Environmentally benign and novel management route for radioactive corrosion products by hydroxyapatite

Abstract

A novel and environmentally benign route for the direct solidification of captured corrosion products (Co, Cr, Fe, Ni, Cu, Zn, and Mn) generated from the primary coolant system of nuclear power plants is introduced in this study. Synthesized calcium hydroxyapatite was used to remove individual and mixtures of corrosion products from aqueous solutions. The results show more than a 95% removal of these corrosion products for both cases. The direct solidification of adsorbed corrosion products was done by pressure-less conventional sintering. The sintered matrix revealed a good hardness (3.70 +/- 0.60 GPa) and a relative sintered density > 98% after heat treatment at 1150 degrees C. The measured compressive strength (207.3 +/- 9.5 MPa) was significantly higher than the established waste immobilization criteria of the US (3.5 MPa) and Russia (4.9 MPa). The corrosion products consolidated matrix had a normalized leaching rate ranging from 3.4 x 10(-2) to 3.1 x 10(-6) g/m(2)/day. Moreover, no additional chemical treatments, additives (gypsum, slaked lime, sodium silicate, etc.), and sophisticated equipment were needed for the adsorption and solidification process. Therefore, the proposed waste management route has no adverse effects on the ecosystem and can be highly efficient to immobilize adsorbed waste and to reduce the secondary waste volume. (C) 2018 Elsevier B.V. All rights reserved.