Kr-81m calibration factor for the npl ionisation chamber.

Area of Science:

• Nuclear physics and radiochemistry
• Medical physics and instrumentation

Background:

• 81mKr is a short-lived radionuclide (13.1s half-life) requiring specialized measurement techniques.
• Its parent, 81Rb, has a longer half-life (4.6h), necessitating elution for use.
• Accurate activity concentration measurement is crucial for its applications.

Purpose of the Study:

• To develop and validate a general method for measuring the activity concentration of 81mKr gas.
• To establish a reliable calibration procedure for 81mKr using standard laboratory equipment.
• To ensure accurate quantification of 81mKr for research and clinical applications.

Main Methods:

• Two-step calibration process: gamma-ray spectrometer calibration using 51Cr and 139Ce sources.
• Calibration of an NPL radionuclide calibrator using a custom ionization chamber insert with 81mKr gas flow.
• Utilized PTFE tubing for gas transfer, maintaining consistent measurement geometry.

Main Results:

• Gamma-ray spectrometer calibrated with sources bracketing 81mKr's energy (190.5 keV).
• Determined a calibration factor for the radionuclide calibrator, independent of gas flow rate within specified limits.
• Validated the measurement geometry for accurate activity concentration determination.

Conclusions:

• A robust method for 81mKr activity concentration measurement has been established.
• The developed calibration procedure provides reliable quantification of this short-lived radionuclide.
• The method's independence from gas flow rate enhances its practical utility.