ASN Report 2017

145 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 04  - Regulation of nuclear activities and exposure to ionising radiation and their monitoring, which are subject to particular scrutiny during inspections. 4.1.2 Evaluating the radiological impact of the facilities In accordance with the optimisation principle, the licensee must reduce the radiological impact of its facility to values that are as low as possible under economically acceptable conditions. The licensee is required to assess the dosimetric impact of its activity. As applicable, this obligation is the result of Article L. 1333-8 of the Public Health Code, or the regulations concerning BNI discharges (Article 5.3.2 of ASN resolution 2013-DC-0360 of 16th July 2013 concerning control of detrimental effects and the impact of basic nuclear installations on health and the environment). The result must be compared with the annual dose limit for the public (1 mSv/year) defined in Article R.1333-8 of the Public Health Code. This regulation limit corresponds to the sum of the effective doses received by the public as a result of nuclear activities. In practice, only traces of artificial radioactivity are detectable in the vicinity of the nuclear facilities; most measurements taken during routine surveillance are below the decision threshold or reflect the natural radioactivity. As these measurements cannot be used for dose estimations, models for the transfer of radioactivity to humans must be used, on the basis of measurements of discharges from the installation. These models are specific to each licensee. They are detailed in the installation’s impact assessment. During its assessment, ASN verifies that these models are conservative, in order to ensure that the impact assessments will in no case be underestimated. In addition to the impact assessments produced on the basis of discharges from the facilities, the licensees are required to carry out environmental radioactivity monitoring programmes FUNDAMENTALS With regard to the measurements ཛྷ ཛྷ The Decision Threshold (SD) is the value above which it is possible with a high degree of confidence to conclude that a radionuclide is present in the sample. ཛྷ ཛྷ The Detection Limit (LD) is the value as of which the measurement technique is able to quantify a radionuclide with a reasonable degree of uncertainty (the uncertainty is about 50% at the LD). More simply, LD ≈ 2 x SD. For the measurement results on chemical substances, the Quantification Limit is equivalent to the Detection Limit used to measure radioactivity. Reference spectra For the NPPs, the reference spectra of discharges comprise the following radionuclides: ཛྷ ཛྷ Liquid discharges: tritium, carbon-14, iodine-131, other fission and activation products (manganese-54, cobalt-58, cobalt-60, nickel-63, Ag-110m, tellurium-123m, antimony-124, antimony-125, caesium-134, caesium-137); ཛྷ ཛྷ Gaseous discharges: tritium, carbon-14, iodines (iodine-131, iodine-133), other fission and activation products (cobalt-58, cobalt-60, caesium-134, caesium-137), noble gases: xenon-133 (permanent discharges from ventilation networks, when draining “RS” effluent storage tanks and at decompression of reactor buildings), xenon-135 (permanent discharges from ventilation networks and at decompression of reactor buildings), xenon-131m (when draining “RS” tanks), krypton-85 (when draining “RS” tanks), argon-41 (at decompression of reactor buildings). LICENSEE/SITE REFERENCE GROUP MOST EXPOSED IN 2016 DISTANCE TO SITE IN km ESTIMATION OF RECEIVED DOSES, IN mSv (a) (a) 2011 2012 2013 2014 2015 2016 EDF / Saint-Alban Saint-Pierre-de-Bœuf 2.3 4.10 -4 4.10 -4 4.10 -4 2.10 -4 2.10 -4 3.10 -4 EDF / Saint-Laurent-des-Eaux Saint-Laurent-Nouan 2.3 3.10 -4 2.10 -4 2.10 -4 2.10 -4 1.10 -4 1.10 -4 EDF / Tricastin Bollène 1.3 7.10 -4 7.10 -4 5.10 -4 2.10 -4 2.10 -4 2.10 -4 Ganil / Caen IUT 0.6 <3.10 -3 <3.10 -3 <2.10 -3 <2.10 -3 <2.10 -3 <2.10 -3 ILL / Grenoble Fontaine (gaseous discharges) et Saint-Egrève (liquids) 1 et 1.4 5.10 -5 1.10 -4 2.10 -4 3.10 -4 2.10 -4 2.10 -4 a: until 2008, for installations operated by EDF, only “adult” figures were calculated. From 2010 to 2012, the dose of the most exposed reference group of each site for the two age classes (adult or infant) is mentioned. As of 2013, the dose of the reference group is provided for three age classes (adult, child, infant) for all the BNIs. The dose value indicated is the harshest value in the age classes. b: for the Cadarache, Saclay, Fontenay-aux-Roses and Marcoule sites, the dose estimates entered in the table are the sum of the dose estimates transmitted by CEA. As these estimates comprise at least one term of less than 0.01 microsieverts, the values indicated are preceded by the “less than (<)” sign. c: because the outfall for the liquid discharges is geographically distant from the stack, two impact calculations are performed. One reflects the aggregate of maximum impact of gaseous discharges plus maximum impact of liquid discharges. The other corresponds to an actual reference group. d: information not provided by the licensee e: as the site has no longer had radioactive discharges since 2014, the radiological impact caused by radioactive discharges has been and continues to be nil since 2014.