External exposure to gamma rays of terrestrial origin Based on the results of a) ambient gamma dose rate measurements taken in France inside buildings, b) the mapping of the uranium potential of geological formations, c) a correlation between the gamma dose rate of terrestrial origin outside the home and inside the home, and d) assumptions on the time spent by the population inside and outside the home (92 % and 8% respectively), the IRSN estimates that the average annual effective dose due to external exposure to gamma radiation of terrestrial origin in France is about 0.63 mSv per person per year. It varies from 0.30 mSv/year to 2.0 mSv/year depending on the municipality. Exposure linked to the incorporation of radionuclides of natural origin The average internal exposure due to the incorporation of radionuclides of natural origin is estimated at 0.55 mSv/year. The two main components of this exposure are the incorporation through foodstuffs and drinking water of potassium-40 (0.18 mSv) and descendants of the uranium and thorium chains (0.32 mSv). Depending on the individual consumption habits, in particular the consumption of fish, seafood and tobacco, this exposure can vary greatly: from 0.4 mSv/year up to more than 3.1 mSv/year, respectively, for people who do not consume these products and those who consume them in large quantities. Waters intended for human consumption, in particular groundwater and mineral waters, become charged in natural radionuclides due to the nature of the geological strata in which they lie. The concentration of uranium and thorium daughters and of potassium-40 varies according to the resource exploited, given the geological nature of the ground. The average effective dose linked to the decay products of the U‑Th chains in drinking water is estimated by IRSN at 0.01 mSv/year. A high value of 0.30 mSv/ year is retained to illustrate the variability of this exposure. 2.1.3 Radon Some geological areas have a high radon exhalation potential due to the geological characteristics of the ground (granitic bedrock, for example). The concentration measured inside homes also depends on the tightness of the building (foundations), the ventilation of the rooms and the life style of the occupants. National measuring campaigns have enabled the French départements to be classified according to the radon exhalation potential of the ground. In 2011, IRSN published a map of France considering the radon exhalation potential of the ground, based on data from the French Geological and Mining Research Office (BRGM). Based on this, a more fine-grained classification, by municipality, was published through the Interministerial Order of 27 June 2018 (see search engine by municipality and mapping accessible on asn.fr and irsn.fr). Working from the available measurement results and the mapping of the geogenic radon potential of the territory, the average time spent inside the home and assumptions on the type of housing concerned (collective or individual), IRSN has estimated the average radon concentration for each municipality: the average concentration of radon-222 inside housing in metropolitan France, weighted for the population and type of housing, is 60.8 Bq/m3. With the dose factor in effect since 1 January 2024, the average effective dose per inhabitant is estimated at 3.5 mSv/year. This effective dose varies from 0.75 mSv/year to 47 mSv/year depending on the municipality (see box page 102). The new obligation for radon detector analysis laboratories to send IRSN the measurement results and the expected results of action 7 of the 4th French action plan for management of the radon risk (see point 3.2), relative to the defining of organisation methods for collecting the radon measurement data should improve knowledge of radon exposures in France. 2.2 IONISING RADIATION ARISING FROM HUMAN ACTIVITIES The human activities involving a risk of exposure to ionising radiation, called nuclear activities, can be grouped into the following categories: ∙ operation of BNIs; ∙ small-scale nuclear activities; ∙ removal of radioactive waste; ∙ management of contaminated sites; ∙ transport of radioactive substances; ∙ activities enhancing natural ionising radiation. 2.2.1 Basic Nuclear Installations Nuclear activities are highly diverse, covering any activity relating to the preparation or utilisation of radioactive substances or ionising radiation. These activities are subject to the general provisions of the Public Health Code and, depending on their nature and the risks that they involve, to a specific legal system. BNIs are defined in Article L. 593-2 of the Environment Code: 1. Nuclear reactors; 2. Facilities, corresponding to characteristics defined by Decree of the Council of State, for the preparation, enrichment, fabrication, treatment or storage of nuclear fuels, or for the treatment, storage or disposal of radioactive waste; Sources and routes of exposure to ionising radiation External irradiation Skin contamination Internal contamination by inhalation of radioactive substances Internal contamination through ingestion of contaminated foodstuffs Ingestion Inhalation Skin contamination External radiation External radiation 104 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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