Development and validation of a subchannel analysis code for PWRs based on the two-phase and three-field model

Abstract

The pressurized water reactor (PWR) continues to be the most prevalently operated reactor type worldwide, with core thermal-hydraulic analysis constituting a crucial aspect of overall reactor design. To achieve a refined distribution of key physical fields within the core and enhance both reactor safety and economic efficiency, the SACOS (Subchannel Analysis Code Of Safety) V3.0 (hereinafter referred to as SACOS) code was developed based on a two-fluid, three-field model at the pin-by-pin level for PWR cores. This code incorporates closure relations such as wall friction, heat transfer, turbulent mixing, and interfacial interaction. It utilizes the finite difference method and the SIMPLE algorithm for numerical discretization and solution, facilitating fine-scale simulations of the entire reactor core. The physical models of the code were validated against experiments such as the GE-3✕3 rod bundle mixing test, the CE-5✕5 heat transfer test, the PNL-7✕7 flow blockage test, the CE-15✕15 inlet stream test and the THTF-8✕8 dispersed flow test, demonstrating good agreement between the computed and experimental results, thereby verifying the accuracy of the models. Finally, the code was applied to steady-state full-core calculations of a typical PWR and transient calculations under SBLOCA conditions for a single assembly, with comparative analysis on the impact of the droplet phase on cladding temperature under high void fraction conditions. The results demonstrate that SACOS is capable of both steady-state and transient core simulations. It can be concluded that the SACOS code provides an effective tool for PWR safety analysis and design.