In article ,
Dave Holford wrote:

I'm not a weapon designer, nor do I play one on tv. (College, and my
partial physics minor, was 30 years ago...so why should I stop now?)

Assuming that there really are plutonium warheads in torpedoes on those
vessels; does anyone here know what the half-life of those isotopes
might be?

The plutonium part of the devices is Pu239 (~93%), Pu240 (~6.5%), and a
trace of Pu241 (~.05%). Their half-lives are, respectively; 24,110 yrs,
6,537 yrs., and 14.4 yrs.

IIRC, some current weapons may use Tritium (hydrogen with two neutrons
in the nucleus, slightly radioactive, sometimes used in things like
night sights for pistols, or wris****ch backlights) as part of a trigger
to boost the efficiency of fission-fusion bombs, it has a half-life of
12.3 years. (More may use LiD as a more convenient source of hydrogen;
neutrons from the fission "fuse" convert some of the Lithium to
deuterium and a bit of tritium, which will enhance the yield of the
overall reaction.)

It is my understanding that nuclear and thermonuclear warheads
have to be refurbished on a regular schedule; and I understood that was
due to the radioactive decay of the isotopes used.