Determination of low-level 54Mn in soils by ultra low-background gamma-ray spectrometry after radiochemical separation

An analytical method was developed for the measurement of low-level ⁵⁴Mn in soil sample by ultra low-background g-ray spectrometry after radiochemical separation. The method consists of decomposition of sample by a mixture of HNO₃ and HF, dissolution by HNO₃, precipitation as hydroxide, solvent extraction with diisopropyl ether and anion exchange. Finally, for purification of Mn it was precipitated as MnO₂ by adding KClO₃. ⁵⁴Mn in the precipitate was measured by ultra low-background well-type Ge detector at Ogoya Underground Laboratory. Measurements of ⁵⁴Mn using 30-200 g of soil samples from the JCO grounds were successfully performed by the present method. The minimum detectable activity of ⁵⁴Mn was about 0.01 dpm (0.2 mBq) for a 7-day counting period.