Oxygen Redistribution in UO2 Due to a Temperature Gradient

Marchant, D. D.; Bowen, H. Kent

doi:10.1007/978-1-4684-3150-6_6

Cited by 2 publications

(1 citation statement)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Characterization of the fuel composition during burnup have been presented in numerous publications as summarized in (Olander, 1998, Walker, Rondinella, Papaioannou, Van Winckel, Goll and Manzel, 2005, Park, Yang and Park, 1997 and will not be reviewed in this document. The importance of the modeling of fuel oxygen transport under large composition and temperature gradients (Marchant and Bowen, 1975, Adamson, Aitken, Evans and Davies, 1975, Adamson and Carney, 1974, Evans, Aitken and Craig, 1969, Marin and Contamin, 1969, Janek and Timm, 1998, Lassmann, 1987, Olander, 1972, Matzke, 1987 is taken here for granted and the main focus is on describing the model formulation and implementation.…”

Section: Introductionmentioning

confidence: 99%

Depletion, Chemical Reaction and Transport in High Burnup Nuclear Fuel

Simunovic

Besmann

Moore

et al. 2019

View full text Add to dashboard Cite

We have developed a formulation and computational model for oxygen transport in Light Water Reactor (LWR) uranium dioxide fuel. The overall model couples the burnup simulation isotopic composition with a thermochemistry model of the fuel phase, and oxygen transport using the driving forces from the thermodynamic calculations. The diffused oxygen is accounted for in the thermochemistry model in order to establish consistent material and thermodynamic conditions in the fuel undergoing burnup. The model has been implemented in the nuclear fuel performance code Bison. The formulation and the model have been successfully demonstrated on fuel burnup data from the open literature. The developed capability enables consideration of complex chemical composition of irradiated fuels beyond available burnup models in Bison.

show abstract

Section: Introductionmentioning

confidence: 99%

Depletion, Chemical Reaction and Transport in High Burnup Nuclear Fuel

Simunovic

Besmann

Moore

et al. 2019

View full text Add to dashboard Cite

show abstract

Thermal Segregation of Cations in Iron Aluminate Spinels

Petuskey

Bowen

1981

Journal of the American Ceramic Society

View full text Add to dashboard Cite

The observation of crystalline grains of both Si2N20 and MgSiO, situated in the noncrystalline phase suggests that they crystallized from that phase. The principal pieces of evidence are the ill-defined shape of many of the Si2N20 grains, the fact that the grains are considerably smaller than the average size (= 1 p m ) of the grains away from the noncrystalline pockets, the spherulitic morphology of the MgSiO, grains (characteristic of the early stages of crystallization in glass ceramics6), and the fact that Si2N20 and MgSiO, have formed, whereas the phases in the same material prior to the rapidly cooling silicon nitride alloy were found (Part I) to be Si3N4, Si2N20, and MgzSi04. The formation of MgSiO, in the intergranular phase cannot be readily explained from phase equilibria considerations as only the subsolidus phase relations are known. However, it is possible that it forms as an intermediate phase during a crystallization sequence of the intergranular phase.The fact that the same elemental partitioning was detectable in the light and dark regions of the intergranular noncrystalline phase (see Fig. 2 of Part I) in the same alloy after hot-pressing, but without additional rapid cooling, indicates that phase separation can occur under normal fabrication conditions. As glasses in the SiO,-MgO miscibility gap can be crystallized by conventional glass-ceramic processes using a nucleating agent, it may be possible to take advantage of the observed phase separation to crystallize the intergranular phase in silicon nitride ceramics. IV. Conclusions(1) Phase separation in the noncrystalline phase (as evidenced by elemental partitioning and morphology) of a hot-pressed and rap-idly cooled silicon nitride was detected by high spatial resolution microanalysis techniques in the transmission electron microscope.(2) Small crystallites of SizN20 and MgSiO, are found in the noncrystalline phase. The presence of Si2N20 indicates the possibility that the noncrystalline phase once incorporated nitrogen. EELS measurements also indicate that the nitrogen content of the noncrystalline phase is probably <5 at.%.(3) The compositional range of the phase separation is determined to be close to the miscibility gap of the system SiOz-MgO and the presence of nitrogen could extend the gap into the Si2N20-Si02-MgSi0, ternary phase field.(4) The fact that noncrystalline regions having compositions similar to the two separated phases have also been detected in both the hot-pressed silicon nitride and the hot-pressed ternary eutectic composition (Part I) indicate that the intergranular phase in conventionally hot-pressed silicon nitrides containing MgO may also undergo phase separation under suitable circumstances.Thermal segregation experiments were performed on open and encapsulated wafers of Fe(Fel.slAlo.49)04 spinels using CO, laser radiation as a heat source. The correlation of "apparent" marker movement and cation segregation led to the conclusion that the free exchange of gaseous oxygen at the external spinel surfaces is necessary ...

show abstract

Oxygen Redistribution in UO2 Due to a Temperature Gradient

Cited by 2 publications

References 8 publications

Depletion, Chemical Reaction and Transport in High Burnup Nuclear Fuel

Depletion, Chemical Reaction and Transport in High Burnup Nuclear Fuel

Thermal Segregation of Cations in Iron Aluminate Spinels

Contact Info

Product

Resources

About