(December 15, 1995) Japan's prototype fast-breeder nuclear reactor, Monju, was manually shut down on December 8, after 3 tonnes (NHK tv is claiming up to 5 tonnes) of sodium leaked from the cooling system. "We manually shut down the reactor when we found sodium leaking from the secondary cooling system," a spokesman for the Power Reactor and Nuclear Fuel Development Corporation (PNC) said.
(444.4392) WISE-Amsterdam - There was no danger of radiation leakage, he assured. Workers shut down the plant at 9:20 p.m. after an alarm went off at 7:47 p.m. Technicians drained 80 tons of sodium to prevent more leakage. Heavy smoke caused by a reaction between the leaking sodium and air delayed technicians' efforts to investigate the leak. According to PNC officials, engineers who had gone into the affected area wearing protective clothing and oxygen masks believed the leak was from piping repaired in 1992.
Although the PNC acknowledged the sodium leak was "a very serious setback for the fast-breeder reactor", it said there was no radioactive harm to the environment from the accident. Masayasu Miyabayashi, head of the Science and Technology Agency's Nuclear Safety Bureau, said he took the first such accident in Japan "seriously".
Monju, located on the coast of Tsuruga, northwest of Tokyo, is the world's second largest fast-breeder reactor and the cornerstone of Japan's ambitious nuclear-power programme. It started operations in August after a decade of technical delays and costly preparations. The plant was operating at 40 percent of 280,000 kilowatt output capacity.
PNC planned the start-up last April but the reactor was shut down during a pre-test run in March because of a problem with the reactor's steam control system. It was restarted in May only to be shut down again due to further problems. PNC hoped Monju would begin supplying electricity to the commercial grid sometime next year.
The accident set off demands for a review or an end to Japan's nuclear programme. Nuclear plants supply 33 percent of the nation's power needs and this figure is expected to rise to 42 percent by 2010.
Politicians from the western coastal prefecture of Fukui blasted the PNC for its delay in announcing Friday's accident. Fukui Governor Yukio Kurita criticised the corporation for waiting nearly one hour after the shutdown before contacting his government.
Sources:
- Reuter, 8, 9 & 10 Dec. 1995
- UPI, 9 Dec. 1995
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