Neutron radiography techniques and applications

In the 1960's, neutron radiography became recognized as a potentially important nondestructive testing tool for industrial applications. The author discusses how neutron radiography is used today for a variety of nondestructive testing applications. In general, neutron radiography and x-radiography tend to complement one another when applied to the same object. Because materials exhibit different attenuation characteristics for neutrons than they do for x-rays, the resulting radiographs emphasize different features for the object. Neutron attenuation is governed by the nuclear scattering and absorption cross-sections of the material, which may vary even between isotopes of a given element, rather than density or any other physical or chemical property of the material. For example, lead, which is very difficult to penetrate with x-rays, is easily penetrated by a neutron beam. Hydrogenous materials such as o-rings, corrosion products, and explosive compounds have high scattering cross-sections and excellent energy moderation characteristics for neutrons and can be imaged easily using neutron radiography even when surrounded with a denser material such as metal