What's the shelf life of an atomic bomb?

Factual Questions
1

I’m curious…what’s the shelf-life of a nuclear bomb? After all, the plutonium and/or uranium in it is turning to lead from the moment it’s made. Assume that normal maintenance (whatever that entails) is taking place, but that the fissile components are not being replaced.

2

Someone will be along with numbers shortly. But you’ll need to know the minimum mass required to get the reaction going and then from there you can take the decay rate and the initial mass and determine how long it will take the initial mass to decay to the minimal mass.

Assuming of course the metal shell, electronics, fuses and whatnot have a longer life than the radioactive material.

3

Pu[sub]239[/sub] has a half-life of 24,000 years.
U[sub]235[/sub] has a half-life around 700,000,000 years.

In both cases, the other components in the bomb (electronics, chemical explosives) would deteriorate long before the fissionable material.

4

This talk by C. Bruce Tarter, the former director of Lawrence Livermore labs, discusses the ways the stockpile ages in some detail. In practice, the number they worry about is the dozen or so year half life of tritium, whose decay screws up the H-bombs.

5
      • I may be absolutely wrong, but I remember reading somewhere that there was some part that goes bad in like 6 months or so–a rather short time. And somehow I doubt it is cheap to replace… Many higher-end military weapons have parts intended to have short shelf lives as a security precaution, but this was a radioactive part, and it was unavoidable.
        ~
6

If you are talking about a bomb system, the current missiles in the UK are about 10-12 years old. They have an indefinite shelf-life (well at least 25 years) as every part is continously inspected and replaced on a rotating basis. This creates interesting problems, such as the plastic resins you once bought off the shelf for the foam insulation might no longer be available or the integrated circuitry which is now obselete.