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OCR for page 1
Executive Summary
BACKGROUND AND CHARGE TO THE PANEL
The concept of the "spent-fuel standard" was introduced, in the 1994
and 1995 reports of the NAS Committee on International Security and
Arms Control (CISAC) on the disposition of excess weapons plutonium,
as the criterion for judging the adequacy of resistance to theft and prolif-
eration conferred by the intrinsic characteristics of the final plutonium
form produced by a disposition option.) That standard held that pluto-
nium in its final dispositioned forms should be roughly as difficult to
acquire, process, and utilize In nuclear weapons as is the plutonium in
typical spent fuel from civilian power reactors.
The 1994 and 1995 reports concluded Mat He two disposition methods
most likely to be able to meet the spent-fuel standard In the near future
are
(a) embodying the plutonium in mixed-oxide (MOX) fuel and irradi-
ating this once through In civilian reactors of currently operating
types ("the MOX option") and
1Committee on International Security and Arms Control, National Academy of Sciences,
Management and Disposition of Excess Weapons Plutonium, Washington, DC: National Acad-
emy Press, 1994, 275 pp.; and Panel on Reactor-Related Options, Committee on International
Security and Arms Control, National Academy of Sciences, Management and Disposition of
Excess Weapons Plutonium: Reactor-Related Options, Washington, DC: National Academy
Press, 1995, 408 pp.
OCR for page 2
2 SPENT-FUEL STANDARD FOR DISPOSITION OF EXCESS WEAPON PLUTONIUM
(b) immobilizing the plutonium together with large quantities of
fission products in a glass and/or ceramic matrix encased in steel
('`the immobilization optional.
The 1995 report argued further that, because both of these options face a
combination of technical and institutional barriers that translate into un-
certainties about the pace at which they could be implemented, the best
chances for having at least one deployable option at an early date in both
the United States and Russia would result from pursuing both options in
parallel ("the dual-track approach") in both countries.
These CISAC recommendations have proven to be somewhat contro-
versial in two main respects: the "dual track" approach (with some fac-
tions, in each country, favoring one or the other approach to the exclusion
of the alternative, and some favoring different approaches) and the appro-
priateness and interpretation of the "spent-fuel standard" (including
whether particular variants of the MOX and immobilization options meet
it). The first issue has been settled, at least for the time being, by the recent
U.S.-Russian Bilateral Plutonium Disposition Agreement: * specifies that
Russia will disposition 34 metric tons of excess military plutonium entirely
by the MOX route and that the United States will disposition the same
amount, 3/4 by the MOX route and 1/4 by the immobilization route. The
second set of questions those connected with clarification and applica-
tion of the spent-fuel standard is the focus of the current report.
The charge to the Pane} from the Office of Fissile Material Disposi-
tion in the U.S. Department of Energy (DOE) was, more specifically, to
(1) amplify and clarify the spent-fuel standard and the considerations
to be taken into account in its application; and
(2) use the results of task (1) to determine whether the final pluto-
nium forms produced by the two primary-candidate disposition
options currently being pursued by DOE under the "dual-track"
approach—"can-in-canister" immobilization of the plutonium
together with high level radioactive wastes and once-through irra-
diation of the plutonium in mixed-o~ade (MOX) fuel in commercial
light-water or Canadian deuterium-uranium (CANDU) reactors-
meet this standard.
The Panel was not asked to address: the proliferation and theft resistance
of the steps that lead, under these disposition options, to the final pluto-
nium forms; any questions related to geologic disposal or interim storage
of these final forms except insofar as the properties of the final forms
under such disposal or storage relate to assessing compliance with the
OCR for page 3
EXECUTIVE SUMMARY
3
spent-fuel standard; or disposition alternatives other than the MOX and
immobilization options described above. Important issues exist under all
of these headings some of them treated in the 1994 and 1995 reports-
but we were not charged to revisit or explore them here, and the time and
resources available for this study would not have permitted our doing so.
SUMMARY OF PRINCIPAL FINDINGS
.˘
As noted above, the spent-fuel standard holds that the final pluto-
nium form produced by a disposition option should be approximately as
resistant to acquisition, processing, and use in nuclear weapons as is the
plutonium in typical spent fuel from once-through operation in a com-
mercial light-water reactor (LWR). We have used, as a specific basis of
comparison, 30-year-old spent LWR fuel irradiated to 33,000 megawatt-
days per initial metric ton of heavy metal in fuel (MWd/MTHM).
Judgments about compliance with the spent-fuel standard should
depend only on the intrinsic properties of the final plutonium form, not
on the extent of engineered and institutional protections. Such protec-
tions are appropriate and necessary, both for ordinary spent fuel and for
plutonium disposition forms meeting the spent-fuel standard, but they
are not substitutes for the built-in barriers to which the spent-fuel stan-
dard relates. Meeting the spent-fuel standard should be regarded as a
necessary but not sufficient condition for judging a disposition method
satisfactory, and satisfactory disposition should be understood to be only
one element of the needed comprehensive approach to managing the
hazards of excess nuclear weapons and weapons-usable materials.
No mechanistically applicable formula can avoid the need for a mul-
tiplicity of informed judgments in the process of determining whether a
specified plutonium disposition form meets the spent-fuel standard. We
have attempted to systematize the process of making these judgments in
a matrix framework that combines
(a) assessments of the relative importance, against a range of prolif-
eration threats, of the various intrinsic barriers provided by
dispositioned plutonium forms, with
(b) assessments of the performance of different dispositioned pluto-
nium forms with respect to these barriers, compared with the per-
formance of the reference LWR spent fuel.
We have applied this approach to address the spent-fuel-standard
compliance of the final plutonium forms from four disposition options:
spent fuel from the once-through irradiation in light-water-reactors, to
OCR for page 4
4 SPENT-FUEL STANDARD FOR DISPOSITION OF EXCESS WEAPON PLUTONIUM
40,000 MWd/MTHM, of MOX fuel made with weapon plutonium (WPu-
MOX); spent fuel from once-through irradiation in CANDU reactors, to
9700 MWd/MTHM, of WPu-MOX fuel; spent fuel from once-through
irradiation in CANDU reactors, to 25,000 MWd/MTH, of WPu-MOX fuel
in a configuration binding numerous CANDU-sized fuel bundles into a
much larger agglomeration; and the current DOE can-in-canister con-
figuration, in which unirradiated weapon plutonium is immobilized in
ceramic pucks contained in steel cans, in a steel frame, in a steel canister
filled with radioactive glass.
We have concluded that the LWR-MOX option is compliant with the
spent-fuel standard; that the standard CANDU-MOX option is not com-
pliant; that the compliance of the CANFLEX CANDU-MOX option is
marginal; and that compliance of the reference can-in-canister option with
the spent-fuel standard is contingent on the outcome of efforts to clarify
this option's resistance against on-site attack and to improve its signa-
tures aiding detection of separation activities.
We have concluded, further, that resolution of the vulnerability of the
current can-in-canister configuration to on-site attack will require addi-
tional investigation. Defining the full details of the required effort was
beyond the scope of the current study. But we are not recommending an
open-ended R&D program. Rather, we suggest that a full scale-test be
carried out involving an attack judged most likely to succeed by a group
of independent subject-matter experts. The outcome of such a test would
provide a basis for deciding what if any additional physical tests, model-
ing and simulation studies, and perhaps other analyses are required. We
believe that such a testing and development program for the can-in-
canister approach might well lead to identification of variants with suffi-
cient resistance to attack to meet the spent-fuel standard, even if it turns
out that the resistance of the current can-in-canister configuration is
inadequate.
..
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Representative terms from entire chapter:
final plutonium
