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Title: Microstructure and Fission Product Distribution Examination in the UCO kernel of TRISO Fuel Particles

Abstract

The effect of irradiation and fabrication process on the UCO fuel kernel, kernel-buffer interlayer and fission products, has not been fully studied for UCO fuel kernels of TRISO coated particles. Specifically, the potential correlation(s) with fission product retention, composition and distribution within these structures for the tristructural isotropic (TRISO) fuel performance at normal and accident conditions, are not well reported in literature. Structural and chemical information in the irradiated UCO fuel kernel, e.g., the stoichiometry variations, may further contribute to fuel performance modeling under the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. The microstructural and micro-chemical evolution of selected irradiated UCO fuel kernels, kernel buffer interfaces and recoil zones were characterized using Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive Spectroscopy (EDS) elemental mapping. The fuel kernel of particles from Advanced Gas Reactor (AGR)-2 irradiated to 10.8% fissions per initial metal atom (FIMA), were examined with the following main findings: (1) large fission gas bubbles were mainly identified in the zirconium and molybdenum enriched but oxygen depleted phases in the center of fuel kernel, (2) significant inter-diffusion between the UCO fuel kernel and pyro-carbon buffer layer was observed as a high density of sub-micron sized carbon inclusions was identifiedmore » at near the interface in the kernel side and some isolated UCO particles were located in the buffer layer, (3) pores filled with free carbon were also observed in the recoil zone specimen. Fuel kernels from two AGR-1 compacts irradiated to 11.4 and 17.4% FIMA respectively, were examined with the following main findings: (1) two primary phases consisting of a “high-Z (atomic mass)” UC(O) phase (rocksalt; a=0.496 nm) that also contained Zr, Mo, and/or Ru and a “low-Z” UO2(C) phase (fluorite structure; a = 0.547nm) in which trace amounts of I, Nd, Pr, and/or Er could be detected. This latter phase contained many precipitates of the “high-Z” phase. Conversely, this latter phase did not contain precipitates of the UO2-type material, (2) Xe bubbles were found almost exclusively in the “high-Z” phase and in the particular example shown, the Zr-containing variant. Further work in this area should address whether this potential Xe preference for just one of the high-Z phases is indeed a real effect.« less

Authors:
ORCiD logo [1];  [2];  [3];  [1];  [4]
  1. Idaho National Laboratory
  2. Materials Science and Engineering Department, University of Florida, Gainesville, FL
  3. Nuclear Materials Science, Los Alamos National Laboratory, Los Alamos, USA
  4. University of Florida
Publication Date:
Research Org.:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1478773
Report Number(s):
INL/CON-18-44479-Rev000
DOE Contract Number:  
AC07-05ID14517
Resource Type:
Conference
Resource Relation:
Conference: HTR2018, Novotel Warszawa, 10/09/2018 - 10/10/2018
Country of Publication:
United States
Language:
English
Subject:
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS; UCO; Fuel; kernel; Scanning Transmission Electron Microscopy; tristructural isotropic; Nuclear Energy Advanced Modeling and Simulation

Citation Formats

van Rooyen, I. J., Yang, Y., Holesinger, T., Bachhav, Mukesh, and Fu, Z. Microstructure and Fission Product Distribution Examination in the UCO kernel of TRISO Fuel Particles. United States: N. p., 2018. Web.
van Rooyen, I. J., Yang, Y., Holesinger, T., Bachhav, Mukesh, & Fu, Z. Microstructure and Fission Product Distribution Examination in the UCO kernel of TRISO Fuel Particles. United States.
van Rooyen, I. J., Yang, Y., Holesinger, T., Bachhav, Mukesh, and Fu, Z. 2018. "Microstructure and Fission Product Distribution Examination in the UCO kernel of TRISO Fuel Particles". United States. https://www.osti.gov/servlets/purl/1478773.
@article{osti_1478773,
title = {Microstructure and Fission Product Distribution Examination in the UCO kernel of TRISO Fuel Particles},
author = {van Rooyen, I. J. and Yang, Y. and Holesinger, T. and Bachhav, Mukesh and Fu, Z.},
abstractNote = {The effect of irradiation and fabrication process on the UCO fuel kernel, kernel-buffer interlayer and fission products, has not been fully studied for UCO fuel kernels of TRISO coated particles. Specifically, the potential correlation(s) with fission product retention, composition and distribution within these structures for the tristructural isotropic (TRISO) fuel performance at normal and accident conditions, are not well reported in literature. Structural and chemical information in the irradiated UCO fuel kernel, e.g., the stoichiometry variations, may further contribute to fuel performance modeling under the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. The microstructural and micro-chemical evolution of selected irradiated UCO fuel kernels, kernel buffer interfaces and recoil zones were characterized using Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive Spectroscopy (EDS) elemental mapping. The fuel kernel of particles from Advanced Gas Reactor (AGR)-2 irradiated to 10.8% fissions per initial metal atom (FIMA), were examined with the following main findings: (1) large fission gas bubbles were mainly identified in the zirconium and molybdenum enriched but oxygen depleted phases in the center of fuel kernel, (2) significant inter-diffusion between the UCO fuel kernel and pyro-carbon buffer layer was observed as a high density of sub-micron sized carbon inclusions was identified at near the interface in the kernel side and some isolated UCO particles were located in the buffer layer, (3) pores filled with free carbon were also observed in the recoil zone specimen. Fuel kernels from two AGR-1 compacts irradiated to 11.4 and 17.4% FIMA respectively, were examined with the following main findings: (1) two primary phases consisting of a “high-Z (atomic mass)” UC(O) phase (rocksalt; a=0.496 nm) that also contained Zr, Mo, and/or Ru and a “low-Z” UO2(C) phase (fluorite structure; a = 0.547nm) in which trace amounts of I, Nd, Pr, and/or Er could be detected. This latter phase contained many precipitates of the “high-Z” phase. Conversely, this latter phase did not contain precipitates of the UO2-type material, (2) Xe bubbles were found almost exclusively in the “high-Z” phase and in the particular example shown, the Zr-containing variant. Further work in this area should address whether this potential Xe preference for just one of the high-Z phases is indeed a real effect.},
doi = {},
url = {https://www.osti.gov/biblio/1478773}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {10}
}

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