Japan's nuclear regulator says it will investigate damage to the underground piles supporting a facility at a nuclear plant in Kashiwazaki-Kariwa in Niigata Prefecture.
The Nuclear Regulation Authority discussed the matter at a regular meeting on Wednesday. The NRA secretariat then decided to carry out an on-site inspection early next year.
The Kashiwazaki-Kariwa plant operator, Tokyo Electric Power Company, says it confirmed the damage during work in July to increase the plant's resistance to earthquakes.
Eight reinforced concrete piles support the foundation of a facility adjacent to a building housing the plant's No.6 reactor.
TEPCO says each pile measures 1.8 meters across and 12 meters long. Reinforcing bars in one of the piles were found to have been broken or deformed. Cracks were found on the other seven piles.
At the Wednesday meeting, NRA chair Fuketa Toyoshi said that a 2007 earthquake in Niigata may have caused the damage. He suggested that the cause of the damage and other matters should be clarified.
The NRA secretariat decided to confirm with TEPCO what caused the damage, how to repair the piles and whether other facilities have been affected.
The plant's No.6 and 7 reactors have passed the necessary screenings to restart operations. But the NRA began further inspections recently after a series of serious breaches of anti-terrorism measures occurred, leaving the reactors offline.