By Kiyoshi Takenaka and Yoko Kubota
TOKYO (Reuters) - Mistaken radiation readings given out by the operator of Japan's crippled nuclear plant were "absolutely unforgivable," the government's chief spokesman said on Monday, as highly radioactive water was found to have leaked out of a reactor.
Engineers have been battling to control the six-reactor Fukushima complex since it was damaged by a March 11 earthquake and tsunami that also left more than 27,000 people dead or missing across northeast Japan.
Fires, explosions and radiation leaks have repeatedly forced them to suspend work, including on Sunday when radiation levels spiked to 100,000 times above normal in water inside reactor No. 2. Tokyo Electric Power Co (TEPCO), the plant operator, had earlier said it was 10 million times the normal level.
"On one hand, I do think the workers at the site are getting quite tired," Chief Cabinet Secretary Yukio Edano told a news conference. "But these radiation tests are being used for making various decisions on safety and therefore these mistakes are absolutely unforgivable."
A partial meltdown of fuel rods inside the reactor vessel was responsible for the high levels of radiation at reactor No. 2 but Edano said the radiation had mainly been contained in the reactor building.
TEPCO later said radiation above 1,000 millisieverts per hour was found in surface water in channels outside the reactor. That is the same as the level discovered on Sunday. The U.S. Environmental Protection Agency says a single dose of 1,000 millisieverts is enough to cause haemorrhaging.
The underground channels did not flow into the sea but the possibility of radioactive water seeping into the ground could not be ruled out, company officials told a news conference.
On the weekend, the spike in radiation levels forced a suspension of work at the reactor, with experts warning that Japan faced a long fight to contain the world's most dangerous atomic crisis in 25 years.
"This is far beyond what one nation can handle -- it needs to be bumped up to the U.N. Security Council," said Najmedin Meshkati, of the University of Southern California. "In my humble opinion, this is more important than the Libya no-fly zone."
Plant operator TEPCO has conceded it faces a protracted and uncertain operation to contain the overheating fuel rods and avert a meltdown.
"Regrettably, we don't have a concrete schedule at the moment to enable us to say in how many months or years (the crisis will be over)," TEPCO vice-president Sakae Muto said in the latest of round-the-clock briefings the company holds.
He also apologised over the mistaken radiation reading.
SEA RADIATION DROPS SHARPLY
Murray Jennex, a nuclear power plant expert and associate professor at San Diego State University, said "there's not really a plan B" other than to dry out the plant, get power restored and start cooling it down.
"What we're now in is a long slog period with lots of small, unsexy steps that have to be taken to pull the whole thing together," he said by telephone.
The good news, he said, was that the reactor cores appeared to be cooling down.
There was good news as well about the radiation levels in the sea just off the plant, which skyrocketed on Sunday to 1,850 times normal. Those had come down sharply, Hidehiko Nishiyama, deputy director general of the Nuclear and Industrial Safety Agency, told a news conference on Monday.
Though experts said radiation in the Pacific would quickly dissipate, the levels at the site are clearly dangerous, and the 450 or so engineers there have won admiration and sympathy around the world for their bravery and sense of duty.
Last week, two workers at Fukushima were injured with radiation burns to their legs after water seeped over their shoes, and on Sunday, engineers had to abandon reactor No. 2 after the new reading.
Beyond the evacuation zone around Fukushima, traces of radiation have turned up in tap water in Tokyo, 240 km (150 miles) to the south.
Japanese officials and international nuclear experts have generally said the levels away from the plant are not dangerous for humans, who anyway face higher radiation doses on a daily basis from natural substances, X-rays or flights.
CHERNOBYL ECHOES
One long-term solution may be to entomb the Fukushima reactors in sand and concrete as happened at Chernobyl, Ukraine, after the 1986 disaster that was the world's worst.
The Japan crisis has prompted a reassessment of nuclear power across the world. It had its most direct political impact yet in foreign politics in Germany at the weekend.
Chancellor Angela Merkel's Christian Democrats lost control of Germany's most prosperous state, Baden-Wuerttemberg, as anti-nuclear sentiment benefited her opponents in a regional vote.
Asked about Japan's plans for nuclear power, Edano said the priority was to resolve the crisis, then an assessment could be made.
Prime Minister Naoto Kan has kept a low profile during the crisis, but may face awkward questions after Kyodo news agency said his visit to the region the day after the disaster delayed TEPCO's response to the unfolding situation. Edano denied that was the case.
The nuclear crisis has compounded Japan's agony after the magnitude 9.0 quake and massive tsunami devastated its northeast coast, turning whole towns into apocalyptic-looking landscapes of mud and debris.
Residents there have been repeatedly rattled by aftershocks from the strongest earthquake in Japanese history, including a magnitude 6.5 tremor on Monday that triggered a tsunami warning.
"I lived through World War Two, when there was nothing to eat and no clothes to wear. I'll live through this," said Mitsuharu Watanobe, sitting cross-legged on a blanket in an evacuation centre in Fukushima city.
"But the scary thing is the radiation. There is a gap between what the newspapers write and what the government is saying. I want the government to tell the truth more."
The latest death toll was 10,804 people, with 16,244 people missing 17 days after the disaster. About a quarter of a million people are living in shelters and damage could top $300 billion (187 billion pounds), making it the world's costliest natural disaster.
(Additional reporting by Chizu Nomiyama, Elaine Lies and Shinichi Saoshiro in Tokyo, David Dolan in Fukushima, Gerard Wynn in London and Alister Doyle in Oslo, Scott DiSavino in New York, Christiaan Hetzner in Stuttgart; Writing by Bill Tarrant; Editing by Robert Birsel)
