TEPCO Blind to Possible Hydrogen Blast

Thursday, August 18, 2011 @ 05:08 PM gHale

Tokyo Electric Power Co. (TEPCO) failed to predict the hydrogen explosion that occurred March 12 following the disaster at the Fukushima No. 1 Nuclear Power Plant, an employee told investigators.

“Nobody was able to predict the explosion,” the TEPCO employee told members of the government’s fact-finding panel on the Fukushima nuclear crisis.

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“We made a serious mistake as we failed to grasp important information on the power station,” plant manager Masao Yoshida told the panel.

The investigation has also revealed TEPCO did not prepare an instruction manual on procedures for venting to protect reactors’ containment vessels when external power sources are lost.

The damaged No. 1 reactor building, center left, at the Fukushima No. 1 Nuclear Power Plant pictured March 12.

The damaged No. 1 reactor building, center left, at the Fukushima No. 1 Nuclear Power Plant pictured March 12.

As part of its investigation into the crisis, the fact-finding panel questioned Yoshida and other TEPCO employees as well as officials with government regulators.

The hydrogen explosion occurred at the plant’s No. 1 reactor at 3:36 p.m. March 12, the day after the Great East Japan Earthquake and tsunami hit the plant. The blast blew off the upper part of the building housing the reactor.

Experts suspect the hydrogen generated after zirconium contained in fuel rods heated and reacted with water.

TEPCO officials said workers had never imagined that hydrogen would fill the reactor building and eventually explode because they focused on checking the conditions of the reactor and its containment vessel.

Because the plant had no instruction manual on venting, workers considered a procedure for venting by closely examining the blueprint of the reactor.

Since all the external power sources had been lost, workers at the plant procured batteries and other equipment to secure power sources. However, due to insufficient communications between workers on the types of devices needed, various machines came into the plant, forcing workers to take time to select usable devices from among them.

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