This is so naive. Yes, there were no nuclear tests with bombs that go "boom" since the early 90's (except for the newest member of the nuclear club, North Kore

This is so naive. Yes, there were no nuclear tests with bombs that go "boom" since the early 90's (except for the newest member of the nuclear club, North Korea). But you can test your nukes so you can have an extremely high degree of confidence that they'll work as designed when the time comes. How can one do that? We'll get to that, but first: if you couldn't do that, the nuclear powers would not have stopped testing. Why would they ever do that? Nobody can coerce a nuclear power to stop doing nuclear tests, just look at North Korea. With that out of the way, here's how you test. The easiest thing is to perform "hydronuclear tests" [1]. In such a test, just like in an actual nuke, you wrap the plutonium pit and detonate a shell of high explosives around it and create an implosion. The "UAT" implosion is slightly less powerful than the "production" one. Either critical mass is not achieved at all (i.e. sustained chain reaction) or if it's achieved, it's only infinitesimally supercritical, so the chain reaction goes on for only a few generations (in an actual explosion there are about 40 generations, with 99% of the energy coming from the last 2 or 3 generations). If the explosion is correctly tuned, you end up melting the plutonium pit (hence the name "hydro") but not transforming it into hot plasma. Hydronuclear tests are virtually undetectable. CIA thinks (with what they claim is a high degree of confidence) that Russia carries out hydronuclear tests. With a hydronuclear test you can determine how well you know your nukes: if you predict that with this amount of detonation, plutonium pit will melt in proportion of 10%, and it happens just as you say, then you know what you are doing. If 80% or 0.8% melts instead, then you have work to do. You tweak all the knobs that you can tweak, check once, twice, three times everything that can be checked, and eventually you get it. Or not. If you don't get it, you restart full scale tests. But considering that no nuclear power have restarted the tests, they probably got it. The US is quite advanced, it does not need to perform hydronuclear tests. It uses high power lasers, and who knows what. But the US is spending $15 BN on the nuclear stockpile stewardship ([2], p182). It's quite unlikely this money just goes down the drain. [1] https://www.globalsecurity.org/wmd/intro/hydronuclear.htm https://www.globalsecurity.org/wmd/intro/hydronuclear.htm [2] https://www.energy.gov/sites/default/files/2022-03/FY%202022%20SSMP%20March%202022.pdf https://www.energy.gov/sites/default/files/2022-03/FY%202022...