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Title: Fabrication and Characterization of Surrogate TRISO Particles Using 800μm ZrO 2 Kernels

Abstract

In support of fully ceramic microencapsulated (FCM) fuel development, coating development work is ongoing at Oak Ridge National Laboratory (ORNL) to produce tri-structural isotropic (TRISO) coated fuel particles with both UN kernels and surrogate (uranium-free) kernels. The nitride kernels are used to increase fissile density in these SiC-matrix fuel pellets with details described elsewhere. The surrogate TRISO particles are necessary for separate effects testing and for utilization in the consolidation process development. This report focuses on the fabrication and characterization of surrogate TRISO particles which use 800μm in diameter ZrO 2 microspheres as the kernel.

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE), Fuel Cycle Technologies (NE-5). Advanced Fuels Campaign
OSTI Identifier:
1325475
Report Number(s):
ORNL/LTR-2016/315
AF5810000; NEAF278; TRN: US1700077
DOE Contract Number:
AC05-00OR22725
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; ACCIDENT-TOLERANT NUCLEAR FUELS; ZIRCONIUM OXIDES; SILICON CARBIDES; URANIUM NITRIDES; COATED FUEL PARTICLES; FABRICATION; FUEL PELLETS; CERAMICS; MATRIX MATERIALS; MICROSPHERES; TESTING

Citation Formats

Jolly, Brian C., Helmreich, Grant, Cooley, Kevin M., Dyer, John, and Terrani, Kurt. Fabrication and Characterization of Surrogate TRISO Particles Using 800μm ZrO2 Kernels. United States: N. p., 2016. Web. doi:10.2172/1325475.
Jolly, Brian C., Helmreich, Grant, Cooley, Kevin M., Dyer, John, & Terrani, Kurt. Fabrication and Characterization of Surrogate TRISO Particles Using 800μm ZrO2 Kernels. United States. doi:10.2172/1325475.
Jolly, Brian C., Helmreich, Grant, Cooley, Kevin M., Dyer, John, and Terrani, Kurt. 2016. "Fabrication and Characterization of Surrogate TRISO Particles Using 800μm ZrO2 Kernels". United States. doi:10.2172/1325475. https://www.osti.gov/servlets/purl/1325475.
@article{osti_1325475,
title = {Fabrication and Characterization of Surrogate TRISO Particles Using 800μm ZrO2 Kernels},
author = {Jolly, Brian C. and Helmreich, Grant and Cooley, Kevin M. and Dyer, John and Terrani, Kurt},
abstractNote = {In support of fully ceramic microencapsulated (FCM) fuel development, coating development work is ongoing at Oak Ridge National Laboratory (ORNL) to produce tri-structural isotropic (TRISO) coated fuel particles with both UN kernels and surrogate (uranium-free) kernels. The nitride kernels are used to increase fissile density in these SiC-matrix fuel pellets with details described elsewhere. The surrogate TRISO particles are necessary for separate effects testing and for utilization in the consolidation process development. This report focuses on the fabrication and characterization of surrogate TRISO particles which use 800μm in diameter ZrO2 microspheres as the kernel.},
doi = {10.2172/1325475},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 7
}

Technical Report:

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  • Zirconium carbide is a candidate to either replace or supplement silicon carbide as a coating material in TRISO fuel particles for high temperature gas-cooled reactor fuels. Six sets of ZrC coated surrogate microsphere samples, fabricated by the Japan Atomic Energy Agency using the fluidized bed chemical vapor deposition method, were irradiated in the High Flux Isotope Reactor at the Oak Ridge National Laboratory. These developmental samples available for the irradiation experiment were in conditions of either as-fabricated coated particles or particles that had been heat-treated to simulate the fuel compacting process. Five sets of samples were composed of nominally stoichiometricmore » compositions, with the sixth being richer in carbon (C/Zr = 1.4). The samples were irradiated at 800 and 1250 C with fast neutron fluences of 2 and 6 dpa. Post-irradiation, the samples were retrieved from the irradiation capsules followed by microstructural examination performed at the Oak Ridge National Laboratory's Low Activation Materials Development and Analysis Laboratory. This work was supported by the US Department of Energy Office of Nuclear Energy's Advanced Gas Reactor program as part of International Nuclear Energy Research Initiative collaboration with Japan. This report includes progress from that INERI collaboration, as well as results of some follow-up examination of the irradiated specimens. Post-irradiation examination items included microstructural characterization, and nanoindentation hardness/modulus measurements. The examinations revealed grain size enhancement and softening as the primary effects of both heat-treatment and irradiation in stoichiometric ZrC with a non-layered, homogeneous grain structure, raising serious concerns on the mechanical suitability of these particular developmental coatings as a replacement for SiC in TRISO fuel. Samples with either free carbon or carbon-rich layers dispersed in the ZrC coatings experienced negligible grain size enhancement during both heat treatment and irradiation. However, these samples experienced irradiation induced softening similar to stoichiometric ZrC samples.« less
  • This document is a compilation of the characterization data for the TRISO-coated surrogate particle batch designated ZrO2-500-AK2 that was produced at Oak Ridge National Laboratory (ORNL) as part of the Advanced Gas Reactor Fuel Development and Qualification (AGR) program. The ZrO2-500-AK2 material contains nominally 500 {micro}m kernels of yttria-stabilized zirconia (YSZ) coated with all TRISO layers (buffer, inner pyrocarbon, silicon carbide, and outer pyrocarbon). The ZrO2-500-AK2 material was created for: (1) irradiation testing in the High Flux Isotope Reactor (HFIR) and (2) limited dissemination to laboratories as deemed appropriate to the AGR program. This material was created midway into amore » TRISO fuel development program to accommodate a sudden opportunity to perform irradiation testing on surrogate material. While the layer deposition processes were chosen based on the best technical understanding at the time, technical progress at ORNL has led to an evolution in the perceived optimal deposition conditions since the createion of ZrO2-500-AK2. Thus, ZrO2-500-AK2 contains a reasonable TRISO microstructure, but does differ significanly from currently produced TRISO surrogates and fuel at ORNL. In this document, characterization data of the ZrO2-500-AK2 surrogate includes: size, shape, coating thickness, and density.« less
  • This document is a compilation of the characterization data for the TRISO-coated surrogate particles designated ZrO2-500-AK2 that was produced at Oak Ridge National Laboratory (ORNL) as part of the Advanced Gas Reactor Fuel Development and Qualification (AGR) program. The ZrO2-500-AK2 material contains nominally 500 {micro}m kernels of yttria-stabilized zirconia (YSZ) coated with all TRISO layers (buffer, inner pyrocarbon, silicon carbide, and outer pyrocarbon). The ZrO2-500-AK2 material was created for: (1) irradiation testing in the High Flux Isotope Reactor (HFIR) and (2) limited dissemination to laboratories as deemed appropriate to the AGR program. This material was created midway into a TRISOmore » fuel development program to accommodate a sudden opportunity to perform irradiation testing on surrogate material. While the layer deposition processes were chosen based on the best technical understanding at the time, technical progress at ORNL has led to an evolution in the perceived optimal deposition conditions since the creation of ZrO2-500-AK2. Thus, ZrO2-500-AK2 contains a reasonable TRISO microstructure, but does differ significantly from currently produced TRISO surrogates and fuel at ORNL. In this document, characterization data of the ZrO2-500-AK2 surrogate includes: size, shape, coating thickness, and density.« less
  • INL readiness review assessment of BWXT readiness to commence fabrication of low-enriched TRISO coated fuel particles for the AGR-5/6/7 irradiation experiments. BWXT self-identified equipment issues preventing operation. INL identified two findings. The first was that disposition codes had not been assigned and documented on BWXT forms to ensure that off-specification materials could not be used in the fabrication of TRISO particles. The second was that chemical purity specifications were not reliably passed on to chemical suppliers, which resulted in the receipt of one acetylene cylinder with suspect impurity levels.