2017 | AFC ACCOMPLISHMENTS 142 The fabrication capability of Mixed Oxide (MOX) fuel in Idaho National Laboratory (INL) has been inactive for years after several discontinuations in activity. Atmosphere control is one of the key factors in successful fabricating MOX (mixed oxide) fuel for high burnups. Regaining MOX fabrication capability in INL is attempted through fine controlling oxygen partial pressure in the sintering furnace for substoichiometric compositions required for high burnups. Project Description: Precise stoichiometry control of MOX fuel is achieved by control of oxygen partial pressure during the sintering of the oxide fuel. For this fine tuning, the gas panel for the sintering furnace in Fuel Manufacturing Facility (FMF) is required to be upgraded for the stoichiometry control after consulting with Kenneth McClellan to utilized Los Alamos Nation Laboratory (LANL’s) experience in MOX fabrication. Main modifications include: • replacing current analog mass flow controller to digital controllers • installing oxygen monitors for the gas flows in and out of the furnace • removing extra thread–sealing points including desiccant filter. MOX Fabrication Trials Principal Investigator: Seongtae Kwon Collaborators: Randall Fielding Other improvements required for the modification of the SCS (substoichiometric control system) include, establishing methods for gas mixture using lecture bottles, upgrading and modifying controlling software according to modified procedures, and developing means for a wide range of oxygen partial pressure for various stoichiometry. The main compositions to be explored for this initial stage of MOX fabrication will be (U0.8Pu0.2) O2-x composition with x 0~0.08 range. Processing condition map for the target stoichiometry will be developed for the stable fabrication of MOX fuel.The project will be further developed to produce stable microstructure of the fuels to mitigate the dimensional change along with retaining porous structure to accommodate fission products. Accomplishments: Digital mass flow controller and oxygen monitor recommended by LANL were located, procured and installed. Due to the discontinuation of the digital mass flow controller model recommended, MKS 647C, a newer version, MKS 946, was selected. Rotameters for dry Ar, wet Ar, hydrogen and nitrogen was installed to visually monitor the flow of gases. Software has been revised to accommodate procedure and component changes. The key fabrication processing capability of substoichometric MOX fuel by fine controlling oxygen partial pressure has been established.