0.4% Prisons 28.2% Certain health care, social and medico-social facilities 60% Schools 11.2% Day-care facilities for children under 6 years of age 0.2% Spas Conventional radiology (55.1 %), computed tomography (12.8%) and dental radiology (29.6 %) account for the largest number of procedures. It is the contribution of computed tomography to the effective collective dose that remains preponderant and more significant in 2017 (75%) than in 2012 (71%), whereas that of dental radiology remains very low (0.3%). In adolescents, conventional radiology and dental procedures are the most numerous (about 1,000 procedures for 1,000 individuals in 2017). Despite their frequency, these procedures in this population represent only 0.5% of the collective dose. Lastly, it will be noted that: ∙ A national headcount estimated at more than 30,000 patients was exposed to a cumulative effective dose of more than 100 mSv in 2017 due to multiple computed tomography examinations. This figure reaches 500,000 if a cumulative period of six years is considered. This highly exposed population seems to be increasing in size regularly and relatively rapidly since 2012. Although most people in this population are old, a quarter of them are aged under 55 years. The question of possible radiation-induced effects is therefore raised for this specific population. It is worth pointing out that these patients are often suffering from serious pathologies and that the computed tomography examinations are important for their care. ∙ Based on a sample of 120,000 children born between 2000 and 2015, IRSN reports that in 2015, 31.3% of the children in the sample were exposed to ionising radiation for diagnostic purposes (up by 2% compared with 2010). The average effective dose is estimated at 0.43 mSv and the median at 0.02 mSv (down for the average but equivalent for the median value). This median value varies greatly according to the age category. For infants of less than one year, it is 0.55 mSv (highest value) and between 6-10 years it is 0.012 mSv. The substantial uncertainties in these studies with regard to the average effective dose values per type of procedure must nevertheless be taken into account, which justifies the need for progress in estimating doses in the next exposure study of the general population. Particular attention must be exercised to check and reduce the doses associated with diagnostic medical imaging, particularly when alternative techniques can be used for a same given indication. Controlling the doses of ionising radiation delivered to persons during a medical examination remains a priority for ASN. In order to enhance the awareness of the building trade professionals (project owners, project managers, architects, companies, distributors, etc.), ASN offers them a guide presenting an overview of the means of protecting buildings against radon. This guide is also intended for private individuals wishing to find out about the work to be carried out. The technical part of this document has been prepared by the Scientific and Technical Centre for Building (CSTB). The guide is divided into two parts, concerning existing buildings and new construction projects respectively: • For existing buildings, the implementation of effective corrective actions usually consists in an adaptation and a judicious combination of three types of generic solutions: airtightness of the substructure and the networks, ventilation of the building and treatment of the substructure by ventilation or placing under negative pressure. A flow chart is provided to help choose the appropriate corrective actions according to the indoor air radon concentration measured in the premises. • For future building constructions, particularly in zones with significant radon potential, it is judicious to use prevention means. It is important to integrate these means at the building design stage to ensure effective results for a marginal cost. The construction project can thus sometimes be improved by avoiding certain designs that foster the entry of radon (for example, avoid underground storeys and intercommunication between basements and occupied volumes). Possible additional preventive actions consist for example in ventilating the crawl space or the basement, or even installing a soil depressurisation system. Whatever the case, the substructures must be meticulously sealed. On completion of the works, whether reduction work in an existing building or the construction of a new building, the effectiveness of the actions taken must be verified by measuring the radon concentration in the premises, using a detector which must remain in place for at least two months, preferably between 15 September and 30 April. PROTECTION OF BUILDINGS AGAINST RADON: A GUIDE FOR EVERYONE de recommandations pour la protection des bâtiments neufs et existants vis-à-vis du RADON GUIDE Réalisé conjointement avec : DIAGRAM Distribution of the initial and ten-yearly measurement by PAB category from 2016-2017 to 2022-2023 5 114 ASN Report on the state of nuclear safety and radiation protection in France in 2023 • 01 • Nuclear activities: ionising radiation and health and environmental risks
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