内陆核电厂冷却塔对大气扩散影响的CFD模拟

 风场的时空变化和大气湍流特征是影响局地大气污染物迁移、扩散的重要因子。本文以某内陆核电厂址为背景,针对内陆核电厂址气象及地形条件的复杂性,选用三维计算流体动力学(CFD)模型Fluidyn-PANACHE,模拟气载放射性颗粒¹³⁷Cs、气溶胶¹³¹I和常规气态污染物CO在大气中的三维风场及浓度场分布情况。该方法可合理模拟内陆核电厂大型冷却塔等建筑物周围的湍流和绕流,弥补了标准高斯模型精细化程度不足的缺陷。此外,该方法也突破了常规CFD模型很难在一次计算中进行多风向模拟的局限性。计算获得的正常工况下年均大气扩散因子能反映出该厂址大气扩散的季节性差异,即秋季的平均大气扩散因子最大,因此,可考虑将换料大修等非运行工况安排在秋季进行,以降低污染强度。研究获得的年均大气扩散模拟结果与高斯混合排放模式推荐的厂址扩散参数较为一致,典型固定风向的模拟结果与风洞物理模拟结果符合较好,可为中国内陆核电厂址大气扩散研究和评价提供参考。

CFD Simulation of Atmospheric Dispersion Influenced by Cooling Towers in Inland Nuclear Power Plant

The spatial and temporal variations of wind field and the atmospheric turbulence characteristics are important factors that affect the migration and dispersion of local atmospheric pollutants. Considering the complexity of meteorological and landform conditions around the inland nuclear power plant, the 3-Dimensional wind field and concentration field distribution of airborne radionuclide particle ¹³⁷Cs, aerosol ¹³¹I and conventional gas pollutant CO dispersion in the atmosphere were carried out by a 3-Dimensional CFD (computational fluid dynamics) model Fluidyn-PANACHE. This method can be used to reasonably simulate the turbulent and circumferential flow around large cooling towers in the inland nuclear power plant, compensating the shortage in subtleness of the standard Gaussian model, as well as shortage in realizing multi-wind direction simulation in the calculation by the traditional CFD model. The calculation results of annual average atmospheric dispersion factor under normal operation indicated the seasonal differences, with maximum average dispersion factor in autumn, which were consistent with those suggested by Gaussian mixture model. Consequently, it's reasonable to arrange refueling overhauling in autumn to diminish pollution. The numerical simulation results from four typical fixed wind directions were compared and they are consistent with the observed values of wind tunnel experiments, providing new references for atmospheric dispersion research and evaluation on inland nuclear power plants in China.