Abstract： 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%).
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