Fri, Mar 14, 2025 page11

• Massive Fukushima plant cleanup work involves high radiation and stress

  • By Mari Yamaguchi / AP, OKUMA, Japan
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  The Fukushima Daiichi nuclear power plant’s radiation levels have significantly dropped since the cataclysmic meltdown in Japan 14 years ago. Workers walk around in many areas wearing only surgical masks and regular clothes.

  It’s a different story for those who enter the reactor buildings, including the three damaged in the 2011 earthquake and tsunami. They must use maximum protection — full facemasks with filters, multi-layered gloves and socks, shoe covers, hooded hazmat coveralls and a waterproof jacket and a helmet.

  As workers remove melted fuel debris from the reactors in a monumental nuclear cleanup effort that could take more than a century, they are facing both huge amounts of psychological stress and dangerous levels of radiation.

  

  Employees of Tokyo Electric Power Company Holdings (TEPCO) on Feb. 20 inside to the area under the Unit 5 reactor pressure vessel, which survived the earthquake-triggered tsunami in 2011, at the Fukushima Daiichi nuclear power plant in Futaba town, northeastern Japan.

  Photo: AP

  A remote-controlled extendable robot with a tong had several mishaps including equipment failures before returning in November with a tiny piece of melted fuel from inside the damaged No. 2 reactor.

  That first successful test run is a crucial step in what will be a daunting, decades-long decommissioning that must deal with at least 880 tons of melted nuclear fuel that has mixed with broken parts of internal structures and other debris inside the three ruined reactors.

  Akira Ono, chief decommissioning officer at the Tokyo Electric Power Company Holdings, which manages the plant, says even the tiny sample gives officials a lot of information about the melted fuel. More samples are needed, however, to make the work smoother when bigger efforts to remove the debris begin in the 2030s.

  A second sample-retrieval mission at the No. 2 reactor is expected in coming weeks.

  Operators hope to send the extendable robot farther into the reactor to take samples closer to the center, where overheated nuclear fuel fell from the core, utility spokesperson Masakatsu Takata said. He pointed out the target area as he stood inside the inner structure of the No. 5 reactor, which is one of two reactors that survived the tsunami. It has an identical design as No. 2.

  HARD TO SEE, BREATHE OR MOVE

  Radiation levels are still dangerously high inside the No. 2 reactor building, where the melted fuel debris is behind a thick concrete containment wall. Earlier decontamination work reduced those radiation levels to a fraction of what they used to be.

  In late August, small groups took turns doing their work helping the robot in 15 to 30-minute shifts to minimize radiation exposure. They have a remotely controlled robot, but it has to be manually pushed in and out.

  “Working under high levels of radiation (during a short) time limit made us feel nervous and rushed,” said Yasunobu Yokokawa, a team leader for the mission. “It was a difficult assignment.”

  Full-face masks reduced visibility, an extra waterproof jacket made it sweaty and hard to move, and triple-layered gloves made their fingers clumsy, Yokokawa said.

  To eliminate unnecessary exposure, they taped around gloves and socks and carried a personal dosimeter to measure radiation. Workers also rehearsed the tasks they’d perform to minimize exposure.

  The mission stalled early on when workers noticed that a set of five 1.5-meter pipes meant to push the robot into the reactor’s primary containment vessel had been arranged in the wrong order.

  A camera on the robot also failed because of high radioactivity.

  The workers’ highest individual radiation dose was more than the overall average but still far below anything approaching a 100-millisievert five-year dose limit.

  Even so, a growing number of workers are concerned about safety and radiation at the plant, said Ono, the decommissioning chief, citing an annual survey of about 5,5,00 workers.

  In 2023, two workers splashed with contaminated sludge at a water treatment facility were hospitalized, though they had no health problems.

  MAKING SURE IT’S SAFE

  Yokokawa and a plant colleague, Hiroshi Ide, helped in the 2011 emergency and are team leaders today. They say they want to make the job safer as workers face high radiation in parts of the plant.

  On the top floor of the No. 2 reactor, workers are setting up equipment to remove spent fuel units from the cooling pool. That’s set to begin within two to three years.

  At the No. 1 reactor, workers are putting up a giant roof to contain radioactive dust from decontamination work on the top floor ahead of the removal of spent fuel.

  To minimize exposure and increase efficiency, workers use a remote-controlled crane to attach pre-assembled parts, according to TEPCO. The No. 1 reactor and its surroundings are among the most contaminated parts of the plant.

  WHAT’S NEXT??

  Workers are also removing treated radioactive wastewater. They recently started dismantling the emptied water tanks to make room to build facilities needed for the research and storage of melted fuel debris.

  After a series of small missions by robots to gather samples, experts will determine a larger-scale method for removing melted fuel, first at the No. 3 reactor.

  Experts say the hard work and huge challenges of decommissioning the plant are just beginning. There are estimations that the work could take more than a century. The government and TEPCO have an initial completion target of 2051, but the retrieval of melted fuel debris is already three years behind, and many big issues remain undecided.

  Ide, whose home in Namie town, northwest of the plant, is in a no-go zone because of nuclear contamination, still has to put on a hazmat suit, even for brief visits home.

  “As a Fukushima citizen, I would like to make sure the decommissioning work is done properly so that people can return home without worries,” he said.
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