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.