The Influence Of Different Sieve Diameters And Geometric Position On The Accuracy Of FRN Measurement

2.00mm is often used as the standard sieve diameter for determining the specific activity of¹³⁷Csand²¹⁰Pb in soil samples, but it is rarely reported that whether the size of the different screening willaffect the accuracy of such determination. This study selected three representative soils, includingcinnamon soil, chestnut soil and purple soil, to assess the effects of different sieve sizes on measurementof¹³⁷Cs and²¹⁰Pb activity in soil samples by using HPGe γ spectrometer. The target soil samples eachwere passed through the four sieve diameters2.00mm,1.00mm,0.50mm and0.25mm, respectively. Itwas observed that the sample of0.25mm had shorter time to reach the acceptable value of¹³⁷Cs analysisprecision and higher value of the specific activity in all three soils compared to the sample of2.00mm.In the measurement of²¹⁰Pb, the decrease of sieve diameters would prolong the time to reach theacceptable value of analysis precision but show no significant effect on the value of the specific activity.These results have some important implications for enhancing the analysis precision of the specificactivity of¹³⁷Cs and²¹⁰Pb in soil samples by using HPGe γ Spectrometry.In this study, we show that the distance between the filter and the detector will influence themeasurement during the process of detecting the radionuclides in air filter, which was rarely studied byothers before. It was found that increasing the distance, when detecting radionuclides with low activity,will raise the inaccuracy of the measurement to the radionuclides activity. By combining the practicalmeasured value with the real value, and considering the result of assessment of measurement accuracy,we concluded that it is proper to set the distance between the filter and detector as6of8.5cm under thecondition of detecting radionuclides with high activity, while3cm for the ones with low activity.