18 Janvier 2017
January 18, 2017
Nuclear regulators order checks for duct decay
Japan's nuclear regulators have ordered checks at nuclear plants after holes were found in ventilation ducts at the Shimane plant in western Japan.
The holes, apparently from decay, were found last month in the ducts at the central control room of the plant's No.2 reactor. If they are unfixed, the room could become contaminated in the event of a serious accident.
The plant's operator had failed to find the holes because the ducts are covered by insulation. The facility says the covers have not been removed for inspection since the reactor began operating.
The Nuclear Regulation Authority on Wednesday ordered operators of nuclear stations across Japan to check for similar problems, with priority on 4 reactors that have already been checked for restarts.
Those to be prioritized are the No.1 and 2 reactors at the Sendai plant in Kagoshima Prefecture, the Takahama No.3 reactor in Fukui Prefecture, and the Ikata No.3 reactor in Ehime Prefecture.
Inspectors have been asked to remove covers to check duct conditions in central control rooms and emergency headquarters.
The operators of the 3 plants say they checked for airtightness of central control rooms before the reactors were restarted. Engineers say even if holes open in the ducts, their covers could prevent leakage of contaminated air, securing airtightness in the rooms.
Rules for plant operation stipulate that if fixing holes would take more than 10 days, reactors should be halted.
As for non-priority reactors and reprocessing plants, regulators ordered checks before they are put back online or exchanging of nuclear fuel.
MATSUE -- Nineteen corroded holes have been discovered in air ducts inside the No. 2 reactor at the Shimane nuclear power plant, the Mainichi Shimbun has learned.
As a consequence of this discovery, the Nuclear Regulation Authority decided on Jan. 18 to order all electric power companies to carry out checks on ducts inside all of their nuclear power plants.
The corroded holes were discovered when insulating material -- that had been wrapped around the ducts -- was removed during a check in December 2016 at the No. 2 reactor at the Shimane plant, which is operated by Chugoku Electric Power Co. The largest hole of the 19 was found to be approximately 30 centimeters by 100 centimeters in size.
Corroded holes in ducts present a threat as there is a chance that radioactive material could flow into the central control room via the holes during an accident -- thereby exposing power plant staff to radiation.