Tokyo Electric Power Co. said it’s investigating the cause of a spike in radiation levels in drainage water that it believes subsequently leaked into the Pacific ocean from its wrecked Fukushima Dai-ichi nuclear plant north of Tokyo.
The radioactivity increase was detected on Sunday, the company said in an e-mail yesterday. No workers were exposed and tests of radiation levels in sea water in the port adjacent to the plant showed no significant increase, the company said.
Ocean water tests will be increased to daily sampling from weekly as it investigates the leak, it added.
Rainwater is believed to have become contaminated through contact with radioactive substances and then flowed into drainage ditches, a spokesperson for the Tokyo-based company said today by phone, asking not to be named because of company policy. The company is unable to estimate the size of the radioactive water leak, the person said.
Tepco, as the company is known, detected 23,000 becquerels per liter of cesium 137, from rainwater accumulated on the roof of the No. 2 reactor building, the utility said yesterday in a statement. The legal limit for releasing cesium 137 is 90 becquerels per liter.
Cesium 137 releases beta and gamma radiation and exposure to large amounts can cause acute radiation sickness and death, according to the U.S. Center for Disease Control and Prevention. Exposure also raises the risk of developing cancers.
Tepco has had repeated failures in stemming radioactive water leaks at the plant since it had three reactor meltdowns almost four years ago following an earthquake and tsunami. The nuclear disaster forced the evacuation of 160,000 people in the area.