Thus, the process of neutron capture, even after any intermediate decay, often results in the formation of an unstable activation product.
All naturally occurring materials, including air, water, and soil, can be induced (activated) by neutron capture into some amount of radioactivity in varying degrees, as a result of the production of neutron-rich radioisotopes.
The Castle Bravo accident, in which the thermonuclear bomb test at Bikini Atoll in 1954 exploded with 2.5 times the expected yield, was caused by the unexpectedly high probability of this reaction.
[5] Carbon-14, most frequently but not solely, generated by the neutron activation of atmospheric nitrogen-14 with a thermal neutron, is (together with its dominant natural production pathway from cosmic ray-air interactions and historical production from atmospheric nuclear testing) also generated in comparatively minute amounts inside many designs of nuclear reactors which contain nitrogen gas impurities in their fuel cladding, coolant water and by neutron activation of the oxygen contained in the water itself.
[6] For physicians and radiation safety officers, activation of sodium in the human body to sodium-24, and phosphorus to phosphorus-32, can give a good immediate estimate of acute accidental neutron exposure.
[7] One way to demonstrate that nuclear fusion has occurred inside a fusor device is to use a Geiger counter to measure the gamma ray radioactivity that is produced from a sheet of aluminium foil.
[8] Aluminium can capture a neutron and generate radioactive sodium-24, which has a half life of 15 hours[9][10] and a beta decay energy of 5.514 MeV.
[11] The activation of a number of test target elements such as sulfur, copper, tantalum, and gold have been used to determine the yield of both pure fission[12][13] and thermonuclear weapons.
It requires no sample preparation or solubilization and can therefore be applied to objects that need to be kept intact such as a valuable piece of art.
Although the activation induces radioactivity in the object, its level is typically low and its lifetime may be short, so that its effects soon disappear.