Neutron activation

Neutron activation is a process wherein the materials become radioactive through neutron radiation.

The nuclear reaction on which the activation is based, is generally of capture of thermal neutrons. The resulting next heavier isotope of the element is radioactive in many cases. Other nuclear reactions can - usually caused by fast neutrons - lead to radioactive product nuclei. Through the half-life of these radioactive products and the energy spectrum of their gamma radiation (see gamma spectroscopy), the output elements are qualitatively and quantitatively determined with reasonable accuracy.

In environments with high neutron flux (eg in the central area of nuclear fission and fusion reactors) neutron activation causes which affected need to be replaced during the operation and then disposed of as radioactive waste. Some elements can be activated easily because their nuclei particularly easy to capture neutrons. It is therefore important to avoid these materials for the reactor components, and instead to choose those having a small capture cross section so as to reduce these problems.

Use cases / examples

• The eg caused in an aluminum foil neutron activation can be used for the detection of free neutrons.
• Sustainable radiation after a nuclear bomb explosion is mainly due to the neutron activation of the material in the explosive range.
• Neutron activation is used for the detection of trace elements (see, neutron activation analysis). For this purpose, the taking or even dissolving a sample is unnecessary. The method can therefore be applied to objects that are not damaged (eg, valuable works of art ). The object is in this case indeed radioactive, but this activity can usually be kept very low. In this sense, the neutron activation is a non-destructive method of analysis. The detection limit is specific for each element; with iron it is 10 - 7g in Gold 10 - 13g.