From the Guardian : Highly radioactive water seeping into the ocean from Japan‘s crippled Fukushima nuclear plant is creating an “emergency” that the operator is struggling to contain, according to the country’s nuclear watchdog.
The contaminated groundwater had breached an underground barrier, was rising towards the surface and exceeded legal limits of radioactive discharge, said Shinji Kinjo, head of a Nuclear Regulatory Authority (NRA) taskforce. Countermeasures planned by Tokyo Electric Power Co (Tepco) were only a temporary solution, he said.
Tepco’s “sense of crisis is weak”, Kinjo said. “This is why you can’t just leave it up to Tepco alone [to deal with the situation].
“Right now, we have an emergency.”
Tepco has been widely castigated for its failure to prepare for the 2011 tsunami and earthquake that devastated its Fukushima plant, as well as being lambasted for its inept response to the reactor meltdowns. It has also been accused of covering up shortcomings.
It was not immediately clear how much of a threat the contaminated groundwater could pose. In the early weeks of the disaster the Japanese government allowed Tepco to dump tens of thousands of tonnes of contaminated water into the Pacific as an emergency measure.
The toxic water release was heavily criticised by neighbouring countries as well as fishermen and the utility has since promised not to dump irradiated water without the consent of local townships.
“Until we know the exact density and volume of the water that’s flowing out I honestly can’t speculate on the impact on the sea,” said Mitsuo Uematsu, of the Centre for International Collaboration, Atmosphere and Ocean Research Institute at the University of Tokyo.
In the US, across the Pacific, there was no sense of alarm. “With the amount of dilution that would occur, any kind of release in Japan would be non-detectable here,” said David Yogi, spokesman for the US Environmental Protection Agency.
Tepco said it was taking measures to prevent contaminated water from leaking into the bay near the plant. In an emailed statement to Reuters a company spokesman said Tepco deeply apologised to residents in Fukushima prefecture, the surrounding region and the larger public for causing inconveniences, worries and trouble.
The utility pumps out 400 tonnes a day of groundwater flowing from the hills above the Fukushima Daiichi nuclear plant into the basements of the destroyed buildings. There it mixes with highly irradiated water that is used to cool the reactors and maintain a stable state below 100C (32F).
Tepco is trying to prevent groundwater from reaching the plant by building a bypass but recent spikes of radioactive elements in seawater have prompted the utility to reverse months of denials and finally admit that tainted water is reaching the sea.
In an effort to prevent more leaks into the bay of the Pacific Ocean plant workers created the underground barrier by injecting chemicals to harden the ground along the shoreline of the No 1 reactor building. But that barrier is only effective in solidifying the ground at least 1.8 metres below the surface.
By breaching the barrier the water can seep through the shallow areas of earth into the nearby sea. More seriously, it is rising towards the surface – a break of which would accelerate the outflow.
“If you build a wall, of course the water is going to accumulate there. And there is no other way for the water to go but up or sideways and eventually lead to the ocean,” said Masashi Goto, a retired Toshiba Corp nuclear engineer who worked on several Tepco plants. “So now, the question is how long do we have?”
Contaminated water could rise to the ground’s surface within three weeks, the Asahi Shimbun newspaper said on Saturday. Kinjo said the three-week timeline was not based on NRA’s calculations but acknowledged that if the water reached the surface “it would flow extremely fast”.
A Tepco official said on Monday that the company planned to start pumping out a further 100 tonnes of groundwater a day by the end of the week.
The regulatory taskforce overseeing accident measures of the Fukushima Daiichi nuclear power station, which met on Friday, concluded that new measures are needed to stop the water from flowing into the sea that way, Kinjo said.
Tepco said on Friday that a cumulative 20tn to 40tn becquerels of radioactive tritium had probably leaked into the sea since the disaster. The company said this was within legal limits. A becquerel is a measure of the release of radioactive energy.
Tritium is far less harmful than caesium and strontium, which have also been released from the plant. Tepco is scheduled to test strontium levels next.
Tepco said on Monday that caesium levels at an observation post 53 metres from the sea had jumped in the past week. Readings for caesium-134 were almost 15 times higher at 310 becquerels a litre.
Caesium-137, with a half-life of 30 years, was also 15 times higher than it had been five days ago at 650 becquerels a litre. A much larger spike in radioactive caesium in July in a different well led to Tepco overturning months of denials and admitting that radioactive water had been leaking into the sea.