Further insight into mechanisms of solid-state interactions in UMo/Al system

Mazaudier, Fabrice; Proye, C.; Hodaj, F.

doi:10.1016/j.jnucmat.2008.04.016

Cited by 76 publications

(68 citation statements)

References 29 publications

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“…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. Park et al showed stratified and layered structures when Si was present in the matrix material, especially when the U-Mo contained 2% Zr.…”

Section: Multi-layered Ilcontrasting

confidence: 72%

“…There was some work, such as Mazaudier et al 15 using Al alloys with very low Si (0.25 and 0.3 %Si)-this data is not shown here.…”

Section: Analysis Of Il Datamentioning

confidence: 61%

“…15 This temperaturedependent stratification seems to apply to both diffusion couple and dispersion fuel anneal experiments.…”

Section: Effect Of Temperaturementioning

confidence: 89%

“…Both Ryu and Mazaudier assert that the formation of layers within the IL is temperature dependent. 32,15 Based on these results, it appears that 500°C is the threshold temperature below which the IL remains one layer and above which two or even three layers form. Ryu mentions that when the dispersion fuels were annealed at 500°C, only one layer formed, but at temperatures of 525 or 550°C, two or more layers formed.…”

Section: Effect Of Temperaturementioning

confidence: 98%

“…Mazaudier, Mirandou, and Ryu have all observed three layers within the IL in the UMo/Al system. 14,17,19,32 The composition of these three layers is not yet agreed upon based on this literature, but each of these articles suggests the presence of three layers. While Mirandou observed all three layers, she asserts that there is no clear boundary between them, while the others suggest the layers are distinct.…”

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: Multi-layered Ilcontrasting

confidence: 72%

“…There was some work, such as Mazaudier et al 15 using Al alloys with very low Si (0.25 and 0.3 %Si)-this data is not shown here.…”

Section: Analysis Of Il Datamentioning

confidence: 61%

“…15 This temperaturedependent stratification seems to apply to both diffusion couple and dispersion fuel anneal experiments.…”

Section: Effect Of Temperaturementioning

confidence: 89%

Section: Effect Of Temperaturementioning

confidence: 98%

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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Interaction of uranium-molybdenum fuel with an aluminum matrix with deep burnup

et al. 2010

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A thermodynamic analysis is used to calculate the phase and component composition of uraniummolybdenum fuel with burnup 200 GW·days/ton. The equilibrium composition of the gas phase, consisting mainly of gaseous cesium whose pressure reaches 30 kPa, is determined more accurately. The quantitative composition of the phase of solid solutions of tellurides, whose formation degrades the structure of a fuel granule, is presented. Thermal tests of the fuel composition (U-Mo)-Al were performed. The investigation was performed in the presence of simulators of the chemically active fission products of cesium and iodine at different temperature. The interaction zone of (U-Mo)-Al is investigated by means of metallography and scanning electron microscopy. The data obtained on the composition of the indicated zone made it possible to conjecture the character of interaction between the fuel material and the aluminum matrix.The world is showing heightened interest in power reactor facilities of low and ultralow power and research nuclear reactors. These facilities use dispersion compositions in the form of UO 2 , UAl x , U 3 Si 2 , uniformly distributed in an aluminum matrix, as nuclear fuel. The 235 U enrichment often reaches >90% [1].When low (to 20%) enrichment fuel is used, the burnup decreases because of the lower volume content of 235 U [2]. As compensation it is suggested that fuel granules consisting of U-9%Mo (density 17.2 g/cm 3 ) in a matrix consisting of an aluminum alloy be used [3,4]. For example, if in the composition UO 2 -Al the uranium content is 3-3.5 g/cm 3 , then in the composition (U−9Mo)-Al it increases by a factor of 2. However, the use of the composition (U-Mo)-Al is held back by the interaction between uranium-molybdenum granules and an aluminum matrix with burnup 150-200 GW·days/ton [5]. This interaction is complicated. On the one hand, a chemical interaction is observed in the system U-Al at a temperature close to the melting temperature of aluminum. On the other hand, the effect of the fission products on the physicochemical and physical-mechanical characteristics of uranium-molybdenum alloy must be taken into account.The compatibility of the fuel with the matrix can be improved by introducing into the alloy a component, for example, silicon, that substantially lowers the interaction rate as well as by depositing a coating on the surface of the fuel particles [5][6][7][8].Even though from the technological point of view alloying with silicon is considered to be optimal, one should take note of the decrease of the stability of the γ-U-Mo phase. The introduction of silicon into an intermetallide does not exclude the focal interaction with aluminum; in addition, it can increase the temperature gradient at the boundary between a fuel granule and an aluminum matrix [6].Of special interest is the appearance of barrier coatings on the surface of uranium-molybdenum granules. Specifically, it is proposed that a layer of pure molybdenum be deposited on the fuel granules, which would then be protected from int...

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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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Further insight into mechanisms of solid-state interactions in UMo/Al system

Cited by 76 publications

References 29 publications

Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

Interaction of uranium-molybdenum fuel with an aluminum matrix with deep burnup

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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