holding sites. Moreover, the inspected suppliers did not all specify the source recovery conditions as is required on delivery of the sources, a situation which is worse than in 2023. There is a very slight increase in the number of ESRs reported compared with 2023, but for the second year running no significant event rated level 1 or higher on the INES scale was recorded. The ESRs notified in 2024 mainly concerned poor management of dosimeters (dosimeter left in luggage during X-ray security checks in an airport zone) resulting in incorrect dose recordings, and the discovery of radioactive substances (tritium luminous paint, loss of integrity of a cobalt-57 source and the discovery of a contaminated source holder) in places not listed in the site’s license. Four other incidents led to abnormal exposures of workers, but without causing any of the regulatory dose limit values to be exceeded. These incidents resulted mainly from failure to comply with the maintenance protocols. None of the supplier ESRs reported in 2024 had significant consequences on the environment or the workers. Cyclotrons Acyclotron 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 containing a liquid, gaseous or solid product which, once irradiated, will produce the desired radionuclide. 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 radiopharmaceuticals manufactured from fluorine-18 have also been developed in recent years, such as 18F-Choline, 18F-Na, 18F-DOPA, as well as 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. Some facilities are also starting to produce copper-64 or zirconium-89, which are still used today in research and clinical tests. 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 274 ASN Report on the state of nuclear safety and radiation protection in France in 2024 Sources of ionising radiation and their industrial, veterinary and research applications
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