Influence of effective decay constant uncertainty on radon exhalation rate measurement from medium surfaces using CR-39

The CR-39 solid-state nuclear track detector is a commonly used instrument for passively measuring radon. When using CR-39 to measure the radon exhalation rate from the surface of a medium, the effects of leakage are often overlooked. However, to a certain extent, system leakage can affect the accuracy of the measurement results. Therefore, the effect of different effective decay constants (including leakage) on the radon exhalation rate is worth studying. In this study, both theoretical and experimental validation methods were used to verify the effect of the uncertainty of the effective decay constant on the results of CR-39 measurements of radon exhalation rate from the medium surface. In the theoretical validation, different values of radon exhalation rate can be obtained by substituting different effective decay constants into the CR-39 formula for measuring radon exhalation rate while keeping the other variables constant. In the experimental validation, the radon exhalation rate in the same medium was measured using both CR-39 and RAD7. Since the traditional passive method (CR-39 solid-state nuclear track detector) cannot directly obtain the effective decay constant, the effective decay constant in the CR-39 measurement experiment was replaced by the effective decay constant value fitted from the RAD7 experimental data. The results showed that the radon exhalation rate value measured by CR-39 was much larger than that measured by RAD7. From the theoretical and experimental validation, it is concluded that the uncertainty of the effective decay constant has a significant effect on the radon exhalation rate measured by CR-39.