• Kyodo

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As Japan edges closer to the first restart of a nuclear plant under new tighter regulations, experts warned on Monday that it’s difficult to predict volcanic hazards and called for more debate on the risks posed by volcanic eruptions.

Last month, the Nuclear Regulation Authority said the risks of volcanic eruptions around the Sendai plant — located in a region of active volcanic sites in Kyushu — are negligible during its life span.

It was a safety nod that hinges on the plant’s operator, Kyushu Electric Power Co., continuing to monitor the state of volcanoes and taking appropriate measures if any signs of change are observed.

At Monday’s expert panel meeting, however, scientists said there are no established ways to predict future volcanic eruptions, and even when signs of changes are noted, their interpretation is still open to debate.

“It is extremely difficult to predict the timing and the scale of massive volcanic eruptions” with current knowledge in volcanology, said Setsuya Nakada, a professor at the Volcano Research Center at the University of Tokyo.

Another academic claimed that the primary overseas study cited by Kyushu Electric and the NRA to support their arguments only covers a specific caldera volcano, and it cannot be generalized and applied to other volcanoes.

“It is extremely risky” to conclude that the possibility of volcanic eruptions around the Sendai complex is small enough “only on the basis of one study,” said Toshitsugu Fujii, an honorary professor of volcanology at the University of Tokyo.

The Sendai plant is located about 50 km from Mount Sakurajima, an active volcano. There are five calderas around the complex.

The odds of an eruption that give rise to a caldera, or a large crater formed by the collapse or explosion of a volcano, are rather slim, but the potential damage could be devastating.

The NRA could order the operator to close down the plant or move fuel out in the event of emergency, but what measures should be taken on what criteria remains uncertain.

NRA Commissioner Kunihiko Shimazaki said at the meeting the regulator will “cope with the matter with responsibility.”

On July 16, the NRA decision-making panel approved a draft report on the outcome of safety screenings on the Nos. 1 and 2 reactors at the Sendai nuclear power station.

The regulator is expected to release the final version of the document possibly this month. The reactors would be the first among Japan’s 48 idled commercial units to meet the new regulations introduced following the triple meltdown at the Fukushima No. 1 nuclear plant.

The two-unit Sendai plant is set to go back online after undergoing some other checks. But a restart also hinges on securing local consent, and the restart is not expected before this winter at the earliest.

The expert panel on volcanoes will continue discussions on how to monitor possible signs of volcanic hazards, but it will not affect the results of the safety screening, an NRA official said.

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