Progress on the Development of DAYU3D Code for HTR Thermal-Hydraulic Design and System Analysis

Abstract System analysis code is an important tool for thermal-hydraulic design and accident analysis of nuclear reactors. At present, the commonly used system analysis codes for pebble-bed high-temperature gas-cooled reactor (HTR), such as THERMIX and TINTE, adopt two-dimensional (2D) models in the reactor core. A new three-dimensional (3D) thermal-hydraulic design and system analysis code named DAYU3D is being developed by the Institute of Nuclear Energy and New Energy Technology (INET) at Tsinghua University. DAYU3D is able to calculate 3D solid temperature, one-dimensional (1D) multi-batch fuel element temperature, 3D gas flow, and 3D gas temperature. Porous media model is employed to perform the 3D temperature and flow field calculations for the entire reactor. In the pebble bed core, DAYU3D employs 1D thermal conduction model to accurately obtain the temperature distribution inside the fuel element. By comparing calculation results with SANA experimental data, the 3D solid temperature module of DAYU3D in steady state is validated. Also, the three-dimensional and multi-batch calculation capabilities of DAYU3D are demonstrated through the calculation of a sample steady state case for pebble-bed reactor. It is expected that DAYU3D will provide an excellent platform for the research of complex 3D problems and facilitate the precise design of HTR.