DIRECT DISPOSAL OF EXCESS PLUTONIUM*

The global stockpile of separated plutonium stands at about 500 tons. Approximately half was separated for nuclear weapons, mostly during the Cold War, and approximately half for recycle into power reactor fuel – originally for plutonium breeder reactors. With the end of the Cold War, Russia and the United States each declared 34 tons of weapon-grade plutonium excess. Russia’s current plan is to use its 34 tons to fuel its prototype breeder reactors. The U.S. decided to make mixed-oxide (MOX) uranium-plutonium fuel for light water reactors. In 2013, however, the Obama administration concluded that this approach “may be unaffordable...due to cost growth and fiscal pressure.” With the indefinite postponement of the plutonium breeder reactor programs in France, Japan and the UK, they too were confronted with a plutonium-disposal problem. France pioneered the MOX route and has been relatively successful, although, due to continued spent fuel reprocessing, its stockpile of separated plutonium has continued to grow and currently stands at about 60 tons. France has fabricated MOX fuel out of plutonium it separated for Japan but, over the decade prior to the Fukushima accident, Japan managed only to recycle 2.5 tons of plutonium in this manner and now has a stockpile of almost 50 tons of unirradiated plutonium. The UK has a stockpile of 100 tons of separated plutonium and is discussing various options for disposing of it, including in MOX. In 2014, the Department of Energy published a preliminary assessment of alternatives to MOX and found at least one (down-blending and disposal in the deep-underground Waste Isolation Pilot Plant in New Mexico) much less costly than MOX. The analysis of other options: disposal with vitrified (glassified) high-level waste at Savannah River and/or in deep boreholes were less complete but both are potentially interesting. Potentially a mix of all three could be the best option of all. Given that the futures of the MOX programs in France, Japan and the UK are all uncertain, they will be watching what the U.S. does with interest.