Critical examination of valve design according to sub-section B 3500 of the french design and construction rules for mechanical components of PWR nuclear Islands (RCCM January 1985 edition)

Abstract

The aim of this paper is to make easier the understanding of sub-section B 3500 of the RCCM Code concerning the design rules of class 1 valve bodies. The RCCM Code is applicable to mechanical components of PWR nuclear islands and is published by the French Society for Design and Construction rules for Nuclear Island Components (AFCEN). The RCCM design rules for class 1 valves (sub-section B 3500) are reviewed and the agreement between the principle of sub-section B 3200 and the rules of sub-section B 3600 concerning piping design is examined. The equations used in the code are examined with respect to their origin, their justification and their conservatism. The applicability of the body shape rules and their relationship with fatigue strength reduction factors are also discussed. A parametric analysis is presented to show the influence of transition radii under different loads, including thermal shock. The study specifically examines the stress concentration factors obtained from a 3D finite element analysis of a tee shaped valve under mechanical loading (pressure, bending, etc.). The objective of this study is to understand and improve the existing rules so that ultimately a program can be written which will allow the stress calculations to be confirmed quickly using a microcomputer.