Experts' fears "unscientific", says Tanaka

October 2, 2014

Nuclear safety chief counters experts over volcanic hazards

http://mainichi.jp/english/english/newsselect/news/20141002p2g00m0dm042000c.html

TOKYO (Kyodo) -- The chairman of the nuclear safety regulator on Wednesday countered volcanologists' claims that more discussion is needed before restarting idled reactors as it is impossible to predict volcanic hazards.

All reactors in Japan remain offline. But the Sendai plant, located in a region of southwestern Japan with active volcanoes, will restart soon after the Nuclear Regulation Authority gave a safety clearance to the facility in September based on new, tighter regulations.

NRA Chairman Shunichi Tanaka told a press conference that he disagrees with "arguments that we should stop all social activities because we never know when natural disasters happen," saying there is a "gap" in perception between him and the volcanologists.

The nuclear safety regulator judged in September that risks of massive volcanic eruptions around the two-reactor Sendai plant in Kagoshima Prefecture are negligible during the facility's lifespan.

Public debate about the safety of the Sendai plant has been further fueled by Saturday's eruption of Mt. Ontake in central Japan that killed about 50 people.

The Sendai plant, on the island of Kyusu, is some 50 kilometers from Mt. Sakurajima, an active volcano. There are a total of five calderas around the complex.

NRA chairman calls concerns over safety of Sendai nuclear plant due to volcanoes 'unscientific'

http://mainichi.jp/english/english/newsselect/news/20141002p2a00m0na009000c.html

The chairman of Japan's nuclear watchdog has confirmed that the levels of safety screening on the idled Sendai nuclear power plant are appropriate, arguing that comparisons of the recent eruption of Mount Ontake and possible eruptions of volcanoes located near the nuclear plant are "unscientific."

Nuclear Regulation Authority (NRA) Chairman Shunichi Tanaka told a news conference on Oct. 1 that it is unscientific to compare the recent phreatic eruption on Mount Ontake in central Japan and possible volcanic eruptions in areas near the Sendai plant, arguing that the natural phenomena envisaged in the plant's safety measures are different from what has happened on Mount Ontake.

Concerns over safety measures against volcanic eruptions for the Sendai plant in Kagoshima Prefecture, whose No. 1 and 2 reactors recently passed the NRA's screening process and are waiting to be restarted, were further fueled by the Mount Ontake eruption on Sept. 27.

According to the Japan Meteorological Agency's liaison conference on the prediction of volcanic eruptions, the scale of the eruption on Mount Ontake is small as the amount of ejected matter stands at some 1 million metric tons. Meanwhile, the amount of volcanic ejecta from possible volcanic eruptions concerned in areas near the Sendai plant is estimated to be 1 million times greater than that of the Mount Ontake eruption, and pyroclastic flows are predicted to reach at least 100 kilometers from the craters. If lava reached nuclear reactors under operation, the NRA or plant operator Kyushu Electric Power Co. would not be able to handle the situation.

For this reason, the NRA is set to beef up its surveillance system for volcanic activities and take necessary measures, such as stopping nuclear reactors and removing nuclear fuel, when signs of volcanic eruptions are detected.

Kyushu Electric has categorized 14 volcanoes located within 160 kilometers in diameter from the Sendai plant as mountains that "may become active in the future" and "cannot be ruled out over the possibility of becoming active volcanoes." The utility has judged that even if those mountains erupted, it would not affect the Sendai plant. It has set up measures for volcanic ash, based on its evaluation that as much as 15 centimeters of ash from Mount Sakurajima would fall on the premises of the plant. The NRA confirmed that the utility's evaluation was appropriate, and Tanaka said, "We have concluded that even larger eruptions than Mount Ontake would not affect the Sendai plant."

However, huge volcanic eruptions on the scale of the NRA's calculations are believed to occur only once every 10,000 years, and further research on such levels of eruption have not been successful.

The NRA has established a committee comprised of a group of volcanologists and begun drawing outlines of a system for volcano observations and for reading signs of volcanic eruptions. However, setting up a yardstick for predicting eruptions is a subject of future discussion as many volcanologists have argued that current studies on volcanoes fall short in predicting eruptions.

October 1, 2014

NRA chief defends volcanic hazard measures

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

Oct. 1, 2014 - Updated 22:06 UTC+2

The head of Japan's nuclear power regulator has defended its approval of volcanic hazard measures for a nuclear power plant in Kagoshima, southern Japan.

Shunichi Tanaka, the chairman of the Nuclear Regulation Authority, was speaking at a news conference on Wednesday.

His remarks follow the eruption of Mount Ontake in central Japan on Saturday without any detection of warning signs. Dozens of climbers died in the eruption.

The eruption prompted public concern over volcanic hazard measures for the Sendai plant in Kagoshima Prefecture operated by Kyushu Electric Power Company. There are active volcanoes in the prefecture.
The utility had showed plans to remove nuclear fuel from the facility if it detects any signs of volcanic activity or tectonic plate movement around the plant.

The NRA officially approved the plans last month as part of its screening of measures proposed by the utility based on government requirements for the restart of offline reactors.

At Wednesday's news conference, the NRA chief said Ontake's hydro volcanic eruption is unlike any huge volcanic eruption that may occur around the Sendai nuclear power plant. He says discussing them as the same type of event is not scientific.

Tanaka said that before an enormous eruption, land movements and tremors appear much earlier than for the ongoing eruption of Mount Ontake.

The NRA has held 2 meetings with volcanologists since August. Participants pointed out the difficulty of predicting volcanic eruptions using current knowledge and technology.