What is the lifetime of a nuclear bomb?
I was told that because Uranium decays, the bomb becomes a dud
if its fuel is not replishned.
The useful lifetime of nuclear weapons is not known. Uranium is not much
of a problem, as its decay process (half-life = 500 million years) is very
long on a human time scale. Plutonium, with a much shorter half-life
(17,000 years), is more of a problem. The problem isn't exactly that the
fissile fuel gets depleted, as that the process of radioactive decay
damages the material. This changes the density and crystalline form of the
metal, which can affect how it behaves under the conditions used for
ignition. The weapons labs are spending a lot of time, effort, and money
to try to figure out how old the metal can be and still function. They
aren't allowed to find out the obvious way, by testing, because of the test
Richard E. Barrans Jr., Ph. D.
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Update: June 2012