Characterisation of the surface over-layer of welded uranium by FIB, SIMS and Auger electron spectroscopy

Recrystallisation of uranium resulting from electron beam welding

“…However, the reduced size and more rounded shape of the carbides present at the surface of the fusion zone indicate that partial dissolution of the carbides had occurred during welding, with smaller inclusions likely undergoing total dissolution into the molten uranium. Concurrent work [20] has also identified the presence of many small carbide particles and dendrites on the weld surface and a near surface carbon-enriched region to 1-2 m depth, indicating surface-directed carbon segregation during welding or during uranium crystallisation down to the ␣-phase. It is also suitable to consider the reason for the apparent growth of carbides in the HAZ.…”

“…In the latter the inclusions were typically euhedral cube-shaped growths, 4-5 m in maximum dimension. These inclusions had been previously identified in the parent material as uranium carbo-nitride (hereafter referred to as carbides), with FCC structure using transmission electron microscopy (TEM), Auger electron spectrometry (AES) and secondary ion mass spectrometry (SIMS) [20]. In the EBSD maps presented in Figs.…”

“…1). Numerous cube-shaped inclusions (3-5 m 3 ) interpreted as uranium carbides and/or carbo-nitrides [20] were observed at the surface of the weld. These inclusions were also observed on the section faces occurring in weld, HAZ and unaffected parent material.…”

Derivation of enhanced potentials for uranium dioxide and the calculation of lattice and intrinsic defect properties

“…The function is splined at cut 1 , r min and cut 2 so that the energy, and first and second derivatives, are continuous using formulae shown in Eqs. (6)- (8). The function has a stationary point at r min occurring when the first derivative of the function equals zero.…”

“…UO 2 is also of great technological importance in other arenas and improved understanding of the factors which can limit or induce uranium corrosion is of interest to a variety of industrial activities [7,8]. The extreme affinity of pure uranium for oxygen is well documented [9] with at least 16 oxides observed between UO 2 and UO 3 comprising the principal products of uranium metal corrosion [10].…”