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Title: Microstructure and fission products in the UCO kernel of an AGR-1 TRISO fuel particle after post irradiation safety testing

Abstract

Tristructural isotropic (TRISO) coated particle fuel as a key fuel concept for the High Temperature Gas-cooled Reactors (HTGRs) and a candidate accident tolerant fuel (ATF) has been currently investigated under the US-DOE Advanced Gas Reactor (AGR) fuel development and qualification program. Over the past decades, extensive studies have been conducted to evaluate the fission product release, diffusion on Ag, Pd and Cd in the SiC layer and the TRISO coating system, and post-safety-test performance. However, to date, there are limited reported results on the fuel kernels’ response to irradiation with or without post irradiation high temperature annealing. To incrementally fulfill this knowledge gap extensive studies using transmission electron microscopes (TEM) and atom probe tomography (APT) were conducted on a TRISO fuel particle kernel with a 19.74% 235U enrichment, irradiated to 18.63% FIMA and subsequently subjected to post-safety testing at 1600ºC for 300 hours.. Microstructure characterizations, elemental analysis, and phase identification were conducted using conventional TEM and scanning TEM (STEM) imaging, energy-dispersive X-ray spectroscopy (EDS), selected-area electron diffraction (SAED) and atom probe tomography (APT). The following findings were made: (1) significant reconstructions and phase evolutions occurred in the irradiated and post-safety annealed fuel kernel, and its microstructure consists of two primarymore » phases, namely a “high-Z (atomic mass)” UC phase and a “low-Z” UO phase, (2) no fission gas bubbles are identified within the fuel kernel, that can be attributed to the high temperature post safety annealing, (3) fission products Zr, Nb, Mo, Ru, Tc and Rh were found to preferentially segregate into UC phase or to form metallic precipitates, while the lanthanide fission products tend to stay in the solution of UO phase, (4) Pd was detected in the rod-shaped precipitates, (5) APT data reveals segregation of Te, Pd, and Ag at the UO and UC phase boundary, and (6) Pd is detected in both the UO and UC phases but with an enrichment in the former one.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [2]; ORCiD logo [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  2. Univ. of Florida, Gainesville, FL (United States)
Publication Date:
Research Org.:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1618432
Report Number(s):
INL-JOU-18-51977-Rev000
Journal ID: ISSN 0022-3115
Grant/Contract Number:  
AC07-05ID14517
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 528; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Tristructural isotropic; High Temperature Gas-cooled Reactors; accident tolerant fuel

Citation Formats

Van Rooyen, Isabella J, Fu, Zhenyu, Yang, Yong, and Bachhav, Mukesh. Microstructure and fission products in the UCO kernel of an AGR-1 TRISO fuel particle after post irradiation safety testing. United States: N. p., 2019. Web. doi:10.1016/j.jnucmat.2019.151884.
Van Rooyen, Isabella J, Fu, Zhenyu, Yang, Yong, & Bachhav, Mukesh. Microstructure and fission products in the UCO kernel of an AGR-1 TRISO fuel particle after post irradiation safety testing. United States. https://doi.org/10.1016/j.jnucmat.2019.151884
Van Rooyen, Isabella J, Fu, Zhenyu, Yang, Yong, and Bachhav, Mukesh. 2019. "Microstructure and fission products in the UCO kernel of an AGR-1 TRISO fuel particle after post irradiation safety testing". United States. https://doi.org/10.1016/j.jnucmat.2019.151884. https://www.osti.gov/servlets/purl/1618432.
@article{osti_1618432,
title = {Microstructure and fission products in the UCO kernel of an AGR-1 TRISO fuel particle after post irradiation safety testing},
author = {Van Rooyen, Isabella J and Fu, Zhenyu and Yang, Yong and Bachhav, Mukesh},
abstractNote = {Tristructural isotropic (TRISO) coated particle fuel as a key fuel concept for the High Temperature Gas-cooled Reactors (HTGRs) and a candidate accident tolerant fuel (ATF) has been currently investigated under the US-DOE Advanced Gas Reactor (AGR) fuel development and qualification program. Over the past decades, extensive studies have been conducted to evaluate the fission product release, diffusion on Ag, Pd and Cd in the SiC layer and the TRISO coating system, and post-safety-test performance. However, to date, there are limited reported results on the fuel kernels’ response to irradiation with or without post irradiation high temperature annealing. To incrementally fulfill this knowledge gap extensive studies using transmission electron microscopes (TEM) and atom probe tomography (APT) were conducted on a TRISO fuel particle kernel with a 19.74% 235U enrichment, irradiated to 18.63% FIMA and subsequently subjected to post-safety testing at 1600ºC for 300 hours.. Microstructure characterizations, elemental analysis, and phase identification were conducted using conventional TEM and scanning TEM (STEM) imaging, energy-dispersive X-ray spectroscopy (EDS), selected-area electron diffraction (SAED) and atom probe tomography (APT). The following findings were made: (1) significant reconstructions and phase evolutions occurred in the irradiated and post-safety annealed fuel kernel, and its microstructure consists of two primary phases, namely a “high-Z (atomic mass)” UC phase and a “low-Z” UO phase, (2) no fission gas bubbles are identified within the fuel kernel, that can be attributed to the high temperature post safety annealing, (3) fission products Zr, Nb, Mo, Ru, Tc and Rh were found to preferentially segregate into UC phase or to form metallic precipitates, while the lanthanide fission products tend to stay in the solution of UO phase, (4) Pd was detected in the rod-shaped precipitates, (5) APT data reveals segregation of Te, Pd, and Ag at the UO and UC phase boundary, and (6) Pd is detected in both the UO and UC phases but with an enrichment in the former one.},
doi = {10.1016/j.jnucmat.2019.151884},
url = {https://www.osti.gov/biblio/1618432}, journal = {Journal of Nuclear Materials},
issn = {0022-3115},
number = C,
volume = 528,
place = {United States},
year = {2019},
month = {11}
}