Japan to raise Fukushima radioactive leak alert level to "serious incident"

21 August 2013

Japan’s Nuclear Regulation Authority (NRA) has proposed that the leakage of radioactive water at the Fukushima Dai-ichi nuclear power plant be termed a "serious incident" rather than "an anomaly". This raises the rating of the leak to Level 3 from Level 1 on the International Nuclear and Radiological event scale (INES) of 0 to 8.

Tokyo Electric Power Co (TEPCO), the operator of the plant, said about 300,000 litres of contaminated water has leaked from one of the steel tanks around the wrecked plant, built quickly after the meltdown at the plant to contain water used to cool the radioactive cores.

The watchdog said it plans to consult with the UN nuclear regulatory agency over whether it is appropriate to use the INES evaluation scale at the plant.

TEPCO said that because the tank is about 100 metres from the coastline, the leak does not pose an immediate threat to the sea. But an NRA spokesman said the authority was extremely concerned.. He urged TEPCO to quickly determine the cause of the leak and its possible effect on water management plans.

TEPCO spokesman Masayuki Ono said the leaked water seeped into the ground after largely escaping piles of sandbags added to a concrete barrier around the tank.

Four other tanks of the same design have had similar leaks since last year. The incidents have shaken confidence in the reliability of hundreds of tanks that are crucial for storing what has been a continuous flow of contaminated water.

The water's radiation level, measured less than a metre above the puddle, was about 100 millisieverts per hour -- the maximum cumulative exposure allowed for plant workers over five years, Ono said.

The plant suffered multiple meltdowns following a massive earthquake and tsunami in March 2011 -- a Level 7 "major accident" on the INES rating and the worst since Chernobyl in 1986.

Hundreds of tanks were built around the plant to store massive amounts of contaminated water coming from the three melted reactors, as well as underground water running into reactor and turbine basements.

Ono said the latest leak was by far the worst from a steel storage tank in terms of volume. The previous four cases involved leakages of only a few litres.

TEPCO says the tanks that have leaked use rubber seams that were intended to last about five years. Ono said TEPCO plans to build additional tanks with welded seams that are more watertight, but will still have to rely on ones with rubber seams.

About 350 of some 1,000 steel tanks built across the plant complex containing nearly 300 million litres of partially treated contaminated water are less-durable ones with rubber seams.

"We have no choice but keep building tanks, or there is no place to store the contaminated water," Ono said.

The massive amount of radioactive water is among the most pressing issues affecting the cleanup process, which is expected to take decades.

The contaminated water is recycled as reactor cooling water, but its volume grows by 400,000 litres a day because of underground water inflow. TEPCO plans to secure storage facilities capable of holding 800 million litres by 2015.

The public is growing frustrated with the company's failure to contain and clean up the mess.
“TEPCO’s actions are reactive and slow,” Kiyoshi Takasaka, a member of a committee of nuclear experts advising Fukushima prefecture, told the Japanese media. Other members of the committee complain that TEPCO has not got a convincing containment plan.

NRA Chairman Shunichi Tanaka likened the stricken nuclear plant to a house of horrors at an amusement park. "I don't know if describing it this way is appropriate, but it's like a haunted house and, as I've said, mishaps keep happening one after the other," he told reporters. "We have to look into how we can reduce the risks and how to prevent it from becoming a fatal or serious incident."