SMILE: Interpretation of WP4 PTS Transient Type Experiment Performed on a Cracked Cylinder Involving Warm Pre-Stress

Abstract

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to PTS transients made at an European level generally not always account the beneficial effect of load history (warm pre-stress WPS) on vessel resistance regarding the risk of brittle failure. A 3-year Research & Development program — SMILE — has been started in January 2002 as part of the 5th Framework Program of the European Atomic Energy Community (EURATOM). The SMILE project — Structural Margin Improvements in aged embrittled RPV with Load history Effect — is one of a cluster of 5th framework projects in the area of Plant Life Management. It aims to give sufficient elements to demonstrate, to model and to validate the beneficial WPS effect in a RPV assessment. Within the framework of the project, an important experimental work has been conducted including WPS type experiments on CT specimens and one PTS type transient experiment on a large component. The WPS type experiment on the cylinder has been successfully conducted by MPA Stuttgart with a final brittle failure during the reloading. The present paper shortly describes the experiment and presents the corresponding analyses based on engineering methods, finite element elastic-plastic computations, and local approach to fracture. The results are in good agreement with the experimental observations. Very significant margins are underlined, with an effective important increase of the material resistance regarding the risk of brittle failure.