Good question! Existing nukes degrade due to various factors such as the natural radioactive decay of the uranium and plutonium they’re made of. Supercomputers

Good question! Existing nukes degrade due to various factors such as the natural radioactive decay of the uranium and plutonium they’re made of. Supercomputers are used to simulate this and make predictions about reliability, remaining lifetime, etc… When it comes time to refurbish old bombs, ideally they should have the cores reprocessed into new, modern designs with better safety, reliability, and less fallout when they go boom (better efficiency). All of this requires measurements, simulations, tests, etc… In the past it was done with experiments on complete bombs, now it’s done with experiments on just small subsets that don’t go boom in the desert.