Papers by Author: Kumar Sridharan

Abstract: Fuel Cladding Chemical Interactions (FCCI) in a nuclear reactor occur due to thermal and radiation enhanced inter-diffusion between the cladding and fuel materials, and can have the detrimental effects of reducing the effective cladding wall thickness and the formation of low melting point eutectic compounds. Deposition of diffusion barrier coatings of a thin oxide on the inner surface of the cladding can potentially reduce or delay the onset of FCCI. This study examines the feasibility of using nanofluid-based electrophoretic deposition (EPD) process to deposit coatings of titanium oxide, yttria-stabilized zirconia (YSZ) and vanadium oxide. The deposition parameters, including the nanofluid composition, current, and voltage were optimized for each coating material using test flat substrates of T91 ferritic-martensitic steel. Diffusion characteristics of the coatings were investigated by diffusion couple experiments using the fuel surrogate cerium. These diffusion couple studies performed in the temperature range of 560°C and 585°C showed that the oxide coatings significantly reduce the solid state inter-diffusion between cerium to steel.

Abstract: Grain boundary engineering (GBE) was employed to improve the oxide exfoliation resistance and mitigate oxide growth by optimizing the grain boundary character distribution. Studies were performed on alloys of Incoloy 800H and Inconel 617. Alloys 800H and 617 were selected due to their potential applications for the Generation IV nuclear power systems. The effect of GBE on the corrosion response was evaluated using supercritical water exposure tests and cyclic oxidation tests. The microstructure of the tested samples was analyzed by means of optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, electron backscatter diffraction, and gravimetry. The effects of thermal expansion mismatch and Cr volatilization on the corrosion response are discussed.