TOKYO — The head of Japan’s devastated Fukushima nuclear plant says details of the damage inside its reactors are only beginning to emerge 12 years after it was hit by a massive earthquake and tsunami, which making it difficult to foresee when or how its decommissioning will be completed.
The most urgent task is to safely start releasing large amounts of treated but radioactive water from the plant into the sea, Akira Ono said in an interview with The Associated Press.
The March 2011 earthquake and tsunami damaged the cooling systems at the Fukushima Daiichi plant, causing three reactors to melt down and release large amounts of radiation. The operator, Tokyo Electric Power Company Holdings Inc., has been able to stabilize the plant to the point where the company can better plan a decommissioning strategy, which is expected to be long and extremely challenging.
“Going forward, we have to face unimaginably difficult work such as removing molten debris” from inside the reactors, said Ono, who heads the plant and is president of Fukushima Daiichi Decontamination. & Decommissioning Engineering Co.
Earlier this year, a remote-controlled underwater vehicle successfully collected a small sample from inside one of the three melted down reactors — just a spoonful of about 880 tons of highly radioactive molten fuel and other more debris that must be safely removed and stored.
The status of the waste in the main cores of the Unit 1, 2 and 3 reactors remains unknown, Ono said.
The removal of melted debris is set to begin in Unit 2 after September this year after almost two years of delay. Removal of spent fuel in Unit 1 reactor’s cooling pool is scheduled to begin in 2027 after a 10-year delay due to the need to dismantle parts of the building damaged by the hydrogen explosion.
The plant should be ready for workers to eventually concentrate on removing molten debris from the reactors after all spent fuel is removed from the cooling pools by 2031, Ono said.
The government has maintained its original goal of completing the decommissioning of the plant by 2051. But some experts say that removing all the melted fuel debris after that is impossible and suggests a Chernobyl-style burying the plant, an option that helps reduce health risks as the plant’s radioactivity gradually decreases.
“I still consider this goal as a major guidepost,” Ono said. “We cannot say what will happen in 30 years. We cannot say, but can almost imagine the next 30 years, I believe that it is necessary to carefully and accurately build the current plan to safely, consistently and easily continue decommissioning.
Before that, however, the biggest issue was the disposal of large amounts of treated but radioactive water from the plant, he said.
Water used to cool the three damaged reactors seeped into the basements of the reactor buildings and was collected and stored in about 1,000 tanks covering most of the plant’s grounds.
The government and TEPCO say the tanks need to be removed so facilities can be built for decommissioning the plant. The tanks are expected to reach their capacity of 1.37 million tons later this year.
Most of the radioactivity can be removed from the water during treatment, but tritium cannot be separated, and low levels of other radionuclides also remain. The government and TEPCO have said they will ensure that the radioactivity in the water is well below legal limits and that it will be diluted in large amounts of seawater before its planned discharge into the ocean.
Local fishing communities strongly opposed the plan, saying their damaged business would suffer more because of the negative image the water release would cause. Neighboring countries, including China and South Korea, and Pacific Island nations have also raised safety concerns.
TEPCO plans to finish building the facilities needed for the spring water discharge and then receive safety approval from nuclear regulators. A final inspection and report by an International Atomic Energy Agency mission is expected before the release begins.
The operator still needs to work on an “easy to understand” explanation and scientific evidence to help people understand the release, Ono said.
“The decommissioning of Fukushima Daiichi itself is based on the understanding and trust of everyone in society,” he said.