Tokyo Electric Power Co. (9501)’s plan to manage radioactive water at its wrecked Fukushima plant may include a controlled discharge into the ocean once its toxicity is brought within legal limits, Japan’s nuclear regulator said.
Nuclear Regulation Authority Chairman Shunichi Tanaka said today the ocean dump could be necessary as the country’s government prepares to present its plan for handling tainted water at the site that’s increasing by 400 tons a day.
Managing the water used to cool melted fuel at the Fukushima plant’s reactors has become a fundamental challenge for the utility known as Tepco, which has struggled to contain a series of leaks including the loss of about 300 tons of contaminated water it reported two weeks ago.
“It is important for us to understand the need to make difficult judgments in order to avoid larger problems in the future,” Tanaka said of the possible ocean discharge during a speech to reporters in Tokyo.
Contaminant levels must be brought below accepted limits through filtration or other treatments before the water is discharged, he said.
Japan’s Nuclear Emergency Response Headquarters may present its response to the water management crisis as early as tomorrow, Deputy Chief Cabinet Secretary Katsunobu Kato said today, relaying comments made by Chief Cabinet Secretary Yoshihide Suga to lawmakers earlier.
The government wants to present a “complete package” of steps to tackle the water problem, Suga said, according to Kato.
Tepco’s challenge was further illustrated yesterday when the utility said it had found a new radioactive leak, capping its worst month since the March 2011 earthquake and tsunami caused reactors to meltdown.
The company said it had halted the contaminated water leak from a pipe near an area of high radiation levels discovered on Aug. 31. Of the hot spots found over the weekend, one recorded radiation of 1,800 millisieverts per hour around the bottom of a bolted-flange tank storing water used to cool melted reactor cores. That’s 18 times the level reported at the same spot on Aug. 22, Tepco said.
The weekend’s findings probably reflect Tepco’s beefed-up monitoring crews finding contamination that was missed earlier, former nuclear engineer Michael Friedlander said in a phone interview.
Tepco boosted the number of tank-inspection patrols from twice a day to three times a day after last month’s 300-ton leak, Yoshikazu Nagai, a company spokesman, said by phone. Patrols are increasing further to four times a day beginning today, when the number of inspection staff grows to 60 members from 10, he said.
The company also planned to install gauges on all of its tanks to monitor changes in water levels that suggest leaks, Nagai said. Those water level checks are currently done by measuring the temperature of the tanks’ outer walls, he said.
“They threw these tanks together, they’re exposed to the elements and now that they have more people looking at it with a higher degree of diligence, they’re finding leaks,” said Friedlander, who spent 13 years operating U.S. nuclear plants. “Those leaks have probably been around for quite some time and they’ve probably been growing because until now they haven’t been doing any work on them.”
Radiation levels Tepco disclosed at the weekend don’t raise an immediate concern for the general public because the site is off limits, Tetsuo Ito, head of Kinki University’s Atomic Energy Research Institute, said yesterday by telephone.
Direct exposure to 1,800 millisieverts for four hours can be lethal, but it’s not life-threatening for Tepco’s inspectors as they don’t stay in one spot for four hours, he said.
Tepco said the 1,800 millisieverts reading was found 5 centimeters above the area that was checked, falling to 15 millisieverts at 50 centimeters. The reading was for beta radiation that travels short distances and can be blocked by use of metal sheet such as aluminum, the company said on its website.
With more than 338,000 metric tons of water of varying levels of toxicity stored in pits, basements and hundreds of tanks at the Fukushima plant, Tepco has been overwhelmed in trying to contain leaks.
While the water stored in tanks has been treated to remove cesium, other radioactive elements such as strontium must be reduced before it can be discharged into the ocean, Tanaka said.
Tepco’s unit for filtering such contaminants, known as ALPS, was taken off line due to corrosion on Aug. 8, just months after beginning operation. Trade Minister Toshimitsu Motegi said last month that Tepco was being given until mid-September to restart the system.
“If we do decide to discharge into ocean, we will make every effort to ensure that contaminant levels are below the accepted limits,” Tanaka said. “One way to achieve it is to use the ALPS system, which does remove many radioactive elements.”
Prime Minister Shinzo Abe last month said Tepco isn’t able to handle the disaster recovery after the company acknowledged that contaminated groundwater at the plant was seeping into the ocean. Japanese government officials estimated that leak at 300 tons of irradiated water a day.