The operator of a damaged Japanese nuclear power station said Wednesday it detected high levels of radioactive caesium above one of the Fukushima Daiichi plant's six reactors, dpa reported.
Tokyo Electric Power Co (TEPCO) said the density of radioactive caesium-134 above reactor 1 was 18 times the permissible level.
Since the plant was hit by a magnitude-9 earthquake and tsunami on March 11, it has leaked radioactive materials into the environment.
The operator on Sunday started to measure the level of radioactive substances above reactors number 1 to 4 and detected 360 becquerels of caesium-134 per cubic metre above reactor 1, where most of the fuel rods are believed to have melted, public broadcaster NHK reported.
TEPCO also found 7.5 times the 50-bequerel limit of caesium-134 above reactor 4, which has no fuel in its core. The substance was believed to have come from the fuel storage pool and reactor number 3, NHK said.
The company plans to cover the reactor buildings with polyester sheets to prevent the further dispersal of radioactive substances.
Prime Minister Naoto Kan said before leaving for France Tuesday that his government might review its basic energy policy programme ahead of the scheduled review set for 2013.
Kan suggested that discussion needed people from various backgrounds, and not exclusively industry ministry officials.
The current basic energy policy aims to boost the proportion of electricity produced with nuclear energy to about 50 per cent and that of renewable energy sources to 20 per cent by 2030.
Mizuho Fukushima, leader of the small Social Democratic Party, urged the prime minister to scrap all plans to build new nuclear reactors and make the country fully dependent on renewable energy sources by 2050.
At the meeting of the Group of Eight countries in Deauville, France, Kan was expected inform the other leaders about Japan's response to the crisis and the nation's future energy policy.
Japanese media reported the premier would announce a new programme to develop renewable energy while continuing to depend on nuclear power as a key energy source after reinforcing safety.