Just as the government finally makes a belated decision to decommission the trouble-plagued Monju prototype fast-breeder reactor, it is seeking to pursue a successor project in order to keep alive its bid for a nuclear fuel cycle in Japan. What it should be doing first is conducting a thorough examination of why the Monju project ended in failure and holding an open discussion on whether the nuclear fuel cycle — in which Monju's technology was supposed to serve as a core component — is still a practical and feasible option for this country.

The formal decision to decommission the nation's sole prototype fast-breeder reactor in Tsuruga, Fukui Prefecture, was long overdue. Billed as a dream nuclear reactor for resource-scarce Japan because it produces more plutonium than it consumes as fuel, Monju first reached criticality in 1994, but it has been mostly offline after it was hit by a sodium coolant leak and fire in December 2015. Its trouble-prone operator was judged by the Nuclear Regulation Authority as unqualified to run the facility, but the government has been unable to build a new viable regime to restart its operation.

Despite the injection of more than ¥1 trillion in taxpayer money, Monju was in operation for a mere 250 days over the past 22 years, and never reached 100 percent of its output capacity. It is estimated that restarting the reactor under the updated safety regulations will take at least eight years — a process that, including acquisition of necessary data that will require an additional eight years, is calculated to cost at least ¥540 billion. The decision to decommission the reactor — which in itself would require at least ¥375 billion over 30 years — was inevitable.