A METHOD USING DI-(1-METHYLHEPTYL)METHYL-PHOSPHATE CHROMATOGRAPHIC SEPARATION FOR MEASURING THE ACTIVITY RATIOS OF ~(234)U/~(238)U AND ~(230)Th/~(232)Th BY ALPHA- SPECTROMETR Y

After ammonium hydroxide is added into 5-10 litres of an aqueous sample containing ferric chloride as carrier, uranium and thorium are concentrated by coprecipitation with ferric hydroxide.The precipitate is dissolved in 20% nitric acid and 2% tartaric acid.The solid samples are dissolved with mixed ammonium salt and adjusted to the same acidity.The uranium and thorium are separated and purified on the di- (l-me'thyiheptyi) methylphosphate (com-merical name p350) -macroporous resin column.The purified samples are eleet-rodeposited on stainless steel disk and determined by alpha-spectrometry.This method can be used for determination of high content iron samples and high level uranium-low level 'thorium or high level thorium-low level uranium samples,The detection limit obtained from 5 litres of aqueous sample is 1-2μg/l, whereas that of solid samples is 5μg/g.