Oxygen potential of irradiated urania-plutonia fuel pins

Behavior of metallic precipitate in an irradiated simulated fuel

“…The reason for a low concentration of molybdenum in the metallic precipitate in the fuel's surface region is that molybdenum is likely to be an oxide of MoO 2 at a higher oxygen concentration. The oxidized molybdenum of a fission product is assumed to dissolve in a fuel matrix with an abundant amount of oxygen [10]. It was found that the concentration of Ru had a similar behavior of Mo with the same EPMA analysis methods.…”

“…The oxidized molybdenum was assumed to be dissolved in the oxide fuel matrix. This is a result of a fission process because oxygen cannot be completely bonded by the generated fission products [10]. Hence, the ratio of the molybdenum concentration in the alloys to the MoO 2 concentration in the fuel matrix is an indicator of a local oxygen potential of a fuel which is based on an equilibrium state [10] ½Mo alloy þ ½O 2 fuel ¼ ½MoO 2 fuel ð1Þ…”

X-Rays and Radiochemistry

“…Interestingly, metallic inclusions of noble metals such as Ru, Rh and Pd were also found as a consequence of the redistribution of oxygen in irradiated fuels. Cladding interactions in neutron-irradiated MOX fuels (U0 2 -Pu0 2 ) were studied by Johnson et al [2], With ΕΡΜΑ, these authors showed that intergranular attack of the stainless steel cladding had occurred at the fuel-cladding interface; in particular, fission-produced iodine played an important role in the corrosion of the cladding.…”

“…In particular, satellite peaks appear in PIXE spectroscopy with heavy ions. The intensity of the KL" peak follows a binomial probability distribution I(KL") = Ο P" L (\-PlT (2) where P L is the probability of ionization of the L shell and η the number of L vacancies. As pointed out by Watson et al, the KL" satellite line is closely related to the electronegativity of the neighbouring atoms of the X-ray emitter [50].…”

Over forty years of ‘Thermodynamics of Nuclear Materials’

“…Above a certain oxygen potential the amount of Mo in the quinary alloy would decrease due to the formation of MoO 2 . In fact, the ratio of Mo in the white inclusions to MoO 2 dissolved in the fuel matrix has been used in attempts to characterize the oxygen potential of the fuel as a function of position [86,87].…”