Abstracts ASN Report 2019

In x zàXnn0 0¨« «0 !Á…« ڙ zȒȇ ٮ ƬȒȇǔȒȸȅǣɎɵ Ȓǔ ȅƏǣȇ ɀƺƬȒȇƳƏȸɵ ɀɵɀɎƺȅ ɯƺǼƳɀ A significant number of deviations have been detected in the welds made on the pipes making up the main secondary systems of the Flamanville EPR reactor. These deviations led to the presence of flaws which were only belatedly detected and to mechanical properties below ɎǝȒɀƺ ǣȇǣɎǣƏǼǼɵ ƏȇɎǣƬǣȵƏɎƺƳِ Áǝƺɀƺ ƳƺɮǣƏɎǣȒȇɀ ɀɎƺȅ ژ ȸƺɀɖǼɎƺƳ from insufficient qualification of the processes, a lack of expertise in their implementation and shortcomings in EDF’s monitoring of its contractors. Some of these welds are subject to a “break preclusion” approach, which assumes mechanical properties and a level of manufacturing quality that are particularly high. As early as 2018, ASN considered that preference should be given to repairing all the welds. EDF began to repair the main secondary systems welds, using procedures which depended on the systems concerned and the nature of the deviations. M Əǣȇ ɀɎƺƏȅ Ǽǣȇƺ ɯƺǼƳɀ Ȓȇ Ɏǝƺ ƬȒȇɎƏǣȇȅƺȇɎ ȵƺȇƺɎȸƏɎǣȒȇɀ Eight main steam line welds (VVP system) are located in the annulus between the two containment walls of the reactor building and are hard to access. EDF had hoped to be able to keep these break-preclusion welds as-is, relying on a test programme and increased in-service monitoring. After examining the EDF file and consulting its Advisory Committee for Nuclear Pressure Equipment, ASN considered that the nature and the particularly high number of the deviations which had occurred during design and manufacture represented a major obstacle to keeping these welds as-is. In June 2019, ASN therefore indicated that repair before commissioning of the reactor remained the baseline solution. Three repair solutions were then studied by EDF, for which ASN submitted its preliminary analysis of the risks and sensitive points. In October 2019, EDF’s priority scenario was repair of the pipe from the inside, which requires the development of special intervention means. Qualification of the processes is ongoing, with EDF envisaging the end of the repair works in the second half of 2021. 1 Steam generators 2 Annulus 3 IƺƺƳɯƏɎƺȸ ˢȒɯ ƬȒȇɎȸȒǼ ɀɵɀɎƺȅ 4 Penetrations 5 Double containment 6 Steam letdown systems (VVP) 1 2 1 3 3 4 4 5 5 6 6 18 ASN Report on the state of nuclear safety and radiation protection in France in 2019