During the in-service inspection in 1999 in Tricastin 1 Nuclear Plant, underclad cracks had been discovered in the core shell. Following the specific demonstration of the acceptability of these defects, other components also sensitive to this kind of defects have been re-examined. The life assessment includes a review of the mechanism of formation of theses underclad flaws by cold cracking and the selection of the components sensitive to theses cracks. This includes various shells of the reactor pressure vessel, the steam generator and the pressurizer. A second part consists in mechanical analysis of theses selected components, with an underclad flaw of very large size. This is compared with the maximum size of a realistic crack, which depends of the size of the heat affected zone during the cladding process. The third part has to do with the In Service Inspection. This concerns only the reactor pressure nozzles — both inlet and outlet — which are examined during the inspection of the core shell of the reactor vessel.

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