Electret ion chamber-based passive radon-thoron discriminative monitors

Area of Science:

• Environmental Science
• Radiation Detection and Measurement
• Nuclear Physics

Background:

• Electret ion chambers (EICs), such as E-PERM(®), are standard for measuring indoor and outdoor radon-222 ((222)Rn) concentrations.
• Standard EICs are designed to exclude thoron-220 ((220)Rn) by limiting the entry area.
• Distinguishing between (222)Rn and (220)Rn is crucial for accurate environmental radiation assessment.

Purpose of the Study:

• To modify existing radon EIC (R EIC) monitors to also detect thoron-220 ((220)Rn).
• To develop a method for simultaneously measuring both (222)Rn and (220)Rn concentrations using collocated modified EICs.
• To compare the sensitivity and range of the modified EICs with existing passive discriminative monitors.

Main Methods:

• Modified EICs, termed RT EICs, were created by increasing the diffusional entry area to allow (220)Rn detection alongside (222)Rn.
• Collocation of standard R EICs and modified RT EICs enabled discrimination between the two isotopes.
• Calibration factors (CFs) and algorithms were developed for different EIC volumes (58, 210, and 960 ml) to quantify (222)Rn and (220)Rn concentrations.

Main Results:

• The study successfully demonstrated the capability of RT EICs to detect (220)Rn in addition to (222)Rn.
• Specific thoron calibration factors (CFs) were determined for 58-ml, 210-ml, and 960-ml R and RT EIC pairs.
• The modified EICs exhibit significantly wider sensitivities and measurement ranges compared to alpha track-based passive radon-thoron discriminative monitors.

Conclusions:

• Modified electret ion chambers (RT EICs) provide a viable method for simultaneous measurement of radon and thoron.
• The developed technique offers enhanced sensitivity and range for environmental radioactivity monitoring.
• This approach improves upon existing methods for discriminating and quantifying radon and thoron concentrations.