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延迟系数是描述核素在地质介质中迁移的最重要的参数之一,而且通常都被当作常数使用。该工作的目的是为了说明(1)延迟系数Rd是否常数?(2)如果Rd不是常数,它对计算结果能有多大影响?(3)由分配系数kd按照传统方程推导的Rd是否适用于安全评价?通过对核素在非饱和黄土中迁移实验结果的分析,达到了上述目的。实验结果表明,在非饱和条件下,85Sr的Rd不是常数,而是随土壤含水量θ的增加而增大;由kd按照传统方程推导的Rd不能用于安全评价;用于安全评价的Rd应该由实际测量得到,而不能由kd推导。通过计算表明,Rd对计算结果影响极大。
The delay coefficient is one of the most important parameters describing the migration of nuclides in geological media and is often used as a constant. The purpose of this work is to show whether (1) is the lag coefficient Rd constant or not? (2) if Rd is not a constant, how much does it have on the result of the calculation? (3) whether the Rd derived from the traditional equation by the distribution coefficient kd applies to safety Evaluation? The above objective has been achieved by analyzing the experimental results of nuclide migration in unsaturated loess. The experimental results show that under non-saturated conditions, Rd of 85Sr is not a constant, but increases with the increase of soil water content θ; Rd derived from kd according to the traditional equation can not be used for safety evaluation; Rd for safety evaluation should be Measured by the actual, but not derived by kd. Calculations show that Rd has a great impact on the calculation results.