Saturday, July 12, 2014

US Gov't Dithers over Surplus Plutonium

Department of Energy Report of the Plutonium Disposition Working Group: Analysis of Surplus Weapon Grade Plutonium Disposition Options / Public release in April 2014

This is a lengthy, but accessible account of the costs and benefits of five different options for disposing of 34 Metric Tons of excess plutonium from decommissioned US nuclear weapons. The options divide naturally into two classes: 1) nuclear reactor based options which transform the weapons grade plutonium into nuclear waste unsuited, without reprocessing, to the creation of new nuclear weapons (2 options); 2) non-reactor based options that do not change the isotopic composition of the plutonium, but make it difficult to access physically (3 options.) The option cited by the DOE as preferred is from the second class, and is the so-called blending and permanent storage in an approved repository option. This is also the option estimated by DOE to be the least expensive to pursue.

An obvious weakness in this presentation is two-fold: 1) the blending and permanent storage option, the preferred option, is described too simply as involving the physical mixing of the surplus plutonium with an unspecified filler material, in such a way as to turn it into TRansUranic (TRU) waste; 2) the approved repository is the Waste Isolation Pilot Plant (WIPP,) or some WIPP-like TRU waste facility, yet to be constructed.

However, considering the recent problems at WIPP, apparently the result of TRU waste containers having been packaged at Los Alamos National Laboratory (LANL) with untested and unapproved filler material, which led to an unexpected chemical reaction inside the container and an underground explosion at WIPP, this is a truly unfortunate selection.

A further weakness in this unclassified report, is that none of the five options have been evaluated in terms of the amount of money and technical effort that would be required to reconstitute the dispositioned plutonium for future weapons use. For example, both of the reactor based options would require reprocessing of the spent fuel, as well as isotopic purification of the extracted plutonium, and would be extraordinarily expensive as a means of obtaining weapons grade plutonium. However, the non-reactor based options would only require separation of the weapons grade plutonium from the matrix of additives with which it had been mixed. Clearly, the cost of reconstituting the plutonium should be a highly relevant consideration when determining whether a particular option could be effective as a means of rendering the dispositioned plutonium unavailable for future weapons use.

Now, it is clear from the report that the reactor based options would both be very expensive to pursue, whereas the non-reactor based options would be less so. Moreover, among the non-reactor based options the blending and storage option is projected to be the least expensive; i.e., it is the least expensive of all five options. Yet, the reactor based options provide, by far, the most security against retrieval of the dispositioned plutonium, for use in weapons, and the non-reactor based blending and permanent storage option appears to provide the least security.

It seems that the DOE is being penny wise and pound foolish in the matter of the disposition of excess plutonium from US nuclear weapons!

On the other hand, so many things in life are really just trade offs --- . Suppose that the US Congress, as well as the citizens of the State of New Mexico could be convinced to go along with this scheme to mix plutonium waste with filler (kitty litter?) and bury it at WIPP. According to the present DOE report, such a plan would require that the size of WIPP be expanded, but only  by  ~10%. Now if this would be found by all concerned to be a acceptable alteration to the present WIPP mandate, then the probability immediately improves that WIPP might also be expanded to accept so-called tank waste from the DOE's Hanford, WA facility, and maybe even ultimately high-level waste from commercial nuclear power plants.

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