Reducing plutonium stockpiles

The agreement reached last week by nations at the Nuclear Security Summit to minimize their stockpiles of plutonium gives more reason for Japan to review its nuclear fuel cycle program, under which it plans to reprocess spent fuel from nuclear power reactors to extract plutonium for reuse — despite uncertainties over how its already large stock of separated plutonium would be consumed.

In a bid to reduce the amount of nuclear materials that can be exploited for terrorism purposes, world leaders gathering at the summit held March 24-25 in The Hague, the Netherlands, agreed in their joint statement that protective measures in storing weapons-grade plutonium and highly enriched uranium should be updated. The communique also urged the states to cut the stockpiles of both nuclear materials to the minimum level “as consistent with national requirements.”

Japan is the only non-nuclear weapons country to have a program to reprocess spent nuclear fuel on an industrial scale. To dispel nuclear proliferation fears, the government has pledged that it will not possess plutonium whose use has not been decided.

But the prospect for using Japan’s stock of plutonium is now unclear. While Japan’s decision to return to the U.S. about 300 kg of weapons-grade plutonium that had been provided for research purpose during the Cold War era was hailed as one of the achievements at the The Hague summit, the nation has 44 tons of separated plutonium from past reprocessing of spent nuclear fuel either at home or overseas.

Under the government’s nuclear fuel cycle program, the extracted plutonium is to be used in plutonium-uranium mixed-oxide (MOX) fuel for consumption at fast-breeder reactors and other types of reactors. But the nation’s sole prototype fast-breeder reactor Monju in Tsuruga, Fukui Prefecture, has been kept offline for much of the past two decades after it first reached criticality in 1994 and the prospect for the fast-breeder reactor’s commercial operation appears dim.

Utilities started using MOX fuel at some of their light-water reactors after years of delay but they have all been shut down following the March 2011 meltdowns at Tokyo Electric Power Co.’s Fukushima No.1 nuclear power plant. The Abe administration plans to restart some of the idled reactors once they have been given safety clearances by the Nuclear Regulation Authority under tightened guidelines. But the government’s plan before the 2011 crisis to consume the separated plutonium as MOX fuel at 16 to 18 reactors across the country seems unfeasible now.

Meanwhile the launch of a nuclear fuel reprocessing plant in Rokkasho, Aomori Prefecture, has been delayed for years due to a series of technical problems. The government is pushing for the plant’s launch as a key component of the nuclear fuel cycle policy. But extraction of more plutonium at the reprocessing plant would only add to the stockpiles whose prospect for use is uncertain.

In the summit, Prime Minister Shinzo Abe stressed that Japan’s plutonium stockpiles have been safely guarded and that its use for exclusively civilian purposes has been confirmed by the International Atomic Energy Agency.

Still the Abe administration and power companies should take the agreement at the Nuclear Security Summit seriously and come up with feasible plans for steadily reducing the nation’s plutonium stockpiles. One option would be to give up the nuclear fuel cycle program that entails the reprocessing of spent fuel.