Japan's nuclear regulator confirms safety of Shimane plant reactor for restart

Regulators officially adopted a screening report Wednesday concluding that the No. 2 reactor at the Shimane nuclear power plant in Matsue, Shimane Prefecture, meets the country’s new safety standards for a restart.

The No. 2 unit at the nuclear plant, operated by Chugoku Electric Power Co., became the 17th reactor in the country to pass the Nuclear Regulation Authority’s safety screenings.

The NRA examines the safety of nuclear reactors based on strict standards Japan introduced after the March 2011 triple meltdown at Tokyo Electric Power Company Holdings Inc.’s tsunami-hit Fukushima No. 1 nuclear plant.

The Shimane plant is the only nuclear power plant in the country located in a prefectural capital.

The Shimane No. 2 reactor became the fifth boiling-water reactor in Japan to win restart approval since the disaster hit reactors of the same type at the Fukushima plant, after the No. 6 and No. 7 reactors at Tepco’s Kashiwazaki-Kariwa nuclear plant in Niigata Prefecture.

With unanimous approval granted by the five members of the NRA, Chugoku Electric will aim to complete construction work under the safety standards by the end of the current fiscal year, which runs through next March.

But the timing for restarting the No. 2 unit remains undecided, as the utility needs to obtain consent from Matsue municipal authorities and the Shimane Prefectural Government.

Close attention is also being paid to the stance of neighboring Tottori Prefecture, as it is located within a 30-kilometer radius of the nuclear plant.

The population residing within the 30-km radius totals roughly 460,000, the third-largest following that of Japan Atomic Power Co.’s Tokai No. 2 nuclear plant in Ibaraki Prefecture and Chubu Electric Power Co.’s Hamaoka nuclear plant in Shizuoka Prefecture.

Located near a geological fault in an area facing the Sea of Japan, the Shimane nuclear plant is protected by a wall reaching 15 meters above sea level constructed on the assumption that a tsunami as high as 11.9 meters could reach the site if a major earthquake occurs.

The safety measures also include preparation for a potential eruption of Mount Sanbe in the prefecture, in which it is assumed up to 56 centimeters of volcanic ash could pile up at the plant.

The power supplier applied for safety screenings for the Shimane No. 2 unit in December 2013. During its screenings, the NRA focused on the company’s earthquake and tsunami estimates.

Chugoku Electric reviewed its evaluation of the Shinji fault, located some 2 kilometers south of the plant, and raised the assumed ground acceleration that could be caused by an earthquake from 600 gals to 820 gals.

Also, the estimated maximum tsunami height was changed from 9.5 meters to 11.9 meters, which the company says can be blocked by the plant’s seawall.

It came to light in June this year that Chugoku Electric had discarded by mistake classified documents about antiterrorism facilities borrowed from the NRA, and had failed to report the problem for about six years.

While noting that the decision to discard the document should be taken as a sign of a deterioration in safety culture at Chugoku Electric, NRA Chairman Toyoshi Fuketa said Wednesday, “We’ll be conducting checks including on whether improvements have been made through maintenance code-related inspections” that will follow the adoption of the safety screening report.

Evacuation plans are drawn up for residents living in areas within 30 kilometers of nuclear plants to prepare for possible severe accidents. Covered by the Shimane plant’s evacuation plan, which was approved by the government’s Nuclear Emergency Preparedness Council on Sept. 7, are people living in Matsue, Izumo and two other cities in Shimane, as well as Sakaiminato and Yonago, which are cities in the adjacent Tottori Prefecture.