Development of liquid scintillation based 4πβ(LS)-γ coincidence counting system and demonstration of its performance by standardization of 60Co

A single-vial, single-PMT 4πβ(LS)-γ coincidence counting system has been developed at the Radiation Safety Systems Division, BARC. It has advantages of simple sample preparation, higher counting efficiency and the absence of self absorption over the conventional proportional counter based 4πβ(PC)-γ coincidence counting system. The performance of the system is demonstrated by standardizing a 60Co solution using the 4πβ(LS)-γ coincidence counting system, 4πβ(PC)-γ coincidence counting system and CIEMAT/NIST method and comparing the results obtained by each method. The detection efficiency of liquid scintillation counter of the 4πβ(LS)-γ coincidence counting system was varied by color quenching, by chemical quenching and by varying the bias voltage applied to the LSC PMT. For the proportional counter based 4πβ(PC)-γ coincidence counting system the detection efficiency was varied by source self absorption. The activity concentrations obtained using the 4πβ(LS)-γ coincidence counting system, the 4πβ(PC)-γ coincidence counting system and the CIEMAT/NIST method are comparable within the uncertainty limits. - Highlights: ► A 4πβ(LS)-γ coincidence counting system has been developed in the laboratory. ► The performance of the system is demonstrated by standardizing a 60Co solution. ► Three methods viz. 4πβ(LS)-γ, 4πβ(PC)-γ coincidence counting system, and CIEMAT/NIST method are used. ► The activity concentrations obtained by different methods are comparable within uncertainty limits.