The Japanese government officially announced it would scrap plans to build advanced thermal nuclear reactors (ATRs), which run on recycled plutonium as well as the enriched uranium used in conventional reactors.

Last month, Japan's nine biggest utilities, which had been asked to pay part of the bill for the costly advanced thermal reactor project, asked the government to drop the project because of the high costs.The Atomic Energy Commission, an influential advisory body, agreed and adopted an alternative proposed by the utilities to build less expensive conventional reactors.

According to the Federation of Electric Power Companies, an advanced thermal reactor costs more than 50 billion yen ($515 million), nearly twice as much as a conventional light-water reactor.

Japan's ambitious, long-term nuclear power policy plans to boost the country's reliance on energy generated by nuclear power plants to 42 percent in 2010 from the current 33 percent.

As a part of that plan, the government planned to build a 606-megawatt ATR in Aomori, northern Japan, at a cost estimated at 396 billion yen ($4.08 billion) in 1984.

However, protests from local residents held up construction for 10 years. When the Electric Power Development Co., entrusted with building the reactor, conducted a new estimate last March the cost had ballooned to 580 billion yen ($5.97 billion).

The Atomic Energy Agency attributed the higher cost to an advancement in technology, and to an unsuccessful attempt by the project operators to rationalize the project.

"Our commission has decided that future construction of advanced thermal reactors would be difficult considering the circumstances," a commission official said.

"But that does not mean that we are rejecting the importance of Japan's nuclear power projects, both past and present," he added.