b'Process #1 included centerline hole drilling followed by pressing in a support tube, defueling, thenFigure 3. Jig revision 5 placing in a loose fit spacer. This process yielded decent results for the centerline hole and the initial tube pressing. It required a center drill with a drill bit to create a pilot hole, which adds a separate piece of equipment and step. However, the molybdenum tube did not hold up well during the defueling step. While the endmill cut through the hard cordierite, the tube split andFigure 4. Welds using Jig revision 5 cracked causing major top surface damage to the cordierite pellets. The tube required another opera-tion with a drill bit to re-open the end of the tube so it could accept a thermocouple and the spacer, being a smaller outside diameter, slipped into the tube. This process also required a larger inside diam-eter to ensure the centerline hole lined up with the spacer.Performing this process in-cell Process #2 included defueling,would more than likely prove to pressing a spacer with anbe infeasible.interference fit, centerline hole drilling through the spacer withProcess #3 included defueling, a diamond core drill, then apressing in a pre-drilled spacer drill bit through the surrogatewith a slight interference fit, fuel, and finally pressing in thecenterline hole drilling through support tube. The process resultedthe surrogate fuel, and finally in a successful installation of apressing in the support tube. support tube inside the centerlineWhile the previous processes hole. This was advantageous ashad somewhat acceptable results it ensured all centerline holeswith varying degrees of success, through the spacer and the surro- this method utilized general gate pellets were in line. However,steps of refabrication but with a the process to drill through thedifferent spacer design. Typical space on the mini-mill with nospacer designs are a loose fit to coolant and manual controls wasapply compression, from the wave very time consuming and difficult.springs, on fresh fuel stacks to hold It required several diamond corethem into place. This particular drills to be used and replacedspacer was designed to have a while drilling due to excessiveslight interference fit into the heat damaging the core drills.cladding (.0000 - .0005 inches). The 2023|AFC ACCOMPLISHMENTS 207'