Caesium-134

Caesium-134

Caesium-134 has a half-life of 2.0650 years. It is produced both directly (at a very small yield because Xe is stable) as a fission product and via neutron capture from nonradioactive Cs (neutron capture cross section 29 barns), which is a common fission product. It is not produced by nuclear weapons because Cs is created by beta decay of original fission products long after the nuclear explosion is over.