NRA releases images of debris inside Fukushima reactor building

June 05, 2013

By JIN NISHIKAWA/ Staff Writer

The Nuclear Regulation Authority released some of the images on June 4 of damaged equipment that was used to cool a reactor at the Fukushima No. 1 nuclear power plant.

The nuclear watchdog inspected the plant on May 30-31 to examine the isolation condensers in the No. 1 reactor building after the Diet investigatory panel said the condensers could have been damaged by the Great East Japan Earthquake on March 11, 2011, before the tsunami struck.

The NRA plans to scrutinize the images and start discussions this month to determine if the equipment was damaged by the 9.0-magnitude temblor.

The images show a large amount of debris scattered on the floor, and that some heat insulating materials wrapping the condensers had peeled away, apparently as a result of the March 12, 2011, hydrogen explosion at the No. 1 reactor building, operated by Tokyo Electric Power Co.

The isolation condensers cool steam from the reactor’s pressure vessel, condense it into water and return the cooling water into the reactor. Installed solely in the No. 1 reactor building, the condensers were designed to function even without a power source in an emergency.

During the May inspection, the investigators were able to remain on the fourth floor of the building--where the condensers were installed--for only 15 minutes due to high levels of radiation, which were measured at 20-30 millisieverts per hour.

Whether the condensers were damaged before the tsunami has been at the center of debate because of the implications with regard to the adequacy of anti-quake preparedness at the Fukushima power plant and other nuclear facilities.

Experts believe that the condensers failed, contributing to a meltdown at the No. 1 reactor taking place earlier than expected. The melting of fuel rods in the reactor began several hours after the quake and tsunami.

The Diet’s Fukushima Nuclear Accident Independent Investigation Commission pointed out the possibility in its report last year that the condensers were damaged by the quake before the subsequent tsunami struck the facility.

Engineers working near the condensers at the time of the quake and tsunami told the panel that they saw water leaking before the tsunami inundated the plant.

But the government’s Investigation Committee on the Accident at the Fukushima Nuclear Power Stations concluded that there were no signs indicating damage stemming from the quake.

The NRA’s recent inquiry came after a TEPCO official dissuaded members of the Diet panel in February 2012 from conducting an on-site survey by misinforming them that it was “pitch dark” inside the facility and unfit for inspections.

By JIN NISHIKAWA/ Staff Writer
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Debris left by a hydrogen explosion is scattered about in the No. 1 reactor building at the Fukushima No. 1 nuclear power plant on May 31, including insulation that had covered the isolation condensers. (Provided by the Nuclear Regulation Authority)

Debris left by a hydrogen explosion is scattered about in the No. 1 reactor building at the Fukushima No. 1 nuclear power plant on May 31, including insulation that had covered the isolation condensers. (Provided by the Nuclear Regulation Authority)

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  • Debris left by a hydrogen explosion is scattered about in the No. 1 reactor building at the Fukushima No. 1 nuclear power plant on May 31, including insulation that had covered the isolation condensers. (Provided by the Nuclear Regulation Authority)
  • Nuclear Regulation Authority investigators examine the damage to ventilation ducts at the No. 1 reactor building at the Fukushima No. 1 nuclear power plant. (Provided by the Nuclear Regulation Authority)
  • The Asahi Shimbun

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