Evidence for the presence of U–Mo–Al ternary compounds in the U–Mo/Al interaction layer grown by thermal annealing: a coupled micro X-ray diffraction and micro X-ray absorption spectroscopy study

Palancher, H.; Martin, Philippe; Nassif, Vivian; Tucoulou, R.; Proux, Olivier; Hazemann, Jean‐Louis; Tougait, Olivier; Lahéra, Eric; Mazaudier, Fabrice; Valot, C.; Dubois, S.

doi:10.1107/s0021889807040010

Cited by 39 publications

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“…Perez et al [23] annealed a series of diffusion couples of U-Mo vs pure Al (99.999 pct) at 823 K (550°C), and determined the (U,Mo)Al 4 as the average composition of the interdiffusion zone based on electron probe microanalysis (EPMA). Mirandou et al, [24] Palancher et al, [25] and Mazaudier et al [26] observed, in addition to the (U,Mo)Al 3 and (U,Mo)Al 4 phases, the U 6 Mo 4 Al 43 and UMo 2 Al 20 ternary intermetallic phases, along with the cfi(a+d) decomposition of the U-Mo alloy. More recently, Mirandou et al [27] examined diffusion couples of U-7 wt pct Mo vs AA6061 for 823 K (550°C) for 3 hours and 613 K (340°C) for 3216 hours.…”

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confidence: 95%

“…Keiser et al, [22] Palancher et al, [25] and Perez et al [23,28] reported concentration profiles of sufficient thickness to permit analysis, by energy dispersive spectroscopy (EDS) and EPMA, of the interaction layer. Concentration profiles of U, Mo, and Al show negligible gradients with near constant concentrations, particularly for Al throughout the interdiffusion zone thickness.…”

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confidence: 98%

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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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confidence: 95%

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confidence: 98%

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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“…The reaction products are undesirable because they generate a low conductivity interaction layer (IL) by nuclear fission, leading to potential structural failure 3,8,9 . The thermal experiments are normally carried out below γ-phase temperature formation to simulate the interdiffusion and phases formation in U-Mo-Al 10 . The more common observed phases have been (U,Mo)Al 2 , (U,Mo)Al 3 (U,Mo)AL 4 [9] .…”

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confidence: 99%

Interdiffusion studies on hot rolled U-10Mo/AA1050

et al. 2012

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The U-Mo alloys are investigated with the goal to become nuclear material to fabricate high-density fuel elements for high performance research reactors. The enrichment level (20% 235 U) suggests that the U-Mo alloys should be between 6 to 10 wt. (%), which can reach up to 9 gU.cm -3 in fuel density. Nevertheless, the U-Mo alloys are very reactive with Al. Interdiffusion reaction products are formed since nuclear fission promotes chemical interaction layer during operation, leading to potential structural failure. Present studies were made with treated hot rolled diffusion couples of U-10Mo inserted in Al (AA1050). The U-10Mo/AA1050 pairs were treated in two temperatures (150 °C and 550 °C) with three soaking times (5, 40 and 80 hours). From microstructure analyses, rapid diffusion of Al happened inside U-10Mo in the first heating at 540 °C during 15 minutes, reaching 8 at% Al in a range of 170 µm towards U-10Mo. Longer time at 550 °C treatment maintain this level of Al-content up to 1000 µm inside U-10Mo. In this study, the results suggested the formation of a barrier made by residual elements, which promoted little interdiffusion phenomena between U-10Mo and alloy AA1050. Silicon co-diffusion with Al, along the interdiffusion line, is thought to be an important indication for this interdiffusion blockage.

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“…Palancher identified UAl 2 , UAl 3 , and U 6 Mo 4 Al 43 in ILs formed during anneal at 600°C. 24 In a separate publication, Palancher 25 identified the presence of (U,Mo)Al 3 , (U,Mo)Al 4 , UMo 2 Al 20 , and U 6 Mo 4 Al 43 in a diffusion couple and a dispersion fuel annealed at 600 and 500°C, respectively. These results are somewhat contradictory, although the results based on the dispersion fuels are based on tests run at different temperatures.…”

Section: Phase Identificationmentioning

confidence: 99%

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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Evidence for the presence of U–Mo–Al ternary compounds in the U–Mo/Al interaction layer grown by thermal annealing: a coupled micro X-ray diffraction and micro X-ray absorption spectroscopy study

Cited by 39 publications

References 18 publications

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

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

Interdiffusion studies on hot rolled U-10Mo/AA1050

Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

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