Determination of 41Ca in biological-shield concrete by low-energy X-ray spectrometry.

An X-ray spectrometric method has been developed for the determination of 41Ca in the biological-shield concrete of nuclear reactors. The concrete sample was first decomposed with nitric, hydrofluoric, and perchloric acids. Calcium was then separated from other radionuclides by ion-exchange chromatography and recovered as an oxalate precipitate. X-rays at 3.3 keV from 41Ca in the calcium oxalate pellet were measured. The detection efficiency of the X-ray measurement at 3.3 keV was calculated from those obtained by measuring 55Fe standard pellets at 5.9 keV using mass-absorption coefficients of the calcium oxalate pellet at each X-ray energy. A lower limit of determination of 8 Bq g(-1) was obtained for a sample weight of 1 g.