同位素稀释质谱法测定铀铌合金中铀含量

根据同位素稀释质谱法原理,推导了铀铌合金中铀含量的计算公式。研究了铀铌合金的分解方法,优化了取样量和稀释剂用量,探讨了质谱谱线干扰和合金元素干扰对测量结果的影响。加入硝酸和氢氟酸定量溶解铀铌合金,再定量加入铀同位素稀释剂,直接制备成混合试样溶液,应用质谱法测定混合溶液、铀铌合金试样的铀同位素比,最后计算出铀铌合金中铀含量。确定的方法无需定量分离铀。为了对分析结果的准确性进行验证,应用XRF法、ICP-AES法和元素分析法测量铀铌合金中铌含量和杂质元素总量,反推得到相应的铀含量,其结果同实验方法的结果是一致的。对铀铌合金样品进行分析,测定结果的相对标准不确定度为0.2%（6次测定）,扩展不确定度为0.5%（95%置信水平）。

Determination of uranium in U-Nb alloy by isotope dilution mass spectrometry

According to the principle of isotope dilution mass spectrometry, the calculation formula of uranium content in U-Nb alloy was deduced. The decomposition method of U-Nb alloy was studied and the sampling and spike amount were optimized. Moreover,the interference of mass spectra and alloy element on the testing result was studied. U-Nb alloy was dissolved by HNO₃ and HF,after which quantificational U isotopic tracer was mixed with. Then,the mixed solution was gotten,and the isotopic ratios of U in the mixed solution and U-Nb alloy were measured by mass spectrometry.Finally,the content of U in U-Nb alloy was calculated. Quantitative separation of uranium was not required in the ascertained method.In order to confirm the accuracy of analysis result, XRF, ICP-AES and element analysis method were used to determine the content of U and impurity elements in U-Nb alloy. Uranium content in U-Nb alloy was obtained backward, with the results consistent with the proposed method. The method was used to analyze U-Nb alloy sample, with the relative standard uncertainty of 0.2% (n=6) and expanded uncertainty of 0.5% (confidence level 95%).