This is completely wrong. Lost nuclear bombs are not going to be functional in the slightest after decades, as they require very precisely timed detonation of explosive charges to actually trigger the main fission reaction. They’re not like chemical bombs, which will explode with enough heat or pressure. And after decades the circuitry to control the explosive charges will be long dead.
So wait, you’re telling me that Mr. Burke can’t really blow up that bomb in the middle of Megaton?