The Spent-Fuel Standard for Disposition of Excess Weapon Plutonium Application to Current DOE Options (2000) / Chapter Skim
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Evaluating Pu Disposition Forms against the Standard
Evaluating Pu Disposition Forms against the Standard
Pages 32-60
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From page 32... ...
For the United States, this would be about In the middle of the age distribution of the spent fuel that will exist in 2020.) We assume that typical spent fuel was irradiated In the reactor to 33,000 megawatt-days per metric ton of initially contained heavy metal (MWd/ MTHM)
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From page 33... ...
. Because the gamma-ray doses from spent fuel and from dispositioned plutonium forms protected by fission products are dominated by 30-year half-life cesium-137 for the period between 5 years and 100 years from the discharge of the fission products from a reactor, knowing the dose rate at one time enables a straightforward calculation of what it would be at other times based on this half life.
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From page 34... ...
Gray, Gregg Hovis, Robert Jones, and Michael Smith, The Can-in-CanisterThen and Now, Lawrence Livermore National Laboratory Report PIP-99-151, 28 October 1999; Leonard Gray and Thomas H Gould, Immobilization Team Comments on Interim Report of NAS Panel Review of Spent-Fuel Standard for Disposition of Excess Weapons Plutonium, Lawrence Livermore National Laboratory Report PIP-99-152, 28 October 1999.
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From page 35... ...
Gray and T Gould, Immobilization Team Comments on Interim Report of NAS Panel Review of Spent-Fuel Standardfor Disposition of Excess Weapons Plutonium, Lawrence Livermore National Laboratory Report PIP-99-152, 28 October 1999; Letter report to Allison Macfarlane from L
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From page 36... ...
. With respect to this barrier, then, we judge the can-in-canister approach as better than comparable to typical spent LWR fuel, the LWR-MOX and CANFLEX-MOX options as comparable, and the standard CANDU-MOX option as much worse than comparable.
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37 in ·_.
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38 di ~ ~ ._' ¢ o ED O a .° In a no _ 0 Pi a a .~ u, 0 In ·P" a, u, u u ~ .s ~ u ~ ¢ =0 m ~ O = .
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39 ~ an s.= ~ it o oc ~ u ~ s:~= p-.N ~ ~ ~ ~ A so ~ o ~ O ~ ~ ~ O F ° in ~ E ._ ' .
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40 dot ·h ~ o c)
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From page 42... ...
(We note that, at the 50-70 percent recovery factors that might be assumed for the processing efforts of subnational groups and proliferant states, the 28 kg of Pu in one can-in-canister item or 5-10 reference LWR spent-fuel assemblies would become 14-20 kg.) With respect to this barrier, we judge the can-in-canister and CANDU-MOX options to be comparable to typical LWR spent fuel, and we judge the LWR-MOX option as worse than comparable.
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From page 43... ...
, which were to be the source of Me fission products In We glass for the can-~n-can~ster approach.23 It is now estimated that development and testing of an alternative process for extracting the fission products from these Savannah River wastes will require another 10 years, so that cesium-137 from Savannah River waste will not be available for addition to glass produced at that site before about 2010.24 A recent National Research Council review of the alternatives DOE has proposed to replace the failed "in-tank-precipitation" process produced the following recommendations that are relevant to judging the potential availability of separated cesium-137 at the SRS:25 .
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From page 44... ...
For typical spent fuel and for the LWR-MOX and standard CANDU-MOX options, this would seem to fall into the category of "more trouble than it would be worth" to the proliferators. For the CANFLEX variant of CANDU-MOX, it is at least conceivable that breaking up the structure would be enough easier than fracturing fuel assemblies themselves to be considered worthwhile, so we rate CANFLEX as worse than comparable to typical spent fuel on this point.
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From page 45... ...
27Leonard Gray and Thomas H Gould, Immobilization Team Comments on Interim Report of NAS Panel Review of Spent-Fuel Standardfor Disposition of Excess Weapons Plutonium, Lawrence Livermore National Laboratory Report PIP-99-152, 28 October 1999.
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From page 46... ...
, hence remains about 2,000 kg (still much more than LWR fuel assemblies)
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From page 47... ...
Barriers to acquisition: signatures aiding detection As noted above, detectability of attempts to acquire, transport, and process dispositioned plutonium forms is a matter of the interaction of intrinsic properties of these forms with engineered and institutional elements of detection. The engineered and institutional elements include national and international materials accountancy and control measures
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From page 48... ...
The intrinsic characteristics of final disposition forms are of course influenced by a variety of choices made in designing and producing these forms (such as the burn-up of MOX heels and the composition of the ceramic and/or glass forms used in immobilization approaches) , and these choices may include the use of additives intended to enhance signatures aiding detection, as discussed further below.
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From page 49... ...
And, In order not to "double count" the possibility that the pluton~um-contain~ng cans in the can-in-canister configuration might prove to be separable from the canister, frame, and radioactive glass by energetic attack at the site of a theft, we assume for this next discussion that the item to be dealt with at the plutonium-extraction facility is, in the can-in-canister case, an intact canister. In the case of spent LWR fuel, the disassembly step involves sawing and chopping operations that are conducted under water because of the intense radiation field.
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From page 50... ...
In our judgment, the reduction in technical difficulty of dissolution and separation associated with the reduced shielding requirements for the can-~n-canister case, compared to those for typical spent fuel, is substantially offset by the greater difficulty the proliferators would face in mastering the chemistry for these steps. With respect to technical difficulty of dissolution arid separation,
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From page 51... ...
This deviation is only moderately offset by the smaller anticipated recovery factor of plutonium from the can-in-canister ceramic than from spent fuel: a well run spentfuel reprocessing operation can recover 85 to 90 percent of the contained plutonium, compared to a Livermore Lab estimate of just over 70 percent as the upper limit for recovery from the can-in-canister ceramic (based on getting 80 percent of the contained plutonium into solution and then losing 10 percent of that in the separation, purification, and conversionto-metal steps) .29 With respect to quantity of material to be processed, we judge the standard CANDU-MOX option to be comparable to typical spent fuel and the CANFLEX CANDU-MOX, LWR-MOX, and can-in-canister options to be worse than comparable.
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From page 52... ...
The fission products in spent-fuel from the LWR-MOX option, which we assume will have a burnup of 40,000 MWd/MTHM and which we are evaluating at 10 years past discharge, would be generating about twice the radiation field of our designated "typical" spent fuel with its burnup of 33,000 MWd/MTHM and an age of 30 years since discharge. The fission products from CANDU-MOX fuel irradiated to 9700 MWd/ MTHM and aged 10 years would generate a field about half as intense as that from our "typical" LWR fuel;30 and those from the CANFLEX CANDU-MOX option (where the assumed burnup is 25,000 MWd/ MTHM)
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From page 53... ...
If this were so, then the relevant concentration for the CANDU options would be 30 percent higher than in the case of our designated "typical" LWR fuel, and the concentration for the LWR-MOX option would be about 3 times higher. In the case of the can-in-canister option, since only the plutonium-containing pucks and not the initially surrounding glass must be dissolved, the concentration of plutonium in solution would be about 10 times that for typical spent fuel.
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From page 54... ...
The radioactive and chemical signatures available for detecting the separation of the ceramic pucks from the glass and the subsequent processing of the former to extract the contained plutonium are different from those available in extracting plutonium from spent fuel using the PUREX process. The three main differences are: the absence, in the case of the can-in-canister approach, of detectable fission products such as the noble gas Kr-85, released during reprocessing of spent fuel; the need to use processes other than PUREX to separate and dissolve the ceramic and extract the contained plutonium; and the higher concentration of plutonium in the ceramic pucks compared to that in typical spent fuel, which, all else equal, will reduce the scale and/or duration, and hence the detectability, of extraction operations.
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From page 55... ...
With respect to signatures aiding detection of plutonium separation, we judge that the LWR-MOX and CANDU-MOX options are comparable to typical spent fuel. We judge the can-incanister option worse than comparable on this criterion, although there is a high likelihood that it could be made comparable through the use of additives to increase detectability, and possibly it could be made better than comparable in this way.
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From page 56... ...
In summary, with respect to the isotopic barrier to utilization of the plutonium in nuclear weapons, we judge the LWR-MOX and standard CANDU-MOX options to be comparable to typical spent fuel, the CANFLEX-CANDU option to be better than comparable, and the can-in-canister option to be much worse than comparable. .` Overall judgments on comparability and compliance Table 5 summarizes our judgments on the comparability, with typical commercial spent LWR fuel, of the four disposition forms LWR-MOX, standard CANDU-MOX, CANFLEX CANDU-MOX, and the reference can-in-canister configuration—in respect to all of the proliferation barriers considered here.
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From page 57... ...
The magnitude of this net deviation from reference spent LWR fuel in importance-weighted barriers to acquisition, separation, and utilization of the contained plutonium is too large, in our judgment, to meet the spent-fuel standard's requirement of "roughly as difficult..." Accordingly, we judge the standard CANDU-MOX option to be noncompliant with the spent-fuel standard. The CANFLEX CANDU-MOX option is worse on difficulty of onsite reduction of mass & radiation; worse on quantity of material to be processed; better on isotopic composition; and comparable on the remaining eight barriers.
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From page 58... ...
. Taking into account the importance ratings of the barriers involved, the two "better" performances could be deemed to compensate for enough of the "worse" on quantity of material to be processed and the "much worse" on isotopic composition to permit a judgment of compliance with the spent-fuel standard if analysis and testing showed performance to be comparable with respect to difficulty of on-site reduction of mass & radiation and if it proved possible, using additives, to make the signatures aiding detection of separation at least comparable to those for typical LWR spent fuel.
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From page 59... ...
But we believe all these approaches would be worth revisiting in the event that the current configuration is ultimately judged noncompliant with the spent-fuel standard. Some combination of them and perhaps others not mentioned her~might suffice to bring the can-in-canister option into compliance.32 32Some of these approaches would undoubtedly increase costs, but we would reiterate in this connection the emphatically stated view of the previous CISAC plutonium reports that security is primary in this matter and cost secondary (unless and until costs become high enough to prevent taking the steps that security requires)
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