Abstract: In this study, a multi-physics mathematical model coupling turbulent flow, species transport, chemical reactions, and energy conservation was established to conduct numerical simulation research on the heat transfer characteristics inside the sodium-water impact reaction vessel, and the accuracy of the model was verified through experiments. The main conclusions are as follows: Comparison with experimental data shows that the average liquid temperature obtained by numerical simulation shows good agreement with the experimental measurement values, with a relative error of less than 9%, indicating that the established mathematical model can accurately reproduce the dynamic processes inside the sodium-water impact reaction vessel. The temperature distribution inside the reaction vessel presents spatial inhomogeneity. After the reaction stabilizes, the temperature of the vessel wall is the most uniform, while there are obvious temperature gradients inside and in the middle of the casing tube. The casing tube structure exerts a blocking effect on heat transfer, resulting in an overall lower temperature inside it compared to the middle region. The inlet temperature of sodium hydroxide solution is a key operating parameter affecting the overall thermal state of the vessel. Studies have shown that although the morphology of the temperature field is similar under different inlet temperatures, the temperature inside the vessel increases significantly and linearly with the rise of inlet temperature. When the inlet temperature increases from 10 ℃ to 40 ℃, the overall stable temperature of the vessel rises correspondingly from 45 ℃ to 75 ℃. Given that high temperature significantly accelerates the corrosion of sodium hydroxide (NaOH) solution on materials such as 316L stainless steel, it is imperative to set an upper limit for the operating temperature from the perspective of long-term safe operation of equipment. The research results of this study indicate that controlling the inlet temperature of sodium hydroxide solution below 40 ℃ can effectively maintain the overall temperature inside the vessel at a relatively safe level, which is an important engineering measure to mitigate corrosion and ensure equipment integrity. In summary, this study reveals the heat transfer mechanism and temperature distribution characteristics inside the sodium-water impact reaction vessel through numerical simulation, clarifies the core significance of inlet temperature control for engineering safety, and provides important theoretical basis and data support for the optimal design and safe operation of waste sodium post-treatment reactors.