不同激发方式对能量色散X射线荧光法测铀的影响

针对能量色散X射线荧光法测铀过程中存在自激发效应对测量结果产生干扰的问题及以往测铀仅使用放射性同位素源作为激发源的测量限制，利用微型X射线对铀矿样品进行自激发效应测量，并分别将109Cd，241Am，微型X光管三种不同激发源测量铀矿样品的结果进行比较分析。结果表明，自激发效应产生的特征X射线峰面积计数仅为有源条件的0.01%以下，属统计涨落范畴，对测量结果的干扰可忽略不计;109Cd源由于其特征射线能量22.11和24.95 keV均在L_α吸收限能量21.75 keV附近，激发光电截面最高，相应的荧光产额也高，故109Cd源相比于241Am源对铀元素的激发效率更高;241Am源测量误差明显大于109Cd源的测量误差，原因是铀的L系能量特征峰与241Am源特征射线26.35 keV的散射峰能量区叠加，造成实测谱线本底偏高;X光管作激发源的铀矿样品中铀含量与化学分析结果之间的误差在10%以内，仅为同位素源激发X射线荧光分析误差的一半，且X光管激发谱峰面积计数值明显大于源激发条件下的峰面积计数，说明X光管作激发源的测铀质量优于源激发模式。

Influence of the Experiment Energy Dispersive X-Ray Fluorescence Measurement of Uranium by Different Excitation Source

Aiming at the self-excitation effect on the interference of measurements which exist in the process of Energy dispersive X-ray fluorescence method for uranium measurement. To solve the problem of radioactive isotopes only used as excitation source in determination of uranium. Utilizing the micro X-ray tube to test Self-excitation effect to get a comparison of the results obtained by three different uranium ore samples—109Cd，241Am and Mirco X-ray tube. The results showed that self-excitation effect produced the area measure of characteristic X-ray peak is less than 1% of active condition, also the interference of measurements can be negligible. Photoelectric effect cross-section excited by 109Cd is higher, corresponding fluorescence yield is higher than excited by 241Am as well due to characteristics X-ray energy of 109Cd, 22.11 & 24.95 KeV adjacent to absorption edge energy of L_α, 21.75 KeV, based on the above, excitation efficiency by 109Cd is higher than 241Am; The fact that measurement error excited by 241Am is significantly greater than by 109Cd is mainly due to peak region overlap between L energy peaks of uranium and Scattering peak of 241Am, 26.35 keV, These factors above caused the background of measured Spectrum higher; The error between the uranium content in ore samples which the X-ray tube as the excitation source and the chemical analysis results is within 10%. Conclusion: This paper come to the conclusion that the technical quality of uranium measurement used X-ray tube as excitation source is superior to that in radioactive source excitation mode.