Change of Calibration Parameters in Frequently Used Vials in Benzene Scintillation Counting

Abstract

Scintillation counting vials used for counting synthesized benzene accumulate an inside coating which is insoluble in benzene. This coating reduces the photon transfer from the vial and lowers its observed background. Age calculations that include calibration data collected with other vials may be inaccurate if this effect is not considered. Frequent cleaning of the counting vials with strong acid solutions keeps the coating from accumulating. A sample counting vial cleaned only with photospectrometric grade benzene between 67 different sample benzene fillings made in a 20-month period showed, during counting, an efficiency lowered by 2.8% and a background lowered by 8.7%. Age calculations for a 10 ka old sample made with calibration data from "matched" vials would yield a result too old by 515 yr.