Simultaneous immobilization of cesium and strontium by crystalline zirconium phosphate

Abstract

In the present study, simultaneous gross immobilization of radioactive Cs and Sr in zirconium phosphate was investigated by two methods. In the “dry method,” a mixture of HZr₂(PO₄)₃ with varying amounts of CsNO₃ and Sr(NO₃)₂ was heat-treated at 700 °C for 5 h to prepare Cs + Sr immobilized samples. At Cs + Sr immobilization of 0.3 + 0.15, the leaching amounts of Cs and Sr in 1 mol·dm⁻³ of HCl solution treated at 160 °C for 24 h were 2.9 × 10⁻⁴ g·m⁻² and 3.9 × 10⁻⁴ g·m⁻², respectively. In the “autoclave method,” aqueous solutions containing 0.5 and 0.25 mol of CsNO₃ and Sr(NO₃)₂, respectively, against 1 mol of (H₃O)Zr₂(PO₄)₃ were thermal-treated at 150–250 °C for 24 h to prepare Cs + Sr immobilized samples; immobilization of Cs and Sr was observed at 150 °C. The immobilized amount of Cs and Sr increased as the treated temperature increased, while the leaching amounts of Cs and Sr in 1 mol·dm⁻³ of HCl solution treated at 160 °C for 24 h decreased. The amount of immobilized Cs and Sr on (H₃O)Zr₂(PO₄)₃ at 250 °C were 0.30 and 0.20, and leaching amounts of Cs and Sr were 1.0 × 10⁻³ g·m⁻² and 1.4 × 10⁻³ g·m⁻², respectively.