Natural Science Forum / Physics / Particle Physics / November 2005

Chose from among the ones listed here:

http://www.thenuclearproject.com/common_radionuclides.htm

I didn't see any at 48,000.  How about a quarter life?

" The half-life of plutonium-239 is 24,000"  

You will also need a power source. I don't think Duracells have a shelf life
that long.

Well, first I wanted to write: 'It is too long a detonation delay,
Islam will likely not be here anymore in 48,000.000 years...'
But then I understood you created a black hole bomb, and want the 48,000.000
years time to leave earth.. in the little spaceship.
So, in that case I will not be able to help you either.

http://www.radiochemistry.org/periodictable/frames/isotopes_lbnl/index.htm

A "Nuclide Search" on half-lives from 24000 y to 96000 y (a factor of
two either way from your target value) yields

Nuclide search
T1/2(parent) > 24000 y;   T1/2(parent) < 96000 y;

--------------------------------------------------------------------------------

Nuclide    Z    N    Decay mode    Half life    Ex (keV)   Jp
59Ni 28 31 e+b+   7.6E+4 y 5   0 3/2-
137La 57 80 e   6E4 y 2   0 7/2+
202Pb 82 120 e, a   5.25E4 y 28   0 0+
230Th 90 140 a, 24ne, SF   7.538E+4 y 30   0 0+
231Pa 91 140 a, SF   32760 y 110   0 3/2-
239Pu 94 145 a, SF   24110 y 30   0 1/2+

The closest seems to be 202Pb at 52500 years
HTH

Tom Davidson
Richmond, VA