McKinney, Casey. Three-Dimensional Characterization of the Grey Phase in FBR MOX Fuel

Principal Investigator
First Name:
Casey
Last Name:
McKinney
Institution:
University of Florida
Title:
Graduate Research Assistant
Team Members:
Name: Institution: Expertise: Status:
Assel Aitkaliyeva University of Florida Nuclear Fuels, Nuclear Materials, mechanical properties, Microstructure-property relationship Faculty
Fabiola Cappia Idaho National Laboratory Nuclear Fuels, mechanical properties, SEM, LWRS, Raman, microindentation, image analysis Faculty
Michael Tonks University of Florida Michael Tonks will direct the computation efforts in modelling fuel behavior. Faculty
Daniel Murray Idaho National Laboratory FIB, SEM, EDS, ebsd, WDS, XPS Faculty
Experiment Details:
Experiment Title:
Three-Dimensional Characterization of the Grey Phase in FBR MOX Fuel
Describe the work that you are proposing in detail. Please include as many specifics as possible (e.g., dose, dose rate, ion energy, types of ions, beam line x-ray energy, irradiation temperature, analysis temperature, atmosphere, etc.):
The objective of the proposed research is to utilize focused ion beam (FIB) tomography coupled with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS) to gather microstructural and microchemical data on mixed oxide (MOX) fuel irradiated to 13.7% fissions per initial metal atom (FIMA). The proposed research will serially section a 40 µm × 10 µm × 40 µm volume of MOX fuel into ~200 layers, each with an approximate thickness of 50 nm. Secondary electron (SE) images, EBSD scans, and EDS scans will be collected for each layer. This will provide the data necessary to build a comprehensive microstructural and microchemical reconstruction of the fuel sample using FEI’s Avizo software. Once the reconstruction is built, it can be provided to modelers to aid in developing advanced simulations that can be utilized to predict the fuel’s response during normal and transient reactor operation.
Technical Abstract
The comprehensive understanding of a fuel’s microstructure is necessary when trying to predict its performance under varying conditions. As MOX fuel is burned up in the reactor, the production of fission products leads to microstructural changes with the formation of new phases and precipitates. At higher sample burn-ups, the grey phase forms mid-radially and eventually concentrates in the central region of the fuel pellet. Due to the lower thermal conductivity of the grey phase with respect to the bulk of the fuel, the accumulation of it at the hot center of the fuel generates concern of localized melting under accident conditions. This project aims to build a reconstruction of the mid-radial region possessing the grey phase in a MOX fuel sample irradiated to a burn-up of 13.7% fissions per initial metal atom (FIMA). Focused ion beam (FIB) tomography coupled with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS) will be used to gather microstructural and microchemical data while serially sectioning through a volume of material. The micrographs, EBSD, and EDS data will be used to build a comprehensive reconstruction of the three-dimensional (3D) microstructure. Once complete, the reconstruction will be provided to modelers to aid in their development of advanced fuel performance simulations that can predict the fuel’s behavior at increased temperatures. This project will deliver an accurate microstructural and microchemical model of the grey phase found in high burn-up MOX fuel. With an expected timeline of 4 months, the completion of this work will significantly advance the current understanding of the grey phase and its effect on MOX fuel’s properties.
Conference Publications
Name Title
Casey McKinney Three-Dimensional Microstructural Characterization of the Peripheral Region in FBR MOX Fuel