Originally Posted by
BFSGrad
Attending a presentation at a U.S. nuclear facility back in the 90s, one of the most vexing problems was how to attract and retain technical expertise when nothing new was being developed (U.S. “Stockpile Stewardship”)
Another problem is that there are certain modern safety features than cannot be retrofitted to existing warheads.
You need to keep the design & production systems "warm". Didný BAE have that problem in Barrow-in-Furness? They'd "forgotten" how to make nuclear subs, due to a dearth of orders, all the knowledge dissipated. The Americans had to come in and teach them.