CHINA'S main centres for designing, making and storing nuclear arms lie in the shattered earthquake zone, leading Western experts to look for signs of any damage that might allow radioactivity to escape.
A senior US official said Washington was using spy satellites and other means to try to monitor the sprawling nuclear plants. "There appear to be no immediate concerns," the official said.
China began building the plants in the 1960s, calculating their remote locations would avert enemy attack.
China's main complex for making nuclear warhead fuel, codenamed Plant 821, is in part of the earthquake zone, some 25 kilometres north-west of Guangyuan in Sichuan province. The vast site holds China's largest production reactor and factories that mine its spent fuel for plutonium - the main ingredient for modern nuclear arms.
Jeffrey Lewis, an arms control specialist at the New America Foundation, a non-profit research group in Washington, said the military buildings that make up Plant 821 were probably considerably stronger than civilian structures.
"I'd rather have been in the reactor building than a grade school" when the quake struck, he said. The site's various plants "were built as military facilities, and so I wouldn't be surprised if, by and large, they came through pretty well".
Closer to the epicentre of the quake that struck on Monday is Mianyang, a science city whose outskirts house the primary laboratory for the design of Chinese nuclear arms, considered the Chinese equivalent to the Los Alamos National Laboratory in New Mexico. Known as the Chinese Academy of Engineering Physics, it has centres throughout Sichuan province.
"I think this is not a no-cost moment for their labs but is not necessarily a human health risk," Dr Lewis, who visited Mianyang last summer, said of the academy's main facilities. "We should keep in mind that there is certainly stuff out in the hills that might have been more seriously damaged."
In rugged hills a two-hour drive west of Mianyang, for example, China runs a highly secretive centre that houses a prompt-burst reactor. It mimics the rush of speeding subatomic particles that an exploding atom bomb spews out in its first microseconds.
North, in an even more rugged and inaccessible region, nuclear experts said China maintains a hidden complex of large tunnels in the side of a mountain where it stores nuclear arms.
"It's very close to the epicentre," said one specialist.
Danny Stillman, a former director of intelligence at Los Alamos, said he had great regard for the Chinese weapons scientists and assumed many of the nuclear plants had been built to ride out disasters, natural or man-made.
"All the Chinese I met in the program were really brilliant," he said. "So I think they do it the right way. I hope."
The New York Times