Analysis of the cracking behavior of Alloy 600 RVH penetrations. Part 2: Derivation of a crack growth model and analysis of crack growth rate field data

The study presented here concerns the analysis of crack propagation behavior in the Alloy 600 RVH penetrations used in the French 900 and 1300 MWe PWR series. The damage mechanism identified is clearly the SCC in primary water environment. Consequently the analysis presented here is based on: (1) the stress analysis carried out on the RVH penetrations, (2) the SCC model developed in Primary Water environment and at the operating temperatures, and (3) the fracture mechanics concepts. The different steps involved in the study are: (1) Evaluation of the stress state for the case of the peripheral configuration of RVH penetrations; the case retained here is that of a conic tube with stress analysis conducted using multi-pass welding. (2) Computation of the influence functions (IF) for a polynomial stress distribution in case of a tube of Ri/t ratio (internal diameter/thickness) corresponding to that of an RVH penetration. (3) Establishment of a propagation law based on study and review of data available in the literature. (4) Conduction of a parametric study of crack propagation using several initial defects. (5) Analysis of crack propagation of defects observed in various reactors and comparison with measured propagation rates. This paper (Part 2) deals with steps (3) through (5) and analyses the crack growth rate field data based on a derived crack growth model