Calibration system for radon EEC measurements

Radon Equilibrium Equivalent Concentration Uncertainty of Calibration System With Alpha Self-Absorption Consideration

The measurement of radon decay products level in dwellings or working places separately is not preferable. The estimation of radon equivalent equilibrium concentration (EECRn) is more simple and quick technique. In this work, the uncertainty of calibration system for EECRn measurements will present and the reduction will be suggesting. The calibration system for EECRn measurements was presented and described in previous work with gamma spectrometer as a reference measuring device. The influence of alpha particles absorption in filters materials and filter efficiency taken into account. The measurements of EECRn by gamma spectrometry and improved alpha radiometry are in good agreement and the systematic shift between average values is observed and resolved. The total standard uncertainty of EECRn measurements with gamma spectroscopy is 3.8%. About 71% of this total uncertainty value is related to the uncertainty of the count rate at full absorption peak with gamma spectroscopy. If the time between the end of sampling and gamma spectroscopy measurements reduced to 2000s not 4000 s, this value will reduce to 1.6% and the total standard uncertainty of EECRn will be 2.6%.

Radon decay products equilibrium at different aerosol concentrations

The influence of aerosol particle concentration on the activity of short-lived radon decay products (RPDs) was investigated inside a standard radon box. The ²¹⁸Po:²¹⁴Pb:²¹⁴Bi activity ratio was determined for unattached and attached fractions of radon decay products at different aerosol concentrations. For the unattached fraction, this ratio was 1:0.31:0.06, while for the attached aerosol fraction the activity ratio was 1:1.4:0.91 at a low aerosol concentration (2000 cm^-3) and with the unattached fraction f_p = 0.45. In this case, there was no additional aerosol in the standard radon box and the equilibrium shift ratio for the total activity (attached and unattached) was 1:0.55:0.27 for ²¹⁸Po:²¹⁴Pb:²¹⁴Bi. When the aerosol was injected, the unattached fraction nearly disappeared at a high aerosol concentration (80000-90000 cm^-3). The equilibrium shift ratio for the total activity at a high aerosol concentration was 1:2:1.5 for ²¹⁸Po:²¹⁴Pb:²¹⁴Bi. This ratio was the same for the attached fraction. For no more than 0.01 of the unattached fractions, this ratio was 1:0.85:0.7. Radioactive equilibrium factors and unattached fractions were also determined at different aerosol particles concentrations. A negative correlation between unattached fraction and the radioactive equilibrium factor, as well as a positive correlation coefficient between the radioactive equilibrium factor and aerosol particle concentration in a standard radon box, has been determined.