Tokyo: Japan`s controversial "fast-breeder" nuclear reactor reached criticality -- the point when a nuclear chain reaction becomes self-sustaining -- on Saturday following 14 years of suspension.
The Monju Prototype Fast Breeder Reactor, located in a coastal town 350 kilometres (220 miles) west of Tokyo, cleared the first hurdle of its test operations on the road to generating power at full capacity in 2013.
"It has reached criticality with no problems," said Katsuya Kinjo, a spokesman for the Japan Atomic Energy Agency, which runs the reactor.
On Thursday, the Monju was reactivated for the first time since the plant was shut down in 1995 following a fire and a subsequent cover-up that sparked public anger.
Unlike regular light-water reactors that run on uranium, fast-breeders use a mix of plutonium and uranium, including waste from conventional reactors, and generate or "breed" more plutonium than they consume.
Major industrialised nations initially rushed to develop the "dream reactors", but technical problems and fears over the proliferation of weapons-grade plutonium have led many to withdraw from the projects.
The United States, Britain and Germany have suspended fast-breeder projects and France shut down its last such reactor last year. The United States and France continue research and development of the technology.
Japan, an energy resource-poor nation with plans to expand its nuclear power sector, gave the green light for the Monju relaunch earlier this year, with a target of commercialising fast-breeders by 2050.