Japan urged a power company Friday to suspend all three reactors at a coastal nuclear plant while a seawall and other structures are built to ensure a major earthquake or tsunami does not cause a second radiation crisis.
The move came as the government is conducting a safety review of all Japan's 54 nuclear reactors after the Fukushima Dai-ichi nuclear plant was crippled by the March 11 earthquake and tsunami that left more than 25,000 people dead and missing on the northeast coast.
The Hamaoka nuclear plant just 110 yards (100 meters) off the Pacific coast in central Japan is the only one so far where the government has asked that operations be halted until the utility can implement safety measures.
Chubu Electric Power Co. said in a statement it will "swiftly consider" the government's request. The statement gave no further details. Government officials estimate the work could last two years.
Prime Minister Naoto Kan said at a news conference Friday evening he requested the shutdown for safety reasons, citing experts' forecast of a 90 percent probability of a quake with magnitude of 8.0 or higher striking central Japan within 30 years.
"It was a decision made after thoroughly considering people's safety," Kan told a news conference.
The government asked Chubu Electric to suspend two running reactors and a third already shut for a regular inspection at the plant in Shizuoka, around 124 miles (200 kilometers) west of Tokyo.
"If there were a major accident at Hamaoka nuclear plant, it would have an enormous impact on the entire Japanese society," Kan told a televised news conference.
Since the March 11 disasters, Chubu Electric has drawn up safety measures that include building a seawall nearly a mile (1.5 kilometers) long over the next two to three years.
"The height of the seawall is at least 12 meters. We have come up with this safety measure after the March quake and tsunami," said Takanobu Yamada, an official at Chubu Electric.
The company also planned to erect concrete walls along 18 water pumps at the plant. Yamada said the walls aimed to protect the pumps from damage from an earthquake and tsunami, and it will take a year or one and a half years to complete the construction.
The plant does not have a concrete sea barrier now, but sandhills between the ocean and the plant are about 32 to 50 feet (10 to 15 meters) high, according to the company.
The seawall of at least 40 feet (12 meters) would be built between the sandhills and nuclear plant over the next two to three years. Yamada said Chubu Electric has estimated a tsunami reaching around 26 feet (8 meters).
"This is a bold move by the Kan administration and I am very surprised they would go as far as to ask for a nuclear plant to be shut simply because an earthquake could occur in its vicinity sometime during the next 30-40 years," said Osamu Fujisawa, an oil economist at industry consultant FE Associates.
"Obviously Chubu's power generation costs will rise since they will have to use more oil and natural gas, but they will likely be able to secure enough power by restarting mothballed oil plants and buying electricity from other utilities."
But Trade Minister Banri Kaieda argued Chubu's safety measures were "not enough."
"Until the company completes safety steps, it is inevitable that it should stop operating nuclear reactors," Kaieda said.
Tokyo Electric Power Co., operator of the stricken Fukushima plant, has said the waves that wrecked critical power and cooling systems there were at least (46 feet) 14 meters high.
Shizuoka governor Heita Kawakatsu called the government's move "a wise decision."
"I pay my respect for the decision. We must do our utmost to secure alternative sources of energy," the governor said in a statement.
Residents in Shizuoka have long demanded suspension of the Hamaoka reactors. Around 79,800 people live within a 6.2-mile (10-kilometer) radius of the plant, according to Shizuoka government figures.
The plant provides power to around 16 million people in central Japan. Faced with a possible power crunch due to the shutdown, the prime minister sought public understanding.
"We will experience some power crunch for sure. But we can overcome this with public support and understanding," Kan said.
The region powered by the plant includes Aichi, where Toyota Motor Corp.'s headquarters and an auto plant are located. Automakers and other industries have had troubles with interrupted supply lines, parts shortages and damage to manufacturing plants since the March 11 disaster.
The Fukushima Dai-ichi nuclear plant lost its power and cooling systems in the earthquake and tsunami, triggering fires, explosions and radiation leaks in the world's second-worst nuclear accident.
Radiation leaks have forced 80,000 people living within a 12-mile (20-kilometer) radius of the plant to leave their homes. Many are staying in gymnasiums and community centers.
Since the Fukushima crisis unfolded, Associated Press investigations have found that TEPCO underestimated the tsunami risk there and that a revolving door of top officials between government regulators and industry allowed a culture of complacency to prevail.
TEPCO submitted an analysis to Japan's Nuclear and Industrial Safety Agency in 2001 that waves would not exceed 5.7 meters (18 feet) at the Dai-ichi plant. The model was based on a quake of 8.6-magnitude, while a 9.0 was what occurred, and it assumed the backup power generators would stay dry.
TEPCO didn't disclose the underlying data behind its assumptions, and NISA, the government regulator, did not scrutinize the calculations, AP's investigations found.
TEPCO crews on Friday increased the amount of water being injected into the crippled No. 1 reactor in an effort to stably cool the damaged nuclear fuel inside, Kyodo News reported.