Thermodynamic and Thermophysical Properties of the Actinide Oxides

Guéneau, C.; Chartier, Alain; Brutzel, L. Van

doi:10.1016/b978-0-08-056033-5.00009-4

Cited by 40 publications

(45 citation statements)

References 221 publications

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“…More importantly, this difference seems to increase with the oxygen potential of the respective dioxide at a given temperature. 32 This shows the suitability of the current approach for the investigation of these materials, particularly in the cases where they display a strong tendency to exchange oxygen with their environment.…”

Section: Discussionmentioning

confidence: 99%

“…Data for the dioxides of protactinium and trans-plutonium actinides are missing or considered as unreliable. The difference between new and old data points increases with the atomic number of the actinide and the oxygen potential 32 of the corresponding dioxide. Data of the room temperature sublimation enthalpy DH sub (298) [33][34][35][36][37] for the actinide dioxide series are also reported for comparison.…”

Section: Figmentioning

confidence: 99%

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Revisiting the melting temperature of NpO2 and the challenges associated with high temperature actinide compound measurements

Böhler

Welland

Bruycker

et al. 2012

Journal of Applied Physics

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This work revisits the melting behaviour of neptunium dioxide, an actinide compound which can be produced in the nuclear fuel during operation, and which has an important impact on the nuclear fuel and waste radioactivity especially on the very long term. The present experimental approach employs remote laser heating under controlled atmosphere and fast pyrometry. This technique circumvents problems encountered by more traditional heating techniques, in particular, the reaction between sample and containment at temperatures beyond 2500 K. In addition, only a small amount of sample material is required, which is an advantage with respect to the radioactivity and limited availability of neptunium. The NpO 2 melting/freezing temperature has been measured to be 3070 K 6 62 K, much higher than previous values (around 2830 K) obtained by more traditional thermal analysis methods. The large amount of experimental data collected allowed a consistent statistical analysis. It seems likely, although not fully evident from the present results, that the high oxygen potential at temperatures around melting leads to a slightly hypo-stoichiometric congruent melting composition, as already observed in other actinide (ThO 2 , PuO 2 ) and lanthanide oxides (e.g., CeO 2 ). Finally, a recently developed phase-field model was used for the simulation of the observed thermograms, allowing a deeper insight in material properties that are difficult to directly measure. For example, a polaron contribution to the high-temperature thermal conductivity, well accepted for the commonly studied actinide oxide UO 2 , is shown here to likely be present in NpO 2 .

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Section: Discussionmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

Revisiting the melting temperature of NpO2 and the challenges associated with high temperature actinide compound measurements

Böhler

Welland

Bruycker

et al. 2012

Journal of Applied Physics

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“…Mixed actinide dioxides are a solid solution of the two dioxide end-members with a fluorite-like structure (fcc, Fm 3m) [1]. Thermal material properties of such systems seem to behave ideally at temperatures well below melting [1], which is shown, for example, for the (Pu, Th)O 2 solid solution with new heat capacity studies by Valu et al [2].…”

Section: Introductionmentioning

confidence: 94%

High temperature phase transition of mixed (PuO 2 + ThO 2 ) investigated by laser melting

Böhler

Cakir

Beneš

et al. 2015

The Journal of Chemical Thermodynamics

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a b s t r a c tA 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 (PuO 2 + ThO 2 ) at high temperature. At low concentration of ThO 2 in PuO 2 a minimum in the solidification temperature in the pseudo binary (PuO 2 + ThO 2 ) was observed. The minimum was found around a composition with 5 mol% ThO 2 . 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 PuO 2 , 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 hightemperature oxygen chemistry in this actinide oxide phase.

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“…Plutonium dioxide (PuO 2 ) is an important ingredient of a mixed oxide (MOX) fuel for fast breeder reactors, the physical, chemical, and mechanical properties of which are important for nuclear engineering [9][10][11]. Also, PuO 2 has long been the compound of choice for plutonium reuse, separation, and deposition in long-term repositories, due to its reliable stability with respect to oxidation [12].…”

Section: Introductionmentioning

confidence: 99%