Tokyo Electric Power Co. said higher radiation readings recorded this week in ditch water at its Fukushima Dai-Ichi nuclear plant are likely caused by recent heavy rains washing contaminated dirt into the area.
Water samples taken yesterday at a ditch had beta radiation levels of 140,000 becquerels per liter, or more than twice the 59,000 becquerels found on Oct. 22 in the same place, the utility known as Tepco said today in an e-mailed statement.
The Japan Meteorological Agency’s Fukushima monitoring station recorded 200.5 milliliters (7.9 inches) of rainfall so far this month, more than the total for any October since 2006.
The ditch water readings are 14,000 times the limit for drinking water under health ministry guidelines, though far below the 80 million becquerels found in water spilled from a nearby storage tank in August. That incident prompted the nuclear regulator to raise its alert level and forced the government to say it would take a bigger role in management of the plant, crippled by the March 2011 earthquake and tsunami.
Water samples from another ditch had readings of 15,000 becquerels of beta radiation, again higher than the record 2,200 becquerels in an Oct. 1 sample from the same site, Tepco said. Beta radiation includes strontium-90 linked to causing cancers such as leukemia.
Tepco said in a separate release that beta radiation levels of 510,000 becquerels per liter were found Oct. 20 in a sample of rainwater that had accumulated between a storage tank and a cement barrier built to contain leaks.
That compares to 450,000 becquerels on Oct. 19 and 360,000 becquerels on Oct. 18, the company said. The Oct. 20 sample was the highest taken so far from within the barrier, the Sankei newspaper reported.
Nuclear Regulation Authority Chairman Shunichi Tanaka told agency commissioners yesterday that he planned to meet Tepco President Naomi Hirose, saying that the company’s reports on “careless mistakes” at the plant doesn’t resolve issues.
Six cleanup workers at the atomic station were exposed to radiation earlier this month after a hose was mistakenly removed from a filtration system. It was the third mishap in two weeks that Tepco attributed to mistakes by workers.