Abstracts ASN Report 2019

• !ǼȒǕǕǣȇǕ Ȓǔ Ɏǝƺ Ɏɖƫƺɀ ƏȇƳ ǣȇɎƺȸȇƏǼɀ Ȓǔ Ɏǝƺ ɀƺƬȒȇƳƏȸɵ ȵƏȸɎ Ȓǔ Ɏǝƺ ³ɎƺƏȅ JƺȇƺȸƏɎȒȸɀ Over time, the SGs tend to become clogged with corrosion products from the secondary system exchangers. This leads to a build-up of soft or hard sludge at the bottom of the SGs, fouling of the tube walls and clogging of the tube bundle tube support plates. The corrosion products form a layer of magnetite on the surface of the internals. The layer of deposits (fouling) that forms on the tubes reduces the heat exchange capacity. On the tube support plates, the deposits prevent the free circulation of the water-steam mixture (clogging), which creates a risk of damage to the tubes and the internal structures and which can degrade the overall operation of the SG. To prevent or mitigate the clogging effects described above, various solutions can be implemented to limit metal deposits: preventive chemical cleaning or remedial mechanical cleaning (using hydraulic jets), replacement of material (brass by stainless steel or titanium alloy, which are more corrosion-resistant) in certain secondary system exchanger tube bundles, modification of the chemical products used for conditioning of the systems and increase in the pH of the secondary system. Some of these operations require a license for the discharge of some of the products used. Some chemical cleaning processes are still being tested to demonstrate that the chemical products utilised are harmless. In particular, the identification of a corrosion risk on reactors ŊĻļĶĻ ĻĴķ ňŁķĸŅ峣ĸ ņňĶĻ ĶĿĸĴŁļŁĺ ļŁ ӅӃӄӉׇĿĸķ Ňł ŅĸńňĸņŇ the implementation of specific maintenance measures, more specifically non-destructive examination of the areas potentially exposed to this risk. • «ƺȵǼƏƬƺȅƺȇɎ Ȓǔ Ɏǝƺ ³ɎƺƏȅ JƺȇƺȸƏɎȒȸɀ ļŁĶĸ ŇĻĸ ӄӌӌӃņё ĻĴņ ĵĸĸŁ ŅňŁŁļŁĺ Ĵ ŃŅłĺŅĴŀŀĸ Ňł ŅĸŃĿĴĶĸ the SGs with the most severely damaged tube bundles, with priority being given to those made of non-heat-treated Inconel ӉӃӃׇĴĿĿłŌ ҎӉӃӃ ҏё ĴŁķ ŇĻĸŁ ŇĻłņĸ ŀĴķĸ łĹ ĻĸĴŇіŇŅĸĴŇĸķ ŁĶłŁĸĿ ӉӃӃׇĴĿĿłŌ ҎӉӃӃׇ ҏє Ļĸ ĶĴŀŃĴļĺŁ Ňł ŅĸŃĿĴĶĸ ņ ŊļŇĻ Ĵ Ňňĵĸ ĵňŁķĿĸ ŀĴķĸ łĹ ӉӃӃׇ ҂ņłŀĸ ӅӉׇŅĸĴĶŇłŅņ҂ ŊĴņ ĶłŀŃĿĸŇĸķ ļŁ ӅӃӄӈׇŊļŇĻ ŇĻĴŇ łĹ ŇĻĸ ĿĴŌĴļņׇ ŅĸĴĶŇłŅ ӆє Ň ļņ ĶłŁŇļŁňļŁĺ ŊļŇĻ ŅĸŃĿĴĶĸŀĸŁŇ łĹ ņ ļŁ ŊĻļĶĻ ŇĻĸ Ňňĵĸ ĵňŁķĿĸ ļņ ŀĴķĸ łĹ ӉӃӃׇ ҂ŇĻĴŇ ļņ ӅӉׇŅĸĴĶŇłŅņє • xȒȇǣɎȒȸǣȇǕ ȅƺɎǝȒƳɀ ƏȵȵǼǣƺƳ ɎȒ ȅƏǣȇ ȵȸǣȅƏȸɵ ƏȇƳ ɀƺƬȒȇƳƏȸɵ ɀɵɀɎƺȅ ¨ȸƺɀɀɖȸƺ 0ȷɖǣȵȅƺȇɎ ٢¨0٣ Ļĸ ŅķĸŅ łĹ ӄӃׇ łʼnĸŀĵĸŅ ӄӌӌӌׇņŃĸĶļĹļĸņ ŇĻĴŇ ŇĻĸ ŁłŁіķĸņŇŅňĶŇļʼnĸ testing processes used for in-service monitoring of the Pressure Equipment (PE) of the main primary and secondary systems of nuclear power reactors must be qualified before they are used for the first time. This qualification is granted by a body comprising ĸŋŃĸŅŇņ ĹŅłŀ ĵłŇĻ ļŁņļķĸ ĴŁķ łňŇņļķĸ ŊĻłņĸ ĸŋŃĸŅŇļņĸ ĴŁķ ļŁķĸŃĸŁķĸŁĶĸ ĴŅĸ ʼnĸŅļĹļĸķ ĵŌ ŇĻĸ ŅĸŁĶĻ ĴĶĶŅĸķļŇĴŇļłŁ ĶłŀŀļŇŇĸĸ (Cofrac). Qualification is a means of guaranteeing that the non-destructive testing process actually achieves the anticipated level of performance as described in specifications drawn up beforehand. Owing to the radiological risks associated with radiographic inspection, ultrasound inspections are preferred, provided that they offer equivalent inspection performance. ł ķĴŇĸё ŀłŅĸ ŇĻĴŁ ӌӃׇŁłŁіķĸņŇŅňĶŇļʼnĸ ŇĸņŇ ŃŅłĶĸņņĸņ ĻĴʼnĸ been qualified for the in-service inspection programmes. New development and qualification processes to address new needs are in progress. ļŇĻ ŅĸĺĴŅķ Ňł ŇĻĸ ĿĴŀĴŁʼnļĿĿĸ ё ʼnļŅŇňĴĿĿŌ ĴĿĿ łĹ ŇĻĸ ŇĸņŇ processes for in-service monitoring of the main primary and secondary systems PE were qualified ahead of the Pre-Service Inspection (VCI) of the main primary and secondary systems, ĶłŅŅĸņŃłŁķļŁĺ Ňł ŀłŅĸ ŇĻĴŁ ӆӃׇńňĴĿļĹļĸķ ŃŅłĶĸņņĸņ ņŃĸĶļĹļĶ Ňł ŇĻĸ єׇ א ِ א ِ ג ɀɀƺɀɀȅƺȇɎ Ȓǔ ¨ȸƺɀɀɖȸƺ 0ȷɖǣȵȅƺȇɎ in operation • Áǝƺ ȸƺƏƬɎȒȸ ȵȸƺɀɀɖȸƺ ɮƺɀɀƺǼɀ As part of the preparation for the fourth periodic safety ŅĸʼnļĸŊņ łĹ ŇĻĸ ӌӃӃׇ ĸ ŅĸĴĶŇłŅņё ņĸŁŇ Ĵ ķłņņļĸŅ ļŁ ӅӃӄӊׇņňĵņŇĴŁŇļĴŇļŁĺ ŇĻĸ ļŁіņĸŅʼnļĶĸ ņŇŅĸŁĺŇĻ łĹ ŇĻĸņĸ ŅĸĴĶŇłŅņ ĴĹŇĸŅ ӇӃׇŌĸĴŅņ łĹ łŃĸŅĴŇļłŁє Ļļņ ķłņņļĸŅ ŊĴņ ņňĵŀļŇŇĸķ Ňł the Advisory Committee for Nuclear Pressure Equipment Ҏ ҏ ĹłŅ ļŇņ łŃļŁļłŁ łŁ ӅӃׇ łʼnĸŀĵĸŅ ӅӃӄӋׇĴŁķ ӄӈׇ ĶŇłĵĸŅ ӅӃӄӌє Ļĸ ĸŋĴŀļŁĴŇļłŁ ĶłŁĶĸŅŁĸķ ŇĻĸ ķĸĹĸĶŇņ ĴŁĴĿŌņĸķё ŇĻĸ estimated irradiation ageing of the metal of the vessel, the thermomechanical analyses and the studies assessing the margin with respect to fast fracture of the vessels. The generic ĴŃŃŅłĴĶĻ ĴķłŃŇĸķ ĵŌ ĶłŁņļņŇņ ļŁ ĶłŁņĸŅʼnĴŇļʼnĸĿŌ ĶłŁņļķĸŅļŁĺ the mechanical properties of the vessel experiencing the worst- ĶĴņĸ ļŅŅĴķļĴŇļłŁ ĸŀĵŅļŇŇĿĸŀĸŁŇ ĹłŅ ŇĻĸ ӌӃӃׇ ĸ ŅĸĴĶŇłŅņє The examination carried out via this generic approach is to be continued in 2020, more specifically with a further presentation to the GPESPN. Given the deadlines of the fourth ten-yearly ļŁņŃĸĶŇļłŁ ĹłŅ ŇĻĸ ŅļĶĴņŇļŁ ŅĸĴĶŇłŅ ӄׇĴŁķ ŇĻĴŇ łĹ ŇĻĸ ňĺĸŌׇ ŅĸĴĶŇłŅ Ӆё ĴĿņł ŃŅłʼnļķĸķ Ĵ ņŃĸĶļĹļĶ ķĸŀłŁņŇŅĴŇļłŁ of the strength of the vessels of these two reactors. ASN considers that this specific demonstration is satisfactory and enables these two reactors to continue to operate beyond their fourth ten- yearly inspection. • !ƏɀɎ ƺǼƫȒɯ ƏɀɀƺȅƫǼǣƺɀ The cast elbow assemblies are piping components installed on the main primary system of PWRs. They are present on the hot legs (C elbow assemblies) and cold legs (A, B and D elbow assemblies on the crossover legs and E elbow assemblies at the input to the vessel). Ļĸ ĶĴņŇ ĸĿĵłŊ ĴņņĸŀĵĿļĸņ ļŁņŇĴĿĿĸķ łŁ ŇĻĸ ӌӃӃׇ ĸ ŅĸĴĶŇłŅņ were made of austenitic-ferritic stainless steel. The ferritic phase experiences ageing under the effect of the MPS operating temperature. Certain alloy elements present in the material accentuate this susceptibility to ageing. The result is a deterioration of certain mechanical properties, such as toughness and resistance to ductile tearing. In addition, these elbow assemblies comprise shrinkage clusters or filaments, or solidification cracks, inherent in the static casting Áǝƺ ȵȸǣȇƬǣȵǼƺɀ Ȓǔ Ɏǝƺ ȸƺƏƬɎȒȸ ɮƺɀɀƺǼɀ ǣȇ ٮ ɀƺȸɮǣƬƺ ɀɎȸƺȇǕɎǝ ƳƺȅȒȇɀɎȸƏɎǣȒȇ The regulations in force require in particular that the licensee: ཛྷ identify the operating situations with an impact on the equipment; ཛྷ take measures to understand the effect of ageing on the properties of the materials; ཛྷ take steps to enable it to ensure sufficiently early detection of defects prejudicial to the integrity of the structure; ཛྷ eliminate all cracks detected or, if this is impossible, provide appropriate specific justification for retaining such a type of defect as-is. ASN Report on the state of nuclear safety and radiation protection in France in 2019 285 ׏׎ ٲ THE EDF NUCLEAR POWER PLANTS 10