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

Ito, Mitsuo; Watanabe, Kazuo; Hatakeyama, Mutsuo; Tachibana, Mitsuo

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