In the wake of numerous experimental tests carried out in air and also in a PWR environment, both abroad and in France, an update of the current fatigue codification is underway. Proposals are currently being formulated in France [1] [2] and discussions are taking place in the frame of a French working group involving EDF, AREVA and CEA.

In parallel with these worldwide modification efforts, it is necessary to evaluate their impact on the NSSS components. In the USA, many such evaluations have already been implemented for license renewal to operate power plants beyond their initial 40 years of operation. In order to reduce the scope of the calculations to perform, a preliminary screening was carried out on the various areas of the primary loop: this screening is detailed in an EPRI report [3]. The output of this screening process is a list of locations that are most prone to EAF degradation process and it is on these zones only that detailed EAF calculations are carried out.

In France, with the approaching fourth decennial inspection of the 900 MWe (VD4 900 MWe) power plants, EDF needs also to map out the impact of these updates to the RCC-M code before initiating detailed calculation efforts.

The EPRI report was not applicable as such to the French plants due to domestic specificities and more particularly, a need for a more detailed Fen estimation. A method was therefore developed by EDF, peer-reviewed by SI with the main innovation being the introduction of correlations enabling the calculation of Fen on the basis of the geometrical dimensions and the information available in the transient document.

This paper presents how these correlations were built and proposes to benchmark them with some existing sample case problems.

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