Standardisation of 133Ba by efficiency extrapolation method and calibration of ionisation chamber

Abstract

133Ba has been standardised by direct measurements for the first time in the laboratory using two counting systems: (i) the 4πβ (plastic scintillator) -γ coincidence, (ii) the 4πβ (proportional counter) -γ coincidence. Furthermore, this standardisation experiment demonstrates the performance and applicability of the recently developed 4πβ (plastic scintillator)-γ coincidence system for radionuclides decaying with complex decay schemes as well as for e, X-γ emitters. Additionally, 133Ba solution standards were prepared to calibrate the pressurized 4π γ ionisation chamber and determination of the calibration coefficient. The En score is a statistical indicator of the agreement between two independent estimations. Thus, the performance of the PS system was compared to the result obtained with the PC system using the En score as specified in the ISO13528:2015. The results of measurements are acceptable if En ≦ 1.0. An En score of 0.2 was obtained which indicates that, the 133Ba activity concentration obtained by the 4πβ (plastic scintillator) -γ coincidence and 4πβ (proportional counter) -γ coincidence systems are in agreement. This paper presents the standardisation procedure, the results obtained by the measurements and their comparison.