TOKYO – Experts who investigated Japan's nuclear crisis said Monday that a watchdog's oversight of the crippled plant's operator is still too lax, amid renewed public fear over a recent spate of safety problems.
The Fukushima Dai-ichi plant has been plagued with glitches. A blackout last month, caused by a rat that short-circuited a switchboard, left the plant's fuel storage pools without cooling for more than a day. Last Friday another cooling failure occurred, and hours later the operator reported a massive contaminated water leak from underground tanks.
The plant's operator Tokyo Electric Power Co. revealed Saturday that up to 120 tons of highly contaminated water has escaped from a temporary underground tank, and a smaller amount from another tank. TEPCO said it believes the water hasn't escaped into the ocean.
Regulators asked TEPCO on Monday to determine the cause and contain the problem quickly.
But the investigators said the Nuclear Regulation Authority is only rubber-stamping TEPCO's work at the plant that still runs on makeshift equipment.
"The public is extremely concerned, especially about the latest contaminated water leak. Many people worry if it's a good idea to leave the plant up to TEPCO and the regulators," said Shuya Nomura, a lawyer who served on the 10-member investigation panel commissioned by the parliament last year. "Regulators should demonstrate they can properly carry out a decades-long decommissioning process."
Another investigator Mitsuhiko Tanaka, a nuclear engineer, said regulators routinely approved work plans submitted by the utility.
"They make a risk assessment, submit their plans to the government and they're approved," he said. "It's the same old routine."
Nine of the investigators testified at a lower house nuclear committee Monday for the first time since releasing their findings in July. The report called the March 2011 disaster "manmade," and blamed regulator-operator collusion and botched crisis management. The NRA started in September as a more independent, tougher regulator.
TEPCO is moving tons of highly radioactive water from the temporary tanks to two similar ones nearby to minimize the leak. They are among seven underground tanks in different sizes with the same design.
TEPCO admitted Sunday it had dismissed earlier signs of water loss as a margin of error and waited until a spike in radiation levels around the tanks was detected. Critics suspect cash-strapped TEPCO built poorly designed underground pits instead of safer and more manageable steel tanks to save money. TEPCO is also criticized for delaying upgrades of makeshift equipment, raising suspicions whether the plant is really under control.
The underground tanks, several times the size of an Olympic swimming pool and similar to an industrial waste dump, are dug directly into the ground and protected by double-layer polyethylene linings inside the outermost clay-based lining, with a felt padding in between each layer. Officials suspect ruptures in the linings due to the weight of the water.
Contaminated water at the plant, which went into multiple meltdowns after the March 2011 earthquake and tsunami that devastated northeastern Japan, has escaped into the sea several times during the crisis. Experts suspect a continuous leak into the ocean through an underground water system, citing high levels of contamination among fish caught in waters just off the plant.
The contaminated water in the tanks is part of more than 270,000 tons of water used to cool melted fuel at the plant's reactors damaged in the twin disasters. So much water has been used that TEPCO is struggling to find storage space. The water is also stored in hundreds of gigantic steel tanks.
NRA commissioner Toyoshi Fuketa told reporters Monday that the water leak poses a more immediate threat to the plant's water management than to the environment. He questioned TEPCO's risk evaluation in the tanks' planning stage, but acknowledged regulators have to allow TEPCO to use remaining underground tanks for now.
"Although we need more long-term plans, we have to tackle the most immediate problem first. TEPCO's decommission process is a tightrope situation to begin with," he said.