ASN Report 2018

The principles underlying the accounting rules are as follows: ∙ ∙ radionuclides for which the measured activity exceeds the decision threshold for the measurement technique are all counted; ∙ ∙ the radionuclides of the “reference spectrum” for which the measured activity is below the decision threshold (see box below) are considered to be at the decision threshold level. For discharges of chemical substances with an emission limit value set by an ASN requirement, when the concentration values measured are below the quantification limit, the licensee is required by convention to declare a value equal to half the quantification limit concerned. • Monitoring discharges in the medical sector Pursuant to ASN resolution 2008-DC-0095 of 29 January 2008, radioactivity measurements are taken on the effluents coming from the places that produce them. In hospitals that have a nuclear medicine department, these measurements chiefly concern iodine-131 and technetium-99m. In view of the difficulties encountered in putting in place the permits to discharge radionuclides into the public sewage networks, as provided for by the Public Health Code, ASN has created a working group involving administrations, “producers” (nuclear physicians, researchers) and sanitation professionals. The report from this working group formulating recommendations to improve the efficiency of the regulations was presented in October 2016 to the Advisory Committee for Radiation Protection (GPRADE), for industrial and research applications of ionising radiation and the environment. ASN consulted the stakeholders in 2017 on this subject. The final report plus recommendations will be published in 2019. In the small-scale industrial nuclear sector, few plants discharge effluents apart from cyclotrons (see chapter 8). The discharge permits stipulate requirements for the discharges 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 16 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. 1333-11 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. 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). ASN in-depth inspection at the Gravelines NPP – May 2018. 146  ASN report on the state of nuclear safety and radiation protection in France in 2018 03 – REGULATION OF NUCLEAR ACTIVITIES AND EXPOSURE TO IONISING RADIATION