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Sodium combustion oxide aerosols are the main carriers of radioactive materials in a sodium-cooled fast reactor (SFR) during sodium fire accidents. Therefore, it is of great significance to simulate aerosol behavior in sodium pool fires to evaluate radioactive source terms in the containment or environment. In this work, a numerical method has been developed to simulate sodium oxide aerosol behavior during sodium pool fires. The Classical Nucleation Theory has been taken into account to simulate gas-to-particle conversion (GPC). The model has been evaluated theoretically in 280 cases with three main parameters: sodium pool temperature, pool diameter, and oxygen concentration. The correlation established by fitting data points is associated with the sodium evaporation rate. The SFA code has been developed based on advanced sodium pool combustion and aerosol models coupled with GPC correlations. In comparison with the experimental data, the code-calculated average atmospheric temperature, airborne aerosol concentration, and particle size are in good agreement with the data, which indicate that the method is reliable and can be applied in code development in the future. [ABSTRACT FROM AUTHOR]

Volume of fluid (VOF) method combined with primary breakup model (PBM) is developed to model large flow rate pressure-swirl nozzle used in pressuriser of the pressurised water reactor (PWR) power plant system. For the VOF model, the renormalisation-group (RNG) K- ϵ model is selected to ensure the accuracy of simulation for swirling flows. The 3-D transient flow is simulated and the dynamic stability of the injection pattern is analysed for the nozzle. Based on the growth rate of the disturbance at the interface of the two phases, PBM is embedded in the VOF model in the form of user defined functions (UDF) to investigate the further breakup from sheet to spray drop and predict the spray drop size spectrum. In addition, experimental studies, considering the characteristics of mass flow rate, spray cone angle, spray flux distribution and drop size spectrum, were conducted to verify accuracy of the numerical results. The result of comparison shows that there is good agreement between the simulated results and the experimental data. Especially, the distribution tendency of the spray drop size simulated by PBM fits the experimental value well and the drop size corresponding to the maximum probability is predicted successfully. The present investigation shows that the VOF-PBM methodology can be applied to simulate the pressure-swirl nozzle and optimise design of spraying systems. [ABSTRACT FROM AUTHOR]

• A numerical simulation method for the coupling flow and heat transfer process of liquid metal HCOTSG is proposed. • The correctness of the method is validated by comparing with relevant experimental research, and the maximum error is less than 25%. • The flow and heat transfer characteristics of liquid metal HCOTSG under different working conditions are analyzed. Much attention has been focused on the Liquid Metal Fast Reactor (LMFR) as one of the most promising concepts for GEN-IV reactors. Helical coil once-through tube steam generator (HCOTSG) is a proposed form of steam generator. Due to its unique advantages, HCOTSG is widely used in various reactor power systems, including LMFR. In this paper, a numerical approach is proposed to simulate heat transfer from the primary side (liquid metal) and secondary side (water/steam). The liquid lead-bismuth eutectic (LBE) is flowing in the shell side and pressurized water is flowing in the tube side. FLUENT CFD commercial code is adopted for the simulations. The robustness of the method is validated by comparing it with relevant experimental research, and the maximum error is less than 25%. Based on this method, the distribution of thermal-hydraulic parameters inside HCOTSG is obtained and the flow and heat transfer characteristics are analyzed. The influence of boundary conditions and geometric parameters on the flow and heat transfer in HCOTSG is analyzed. The comprehensive performance of different models is compared with the comprehensive performance evaluation index. The optimal geometric arrangement scheme for the working conditions is recommended. Compared with the reference model, the comprehensive performance can be improved by up to 14%. This study provides a numerical simulation method reference for the study of flow and heat transfer characteristics and structural design optimization of liquid metal HCOTSG. [ABSTRACT FROM AUTHOR]