TOKYO (Reuters) - The operator of Japan's crippled Fukushima nuclear plant on Thursday detailed a new leak of radioactive water as Greenpeace slammed the country's "inadequate response" to a growing threat to sea water and health.
And in an embarrassing reversal, Tokyo Electric Power officials changed a key element of an account of the early response to the crisis it had given on Saturday as part of a government investigation into the accident.
Tokyo Electric said up to 57 tonnes of highly contaminated water had leaked from a storage facility into a trench. It vowed to step up monitoring of groundwater.
The disclosure raises the stakes in a race to complete by next month a system to decontaminate a massive pool of radioactive water at the site that critics see as a growing risk to both the Pacific and groundwater.
In early April, the utility dumped about 10,000 tonnes of radioactive water into the ocean, prompting criticism from neighbors China and South Korea.
Environmental group Greenpeace said seaweed had been found with radiation levels 60 times higher than official limits, raising concerns about risks from contaminated sea water more than two months after the Fukushima-Daiichi plant was hit by an earthquake and tsunami.
"Our data show that significant amounts of contamination continue to spread over great distances from the Fukushima nuclear plant," a statement quoted Greenpeace radiation expert Jan Vande Putte as saying.
One seaweed sample showed readings over 60 times above the limits set by the government.
"The concentration of radioactive iodine we found in seaweed is particularly concerning, as it tells us how far contamination is spreading along the coast, and because several species of seaweed are widely eaten in Japan," Vande Putte said.
The magnitude 9.0 earthquake on March 11 and the massive tsunami that followed killed about 24,000 people and knocked out power to the Fukushima plant, triggering the world's worst nuclear accident since Chernobyl in 1986.
The crisis has displaced some 80,000 residents from around the plant and prompted a review of Japan's energy policy, with the government "starting from scratch" on nuclear policy.
The effort to regain control of the Fukushima plant relies on pumping massive quantities of water to cool the three reactors that suffered meltdowns.
A poll by the Asahi newspaper published on Thursday showed 42 percent of Japanese people opposed nuclear power, up from 18 percent before the disaster.
The survey underscored deepening concerns about nuclear safety and criticism of the halting response to the crisis and incomplete disclosure by government officials and the utility.
Tokyo Electric officials said on Thursday that the Fukushima plant's chief officer had ignored an order to stop injecting sea water into the No. 1 reactor. Experts said his decision was the correct one.
Officials said earlier that an adviser to Prime Minister Naoto Kan had raised concern about the injection a day after the quake prompting Tokyo Electric to halt pumping in sea water.
The revised account was triggered in part by the visit of a U.N. nuclear safety team to prepare a report on Fukushima, Tokyo Electric Vice President Sakae Muto said.
Even before Greenpeace's outburst, Kan's government has been under fire for its response to the disaster and a leading opposition figure said Thursday's revelation would not help.
"I don't see how Japan can recover international trust," said Sadakazu Tanigaki, head of the opposition Liberal Democratic Party, who now plans a no-confidence motion against Kan's Cabinet.
People forced to evacuate from the town of Namie near the Fukushima plant were allowed back to their homes for a short visit on Thursday.
As residents in protective white suits laid flowers for the dead on a long table at a roadside in the abandoned town, a Buddhist monk wearing a stole over his suit recited a sutra.
"It was like being at a different place," one man told TV Tokyo.
"Perhaps I could have grieved more if something was left standing. But it was like being in a strange place."
Additional reporting by Shinichi Saoshiro; Writing by Kevin Krolicki; Editing by Nick Macfie