Calibration of Tritium Monitors Using Saturated Vapour of Tritiated Water

An original method, based on the continuous circulation in a closed circuit of saturated HTO vapour, is presented. The saturated vapour are obtained by bubbling from vials containing different tritium standard solutions (IFIN-HH-TDCR method). The main difference from the usual method, elaborated by Osborne, is the use of saturated vapour, which eliminates the measurement in liquid scintillator of the recovered non-saturated vapour. Tritium Monitors type MT-1 made in IFIN-HH were calibrated. The measurements were carried out for three levels of the activity concentration: 0.0180, 0.701 and 1.73 MBq.g^-1. The mean response was R=2.25.10^-13 A/(MBq m^-3) with a relative combined uncertainty lower than 4%. The value agrees with the result obtained with the Osborne method, R_Os=2.30.10^-13A/(MBq m^-3) and with the estimated theoretical value, 2.29 10^-13A/(MBq m^-3)