Materials in Nuclear Energy Systems (MiNES) 2021: Fuels and Actinide Materials- Oxide Fuels I
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory

Thursday 10:20 AM
November 11, 2021
Room: Monongahela
Location: Omni William Penn Hotel

Session Chair: Sarah Finkeldei, University Of California-Irvine


10:20 AM  Invited
Atomic Scale Investigation of Thermodynamic and Defect Properties of (U,Pu)O2 Mixed Oxide: Didier Bathellier1; Marjorie Bertolus1; Emeric Bourasseau1; Michel Freyss1; Luca Messina1; 1CEA
     One way of increasing significantly the efficiency in designing and qualifying innovative fuels is to enhance the predictive capability of fuel behaviour simulation by developing a more physically based description of nuclear fuels. Basic research approaches combining multiscale modelling and separate effect experiments can bring significant insight into materials properties and key phenomena involved in the evolution of fuels in reactor. We will show the results obtained using state-of-the art electronic structure and empirical calculations on the uranium-plutonium mixed oxide. In particular, the thermal expansion, enthalpy increments and specific heat of (U,Pu)O2 as a function of Pu content will be presented. The defect properties of(U,Pu)O2 and the impact of the disorder on the cationic sublattice will also be discussed.This research is part of the INSPYRE project, which has received funding from the Euratom research and training program 2014-2018 under Grant Agreement 754329.

11:00 AM  
Phase-field Simulations of Fission Gas Bubbles in High Burnup UO2 during Steady-state and LOCA Transient Conditions: Larry Aagesen1; Sudipta Biswas1; Wen Jiang1; David Andersson2; Michael Cooper2; Christopher Matthews2; 1Idaho National Laboratory; 2Los Alamos National Laboratory
    U.S. utilities are currently seeking licensing approval to operate UO2 fuel to higher burnups. One significant safety issue that must be addressed to obtain approval is the potential for pulverization of the fuel during a LOCA. It has been hypothesized this is caused by the rapid increase of pressure in fission gas bubbles in the high burnup region of the fuel. To better understand this phenomenon, a novel phase-field model of the fission gas bubble microstructure in UO2 has been developed and implemented in Idaho National Laboratory's Marmot application for phase-field simulation of nuclear materials. During a LOCA transient, simulations of bubbles in the high burnup region showed that bubble size did not change significantly, and the pressure increase due to the transient was calculated and passed to a phase-field model of fracture.

11:20 AM  
Thermal Diffusivity of Nuclear Materials at the Miniature Scale: Najeb Abdul-Jabbar1; Scarlett Widgeon Paisner1; Joshua White1; 1Los Alamos National Laboratory
    To accelerate materials qualification for reactor deployment, a framework has been developed to process and characterize nuclear materials at the miniature scale for irradiation and burn-up experiments at Oak Ridge and Idaho National Laboratories, where specimen geometries are restricted to diameters of ~3 mm and thickness ≤300 µm. The size constraints serve to decouple interrelated materials phenomena that occur in full-scale nuclear reactor testing and will reduce sample radioactivity post-irradiation to avoid costly handling procedures. High-density miniature specimens of pure UO2, U3Si2, and UN have been fabricated by powder metallurgy routes and current efforts have been focused on validating their thermophysical properties. Thermal diffusivity measurements via light flash analysis on UO2 miniature fuels up to 1000 °C have been demonstrated and additional measurements on U3Si2, UN, and reactor cladding materials are currently in progress. The ensuing results will be discussed in the broader context of accelerated nuclear materials testing.