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SummaryA thermal model for the LS-VHTR (liquid-salt-cooled very high temperature reactor) concept has been developed by using the RELAP5 code. The LS-VHTR concept is proposed to operate at 2400 MWth, and it is cooled by liquid Li 2 BeF 4 (Flibe) salt. An initial thermal analysis of the LS-VHTR concept was performed in a previous work where the simulation of only 1 unit cell was considered. In the present work, the RELAP5 model was increased to represent the complete core with all hexagonal blocks. Also, the salt recirculation has been simulated. The LS-VHTR core inlet and outlet coolant temperatures, heat structures temperature, and pressure drop have been simulated. The results were compared with the available data and demonstrate that the developed model is capable of reproducing the thermal behavior of the reactor in steady-state operation.

Abstract. Angra 2, the second Brazilian nuclear power plant, began the commercial operation in 2001. The plant is a pressurized water reactor (PWR) type with electrical output of about 1350 MW. In the present work, the thermal hydraulic RELAP5-3D code was used to develop a model of this reactor. The model was performed using geometrical and material data from the Angra 2 final safety analysis report (FSAR). Simulations of the reactor behavior during steady state and loss of coolant accident were performed. Results of temperature distribution within the core, inlet and outlet coolant temperatures, coolant mass flow, and other parameters have been compared with the reference data and demonstrated to be in good agreement with each other. This study demonstrates that the developed RELAP5-3D model is capable of reproducing the thermal hydraulic behavior of the Angra 2 PWR and it can contribute to the process of the plant safety analysis.