U–Mo/Al–Si interaction: Influence of Si concentration

Allenou, Jérôme; Palancher, H.; Iltis, X.; Cornen, M.; Tougait, Olivier; Tucoulou, R.; Welcomme, E.; Martin, Philippe; Valot, C.; Charollais, F.; Anselmet, Marie-Christine; Lemoine, P.

doi:10.1016/j.jnucmat.2010.01.018

Cited by 30 publications

(25 citation statements)

References 9 publications

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“…Of more importance, perhaps, is that the phases present in the layered ILs change with Si content of the matrix. Allenou et al 6 noted this, showing there were no Si-bearing phases next to the fuel if the Si content was less than 5 wt% (see more detail below when phase content is discussed).…”

Section: Mo and Si Contentmentioning

confidence: 96%

“…With XRD, Mirandou identified the four compounds: (1) (U,Mo)Al 3 , (2) (U,Mo)Al 4 , (3) UMo 2 Al 20 , and (4) U 6 Mo 4 Al 43 . 16 Following this work, both Allenou 5 and Palancher 24 used µXRD for verification. The results of both studies establish the presence of these four phases, except Allenou does not observe UAl 4 and instead mentions the presence of U 3 (Al,Si) 5 because the study involved the addition of Si to the system.…”

Section: Phase Identificationmentioning

confidence: 97%

“…Allenou et al 6 has recently reviewed data from 450C diffusion couple experiments and showed evidence for microstructure and phase composition differences that perhaps helps explain the differences exhibited by fuels with high and low Si matrix compositions. With higher Si, the layers are thinner, with a highly Si-enriched sub-layer near the fuel and no Si-free complex phases.…”

Section: Mo and Si Contentmentioning

confidence: 99%

“…7 However, as co-author with Allenou in a paper that further examines the earlier results, Cornen mentions the observation of three layers. 5 Allenou determined that three layers exist based on a study conducted at 450°C, and the composition and thickness of those layers are influenced by the amount of Si present in the system. This study presented results for two types of couples: those with Si content between 2 and 5 wt% and those with greater than 5 wt% Si.…”

Section: Multi-layered Ilmentioning

confidence: 99%

“…This study presented results for two types of couples: those with Si content between 2 and 5 wt% and those with greater than 5 wt% Si. The most recent reference from Allenou et al 6 states that 450C treatments produce bi-layers regardless of Si content, but the phases present are different if the matrix Si content is above or below 5 wt%. Mazaudier speculated on the phase make-up of the three layers seen in that study, 14 but they are different from those presented originally by Allenou.…”

Section: Multi-layered Ilmentioning

confidence: 99%

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Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

Porter¹

2010

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SUMMARYPublished data concerning the interaction layer (IL) formed between U-xMo fuel alloy and aluminum (Al)-based matrix or cladding materials was reviewed, including the effects of silicon (Si) content in the matrix/cladding, molybdenum (Mo) content in the fuel, pre-irradiation thermal treatments, irradiation, and test temperature. The review revealed that tests conducted in the laboratory produce results different from those conducted in an irradiation environment. However, the laboratory testing relates well to thermal treatments performed prior to irradiation and helps in understanding the effects that these pre-irradiation treatments have on in-reactor performance. A small, Si-enriched IL, formed during a step in the fabrication process, seems to be stable during irradiation, helping to prevent the rapid growth of an irradiation-induced IL. Moreover, the Si-enriched IL seems to be important in delaying the onset of rapid growth of fission gas bubbles.Conclusions from irradiated fuels data have been repeated many times in the literature review. However, as related to the "Desired Characteristics of the IL" mentioned near the beginning of this report, several more conclusions can be drawn:1. An IL with phases akin to UAl 3 is desired for optimum fuel performance, but at low temperatures, and especially in an irradiation atmosphere, the desired (Al+Si)/(U+Mo) ratio of three is difficult to produce. When the fuel operating temperature is low, it is important to create a pre-irradiation IL enriched in Si. This pre-formed IL is relatively stable, performs well in terms of swelling resistance, and prevents rapid IL growth during irradiation. Fabrication-related heat treatments should be limited in order to maintain a thin, Si-enriched layer containing potentially beneficial phases.2. At higher operating temperatures (>150-170°C), IL formation in reactor may not be so dependent on pre-irradiation IL formation, especially at high burnup; a pre-fabricated IL seems to be less stable at high burnup and high operating temperature. Moreover, the (Al+SI)/(U+Mo) ratio of three occurs more often at higher temperature. For these two reasons, it is important at high operating temperature to also have a matrix with significant Si content to create an IL in-reactor with the right characteristics.3. Out-of-reactor testing seems to indicate that Si in the matrix material is required in some concentration (2%, 5%, ?) to provide for a thin, Si-enriched IL formed before irradiation of a fuel plate. It ensures that the IL contains beneficial phases or prevents formation of some known to promote poor fuel performance. Significant progress has been made in determining the desired characteristics of the IL.4. The use of a fuel with stable gamma phase appears to allow more predictable performance regarding both a beneficial pre-irradiation layer and the fuel performance (low swelling) to high burnup. Destabilization of the gamma phase may create problems with IL breakaway growth.5. A theory whereby prevention of the U 6 Mo 4 Al 43 comp...

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Section: Mo and Si Contentmentioning

confidence: 96%

Section: Phase Identificationmentioning

confidence: 97%

Section: Mo and Si Contentmentioning

confidence: 99%

Section: Multi-layered Ilmentioning

confidence: 99%

Section: Multi-layered Ilmentioning

confidence: 99%

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Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

Porter¹

2010

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Magnesiothermic Reduction Process Applied to the Powder Production of U(Mo) Fissile Particles

et al. 2012

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Uranium‐molybdenum alloy powders are obtained by a new synthetic route deriving from the Kroll process which avoids a “melting‐solidification” step. This alternative process consists in the reduction of uranium dioxide by magnesium in presence of Mo in a sealed Mo crucible heated at temperatures ranging from 750 to 1100 °C for dwell periods ranging from 12 to 48 h. An appropriate quenching allows the retention of the high temperature bcc‐form γ–U(Mo). The side products are easily removed by a soaking into a diluted hydrochloric acid solution under sonication. The agglomerates have a typical size in the range 10–200 µm, with an irregular shape. They display even at the periphery equiaxed grains with homogeneous distribution of Mo. Small closed porosity, which seems to be preferentially located at the grain boundaries corresponds to roughly 2% of the volume fraction.

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Phase Constituents and Microstructure of Interaction Layer Formed in U-Mo Alloys vs Al Diffusion Couples Annealed at 873 K (600 °C)

Perez

Keiser

Sohn

2011

Metall Mater Trans A

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U-Mo dispersion and monolithic fuels are being developed to fulfill the requirements for research reactors, under the Reduced Enrichment for Research and Test Reactors program. In dispersion fuels, particles of U-Mo alloys are embedded in the Al-alloy matrix, while in monolithic fuels, U-Mo monoliths are roll bonded to the Al-alloy matrix. In this study, interdiffusion and microstructural development in the solid-to-solid diffusion couples, namely, U-15.7 at. pct Mo (7 wt pct Mo) vs pure Al, U-21.6 at. pct Mo (10 wt pct Mo) vs pure Al, and U-25.3 at. pct Mo (12 wt pct Mo) vs pure Al, annealed at 873 K (600°C) for 24 hours, were examined in detail. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA) were employed to examine the development of a very fine multiphase interaction layer with an approximately constant average composition of 80 at. pct Al. Extensive TEM was carried out to identify the constituent phases across the interaction layer based on selected area electron diffraction and convergent beam electron diffraction (CBED). The cubic-UAl 3 , orthorhombic-UAl 4 , hexagonal-U 6 Mo 4 Al 43 , and cubicUMo 2 Al 20 phases were identified within the interaction layer that included two-and three-phase layers. Residual stress from large differences in molar volume, evidenced by vertical cracks within the interaction layer, high Al mobility, Mo supersaturation, and partitioning toward equilibrium in the interdiffusion zone were employed to describe the complex microstructure and phase constituents observed. A mechanism by compositional modification of the Al alloy is explored to mitigate the development of the U 6 Mo 4 Al 43 phase, which exhibits poor irradiation behavior that includes void formation and swelling.

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U–Mo/Al–Si interaction: Influence of Si concentration

Cited by 30 publications

References 9 publications

Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

Magnesiothermic Reduction Process Applied to the Powder Production of U(Mo) Fissile Particles

Phase Constituents and Microstructure of Interaction Layer Formed in U-Mo Alloys vs Al Diffusion Couples Annealed at 873 K (600 °C)

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