Research on Calculation Methods of Important Parameters in Radioactivity Measurement

Abstract [Background]: Radioactivity measurement is widely used in various fields of nuclear technology application. The measurement uncertainty, confidence interval and detection limit are important parameters of radioactivity measurement. Different calculation methods may get different results, and the calculation results directly affect some important and relevant decisions. [Purpose]: It is important to analyze whether the calculation method is used properly. [Methods]: The important parameters of α particle activity concentration measurement were studied by partial derivative method and Monte Carlo method. In this study, based on the measurement of α activity concentration, the sources of uncertainty for the measurement results were analyzed. The measurement uncertainty, confidence limits, decision threshold and detection limit of α particle activity concentration under different input modes were derived and calculated by partial derivative and MC methods. [Results]: The results show that when the input uncertainty is higher than 10%, the relative deviation between confidence interval and uncertainty results obtained by the two calculation methods is greater than 15%. When the relative uncertainty of the input is small, the detection limit is about 2 times of the decision threshold. [Conclusions]: The partial derivative method is widely used, but it does not consider the probability distribution of the input, and it is not suitable for complex and special input models. Under the circumstances, Monte Carlo method can be used to obtain more reliable calculation results. The two approaches can be applied in complementary ways.