光学スペクトル法によるウラン同位体比の測定 : I. 中空陰極放電管光源を用いる235U/238U比の測定

概要

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An emission spectrometric method for uranium isotopic analysis is described. A specially designed hollow cathode discharge tube was employed as the excitation source. A Shimadzu etalon-grating monochromator (MEG-50) was used as the high-resolution spectrometer. The etalon having cemented optical elements kept high finesse without any adjustment for about 6 months. A 50-mg portion of U3O8 powder sample was directly packed into a graphite cup, which was then loaded in the cathode cavity of the water-cooled hollow cathode discharge tube. It is found that an addition of nitrogen to argon carrier-gas was very effective to increase uranium line intensities. Pulsed-current operation was also effective to increase line intensities. Consequently, a relatively small discharge current (-30mA) was sufficient. The output light was stable for at least 2 hours. Uranium-235 concentrations from 0.684 to 20.0 atomic % can be determined with a relative standard deviation ranging from 1.3 to 0.3%.