On an October morning in 2023, a chemical explosion detonated in a tunnel under the Nevada desert was the launch of the following set of experiments by the National Nuclear Security Administration, with the goal to enhance detection of low-yield nuclear explosions world wide.
Physics Experiment 1-A (PE1-A) is the primary in a series of non-nuclear experiments that may compare computer simulations with high-resolution seismic, tracer gas, acoustic and electromagnetic data gleaned from underground explosions and atmospheric experiments, said Lawrence Livermore National Laboratory researcher Stephen Myers on the Seismological Society of America (SSA)’s 2024 Annual Meeting.
The 18 October explosion — the equivalent of 16.3 tons of TNT — took place in Aqueduct Mesa “P Tunnel” on the Nevada National Security Site (NNSS). Seismic, acoustic and electromagnetic waves from the shock were recorded by instruments near the explosion and with regional seismic networks, while gas tracers and chemical byproducts released into the resulting cavity and boreholes also were sampled by a dense instrument array. Seismic signals were recorded a minimum of 250 kilometers away from the explosion.
“All of that is to assist further our goal of monitoring nuclear explosions higher and understanding the source physics of how those explosions generate seismic waves,” Myers said.
Physics Experiment 1 (PE1) is the newest research program at NNSS, where atmospheric nuclear tests took place between 1951 and 1962, and underground testing occurred between 1961 and 1992. More recently, programs just like the Source Physics Experiment checked out a variety of non-nuclear chemical explosions in numerous rock environments, collecting data to learn more about explosion physics.
The seven latest experiments planned as a part of PE1 include more underground chemical explosions under different emplacement conditions, in addition to atmospheric experiments that try and track underground and atmospheric transport of gases produced in all these explosions. This system may even use a big electromagnetic coil, about 4 meters wide, to generate pulses of electromagnetic energy contained in the tunnel that could be measured at the bottom surface, to find out how much of the electromagnetic signal from an underground nuclear test can be affected by traveling through the earth.
“There is no one experiment that may generate all of the signals which can be produced by a nuclear shot, so we’re doing this series of seven to attempt to piece together all of those signals,” Myers explained, “in order that we are able to validate our full physics codes that we use to simulate what all of those signals can be like from a nuclear explosion.”
Significant improvements in high-performance computing have allowed researchers like Myers to create increasingly realistic and complicated explosion simulations, but “then the query is, ‘are they correct?’ And the one way we could be confident about that’s to match them to those high-resolution data sets from the experiments,” he said.
The brand new experiments are more heavily instrumented than older NNSS experiments, he noted, which helps to validate the pc code simulations.
Atmospheric simulations, for instance, must account for complex variables akin to temperature changes and air turbulence under different topographic conditions. With the experiments, Myers said, “we’re attempting to get an idea if tracers got here out of the bottom after a nuclear test, exactly what a few of these very local conditions, topography and other points, would affect the transport of those radionuclides and other telltale gases that may very well be released by an underground test.”
Myers said the seismic and acoustic data from PE1 will probably be released to a public seismic database after two years. “We wish this to be a resource for the community as a complete.”
