If an underground explosion occurs anywhere in the world, there is a good chance that a seismologist can pinpoint it. However, they won’t necessarily be able to tell you what kind of explosion had occurred—whether it is chemical or nuclear in nature. New research from Pacific Northwest National Laboratory (PNNL) scientists makes detecting nuclear explosions easier.
“To a seismologist, chemical and nuclear explosions look identical,” said Harry Miley, Laboratory Fellow and physicist in the National Security Directorate at PNNL. “Radionuclide detection technologies, like the PNNL-developed Xenon International and Radionuclide Aerosol Sampler/Analyzer, known as RASA, can discriminate between the two by detecting radioactive atoms that are created in nuclear explosions. However, we have very little scientific understanding of the geologic containment of these atoms following an explosion.”
When an underground explosion occurs, gases travel through fractures in the ground and escape into the atmosphere. Instruments such as Xenon International and RASA can then detect radionuclide gases, but their chemical signatures may be greatly affected by rock damage that the gases must pass through.
Earth scientist Hunter Knox and computational scientist Tim Johnson at the Earth Systems Science Division at PNNL showed up in Miley’s office one day proposing to investigate the effects of rock damage patterns on gas flow paths. The results, recently published in Pure and Applied Geophysics, have been transformational for understanding subsurface gas flow.
Hidden within the exit paths taken by these post-explosion gases are clues to their origin. Monitors around the globe can detect tiny amounts of radionuclides in the atmosphere but cannot differentiate between a radioactive isotope from an explosion or from other activities, such as the production of medical isotopes.
“This research helps us with timing – if a nuclear explosion occurs, when should we expect to detect the radioactive gases it produces? Coupling this information with seismologic data and radionuclide detection can reduce uncertainty in determining if an explosion is chemical or nuclear in nature,” said Johnson.
Ultimately, this research augments existing global nuclear non-proliferation efforts to keep citizens safe.