If they meant "simulate prototypes of nuclear weapons under development", Bruce, why do you suppose they claimed it was useful in "maintaining the stockpile"? Or is there some overlap there I am not aware of? DO they mean "maintain the stockpile by developing new weapons to add to it as older ones are retired?". Because if that is what they actually mean, it makes sense, but they sure left it ambiguous. WHat they are actually meaning to say, then, is "replace and renew" the stockpile, which would of course push buttons amongst the anti-nuke tree-hugging crowd, I guess.