Objectives  The effect of thermal discharge on the temperature of the cooling water at the water inlet of the floating nuclear power platform is studied in this paper.

  Methods  The finite volume method combined with Reynolds average method were used to simulate numerically the thermal diffusion in the external flow field in three dimensions.

  Results  The numerical simulation of the turbulent flow for the thermal water diffusion was carried out, and the results are in good agreement with the model test results. When the flow velocity of seawater is low, the thermal discharge diffuses along the flow direction of water at the outlet, which has little influence on the temperature field of the water flow at the inlet. When the flow velocity of seawater is high, the thermal discharge diffuses along the flow direction of the seawater, which has a great influence on the temperature field of water flow at the inlet.

  Conclusions  The results of this paper can provide guidance for the design of the floating nuclear power platform.