Development of a multi-compartment containment code for advanced PWR plant

HPR1000 (Hua-long Pressurized Reactor) Nuclear Power Plant is a type of third generation advanced PWR developed in China. In this study, a home-made multi-compartment containment code, ATHROC (Analysis of Thermal Hydraulic Response Of Containment), was developed to analyze the thermal-hydraulics and hydrogen behaviors in HPR1000 containment. Two types of bulk fluids, the atmosphere bulk fluid and the pool bulk fluid, were used to model the transient behaviors of multiphase flow. The atmosphere bulk fluid consists of steam, noncondensables and homogeneously dispersed liquid droplets. The code contains comprehensive models, including flow model, heat and mass transfer model, engineering safety feature model, etc. A plume model was implemented to assess buoyancy driven plume movement inside a compartment. A counter-current flow model was developed to evaluate the buoyancy driven bidirectional exchange flow through the junctions. Also, a film tracking model was developed to simulate film flow on the contiguous walls. Special methods such as using variable time steps and non-uniform nodalization for heat sinks were applied to speed up the computation. Code assessments were carried out by simulating several separated effects tests (Phebus FPT0 test, JAERI tests) and integral effects tests (CVTR tests, NUPEC M-7-1 test). Comparing results between code simulations and experimental data showed that the code was capable of providing reasonable predictions.