Immobilize fission product Cs by natural biotite hornblende monzonite

High-level radioactive waste (HLW) Cs is characterized by high fission yield, strong beta and gamma radioactivity, and strong migration activity, which needs to be properly immobilized. Given the thermal influence on volatile Cs, we tentatively prepared natural biotite hornblende monzonite glass to immobilize the simulated nuclear waste CsNO 3 under lowered temperatures. A suite of characterization techniques was employed to analyze the thermal effect, phase evolution, microstructure, micromorphology, and elemental distribution of the prepared waste forms. Moreover, the service performance of the waste forms, including density, hardness, and chemical durability were evaluated. The results indicate that the biotite hornblende monzonite glass powder can incorporate up to 50 wt.% of CsNO 3 , with Cs being immobilized both in the aluminosilicate glass network and the CsAlSi 2 O 6 crystalline lattice. The glass-ceramic composite enhances the Cs retention rate (98.32%) and reduces its leaching rate (∼10 −4 g m −2 day −1 ). This method addresses key challenges in HLW management, especially in dealing with high-yield fission products of low melting and high mobility.