Irradiated water at Tokyo Electric Power Co. (9501)’s Fukushima plant will probably have to be dumped into the ocean after contamination is brought to safe levels, an adviser to the company’s water management task force said.
The ocean release will be necessary because water can’t be stored in tanks indefinitely at the Dai-Ichi station after being used to cool the plant’s overheating reactor fuel, Lake Barrett, a former official with the U.S. Nuclear Regulatory Commission, wrote in a Sept. 9 opinion piece posted on the website of the Bulletin of Atomic Scientists.
The article by Barrett, who’ll be advising the utility known as Tepco on water management at the site, could offer clues to its strategy for handling the 338,000 metric tons of contaminated water stored in more than 1,000 tanks at the plant. That amount is increasing by about 400 tons a day.
“Spending billions and billions of yen on building tanks to try to capture almost every drop of water on the site is unsustainable, wasteful, and counterproductive,” Barrett wrote. “I see no realistic alternative to a program that cleans up water with improved processing systems so it meets very protective Japanese release standards and then, after public discussion, conducts an independently confirmed, controlled release to the sea.”
Tepco set up the Contaminated Water and Tank Countermeasures Headquarters last month after reporting a 300 ton leak at one of the tanks, which Japan’s Nuclear Regulation Authority designated as the worst accident since the March 2011 earthquake and tsunami caused meltdowns at the site. The company is also struggling to stem the leak of contaminated groundwater into the Pacific Ocean, which the government has estimated at about 300 tons per day.
Barrett, who directed cleanup operations at Three Mile Island for the Nuclear Regulatory Commission for four years after the 1979 accident at the U.S. plant, is scheduled to meet with task force staff tomorrow to offer advice on plant decommissioning and water management, Tepco said in a Sept. 10 statement.
He didn’t immediately respond to an e-mail today asking whether his position outlined in the opinion piece represented the advice he would be giving to Tepco.
The possibility of an ocean dump of stored water after treatment was also raised last week by Nuclear Regulation Authority Chairman Shunichi Tanaka. JF Zengyoren, a union of Japanese fisheries cooperatives, later said such a discharge would be unacceptable, even if contamination levels were brought below legal limits for ocean dumping.
Fishing Groups Object
Tepco is also seeking fishermen’s groups’ permission for a pipeline that would channel groundwater around the Fukushima plant’s reactors and into the ocean to cut the volume of radioactive water it must manage.
The plan has been complicated by the detection of irradiated groundwater in an area near storage tanks that had been thought free of contaminants. Inspectors have been finding higher amounts of the contaminant tritium in the area, despite a decrease in levels of beta radiation, which includes strontium-90.
Beta radiation levels at one well near the tank where last month’s leak occurred fell from 3,200 bequerels per liter on Sept. 8 to 2,000 bequerels on Sept. 10, while tritium levels surged from 4,200 bequerels to 64,000 bequerels to exceed safety guidelines, Mayumi Yoshida, a Tepco spokeswoman, said today by phone.
Safety limits covering sea water near the plant require levels of strontium-90 to remain below 30 bequerels, while tritium must stay below 60,000 bequerels. The company was investigating why levels of one were rising while others declined. Strontium-90 has been linked to bone cancer
Tepco needs local fishermen to approve their plan to pump groundwater flowing toward the plant directly into the ocean. The objective is to cut the quantity of water flooding reactor building basements. Since the groundwater would pass through the plant’s tank areas before entering the bypass system’s intake wells, the tainted water could pose a contamination risk, Tepco has said.
Beta radiation levels of 9,500 bequerels per liter were found at a monitoring well yesterday near the plant’s No. 1 turbine building in a separate area of the plant from the tanks, Tepco said today in a statement.
The newly dug well was tested as part of Tepco’s efforts to find the source of contamination in water flooding a sub-drain system designed to keep some groundwater out of reactor basements, Yoshida said. The company hopes by March 2015 to restore the system, which was damaged in the 2011 disaster, she said.
With the bypass pipe and sub-drain system in operation, the utility would be able to reduce the amount of groundwater entering the reactor basements from 400 tons per day to about 50 tons, Yoshida said.
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