Takahama: "Safety" measures

December 17, 2014

Screening and measures for Takahama plant

http://www3.nhk.or.jp/nhkworld/english/news/20141217_27.html

Dec. 17, 2014 - Updated 10:54 UTC+1

A key point in screening the Takahama nuclear power plant in Fukui Prefecture, central Japan, was an assumption about the strongest earthquake that could hit the facility.

The Nuclear Regulation Authority has conducted 67 review meetings and 3 surveys at the plant since Kansai Electric Power Company in July 2013 filed with the NRA for the screening. The procedure is needed to restart the No. 3 and 4 reactors of the facility in Fukui Prefecture.

Kansai Electric initially submitted 550 gals as a figure for the strength of the possible quake. But the NRA rejected the figure as too optimistic.

In December 2013, the utility raised the figure to 700 gals, taking into consideration possible simultaneous movement along 3 faults in Wakasa Bay and land areas to the east.

The utility first filed as a figure for the tallest possible tsunami 2.6 meters above sea level, but later raised it to 5.7 meters. But the firm had miscalculated the duration of possible seafloor landslides, and again raised the figure, to 6.2 meters.

After the revisions, Kansai Electric decided to increase the height of a tsunami breakwater from an initially planned 6 meters to 8.

The firm installed more equipment as required by new regulations in case of a serious accident. It installed pumps for cooling reactors and containment vessels, and devices to prevent hydrogen explosions. Such blasts occurred in the 2011 Fukushima Daiichi accident.
Instructions for responding to accidents at the plant are thousands of pages. They cover steps to manually open valves of pumps for cooling reactors in case of complete power outages. This is based on lessons from the Fukushima Daiichi accident.