingly, does not itself engage in plutonium reprocessing for either nuclear
power or nuclear explosive purposes." The initiative called for an exploration
of "means to limit the stockpiling of plutonium from civil nuclear programs."4
Given this background, policymakers will have to take into account the fact
that choosing to use weapons plutonium in reactors would be perceived by some
as representing generalized U.S. approval of separated plutonium fuel cycles,
thereby compromising the ability of the U.S. government to oppose such fuel
cycles elsewhere. Conversely, choosing to dispose of weapons plutonium with-
out extracting any energy from it could be interpreted as reflecting a general-
ized U.S. government opposition to plutonium recycle. Either choice could have
an impact on fuel cycle debates now under way in Japan, Europe, and Russia.
4 White House Fact Sheet, "Nonproliferation and Export Control Policy," September 27, 1993.
OCR for page 150
150 LONG-TERM DISPOSITION
OCR for page 151
LONG-TEAM DISPOSITION 151
OCR for page 212
212 LONG-TERM DISPOSITION
Accelerator-based Conversion (ABC). Accelerator-based conversion
(ABC) systems have been under study as a means of eliminating plutonium,
and of fissioning actinides and transmuting fission products in order to reduce
the longevity of radioactive wastes. In this concept, a reactor that was subcriti-
cal meaning that the neutrons within it could not sustain a chain reaction
without outside input is driven by neutrons produced by a beam of particles
from an accelerator hitting a target. In the concepts that have received most
examination, the subcritical reactor would have a fluid fuel (either an aqueous
slurry or a molten salt) that would be fed continuously out of the reactor, re-
processed to remove fission products, and fed back into the reactor.47
This option is only at the early paper-study stage and cannot be available
on a large scale for decades. Both the proposed subcritical fluid fuel reactor
technology and its fuel cycle technology are extremely challenging and un-
proven. The reactor, for example, would have a radiation flux of order 10 times
that in current LWRs, raising serious engineering issues concerning the sur-
vival of the reactor materials. Reprocessing would take place within days or
weeks after the fuel left the reactor, forcing the approach to deal with unprece-
dented levels of radioactivity; at the same time, proponents claim that reproc-
essing losses would be unprecedentedly low. If the estimated performance could
be attained, however, such systems could destroy plutonium at a rate (per unit
of thermal energy) comparable to those of the other destruction-oriented options
and could reach high reduction factors for plutonium inventory more rapidly
than many of the other options.
The continuous on-line reprocessing proposed for ABC would offer some
advantages in waste reduction and in safeguards against plutonium theft or
covert diversion (but again, probably not against open diversion by the system's
operators) shared in varying degrees by other advanced systems that use such
reprocessing.
Molten-Salt Reactors. Molten-salt reactors, based on the system explored
in the 1950s-era Molten Salt Reactor (MSR) Experiment have also been pro
posed as destroyers of plutonium. This concept is similar in many respects to
the molten-salt ABC, except that the reactor is fully critical and therefore no
accelerator is required. Proponents claim that MSRs offer major safety advan
tages over existing light-water reactor technology. However, like ABC, MSRs
would take decades to develop, license, and deploy.
Pebble-Bed Reactors. Pebble-bed reactors (PBRs), originally developed
for nuclear rocket applications, have also been proposed for use as plutonium
destroyers. Like ABC and molten-salt systems, they are in the early stages of
development.
47Solid-fue} concepts have also been examined but are perceived as not having some of the
advantages of the fluid fuel approach.
OCR for page 213
LONG-TERM DISPOSITION 213
Modular High-Temperature Gas-Cooled Reactors (MHTGRs). In
principle, the MHTGR could also be used in an elimination mode, by reprocess-
ing and recycling its spent fuel. Reprocessing this fuel would be complex, how-
ever, and MHTGR advocates have not pursued this approach in recent years.
As indicated above, it is too soon to choose among these options. Addi-
tional research is desirable to clarify the issues involved in elimination options
in general and to identify the most promising options for that purpose.
CONCLUSIONS
Figure 6-5 summarizes the committee's judgments concerning the long-
term disposition options described in this chapter. Any figure of this kind can
only be an illustrative overview of the options and issues; by their nature, such
figures are oversimplifications. Moreover, these ratings are inevitably judg-
mental. The committee chose to use only three ratings high, moderate, and
low" because the information available cannot confidently support more de-
tailed assessments. This inevitably means that there may be wide variations
among options that receive the same rating; two options might each be expen-
sive enough to be rated as having "high" cost, for example, but one might be
several times as expensive as the other.
The committee has not attempted to reach an "overall" rating for each op-
tion, since readers may rank the criteria differently. Such an overall rating can-
not be reached simply by averaging highs and lows across columns. For exam-
ple, as described earlier, the committee does not consider indefinite storage an
acceptable option, because the black mark under "risks of recovery" with all it
implies for the risks of theft, breakout, and the arms control and nonprolifera-
tion regimes more than outweighs the low risks and costs of this option.
Criteria. All the criteria are described in the negative, so that "high" cor-
responds to high risks or costs, whereas "low" is a more favorable rating.
The first three columns of the chart are all related to the speed with which
an option could be accomplished, which the committee considers to be one of
the principal criteria for choice (discussed under "Risks of Storage" in the text).
"Technical Uncertainty" affects both timing and the degree of assurance of suc-
cess, as does the following column, "Difficulty of Public/Institutional Accep-
tance." The latter category includes licensing and public approval issues, and,
where necessary, issues related to the approval of international parties. The
third column, "Time to Execute," refers to the time required for implementa-
tion once the obstacles represented by the first two columns have been over-
come that is, once development is complete and the requisite licenses and
approvals have been obtained. This includes the time required for any necessary
facility construction or modification, and the time during which the option
would be processing the excess plutonium stock.
OCR for page 214
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OCR for page 216
216 LONG-TERM DISPOSITION
As in the text, "Risks of Handling" refers to the risks of theft or diversion
of materials during the various processes involved before the material reaches
its final state, while "Risks of Recovery" refers to the risks that the material
might be recovered for weapons use (by the state from whose weapons it came
or by others) after disposition was complete. Hence, the latter, combined with
the several timing criteria, effectively portrays the committee's judgment of the
option's political impact on arms reduction and nonproliferation (assuming that
equivalent levels of transparency would be applied to all options); this impact
does not receive a separate column in the chart.
The "ES&M Risk" and "Cost" categories are self-explanatory. The final
column, "Fuel Cycle Policy Signal," refers to the issue relating to more general
U.S. fuel cycle and nonproliferation policies described in the text: those options
involving the use of weapons plutonium in reactors would send the signal that
the United States approved of such use, at least for this limited purpose,
whereas the disposal options would send the signal that even for the pressing
problem of plutonium disposition, the United States did not approve of the use
of plutonium fuels. In this column, therefore, the committee simply indicates
whether the option would or would not use plutonium in reactor fuel, rather
than attempting a high, moderate, and low categorization.
Ratings. For all the criteria other than "Technical Uncertainty," the option
of using 100 percent MOX fuel in U.S. LWRs is used as the standard for a
moderate rating. (Technical uncertainty for the LWR MOX option is rated
low.) Options that involve greater risks or costs than MOX in LWRs are rated
high, while those that involve significantly lower risks or costs are rated low.
Options
Indefinite Storage
Indefinite storage is among the more complex options to rate, because for
the next several decades storage would be relatively simple, safe, and low cost
(at least in the United States), but these judgments would change if it were truly
extended indefinitely.
Indefinite storage is rated as having low technical uncertainty and time to
execute because storage can be (and is being) implemented immediately. Stor-
age is rated as low in risks of handling and ES&H risks (because no processing
is involved), and low in cost (by assuming costs comparable to those at Pantex,
rather than commercial charges for plutonium storage). The difficulty of ob-
taining public and institutional acceptance is rated moderate, although it would
probably be quite difficult to gain public approval for storage that was explicitly
presented as lasting indefinitely, at least in the United States. Indefinite storage
is the only option on the chart rated as having high risks of recovery, since the
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LONG-TERM DISPOSITION 217
material could be removed from the storage site and used for weapons at any
time.
Minimized Accessibility
LWRs with 113 MOX refers to the use of existing or modified LWRs, either
U.S. LWRs using U.S. plutonium or Russian VVER-1000s using Russian plu-
tonium. These are rated as having low technical uncertainty. They are rated
moderate in most other categories, but high under risks of handling, because
the material would have to be transported to three times as many sites as in the
case of LWRs with 100 percent MOX cores. As described in the text, there are
likely to be higher risks of handling in the former Soviet Union under present
circumstances than in the United States.
LWRs with 100 percent MOX (which, like the previous entry, refers to the
use of existing or partly completed LVVRs, in this case with modifications as
necessary for use of full-MOX cores) are rated moderate in all categories except
technical uncertainty, which remains low, as in the case of LWRs with one-
third MOX, because the modifications needed to accommodate full-MOX cores
are not sufficient to create substantial uncertainties or require major
development.
CAND Us, like full-MOX LWRs, are rated moderate under all criteria ex-
cept technical uncertainty, which is rated low, because this option would not
require a major development program. The moderate rating for difficulty of
acceptance is more doubtful than in the case of LWRLs, since Canadian accep-
tance of plutonium fuel use remains uncertain. Similarly, the cost rating for
CANDU reactors is more uncertain.
Substitution for civil plutonium is rated high for difficulty of acceptance,
because of the complex web of arrangements that would have to be changed to
implement this option, but low for time to execute, because the scale of MOX
use already planned is large enough to consume 50 or 100 tons of weapons plu-
tonium quite rapidly if this option were agreed to. ES&H risks are rated low
because there would be virtually no net additional risks compared to the pluto-
nium use already planned; risks of handling would be rated low for the same
reason, except that there is some significant difference in theft and diversion
risk in the shift from reactor-grade to weapons-grade plutonium, and there are
the risks of transport of the plutonium from its current location. Hence the risks
of handling are rated moderate.
Vitrification with high-level waste is rated moderate on all criteria except
risks of handling, where it is rated low, because of the somewhat greater ease of
safeguarding described in the text. The technical uncertainty, which is moder-
ate, is greater than in the case of the reactor options just described. Although
time to execute is also rated as moderate, vitrification might be accomplished
somewhat more rapidly than the LWR and CANDU options if technical uncer-
tainties are resolved.
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218 LONG-TERM DISPOSITION
Deep boreholes are rated high on technical uncertainty because they would
require more development than either the existing reactor options or the vitrifi-
cation option. They are rated high for difficulty of public and institutional ac-
ceptance because of the likely difficulties of obtaining the necessary licenses.
Boreholes are rated as having moderate risks of recovery, with the caveat that
recovery would be less difficult for the state in control of the borehole site than
would recovery of plutonium in spent fuel. Although the cost of implementation
itself would probably rate as low, boreholes are rated moderate on cost because
of the development and licensing programs required. These costs could in fact
ultimately be in the high category (as is also the case with other nonrepository
disposal options). Boreholes are judged moderate on ES&H risks, but if techni-
cal uncertainties are resolved favorably, these risks could turn out to be low.
Sub-seabed disposal is rated high in technical uncertainty because consid-
erable development would still be required before this option could be imple-
mented-but it is the most fully developed of the options receiving this rating.
This approach is rated as having high difficulty of public and institutional ac-
ceptance, because of the legal barriers and likely intense international oppo-
sition to such disposal. As with deep-borehole disposal, however, time to exe-
cute and risks of handling are rated low, and cost is rated moderate because
even though implementation costs could be low, the costs of development and
licensing would be substantial.
Detonation with underground nuclear explosions is rated high for technical
uncertainty, even though it is clear it could be done, because of the many unre-
solved safety and environmental issues. Similarly, it is rated as having high
ES&H risks and acceptance difficulties.
Existing LMRs without reprocessing are less susceptible to across-the-
board ratings than some of the other options because there are wide variations
in the design and characteristics of these facilities; moreover, some are in coun-
tries where the excess weapons plutonium is located, whereas for others, the
plutonium would have to be shipped and agreements negotiated. Existing
LMRs are rated as low in technical uncertainty because the use of plutonium in
these reactors is amply demonstrated; however, there are outstanding technical
issues regarding the safety of some of these facilities. The time necessary to
execute is rated high, because of the relatively small capacity, advanced age, or
poor availability records of the existing LMRs.
ALWRs refers to LWRs built for this mission, whether existing or follow-
on designs. Technical uncertainty is rated low (though this judgment applies
primarily to existing and evolutionary designs). Time to execute is rated high
because licensing and building new reactors would take substantially longer
than using existing facilities.
New LMRs (without reprocessing, and MHTGRs are rated high on time to
execute and cost, because of the delays and costs of development, licensing, and
construction for these advanced reactors, both of which are estimated to involve
higher life cycle costs in the current market than evolutionary LWRs.
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LONG-TERM DISPOSITION 219
Elimination
Ocean dilution is rated as having high technical uncertainty, because al-
though it is clear it could be done, there are large uncertainties concerning the
ultimate ecological impact. It is rated moderate for cost, although the cost of
implementation would be low, because of the likely costs of developing the op-
tion and attempting to gain approval for it.
Space launch is rated high for ES&H risks, because of the risks involved in
possible launch accidents, but this rating could be reduced with a payload de-
sign that provided high-confidence plutonium containment for all plausible
accidents.
LWRs or CANDUs with reprocessing are rated as having high time-to-
execute and costs (as are all of the other reactor reprocessing options) because
of the very long time required to eliminate nearly all of the plutonium by this
means, and the high costs of reprocessing and recycle. Technical uncertainty is
rated as moderate because the plutonium use demonstrated to date has not in-
volved multiple-recycle fuel with its different mix of isotopes. Risks of handling
are rated as high, because these options would involve repeated separation,
transport, and use of separated plutonium, while several of the other reprocess-
ing options are or can be designed to maintain the plutonium in a more theft-
resistant form. ES&H risks are rated as high because of the record of ES&H
impacts of reprocessing in some countries, but the committee notes that appro-
priate application of resources would greatly reduce these risks.
LMRs with reprocessing are also rated as having moderate technical uncer-
tainty, because while some of these systems are being designed for a similar
actinide-burning mission, considerable development is still required. Their
handling and ES&H risks are rated as only moderate, rather than high, on the
assumption that new reprocessing techniques that reduce wastes and safeguards
risks would be employed.
MHTGRs with reprocessing are rated as having high technical uncertainty,
since a reprocessing approach has not been pursued for HTGRs in recent years,
and such a plutonium elimination objective has not been examined in detail.
Like LWRs and CANDUs with reprocessing, they are rated as having high
risks of handling, because of the repeated reprocessing and use of fully sepa-
rated plutonium that would be required. ES&H risks are rated as high, on the
analogy to LWRs and CANDUs with reprocessing, but the same caveat applies.
ABC is rated as having high technical uncertainty, because of the large
amount of technical development still required. It is rated moderate for ES&H
risk, but that judgment is quite uncertain: if ABC fulfills its proponents' expec-
tations, ES&H risk could be quite low, but it is also possible that unexpected
ES&H risks could arise.
MSR and PBR receive the same ratings across the board as ABC, for much
the same reasons. It is too soon to tell which of these technologies would be
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220 LONG-TERM DISPOSITION
preferable for the missions their advocates propose, if these missions are
pursued.
RECOMMENDATIONS
· It is important to begin now to build consensus on a road map for deci-
sions concerning long-term disposition of excess weapons plutonium. Because
disposition options will take decades to carry out, it is critical to develop op-
tions that can muster a sustainable consensus.
· Storage should not be extended indefinitely, because of (1) the negative
impact that maintaining this material in forms readily accessible for weapons
use would have on nonproliferation and arms reduction, (2) the risk of breakout
and (3) the risks of theft from the storage site. One of the key criteria by which
disposition options should be judged is the speed with which they can be ac-
complished, and thus the degree to which they curtail the risks of prolonged
storage.
· Disposition options beyond storage should be pursued only if they reduce
overall security risks compared to leaving the material in storage, considering
both the final form of the material and the risks of the various processes re-
quired to get to that state. In the current unsettled circumstances in Russia, this
. . . . . . ., - .
minimum cnter~on IS a slgnlilcant one.
· The United States and Russia should begin discussions with the aim of
agreeing that whatever disposition options are chosen, an agreed, stringent
standard of accounting, monitoring, and security will be maintained throughout
the process-coming as close as practicable to meeting the standard of security
and accounting applied to intact nuclear weapons.
· Disposition options should be designed to transform the weapons pluto-
nium into a physical form that is at least as inaccessible for weapons use as the
much larger and growing stock of plutonium that exists in spent fuel from
commercial nuclear reactors. The costs, complexities, risks, and delays of going
further than this "spent fuel standard" to eliminate the excess weapons
plutonium completely or nearly so would not be justified unless the same ap-
proach were to be taken with the global stock of civilian plutonium.
· The two most promising alternatives for the purpose of meeting the spent
fuel standard are:
1. The spent fuel option, which has several variants. The principal one is to
use the plutonium as once-through fuel in existing commercial nuclear power
reactors or their evolutionary variants. Candidates for this role are U.S. light-
water reactors (LWRs), Russian LWRs, and Canadian deuterium-uranium
(CANDU) reactors. The use of European and Japanese reactors already licensed
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LONG-TERM DISPOSITION 221
for civilian plutonium should also be considered for Russian weapons
plutonium.
2. The vitrification option, which would entail combining the plutonium
with radioactive high-level wastes (HLW) as these are melted into large glass
logs. The plutonium would then be roughly as difficult to recover for weapons
use as plutonium in spent fuel.
A third option, burial in deep boreholes, has until now been less thor-
oughly studied than alternative 1 and 2, but could turn out to be comparably
attractive.
· A coordinated program of research and development should be under-
taken immediately to clarify and resolve the uncertainties the committee has
identified regarding each of these three options. The aim should be to pave the
way for a national discussion, with full public participation, in order to make a
choice within a very few years.
· Applying the spent fuel standard narrows the options considerably:
1. Options that irradiate the weapons plutonium in reactors only briefly
("spiking"), leaving it far less radioactive than typical spent fuel, and with little
change in its isotopic composition, should not be pursued except possibly as a
preliminary step on the road toward the spent fuel option. (Even for that pur-
pose, in those cases the committee has examined, the possible advantages of the
spiking option over continued storage do not appear to be worth the substantial
cost of such spiking approaches.)
2. Options that involve only a chemical barrier to reuse such as vitrifica-
tion of plutonium without HEW or other fission products should not be pur-
sued, except possibly as a first step toward adding radiological or physical bar-
riers as well.
3. Advanced reactors should not be specifically developed or built for
transforming weapons plutonium into spent fuel, because that aim can be
achieved more rapidly, less expensively, and more surely using existing or
evolutionary reactor types.
4. Options that strive to destroy a large fraction of the plutonium without
reprocessing and recycle, using existing or advanced reactors with nonfertile
fuels, should not be pursued because such approaches cannot destroy enough of
the plutonium to obviate the need for continuing safeguards, and the modest
reduction in security risk that could be achieved is not worth the extra delay,
cost, and uncertainty that development of such approaches would entail.
· Production of tritium should not be a major criterion for choosing among
disposition options.
· Institutional issues in managing plutonium disposition are complex and
the process to resolve them must be carefully managed. The process must pro-
vide adequate safeguards, security, and transparency, as well as protection for
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222 LONG-TERM DISPOSITION
the environment, safety, and health; obtain public and institutional approval,
including licenses; and allow adequate participation in the decision making by
all affected parties, including the U.S. and Russian publics and the interna-
tional community. Adequate information must be made available to give sub-
stance to the public's participation.
· Although the committee did not conduct a comprehensive examination of
the proliferation risks of civilian nuclear fuel cycles, which would have gone
beyond its charge, the risks posed by all forms of plutonium must be addressed.
· While the spent fuel standard is an appropriate goal for next steps, fur-
ther steps should be taken to reduce the proliferation risks posed by all of the
world's plutonium stocks, military and civilian, separated and unseparated; the
need for such steps exists already, and will increase with time. Options for
near-total elimination of plutonium may have a role to play in this effort, and
research on defining and exploring these options should be continued at a con-
ceptual level. These options, however, can only realistically be considered in
the broader context of the future of nuclear electricity generation, including the
minimization of security and safety risks-the assessment of which is beyond
the scope of this report. Studies of that broader context should have as one im-
portant focus minimizing the risk of nuclear proliferation, and should consider
nuclear systems as a whole, from the mining of uranium through to the disposal
of waste; should consider feasible safeguarding methods as elements of devel-
opment and design; and should take an international approach, realizing that
other nations' approaches reflect their differing economic, political, technical,
security, and geographic situations and perceptions.
Representative terms from entire chapter:
disposition options
