Japan has decided to scrap an experimental nuclear reactor that cost the equivalent of nearly £7 billion over 22 years - even though it was only operational for 250 days.

Government ministers decided to decommission the trouble-plagued “Monju” fast-breeder reactor that had drained government finances for decades without living up to hopes it would be a saviour for the resource-poor nation's energy needs.

The so-called “dream reactor” was designed to burn a plutonium-uranium mix, while potentially producing more plutonium in the process that could be converted into more nuclear fuel. It cost some £6.89 billion over its lifetime.

The reactor suffered a leakage of sodium, used as coolant, in 1995, months after it went online, a major accident that caused its initial years-long suspension before more recent safety problems.

It was estimated that Monju would have required costly upgrades to meet new safety standards introduced after meltdowns at a nuclear plant in Fukushima that was flooded by a tsunami in 2011, with at least another £3.7 billion and eight more years of work estimated to restart Monju, officials said, citing their latest estimates.

“We have decided to decommission Monju because restarting it would require significant time and cost,” chief cabinet secretary Yoshihide Suga said from Fukui, home to Monju in western Japan. Local officials oppose losing Monju, which rakes in subsidies and provides jobs.

Officials, however, said Japan's spent fuel recycling plan would not change even without Monju. Opponents say Japan should give up the program and shift to direct burial of spent fuel as waste, but officials are seeking another fast reactor to replace Monju, although details are still unclear.