A nuclear leak at a South Korean power plant has exposed 22 workers to low-level radiation, officials said yesterday, four days after a major leak in nearby Japan.
Forty-five litres (11.7 gallons) of heavy water leaked on Monday night during maintenance and safety checks at Wolsong, 260 km south-east of Seoul, the Science and Technology Ministry said.
The reactors were not in operation at the time and the leak was confined to the plant, it said.
Officials said the leak appeared to have been caused by human error, but stressed that an official investigation was still under way.
"We cannot make a hasty decision yet but it looks like workers made a mistake," said a ministry spokesman, Mr Han Pung-U.
"The ministry now suspects that the heavy water might have leaked from valves of the moderator." He declined to expand on the nature of the possible error.
Yonhap News Agency said the reactor, a Canadian-built Candu natural uranium reactor with a 700-megawatt annual capacity, had been in operation only since July.
But officials were quick to play down the seriousness of the heavy water leak, the fourth such incident in South Korea since it started its nuclear power programme in the late 1970s.
"This was a minor leak. The amount of radiation to which those workers were exposed is equivalent to a patient undergoing four or five X-rays," Mr Han said.
The heavy water is used as a moderator at the plant to slow the nuclear reaction, and as a coolant.
Other officials said the leak was the first case of group contamination in South Korea, adding the exposed workers were not treated for serious contamination.
"All those exposed to radiation have now turned out to be safe. None of them was hospitalised," said a ministry spokesman, adding all the men were resting at home.
The leak was contained immediately, causing "no damage to the environment outside," he said. The amount of radiation measured 0.006 milliSieverts (mSv) to 4.4 mSv, he said, adding the level was within a permissible range.
Two of the crew were exposed to radiation of above 0.3 mSv and suspended from the plant until they had undergone further checks, he said, without specifying the exact level of exposure.
Mr Han said the leak had not been made public until yesterday because it had not been sufficiently serious to activate emergency notification procedures.
The leak came four days after a massive radiation leak at a nuclear plant in Tokaimura, northeast of Tokyo, which exposed at least 49 people and forced more than 320,000 to shelter in their homes.
Hydrogen gas escaped from a nuclear plant in Lovisa, Finland, yesterday but emergency services quickly brought the situation under control, the FNB/STT press agency reported.
The gas leak happened as work was being done to the outside of the building, including the replacing of hydrogen gas bottles.
"This escape did not endanger the safety of the nuclear plant," said Mr Leif Ekholm, a senior firefighter in Lovisa, which is 90 km east of Helsinki.