We don't know what caused it

April 13, 2013

TEPCO yet to nail down cause of radioactive leaks at Fukushima plant

http://mainichi.jp/english/english/newsselect/news/20130413p2g00m0dm053000c.html

TOKYO (Kyodo) -- The operator of the crippled Fukushima No. 1 Nuclear Power Plant said Friday it has failed to find out why radioactive water leaked from underground tanks during visual checks of an area suspected to have been the cause of the incidents.

Workers removed part of the soil covering one of the troubled tanks and checked an area where a leak detection pipe, installed close to the tank, pierces though a water-containment sheet. But they could not find any irregularities there, plant operator Tokyo Electric Power Co. said.

"We have no choice but to think that the leakage occurred at another place in the case of the No. 2 tank,"TEPCO spokesman Masayuki Ono said at a press conference, while noting that junctions of water-containment sheets located around the tank could be seen as other suspicious areas.

But he added that even if there are holes in the water-containment sheets, they are unlikely to be large because the amount of water accumulating inside the pipe has been small.

To contain contamination caused by the leaks, TEPCO is collecting the polluted water that has flowed into the pipe and returning it to the tank again.

Workers cannot go inside the 6-meter-deep tank to directly find out the cause partly because it is contaminated with radioactive substances, according to Ono.

TEPCO has seven underground tanks and some of them store part of the huge amounts of radioactive water resulting from continuing water injections into the Nos. 1 to 3 reactors, which experienced meltdowns in the 2011 nuclear crisis.

The water in the underground tanks has passed through a water-processing facility for the removal of cesium, but it is still contaminated with other radioactive substances. Three such tanks have been found to be leaky.

TEPCO plans to remove all the heavily contaminated water currently stored inside the underground tanks to other reliable containers installed above the ground.

According to TEPCO, radioactive substances were not observed in groundwater at the plant's three locations about 300 and 500 meters away from the troubled tanks toward the direction of the Pacific Ocean.