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Asia's nuclear reactors face tsunami risk

April 19, 2011

At least 32 plants in operation or under construction in Asia are at risk of one day being hit by a tsunami, nuclear experts and geologists warn. — File Photo

JAKARTA: The skeleton of what will soon be one of the world’s biggest nuclear plants is slowly taking shape along China's southeastern coast right on the doorstep of Hong Kong’s bustling metropolis.

Three other facilities nearby are up and running or under construction.

Like Japan’s Fukushima Daiichi plant they lie within a few hundred miles (kilometers) of the type of fault known to unleash the largest tsunami spawning earthquakes.

Called subduction zones, these happen when one tectonic plate is lodged beneath another. And because the so-called Manila Trench hasn't been the source of a huge quake in at least 440 years, some experts say tremendous stresses are building, increasing the chances of a major rupture.

Should that happen, the four plants in southern China, and a fifth perched on Taiwan's southern tip, could be in the path of a towering wave like the one that struck Fukushima.

“We have to assume they'll be hit,” said David Yuen, a University of Minnesota professor who has modeled seismic probabilities for the fault. “Maybe not in the next 10 years, but in 50 or 100 years.” Asia, the world's most seismically charged region, is undergoing a nuclear renaissance as it struggles to harness enough power for its huge populations and booming economies.

But China, Taiwan, India and several other countries frantically building coastal facilities have made little use of new science to determine whether these areas are safe. At least 32 plants in operation or under construction in Asia are at risk of one day being hit by a tsunami, nuclear experts and geologists warn.

And even when nations have conducted appropriate seismic hazard assessments, in many cases they have not shared the findings with the UN International Atomic Energy Agency, leaving experts frustrated and in the dark.

“It’s pretty astonishing to a lot of us that so little priority is placed on the work we do,” said Kerry Sieh of the Earth Observatory of Singapore, who has studied and written about the Manila Trench, where pressure has been building for millions of years.

He is among those who say it is only a matter of time before it snaps.

In assessing the tsunami risks to nuclear power stations, scientists focus on their proximity to subduction faults, volcanoes and areas frequently hit by underwater landslides all of which can trigger seismic waves. Because giant tsunamis recur, they also look at historic and scientific records, going back up to 4,000 years if possible.

The greatest threat comes from the subduction faults crisscrossing the globe, some far from the minds of policymakers, nuclear industry officials and the public because it has been so long since they exploded.

In places where tectonic plates that form these faults are ''coupled,'' or stuck together, the stresses are the biggest, especially if centuries have passed without a major energy releasing earthquake.

When the strain eventually forces one plate to pop up or dive under the other, the resulting temblor can spawn mammoth waves like the one that struck off Japan's northeast coast on March 11, triggering the nuclear crisis that has carried on for more than a month.

While there is some ''coupling'' at the Manila Trench, there is debate about just how much. Scientists say more research needs to be done to determine if pressure is building and along which segments.

A computerized simulation by Yuen's students shows a magnitude-9.0 quake along the Manila Trench sending waves racing along the South China Sea, before slamming Taiwan's southern shore 15 minutes later. The tsunami reaches China's southeast coast in around two hours. It also strikes Hong Kong, which sits just 30 miles from the nearest nuclear plant close enough to see increased radiation levels if a plant were to be damaged by a Fukushima-like event.

Scientists paint a worst-case scenario in which waves 15 to 24 feet high (5 to 8 meters) could strike the plants in China and Taiwan.

Science has come a long way since the first nuclear plant was built in the 1950s.

By carbon dating the ash, pollen or other organic material attached to tsunami sand deposits swept inland with the giant walls of water, geologists can determine to the decade, and sometimes even the year, when the wave hit and how big it was when it roared ashore.

That’s important because some tsunamis only strike once a millennium.

“This is the smoking gun, the calling card of the tsunami, and when you find it, especially far inland, you know that this is an area that has been hit with a large tsunami in the past,” said Bruce Jaffe, an oceanographer and tsunami expert at the U.S. Geological Survey.

Such research is considered essential in deciding where to locate nuclear power stations because most are built along seashores, rivers and lakes to supply the massive amounts of water needed to keep their reactors cool.