Nosing Out Illegal Nuclear Tests Is Possible, Study Says

Inspectors might be able to sniff out an underground nuclear explosion that violates a test ban treaty, a study suggests.

Researchers who simulated a one-kiloton underground nuclear test found that gases seep to the surface through underground cracks.

The experiment used a mined cavity about 400 yards underground at the Nevada Test Site. Researchers put a bottle containing helium and another containing sulfur hexaflouride in the cavity and set off a chemical explosion there.

Monitoring stations were set up to look for the gases at the surface and just below ground. The sulfur hexaflouride was first detected 50 days after the explosion, and helium 325 days after that.

To look for evidence of a real nuclear explosion, inspectors would probably sample for argon-37 and xenon-133, the researchers said. Those gases aren’t produced in significant amounts naturally, and their short half-lives could be used to calculate when the blast occurred, the researchers said.

The work is presented in the Aug. 8 issue of the journal Nature by scientists at the Lawrence Livermore National Laboratory in Livermore, Calif.

It doesn’t prove that xenon and argon would always seep out from an illegal underground test, but the risk would provide “a great source of uncertainty for the cheat,” Lars-Erik De Geer of the National Defence Research Establishment in Stockholm, Sweden, wrote in an accompanying commentary.