LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT 4.1.2 – Case of worker exposure to natural radioactivity Exposure to radioactive substances of natural origin and to radon of geological origin Worker exposure to naturally occurring radioactive substance results either from the ingestion of dust from materials containing large amounts of radionuclides (phosphates, metal ores), or from the inhalation of radon formed by uranium decay (poorly ventilated warehouses, thermal baths) or from external exposure due to industrial process deposits (scale forming in piping for example). In 2024, the individual monitoring of worker exposure in industrial activities leading to exposure to naturally occurring radioactive substance or to radon of geological origin (exposure to natural radionuclides of the uranium and thorium decay chains) involved about 280 workers monitored for external exposure (including 4 workers exposed to more than 1 mSv) and 214 workers monitored for internal exposure (of whom 66 were exposed to more than 1 mSv). Sixty-five workers are subject to individual dosimetric assessment for exposure to radon from the ground, as part of enhanced individual monitoring by an occupational physician trained in this risk. This number has risen compared with 2023 (30 workers monitored), in line with the gradual application of regulations on radon in the workplace. However, this assessment of radon exposure cannot be considered exhaustive, as many workers may be exposed to an average annual concentration in excess of the reference level (> 300 Bq/m3) in their workplace, even though they do not yet have dosimetric monitoring. In 2024, eight exceedances of the Occupational Exposure Limit Value (OELV) of 20 mSv for effective dose were recorded, with doses ranging from 21 to 37 mSv(3). In 2025, 30 exceedances concerning three caves were recorded in SISERI, five of which were validated by the occupational physician. In addition, a significant event for worker radiation protection was declared concerning the exposure of three workers in an agricultural cavity. This is due in particular to the application of new dose coefficients which, at constant radon exposure, multiply the effective dose by 2 or 4 depending on the physical activity of the workers (Order of 16 November 2023 applicable from 1 January 2024). The workers concerned were working in tourist caves with high radon concentrations. Natural or artificial underground cavities are among the designated radonrisk workplaces in which radon risk assessment is mandatory, due to the high radon concentrations that may be present. As employers take on board the radon regulations, it is expected that the number of workers likely to receive an effective dose of more than 6 mSv over a sliding 12-month period in these environments will increase, and therefore the number of workers subject to dosimetric monitoring. 3. ASNR report: Worker radiation protection: occupational exposure to ionising radiation in France, results for 2024. 3.5 Radon 0.01 Others (discharges from facilities, fallout from atmospheric tests) 0.6 Terrestrial radiation 1.5 Medical TOTAL 6.5 mSv/year 0.6 Water and foodstuffs 0.3 Cosmic radiation Source: IRSN, 2021. GRAPH 7 Average exposure of the French population Number of persons monitored Collective dose (man.Sv(*)) Individual dose > 20 mSv Reactors and energy production (EDF) 24,079 6.78 0 “Fuel cycle”; decommissioning 13,653 4.57 0 Transport 386 0.05 0 Logistics and maintenance (contractors) 34,688 35.50 0 Effluents, waste 736 0.11 0 Others 16,175 2.75 0 Total civil nuclear 89,717 49.76 0 * Man.Sv: unit of quantity of collective dose. For information, the collective dose is the sum of the individual doses received by a given group of persons. (Source: Radiation protection of workers: occupational exposure to ionising radiation in France, results for 2024 – ASNR) TABLE 7 Monitoring of external exposure of workers in the civil nuclear field (year 2024) Number of persons monitored Collective dose (man.Sv(*)) Individual dose > 20 mSv Medical 101,559 5.80 1(1) Dental 4,867 0.16 0 Veterinary 8,009 0.12 0 Industry 9,137 2.89 1(2) Research and education 6,432 0.18 0 Natural(**) 24,112 27.11 8(3) Total small-scale nuclear activities 154,116 36.26 10 (1) This case was included by default, as the occupational physician gave no feedback on the conclusions of the investigation. (2) This case was included by default as the occupational physician gave no feedback. (3) Five of the eight cases were included by default as the occupational physician gave no feedback. * Man.Sv: unit of quantity of collective dose. ** “Natural” covers civil flight crew and workers exposed to natural radionuclides of the uranium and thorium decay chains. (Source: Radiation protection of workers: occupational exposure to ionising radiation in France, results for 2024 – ASNR) TABLE 8 Monitoring of external exposure of workers in small-scale nuclear activities (year 2024) Number of employees monitored Collective dose (man.Sv(*)) Individual dose > 20 mSv 2017 384,198 100.58 1.03 2018 390,363 104.14 1.12 2019 395,040 112.31 1.20 2020 387,452 72.43 0.78 2021 392,180 82.71 0.85 2022 386,080 88.43 0.90 2023 360,743 84.23 0.95 2024 248,814(*) 87.36 0.35(**) * The total workforce monitored in 2024 only concerns workers classified as category A, B and/or those in the “Other exposures” category, which includes exposure to radon, cosmic radiation and workers in radiological emergency situations. ** As all classified workers are considered to be exposed within the meaning of the regulations, the average dose is now calculated on the basis of the total number of workers monitored, and not on the number of employees who received a dose in excess of the dosimeter recording threshold, set at 0.1 mSv, as was the case in previous reports. (Source: Radiation protection of workers: occupational exposure to ionising radiation in France, results for 2024 – ASNR) TABLE 9 Development of number of employees monitored and average collective and individual doses in the exposed population from 2017 to 2024(*) in all areas combined Source: IRSN, 2021. 156 ASNR Report on the state of nuclear safety and radiation protection in France in 2025
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