Changes in U.S. Surplus Plutonium Disposition program

The U.S. Department of Energy announced its intent to modify some components of its plutonium disposition program. A formal notice in the Federal Register outlines the proposed changes.

The goal of the U.S. Surplus Plutonium Disposition program is to dispose about 50 tonnes of plutonium that was declared excess to U.S. security needs. The U.S.-Russian Plutonium Management and Disposition Agreement, which was finalized in April 2010, requires each side to dispose of at least 34 tonnes of weapon-origin plutonium.

As the U.S. part of the plutonium disposition program was taking shape, DoE identified about 50 tonnes of plutonium to be disposed of. The key decision taken in 2002 called for a dual-track approach - about 17 tonnes of the material were to be immobilized and up to 33 tonnes were to be used as feedstock for MOX fuel to be used in existing civilian light-water reactors. As a result of this decision, the United States began construction of the MOX Fuel Fabrication Facility (MFFF) at Savannah River Site (the facility is built by Areva).

By 2007, DoE decided to use 4 of the 17 tonnes of material in its R&D program - that plutonium was used to manufacture research fuel for non-defense use (which remains unirradiated as of 2010). In 2007, DoE looked at three alternative ways to dispose of the remaining 13 tonnes of the surplus plutonium - glass can-in-canister, ceramic can-in-canister, and MOX fabrication (although less than a third of the material was considered to be suitable for MOX). No decision on a disposition route has been made and now DoE would like to consider other options.

Since 2002, the composition of the material to be disposed of has changed. In 2007, the United States declared 9 tonnes of weapon-origin plutonium (so-called "pit plutonium") as surplus to its defense needs. Two tonnes of that material were added to the 33 tonnes of Pu to be used in MOX. However, the total amount of MOX-designated Pu increased only by one tonne, reaching 34 tonnes. Seven tonnes of the new surplus pit plutonium were added to the material to be disposed of by other route. Of the 13 tonnes of Pu that were previously in this category, only 6 tonnes left - about 6.5 tonnes were moved to the MOX-designated pool (again, without increasing the total amount there; note, that in 2007 it was believed that less than about 4 tonnes can be used for MOX). About 0.6 tonnes will be reprocessed in the H-Canyon and then disposed of at the Defense Waste Processing Facility. As a result, DoE again has 13 tonnes of surplus material without a clear disposition route - 6 tonnes of "old" non-pit plutonium and 7 tonnes of pit plutonium added in 2007. The total amount of surplus plutonium is now about 52 tonnes (34+13+0.6+4 tonnes; additional 3 tonnes of scrap and waste plutonium, not included in these totals, were sent to the Waste Isolation Pilot Plant)

Now DoE is looking for a strategy that would allow it to efficiently combine all elements of its disposition program. Among the options that DoE will consider are immobilization in glass can-in-canister, fabrication of MOX fuel, processing some material in H-Canyon/DWPF, and sending some material to the WIPP facility as waste. Among the decisions that will have to be made is the one about future of the Plutonium Disassembly and Conversion Facility (PDCF), which was to disassemble weapons and convert metal plutonium to oxide form to be used as feedstock for MOX fabrication, and of the Plutonium Preparation (PuP) project, which was supposed to convert and package non-pit plutonium. In its FY2011 request, DoE assumed that the PDCF will absorb PuP activities. Now this option is being reconsidered.

Another component of the current round of changes is the intent to explore the possibility of using the MOX fuel produced by MFFF in reactors of the Tennessee Valley Authority (TVA). Two TVA nuclear power stations have been identified as candidates for MOX - Sequoyah and Brown Ferry. It should be noted that TVA is taking part in a number of DoE programs already - the TVA HEU Down-blending Project and the Tritium Readiness program. Earlier, DoE had a contract with Duke Energy to use MOX fuel in its reactors, but this contract was terminated in 2008, probably after problems with tests of fuel assemblies.