Today one sees more and more particle accelerators used for research purposes and functioning on the principle of laser‑plasma interactions: these devices can generate beams of highly energetic particles (up to a few hundreds of MeV in some facilities) and over very short times, down to the femto second (10‑15 second). Particle accelerators have been used for several years now in France to fight fraud and large‑scale international trafficking. This technology, which the operators consider effective, must however be used under certain specific conditions in order to comply with the radiation protection rules applicable to workers and the public, in particular: ∙ a ban on activation of construction products, consumer goods and foodstuffs as specified by Article R. 1333‑2 of the Public Health Code, by ensuring that the maximum energy of the particles emitted by the accelerators used excludes any risk of activation of the materials being verified; ∙ a general ban on the use of ionising radiation on the human body for purposes other than medical; ∙ the setting up of procedures to ensure that the checks conducted on the goods or transport vehicles do not lead to accidental exposure of workers or other individuals. The use of ionising technologies to seek out illegal immigrants in transport vehicles is prohibited in France. During customs inspections of trucks using tomographic techniques, for example, the drivers must be kept away from the vehicle and other checks must be performed prior to irradiation to detect the presence of any illegal immigrants, in order to avoid unjustified exposure of people during the inspection. 3.3.2 Evaluation of the radiation protection situation The use of particle accelerators presents significant radiation exposure risks for the workers; ASN is particularly attentive to these facilities and therefore inspects them regularly. Between 2019 and 2023, 66 facilities equipped with these devices were inspected by ASN, 14 of them in 2023. ASN considers the radiation protection situation in the facilities using these devices to be satisfactory on the whole. In effect, the key requirements for conducting this activity with a satisfactory level of radiation protection (organisation of radiation protection, informing and training, technical verifications, radiological zoning and design of the premises in which these devices are used) are appropriately implemented by the large majority of the licensees concerned. Nevertheless, the inspections have also highlighted areas for improvement on which ASN will remain vigilant: ∙ compliance with the regulations concerning the frequency of technical verifications of radiation devices and associated equipment and the formalised processing of any nonconformities detected during these checks; ∙ the presence of an unlocking device which can be actuated from inside the rooms in which particle accelerators are used; ∙ the correct operation of the audio signal associated with the in‑situ check process to ensure nobody is in the room before the emission of ionising radiation can be enabled; ∙ the availability of radiation monitoring devices in sufficient quantities for the operators who access these rooms and keeping these devices in good working order; ∙ the control of the technical means (password, dedicated key, etc.) allowing the security systems to be bypassed for highly specific maintenance and servicing procedures. These means must be kept under constant surveillance to prevent their use other than for these special procedures. Lastly, with regard to experience feedback, no Significant Radiation Protection Event (ESR) was reported to ASN in 2023, apart from the recurrent events associated with the use of particle accelerators in shipment security checks. When conducting these checks, the customs services take precautions (such as broadcasting information messages in several languages) to avoid the unjustified irradiation of people who could be hiding in these vehicles (see point 3.3.1). However, despite these precautions, the customs services regularly notify ASN of events relating to the exposure of people hidden in checked vehicles. Although this exposure is unjustified, it nevertheless remains extremely low with effective doses of just a few microsieverts per person. 3.4 RESEARCH ACTIVITIES INVOLVING UNSEALED RADIOACTIVE SOURCES 3.4.1 The devices used In the research sector, as at 31 December 2023, ASN counted 392 licenses and 153 registrations issued under the Public Health Code, of which nearly 90% are issued to public or mixed (public/ private) entities. The number of licenses is constantly decreasing, essentially due to the replacement of ionising radiation sources by alternative technologies that do not use ionising properties, but also to the changes in the system introduced in the last few years. Since 2019, certain nuclear activities have switched from the licensing system to the notification system (see point 2.4.2) and, since July 2021, other activities are now subject to the registration system (see point 2.4.2). This new system addresses in particular the possession/use of unsealed source which until then were governed solely by the licensing system. Belonging to the same family of circular particle accelerators as the cyclotrons (see point 4.2), the synchrotron, which is much larger, can attain energy levels of several gigaelectronvolts by using successive accelerators. Owing to the low mass of the particles (generally electrons) the acceleration created by the curvature of their trajectory in a storage ring, produces an electromagnetic wave when the speeds achieved become relativistic: this is synchrotron radiation. This radiation is collected at various locations called beam lines and is used to conduct scientific experiments. SYNCHROTRONS The use of ionising radiation in research activities extends to various fields such as medical research, molecular biology, the agri‑food industry, materials characterisation, etc. It primarily involves the use of unsealed sources (iodine‑125, phosphorous‑32, phosphorous‑33, sulphur‑35, tritium‑3, carbon‑14, etc.). Sealed sources (barium‑133, nickel‑63, caesium‑137, cobalt‑60, etc.) are also used in gas chromatographs or scintillation counters or, with higher‑activity sources, in irradiators. X‑ray generators rays are used for X‑ray fluorescence or X‑ray diffraction spectrum analyses. The use of scanners for small animals (cancer research) in research laboratories and faculties of medicine should also be noted. Particle accelerators are used in research into matter or for the manufacture of radionuclides. RESEARCH ACTIVITIES 262 ASN Report on the state of nuclear safety and radiation protection in France in 2023 • 08 • Sources of ionising radiation and their industrial, veterinary and research applications
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