Development of the absolute standardization apparatus for radon-222 activity

Area of Science:

• Nuclear physics
• Metrology
• Environmental radioactivity

Background:

• Accurate measurement of radon-222 activity is crucial for radiation protection and environmental monitoring.
• Existing methods may be limited by gas impurities and scattering effects.
• Development of a primary measurement standard is essential for reliable radon quantification.

Purpose of the Study:

• To develop and validate a defined solid angle counting apparatus for absolute radon-222 activity measurement.
• To minimize the impact of gas impurities on measurement accuracy.
• To quantify the uncertainty contributions from alpha particle scattering.

Main Methods:

• Utilized home-made vacuum-sealed radium-226 sources (500kBq and 3MBq) to reduce gas impurity effects.
• Calculated the defined solid angle using precisely measured geometrical parameters and multiple algorithms.
• Employed geant4 code for Monte Carlo simulation to model alpha particle scattering in the measurement chamber and collimator.

Main Results:

• Monte Carlo simulation results align with other calculation methods within uncertainty limits.
• Estimated a total scattering alpha particle ratio of 0.23%.
• Quantified the relative uncertainty contribution from scattering to be between 0.02% and 0.09%.

Conclusions:

• The developed defined solid angle counting apparatus provides a reliable method for primary radon-222 activity measurement.
• The apparatus achieves a typical total combined standard uncertainty of 0.28%.
• The study demonstrates effective mitigation of gas impurity impacts and quantification of scattering uncertainties.