Synthesis and characterization of cerium monazite phosphate glass-ceramic for immobilization of nuclear waste salt

A phosphate glass-ceramic wasteform incorporating cerium monazite was synthesized through a two-step solid phase sintering methodology, aimed at immobilizing waste salts derived from the pyrochemical reprocessing of spent nuclear fuel. The initial phase involved the synthesis of cerium monazite powder, employing a stoichiometric mixture of CeF3 and NH4H2PO4 in a molar ratio of mol(Ce:PO4) = 1:1.4, which was subjected to a thermal treatment at 900 degrees C. Subsequently, the glass-ceramic matrix was fabricated by sintering a composite mixture of the synthesized cerium monazite and iron phosphate glass (IPG) powder at a temperature of 1000 degrees C for a duration of 2 h, resulting in a cerium incorporation exceeding 36.5 wt%. Microstructural analysis and structural characterization of the glass-ceramic sample elucidated the presence of monazite crystallites (CePO4) with dimensions ranging from .2 to 5.5 mu m. The chemical durability of the wasteform was assessed through modified ASTM C1308 tests conducted in deionized water over a period of 28 days, revealing a total elemental leaching rate of 2.58 x 10-7 g m-2 min-1.