Instrumentation for individual worker dosimetry

In France, some 230,000 people may be exposed to ionizing radiation. Some of them work in nuclear power generation (fuel fabrication, nuclear power plants, reprocessing, research). Others, more scattered but more numerous, work in the medical field (radiotherapy, fluoroscopy, nuclear medicine), in industry (sterilization, polymerization, radiography of parts and welds, etc.), in the military (nuclear ships, weapons), in university research (research laboratories, gas pedals), and so on.

In accordance with European directives and French regulations, these workers must be monitored to ensure that they are not exposed to radiation doses in excess of certain values corresponding to a risk considered sufficiently low to be acceptable.

This control is carried out by means of individual dosimeters, which are the subject of this article. This dosimetry is compulsory for workers likely to be exposed to more than 30% of the regulatory limit (category A).

These dosimeters must be worn on the chest, where the value they measure is considered representative of the effective dose (average dose for the whole body). In special cases, where the extremities are particularly exposed, workers can wear dosimeter rings or wrist dosimeters.

Over the last ten years, optimization - i.e. the search for the lowest possible level of exposure, taking into account economic and social factors - has gradually become a major objective of radiation protection for workers.

While passive dosimeters only provide information on the dose received a posteriori, direct-reading electronic dosimeters are increasingly used, often connected to centralized daily recording systems, and enable effective action to be taken in the direction of optimization.

In the event of an accident, dosimeters can be used to determine the doses received by the worker and to help with medical diagnosis.

In all cases, the user should bear in mind that a dosimeter is generally not designed to respond perfectly to all types or energies of radiation. He should choose a dosimeter suited to the radiation fields to which the worker is (mostly) exposed.