- - Monday, May 9, 2011

TOKYO | A Japanese utility agreed Monday to close three nuclear reactors at a coastal power plant in central Japan and build a sea wall to protect it from a tsunami like the one that devastated much of the northeast in March.

Chubu Electric Power Co. acted after Prime Minister Naoto Kan requested the temporary shutdown at the Hamaoka plant amid concerns that an earthquake of magnitude 8.0 or higher could strike the central Japanese region sometime within 30 years.

The company had resisted pressure from thousands of protesters in the largest demonstrations in Japan in 40 years in the weeks after the nuclear disaster at the Fukushima reactors, owned by the Tokyo Electric Power Co.

In making the shutdown request on Friday night, Prime Minister Naoto Kan cited Science Ministry predictions of an 87 percent chance over the next 30 years of an earthquake larger than 8.0 magnitude striking the Tokai areas including Shizuoka and Aichi prefectures in Japans automotive heartland.


On Monday he praised Chubus decision, and promised to help Chubu avoid losses and power shortages while it improves safety measures.

Many observers, however, are questioning whether any wall, no matter how high or wide, can really block out the Pacific Ocean, which spawns tsunamis devastating Japan roughly every 20 years on average.

On March 11, a 400-mile long mountain of water, racing across the Pacific Ocean at jet speed, easily breached or destroyed some of the worlds strongest and most expensive sea walls, near the ports of Kamaishi and other cities. In Minami-Sanriku and Rikuzen-Takata, sea surges more than 40-feet high obliterated nearly everything in their path, pulverizing concrete buildings and mangling structures made of steel even three miles inland.

Tokyo University researchers even found that the tsunami in Miyako city ran up slopes to a point more than 110-feet above sea level.

Japan is destined to always be hit by tsunamis, and the Tokai region is the riskiest area in Japan,” Goshi Hosono, a special adviser to Mr. Kan and a member of parliament from Shizuoka, home to the Hamaoka reactors, said Monday.

“We are one of the best-prepared regions for earthquakes, but not as much serious thought has been given to tsunamis.”

Japans seismic experts had opposed the Hamaoka plant even before construction began in 1971. In 2004, professor Katsuhiko Ishibashi, a former member of a government nuclear safety panel, called Hamaoka the most dangerous nuclear plant in Japan.

Seismologists point to Dec. 23, 1854, and the 8.4 magnitude Ansei quake and tsunamis that destroyed much of the Tokai area in Shizuoka prefecture from Numazu to Hamamatsu cities, which flank Omaezaki, currently site of the Hamaoka reactor and about 80,000 people in a six-mile radius.

Scientists believe that tectonic movement along the same zone caused the 1923 Great Kanto quake, which spawned 36-foot-high tsunamis near Tokyo and Yokohama, and two quakes and tsunamis in the 1940s.

Since the March 11 disasters, Chubu Electric officials say they have drawn up plans to install more backup generators and build a 40-foot-high seawall nearly a mile long over the next two to three years.

“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,” Chubu President Akihisa Mizuno told a news conference at its headquarters in Nagoya.

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