Tokyo Electric Power Co., manager of the stricken Fukushima nuclear plant, said Sunday it halted a slow leak from a pipe connecting two water storage tanks by patching it with tape just hours after stumbling upon a potentially lethal radioactive hot spot.
Tepco has been unable to safely contain the growing volume of water used to cool the three reactors hit by meltdowns triggered by the March 2011 earthquake and tsunami, and the government is in the process of taking over the cleanup.
The discovery of the dripping pipe came just after Tepco said late Saturday it had found hot spots at four sites near the water tanks, with one giving off 1.8 sieverts per hour — enough to kill a human being in four hours.
The other three hot spots were not detailed.
The pipe, which was leaking a drop about every 90 seconds, was sealed using absorption material and plastic tape. A puddle of giving off 230 millisieverts per hour was found below it, Tepco said.
“We have to suspect that the high radiation levels were caused by the toxic water oozing from the flange connections,” a Tepco spokesman said, adding that no conclusions had been reached.
The beleaguered utility also said it recorded 900 becquerels of tritium per liter in a groundwater interdiction well, compared with 450 becquerels per liter in February.
Since the well is near the H4 area, where a tank lost 300 tons of radioactive water last month without anyone noticing, Tepco is looking into whether the rise in tritium is related to that incident. Tritium is one of the elements Tepco’s makeshift filtering system, which is partially offline, can’t remove.
On Sunday, the utility said it logged 920 becquerels of strontium-90 per liter of liquid emitting beta rays in the drainage ditch south of H4 that leads from the tanks to the Pacific. Tepco logged 580 becquerels in the ditch on Aug. 22.
Last week, Tepco revealed that 300 tons of toxic water had disappeared from a huge tank — one of 930 on site — before anyone noticed. The spill sparked fears that the toxic water may have escaped into the ocean or seeped into the ground, and was categorized — by Japan’s Nuclear Regulatory Agency — as a Level 3 event on the International Nuclear Radiological Event Scale (INES), the most serious incident since the meltdown itself, which was rated Level 7.
The hot spots were discovered during daily inspections Saturday near three tanks and a pipe connecting them to the crippled plant.
Although it was unclear whether the hot spots indicated that a fresh spill had taken place, traces of water reading 230 millisieverts per hour were found below the pipe.
In response to growing domestic and international pressure on Tepco to stop tainting the ocean and to seek outside help, Prime Minister Shinzo Abe on Thursday promised the world that his government will play a greater role in solving the water crisis.
“The accident in Fukushima cannot be left entirely to Tokyo Electric Power. There is a need for the government to play a role with a sense of urgency, including taking measures to deal with the waste water,” he said.
Abe’s pledge came as the world’s nuclear watchdog urged Japan to explain more clearly what is happening at Fukushima and avoid sending “confusing messages” about the disaster, including the Level 3 rating.
The International Atomic Energy Agency recently questioned why last week’s 300-ton leak of radioactive water prompted the NRA to rate the event on its INES scale, when no other incident since the meltdowns had.