ASN Report 2017
53 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 01 - Nuclear activities: ionising radiation and health and environmental risks 2.2.6 Activities using radioactive substances of natural origin Exposure to ionising radiation of natural origin, when increased due to human activities, justifies monitoring measures if it is likely to create a hazard for the exposed workers and, where applicable, the neighbouring population. Thus, certain activities included in the definition of “nuclear activities” can use materials containing Naturally Occurring Radioactive Materials (NORM, see definition in chapter 3, point 1.2.2) at concentration levels that could significantly increase the exposure of workers to ionising radiation and, to a lesser extent, the exposure of populations living near the places in which these activities are carried out. The natural families of uranium and thorium are the main radionuclides found. Among the industries concerned, we can mention: ཛྷ ཛྷ the production of oil and gas, geothermal energy, titanium dioxide, phosphate fertilizers and cement; ཛྷ ཛྷ the extraction of rare earths and granites; ཛྷ ཛྷ the casting of tin, lead and copper. The radiation protection measures to take in this area target not only the workers (risk of external irradiation and internal contamination, radon) but also the general public, for example in the case of effluent discharges into the environment or the production of residues that could be reused, in construction materials for example. 3. Monitoring of exposure to ionising radiation Given the difficulty in attributing a cancer solely to the ionising radiation risk factor, “risk monitoring” is performed by measuring ambient radioactivity indicators (measurement of dose rates for example), internal contamination or, failing this, by measuring values (activities in radioactive effluent discharges) which can then be used – by modelling and calculation – to estimate the doses received by the exposed populations. The entire population of France is exposed to ionising radiation of natural or anthropogenic origin, but to different extents across the country. The average exposure of the French population is estimated at 4.5 mSv (see Diagram 1) per person per year, but this exposure is subject to wide individual variability, particularly depending on the place of residence and the number of radiological examinations received (source: IRSN 2015); the average annual individual effective dose can thus vary by a factor of up to 5 depending on the département . Diagram 1 represents an estimate of the respective contributions of the various sources of exposure to ionising radiation for the French population. These data are however still too imprecise to allow identification of the most exposed categories or groups of individuals for each exposure source category with the exception of the radon risk. 3.1 Doses received by workers 3.1.1 Exposure of persons working in nuclear facilities The system for monitoring the external exposure of persons liable to be exposed to ionising radiation, particularly those working in BNIs or in small-scale nuclear facilities, has been SOURCES AND ROUTES OF EXPOSURE to ionising radiation External irradiation Internal contamination by inhalation of radioactive substances Skin contamination External irradiation Internal contamination through ingestion of contaminated foodstuffs Skin contamination and involuntary ingestion DIAGRAM 1: Average exposure of the French population to ionising radiation (mSv/year)* Source: IRSN 2015 TOTAL 4.5 mSv/an 0.6 Telluric radiation 0.6 Water and foodstuffs 0.3 Cosmic radiation 0.02 Others (BNI discharges, fallout from atmospheric testing) 1.6 Medical 1.4 Radon * This diagram does not integrate the data published in ICRP 167 of January 2018.