11 years later, fate of Fukushima reactor cleanup uncertain

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OKUMA, Japan (AP) — Eleven years after the Fukushima Daiichi nuclear power plant was ravaged by a meltdown following a massive earthquake and tsunami, the plant now looks like a sprawling construction site. Most of the radioactive debris blown up by the hydrogen explosions has been cleaned up and the torn buildings have been repaired.

During a recent visit by Associated Press reporters to see first-hand the cleanup of one of the world’s worst nuclear meltdowns, helmeted men wore regular work clothes and surgical masks, instead of coveralls. hazmat protection and full-face masks, as they dug near a recently reinforced ocean levee.

Workers were preparing for the planned construction of an Olympic-sized swimming pool pit to be used in a highly controversial plan set to begin in the spring of 2023 to phase out treated radioactive water – now exceeding 1.3 million tonnes stored in 1,000 tanks – then officials can make way for other facilities needed to dismantle the plant.

Despite the progress, massive amounts of radioactive molten fuel remain inside reactors. There are concerns about the fuel because its condition is still unknown, even to those responsible for the cleanup.

Nearly 900 tons of molten nuclear fuel remain inside the three damaged reactors, and its removal is an unprecedented challenge involving 10 times the amount of damaged fuel removed during the cleanup of Three Mile Island after the partial core meltdown in 1979 .

The government has drawn up a dismantling roadmap aiming to be completed in 29 years.

The challenge of removing melted fuel from reactors is so daunting that some experts now say setting a completion target is impossible, especially since officials still have no idea where to store the fuel. waste.

Nuclear Regulatory Authority Chairman Toyoshi Fuketa recently said that more time would be needed to determine where and how highly radioactive waste removed from reactors should be stored.

Japan does not have a final disposal plan, even for highly radioactive waste that comes out of normal reactors. Twenty-four of the country’s 60 reactors are slated for decommissioning, mainly because of the high cost needed to meet safety standards put in place following the Fukushima disaster.

On March 11, 2011, a magnitude 9.0 earthquake caused a 17-metre (56 ft) high tsunami that slammed into the coastal power station, destroying its power and cooling systems, causing the reactors to melt #1, 2 and 3 and spitting out massive amounts. of radiation. Three other reactors were offline and survived, although a fourth building suffered hydrogen explosions.

The spread of radiation prompted the evacuation of some 160,000 residents. Parts of the surrounding neighborhood are still uninhabitable.

Molten cores from Units 1, 2, and 3 largely fell to the bottom of their primary containment vessels, along with control rods and other equipment, some penetrating or possibly mixing with the concrete foundation, rendering the extremely difficult to clean.

Probes for molten fuel must rely on remote-controlled robots carrying equipment such as cameras and dosimeters – which measure radiation – because radiation levels in these areas are still lethally high for humans.

In February, a remote-controlled submersible robot entered Unit 1’s primary containment vessel, its first internal probe since a failed attempt in 2017. It captured limited footage of what are believed to be fuel mounds fade rising from the concrete floor.

The probes advanced to Unit 2, where TEPCO plans to send an extendable robotic arm later this year to collect samples of molten fuel.

TEPCO’s director of decommissioning, Akira Ono, said in a recent online interview that the robotic probes for Units 1 and 2 this year are a major “step forward” in cleanup that has been going on for decades.

“It feels like we’ve finally reached the starting line,” Ono said. “Before, we didn’t even know in which direction we had to go.”

Ono said the removal of the Unit 2 molten fuel test will start from one or two pellets, all of which will be sent for lab analysis, meaning a storage facility will not be needed until larger quantities will not be transported. Even a tiny amount would provide valuable data for research and development of fuel and debris removal technology for the three reactors, he said.

Hideyuki Ban, the co-founder of the Citizens’ Nuclear Information Center who has previously served on government nuclear safety panels, proposes the underground burial of solidified treated water for long-term stable storage, while burying the three reactors for several decades – like Chernobyl – and wait for radioactivity to decrease for better safety and worker access instead of rushing cleanup.

Since the disaster, contaminated cooling water has been constantly leaking from the damaged primary containment buildings into the basements of the reactor building, where it mixes with infiltrating groundwater and rainwater.

The water is pumped and treated, partly recycled as cooling water, the rest being stored in 1,000 huge tanks that clutter the plant. The tanks will be full to 1.37 million tonnes by next spring, according to TEPCO.

The government has announced its intention to release the water after treatment and dilution well below legally releasable levels via a planned underwater tunnel at a site about 1 kilometer offshore. The plan has faced fierce opposition from local residents, particularly fishermen worried about further damage to the reputation of the area.

TEPCO and government officials say tritium, which is not harmful in small amounts, is inseparable from water, but all 63 other radioactive isotopes selected for treatment can be reduced to safe levels, tested and diluted. more by sea water before their release.

Scientists say the health impact of consuming tritium through the food chain may be greater than drinking it from water, and more studies are needed.

At one of the water treatment facilities where radiation levels are much higher, a team of workers in full protective gear handled a container full of highly radioactive sludge. It had been filtered from the contaminated water that continually leaked from the damaged reactors and pumped from their basements since the disaster. Large amounts of sludge and solid radioactive waste also accumulate in the plant.

Radiation levels have dropped significantly after decontamination since the disaster, and full protective equipment is only needed in limited areas, including in and around reactor buildings.

On a recent visit, AP reporters used cotton gloves, goggles, headgear and surgical masks to visit low-radiation areas.

Additional protection, including hazmat suits and double rubber gloves, was required as reporters entered Unit 5’s primary containment vessel and stood on the pedestal grate, a structure under the fuel-emptied core, where officials explained the concept of using robotic probes in No 1 and 2 reactors.

TEPCO has emptied spent fuel from the No. 3 and No. 4 reactor pools, but the removal of No. 1 and No. 2 reactors has been delayed for several years due to high radiation and contaminated debris, raising fears of a melting spent fuel in case another major earthquake caused water loss and overheating.

Futaba Mayor Shiro Izawa said the Fukushima Daiichi plant must be fully and safely decommissioned “to make our hometown a safe and livable place again”. Izawa said he wants the government to “erase the negative image (of the region)” by tackling safe cleanup, which is a prerequisite for rebuilding the city.

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