nuclear-news

FOCUS: Decades-long challenge to scrap Fukushima plant by 2051 in a bind. By Junko Horiuchi, KYODO NEWS – Mar 1, 2021 The decades-long challenge to scrap the Fukushima Daiichi nuclear plant, crippled by the massive earthquake and tsunami disaster that struck northeastern Japan in 2011, is becoming more complex as recent remote-controlled probes have highlighted just how damaged the reactors are.Tokyo Electric Power Company Holdings Inc., operator of the six-reactor nuclear complex, aims to scrap the plant between 2041 and 2051. But critics have cast doubts on the schedule, citing not only the extremely high radiation levels, but problems associated with delayed probes and underdeveloped robots and other technology needed to extract an estimated nearly 900 tons of melted fuel debris.

Decommissioning of the plant, scene of the world’s worst nuclear accident since the 1986 Chernobyl disaster, is crucial for Japan if it wants to stick to using nuclear power safely and show the world that the nuclear crisis is under control.

“It is likely that the roadmap will not be completed as scheduled,” said Tetsuro Tsutsui, a member of the Citizens’ Commission on Nuclear Energy, a group comprising academics and nuclear experts.

He added the “melted debris is mixed with fractured parts of buildings and concrete material and is highly radioactive, making it hard for robots to clear the debris.”

The scrapping of the plant involves the daunting decision on how to dispose of the huge amount of radioactive waste left as a byproduct. This has been made worse as no municipality offered to become the final disposal site when the plant was operating……….

“Nearly 10 years have passed following the Fukushima accident but with respect to the long decommissioning process, we are still hovering around the start line. We have a long journey ahead,” said Fukushima Gov. Masao Uchibori in a recent briefing.

“The most difficult step is the safe and stable retrieval of the debris but we don’t know what state it is in,” he added.

Despite the use of computer simulations and small-scale internal probes using remote cameras, data is scarce about the exact locations and other details of the melted fuel — crucial information to determine the retrieval methods and develop the appropriate technology and robots.

Robotic probes at the Nos. 2 and 3 units have captured images of large amounts of material that appear to be melted fuel, but attempts so far have been unsuccessful at the No. 1 unit.

TEPCO opted to start the fuel removal at the No. 2 unit as it has the best grasp of the internal conditions there but no time frame has been set for the two other units

In a setback for retrieval efforts, the company said in late December removing melted fuel from the No. 2 unit would be delayed from its initial starting period in 2021 by at least a year as the coronavirus pandemic has stalled the development in Britain of a robotic arm to be used for the extraction.

That robotic arm, however, can only extract a few grams of melted fuel debris at a time. To completely remove the hundreds of tons of melted fuel from the reactor larger machinery is required, experts say.

In another development that may affect the decommissioning process, a Nuclear Regulation Authority study group said in January a high concentration of radioactive cesium is likely to have accumulated in the lids of the containment vessels for the No. 2 and No. 3 reactors.

The regulator’s findings in a new interim report draft on the Fukushima accident came as a shock because it was previously believed that most of the radioactive material remained at the bottom of the reactors in the form of melted nuclear fuel debris……..

TEPCO, whose biggest shareholder is the Japanese government, has not given an estimate of the costs for the debris removal, which would add to the 8 trillion yen ($75 billion) already forecast for the decommissioning process.

The utility and the government have also been grappling with the buildup of radioactive water, which is generated in the process of cooling the meltdown reactors………

According to Yasuro Kawai, another member of the commission, the government’s decision to release treated water into the sea is in fact the government’s attempt to minimize the impact of the Fukushima crisis and say dismantling work is on track.

“But the roadmap is nothing but pie in the sky,” he said.

The commission says it is more logical to keep the debris inside the reactors than to retrieve it and suggests constructing a shield around the reactors and postpone taking out the melted fuel until 100 years or 200 years later when radioactive activity levels have decreased.

https://english.kyodonews.net/news/2021/03/bd5639526c13-focus-decades-long-challenge-to-scrap-fukushima-plant-by-2051-in-a-bind.html?fbclid=IwAR29Thhx8Rt2JyYT6rtadF_B7QkZmxjYVmkno0G2Nxg4xidACeCZVW2EzCw