Standardization of ²⁴³Am by Efficiency Extrapolation Method

²⁴³Am is a very important nuclide as a chemical yield tracer for the radiochemical determination of ²⁴¹Am in environmental, food and other samples. For the study of absolute activity measurement of ²⁴³Am samples, efficiency extrapolation method by 4πα,β(PC)-γ(NaI(TI)) counting system is introduced in this paper. A solution containing ²⁴³Am in equilibrium with its daughter ²³⁹Np was standardized by this coincidence system, and the activity concentration of ²⁴³Am was just half of the gross activity concentration based on the theory of radioactivity equilibrium. In the experiment, the efficiencies of ²⁴³Am and ²³⁹Np were changed by altering the applied HV step by step, and the gross activity was obtained while the total efficiency of α and β was extrapolated to 100%. The final result for the efficiency extrapolation method is 5116.1(1±0.89%) Bq/g, which is the mean of the results obtained for the eight VYNS sources. As comparison, the result for ionization chamber is 5141.2(1±0.39%)Bq/g which is the mean of the results obtained for the six glass sources. The results show that there is good consistency between both methods adopted, and the agreement between results by both expereiments was 0.49%. The reference time is January 1 2012 0h.