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Title: Thermal conversion in air of rare-earth fluorides to rare-earth oxyfluorides and rare-earth oxides

Journal Article · · Journal of Nuclear Materials

Phase transformations of seven different rare-earth fluorides (i.e., REF3) where RE = La, Ce, Pr, Nd, Tm, Yb, Lu at temperatures ranging from 400–1400°C in air were investigated with X-ray diffraction. All of the REF3 compounds first transformed to oxyfluorides and then to oxides, with the exception of CeF3, which transformed directly to an oxide. This study focuses on the phase transitions of REF3 to REOx by simple heat-treatment processes in air and shows plausibility to remove RE elements from fluoride salt streams from molten salt reactors through fluoride-to-oxyfluoride or fluoride-to-oxide conversion mechanisms, which will result in precipitation. This could be used to remove fission product poisons from molten salt reactor waste streams. A waste form option for the resulting REOx products is lanthanide aluminoborosilicate (LABS) glass. To demonstrate this NdF3 was converted to Nd2O3 and immobilized in a LABS glass.

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
1872435
Report Number(s):
PNNL-SA-167547
Journal Information:
Journal of Nuclear Materials, Vol. 561
Country of Publication:
United States
Language:
English

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