Non Destructive Testing

Monitoring without causing damage …

Editorial review 2026

Radioactive tracers and sources are used to monitor manufacturing processes in large-scale industry. These controls are called non-destructive because they do not damage the integrity of the materials used.

Tracers were generally chosen with a short radioactive half-life so that they would disappear rapidly from the environment into which they had been introduced. However, the ASNR no longer authorizes the use of this type of marker.

Used in extremely small quantities (A tiny amount is sufficient for detection, because the tracer is highly active due to its short half-life), they do not alter the behavior of a mechanical component or of a substance in a chemical process. Detection is extremely sensitive. Only a few becquerels per liter are sufficient to detect a gamma-emitting tracer.

Industrial processes such as gas flows inside a column or the mixing of components in a hopper can be studied by introducing radioactive products. These tracers are monitored in real time by detectors and make it possible to determine their pathways. This knowledge helps optimize industrial processes.

Car body sheets are produced by a rolling line in which the thickness of the sheet is continuously monitored thanks to a radioactive source and a detector located on either side of it: as soon as the specifications are exceeded, the machine must be adjusted. Quality control is greatly improved and waste is reduced.

Disposable lighters are checked at the end of the production line using a radioactive source. The transmission of radiation through the lighter body provides information about its filling level and automatically removes defective products.

Among non-destructive testing techniques, gamma radiography must also be mentioned. Gamma radiography uses gamma rays, which are more penetrating than X-rays. This technique makes it possible to detect defects in the uniformity of metals, particularly in weld seams.

In agriculture, non-destructive controls are also used, although less frequently. For example, one technique uses an unstable isotope of nitrogen as a tracer to optimize fertilizer quantities as well as the best locations and timing for its application. This allows better use of soil fertility and irrigation while reducing environmental damage.

Thickness or level gauges represent 70% of sealed sources. A sealed source is a radioactive source enclosed within a leak-tight casing. They are used to perform measurements of thickness, density, weight and level. Medium- to high-activity sources installed in fixed positions are commonly used.

Radiation produced by radioelements or accelerators is used in industrial processes only when no less restrictive alternative method exists. The assessment of the benefits provided by these methods takes into account the many necessary safety and regulatory measures.