Tracers are substances with atomic or nuclear, physical, chemical or biological properties that can help identify, observe or follow the behaviour of various physical, chemical or biological processes. Radioactive tracers are widely used to diagnose industrial reactors, for instance by measuring the flow rate of liquids, gases and solids.
A radioactive tracer is a chemical compound in which one or more atoms have been replaced by a radioisotope. Monitoring its radioactive decay, a radiotracer can be used to explore the mechanism of chemical reactions . They are also used for flow visualisation through different technologies, such as Single Photon Emission Computed Tomography (SPECT), Positon Emission Tomography (PET) and Computed Radioactive Particle Tracking (CARPT).