Sources in Industry

A wide variety of applications

Most of the radionuclides contained in radioactive sources are extracted from small reactors dedicated to the needs of research, medicine and industry. Some radionuclides are fission products or actinides (americium-241). Others are obtained by neutron irradiation of materials (cesium-137, cobalt-60). They are then extracted using radiochemistry techniques. When short-lived tracers are needed, particularly for medicine and research, cyclotrons or accelerators such as the GANIL accelerator in Caen are also used.

The activities of the sources most commonly used in industry range from a few thousand (kBq) to billions of becquerels (GBq).

The use of radionuclides for “non-destructive testing”, that is to say for “characterizing materials without damaging their integrity”, is the most common. Applications include:

– Weld inspection by gamma radiography, a true radiography of metal (iridium-192 or cobalt-60 sources)

– Liquid level measurement. The attenuation of the detected signal makes it possible to determine the filling level of the container and to automatically trigger certain operations (stop/continuation of filling, alarm, etc.). The radionuclides used depend on the characteristics of the container and its contents: americium-241 (activity 1.7 GBq), cesium-137-barium-137m (activity 37 MBq);

– Thickness measurement of materials such as paper, fabric, plastic, sheets or metal plates according to a similar principle and using gauges based on krypton-85, cesium-137, americium-241, cobalt-60 or promethium-147;

– Density measurement and weighing, also according to a similar principle. The sources generally used are americium-241 (activity 2 GBq), cesium-137-barium-137m (activity 100 MBq) or cobalt-60 (30 GBq);

– Soil density and moisture measurement devices, or gamma densitometry, used particularly in agriculture and public works, operate with a dual americium-beryllium and cesium-137 source;

– Detection and quantification of molecules by analysis in gas chromatographs, using nickel-63 or tritium sources for products such as pesticides, explosives or drugs.

Cadmium-109 and cobalt-57 are used for the detection of toxic products such as lead in paints.

When the activity of a radiation source becomes very powerful, it is referred to as industrial irradiation. In France there are several industrial irradiators using sealed sources (cobalt-60 or cesium-137) with very high activity (800 TBq). Given the activity involved, these facilities are classified as Basic Nuclear Installations (BNI). Highly active radioactive sources tend to be replaced by electrical generators of ionizing radiation.