Current Projects
Thermal Transport and Fracture Behavior of Sintered Fuel Pellets: Experimental Validation of NEAMS Tool MARMOT
Objective: validate fuel behavior models developed in MARMOT.
This project will perform extensive thermal transport and fracture experiments on UO2 to improve understanding of the impact of microstructure on thermo-mechanical properties. Experiments include:
- Sintering UO2 samples with well-controlled microstructures
- Thermal conductivity measurements of well-characterized UO2 samples
- Indentation testing of sintered UO2 with various grain size, porosity, and stoichiometry to obtain fracture and crack propagation mechanisms
- Validation and uncertainty quantification of the MARMOT thermal transport and fracture models
UO2 Fuel Pellet Sintering and Densification Modeling
Objective: develop a phase-field based model of microstructure evolution of UO2 pellets during manufacturing and irradiation
UO2 pellets are manufactured through sintering, which yields very specific types of microstructures. These microstructures then have a large impact on fuel behavior and performance while under irradiation inside nuclear reactors. This project seeks to understand this relationship better. This project will:
- Combine existing phase-field models of sintering and irradiation effects on microstructure evolution
- Develop a phase-field model of field-assisted sintering and combine with other models
- Model fuel densification and swelling over entire life cycle of pellets
- Optimize manufacturing process to improve fuel evolution and behavior
Radiation-induced swelling and microcracking in SiC cladding for LWRs
Objective: develop a master phase-field equation that can predict the amount of swelling and micro cracking in SiC cladding material as a function of temperature and irradiation histories.
After the 2011 Fukushima accident, SiC gained attention as a potentially less hazardous cladding material for use in nuclear fuel rods. However, our understanding of irradiation-induced swelling is incomplete. Current models of irradiation-induced swelling in SiC have been largely empirical, so they cannot be used to predict the microstructural dependence of microcracking. Objectives of this project include:
- Understanding defects that form within the range of temperatures relevant to fuel cladding
- Develop a governing set of equations for SiC behavior in these ranges
- Model SiC behavior in operation and accident scenarios
Development of Accident Tolerant Fuel Options For Near Term Applications
Objective: develop computational tools to evaluate accident tolerant fuel (ATF) options in order to increase accident tolerance
Since the 2011 Fukushima accident, dozens of new accident-tolerant fuels have been proposed for use in Light Water Reactors. Each new concept involves some changes to the conventional UO2 pellets and Zircaloy cladding. Testing each of these fuel concepts would be prohibitively expensive. In order to get a better idea of which concepts are worth exploring further, computer simulations will be used to estimate fuel behaviors. This project will:
- Develop computer models of several accident-tolerant fuel concepts
- Evaluate models under transient and steady conditions
- Estimate melting time for fuel and core components
- Gather experimental data to validate and improve models
Multilayer Composite Fuel Cladding for LWR Performance Enhancement and Severe Accident Tolerance
Objective: improve cladding to resist runaway oxidation during accidents and minimize corrosion during normal operation
Bi-layered composite materials have recently been successfully designed to resist corrosion and maintain mechanical integrity. Each layer performs a specific function. This research seeks to determine if a composite material could improve behavior of fuel cladding in reactor accidents. This research will:
- Fabricate composite materials
- Characterize and model joining techniques
- Develop computer models of cladding performance
- Validate models with experimental data
Surface Manufacturing for Specific Wetting Behavior
Objective: better understand the mesoscale material properties that create hydrophobic and hydrophilic surfaces
Mesoscale surface structures have been developed in recent years which dramatically affect how the surfaces interact with water. However, the cause of this change is largely unknown. This project seeks to:
- Understand the material properties that affect this behavior
- Develop phase-field based computer models of this interaction
- Design new surfaces to improve interactions with water even further
A Coupled Experimental and Simulation Approach to Investigate the Impact of Grain Growth, Amorphization, and Grain Subdivision in Accident Tolerant U3Si2 Light Water Reactor Fuel
Objective: The objectives of this project are to determine temperature and dose thresholds for the occurrence of grain growth, amorphization, and grain subdivisionin U3Si2 fuel using experiments and simulation.
U3Si2 is a candidate for an accident tolerant fuel system for existing light water reactors. However, before this fuel can be adopted, we need to learn more about the microstructure evolution that takes place during reactor operation. In this project, we are specifically investigating various changes to the grain structure. This information will be provided to the Fuel Cycle R&D program, as well as to other interested vendors, to assist in the development of U3Si2 as an accident tolerant fuel concept.