9 Octobre 2014
October 9, 2014
The eruption of Mount Ontakesan has raised questions about the ability of nuclear power plants to operate safely in the vicinity of active volcanoes.
The Sept. 27 disaster claimed more than 50 lives. It was a grim reminder that Japan, with 48 nuclear reactors, is studded with 110 active volcanoes. Several reactors are to be decommissioned. There are fears their nuclear fuel could leak if the facilities were damaged in a volcanic eruption.
Not enough attention has been given to this risk in assessing whether certain sites are suitable for the construction of a nuclear reactor or the safety standards concerning the structure and operations of nuclear facilities.
Given the current level of volcanology, there is no way to accurately predict volcanic eruptions.
Some nuclear plants are located in high-risk areas, such as the Sendai nuclear power plant in Kagoshima Prefecture. It is surrounded by volcanoes with a history of massive eruptions.
The safety of these plants should be carefully reassessed to determine whether they should continue operating.
The catastrophic accident at the Fukushima No. 1 nuclear power plant in 2011 underscored the fact that Japanese nuclear plants were not prepared to withstand a battering by towering tsunami.
The triple meltdown at the Fukushima plant prompted the Nuclear Regulation Authority to reassess the safety of nuclear reactors against all sorts of natural disasters and revised the regulatory standards accordingly. The new standards require operators of nuclear power plants to take appropriate safety measures commensurate with the risk of an accident caused by volcanic eruptions.
The actions taken by the nuclear regulator are reasonable in themselves.
The eruption of 3,067-meter Mount Ontakesan was actually quite minor. Even so, it aroused a lot of anxiety.
Volcanic eruptions can result in a magmatic explosion or create a caldera, a cave-in formed by the collapse of land. This, clearly, could be a major problem. Volcanic ash or massive pyroclastic flows could render nuclear plants uncontrollable.
Shunichi Tanaka, chairman of the Nuclear Regulation Authority, referred to safety concerns raised by the Mount Ontakesan eruption during a news conference, saying, “It is unscientific to discuss different events at the same time.”
He was pointing to the differences between the Mount Ontakesan eruption and huge volcanic events that could be more predictable.
Still, the fact remains that it is next to impossible to accurately predict the timing and scale of any volcanic eruption. This is the essence of the risk posed by volcanoes with regard to the safety of nuclear power plants.
Volcanoes are believed to remain active for several hundreds of thousands of years. The modern science of observing volcanic eruptions spans only a few decades, or roughly one-10,000th of the period during which some volcanoes are active.
Despite these facts, Kyushu Electric Power Co. is pushing to resume operations of its Sendai nuclear power plant. The utility has expressed confidence in the safety of the facility.
It insists that the possibility of a huge eruption while the Sendai plant is operating is acceptably low. The company also says it would be possible to detect signs of a major eruption and remove the nuclear fuel beforehand.
The nuclear watchdog has supported the utility’s position.
Using the human analogy, what the utility says can be likened this way: After observing a person, who is expected to live to be 80 years old, for only three days, during which you have not seen the person sneeze, you could state, “Considering the degree and frequency of his past sneezing, we can say he will not sneeze for the time being. We will certainly know in advance when he actually sneezes.”
A lot more scientific research is needed to understand volcanoes. But we should not put too much hope on such research in preparing for volcanic disasters.
It is said that major eruptions have occurred in the Japanese archipelago about once every 10,000 years. When the next big eruption will occur is anybody’s guess.
If a nuclear power plant is seriously damaged by such an eruption, the entire world, not just Japan, would be exposed to a grave threat.
--The Asahi Shimbun, Oct. 9