Study on the Weights of Influencing Factors Contribution to Background Count Rate in Liquid Scintillation Measurement

Abstract The background count rate is a key factor to MDA and accuracy of measuring gross alpha and gross beta in water sample using liquid scintillation analysis. In this paper, the weights of the measurement environment, the material of scintillation vial, the volume of scintillation cocktail, type and volume of sample solvent to the background count rate were studied in Tsinghua University Laboratory and China Jinping Underground Laboratory using liquid scintillation counter. The weight of the external measurement environment is more than 60% to the background count rate in Tsinghua University Laboratory. The wights of the volume of the liquid scintillation cocktail, pure water and 0.05M nitric acid are linearly positive correlation to the background count rate. Pure water and 0.05M nitric acid were used as sample solvent, the weights of the volume of the two kinds of sample solution to the background count rate are comparable. At the same volume, the weights of pure water and 0.05 M nitric acid to the background count rate are lower compared to weight of the liquid scintillation cocktail to the background count rate. Compared with low-potassium glass scintillation vial, plastic scintillation vial has a lower weight to the background count rate. The results can provide data support to reduction of background count rate of liquid scintillation measuring gross alpha and gross beta in water samples, optimization of measuring condition and promotion of detection capability.