Source Thickness Measurements and Evaluation of Their Uncertainty for The U8 Type Cylindrical Shaped Radionuclide Reference Sources

• Published in: BUNSEKI KAGAKU Vol. 69; no. 10.11; pp. 627 - 637
• Main Authors: YONEZAWA, Chushiro, YAMAGUCHI, Kosaku, ARAKAWA, Fumihiro, MOCHIZUKI, Gaku, MIYAZAWA, Megumi
• Format: Journal Article
• Language: English
• Published: The Japan Society for Analytical Chemistry 05.10.2020
• Subjects: cylindrical shape; gamma-ray peak efficiency; radionuclide reference source; source thickness; uncertainty evaluation
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.69.627

A method for both the measurement of the source thickness and for evaluating its uncertainty of the U8 type cylindrical shaped radionuclide reference sources used for peak efficiency calibration of a gamma-ray spectrometer has been established. Essential information to measure the source thickness such as the height of the base level and a width of stopper for cover of the U8 container were clarified by measuring detailed dimensions of the 20 empty containers. The measurement of the source thickness and evaluating of its uncertainty were examined using dummy sources prepared with same materials as the reference sources. The examination clarified that: i) a vernier caliper is suitable for the thickness measurement due to its precision and utility; ii) the source thickness should be obtained by subtracting the mean height of the source measured at 4 places corresponding to the quartered bottom with the height of the base level for thickness measurement; iii) the standard uncertainty of the source thickness for 5 mm to 40 mm is found to be 0.4 mm; iv) the source thickness and its standard uncertainty of the reference source so called as “50 mm height”, which is unable to measure the thickness directly, are estimated to be 50. 7 mm and 0.7 mm, respectively. The peak efficiency of a gamma-ray spectrometer with a Ge detector was calibrated using the reference sources and was evaluated the uncertainty. The relative standard uncertainty of gamma-ray peak efficiencies for analyte nuclides such as 131I, 134Cs, 137Cs and 40K corresponding to source thickness were found to be 0.63 % to 1.0 %.