In this accident, the air for operating and power source for driving the valve required for venting had been lost due to the station black out caused by the tsunami, so the valve could not be remotely operated from the main control room. Consequently, manual operation of the value was attempted on-site and temporary air compressors, small generators and other equipment were used to attempt the opening of the valve, but such an operation was extremely difficult on a site under darkness and with an atmosphere of high dose and high temperature. Also, situations were repeatedly seen in which once a valve was opened, it could not be maintained in that state and immediately closed. It was difficult to promptly and appropriately perform venting.
Because venting was an important matter that would release radioactive materials, the matter was confirmed by the president of the Tokyo Electric Power Company in addition to the decision of the station director, and a request to perform venting was also put to the national government.
The national government was aware of the necessity for venting, and there is no fact that it took time to gain approval from the national government.
To implement venting, the power station confirmed the status of evacuation of residents in the surrounding area and endeavored to make the exposure to the minimum extent possible.