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Recognising the risks of volcanoes for nuclear plants

December 14, 2017

In ordering nuclear plant suspension, Hiroshima high court recognizes volcanic risk



Lawyers hold up banners with messages such as, "Injunction issued," following a Hiroshima High Court order to suspend operation of the No. 3 reactor at Shikoku Electric Power Co.'s Ikata Nuclear Power Plant, in Hiroshima's Naka Ward, on Dec. 13, 2017. (Mainichi)

HIROSHIMA -- Recognizing the risk of a volcanic eruption, the Hiroshima High Court on Dec. 13 ordered the suspension of a reactor at Shikoku Electric Power Co.'s Ikata Nuclear Power Plant -- a decision that could deal a blow to power companies' finances and the government's energy policy, as there are many nuclear plants located near volcanoes.

In its decision, which overturned a lower court ruling, the high court judged that new regulatory standards for nuclear power plants implemented in the wake of the Fukushima nuclear disaster were reasonable, but that the Nuclear Regulation Authority (NRA)'s judgment on the risks of damage from a volcanic eruption were "irrational." The court mentioned the danger of pyroclastic flows from a catastrophic eruption at the Aso Caldera, located about 130 kilometers away from the Ikata plant in Ehime Prefecture, together with the threat of volcanic ash and other falling material.


The court decision to order suspension of the plant's No. 3 reactor was based on an "evaluation guide on the effects from volcanoes" that the NRA had produced to screen nuclear plants' volcanic eruption countermeasures.


Based on the guide, the court in its ruling stated that there was a need to demonstrate that there was a low possibility of a pyroclastic flow reaching the plant even in the event of a massive eruption at the Aso Caldera on the scale of one that is said to have occurred some 90,000 years ago. The court criticized a geological survey by Shikoku Electric Power Co., and judged that the location was not fit for the building of a nuclear power plant. It also judged that the utility had underestimated the effects of a volcanic eruption.


The high court acknowledged that it is the social norm to ignore the risks of events whose frequency of occurrence was extremely low. However, it ruled that it was impermissible for the district court to alter the framework for the judgment criteria by saying that there would be no safety deficiencies even if a catastrophic eruption were not envisaged as a natural disaster -- and overturned the lower court's decision.


A representative of the secretariat of the NRA expressed dissatisfaction with the latest ruling.

"It's been 90,000 years since the last catastrophic eruption at the Aso Caldera, and there's no large magma chamber underground. We've already judged that there will be no catastrophic eruption during the operation period," the representative said.


There are cases in which claims of local residents calling for the halt of nuclear reactor operations have been accepted in the past on the grounds that officials' assumptions on the possible level of shaking from earthquakes under new safety standards are too lenient. Such was the case with an injunction issued by the Otsu District Court in March 2016 to halt the No. 3 and 4 reactors at the Takahama Nuclear Power Plant in Fukui Prefecture -- although the injunction was overturned by the Osaka High Court in March 2017.


The latest ruling in the Hiroshima High Court stated that the "new standards (for safety implemented after the Fukushima nuclear disaster), and the decisions by the NRA are reasonable." It also judged that estimates on other points of contention including earthquake ground motion, the maximum tsunami envisaged and countermeasures against serious accidents and terrorist attacks were "reasonable."


In response to the court's acknowledgement of the risks of a volcanic eruption, Hiroyuki Kawai, a lawyer representing the plaintiffs, commented, "The risks from volcanic eruptions extend to other nuclear power plants, and the framework of the Hiroshima High Court's decision can be applied laterally (to other nuclear power plant lawsuits)." Kawai predicted that the effects of the ruling would spread to Kyushu Electric Power Co.'s Sendai and Genkai nuclear plants, which are close to the Aso Caldera and Sakurajima in Kagoshima Prefecture, and Chugoku Electric Power Co.'s Shimane Nuclear Power Plant in the city of Matsue, which is near the volcano Mount Daisen.



December 15, 2017


EDITORIAL: Ruling on Ikata nuclear plant spotlights risk of volcanoes




A recent court ruling on the operation of a nuclear power plant in western Japan has raised fundamental questions about the safety of nuclear power generation in a country sitting on chains of volcanoes.


The Hiroshima High Court on Dec. 13 issued an injunction banning the operation of the No. 3 reactor at the Ikata nuclear power plant in Ikata, Ehime Prefecture, operated by Shikoku Electric Power Co.


The ruling referred to the possibility that the plant could be hit by a pyroclastic flow of superheated gases and debris produced by a huge eruption of Mount Aso, an active volcano in Kumamoto Prefecture.


The court decision is bound to have massive, wide-ranging repercussions since there are many other nuclear plants located close to a volcano in Japan.


The government’s Nuclear Regulation Authority (NRA), the nuclear safety watchdog, and utilities operating nuclear power plants should take the ruling seriously.


The NRA has developed internal guidelines for assessing safety risks posed to nuclear plants by volcanoes under the new nuclear safety standards introduced after the 2011 Fukushima nuclear disaster. The guidelines say areas within 160 kilometers from a volcano are not suitable for operating a nuclear power plant unless the risks posed by a possible eruption, such as an avalanche of extremely hot ash reaching the plant, are “sufficiently small.”


Many volcanologists argue that it is impossible to predict the timing and scale of large volcanic eruptions. But the NRA has approved plans to operate reactors near volcanoes submitted by utilities on the assumption that there should be telltale signs of a looming major eruption.


The high court based its decision on the view shared by many volcanologists that the possibility of a gigantic eruption of Mount Aso cannot be ruled out.


It is known that a supersized eruption occurred at the volcano some 90,000 years ago. The risk of an Aso eruption of a similar scale causing serious damage to the Ikata nuclear plant, located about 130 km from the mountain, cannot be dismissed as “sufficiently small,” the ruling said. The court judged the NRA’s conclusion that the plant has fulfilled the safety standards to be “not rational.”


In a nutshell, the court decided that the NRA failed to assess the safety of the plant strictly in line with the guidelines.


This is not the first time that a court has questioned the NRA’s approval of a plan to operate a nuclear reactor near a volcano.


In April last year, the Fukuoka High Court’s Miyazaki branch rejected an appeal against a lower court ruling allowing Kyushu Electric Power Co. to continue operating the Nos. 1 and 2 reactors at its Sendai nuclear power plant in Kagoshima Prefecture. Pointing out that huge volcanic eruptions rarely occur, the court argued that social common sense disregards the risk as negligible.


But the ruling nevertheless said the guidelines’ claim that such eruptions are predictable is “irrational.”


The fact that shortcomings in the way the NRA evaluates the risks posed to nuclear plants by volcanoes have been repeatedly pointed out by courts has significant implications.


The NRA should pay more serious attention to what volcanologists say and remake the guidelines from the ground up.


It is indeed difficult to reasonably assess the safety risks from gargantuan volcanic eruptions that occur only once in every tens of thousands of years.


The Hiroshima High Court’s ruling has raised the fundamental question of how society should deal with the threat of natural disasters.


Any catastrophic volcanic eruption would cause enormous damage over a wide swath of the nation.


Some people may say that debate focused on the effects of such an eruption on nuclear plants is of little use.


But the principal lesson we have learned from the catastrophic accident at the Fukushima No. 1 nuclear power plant is that failing to take measures to prepare for disasters that rarely occur could lead to irrecoverable damage.


The government, which has been promoting restarts of offline nuclear reactors, should remember this lesson and seriously consider whether it is really possible to operate nuclear power plants safely in a country dotted with so many volcanoes.


--The Asahi Shimbun, Dec. 15



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