The absolute counting of 125I

Area of Science:

• Nuclear physics
• Metrology
• Radiochemistry

Background:

• The Institute of Nuclear Energy Research (INER) participated in an international activity comparison.
• This comparison focused on standardizing the activity of Iodine-125 (125I).
• Collaborated with the Electrotechnical Laboratory (ETL) in Japan and other Asia Pacific laboratories.

Purpose of the Study:

• To standardize the activity of Iodine-125 (125I) using two distinct measurement methodologies.
• To validate INER's measurement techniques against international standards and regional comparisons.
• To contribute to the accuracy and reliability of radioactivity measurements in the Asia Pacific region.

Main Methods:

• Employed sum-peak coincidence counting with two 76 x 76 mm NaI(Tl) detectors.
• Utilized 4π-X coincidence counting technique with efficiency extrapolation.
• Participated in a regional activity comparison alongside BIPM (International Bureau of Weights and Measures) measurements.

Main Results:

• The two developed methods at INER yielded results with a 2.6% difference.
• INER's standardized activity values for 125I demonstrated agreement with the regional comparison results.
• INER's findings were consistent with the measurements from the BIPM's International System of Units (SIR) database.

Conclusions:

• The sum-peak and 4π-X coincidence counting methods are reliable for Iodine-125 standardization.
• INER's radioactivity measurement capabilities are validated through international intercomparisons.
• This study reinforces the accuracy of radioactivity metrology in the Asia Pacific region.