High temperature phase transition of mixed (PuO2 + ThO2) investigated by laser melting. (February 2015)

• Record Type: Journal Article
• Authors: Böhler, R.; Çakır, P.; Beneš, O.; Hein, H.; Konings, R.J.M.; Manara, D.
• Is Part Of: Journal of chemical thermodynamics. Volume 81(2015:Feb.)
• Page Start: 245
• Page End: 252
• Publication Date: 2015-02
• Subjects: Actinide alloys and compounds -- Phase transitions -- Phase diagrams -- (Thorium + plutonium) dioxide; Thermodynamics -- Periodicals; Thermochemistry -- Periodicals; Thermodynamique -- Périodiques; Thermochimie -- Périodiques; Thermochemistry; Thermodynamics; Periodicals; 541.369
• DOI: 10.1016/j.jct.2014.10.006
• Languages: English
• ISSNs: 0021-9614

Abstract

Graphical abstract: Highlights: Melting of mixed (Pu + Th) dioxides was studied by laser heating. A minimum melting point was found around 5 mol% ThO2 . Ideal solution behaviour near melting was observed for compositions richer in ThO2 . Raman spectroscopy reveals peaks (>2000 cm −1 ) linked to the PuO2 content. Abstract: A laser heating approach combined with fast pyrometry in a thermal arrest method was used to provide new data for the melting/solidification phase transition in mixed (PuO2 + ThO2 ) at high temperature. At low concentration of ThO2 in PuO2 a minimum in the solidification temperature in the pseudo binary (PuO2 + ThO2 ) was observed. The minimum was found around a composition with 5 mol% ThO2 . Phase transition temperatures of other compositions are closer to an ideal solution behaviour. To detect changes in the material a complete investigation with electron microscopy, Raman spectroscopy and powder X-ray diffraction was done. Raman vibration modes were found, that are characteristic for materials containing PuO2, and high temperature segregation effects during solidification were described. The results obtained in the present work are compared to other mixed actinide dioxides and compared to the ideal solution case for this system. The presented results show the importance of the high-temperature oxygen chemistry in this actinide oxide phase.