Study on the Analytical Method for Beta Counting of Cesium-137 in Fallout

[Purpose]: This study aims to establish a reliable beta counting method for cesium-137 detection in fallout samples. [Methods]: Researchers conducted a series of experiments, including digestion system selection experiment, phosphomolybdic acid ammonium adsorption system selection experiment, nitric acid-ammonium chloride detergent substitution experiment, and interference elimination experiment. Referring to the instrument scale and cesium iodobismuthate precipitation source preparation method in HJ 816-2016, and combining with low-background alpha/beta measuring instruments for sample measurement, a beta counting method suitable for cesium-137 in fallout was established. [Results]: Comparative analysis with the GB/T 16145-2022 method showed no significant differences in sedimentation sample detection. Validation experiments demonstrated that the method met precision (relative deviation of parallel samples ≤30%) and accuracy (The recovery rate of spiked samples was 80%~120%) requirements specified in HJ 61-2021. [Conclusion]: Experimental results demonstrate the viability of the beta counting method for cesium-137 in fallout samples developed through this research,Meanwhile, the research results can provide technical references for the construction of relevant standard systems.‌