Analytical method for determination of 41Ca in radioactive concrete

Abstract The analysis of 41Ca in concrete generated from the nuclear facilities decommissioning is critical for ensuring the safe management of radioactive waste. An analytical method for the determination of 41Ca in concrete is described. 41Ca is a neutron-activated long radionuclide, and hence, for accurate analysis, it is necessary to completely extract Ca from the concrete sample where it exists as the predominant element. The decomposition methods employed were the acid leaching, microwave digestion, and alkali fusion. A comparison of the results indicated that the alkali fusion is the most suitable way for the separation of Ca from the concrete sample. Several processes of hydroxide and carbonate precipitation were employed to separate 41Ca from interferences. The method relies on the differences in the solubility of the generated products. The behavior of Ca and the interfering elements such as Fe, Ni, Co, Eu, Ba, and Sr is examined at each separation step. The purified 41Ca was measured by a liquid scintillation counter, and the quench curve and counting efficiency were determined by using a certified reference material of known 41Ca activity. The recoveries in this study ranged from 56 to 68%, and the minimum detectable activity was 50 mBq g−1 with 0.5 g of concrete sample.