Plant operator Tokyo Electric Power Co. (TEPCO) has defended the worker's judgment as appropriate after analyzing the sequence of events and releasing its findings at the order of its government regulator, the Nuclear and Industrial Safety Agency.
The reactor core isolation cooling (RCIC) system of the No. 3 reactor stopped at 11:36 a.m. on March 12, the day after the plant was hit by a massive tsunami triggered by the Great East Japan Earthquake, causing the water level in the reactor to decline.
In response, its high-pressure coolant injection (HPCI) system, powered by a battery, was automatically activated.
However, the pressure in the reactor subsequently lowered below the standards specified by its operation manual, and vibrations increased. The worker in charge stopped the HPCI system and decided to switch to manual injection of water for fear that the trouble could cause radioactive substances to leak from the reactor, according to the utility. Read More