A humidity resistant radon source developed by ion exchange of radium in a membrane

Objective

To develop a humidity resistant radon source on a membrane based on the ion exchange technique.

Methods

²²⁶Ra in its standard solution was adsorbed in the HP membrane through cation exchange. The radioactivity of ²²⁶Ra in the membrane was determined through the measurements of ²²⁶Ra activities in the solution before and after the adsorption using a HPGe γ spectrometer. The emanation coefficients of radon from the membrane in different humidity conditions were quantified through the measurements of radon concentrations in a close loop mode using the AlphaGUARD DF2000 radon monitor. Long-term measurements of radon concentrations in the close loop and a standard chamber using the membrane as radon source were performed to verify the stability of radon emanation from the source.

Results

A piece (70 ​mm ​× ​20 ​mm) of the HP membrane could adsorb 51.2 kBq of ²²⁶Ra in about 30 ​min. The emanation coefficient of radon from the membrane could reach as high as 0.997, and it was hardly changed in a humidity range from 7.5% RH to 94.5 ​% RH. The variation of the radon production rate from the source was only ±1.2 ​% in two weeks at a general laboratory condition, and its emanation stability was also confirmed in a standard radon chamber by using the membrane source for one month.

Conclusion

The radon membrane source developed in this study has a stable emanation coefficient regardless the environmental humidity. It can be used as a flow-through radon source in a standard radon chamber.