电位滴定法测定基准 U3 O8中铀的不确定度评定

摘要

分析了电位滴定法测定基准 U3 O8中铀总量的检测过程,建立了测量过程分量的数学模型,讨论和比较了检测过程中各种不确定度因素,发现各不确定度因素中称样量的不确定度贡献最大,其次是测量重复性和消耗重铬酸钾质量的不确定度,K2 Cr2 O7相对分子质量和 U 的相对原子质量对不确定度结果的影响可忽略。结果表明,采用电位滴定法测定基准 U3 O8中铀总量,当样品中铀的总量为84.795%时,扩展不确定度为0.022%(k =2)。%The determination of total uranium in primary reference material U3 O8 by poten-tiometric titration method was discussed.A mathematical model of measurement component was established to compare the uncertainty factors during measurement process.It was found that the uncertainty of quantity of samples has maximal contribution,the uncertainties of measurement repeatability and quantity of consumed potassium dichromate are in the second place,and the effect of K2 Cr2 O7 relative molecular mass and U relative atomic mass to the final uncertainty factors is minimum.The results show that,when potentiometric titration method is used to determine total uranium in U3 O8 ,an expanded uncertainty of 0.022%(k =2)is recorded at total uranium of 84.795%.