'Ring of Fire' volcano risk the last obstacle for Japan's nuclear plants

(REUTERS) TOKYO — In the three years since the Fukushima disaster, Japan’s utilities have pledged $15 billion to harden their nuclear plants against earthquakes, tsunamis, tornadoes and terrorist attacks.

But as Japan’s nuclear safety regulator prepares to rule on whether the first of the country’s 48 idled reactors is ready to be come back online, the post-Fukushima debate about how safe is safe enough has turned to a final risk: volcanoes.

The Nuclear Regulation Authority (NRA) has already said the chance of volcanic activity during the lifespan of Kyushu Electric Power’s nuclear plant at Sendai was negligible, suggesting it will give it the green light. The plant lies in a region of active volcanic sites.

Critics, including some scientists who were consulted by the NRA, say that shows regulators are turning a blind eye to the kind of unlikely but potentially devastating chain of events that pushed the Fukushima Daiichi plant into a triple meltdown in 2011 when a tsunami crashed into the facility.

The debate has played out in several months of public hearings in Tokyo by the NRA and could weigh on the last hurdle for restarting nuclear plants - the opinion of local residents - at a time when the costs of keeping reactors shut are mounting.