Immobilization of cesium and iodine into Cs3Bi2I9 perovskite-silica composites and core-shell waste forms with high waste loadings and chemical durability

Kun Yang; Weiguang Zhu; Spencer Scott; Yachun Wang; Jianwei Wang; Brian J Riley; John Vienna; Jie Lian

doi:10.1016/j.jhazmat.2020.123279

Immobilization of cesium and iodine into Cs₃Bi₂I₉ perovskite-silica composites and core-shell waste forms with high waste loadings and chemical durability

J Hazard Mater. 2021 Jan 5:401:123279. doi: 10.1016/j.jhazmat.2020.123279. Epub 2020 Jun 22.

Authors

Kun Yang¹, Weiguang Zhu¹, Spencer Scott², Yachun Wang¹, Jianwei Wang³, Brian J Riley⁴, John Vienna⁴, Jie Lian⁵

Affiliations

¹ Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, NY 12180, United States.
² Savannah River National Laboratory, Aiken, SC 29801, United States.
³ Department of Geology and Geophysics, Louisiana State University, LA 70803, United States.
⁴ Pacific Northwest National Laboratory, Richland, WA 99354, United States.
⁵ Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, NY 12180, United States. Electronic address: LIANJ@rpi.edu.

PMID: 32629351
DOI: 10.1016/j.jhazmat.2020.123279

Abstract

Cs₃Bi₂I₉, a defect perovskite derivative, is a potential host phase to immobilize iodine and cesium with high waste loadings. In this work, two strategies were explored to form Cs₃Bi₂I₉-silica composites and a core-shell structure in order to improve chemical durability of waste form materials meanwhile maintaining high waste loadings. Cs₃Bi₂I₉ loadings as high as 70 wt.% were incorporated into a silica matrix to form silica-ceramic composites, and 20 wt.% Cs₃Bi₂I₉ was encapsulated into silica to form a core-shell structure by low temperature spark plasma sintering. Chemical durability of the composite and core-shell waste forms was evaluated by semi-dynamic leaching experiments, and Cs and I were incongruently released from waste form matrices. A BiOI alteration layer formed, acting as a passivation layer to reduce the release of radionuclides. The long-term iodine release rate was low (30 mg m^-2 day^-1) for the 70 wt.% Cs₃Bi₂I₉-silica composite leached in deionized water at 90 °C, which can be further reduced to 5 × 10^-3 mg m^-2 day^-1 for the 20 wt.% core-shell structure. This work highlights a robust way to immobilize the highly mobile radionuclides with high waste loadings through encapsulation into durable matrices and a surface passivating mechanism that can greatly reduce the elemental transport from waste form materials and significantly enhance their chemical durability.

Keywords: Fission product; Pervoskite; Silica; Sparking plasma sintering; Waste form.