William Charlton

Digital twin technologies, which couple physical systems with their virtual representations for monitoring, prediction, and analysis, have advanced significantly in many engineering domains. However, their deployment in nuclear systems remains limited due to stringent requirements on safety, validation, and system-level integration. Existing efforts often focus on individual components such as high-fidelity simulation or data-driven models, while practical implementations that unify these elements into an accessible and operational framework remain scarce. In response, this work presents the Nuclear Twins Website (NTW), a web-based digital twin platform developed for the NETL TRIGA reactor. The NTW is designed as a centralized and integrated hub that unifies data, simulation, and user interaction. The platform integrates five core components: core configuration analysis, operational data access, a natural-language-based data query interface, an interactive reactor simulator, and a high-fidelity prediction module. By connecting historical data, physics-based models, and user interaction, the NTW enables intuitive exploration, training, and analysis of reactor behavior. Rather than introducing a standalone software tool, this work demonstrates a structured approach for deploying nuclear digital twins that emphasizes integration, accessibility, and validation. The NTW provides a scalable foundation for bridging high-fidelity reactor simulations with practical operational and research workflows.

Quantifying the Pu content in spent nuclear fuel is necessary for many reasons, in particular to verify that diversion or other illicit activities have not occurred. Therefore, safeguarding the world's nuclear fuel is paramount to responsible nuclear regulation and public acceptance, but achieving this goal presents many difficulties from both a technical and economic perspective. The Next Generation Safeguards Initiative (NGSI) of NA-24 is funding a large collaborative effort between multiple laboratories and universities to improve spent nuclear fuel safeguards methods and equipment. This effort involves the current work of modeling several different nondestructive assay (NDA) techniques. Several are being researched, because no single NDA technique, in isolation, has the potential to properly characterize fuel assemblies and offer a robust safeguards measure. The insights gained from this research, will be used to down-select from the original set a few of the most promising techniques that complement each other. The goal is to integrate the selected instruments to create an accurate measurement system for fuel verification that is also robust enough to detect diversions. These instruments will be fabricated and tested under realistic conditions. This work examines one of the NDA techniques; the feasibility of using x ray emission peaks from Pu and U to gather information about their relative quantities in the spent fuel. X Ray Fluorescence (XRF), is unique compared to the investigated techniques in that it is the only one able to give the elemental ratio of Pu to U, allowing the possibility of a Pu gram quantity for the assembly to be calculated. XRF also presents many challenges, mainly its low penetration, since the low energy x rays of interest are effectively shielded by the first few millimeters of a fuel pin. This paper will explore the results of Monte Carlo N-Particle eXtended (MCNPX) transport code calculations of spent fuel x ray peaks. The MCNPX simulations will be benchmarked against measurements taken at Oak Ridge. Analysis of the feasibility of XRFs role in spent nuclear fuel safeguards efforts, particularly in the context of the overall NGSI effort will be discussed.