Tokyo Electric Power Company (TEPCO) announced on Thursday it had discovered a new leak of radioactie water at the Fukushima Dai-ichi nuclear plant . In a press conference the day following its discovery, company spokespeople confirmed that at least 430 liters (110 gallons) of contaminated water had spilled out of one of its tanks.
"Some of the water could have flowed into the sea through a ditch nearby," said TEPCO spokesman Hiroki Kawamata.
Kawamata also told reporters that the operator had detected 200,000 becquerels per liter of beta-ray emitting radioactive substances in the water, exceeding the legal limit, which is set at 30 becquerels per liter. A becquerel is one of three units used to measure radioactivity. The Associated Press agency reported that TEPCO subsequently said radiation measurements from sea water samples taken just off the plant's coast remained below detectable levels.
One of the toxic substances in the leaked water was strontium 90.
The company attributed the accident to heavy rainfall, which had filled the tank past capacity, as well as to the tank's placement on a slope, causing it to tilt and allowing its contents to spill out.
Workers discovered the leak on Wednesday night during a routine patrol of the complex.
The faulty tank is one of some 1,000 tanks erected to store water used to cool three of Fukushima's nuclear reactors, which were heavily damaged in the earthquake and tsunami of March 2011.
Thursday's announcement follows similary embarrassing TEPCO incidents this year.
In addition to reports of high radiation levels this summer, the plant operator admitted in August that 300 tons of toxic water had spilled out of one of the tanks.
Japan's nuclear regulator categorized that spill as a Level 3 event, the most serious category since the nuclear plant suffered a meltdown in March 2011 - triggered by a major earthquake and subsequent tsunami.
kms/msh (AP, AFP, Reuters, dpa)