PERFORMANCE EVALUATION OF CONTROL SAFETY ROD AND ITS DRIVE MECHANISM OF FAST BREEDER REACTOR DURING SEISMIC EVENT

摘要

Control and safety rods & their drive mechanisms (CSRDM) and diverse safety rods & their drive mechanisms (DSRDM) are the main constituents of the two independent shutdown systems in Prototype Fast Breeder Reactor (PFBR) of 500 MWe. There are nine CSR and three DSR placed within the hexagonal sheaths, which in turn are located in two radial banks of reactor core. This paper deals with the analysis carried out to predict the performance of CSRDM along with CSR. Analysis is carried out for the static and seismic loading under the fuel handling as well as normal operating conditions with the objective of ensuring structural integrity as well as to estimate the drop time during seismic event. The effects of bowing of sub-assemblies corresponding to the end of life situation have been considered. From the analysis, it is found that the drop time of CSR is 0.82 s, which is less than 1 s, and hence there is no concern of reactor shutdown. Further, it is ensured that there is no mechanical interaction of concern between various parts. The induced stresses are found to be very much less than RCC-MR allowable stress intensity. Thus the performance of CSRDM and CSR is demonstrated to be sound during normal as well as seismic events.