Assessing the SCRRI and RIP runback performances of TRACE/PARCS for Lungmen ABWR

Highlights: • Performance of SCRRI and RIP runback simulated by TRACE/PARCS for Lungmen ABWR. • TRACE/PARCS model is a best-estimate calculation for 3-D core performance. • Responses simulated are in reasonable agreement with startup test prediction. • Compared to RIP runback, SCRRI is a slower measure to coast down power. - Abstract: The TRACE/PARCS model is conventionally adopted as a best-estimate calculation approach for the Lungmen advanced boiling water reactor (ABWR). This study assesses the performance of SCRRI and RIP runback simulated by TRACE/PARCS featuring three-dimensional evaluation. The effectiveness of TRACE/PARCS is demonstrated by selecting the two transients in the startup test prediction, feedwater pump trip and loss of feedwater heater, which are involved with the initiation of both SCRRI and RIP runback. Calculation results indicate that SCRRI is a slower measure than the runback mechanism in mitigating the steam flow dumped into the main condenser, subsequently reducing the power to another state. Additionally, RIP runback is alternative approach to diminishing the power by reducing the core flow. Moreover, sensitivity studies involving different settings for RIP runback and SCRRI are also performed to determine the SCRRI and RIP runback delay times, as well as RIP runback rate. Sensitivity studies reveal that the operational settings of SCRRI and RIP runback influence the process during transients. Nevertheless, the setting does not significantly impact the final state of the transient