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http://www.thestate.com/mld/thestate/news/15672722.htm?source=rss&channel=thestate_news

Posted on Wed, Oct. 04, 2006

A nuclear test by North Korea carries radiation risk

By GEORGE JAHN
The Associated Press

Any miscalculation by North Korea in the design of its nuclear test could release radiation into the atmosphere that could travel far beyond North Korea’s borders, experts say.

With Pyongyang’s nuclear activities off limits to the outside world for the past 13 years, much of the secretive country’s expertise and nuclear sophistication is a matter of guesswork. And if the North is not as advanced as it thinks it is, the possibility of mistakes cannot be discounted.

The suspected underground test site, near the town of Chiktong, is dug into the side of a mountain and likely zigzags down at an angle with a series of sharp turns and blast doors meant to contain the force of the explosion. The point of entry would be sealed before any explosion is set off.

But former U.N. nuclear inspector David Albright, president of the Washington-based Institute for Science and International Security, said Tuesday any flaws in the site’s design could “blow everything out of the entrance,” including substantial amounts of radioactivity.

Another potential error that could send clouds of radioactivity into the air — and ultimately far beyond North Korea’s borders — could be a miscalculation in the yield of the explosion.

The limited nuclear sophistication of the North Koreans means they would aim to make a test bomb no larger than five kilotons, he said. That would produce an explosion three to four times weaker than the bombs that destroyed the Japanese cities of Hiroshima and Nagasaki during World War II.

“But if they (inadvertently) over-designed the thing that could be a worry,” Albright said. “If it’s 30 kilotons, it could blow a hole in the mountain, and if there is a fissure, radiation will escape.”

Albright said the chances of miscalculation either in bomb or tunnel design that is major enough to set free large amounts of radioactivity were small, but could not be ruled out.

Satellite imagery of the potential test site near Chiktong taken May 1 shows what appears to be a tunnel entrance to the northwest of a ridge and an equipment storage site on the ridge’s southeastern flank. Another photo identifies “suspected V.I.P housing” and a “suspected helipad” near the site.

Albright said that what appears to be rolls of cable near the site could mean the North is preparing a test, with the wiring possibly connecting a nuclear device inside the tunnel to a monitoring site.

The bomb would be set of electronically. If that happens, “the mountain will shake, and they’ll be sending (seismic signals) that will be detected in China, maybe Japan, certainly in South Korea,” said Albright. The residents of Chiktong, about 10 miles away, “would feel a shaking,” he added.

Albright’s comments reflected the guesswork connected to what North Korea can and cannot do since it unilaterally withdrew in 2003 from the Nuclear Nonproliferation Treaty and expelled inspectors of the International Atomic Energy Agency.

Pyongyang last year announced it had nuclear arms — a claim that, like most others connected to its atomic activities — cannot be verified. Still, the North is believed to have enough fissile material to arm at least half a dozen warheads.