Materials in Nuclear Energy Systems (MiNES) 2021: Fuels and Actinide Materials- Oxide Fuels II
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory
Thursday 1:10 PM
November 11, 2021
Room: Monongahela
Location: Omni William Penn Hotel
Session Chair: Maria Okuniewski, Purdue University
1:10 PM Invited
New Microscopic Insights into the Fuel Cladding Interaction Layer of High Burnup Fuel: Sarah Finkeldei1; Karen Wright2; Nedim Cinbiz2; Boopathy Kombaiah2; Fabiola Cappia2; 1University of California-Irvine; 2Idaho National Laboratory
The fuel-cladding interaction layer plays a vital role in nuclear fuel rod performance during off-normal, in particular, transient conditions. Thus, understanding the microstructural features and local chemistry will help to better predict the mesoscale behavior of high burn-up fuels. X-ray maps were collected with an electron probe microanalyzer (EPMA) at the cross section of a high burnup pellet with detailed characterization of the pellet cladding interaction (PCI) layer, revealing the distribution and location of fission products, gases and epsilon particles. EPMA data are complemented with TEM measurements, including orientation mapping via precession electron diffraction technique to gain insights about the chemical and microstructural nature of the PCI and the high burnup fuel which will enable better evaluation and analysis of upcoming TREAT experiments.
1:50 PM
Three-dimensional Characterization of Microstructural Features in Oxide Fuels: Casey McKinney1; Assel Aitkaliyeva1; 1University of Florida
Nuclear fuels undergo various microstructural and chemical changes during their lifetime in the reactor. Temperature gradients cause grain restructuring while fission disperses new phases and precipitates throughout the fuel microstructure. Understanding how these features evolve over the lifetime of the fuel is vital as each one has the potential to compromise the safety of the reactor. In this work, we employ focused ion beam (FIB) tomography to study the microstructural evolution. With the incorporation of electron backscatter diffraction (EBSD) and energy dispersive x-ray spectroscopy (EDS), we can study the grain and fission product evolution in oxide fuels. The reconstructions obtained from this study will be used to assess solid and gaseous fission product behavior and their relationship to the local grain structure.
2:10 PM
Modeling the Mechanisms of Fuel Pulverization Using Cluster and Molecular Dynamics: Michael Cooper1; Christopher Matthews1; Robert Daum2; David Andersson1; 1Los Alamos National Laboratory; 2Electric Power Reseach Institute
Reactor operators in the US would like to extend the refueling cycle length in PWRs from 18 to 24 months, which requires an increase in the peak rod average burnup from 62 GWd/tU to 75 GWd/tU. The high burnup structure (HBS) that forms in UO2 under such conditions is susceptible to fragmentation and pulverization when it experiences a temperature ramp (e.g., during a LOCA). The resultant relocation/dispersal of fuel particles represents a significant safety concern. In this work, we use cluster dynamics to examine the over-pressurization of Xe bubbles through irradiation-enhanced diffusion processes relevant to the cooler temperatures found in the periphery of the pellet, where HBS forms. Then, we employ MD simulations to examine the impact of over-pressurized inter-granular bubbles on the fracture of grain boundaries during temperature ramps, as a proposed mechanism for fuel pulverization. The peak temperature, bubble size, bubble number, and bubble pressure are all examined.
2:30 PM Cancelled
Experimental Characterization of the Chemical Behavior of Cs, I and Te in UO2: Morgane Rochedy1; Vincent Klosek1; Chantal Riglet-Martial1; Claire Onofri-Marroncle1; Doris Drouan1; Philippe Bienvenu1; Ingrid Roure1; Martiane Cabié2; Lucia Amidani3; Myrtille Hunault4; Jacques Lechelle1; Marie-Amandine Pinault-Thaury5; 1CEA, DES, IRESNE / DEC; 2Université Aix-Marseille, CP2M; 3HZDR; 4SOLEIL; 5Université de Versailles St Quentin en Yvelines, GéMAC
Studies are undertaken to better understand Iodine-Stress Corrosion Cracking (I-SCC) of Zircaloy cladding due to Pellet-Cladding Interaction (PCI) in transient conditions [1]. The efficiency of iodine at producing SCC varies with the chemical iodide compounds in interaction with the cladding [1, 2]. In irradiated UO2 fuel, iodine speciation is determined by the (Cs-Mo-I-Te)-UO2 chemical system [2]. In the present study, simulated fuel samples were prepared by implanting UO2 pellets with Cs, I and/or Te. The samples were thermally treated in carefully controlled (T, pO2) conditions and characterized using SIMS, TEM, EELS and XAS techniques. Relevant (T, pO2) phase diagrams were computed to design the tests and interpret the observations. Results regarding the Cs-UO2, I-UO2, (Cs-I)-UO2 and (Cs-I-Te)-UO2 systems are presented and discussed considering thermochemical equilibria and fission products interactions with microstructural defects. [1] P. Konarski et al., JNM, 519, 104-120 (2019)[2] L. Desgranges et al., JNM, 437, 109-414 (2013)
2:50 PM Break