Groundwater laced with radiation from melted reactors at the Fukushima Dai-Ichi atomic plant north of Tokyo has been leaking into the Pacific Ocean, raising concern the toxic water has been flowing into the sea since the disaster at the facility more than two years ago.
Backtracking on previous comments, Tokyo Electric Power Co. confirmed the groundwater leaks last night, earning a rebuke from the government today to stop the leaks that Chief Cabinet Secretary Yoshihide Suga said were “serious.”
Tepco, as the utility is known, suspected the breach after finding water levels in monitoring wells moving in sync with tidal flows, spokeswoman Kaoru Suzuki said by phone today. The operator doesn’t know when the leaks started or how much radiated water has drained into the ocean, she said. Water samples suggest contamination has been contained in the port area near the Fukushima plant, Suzuki said.
“I don’t know why Tepco was so circumspect about acknowledging that there was a leak,” Jota Kanda, a professor at Tokyo University of Marine Science and Technology, said by phone today. “Most marine experts who have studied the effect of the Fukushima disaster on surrounding ocean areas hold the view that radioactive water has been leaking from the plant. It’s common sense.”
Tepco’s announcement angered fishing unions that lost fishing grounds and customers on concern radiation would contaminate catches and enter the food chain. In August last year, the utility found record high levels of radioactive cesium in fish it caught for tests within 20 kilometers of the coast from the nuclear plant.
“Tepco could have told us at least about the possibility of the leaks,” Yoshihisa Kobayashi, an official at the Fukushima Prefectural Federation of Fisheries Co-operative Associations, said by phone today. “I’ve always suspected there may be leaks because radiation levels inside silt fences have remained high though Tepco told us there is no such leak.”
Fish contamination concerns have spread beyond Japan.
A study of 15 Pacific bluefin caught off San Diego in August 2011 found radioactive cesium 10 times higher than in fish caught in previous years.
That provides “unequivocal evidence” that the radiation came from Fukushima, researchers including Daniel Madigan and Nicholas Fisher said in a study published in May 2012 in the Proceedings of the National Academy of Sciences. The level of contamination was not a danger to humans, the study said.
Find the Leak
The finding comes in the same month Japan’s Nuclear Regulation Authority told Tepco to speed up completion of a seawall to block contaminated water that it suspected was leaking into the ocean. While reporting elevated levels of cesium 137 and 134 in the plant’s groundwater, the utility had maintained that there had been no apparent effect on the adjacent seawater.
The pace of decline in radiation levels slowed in the waters beside the Fukushima plant after June 2011, suggesting that there was a leak, said marine science professor Kanda, whose findings are being reviewed for publication in the journal Biogeosciences.
Tepco needs to pinpoint the source of the leak before it can come up with credible measures to stop it, he said.
Reports differ on how much radiation escaped into the atmosphere and the sea after the Fukushima disaster.
The Atmospheric Chemistry and Physics journal in October 2011 estimated the radiation released was about 42 percent of the 1986 nuclear accident at 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. Tepco in May last year estimated the total radiation release was about 17 percent of Chernobyl.
Human exposure to radiation at moderate to high levels can lead to cancers, such as leukemia, according to the United Nations Scientific Committee on the Effects of Atomic Radiation. The body, known as UNSCEAR, is in charge of the most comprehensive study of the Fukushima disaster and is expected to deliver its report to the UN in October this year.
Tepco also said in an e-mailed statement today that steam from an unknown source that was first spotted near the fifth floor of the Fukushima plant’s No. 3 reactor building on July 18 was seen again around 9 a.m. By 1:30 p.m., it was no longer visible, the company said.
The steam was probably the result of atmospheric moisture evaporating against the outer wall of the containment vessel, which is warmer than air temperatures, spokesman Yusuke Kunikage said by phone.
The utility found no significant changes to the unit’s containment vessel temperature and other readings, it said in the statement.
The handling of highly radioactive water is an issue that has vexed Tepco as the utility oversees the plant’s cleanup. Leaks in April raised the prospect the utility would be forced to dump radioactive water in the Pacific.
Last month, Tepco said it had found unsafe levels of radioactivity in groundwater at the Fukushima station. The contaminants were found at a monitoring well in a turbine complex at the Dai-Ichi plant.
While the current findings marked the first time the utility has acknowledged that contaminated groundwater was seeping into the ocean, it has had other leaks of radioactive water at the plant. 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.
The groundwater leakage is a reminder of the complexities facing Tepco as it mops up the aftermath of the Fukushima disaster.
Tepco shares fell 6.7 percent to 656 yen at the close on the Tokyo Stock Exchange, the biggest decline since July 3.