"TOKYO — Just a month before a powerful earthquake and tsunami crippled the Fukushima Daiichi plant at the center of Japan's nuclear crisis, government regulators approved a 10-year extension for the oldest of the six reactors at the power station despite warnings about its safety.
The committee reviewing extensions pointed to stress cracks in the backup diesel-powered engines at Reactor No. 1 at the Daiichi plant, according to a summary of its deliberations that was posted on the Web site of Japan's nuclear regulatory agency after each meeting. The cracks made the engines vulnerable to corrosion from seawater and rainwater. The engines are thought to have been knocked out by the tsunami, shutting down the reactor's vital cooling system.
The Tokyo Electric Power Company, which runs the plant, has since struggled to keep the reactor and spent fuel pool from overheating and emitting radioactive materials.
Several weeks after the extension was granted, the company admitted that it had failed to inspect 33 pieces of equipment related to the cooling systems, including water pumps and diesel generators, at the power station's six reactors, according to findings published on the agency's Web site shortly before the earthquake.
Regulators said that "maintenance management was inadequate" and that the "quality of inspection was insufficient." "