The phenomenon of stress corrosion (SCC) discovered in 2021 in certain EDF power plants has severely affected the production of nuclear electricity this winter.
The discovery of new cracks, linked this time to “
thermal fatigue
” raised fears of the worst.
EDF and the nuclear safety authority (ASN) were however reassuring this Thursday evening, after having detailed the evolution of the control strategy carried out by EDF in its nuclear power plants.
This change in the control strategy for the CSC phenomenon was proposed to ASN by EDF on 10 March 2023 to ASN.
EDF explains "
accelerate the control of the welds concerned of the RIS and RRA systems, in order to take into account the elements identified on the repaired weld of Penly 1
".
To date and on the basis of the control strategy proposed by EDF, "
the estimate of nuclear production in France for 2023 remains in the 300-330 TWh range
".
Last year, nuclear generation dropped to 279 TWh.
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This change in strategy follows the recent discovery of deep-water faults on Unit 1 of the Penly nuclear power station.
It concerns a weld located on a line hitherto considered as not sensitive to SCC, but having been the subject of specific repairs at the time of manufacture.
Hence the term repaired welds, the control of which will be reinforced.
Thermal fatigue defect
“
320 welds on the RIS and RRA lines were identified as having been repaired when the reactors were built.
The revised strategy will make it possible to have checked, by the end of 2023, more than 90% of the repaired welds identified as a priority by EDF
”, underlines the ASN.
The authority could, however, ask EDF to review the timetable for inspections and, if necessary, repairs: "
ASN, with the support of IRSN, is continuing the technical dialogue with EDF in order to ensure the relevance of the envisaged timetable
.
ASN also considers that the discovery of a thermal fatigue defect among the large defects recently characterised, on a weld for which this mode of degradation was not expected, requires additional analyses.