WORLD NEWS_ International Assessment of Seismic Risk .

JULY 19, 2011.
International Assessment of Seismic Risk .

By REBECCA SMITH And MARK MAREMONT

Internationally, concern about seismic risks for nuclear power plants began climbing years before the March earthquake in Japan, but actually making the plants more quake-proof will take a long time.

At Fukushima Daiichi, on the east coast of Japan, the plant owned by Tokyo Electric Power Co. had prepared for a maximum likely quake of about magnitude 7.8, but was overwhelmed by a far more powerful 9.0 offshore temblor and the associated tsunami in March. Although most experts believe the tsunami did most of the damage, not ground shaking from the earthquake, some said the catastrophe underscores the need for conservatism in earthquake risk analysis and nuclear-plant design.

Concerns about seismic risks around the world began mounting back in 2007, after a magnitude 6.6 earthquake struck close to another major Japanese nuclear complex, unleashing ground shaking greater than the plant was designed to handle. The quake set off flooding and a fire that the local fire department had to extinguish, but didn't cause any radioactive release. Several reactors still were shut down when the giant quake struck off Japan's coast in March.

The 2007 event "was a big wakeup call," said Antonio Godoy, who at the time headed the International Atomic Energy Agency's seismic safety center. "It was clear there was an underestimation of the risk." He said around the world there was a "wave of interest" in re-evaluating the seismic risk to nuclear plants.

That was particularly true in Japan, where 24 of the nation's 54 reactors are located in high-hazard earthquake areas. Globally, 34 reactors, or 8% of the world's total, are in high-hazard areas. An additional 90 are in seismic zones that have been regarded as moderately risky.

Older nuclear power plants have been upgraded in several nations due to seismic hazard. Hungary's Paks nuclear power plant, with four reactors, was designed for a modest earthquake hazard. But the risk was "radically modified" in 1993 after updated seismic assessments found the potential ground shaking could be many times higher, according to the IAEA.

With the help of the IAEA, the Hungarian government strengthened Paks over eight years, adding vibration dampers, large structural reinforcers and other upgrades.

Write to Rebecca Smith at rebecca.smith@wsj.com and Mark Maremont at mark.maremont@wsj.com

More
. Earthquake Risks Probed at U.S. Nuclear Plants


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1 comment

5 hours ago.
JONATHAN KATZ wrote:
Earthquakes aren't a threat to power plants. Tsumanis are, if you are fool enough to put them, and their backup power supplies, in a tsunami zone.

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