MEASUREMENT OF THE POTENTIAL ALPHA ENERGY CONCENTRATION OF RADON PROGENY BY USING LIQUID SCINTILLATION COUNTING METHOD.

For more accurate measurement of the potential alpha energy concentration (PAEC) of radon progeny by the liquid scintillation counting (LSC) method, its counting efficiency was studied in this work. A radon progeny standard source was used to provide different concentrations of radon progeny, and the progeny collected on the sampling filters were measured with a low background liquid scintillation counter. The result showed that the quenching effect could not be ignored, and the counting efficiency was estimated to be 86.12%. The co-comparison experiments showed that the PAECs of radon progeny measured by the LSC methods were in generally consistent with those of other three methods. It indicates that for more accurate measurements of PAEC of radon progeny by using the LSC method, the counting efficiency should be well determined.

Controlling 212Bi to 212Pb activity concentration ratio in thoron chambers.

It is necessary to establish a reference atmosphere in a thoron chamber containing various ratios of 212Bi to 212Pb activity concentrations (C(212Bi)/C(212Pb)) to simulate typical environmental conditions (e.g., indoor or underground atmospheres). In this study, a novel method was developed for establishing and controlling C(212Bi)/C(212Pb) in a thoron chamber system based on an aging chamber and air recirculation loops which alter the ventilation rate. The effects of main factors on the C(212Bi)/C(212Pb) were explored, and a steady-state theoretical model was derived to calculate the ratio. The results show that the C(212Bi)/C(212Pb) inside the chamber is mainly dependent on ventilation rate. Ratios ranging from 0.33 to 0.83 are available under various ventilation. The stability coefficient of the ratios is better than 7%. The experimental results are close to the theoretical calculated results, which indicates that the model can serve as a guideline for the quantitative control of C(212Bi)/C(212Pb).