The vast majority of Japan’s 42 viable commercial nuclear reactors have not had detailed checkups performed on the air conditioning and ventilation systems of their central control rooms, it has been learned.
According to Japan Atomic Power Co. and nine utilities that manage nuclear power plants, the checkups — conducted at only two of the plants so far — are carried out without removing the insulation on the pipes.
Last month, Chugoku Electric Power Co. found extensive corrosion and holes, including one measuring 30 cm by 100 cm, in the ventilation pipes of the No. 2 reactor at the Shimane nuclear plant in Matsue, Shimane Prefecture. It was the first time the utility had removed the covering on the pipes since the reactor booted up in 1989.
Concluding the pipes were not functioning properly, Chugoku Electric reported the degradation to the Nuclear Regulation Authority.
In the event of a accident, control rooms, which are staffed around the clock, must be self-contained to prevent outside air from entering.
Five reactors at the three nuclear plants that have been reactivated since 2015 have not undergone pipe inspections in which their insulation was removed. Of the five, the No. 1 reactor at Kyushu Electric Power Co.’s Sendai plant in Kagoshima Prefecture and the No. 3 reactor at Shikoku Electric Power Co.’s Ikata plant in Ehime Prefecture are currently in operation.
Following the discovery of the pipe degradation at the Shimane No. 2 reactor, the NRA plans to check conditions at all of the nation’s nuclear plants, sources said.
Hokuriku Electric Power Co. detected rust in the ventilation pipes of the No. 1 reactor at its Shika nuclear plant in Ishikawa Prefecture in 2003. After removing the covers and conducting further inspections, the company replaced the equipment in 2008.
The NRA suspects that the pipe corrosion at the Shimane No. 2 reactor may violate nuclear regulatory standards, an official said.
“As the plant is located near the sea, salt-containing air may have flowed into the pipes and hastened corrosion,” a Chugoku Electric official said.
Most of the nation’s nuclear plants are in coastal areas because they use seawater to cool their turbines.