China says it is “shocked” to learn radioactive water is still leaking from the Fukushima nuclear plant, as it is revealed 300 tonnes of contaminated liquid has escaped from a tank.
Japan’s nuclear watchdog said on Wednesday that it is “extremely concerned” after around 300 tonnes of radioactive water leaked from a steel tank.
The Nuclear Regulation Authority is considering raising the rating of the leak to “a serious incident” after the water escaped at the Fukushima Dai-ichi plant.
Responding to the incident, the Chinese government expressed surprise that leaks were still taking place.
China “hopes that the Japanese side can earnestly take effective steps to put an end to the negative impact of the after-effects of the Fukushima nuclear accident,” the foreign ministry said in a statement.
Tokyo Electric Power Company (TEPCO), the operator of the site, said it did not know how the leak, from one of hundreds of tanks that hold hundreds of thousands of tonnes of water, occurred.
The company said it suspects the water escaped through a seam on the tank or a valve connected to a gutter.
Concerns will now be raised that the water, which has been partially treated, will make it to the ocean.
TEPCO said there was no immediate threat because the tank is about 100 metres from the coastline. However, a watchdog spokesman, Hideka Morimoto, said water could reach the sea via a drain.
“We are extremely concerned,” Mr Morimoto told reporters on Wednesday. He urged TEPCO to quickly determine the cause of the leak and its possible effect on water management plans.
The watchdog will consult with the UN before raising the rating of the incident, he said.
Workers are now pumping out a large puddle of the contaminated water and will transfer it to other tanks. However, their work is under pressure from forecasts of heavy rain in the area later on Wednesday.
The water’s radiation level, measured two feet above the puddle, was about 100 millisieverts per hour, the same as the maximum cumulative exposure allowed for plant workers over five years, TEPCO spokesman Masayuki Ono said.
The massive amount of radioactive water at Fukushima is among the most pressing issues affecting the cleanup process, which is expected to take decades.
Around one thousand tanks have been built to contain the water from three reactors, as well as underground water that is contaminated when it runs into reactor and turbine basements.
However, 350 of these tanks, holding 300,000 tonnes of water, are less durable than others, with rubber seams.
“We have no choice but keep building tanks, or there is no place to store the contaminated water,” Mr Ono said.
TEPCO has been unable to prevent some of the radioactive water reaching the ocean – hundreds of tonnes of the water runs into the Pacific Ocean each day, it is understood, and is largely made up of ground surface water mixed with untreated radioactive water.
However, the current leak is the worst of its kind in terms of volume to hit the clean-up operation, TEPCO said. There have been four previous cases of leaks, but each one was only up to ten litres of water, Mr Ono said.
Fukushima suffered multiple meltdowns following a massive earthquake and tsunami in March 2011.