Fission Reactor Modeling & Design
Our fission research focuses on how reactor systems can be modeled, designed, and evaluated with enough confidence to support deployment and long-term operation. This includes both light-water reactors and more specialized reactor concepts, where design choices can affect cost, safety margins, fuel utilization, licensing confidence, and operational flexibility. We study these questions using reactor physics, thermal-hydraulics, fuel-cycle analysis, and coupled multiphysics simulations.
A major part of this work is benchmarking and validation. We use historical experiments, modern computational tools, and coupled physics models to understand how well simulations represent reactor behavior in steady-state and transient conditions. We also examine specific design and analysis questions in high-temperature reactors, pebble-bed reactors, small boiling water reactors, and pressurized water reactor core design. Across these efforts, we aim to connect detailed modeling with the practical questions that shape reactor performance, safety, and deployment risk.
Separate and Multiphysics Effects IRPhEP Benchmark Evaluation using SNAP Experiments
We are working with Georgia Tech, INL, BWXT, and LANL to prepare a benchmark evaluation for the SNAP 8 Experimental Reactor (S8ER), a highly reflected space microreactor that was built and operated in the 1960s. This project benchmarks data from both steady-state dry critical experiments and wet operating experiments. We utilize cutting-edge tools such as Serpent and OpenMC to evaluate the steady-state characteristics of the reactor and couple these with other physics solvers from the MOOSE suite to incorporate direct thermal feedback for the operating experiments.
For the wet experiments, we are also comparing two different methods for evaluating multiphysics phenomena to understand their differences and what those differences would mean for future reactor design work. This project incorporates much of the reactor design process and highlights the impact of real-world inconsistencies that cannot be exactly modeled or that are not expected. For this reason, the project synthesizes a broad range of nuclear topics, such as neutronics, thermal-hydraulics of advanced reactors, and materials science.
This work is supported by the U.S. Department of Energy, Office of Nuclear Energy, through the Nuclear Energy University Program.
Telescopic Control Rod for Significant Reduction in HTR Height and Cost
Due to their low power density and high aspect ratio, high-temperature reactors (HTRs) have tall cores that may (Xe-100) or may not (HTR-PM) be contained within a silo embedded in the ground. Incremental increases to silo depth are high cost; thus, we propose a compact design for a small modular HTR control rod that extends telescopically. The technology is applicable to both pebble-bed and prismatic HTRs. This compact component substantially reduces the length of the above-vessel control rod housing compartments, thereby reducing the depth of the silo and offering potentially major cost benefits.
The primary objective of this project is to develop the telescopic control rod to the point of being technically feasible and licensable through a multidisciplinary design study encompassing theoretical and experimental work, performed in collaboration with the MADCOR laboratory at UW–Madison, Framatome, X-Energy, INL, and the University of Manchester and Jacobs in the UK.
This work is supported by the U.S. Department of Energy, Office of Nuclear Energy, through the Nuclear Energy University Program.
Modeling of Pebbles in Pebble Bed Reactors
To accurately analyze pebble-bed reactors, pebble behavior must be modeled to determine flow paths and pebble residence times. We have ongoing work using the DEM code Project Chrono to model pebbles in pebble-bed reactors with varied geometries. The results are then used in Monte Carlo simulations to determine reactor performance, particularly fuel utilization.
Coupled Neutronics and Thermal-Hydraulics Stability Analysis of a Small Boiling Water Reactor (sBWR)
Small boiling water reactors (SBWRs) are being actively pursued as part of the next generation of nuclear energy, particularly those that operate under natural circulation. The challenges associated with this type of design include instabilities that can occur as a result of the two-phase flow present. To better understand these instabilities, the analysis of these reactors can be performed using the coupled neutronics and thermal-hydraulics codes PARCS and TRACE. This allows the multiphysics feedback to be more accurately captured within the model. This work aims to enhance the criteria for defining stable regions of operation by simulating and studying the behavior of the BWRX-300.
This work is supported by the U.S. Nuclear Regulatory Commission.
Development of a Fission-Fusion Hybrid System for Transuranic Waste Processing
Molten Salt Reactors (MSRs) offer potential benefits in safety, fuel utilization, and power density but are complex systems with closely coupled multiphysics effects. Work initially facilitated through the Fission–Fusion Hybrid (FFH) project developed workflows within two open-source codes (GeN-Foam and OpenMC) to analyze the safety of transuranic (TRU)-fueled critical systems, as well as to compare subcritical and critical systems under transient accident scenarios. The analysis found that subcritical operation creates new operational complexity but performs much better in reactivity insertion scenarios, where critical TRU systems (especially those with a majority of minor actinides) are unstable.