The decision by nuclear power regulators to call for a change in the operator of Monju, the nation's sole prototype fast-breeder reactor, not only puts the fate of the trouble-prone project in question but raises serious doubts about the government's decades-old policy of seeking to establish a nuclear fuel cycle. The government should take the upcoming recommendations from the Nuclear Regulation Authority (NRA) as a cue to rethink the controversial and effectively stalled policy itself.

Monju, on which the government spent ¥1 trillion to build, was once touted as a "dream" reactor that produces more plutonium than it consumes as fuel — a boon for resource-scarce Japan. It was also billed as a key component of the nuclear fuel cycle, in which spent fuel from nuclear power plants is reprocessed into plutonium-uranium mixed oxide (MOX) fuel to be reused at fast-breeder reactors and other types of nuclear reactors.

But the plant in Tsuruga, Fukui Prefecture, has been kept offline for most of the past two decades. After first reaching criticality in 1994 and starting to generate electricity the following year, Monju was shut down in December 1995 due to a sodium coolant leak and fire, and remained idled for more than 14 years until it briefly resumed operation in 2010 — when another accident forced it to be halted again. Subsequent revelations of sloppy safety checkups by its operator, the government-backed Japan Atomic Energy Agency, led the NRA to effectively order a ban on Monju's operations.