The Dissolution and Characterization of Aluminum Clad Oxide Fuel

Laboratory dissolution studies of aluminum clad mixed oxide fuel rods have been conducted using two different F-Canyon decladding and dissolving flowsheets. During the first phase of the experimental program, materials from three different color coded fuel rods were dissolved in caustic and nitric acid solutions. The final phase of the laboratory program involved the dissolution and characterization of materials from three cracked pellet fuel rods using a selected caustic/ nitric acid flowsheet.Laboratory results obtained from the initial dissolution studies identified several inconsistencies and potential problem issues with the behavior of materials from the color coded fuel rods. Based on these findings and influenced by the difficulties introduced by using the RCRA listed mercury during processing, the flowsheet selected for dissolving these aluminum clad fuel rods in F-Canyon dissolvers was the two- step caustic decladding/ nitric acid dissolution flowsheet.The final phase of the experimental program involved testing materials from three cracked pellet fuel rods using the selected flowsheet. Again all aluminum fuel rod components dissolved during the decladding step. However, some uranium and plutonium bearing solids remained with the caustic decladding solution which could be sent to waste. The quantities of uranium and plutonium expected to remain with the caustic solutions are small.Fluoride ions will need to be present in the nitric acid dissolver solution to dissolve all solids. At 0.05 molar fluoride concentration, no plutonium bearing solids remained in the product solutions