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The Westinghouse AP1000® nuclear reac- tor features a revamped fuel assembly providing improved fuel performance over the previous reactor model.


add features or do things differently to improve machinability.” GSC suggested some radii and gussets in the corners, where the part transitions vertically, to improve flow- ability of the wax to make the pattern, as well as the molten metal. “Features like that, we would not


have thought of,” Peterson said. “Radius sizes for castability was a key factor, so the supplier’s input was important.” After reviewing GSC’s suggestions,


Westinghouse approved the design to move through to the next phase and a rapid prototype was made. GSC used stereolithography to


produce wax patterns from the CAD model then cast the prototype part in CF-3 stainless steel. Te investment caster partially machined the part before shipping it to Westinghouse for load testing. It was one of GSC’s first forays into rapid prototyping. “Out of that, we were able to re-


ceive early prototypes for risk mitiga- tion,” Lewis said. “In project manage- ment, we have a jump-off schedule. In this case, we asked the supplier to develop a contingency process in case the single-piece casting design could not be validated.” For contingency, GSC and West- inghouse designed the wax tool con- figuration in such a way that if the top nozzle could not meet final require- ments, GSC would need to change only a portion of the tool to revert to the two-piece design. Te contingency plan was never needed. Typically, new part designs at


Westinghouse go through a pre- prototype, prototype, preproduction and production run. After the first prototype parts were tested, Westing- house refined the design and sent it back to GSC for final optimization for castability. GSC produced a wax tool to cast a small run of preproduction castings machined to the final dimen- sions. Westinghouse assembled the cast nozzles to a fuel assembly for full- size flow testing that simulated flow conditions in the nuclear core. Tis initial test proved a 30% reduction in


24 | METAL CASTING DESIGN & PURCHASING | Jan/Feb 2013


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