High-Temperature Phase Transformations in Some Lanthanide and Actinide Oxides.

Chikalla, T.D.; McNeilly, C.E.; Bates, J.L.; Rasmussen, J. J.

doi:10.2172/4723115

Cited by 6 publications

(6 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the general trend of the entire actinide dioxide series, reported in Figure 8, 3,5,7,[28][29][30][31] changes considerably when new values for NpO 2 and PuO 2 are taken into account instead of old ones. Figure 8 also shows that the difference between old and new melting temperatures of actinide dioxides increases with the atomic number of the actinide.…”

Section: Discussionmentioning

confidence: 99%

“…Comparison between old (induction furnace heating in a tungsten crucible) 3,[29][30][31] and new (quasi-containerless laser heating) 5,7,28 data points for the melting/solidification temperatures of dioxides of the actinide series. Data for the dioxides of protactinium and trans-plutonium actinides are missing or considered as unreliable.…”

Section: Figmentioning

confidence: 99%

“…Two melting point measurements of NpO 2 were published prior to the present work by Chikalla et al 3 …”

mentioning

confidence: 99%

See 2 more Smart Citations

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

View full text Add to dashboard Cite

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 .

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

show abstract

“…The decay mechanism predominantly.involves a 114 I(eV beta, introducing californium-249 ( t = 360 yrs) a t the r a t e of about l.S%/week. I/ 2 Since only milligram samples of this element were available and the weight l o s s f o r a Bk02 -t BkOle5 decomposition is 34.2 pg per milligram of BLQ2, balance techniques were ruled out and tlle capacitance manometer systex was developed as described e a r l i e r . The 1 .…”

Section: Bkomentioning

confidence: 99%

“…. (x = 1.500 and x = 2.000), the behavior through the series is more regular, and phase relations (polymorphism) in the sesquioxide are now well documented f o r both 1 ' the actinide and 1anthani.de series [1,2].…”

Section: Introductionmentioning

confidence: 99%