Development of the fuel assembly pin-by-pin model in the KORSAR/GP code

摘要

This paper presents the pin-by-pin thermal-hydraulic model of the fuel assembly (FA) developed with the KORSAR/GP code. Its application for simulation of separate fuel rods in the FA is demonstrated.Usually the safety margins are calculated using a "hot channel" model for NPP (Nuclear Power Plant) safety analysis. This approach is conservative. The pin-by-pin simulation provides more realistic results and wider safety margins.The new KORSAR/GP pin-by-pin model was cross-validated with the TIGR-SP code which is used by OKB "GIDROPRESS" for FA steady-state operation assessment. DNBR (departure from nucleate boiling ratio) difference between KORSAR/GP and TIGR-SP does not exceed 3%. Thus, the KORSAR/GP pin-by-pin model provides correct results.The nodalization of the developed model consists of parallel 1D hydraulic elements (channels). The cells of these channels are connected to each other by special elements - cross junctions and turbulent mixing elements (CJ and TM). The paper also deals with the investigation of influence of these elements on DNBR calculation.