Bubble Behaviors in a Fuel Assembly of Accelerator Driven System

The accelerator driven system (ADS) is a nuclear reactor that can burn spent nuclear fuel with inherent safety features and operational flexibility. China is developing an ADS research device named China Initiative Accelerator Driven System (CiADS). The steam generator is one of the most important parts in the primary circuit of CiADS. The rupture of steam generator tubes may cause a significant impact on the reactor core due to potential risks of steam bubble intrusion into the core region. When the steam generator tube-rupture accident occurs, the primary coolant turns to a two-phase flow, which may cause variations of flow conditions through fuel assemblies. This paper adopted the open-source computational fluid dynamics calculation software OpenFOAM, and performed numerical simulations of a two-phase flow scenario in the ADS fuel assembly with the volume-of-fluid method. By changing boundary conditions at the assembly inlet, different scenarios of steam bubble intrusion were simulated and compared, based on our preliminarily conclusion that steam bubbles evenly distributed at the assembly inlet tend to accumulate at the periphery region, which partly confirmed the necessity of building experimental facilities for relevant two-phase flow research.