too early to predict dismantling
The March 2011 earthquake and tsunami damaged the cooling systems at the Fukushima Daiichi power plant, melting three reactors and releasing 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 difficult.
“In the future, we will face inconceivably difficult tasks such as recovering melted debris” inside the reactors, said Ono, who runs the plant and is president of Fukushima Daiichi Decontamination & Decommissioning Engineering Co. .
Earlier this year, a remotely operated underwater vehicle managed to collect a tiny sample inside one of three melted reactors – just a spoonful of around 880 tonnes of highly radioactive molten fuel and other debris that must be removed and stored safely.
The condition of the debris in the primary containment chambers of Units 1, 2 and 3 reactors remains largely unknown, Ono said.
Removal of molten debris is scheduled to begin in Unit 2 after September this year, after a delay of nearly two years. Removal of spent fuel in the Unit 1 reactor 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 hydrogen explosions.
The plant should be ready for workers to finally focus on clearing molten debris from reactors after all spent fuel is removed from cooling pools by 2031, Ono said.
The government is sticking to its original target of completing the decommissioning of the plant by 2051. But some experts say it is impossible to remove all the melted fuel debris by then and suggest burying the plant Chernobyl-style, an option that could help reduce health risks while the plant’s radioactivity gradually decreases.
“I still see this goal as a major benchmark,” Ono said. “We cannot say what will happen in 30 years. We cannot say, but roughly imagining the next 30 years, I think it is necessary to carefully and precisely build the current plan in order to carry out the dismantling in a safe, regular and rapid manner.
Before that, however, the biggest problem is the removal of large amounts of treated but still 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 approximately 1,000 tanks that cover much of the plant’s grounds.
The government and TEPCO say the tanks must be removed so that facilities can be built for the dismantling of the plant. The tanks are expected to reach their capacity of 1.37 million tonnes later this year.
Most of the radioactivity can be removed from the water during treatment, but tritium cannot be separated and low levels of some other radionuclides also remain. The government and TEPCO say they will ensure the water’s radioactivity is well below legal limits and will dilute it with large amounts of seawater before its planned discharge into the ocean.
Local fishing communities fiercely opposed the plan, saying their already damaged business would suffer more due to the negative image caused by the water release. Neighboring countries, including China and South Korea, and Pacific island nations have also raised security concerns.
TEPCO expects to complete the construction of the facilities needed to discharge the water in the spring and then receive safety approval from nuclear regulators. A final inspection and report from 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 statement, Ono said.
“The dismantling of Fukushima Daiichi itself is based on the understanding and trust of everyone in society,” he said.
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