Core Protection Method with 4-Channel CEA Signals for Application of OPR-1000 Plants

In digital protected nuclear power plants, Core Protection Calculator System (CPCS) is used for a core protection based on several online measured system parameters. The CPCS provides four independent channels for the departure from a nucleate boiling ratio (DNBR) and local power density (LPD) trip signals to the reactor protection system. Each channel consists of a Core Protection Calculator (CPC) and a Control Element Assembly Calculator (CEAC). This system has been used in OPR-1000 plants in Korea and it is reported that several abnormal trip generations have been caused by a transmission of improper penalty factors and by a failure of CEA related hardware. The Korea Atomic Energy Research Institute (KAERI) has been developing a system-integrated modular advanced reactor (SMART) with an on-line digital core protection system for a seawater desalination and electricity generation. To overcome the generation of abnormal trips in a conventional CPCS and increase the applicability of research results established during the process of an integral reactor development, a new core protection method with 4-channel CEA positions was suggested and its feasibility was evaluated. In addition, this paper describes the state-of-the-art related to a core protection system in various countries