Creep-fatigue Damage Analysis of Lower Stay Plate in Control Plug

In Prototype Fast Breeder Reactor, the lower stay plate made of SS 316 LN in control plug has cut opening in three locations for the purpose of easiness of assembling the sampling tubes through the lower stay plate. These openings are then covered with appropriate cover plates bolted with the stay plate. The stay plate along with cover plate will be seeing thermal transients during reactor scrams. The thermal transient will cause the membrane stress due to global temperature increase in cover plate and bending stress due to temperature gradient across the thickness. This paper aims the creep and fatigue damages estimation of the stay plate and covers plate. The material of stay plate and cover plate is SS 316 LN. The stay plate and cover plate is analysed using CAST3M FE software developed by CAE France. A small square segment including a bolt and portion of junction between stay plate and cover plate is modeled with 8 noded, CUB8 elements. The fatigue damage for 851 number of thermal transient has been calculated. The creep damage due to the thermal stress has been evaluated. The interaction of creep-fatigue damage has also been evaluated as per RCC-MR code rule and is found within the limit. (C) 2013 The Authors. Published by Elsevier Ltd.