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Fukushima Daiichi Nuclear Power Plant, risk of earthquakes revealed… Failure of seismometers, building deterioration, tanks shifting….

March 20, 2021
　The earthquake that struck the Tohoku and Kanto regions on the evening of February 13, 2011, which had a maximum intensity of 6 on the Japanese seismic scale, revealed that seismometers at TEPCO’s Fukushima Daiichi plant had been removed more than four months earlier, highlighting the dangers posed by the plant, which was damaged in an accident 10 years ago, and the sloppy system in place at TEPCO. The earthquake was strong. With high radiation levels in the buildings making normal maintenance and inspections impossible, how can we ensure the safety of the ongoing work toward the “decommissioning” of the reactors, which has no end in sight?

◆Still removed after failure
　Akira Ono, chief executive officer of the Fukushima Daiichi Decommissioning Promotion Company, was forced to apologize at a press conference on February 25 because a seismograph that was supposed to have been installed in the Unit 3 reactor building had failed and had been removed.
　One of the two seismometers installed in the reactor building failed in July of last year when it got stuck in a pool of water, and three months later the other seismometer was out of commission. The top management was unaware of this fact for seven and a half months.
　The seismometers originally installed in Units 1 through 4 to determine the emergency shutdown of the reactors were rendered unusable by the tsunami and accident 10 years ago. In April of last year, TEPCO installed two of the earlier seismometers to monitor the shaking of the Unit 3 reactor building, which had been damaged by a hydrogen explosion, but in the end, none of the “valuable data” that Ono emphasizes was obtained.
　After the February earthquake, the water level in the containment vessels of Units 1 and 3, where melted-down nuclear fuel (debris) remains, dropped. It is believed that the damaged areas created during the accident have spread. The positions of 53 tanks that store contaminated water and other materials in the process of being cleaned up have also shifted by up to 19 centimeters. If the pipes connecting the tanks were to come loose, a large amount of contaminated water could leak out.
The extent of the damage is unknown.
　Making earthquake preparedness difficult is the high level of radiation in the building. One worker said, “I can’t see inside, so I don’t know how the damage is spreading.
　Katsumi Takiguchi, a professor emeritus at Tokyo Institute of Technology who specializes in reinforced concrete buildings, compiled a performance assessment of the Fukushima Daiichi Nuclear Power Plant buildings at a subcommittee of the Atomic Energy Society of Japan in 2019. He said, “Reactor buildings have walls that are 1.5 or 2 meters thick,” and pointed out that there is little fear of collapse.
　What concerns Takiguchi is the localized deterioration of the buildings. If the reinforcing steel in the walls rusts and swells, exposing the concrete, the rusting will accelerate, so cracks and other abnormalities must be noticed quickly. Although seismograph observations are valuable in detecting deterioration trends, he asserts, “They are not a substitute for visual inspections.

◆ “TEPCO is losing its nerve.
　According to TEPCO, the exterior of the Unit 1-3 buildings has been visually inspected about once a year since FY19. Little is known about the inside of the buildings beyond a robotic survey conducted immediately after the accident. The company aims to conduct inspections with people inside the buildings after April of this year, which, if realized, will help strengthen countermeasures.
　However, it is essential to minimize the radiation exposure of the workers, and the method and frequency of inspections are still under consideration. Inspections of the reactor equipment in Units 1 through 3, where debris remains and the tops of the containment vessels are contaminated with extremely high concentrations of radioactive materials, will be extremely difficult.
　The safety of the site is also a top priority for the removal of spent nuclear fuel and debris from the pools. The number of veteran employees with knowledge of the accident has been reduced, and some workers are heard to say, “TEPCO is losing its sense of urgency. Mr. Ono, who is in charge of decommissioning the plant, said, “I think the plant was highly sensitive to the tsunami. We also have to think about earthquakes,” he stresses, “but will we be prepared in time? The next earthquake could come at any time.
https://www.tokyo-np.co.jp/article/92694?fbclid=IwAR3Y8kYYXRoDAh8DPDAodsD6p5itoAJufNvcRDJoK_jiSux5HrPv5f-rd98

March 20, 2022 Posted by dunrenard | Fuk 2022 | Damages, Earthquake, Failures, Fukushima Daiichi | Leave a comment