The operator of Japan's Hamaoka nuclear plant, located near a tectonic faultline southwest of Tokyo, said on Monday it would shut down its reactors as requested by Prime Minister Naoto Kan.
Kan last Friday called for the closure of the plant, eight weeks after a massive quake and tsunami damaged the Fukushima Daiichi nuclear plant Northeast of Tokyo, sparking the world's worst atomic crisis since Chernobyl in 1986.
Seismologists have long warned that a major quake is overdue in the Tokai region southwest of Tokyo where the Hamaoka plant is located. It is only 200 kilometres (125 miles) from the capital and megacity of Tokyo.
The Hamaoka plant has five reactor units, but only two are currently running — numbers four and five. Reactors one and two, built in the 1970s, were stopped in 2009, and three is undergoing maintenance.
"We have decided to halt operations of the number four and five reactors and postpone the restart of the number three reactor at the Hamaoka nuclear power plant," said Chubu Electric Power Co. President Akihisa Mizuno.
"We consider that the Prime Minister's request was very serious," he said, announcing the decision after an extraordinary board meeting.
He promised that "we will implement reinforcement measures against tsunamis and explain them to regain public trust".
The Hamaoka plant accounts for almost 12 per cent of the output of Chubu Electric, which services part of Japan's industrial heartland, including many Toyota auto factories.
Kan said the plant should stay shut while a higher sea wall is built and other measures are taken to guard it against a major quake and tsunami. Local media said the suspension would last about two years.
Japanese anti-nuclear campaigners have long argued that the seismically unstable area, where two major continental plates meet, makes Hamaoka the most dangerous atomic facility in the quake-prone Japanese archipelago.
Japan, the world's number three economy, endures 20 per cent of all major earthquakes and generates about 30 per cent of its power from nuclear plants.