The government's Basic Energy Plan, updated last week after its first review in four years, features a pledge to reduce the nation's stockpile of plutonium extracted from spent nuclear fuel. Today, the plutonium stockpile has reached 47 tons, including 37 tons stored in Britain and France, which have been commissioned to reprocess spent fuel from Japan's nuclear power plants. The goal of reducing the unused plutonium stockpile was apparently made in view of a concern expressed by the United States, which under a bilateral nuclear pact authorizes Japan to reprocess spent nuclear fuel. Japan is the only non-nuclear weapon state with this authority.

A significant reduction over the short term is expected to be difficult. Behind the accumulation of unused plutonium is the government's long-standing but stalemated policy of seeking a nuclear fuel cycle, which should be reviewed to reach a fundamental solution to the problem.

Under the elusive nuclear fuel cycle policy, plutonium extracted from spent fuel removed from nuclear reactors is to be converted into plutonium-uranium mixed oxide (MOX) fuel to be used either in fast-breeder reactors or in conventional nuclear plants. But Monju, the nation's sole fast-breeder reactor and once deemed a prototype for a dream technology for this resource-scarce country because it produces more plutonium than it consumes as fuel, remained mostly idle after it reached criticality for the first time in 1994. It suffered a sodium coolant leak and fire in 1995 and a subsequent series of other problems, until the decision was made in 2016 to finally pull the plug for good.