Not a nuclear war simulation, but what you’re asking about is the mission of NARAC at LLNL: https://narac.llnl.gov https://narac.llnl.gov NARAC monitors and pr

Not a nuclear war simulation, but what you’re asking about is the mission of NARAC at LLNL: https://narac.llnl.gov https://narac.llnl.gov NARAC monitors and predicts the spread of wind/water carried nuclear, biological, chemical, and other hazardous materials in emergencies. You can see videos of recent responses on their website; the highest profile one was probably the Fukushima disaster (if you remember the various evacuation recommendations, NARAC guided the US ones). Here are some more: https://narac.llnl.gov/about/timeline https://narac.llnl.gov/about/timeline, including the Eyjafjallajökull volcano. They run in some of their own (comparatively) smaller clusters for quick turnaround simulations, as well as on LLNL’s bigger HPC systems (https://hpc.llnl.gov/hardware/compute-platforms https://hpc.llnl.gov/hardware/compute-platforms) when there’s a need.