Volcanism and nuclear safety in Japan.

Three years after the Tohoku earthquake / Japan, magnitude 9, and the tsunami that followed, causing the Fukushima nuclear disaster , the country is preparing to release the " nuclear zero " .

The Japanese reactors are reviewed by the NRA - Nuclear Regulation Authority - since 2013. This is the first time that the danger posed by volcanism is taken into account : new standards requires to consider the influence of volcanoes within a radius of 160 km. around the core .

Units 1 and 2 of the Sendai atomic central, on the island of Kyushu , could be the first to restart . Kyushu Electric has examined the effect of 39 volcanoes eruptions ... and concluded that it is sufficient to take action based on the assumption that the ashes of  Sakurajima near volcano would accumulate in the walls of the Sendai central to a height 15 cm . Generators are provided for the case where the power lines are damaged by the weight of the ash . What will happen if the supply of cooling water is impeded , plunging reactors in a manner similar to that experienced at Fukushima situation?

The reactors at the nuclear power plant of Sendai, on the island of Kyushu - photo 20 minutes.fr

The eruptive plume of Sakurajima August 18, 2013 - photo Kyodo news / Twitter

Without falling into the doom and gloom, we must remember the current activityof the Sakurajima on the rise . The eruption of May 11, was accompanied by a rising plume 4,500 meters. Although the frequent eruptions of the volcano have mostly effects on the island of Kagoshima , do not underestimate the possibility of a larger episode.

The central of Sendai is indeed surrounded by several calderas formed by collapse in previous catastrophic eruptions.

Tectonics should also be taken into consideration: Kyushu is cut by large faults, which MTL - the Median Tectonic Line - which runs from northern Honshu. The center of the island consists of an area of ​​subsidence , the Beppu - Shimabara graben .

Location map of the volcanoes of Kyushu / Japan - doc . GSI .

Median tectonic line and grabens of Kyushu ( plotted approximate) - from the tectonic map of South Japan / Wikipedia. Beppu - Shimabara graben : between green dashed - Kagoshima graben : among the purple dotted

Sources :

- Asahi Shimbun - 11.05.2014 - Threat posed by volcanic eruptions to nuclear plants must be carefully examined

- Asahi s-Shimbun - 17.03.2014 - Nuclear safety requires a multilayered defense system // Demonstrators turn out in force in Kagishima to oppose Sendai palnt restart.