Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus often decays immediately by emitting particles such as neutrons, protons, or alpha particles. The neutron capture, even after any immediate decay, often results in the formation an unstable activation product. Such radioactive nuclei can exhibit half-lives ranging from fractions of a second to many years.

In places with high neutron fluxes, such as nuclear reactor cores, neutron activation contributes to material erosion, and the materials themselves must be disposed of as low-level radioactive waste. Some materials are more subject to neutron activation than others, so a suitably chosen low-activation material can significantly reduce these problems. One way to demonstrate that nuclear fusion is occurring inside a Farnsworth-Hirsch fusor is to use a Geiger counter to measure the radioactivity induced in a sheet of aluminum foil.

The lasting radiation from a nuclear weapon is in large part due to the neutron activation of the bomb itself and the surrounding material.

Neutron activation also has a practical use. Neutron activation analysis is one of the most sensitive and accurate methods of trace element analysis. 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 have soon disappeared. In this sense, neutron activation is a non-destructive analysis method.

External links

• Handbook on Nuclear Activation Cross-Sections, IAEA, 1974

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