4.3 The other suppliers of sources Evaluation of radiation protection Suppliers of radioactive sources, cyclotrons excluded, propose technical solutions for the industrial, medical and research sectors. Suppliers may be manufacturers of “bare” sources or of devices containing sealed radioactive sources, manufacturers of unsealed sources, or distributors who import sources from other countries. Whatever the case, ASN examines the license application files for the sources these suppliers wish to distribute in France. In 2022, excluding cyclotrons, 28 inspections were carried at manufacturers/distributors of sealed and unsealed sources, companies removing surge suppressors, and those manufacturing, installing or maintaining X‑ray generators or particle accelerators (although they are not yet subject to a distribution licence, the utilisation of these devices is regulated, thereby including the commissioning and maintenance operations carried out by the companies that sell them). As a complement to what was done until now, five of the 28 inspections focused on priority themes other than the supply of radioactive sources (protection of sources against malicious acts, maintenance of electrical devices emitting ionising radiation, removal of surge suppressors). Lastly, one of these inspections concerned a foreign company distributing ionising radiation sources in France. CYCLOTRONS A cyclotron is a device 1.5 to 4 metres in diameter, belonging to the circular particle accelerator family. The accelerated particles are mainly protons, with energy levels of up to 70 MeV. A cyclotron consists of two circular electromagnets producing a magnetic field and between which there is an electrical field, allowing the rotation and acceleration of the particles at each revolution. The accelerated particles strike a target which is activated and produces radionuclides. Low and medium energy cyclotrons are primarily used in research and in the pharmaceutical industry to produce positron emitting isotopes, such as fluorine-18 or carbon-11. The radionuclides are then combined with molecules of varying complexity to form radiopharmaceuticals used in medical imaging. The best known of them is 18F-FDG (fluorodeoxyglucose marked by fluorine-18), which is an industrially manufactured injectable drug, commonly used for early diagnosis of certain cancers. Other radiopharmaceutical drugs manufactured from fluorine-18 have also been developed in recent years, such as 18F-Choline, 18F-Na, 18F-DOPA, along with other radiopharmaceuticals for exploring the brain. To a lesser extent, the other positron emitters that can be manufactured with a cyclotron of an equivalent energy range to that necessary for the production of fluorine-18 and carbon-11 are oxygen-15 and nitrogen-13. Their utilisation is however still limited due to their very short radioactive half-life. The approximate levels of activities involved for the fluorine-18 usually found in pharmaceutical facilities vary from 30 to 500 GBq per production batch. The positron emitting radionuclides produced for research purposes involve activities that are usually limited to a few tens of gigabecquerels. SIMPLIFIED DIAGRAM OF THE OPERATION OF A CYCLOTRON Semi-cylindrical D-shaped hollow electrodes Magnetic field generated by two electromagnets Progressively accelerated particles Electric field AC voltage generator Beam extraction channel Isotopes transferred and then used in shielded cells Target in which the isotopes are generated Source of electrically charged particles Electromagnet Semi-cylindrical hollow electrode 262 ASN Report on the state of nuclear safety and radiation protection in France in 2022 • 08 • Sources of ionising radiation and their industrial, veterinary and research applications 08
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