Japan lies in what’s know as a “Ring of Fire.” It’s a 40,000 km (25,000 mile) horseshoe-shaped basin consisting of a super-mix of fault lines, oceanic trenches, volcanic belts, and volcanic arcs. Of the roughly, 1,500 active volcanoes in the world, around 110 of them are here. In Japan, there will always be a risk wherever you plonk a nuclear power plant.
“The Sendai nuclear plant is sufficiently distant from the Sakurajima and Kirishimayama volcanoes to be safe from the direct impact of destructive phenomena such as lava flows or pyroclastic flows, but could be affected by ash fall during a sufficiently large eruption, and provided the wind is blowing in its direction,” Bill McGuire, a leading British volcanologist and Emeritus Professor of Geophysical & Climate Hazards at University London, told me in an email.
“Ash is a rather unspectacular hazard, but can cause major problems through clogging filters and machinery and infiltrating sensitive electrical and electronic systems.”
Still, while 10,000 years might seem pretty epic when viewed along a human timescale—according to Charles B. Connor, a volcanologist at the University of South Florida, you definitely need to think about that time frame when you’re building a powerful nuclear reactor.
“Volcanologists don’t know much about the time scales or precursory activity to large eruptions as we don’t get a chance to observe them so often,” Connor, told me over the phone. “That’s an issue—we treat their eruptions probabilistically.”
McGuire and Connor explained that there are several examples of nuclear power plants worldwide, built according to calculations based on the probability or large-scale volcanic eruptions happening or not. “Often, even though the natural hazard is clear, the facility is still built. Short-termism and the profit motive remain powerful drivers,” McGuire told me.