Suspected failure to vent Fukushima reactor casts doubt on accountability standards

Revelations that Tokyo Electric Power Co. (TEPCO) highly likely failed to vent a crippled reactor at its tsunami-hit Fukushima No. 1 Nuclear Power Plant have raised doubts about the utility's and government's accountability standards.

TEPCO had claimed that it had successfully vented the plant's No. 1 reactor to decrease pressure inside it prior to a hydrogen explosion, and the government had supported the power supplier's claim.

The power company attempted to vent the reactor on March 12, the day after the tsunami triggered by the Great East Japan Earthquake hit the plant. After confirming that the pressure inside the containment vessel of the reactor had declined, TEPCO announced at around 3 p.m. that it had succeeded in venting the reactor.

However, the pressure still remained above the designated upper limit of 427 kilopascals and rose moderately after the announcement. Moreover, the monitoring post on its premises showed no signs of radioactive materials being released out of the reactor following the venting attempt. TEPCO insiders say they were unable to confirm that the valve for venting had opened.

Both TEPCO and the government could have checked whether the venting was successful on many occasions. Nevertheless, the government simply mimicked TEPCO's comments on the matter in a report it submitted to the International Atomic Energy Agency (IAEA) on June 7, without scrutinizing the utility's view for nearly three months.