Abstracts ASN Report 2019

ŇĻĸŁ ļŁļŇļĴŇĸķ ŀĴĽłŅ ŊłŅľ ĶłŁņļņŇļŁĺ ļŁ ĿłĶĴĿĿŌ ĴŃŃĿŌļŁĺ a resin sealing coating to the interior and exterior surfaces of the inner wall of the containments of the most severely affected ӄёӆӃӃ ĸ ŅĸĴĶŇłŅņё Ĵņ ŊĸĿĿ Ĵņ Ňł ŇĻĸ ӄёӇӈӃ ĸ ŅĸĴĶŇłŅņє Ļļņ work has already been carried out on seven reactors and will continue until 2022. The tests performed since this work have all complied with the leak rate criteria. ASN remains vigilant with regard to changes in the leaktightness of these containments and to maintaining the long-term effectiveness of the coatings. ňŅļŁĺ ŇĻĸ ӅӃӄӆׇĸŋĴŀļŁĴŇļłŁ łŁ ŇĻĸ ĸĹĹĸĶŇļʼnĸŁĸņņ łĹ ŇĻĸ double-wall reactor containment function, ASN noted that the characteristics of some containments were liable to affect them through the internal swelling of the concrete prejudicial in the long-term to the performance of the confinement function of ŇĻĸņĸ ĶłŁŇĴļŁŀĸŁŇņє ļŁĶĸ ŇĻļņ ĸŋĴŀļŁĴŇļłŁё ĻĴņ ļŁļŇļĴŇĸķ measures to characterise and monitor the phenomena which could affect the concrete of the containments. The analyses carried łňŇ ĵŌ ŁłŇĴĵĿŌ ņĻłŊĸķ ŇĻĴŇ ŇĻĸ ľļŁĸŇļĶņ łĹ ŇĻĸ ķĸʼnĸĿłŃŀĸŁŇ of these phenomena are very slow and that the containments concerned suffer from no structural damage. Also on this point, ASN remains vigilant with regard to the medium to long-term ķĸʼnĸĿłŃŀĸŁŇ łĹ ŇĻĸ ŃĻĸŁłŀĸŁĴ ļŁʼnłĿʼnĸķє Ł ӅӃӄӌё ĶĴŅŅļĸķ out an inspection to ensure the monitoring and characterisation łĹ ŇĻĸņĸ ŃĻĸŁłŀĸŁĴ ĵŌ є łķĸĿĿļŁĺ łĹ ŇĻĸ ĶłŁŇĴļŁŀĸŁŇņ łĹ ŇĻĸ ӄёӆӃӃׇ ĸ ĴŁķ ӄёӇӈӃׇ ĸ reactors in a severe accident situation show particular behaviour, which leads to a risk of cracking in part of the thickness of the dome, in certain accident scenarios. These observations are mainly linked to the differential thermomechanical behaviour of the concrete of the dome and the metal beams. The cracking ŇĻňņ łĵņĸŅʼnĸķ ŇĴľĸņ ŃĿĴĶĸ ŊĸĿĿ ĵĸĹłŅĸ ӅӇׇĻłňŅņё ĶłŅŅĸņŃłŁķļŁĺ Ňł ŇĻĸ ŀļŁļŀňŀ Ňļŀĸ ĶĴĿĶňĿĴŇĸķ ĵŌ ĹłŅ ŅĸńňĸņŇļŁĺ łŃĸŁļŁĺ of the filtration system before discharge from the containment. This cracking is liable to lead to an appreciable increase in leaks through the dome. ASN notes that the results obtained following this modelling depend to a large extent on the hypotheses adopted (containment brittleness curve, representativeness łĹ ŇĻĸ ĶłŁŇĴļŁŀĸŁŇ ŀłķĸĿё ĸŇĶєҏє Ĵņľĸķ Ňł ņŇňķŌ ŇĻļņ phenomenon, to assess the sensitivity of the results to the various parameters of the model and to present any modifications that would be needed to mitigate this risk. א ِ ג «ǣɀǸ ȵȸƺɮƺȇɎǣȒȇ ƏȇƳ ȅƏȇƏǕƺȅƺȇɎ א ِ ג ِ׏ xȒȇǣɎȒȸǣȇǕ Ɏǝƺ ƳȸƏǔɎǣȇǕ ƏȇƳ ƏȵȵǼǣƬƏɎǣȒȇ Ȓǔ Ɏǝƺ JƺȇƺȸƏǼ…ȵƺȸƏɎǣȇǕ «ɖǼƺɀ The RGE cover the operation of nuclear power generating reactors. These are drafted by the licensee and are the operational implementation of the hypotheses and conclusions of the safety assessments constituting the nuclear safety case. They set the limits and conditions for operation of the installation. • zȒȸȅƏǼ ƏȇƳ ƳƺǕȸƏƳƺƳ ȅȒƳƺ ȒȵƺȸƏɎǣȒȇ Operating Technical Specifications The Operating Technical Specifications (STE), which constitute Chapter III of the RGE, define the normal operating conditions ĵĴņĸķ łŁ ŇĻĸ ĹĴĶļĿļŇŌѡņ ķĸņļĺŁ ĴŁķ ņļōļŁĺ ĻŌŃłŇĻĸņĸņ ĴŁķ ŅĸńňļŅĸ the systems needed for maintaining the safety functions, in particular the integrity of the radioactive substance containment barriers and the monitoring of these functions in the event of an incident or accident. They also stipulate the action to be taken in the event of temporary failure of a required system or if a limit is exceeded, situations which constitute “degraded mode” operation. The STEs evolve to integrate the lessons learned from their application and the modifications made to the reactors. The licensee can also modify them temporarily if need be, for example to carry out an operation in conditions that differ from those initially considered in the nuclear safety case. It must then demonstrate the relevance of this temporary modification and define adequate compensatory measures to control the associated risks. Depending on their significance, STE modifications that could affect safety require either submittal of an authorisation application to ASN or notification to ASN before they are implemented. During NPP inspections, ASN verifies that the licensee complies with the STE and, as necessary, the compensatory measures associated with any temporary modifications. It also checks the consistency between the modifications made to the facilities and the normal operating documents, such as operational control instructions and alarm sheets, and the training of the persons responsible for applying them. Periodic tests The Elements Important for Protection (EIP) of persons and the environment undergo qualification to guarantee their ability to perform their assigned functions in the situations where they are needed. The periodic tests of these equipment items help check their continued qualification and regularly verify that they will be available when required. The periodic test rules for equipment important for safety are incorporated into the general operating rules of the reactors. They set the nature of the technical checks to be performed, their frequency and the criteria for determining the satisfactory nature of these checks. ASN ensures that the periodic tests on the elements important for safety are pertinent and are continuously improved. It carries out this verification when examining the application for authorisation to start-up the reactor and then the applications for authorisation to modify the RGE. During inspections, it also verifies that these periodic tests are carried out in accordance with the test programmes stipulated in the RGE. Core physics tests The core physics tests contribute to the first two levels of defence in depth. Their purpose is, on the one hand to confirm that the core in operation is compliant with the design baseline requirements and the safety case and, on the other, to calibrate the automatic control and protection systems. These tests, prescribed in the RGE, are performed periodically. The physics tests at restart are comparable to requalification tests following reloading of the core. The physics tests during the cycle and for the cycle extension guarantee the availability and representativeness of the instrumentation as well as the performance of the core in operation. The modifications to the RGE concerning core physics tests are made using a process similar to that for STE modifications and generally require ASN authorisation. During the on-site inspections, ASN checks the conformity of the tests performed (compliance with procedures and criteria Ňł ĵĸ ʼnĸŅļĹļĸķҏ ĴŁķ ѡņ łŅĺĴŁļņĴŇļłŁ ķňŅļŁĺ ŇĻĸņĸ ŃĴŅŇļĶňĿĴŅ operating phases. • …ȵƺȸƏɎǣȇǕ ȸɖǼƺɀ ǣȇ Ɏǝƺ ƺɮƺȇɎ Ȓǔ Əȇ ǣȇƬǣƳƺȇɎ Ȓȸ ƏƬƬǣƳƺȇɎ Operation in the event of an incident or accident The strategies and reactor operating rules for an incident or accident situation are defined in the RGE. These evolve notably to take account of experience feedback from incidents and accidents, to correct the anomalies detected during their application or to take account of modifications made to the facilities, in particular those resulting from the periodic safety reviews. Most of these modifications require ASN authorisation. ASN Report on the state of nuclear safety and radiation protection in France in 2019 287 ׏׎ ٲ THE EDF NUCLEAR POWER PLANTS 10