radiation protection issues concerning these facilities must be considered as of the design stage. Application of the standards, in particular standard NF M 62‑105 “Industrial accelerators: installations”, ISO 10648‑2 “Containment enclosures” and ISO 17873 “Ventilation systems for nuclear installations”, guarantees safe use of the equipment and a significant reduction in risks. Facilities that have a cyclotron used to produce radionuclides and products containing radionuclides are subject to gaseous effluent discharge limits specified in their license. The discharge levels depend on the frequency and types of production involved. Systems for filtering and trapping gaseous effluents are installed in the production enclosures and in the facilities’ ventilation systems in order to minimise the activity discharged at the stack outlet. An increasing number of licensees are also installing – as close as possible to the shielded enclosures – systems for collecting and storing the gases to let them decay before being discharged, bringing a substantial reduction in the activities discharged into the environment. These radioactive gas compression systems are then emptied after a decay time that is appropriate for the type of radionuclide. Consequently, the discharged activity levels and the short half‑life of the radionuclides discharged in gaseous effluents mean there is no significant impact on the public or the environment. The work that began in 2016 with IRSN support, on the gaseous discharges from the cyclotrons resulted in 2018 in a doctrine, of which the key principles will be used to draft a regulatory text. 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 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 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. 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. CYCLOTRONS 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 ASN Report on the state of nuclear safety and radiation protection in France in 2023 265 • 08 • Sources of ionising radiation and their industrial, veterinary and research applications 08 05 15 11 04 14 06 07 13 AP 03 10 02 09 12 01
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