Neutron diffraction measurement of residual stresses, dislocation density and texture in Zr-bonded U-10Mo “mini” fuel foils and plates

Abstract

Al clad U-10Mo fuel plates are being considered for conversion of several research reactors from high-enriched to low-enriched U fuel. Neutron diffraction measurements of the textures, residual phase stresses, and dislocation densities in the individual phases of the mini-foils throughout several processing steps and following hot-isostatic pressing to the Al cladding, have been completed. Recovery and recrystallization of the bare U-10Mo fuel foil, as indicated by the dislocation density and texture, are observed depending on the state of the material prior to annealing and the duration and temperature of the annealing process. In general, the cladding procedure significantly reduces the dislocation density, but the final state of the clad plate, both texture and dislocation density, depends strongly on the final processing step of the fuel foil. In contrast, the residual stress state of the final plate is dominated by the thermal expansion mismatch of the constituent materials.

Texture Evolution in U-10Mo Nuclear Fuel Foils during Plasma Spray Coating with Zr

“…The lattice parameters of the plasma spray coated samples were 3.492-3.505 Å (standard deviation for the eight measurement results σ = 0.010 Å) for a-axis of γ-U. The parameters are sensitive to residual strain, part of which is derived from thermal contraction difference between the coating and the substrate [2]. The amount of thermal contraction depends on the coating temperature, so the variation of the lattice parameters is due to differences in the heating pattern in the coating process.…”

“…In the case of steels, the cold rolling texture with reductions around 60% shows ODF intensities of more than 5.0 mrd, which is stronger than that of the recrystallization texture. Brown et al [2] suggested that a U-10Mo sample which was cold-rolled with a 50% reduction and annealed at 650 • C also shows a recrystallization texture. Compared to the experiment in [2], manufacturing processes in this study consisted of a slightly higher cold rolling reduction and higher annealing temperature, which are more preferable conditions for recrystallization.…”

“…Brown et al [2] suggested that a U-10Mo sample which was cold-rolled with a 50% reduction and annealed at 650 • C also shows a recrystallization texture. Compared to the experiment in [2], manufacturing processes in this study consisted of a slightly higher cold rolling reduction and higher annealing temperature, which are more preferable conditions for recrystallization. Therefore, the U-10Mo used in this study is likely to undergo recrystallization during the annealing process before plasma spray coating.…”

“…Currently, the CONVERT M3 Reactor Conversion Program is developing a high-density, monolithic U-Mo fuel for the research reactor conversion, while at the same time establishing efficient and economic fabrication and manufacturing capabilities. The U-Mo fuel is required to show isotropic properties, such as isotropic thermal expansion, to prevent fuel voids in its application [1,2]. To address this requirement, 10 mass % molybdenum is alloyed to the uranium, which suppresses the orthorhombic α-U phase and stabilizes the body centered cubic (bcc) γ-U phase [3].…”

Recent Progress of Residual Stress Distribution and Structural Evolution in Materials and Components by Neutron Diffraction Measurement at RSND

“…Brown et al researched the residual stress, dislocation density, and texture of U-10Mo alloy on the Spectrometer for Materials Research at Temperature and Stress (SMARTS) at the Los Alamos Neutron Science Center (LANSCE, Los Alamos, NM, USA). They found that the thermal expansion mismatch was the main reason affecting the distribution of residual stress in this material [11]. Using the ENGIN-X strain diffractometer at the Science and Technology Facilities Council's (STFC) laboratory (Swindon, UK), Faisal et al clearly demonstrated the residual stress distribution in Mo-C-based anode layers [12].…”