Candidate Core Designs for the Transformational Challenge Reactor

Abstract

Early cycle activities under the Transformational Challenge Reactor (TCR) program focused on analyzing and maturing four reactor core design concepts: two fast-spectrum systems and two thermal-spectrum systems. A rapid, iterative approach has been implemented through which designs can be modified and analyzed and subcomponents can be manufactured in parallel over time frames of weeks rather than months or years. To meet key program initiatives (e.g., timeline, material use), several constraints—including fissile material availability (less than 250 kg of HALEU), component availabilities, materials compatibility, and additive manufacturing capabilities—were factored into the design effort, yielding small (less than one cubic meter in volume) cores with near-term viability. The fast-spectrum designs did not meet the fissile material constraint, so the thermal-spectrum systems became the primary design focus. Since significant progress has been made on advanced moderator materials (YHx) under the TCR program, gas-cooled thermal-spectrum systems using less than 250 kg of HALEU that occupy less than 1 m3 are now feasible. The designs for two of these systems have been evolved and matured. In both thermal-spectrum design concepts, bidirectional coolant flow is used. Coolant flows down through YHx moderator elements and is reversed in a bottom manifold and core support structure, and then flows up though or around the fuel elements. The main difference between the two thermal-spectrum design concepts is the fuel elements—one uses traditional UO2 ceramic fuel, and the other uses UN-bearing TRISO fuel particles embedded inside a SiC matrix. Core neutronics and thermal performance for these systems are assessed and summarized herein.

Artificial Intelligence for Multiphysics Nuclear Design Optimization with Additive Manufacturing

“…Alternatively, most of the work performed under the TCR program focused on developing a process to combine an additive and a traditional fuel manufacturing process. The TCR fuel form consists of conventionally manufactured UN tristructural isotropic (TRISO) fuel particles embedded inside a 3D printed SiC matrix [6,39,40]. In the TCR fuel form, TRISO particles are poured into a 3D printed SiC shell, creating a fuel form that has all the features one might expect from a fully additively manufactured fuel element (e.g., complex surface features, complex cooling channels, variable fuel density), as shown in Figure 3, but constitutes a more near-term deployable fuel production process.…”

“…Beyond applications for existing nuclear reactors, these new manufacturing methods, advanced materials, and dimensional constraints can be applied to the nuclear core design problem [4,5]. A manufacturing-informed design approach yields the most benefit from the application of advanced manufacturing in the nuclear industry [6][7][8][9], leveraging advanced materials, data science, and rapid testing and deployment to decrease costs and development times and ultimately improving future commercial viability. This approach is being demonstrated under the US Department of Energy Office of Nuclear Energy's Transformational Challenge Reactor (TCR) program [10].…”

Large-Scale Additive Manufacturing of Silicon Carbide with Process Monitoring

“…• Demonstrating an agile design process to leverage AM and rapidly converge on an optimized, advanced nuclear microreactor design [9][10][11][12][13][14][15] • Advancing new reactor materials such as an yttrium hydride moderator [16][17][18][19][20][21][22], AM 316 stainless steel (316SS) [23], AM silicon carbide (SiC) [24,25], and the novel integration of uranium nitride tristructural-isotropic fuel [26] densely packed in an AM SiC matrix [27] • Developing the digital platform necessary to certify and qualify AM materials for nuclear applications [28][29][30] • Integrating and embedding spatially distributed sensors within AM materials for nuclear applications [31][32][33][34] • Progressing toward semi-autonomous reactor operation [35,36] • Evaluating and understanding radiation effects on AM SiC [37,38], 316SS [39], and integral TCR fuel compacts [27,40] In fiscal year (FY) 2021, the TCR program priorities shifted away from a nuclear reactor demonstration, but the focus on advancing ceramic AM for nuclear applications and qualifying AM components remained. Eventually, the TCR program was merged into the AMMT program and focused on the broader adoption of AM for nuclear applications compliant with American Society of Mechanical Engineers (ASME) Nuclear Quality Assurance (NQA-1) standards.…”