Radioactive Fukushima water 'leaking into ocean'
The stricken nuclear power plant at Fukushima has probably been leaking contaminated water into the ocean for two years, ever since an earthquake and tsunami badly damaged the plant, Japan's chief nuclear regulator said.
In unusually candid comments on Wednesday, Shunichi Tanaka, the head of the Nuclear Regulation Authority, also said that neither his staff nor the plant's operator knew exactly where the leaks were coming from, or how to stop them.
The operator, Tokyo Electric Power Co (Tepco), has reported sharp increases in the amounts of radioactive caesium, tritium and strontium detected in groundwater at the plant, adding urgency to the task of sealing any leaks.
Radioactive caesium and strontium, especially, are known to raise risks of cancer in humans.
Tanaka's comments highlight the precariousness of the clean-up at the Fukushima Daiichi Nuclear Power Plant, where core meltdowns occurred at three of the six reactors.
A critical problem has been the groundwater that has been pouring into the basements of the damaged reactor buildings and becoming contaminated.
Until recently, Tepco flatly denied any of the water was leaking into the ocean, even though various independent studies of radiation levels in the nearby ocean have suggested otherwise. In recent days, Tepco has retreated to saying it was not sure whether there was a leak.
Tanaka said the evidence was overwhelming.
"We've seen for a fact that levels of radioactivity in the seawater remain high, and contamination continues - I don't think anyone can deny that," he said.
"We must take action as soon as possible. That said, considering the state of the plant, it's difficult to find a solution today or tomorrow."
Tepco said in the past that the stricken plant was having "no significant impact" on the marine environment.
"We can't say anything for sure," said Noriyuki Imaizumi, a Tepco spokesman.
"But we aren't just sitting back. We are first analysing why there have been high radiation measurements in recent weeks."
The struggle to seal the plant has overshadowed the push to restart Japan's other nuclear power stations, which were shut in after the Fukushima disaster.