Assessment of the mechanical consequences of thermal stratifications in elbow geometries

Analysis of incidents due to thermal stratification phenomena in the fluid circulating in certain PWR primary and secondary piping has evidenced the necessity for an overall methodology to determine the origin and assess the mechanical consequences. Since 1990, R and D have assembled a team comprising specialists in thermal hydraulics, mechanics and materials in the framework of a Multiannual R and D Project on the subject. This report presents the main developments and results obtained. It stresses the advantages of an approach associating experimental (site and mockup tests) and numeric methods (ESTET and ASTER codes) and describes the general tools developed in this context. (authors). 8 figs., 8 refs