TINTE analysis of PBMR reactivity insertion transients

Several important PBMR reactivity insertion transients have been simulated by means of the dynamic reactor code TINTE (Time-dependent Neutronics and Temperatures). These transients include total control rod removal during normal operating conditions, cold zero power (CZP) conditions and hot zero power (HZP) conditions, as well as Reserve Shut-down System (RSS) removal during the cold zero power conditions. According to the TINTE results, the worst control rod removal scenario is the total control rod removal during hot zero power conditions in a postulated event with the power conversion unit (PCU) starting up and with continual operation without a trip. The amount of reactivity insertion by the RSS removal is much greater than the reactivity insertion by control rod removal. The event was analyzed but the RSS during the cold zero power conditions is a Beyond Design Basis Accident (BDBA). This paper presents the methodology followed to model these transient events with the TINTE code, as well as total power, maximum and average fuel temperatures and case comparison results. It is also shown that the maximum fuel temperatures for all of the Design Basis Accidents (DBA) are within acceptable safety limits.