核电厂低放射性废水对水库库区影响的数值模拟研究

Numerical simulation research on impact of low-level liquid radwaste of nuclear power plant on a reservoir

研究核电厂低放射性废水在受纳水体中的迁移扩散规律对环境保护的重要意义.针对某水库库区内一拟建核电厂,在充分考虑水体对流、扩散、核素沉积及衰变等作用的基础上,建立了三维低放废水数学模型.利用该模型,模拟分析了不同排放条件、来流条件和坝前水位情况下,核电厂排污口下游核素的三维分布规律.结果表明:稀释倍率包络线汛期窄长,枯期宽短;低放废水出流后,与环境水体迅速掺混,各方案均未出现5倍稀释包络线;坝前水位145、155m时低放废液对水库中层影响范围最大,坝前水位175m时,低放废液排放对底层影响范围最大;枯水期排放口下游500m处最大相对浓度0.009 52,各层稀释倍率稳定时间均为20d.

Researching on the migration and diffusion of the low-level liquid radwaste of nuclear power plants in the receiving water bodies is of great importance to environment protection.Considering the hydrodynamic convection-diffusion processes and the deposition/decay process of the nuclides,a three-dimensional numerical model is developed to describe the transport processes of radionuclide in a reservoir.The model is used to simulate three-dimensional distribution of the nuclide along the river under different discharge conditions,hydrological conditions and water levels of the reservoir.The results show that,the shape of dilution ratio envelope is narrow and long in flood season,wide and short in dry season.After outflow,the low-level liquid radwaste mixed quickly with environment water,5 times dilution ratio envelope does never appear in any calculation scheme.When the upstream water level of the dam is 145 m and 155 m,the sphere of influence by the low-level liquid radwaste is largest at the middle layer of the reservoir;while 175 m,the sphere of influence is largest at the bottom layer.The maximum relative concentration at downstream 500 m of outfall in dry season is 0.009 52 and the stability times of dilution ratio to each depth-layer are 20 d.