Tepco admits the underground tanks are "not reliable"
TOKYO—The operator of Japan’s crippled nuclear power plant said Tuesday that it had detected a fresh leak of radioactive water from one of the facility’s storage tanks.
Tokyo Electric Power Co. (Tepco) previously said two of seven huge underground tanks at the Fukushima Dai-ichi plant had been leaking since Saturday if not earlier.
The latest leak involves a tank that was being used to take water from one of the two that were leaking, Tepco spokesman Masayuki Ono said. Up to 120 tons might have leaked from one of the tanks and smaller amount from the other two, but none of the radioactive water was believed to have reached the ocean, he said.
Tepco has halted the transfer of water to the third tank, diverting it to a fourth tank that remains intact. Two of the seven tanks are currently unused.
Ono said Tepco has decided to stop using the two most damaged of the three leaking tanks as soon as they are emptied, but will use the other because of a tank shortage.
“We admit that the underground tanks are not reliable,” Ono said. “But we must keep using some of them that are relatively in good shape while monitoring them closely. We just don’t’ have enough tanks on the ground that can accommodate the water.”
The tanks are crucial to the management of contaminated water used to cool melted fuel rods at the plant’s reactors, which were damaged in March 2011 by an earthquake and tsunami. They have since stabilized significantly but the melted fuel inside must be kept cool with water, which leaks out of the reactors’ holes and ruptures and flows into basement areas. Plant workers are scrambling to find extra tanks at the plans and believe they can find space from unused containers and underground tanks.
The plant is being decommissioned but continues to experience glitches. A fuel storage pool temporarily lost its cooling system Friday, less than a month after the plant suffered a more extensive outage caused by a rat that short-circuited a switchboard, cutting off power to four storage pools for fuel rods and other key facilities.
The spate of problems has triggered public outcry and renewed doubts about the plant’s safety. Tepco resident Naomi Hirose headed to Fukushima on Tuesday to inspect the latest problems and address the concerns. Regulatory officials said Tepco was too slow in detecting earlier signs of leaks and disclosing the problems.
The underground tanks, all built by Maeda Corp., come in different sizes, including one the size of an Olympic-size swimming pool and similar to an industrial waste dump, are dug into the ground and protected by two layers of polyethylene linings inside the outermost clay-based lining, with a felt padding in between each layer.
Ono said Tepco hasn’t determined the cause of the leak, but cited a hole or a partial detachment of the linings as a possibility. Regulators also suspect a design problem of the underground tanks, which Tepco allegedly chose as cheaper option to steel tanks to save money.