The U.K. government released a document Management of the UK's Plutonium Stocks that outlines a strategy of dealing with the U.K.'s separated civilian plutonium. The document is part of the public consultation initiated by the U.K. government in July 2010.
In its consultation paper, released in February 2011 the Department of Energy and Climate Change (DECC) suggested an approach that would "pursue reuse of plutonium as mixed oxide fuel (MOX)." This approach was criticized at the time as being expensive and technologically unproven (see Plutonium to MOX: "Repeating Mistakes of the Past" and UK Separated Plutonium Management - A New Sellafield MOX Plant? in this blog). Nevertheless, DECC insisted on the MOX strategy, which "would mean converting the vast majority of UK civil separated plutonium into fuel for use in civil nuclear reactors. Any remaining plutonium whose condition is such that it cannot be converted into MOX, will be immobilised and treated as waste for disposal." The report also suggested that the future U.K. MOX program could manage foreign civilian plutonium currently stored in the U.K.
Addressing the concerns about the technical and commercial viability of the strategy, the report asserts that "lessons learned from the Sellafield MOX plant can be applied to a new MOX plant and that overseas experience gives confidence that any new MOX plant will be successful." However, the question of availability of reactors that could provide viable market for MOX fuel remains open. In August 2011, the Nuclear Decommissioning Authority announced a decision to close the Sellafield MOX Plant, partially in response to the anticipated lack of demand for MOX fuel after the Fukushima crisis.
According to the most recent declaration submitted to IAEA, as of December 31, 2010 United Kingdom had 114.8 tonnes of unirradiated separated plutonium on its territory and 0.9 tonnes of U.K.'s plutonium outside of the country. The amount of plutonium in the U.K. includes 28.0 tonnes that belong to foreign countries. Also, it apparently includes the 4.4 tonnes of plutonium that the United Kingdom declared as excess to its national security needs. It is not clear if that plutonium will be covered by the new policy.