The most critical device of a nuke warhead is the trigger device (initiator) which can provide millions degree heat and million pounds pressure within millionth of a second, and its coke bottle size can be fitted in the warhead. These initiators need to be "refreshed" every 10-12 years. The only way to test the new initiator is underground (1000 m) actual explosion of one device in each batch of the new initiators. Super computers can not guarantee the actual success of the new initiators, thus physical test (in the power of < 500 kg TNT) deep under ground are being conducted by the nuke weapon owners. Only that no one can detect unless within 5 km of the 30 cm diameter test hole. The 90+% enriched nuke warhead fuel mass have 25,000 yr half life, thus need not to be refreshed. 🤔🤨🤫😎