May 27, 2022
The removal work of pipes contaminated with high levels of radioactive materials between Fukushima Daiichi Nuclear Power Plant Units 1 and 2, which had been resumed by Tokyo Electric Power Co. for the first time in two months, was suspended again after extremely high radiation levels of 3 sieverts (3000 millisieverts) per hour were detected in the first cut pipe on May 23. The second disconnection scheduled for the 26th was cancelled. TEPCO will take time to reconsider the cutting method and measures to control workers’ exposure.
The radiation dose of 3 sievert per hour is high enough to cause death if a person is exposed to radiation for several hours. According to TEPCO, workers who measured the dose inside the cut surface of the pipes were exposed to a maximum of 0.41 millisieverts, which did not exceed the exposure limit that had been planned in advance.
Before cutting, the 30-centimeter-diameter pipe was covered with urethane to prevent radioactive materials from leaking out of the pipe when it was cut. However, the cut surface with the high radiation dose did not have a lid, and the inside of the other cut surface, which had a lid, was 120 millisieverts per hour.
The pipes were used for venting highly contaminated steam from the reactor to prevent the containment vessel from rupturing at the beginning of the accident in March 2011. Akira Ono, chief executive officer of the Fukushima Daiichi Decommissioning Promotion Company, said at a press conference on March 26, “The high concentration is thought to be caused by the venting. We need to work carefully and consider our procedures.
The removal of piping using remote-controlled equipment began at the end of February, but was suspended for about two months due to a series of troubles that forced a review. The plan was to cut and remove a total of 135 meters of piping in 26 installments, and the first installment was finally completed on the 23rd of this month. （The first round finally succeeded on the 23rd of this month.)
May 27, 2022