Development of High Current Thyristor Controlled Rectifier System for Nuclear Reactor Safety Studies

Abstract

Nuclear power plants are designed to maintain their integrity and performance of safety functions for a bounding set of normal operational events as well as abnormal events that are expected to occur or might occur at least once during the lifetime of the plant. In addition, they are designed to maintain performance of safety functions for a set of design basis accidents that involve failures that are possible but unlikely to occur during the plant lifetime. However, experience of accidents occurred in nuclear power plants shows that accident conditions can occur which threatens the essential function of adequate cooling of the nuclear core. It is essential to validate the safety and safety related system designed for nuclear reactor to cope up the severe accident. During a severe accident, the core can melt and be relocated to the lower plenum of the reactor pressure vessel. The molten corium can be relocated in the containment cavity forming a debris bed if water is present in the cavity. Hence, a scale down experimental test facility in power and volume has been designed with thyristor controlled rectifier system feeding high current to the test section of the facility to simulate the fission heat flux generated after severe accident in nuclear reactor. The paper presents design considerations, development and subsequently the performance of 15 kA thyristor controlled, six pulse rectifier system. The circuit simulation of the rectifier system is also presented.