A panel set up by Tokyo Electric Power Co. to investigate the company's coverup of nuclear reactor faults has discovered that unauthorized bolts were used to repair a reactor at Tepco's Fukushima No. 1 plant, company sources said Tuesday.
The bolts were used to secure a manhole cover on the plant's No. 5 reactor, the sources said. The manhole is used to access the pressurized container and is located just below the reactor shroud. The cover was sealed with bolts after construction of the reactor was completed.
During a regular check, it was found that some of the bolts used for the cover were loose. Engineers tried to screw them tight, but the threads were stripped so the bolts had to be replaced, according to the investigation.