Tokyo Electric Power Co.’s discovery of leaks in water storage pits at the wrecked Fukushima atomic station raises the risk the utility will be forced to dump radioactive water in the Pacific Ocean.
Leaks were found in three of seven pits in the past week, reducing the options for moving contaminated water from basements of reactor buildings. Water in the basements is from the months after the earthquake and tsunami disabled the plant two years ago, when disaster teams used hose pipes and pumps to try and cool the reactors.
While the company has since built a makeshift sealed cooling system, underground water is breaching basement walls at a rate of about 400 tons a day and becoming contaminated, according to Tepco’s estimate. With Japan’s rainy season approaching, contaminated water levels are likely to increase at the plant 220 kilometers (137 miles) northeast of Tokyo.
Reducing radiation levels in the water and pouring it into the sea is one of two options the utility has, said Kazuhiko Kudo, a research professor of nuclear engineering at Kyushu University. The other option is “to keep building above-ground storage tanks,” said Kudo. That’s a fight Tepco can’t win without stopping the underground water pouring into the basements, Kudo said.
“It is like a well. No matter how much water you draw from a well, underground water keeps seeping into the well,” said Kudo, who also served on a safety advisory board for the Fukushima plant after the disaster for the now defunct Nuclear and Industrial Safety Agency.
Not Ruled Out
Officials at the utility known as Tepco, including President Naomi Hirose, have said the company won’t “easily” release radiated water into the ocean, indicating it’s not ruling out the possibility if it runs out of storage.
The utility plans to have 450,000 tons of above-ground tank capacity by the end of September and 700,000 tons by mid-2015, Japan’s trade ministry said in a statement today.
“It’s obvious Tepco cannot keep storing water forever as it increases by 400 tons a day,” said Hideyuki Ban, co-director of the antinuclear group Citizens’ Nuclear Information Center. That’s why the company won’t rule out discharge into the sea, Ban said in a telephone interview.
Tepco has had leaks of radioactive water at the plant before. In April last year, it said as much as 12 tons of radioactive water had leaked from a pipe and may have poured into the sea. That followed a leak at the same pipeline 11 days earlier.
Yesterday, Tepco reported another leak of radiated water, this time from a pipe.
Reports differ on how much radiation escaped from the Fukushima plant, with Tepco in May last year estimating it was about 17 percent of that released from the 1986 nuclear accident at Chernobyl.
In October 2011, the Atmospheric Chemistry and Physics journal estimated the radiation released at about 42 percent of Chernobyl and that most of it fell into the North Pacific Ocean. In the same month, the Institute for Radiological Protection and Nuclear Safety, which is funded by the French government, said the Fukushima plant was responsible for the biggest discharge of radioactive material into the ocean in history.
Next month, the United Nations Scientific Committee on the Effects of Atomic Radiation, or UNSCEAR, is expected to issue the first global and independent assessment of the Fukushima nuclear accident, including how much radiation was released and where it went, according to its website.
Human exposure to radiation at moderate to high levels can lead to cancers, such as leukemia, according to UNSCEAR.
Pacific bluefin tuna caught off San Diego in August 2011 was found to contain radioactive cesium 10 times higher than fish seized in previous years, researchers including Daniel Madigan and Nicholas Fisher said last May. The radiation levels, which the group said don’t pose a danger to public health, are expected to decline over time, they said in a study at the time.
Fishermen fear more people would hesitate to buy fish and shellfish caught off Fukushima if Tepco again releases radioactive water into the ocean, said Kenji Nakada, an official at the Fukushima Prefectural Federation of Fisheries Co-operative Associations.
“We are against the release of water even if Tepco cleans contaminated water” by removing radioactive substances, Nakada said in an phone interview. “Any release of water that has been used for cooling is not acceptable.”
On March 30, Tepco started test runs of equipment that the operator says can remove 62 kinds of radioactive substances. Still, the purification system called ALPS can’t remove tritium, a hydrogen isotope. The water processing system has also had problems and was temporarily halted last week because of incorrect operation.
The government will set up a special committee to discuss measures to help Tepco deal with radioactive water at Dai-Ichi, the trade and industry ministry said in a statement today.
An extended period of time may be needed to come up with measures to stop the influx of underground water and remove radioactive tritium, Yojiro Hatakeyama, director of the trade ministry’s nuclear energy policy planning division, told reporters in Tokyo today.
“When we reach a stage where the water contains no radioactive substances after removing tritium, we will properly handle it,” Hatakeyama said. “We haven’t decided whether the water will be released into the sea after that.”
Currently, about 280,000 tons of highly radioactive water is stored at the Fukushima plant, according to Tepco’s latest data. That’s enough to fill about 112 Olympic-sized swimming pools, according to Bloomberg News calculations.
To store the water, Tepco dug underground pits lined with three layers of waterproof sheet to prevent seepage into the surrounding soil, according to the utility.
The same method is used in industrial waste disposal, said Koji Kumagai, a geotechnical engineering professor at the Hachinohe Institute of Technology.
A design flaw is unlikely to have caused the leaks as the method is used around the world, Kumagai said in an phone interview. “The question is whether Tepco properly inspected equipment and carried out tests before pouring radioactive water into the pits.”
Tepco is still investigating the cause of leaks, President Hirose told reporters on April 10. The operator plans to keep using one of the underground pits that is leaking as it doesn’t have enough additional space, he said.
More above-ground storage tanks are scheduled to be built by the end of next month to transfer radioactive water from the leaking pits before Japan’s rainy season begins, Hirose said. The rainy season, which typically runs from June to July in Japan, would cause an increase in underground water flowing into the basements of plant buildings, he said.
“Regardless of whether we had the leaks, we will properly manage the issue and never easily discharge contaminated water into the sea,” Hirose said. “We will employ all available means to manage it.”