The move has sparked fears of energy shortage after the Fukushima plant was crippled by the March tsunami [EPA]

Japan's Hamaoka nuclear plant is to be shut until it can be buttressed to withstand a tsunami as severe as the one which devastated the country's northeast coast in March, triggering the world's worst atomic crisis in 25 years.

Monday's decision by Chubu Electric Power Co, Japan's third biggest power operator, to close the plant situated 200km southwest of Tokyo followed a request by Naoto Kan, the prime minister.

Government experts put the chance of a magnitude 8.0 quake hitting the Hamaoka area in the next 30 years at 87 per cent, which has raised questions over why it was built there in the first place.

"By halting the Hamaoka nuclear plant, we are causing great short-term trouble to not only those in the plant area but also many others including our customers and our shareholders," Akihisa Mizuno, Chubu Electric president, told a news conference.

"But firmly implementing measures to strengthen safety would become the cornerstone to continue safe and stable nuclear power in the long-term and in the end lead to the benefit of our customers."

The 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.

The move signals a potential shift in energy policy after the Fukushima Daichi plant in the northeast was damaged by a giant tsunami triggered by one of the biggest earthquakes ever recorded on March 11.

Reopening Hamaoka could take two years, raising the risk of a shortage of electricity after the Fukushima plant was shut down by the tsunami. 

Government under pressure

Chubu said it could restart the plant once its tsunami wall and other safety steps had been approved by the authorities.

Another power operator said it had discovered a tiny amount of leaked radiation at its Tsuruga plant on the west coast. The revelation raised more public concern over an industry that supplies about 30 per cent of the quake-prone country's electricity.

Japan Atomic Power, however, said it had stopped the leak and that there had been no impact on the environment.

The government is under heavy pressure to review its energy policy after the March quake and tsunami crippled the Fukushima nuclear power plant run by Tokyo Electric Power.

Nearly 26,000 people were killed or are unaccounted for following the natural disaster which triggered the world's biggest nuclear crisis since Chernobyl in 1986. The plant is still leaking radiation.

Banri Kaieda, the trade minister, said the government would consider bearing the cost of closing the plant if requested by Chubu.

The company's shares were down 11 per cent at $19 in afternoon trade, after falling as low as $18. Chubu's tumble helped push Tokyo's electric and gas subindex down 2.7 per cent.

"This news is triggering uncertainty not just about Chubu Electric but the whole utility sector," said Yoshinori Nagano, a senior strategist at Daiwa Asset Management.

Source: Agencies