Chubu Electric said Friday it will build an 18-metre (60 foot) anti-tsunami seawall to protect its ageing Hamaoka nuclear plant located near a faultline in a region seen as vulnerable to earthquakes.
The decision came two months after the government asked the plant to shut down and add new disaster-mitigation measures amid deepening public fears about the safety of nuclear power in the wake of the Fukushima Daiichi crisis.
The plant's operator Chubu Electric Power said the seawall and other additional safety measures should protect the plant from a tsunami as strong as the one that crippled the Fukushima plant on after the March 11 earthquake.
The Hamaoka plant faces the Pacific Ocean and sits in the Tokai region, southwest of Tokyo, where seismologists have long warned that a major quake is overdue.
Anti-nuclear campaigners argue that the seismically unstable area, where two major continental plates meet, makes Hamaoka the most dangerous atomic facility in the quake-prone country.
Chubu Electric will spend about 100 billion yen ($1.3 billion) on the 1.6-kilometre (1 mile) wall, steps to prevent flooding inside the plant, and programmes to safeguard cooling systems that bring reactors to safe shutdown in case of severe accidents.
An earthquake as strong as 9.0 in magnitude, as it was on March 11, could cause a 10-metre tsunami near Hamaoka, Chubu Electric said.
The five-reactor Hamaoka plant accounts for almost 12 percent of the output of Chubu Electric, which serves a large part of Japan's industrial heartland, including many Toyota auto factories.
After the twin earthquake and tsunami disaster, Chubu Electric planned to build a more than 12-metre-high seawall at the Hamaoka plant.
But it revised the that and decided to build an 18-metre-high wall, taking into consideration that 15 metre-high tsunami waves tore into the Fukushima Daiichi plant operated by Tokyo Electric Power Co.
The Fukushima crisis has forced the evacuation of tens of thousands of area residents, devastated the local commerce and farming, and caused a nationwide food contamination scare.
Explore further: Next-generation nuclear reactors that use radioactive waste materials as fuel