Nuclear weaponsHelping inspectors locate and identify underground nuclear tests
Through experiments and computer models of gas releases, scientists have simulated signatures of gases from underground nuclear explosions (UNEs) that may be carried by winds far from the point of detonation. The work will help international inspectors locate and identify a clandestine UNE site within a 1,000 square kilometer search area during an on-site inspection that could be carried out under the Comprehensive Nuclear Test Ban Treaty.
Through experiments and computer models of gas releases, Lawrence Livermore National Laboratory scientists have simulated signatures of gases from underground nuclear explosions (UNEs) that may be carried by winds far from the point of detonation.
The work will help international inspectors locate and identify a clandestine UNE site within a 1,000 square kilometer search area during an on-site inspection that could be carried out under the Comprehensive Nuclear Test Ban Treaty. Jordan recently hosted such a simulated inspection, the Integrated Field Exercise 2014 (IFE14), sponsored by the Comprehensive Test Ban Treaty Organization (CTBTO) and involving more than 40 countries, which tested some aspects of noble gas signature detection.
LLNL notes that in addition, the technique can potentially help interpret noble gas (radioactive xenon isotopes) signals captured in the atmosphere following UNEs such as the North Korean test that occurred in January.
The research also led to the development of the LLNL Smart Sampler, which was originally designed as a research instrument to automatically capture gases reaching the surface in remote locations following release of gas tracers underground. During its IFE14 exercise, the CTBTO deployed three of these samplers, which were designed and built by Lab engineers Steven Hunter and David Ruddle at LLNL.
The work combines novel field experiments involving injection of gas tracers using four large compressors into an old nuclear explosion cavity and sophisticated numerical simulations that employ a new method for tracking different parent/daughter isotopes produced in the detonation cavity. The simulations use the results of the field experiment as a basis for probing the isotopic evolution and gas transport processes of a UNE.
The team, made up of scientists from LLNL and National Security Technologies (NSTec), partially reproduced the subsurface conditions following a UNE responsible for the migration of explosion gases to the surface where they can be detected locally at a test site. Such results can provide inspectors with a better idea of what to expect when they are in the inspection area searching for a suspected UNE. With LLNL computer models using information from the tracer experiment, the team was able to track the evolution of gases in the explosion cavity, which may be detected downwind thousands of kilometers away. This actually occurred after the third North Korean UNE in 2013.
