Holes Found on Air Ducts for Control Rooms at 6 Reactors in Japan

May 24, 2018

Tokyo, May 23 (Jiji Press)--Holes from corrosion have been found on air ducts for the main control rooms at a total of six reactors at four nuclear power plants in Japan, the Nuclear Regulation Authority said Wednesday.

The announcement came after the NRA instructed nuclear plant operators in January 2017 to check air ducts for reactor control rooms, following the discovery of corrosion and holes at the No. 2 unit at Chugoku Electric Power Co.'s Shimane plant in Shimane Prefecture in 2016.

The Shimane No. 2 reactor is one of the six. The five others are the No. 1 unit at the Shimane plant, the No. 3 and No. 7 units at Tokyo Electric Power Company Holdings Inc.'s Kashiwazaki-Kariwa plant in Niigata Prefecture, the No. 3 unit at Chubu Electric Power Co.'s Hamaoka plant in Shizuoka Prefecture and the reactor at Japan Atomic Power Co.'s Tokai No. 2 plant in Ibaraki Prefecture.

Corrosion was also found at seven other reactors, including the No. 3 unit at Tohoku Electric Power Co.'s <9506> Onagawa plant in Miyagi Prefecture, but no holes were discovered.

The air duct holes could make it difficult to shut off air flows to the control rooms in times of accidents releasing radioactive materials, experts said.

The plant operators claimed that mandatory levels of airtightness can be maintained, despite the holes.

At a meeting of the NRA on Wednesday, however, the secretariat for the regulatory body said that it will examine whether TEPCO's claim regarding the Kashiwazaki-Kariwa No. 3 reactor is reasonable, pointing out that a crack as long as 13 centimeters was found at the unit.

TEPCO plans to replace air duct parts at the reactor, company officials said, adding that its plan to restart reactors at the Kashiwazki-Kariwa plant will not be affected. All seven reactors at the plant are now offline. Jiji Press