London, June 17 (ANI): Reports indicate that a global network of sensors designed to verify nuclear testing has failed to pick up radioactive gases from North Korea’s nuclear blast, which indicates that the country might have used conventional explosives to mimic a nuclear test.

North Korea conducted what it claims was its second nuclear test on May 25 this year. Within seconds, a global network of seismographs had detected the shock wave from the blast.

The seismographs are operated by the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), a Vienna-based body that would enforce a global ban on nuclear testing if enough nations were to sign up to the treaty.

The CTBTO seismographs showed that the tremors caused by the explosion were of magnitude 4.5, far larger than the nation’s first nuclear test in October 2006.

According to a report in Nature News, the seismic signature of the test strongly suggested that the blast was man made, but the CTBTO hoped to use a follow-up set of measurements to verify its nuclear nature.

During nuclear fission, plutonium and uranium generate many lighter fission products, such as xenon isotopes. Unlike other nuclear debris, xenon, an unreactive noble gas, can filter out through fissures in the rock after an underground test.

Once in the atmosphere, plumes of xenon isotopes can be blown for thousands of miles.

So far, however, no monitoring stations have detected this test’s xenon signature, according to Lassina Zerbo, the director of the International Data Centre at the CTBTO.

What’s more, the likelihood of spotting anything is dropping fast because some xenon isotopes rapidly decay to levels that would make the signature appear similar to that generated by civilian nuclear power plants.

Zerbo points out that the CTBTO network is far more complete in 2009 than it was in 2006 and that all stations were operational at the time of the test.

“If we didn’t measure it, it’s unlikely that anyone outside of North Korea’s borders did,” he said.

The lack of isotopes has become an interesting puzzle for proliferation researchers. It could mean that the North Koreans used conventional explosives to mimic a nuclear test.

Such a mock test would be unusual, although not unprecedented.

In the 1980s, the United States government set off several multi-kilotonne chemical explosions to test how various weapons and communication systems would respond to a nuclear blast. (ANI)