ASN presents its position regarding the Flamanville EPR reactor vessel anomaly
On 28th June 2017, ASN presented its position regarding the Flamanville EPR reactor pressure vessel anomaly. ASN relied on the analysis of the files transmitted by Areva NP and EDF, carried out by its nuclear pressure equipment department and its technical support organisation IRSN, and on the opinion of its Advisory Committee for nuclear pressure equipment.
On the basis of the technical analyses carried out, ASN considers that the mechanical characteristics of the pressure vessel bottom head and closure head are adequate with regard to the loadings to which these parts are subjected, including accident situations.
However, the anomaly in the chemical composition of the steel entails a reduction in the margins with respect to the fast fracture risk. ASN therefore considers that EDF must implement additional periodic inspections to ensure that no flaws appear subsequently. ASN observes that such inspections can be performed on the vessel bottom head and therefore considers that they must be implemented.
However, the technical feasibility of similar inspections on the pressure vessel closure head is not established. ASN therefore considers that the use of the closure head must be limited in time. It notes that it would take about seven years to manufacture a new closure head, which could thus be available by the end of 2024. In these conditions, ASN considers that the current closure head shall not be operated beyond that date.
ASN makes the examination report produced by ASN and IRSN available on its website for consultation by the public, along with the opinion of its Advisory Committee for nuclear pressure equipment.In the coming days,
ASN will submit its draft opinion for public consultation. This consultation will continue until September 2017. ASN will also consult the French High Council for Technological Risk Prevention. It will finalise its opinion following these consultations in October 2017.
The commissioning of the Flamanville EPR reactor pressure vessel will also require authorisation issued more specifically regarding the results of a hydrotest on the entire main primary system.
ASN, with the support of IRSN, is continuing its review of the Flamanville EPR reactor commissioning authorisation application, as and when it receives the files transmitted by EDF.
At the end of 2014, Areva NP revealed an anomaly in the chemical composition of the steel used in the Flamanville EPR reactor pressure vessel, which could impair its ability to withstand crack propagation. Areva NP initiated a test programme to demonstrate that the mechanical strength of the steel is sufficient in all operating situations, including accident situations. The Areva NP conclusions were sent to ASN in December 2016.
To find out more:
Consult the opinion on the consequences of the carbon concentration anomaly on the fitness for service of the Flamanville EPR reactor pressure vessel domes, Advisory committee of experts for nuclear pressure equipment
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