A Strategy of DNBR On-Line Monitoring and Protection in PWR

Based on the measured parameters, including core power distribution, system pressure, inlet coolant temperature and flow, departure from nucleate boiling ratio (DNBR) can be calculated on-line. This paper presents a strategy to develop the DNBR online monitoring and protection system for PWR nuclear power plant (NPP). The main functions are to provide core DNBR status to operator and to replace the delta-T protection in conventional PWR NPPs. The system structure consists of two different levels respectively for monitoring and protection. There are four cabinets in each level to insure the reliability. DNBR on-line algorithm is on the basis of a modified single channel thermal-hydraulic model. A computer program was developed and verified through comparison with the sub-channel code.