The Sendai nuclear power plant located in Kagoshima Japan has been selected as the one Japanese authorities would focus on attempting to approve for restart. Sendai includes two PWR type reactors. Intakes reside at: 5ft above sea level Intake pump buildings 13 feet above sea level Reactor blocks at about 35-40 ft above sea level
Road routes are problematic at the plant. The plant is bordered by a large river to the north, the sea to the west and a large expanse of mountains to the east. Roads route either north along the river or south following the coastline a considerable distance before you reach an area that might be undamaged. The south road has various locations that could be subject to tsunami damage or landslide damage.
Major roads shown in yellow. Kagoshima sits facing the Sakurajima volcano. This could potentially render it unavailable for a major response. The major road that routes towards Sendai crosses the river north of the plant before a road to get to the plant could be reached, requiring another trip across the river. Miyazaki sits further to the east but again requires a north route and river crossing.
The even bigger challenge is that the conditions that would take out offsite power can’t be overcome. Issues with clogged generator intakes would also plague any new generators brought on site. The problem would persist until ash from the volcano ceased and what is in the air would settle. There really isn’t any way to prevent or subvert this very big act of nature. Sakurajima isn’t some abstract threat. The volcano is still very active, it has a current “orange” status indicating it is active and people should not approach it. It ejected a large plume of ash in August of 2013. That had been the 500th eruption for the year and was just past the half way point of 2013.
The problems a volcano can cause a nuclear power plant is a well known problem. A buildup of dust or ash can cause power line equipment to arc and fail. This happened at the Diablo Canyon nuclear plant in the US recently. This USGS informational page on volcanoes explains in depth how volcanic ash can knock out power to widespread areas. Ash can also cause mechanical damage to anything with moving parts that the ash may get into including pumps and generators.
Read more at The Real Risks at Sendai