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From Source to Receiver: Numerical Simulations of Underground Explosions, Cavity and Chimney Formations, Subsurface Gas Transport and Prompt Atmospheric Releases

Description: 

Radionuclide monitoring is complementary to seismic, hydroacoustic, and infrasound monitoring techniques used in verification, and it is the only one that can discriminate and confirm whether an explosion is indicative of a nuclear explosion. To understand radioactive noble gas prompt releases from underground nuclear explosions, their atmospheric transport to monitoring stations, and to discriminate nuclear explosion generated radioisotopes from those, generated and released by nuclear reactors, or radionuclide generators, one must accurately and numerically simulate the explosion phase, the interaction of the explosive energy released with the fractured hosting rock, and cavity formation, the radionuclide generation and their circulation within the cavity, and the eventual prompt release or seepage of the radionuclide gases to the atmosphere. LLNL has, therefore, developed an HPC-based numerical framework to simulate, from source-to-atmosphere, the gas releases by coupling a non-linear explosion hydrocode to a geomechanical code that converts explosion-induced damage to rock permeability, key parameter to subsurface and surface coupled gas transport codes. The resulting releases source to the atmosphere is then used as an input to a global atmospheric circulation code to reach the monitoring stations. We numerically illustrate the onset of the different regimes and their combined effect of flow, heat and mass transport of different gas species, the fraction of molten rock and their impact on the noble gas fractionation. We also present a sensitivity analysis of the effect of heat loss and cooling to the adjacent rock formation. We demonstrate several scenarios of prompt releases to the atmosphere using a first-ever fully coupled prompt subsurface-to-atmospheric transport without ad-hoc boundary conditions between different numerical codes. We illustrate, using hypothetical explosion scenarios, the benefits of the proposed approach versus the conventional ones.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Session: Advancements in Forensic Seismology and Explosion Monitoring - I

Type: Oral

Date: 4/17/2025

Presentation Time: 08:45 AM (local time)

Presenting Author: Souheil

Student Presenter: No

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