Radioactive water leaked from another tank at the Fukushima No. 1 nuclear plant and spilled into the ocean following bungled work to prepare for a typhoon, Tokyo Electric Power Co. said Oct. 3. (With video)
The utility estimated that about 430 liters breached the barrier surrounding the leaking tank in the B-South area and entered a drainage ditch leading to the sea.
“We believe (contaminated water) flowed into the ocean,” Masayuki Ono, acting general manager of TEPCO’s Nuclear Power and Plant Siting Division, said at an Oct. 3 news conference.
The leak occurred because the utility had pumped too much rainwater into the tank. TEPCO officials said the water likely spilled from a section connecting the top and side of the tank.
Water within the barrier surrounding the tank had levels of beta rays, including radioactive strontium, of 200,000 becquerels per liter.
The Nuclear Regulation Authority ordered TEPCO to collect the soil where the contaminated water leaked and to check the effects on the seawater.
The Fukushima prefectural government, increasingly frustrated over the lack of progress in dealing with the radioactive water problem at the nuclear plant, held an emergency meeting of high-ranking officials on the morning of Oct. 3.
“TEPCO has said it would place priority (on dealing with the contaminated water problem) and that it would inject corporate resources to deal with it, but I doubt their actions match what they have said,” Governor Yuhei Sato said.
TEPCO is struggling to bring the contaminated water problem under control. Storage space for radioactive water used to cool the reactors has long been a concern. And groundwater continues to enter reactor buildings where it mixes with the polluted water.
In August, workers discovered that about 300 tons of highly radioactive water had leaked from another tank in the H4 area of the site. Some of that water is believed to have reached the ocean as well.
The flange-type tank where the latest leak was found is one of five connected by pipes in the B-South area. The metal sheets on these tanks are secured by bolts. Each tank has a capacity of 450 tons and stores water that has been processed through purifying equipment after cooling a reactor core.
According to TEPCO officials, a large volume of rainwater had accumulated within the barrier in the B-South area on Oct. 2. Workers that day pumped the water into the tanks from 8:30 a.m. until shortly after noon to make room for additional rainwater from the approaching typhoon.
At 8:05 p.m., a worker discovered water dripping from the top part of a tank.
The tanks were filled to about 98.6 percent of capacity, leaving very little space between the top of the water and the ceiling of the tank.
Normally, water is stored at a much lower level because the sections of tank are connected only by bolts.
The B-South area is also on an incline, meaning that the tanks are tilted. Workers checked the water gauge at the tank at the highest location. Officials believe the water leaked from the tank at the lowest location.
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