Additive Manufacturing of SMR Holddown Springs and Upper Nozzle Interfaces

Cost and time associated with material waste, quality control, inspection, and manufacturing of nuclear fuel assembly components can be detrimental to nuclear plant design and development. Specifically, holddown springs are prime component examples that inherently carry these issues due to their complex geometries and attachment points. The design engineer must always weigh the manufacturing practices against the operational benefits. To combat this issue, the Department of Energy is highly interested in advancing methods of manufacturing for nuclear energy technologies that allow for easier engineering and commercial production of nuclear fuel assembly component. Proving that complex geometries, holddown springs, can be manufactured with the same design material using additive material technologies shows the nuclear industry that former manufacturing complications are no longer necessary. Additive material technologies also give the designer the option of adding beneficial features to holddown springs and nozzles during the Computer Aided Design (CAD) process that were previously impossible (due to tooling impediments). During Phase II, the spring designs from Phase I that provided promising results will be further refined. The new designs will then be printed in large batches to allow for extensive testing. The testing will include bench testing on single springs and also flow testing to determine pressure drop and life and wear characteristics. The holddown springs will also be analyzed using Finite Element Analysis (FEA) to ensure structural integrity. Using additive material technologies (i.e. metallic 3D printing) minimizes material waste and inspection time while producing fine-tolerance products – increasing quality – that frees the designers to focus on component operation, not manufacturing (welding, milling, stamping, etc). The goal at the end of Phase II is to complete the required testing to allow 3D printed holddown spring to be included on a lead test assembly in subsequent years.