The perovskite mineral structure, ABX3, has drawn attention for the incorporation of actinides into a durable nuclear waste form, primarily as a component of SYNROC, a leading technology in the disposal of actinides. Defect perovskites, which follow the chemical formula A2BX6, have primarily drawn the attention of the photovoltaic community as a hole-transport material. However, defect perovskites are capable of high (up to 66 wt %) halogen mass loadings, notably Cl and I, which represent serious challenges in the disposal and reprocessing of spent nuclear fuel. Cs2SnCl6, a defect perovskite molecular salt which displays air stability and water insolubility, is highly attractive for nuclear waste disposal due to a combination of a high mass loading of both Cs (44.6 wt %) and Cl (35.6 wt %), as well as thermal stability above 600 oC. Through spark plasma sintering (SPS), a field assisted sintering technique (FAST), Cs2SnCl6 powders were consolidated into a fully dense (≥ 94% t.d.) pellet without any decomposition occurring. This enabled the preservation of the water insoluble phase, and the retention of the volatile chlorine and cesium after consolidation. Other defect perovskite compositions are being researched for nuclear waste applications, including Cs2SnI6 for the disposal of 129I, and K2SnCl6 for the disposal of pyroprocessing waste.

Defect perovskites for the sequestration of volatile nuclear waste

254th National Meeting (2017)

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