The Transformational Challenge Reactor (TCR)(tcr. ornl. gov) is a demonstration reactor program showcasing the potential advantages of using additively manufactured components for a nuclear reactor. Recently, new advanced manufacturing methods, including significant advancements in additive manufacturing, have been developed which have great promise in the design of next-generation reactors. However, without demonstration and pilot programs, the project risk for developing a new reactor with these technologies is too high for a commercial reactor. The TCR project is aimed at eliminating this risk by showcasing these new technologies.

The TCR will be a 3 MWth gas-cooled reactor with both additively and conventionally manufactured components. Additionally, the reactor will showcase new highperformance materials, distributed sensing, and on-the-fly certification of components. The TCR fuel forms will use conventionally fabricated uranium nitride tristructural isotropic (UN TRISO) fuel particles [1] embedded in an additively manufactured silicon carbide (SiC) matrix [2]. These fuel forms are densified using chemical vapor infiltration (CVI) after they are printed on a binderjet machine [3]. These fuel forms allow for dramatically greater design flexibility than seen in previous gas-cooled reactor designs, which used either simple cylindrical coolant channels or a pebble bed design [4]. The helium coolant allows for high outlet temperatures and works well with the SiC fuel forms. The basic structure of the TCR fuel forms was determined in the conceptual design phase of the TCR project. The coolant considerations in this initial design down-selection and optimization have been previously reported [5].