Evaluation of an ionization chamber characteristics for 222Rn calibration

Area of Science:

• Metrology
• Radiological Physics
• Environmental Science

Background:

• Accurate calibration of radon monitors is crucial for environmental and health assessments.
• Ionization chambers (ICs) are essential tools for radiation measurement and calibration.
• Establishing reliable working standards for radon calibration is a key metrological challenge.

Purpose of the Study:

• To develop and validate novel calibration methods for an inner-through-type ionization chamber (IC).
• To establish the IC as a working standard for calibrating radon monitors at the National Metrology Institute of Japan.
• To evaluate the calibration factor (CF) and its uncertainty for the IC under different sampling conditions.

Main Methods:

• Utilized an inner-through-type ionization chamber (IC) as a primary standard.
• Developed novel methodologies for the precise calibration of the IC.
• Measured IC output current in the order of 10^-13 A.
• Evaluated calibration factors under both continuous gas flow and stationary gas-filled conditions within the IC.

Main Results:

• The calibration factor (CF) for the IC was determined to be (2.0 ± 0.2) × 10^16 Bq m^-3 A^-1.
• The expanded uncertainty (k=2) of the CF was rigorously evaluated.
• Calibration factors obtained under continuous gas flow and stationary gas-filled conditions were in agreement within the evaluated uncertainty.

Conclusions:

• The developed novel methods provide a reliable approach for calibrating ionization chambers for radon measurements.
• The evaluated calibration factor establishes the IC as a viable working standard for radon monitor calibration.
• The consistency of CFs across different sampling conditions validates the robustness of the calibration methodology.