An experimental study on Sodalite and SAP matrices for immobilization of spent chloride salt waste

• Published in: Journal of nuclear materials Vol. 499; pp. 512 - 527
• Main Authors: Giacobbo, Francesca, Da Ros, Mirko, Macerata, Elena, Mariani, Mario, Giola, Marco, De Angelis, Giorgio, Capone, Mauro, Fedeli, Carlo
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-02-2018; Elsevier BV
• Subjects: Borosilicate glass; Ceramic wasteforms; Chemical synthesis; Chloride salt waste; Chlorides; Comparative studies; Confining; Frit; Immobilization; Leaching; Leaching tests; Nuclear fuel cycle; Nuclear fuel elements; Nuclear fuels; Nuclear reactors; Plutonium; Pyro-processing; Retention; Salts; SAP; Sodalite; Spent nuclear fuels; Uranium; Vitrification; SAP; Sodalite; Leaching tests; Pyro-processing; Ceramic wasteforms; Nuclear fuel cycle; Chloride salt waste
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2017.11.051

In the frame of Generation IV reactors a renewed interest in pyro-processing of spent nuclear fuel is underway. Molten chloride salt waste arising from the recovering of uranium and plutonium through pyro-processing is one of the problematic wastes for direct application of vitrification or ceramization. In this work, Sodalite and SAP have been evaluated and compared as potential matrices for confinement of spent chloride salt waste coming from pyro-processing. To this aim Sodalite and SAP were synthesized both in pure form and mixed with different glass matrices, i.e. commercially available glass frit and borosilicate glass. The confining matrices were loaded with mixed chloride salts to study their retention capacities with respect to the elements of interest. The matrices were characterized and leached for contact times up to 150 days at room temperature and at 90 °C. SEM analyses were also performed in order to compare the matrix surface before and after leaching. Leaching results are discussed and compared in terms of normalized releases with similar results reported in literature. According to this comparative study the SAP matrix with glass frit binder resulted in the best matrix among the ones studied, with respect to retention capacities for both matrix and spent fuel elements.
•Sodalite and SAP were evaluated as confining matrices for chloride salt waste.•Addition of glass frit enhances the matrix retention capability.•SAP matrix blended with glass frit exhibited the best confining performances.•Sodalite and SAP with glass frit are comparable with similar matrices in the literature.•SAP process produces a little amount of secondary active waste containing Cl-36.