Effect of ECCS cold-leg injection angle on thermal hydraulic characteristics and core recovery during LBLOCA in a PWR

Abstract

The Emergency Core Cooling System (ECCS) is actuated following Loss of Coolant Accidents (LOCA) to inject coolant into the primary loop through a T-junction configuration in nuclear power plants. The injection angle; i.e., the T-junction angle, in the cold leg injection system in a pressurized water reactor is an important parameter during a postulated LOCA. The amount of the break flow rate and the time at which the refill period initiates impact the thermal-hydraulic behavior of the reactor coolant system and eventually affect the integration of reactor nuclear core. In the current work, RELAP5 code is used to study the effect of the cold leg injection angle on LOCA scenario in a standard four-loop Westinghouse Pressurized Water Reactor (PWR). Injection angles investigated in the study are 45°, 90°, and 135°. The whole reactor system is simulated using RELAP5 code whilst the injection junction is numerically developed using ANSYS-FLUENT commercial code. The break flow, core recovery, and thermal-hydraulic parameters are calculated for the different injection angles. Research results are validated with published data available in the literature. The results manifest that the injection angle of 45° gives the highest and the most uniform core level during the core refilling phase, the best temperature behavior for both fuel centerline and maximum cladding temperatures, where both temperature distributions reach a stable value earlier than that of the other angles. ANSYS-FLUENT code is utilized to explain the complex mixing phenomena of fluids during the analysis.