Air duct corrosion and holes found at seven nuclear plants via The Japan Times

Corrosion and holes have been found in ventilation ducts at 12 reactors at seven nuclear plants across the country, the Nuclear Regulation Authority said Wednesday, raising concerns that workers could be exposed to radiation in the event of an accident.

The governmental nuclear watchdog released the results of a nationwide survey it had ordered following a revelation in December 2016 that corrosion had left multiple holes in the air ducts of the No. 2 reactor at Chugoku Electric Power Co.’s Shimane plant in western Japan. That reactor was not included in the survey.

Corrosion and holes have been found in ventilation ducts at 12 reactors at seven nuclear plants across the country, the Nuclear Regulation Authority said Wednesday, raising concerns that workers could be exposed to radiation in the event of an accident.

The governmental nuclear watchdog released the results of a nationwide survey it had ordered following a revelation in December 2016 that corrosion had left multiple holes in the air ducts of the No. 2 reactor at Chugoku Electric Power Co.’s Shimane plant in western Japan. That reactor was not included in the survey.

Serious corrosion was found at the No. 3 unit of the Kashiwazaki-Kariwa plant in Niigata Prefecture operated by Tokyo Electric Power Company Holdings Inc. and may have abnormally affected ventilation of the central control room, the watchdog said.

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Corrosion or holes were found in steel or galvanized steel ducts at Tohoku Electric Power Co.’s Onagawa nuclear plant, Japan Atomic Power Co.’s Tokai No. 2 nuclear plant, Tepco’s Fukushima No. 1 nuclear plant and Kashiwazaki-Kariwa nuclear plant, Chubu Electric Power Co.’s Hamaoka plant, Hokuriku Electric Power Co.’s Shiga nuclear plant and Chugoku Electric’s Shimane plant.

If an accident occurs, radioactive materials could flow into a plant’s central control room through such holes, putting workers in danger of radiation exposure.

At the No. 3 reactor at the Kashiwazaki-Kariwa plant, a crack as large as 13 centimeters in length and 5 cm in width was found. A total of nine holes and cracks have been discovered at the Nos. 3 and 7 units at the plant.

All the reactors with corrosion were boiling-water reactors, the same type used at the Fukushima No. 1 plant, which spewed a massive amount of radioactive material into the atmosphere following the March 2011 earthquake and tsunami.