TOKYO, Feb 20 – About 100 tonnes of highly radioactive water has leaked from one of the storage tank areas at the Fukushima No. 1 nuclear power plant, its operator said Thursday.
The water contained 230 million becquerels per litre of beta ray-emitting radioactive substances such as strontium-90, Japanese news agency Jiji Press reports Tokyo Electric Power Co. (TEPCO) as saying.
“A barrier at the H6 tank area failed to prevent the water from leaving the area,” the company said.
The leak was detected around 11:25 p.m. Wednesday (2:25 p.m. GMT), when water was found to be dripping from a tank located some 700 metres west of the seawall, according to TEPCO.
The water had escaped the area through a gutter. The level of beta-ray radiation on the surface of the water was 50 millisieverts per hour.
Although an alarm signaling that the tank was almost full went off shortly after 2 p.m. Wednesday, TEPCO was unable to detect any irregularities at the time and concluded that the alarm was caused by equipment failure.
The tank has three valves through which it receives tainted water. The valves should have been closed but two of them were open, but even the closed valve was not able to stop water entering.
As a result, tainted water entered the tank and caused the leak, TEPCO said.
The company said that 13,100 becquerels of radioactive cesium were detected in a water sample collected from the gutter.
However, TEPCO said it does not believe the water made it into the ocean as no drainage was reported.
The leak was brought under control around 5:40 a.m. on Thursday.
– BERNAMA
