Everybody, still nursing my racing upset and found this:
Disease could affect 2005 Triple Crown field
Mares delivering weak foals; more than 2,200 have died
http://www.msnbc.msn.com/id/5139088/
The radiation source - the nuclear material itself - doesn't need maintenance.
The circuitry needed to detonate a weapon does need maintenance and is pretty fragile.
The tritium used to boost the yield of a fission weapon, and which is involved in the fusion reaction process, does decay fairly quickly but that isn't radioactive.
The radiological source (Uranium or Plutonium) in a lost or abandonned nuke, could be re-used in a dirty bomb. If whoever came into possession of the source had the technical know-how, and certain tools and machinery, it could be recycled into another nuclear weapon, a la "Sum of All Fears".
The tough part about building a nuke is getting hold of the fissionable nuclear material, which is supposedly tightly controlled.