A comparative study on numerical simulation and prototype observation of thermal effluents from a nuclear power plant

Prototype observation of thermal discharge from operating power plants is the primary means adopted in China for verifying the accuracy of thermal-discharge numerical models. However， the temperature fields obtained from such prototype observations incorporate complex background water temperatures， while the models usually assume a uniform background temperature. Since the impact of baseline values on verification accuracy is unclear，there is an urgent need to carry out relevant research. This paper takes a certain nuclear power plant site as an example. The water temperature variation processes in the project sea area through a real-time surface heat flux simulation approach based on spatial and temporal varied metrological and hydrological conditions. The numerical model is then validated using diverse in-situ observation data sources， including satellite remote sensing， airborne remote sensing， and surface water measurements. The calculated temperature results are in good agreement with the measurements. Then the impact of the background water temperature value on the extraction of the temperature rise field is analyzed， as well as the sensitivity of numerical simulation results to the values of the diffusion coefficient， heat dissipation coefficient， and wind field. The results show the background temperature distribution has obvious effect on the observed temperature rise determination. Using a uniform background value will result in an opposite seasonal trend in the temperature rise field—overestimation in summer and underestimation in winter. The marine wind field has the greatest impact on the pattern and covered area of the temperature rise field. The diffusion coefficient and heat dissipation coefficient show different in their sensitivity to the calculated temperature rise result， as the diffusion coefficient has a greater impact on the 4 ℃ temperature rise zone， while the heat dissipation coefficient has a greater impact on the 1 ℃ temperature rise zone. This study provides an important reference for enhancing the accuracy of thermal discharge modeling and promoting thermal discharge impact assessment.