核废料处置库近场温度半解析研究

Semi-analytical solution of near-field temperature innuclear waste disposal repository

核废料处置库的温度场演化规律是处置库设计和安全评估的重要依据,根据处置库的概念化设计,建立了单个核废料废物罐的分层热传导模型。对膨润土区和围岩区热传导方程组进行Laplace变换,联立求解得到了在不同内外边界条件组合情况下变换域内的温度场半解析解。采用Crump方法对半解析解进行数值反演,获得废物罐近场时间-空间域的温度分布,最后分析了不同参数条件下单个废物罐表面温度的变化规律。结果表明,核废料的燃烧值越高,冷却时间越短,废物罐表面温度越高;采用有限外边界条件计算得到的废物罐表面温度要高于无限外边界条件;膨润土的导热系数越大,废物罐表面温度越低,膨润土土层厚度越厚,越不利于内部温度的扩散。研究成果可用于评价不同条件下废物罐近场温度的演化规律。

The evolution of the temperature field in the nuclear waste repository is an essential basis for the design and safety assessment of the repository.The layered heat transfer model of a single nuclear waste container was established,according to the conceptual design of the disposal repository.The Laplace transform was applied upon the equations of heat conduction in the bentonite and surrounding regions,and the semi-analytical solutions of the temperature field were derived in the Laplace domain under different combinations of internal and external boundary conditions.The temperature distribution in the near-field time-space domain of the waste container was obtained by numerical inversion of the semi-analytical solution using the Crump’s method.Finally,the evolution of the surface temperature of single waste container under different parameter conditions was analyzed.The results show that the higher the burn-up value of nuclear waste is and the shorter the cooling time of nuclear waste is,the higher the surface temperature of the waste container is.The surface temperature of the waste container calculated by the finite external boundary condition was higher than that calculated by the infinite external boundary condition,the higher the thermal conductivity of bentonite is,the lower the surface temperature of the waste container is.The thicker the bentonite soil layer is,the worse the internal temperature diffusion is.The results provide references for evaluating the evolution of the near-field temperature of waste container under different conditions.