Initial examination of fuel compacts and TRISO particles from the US AGR-2 irradiation test

John D. Hunn; Charles A. Baldwin; Fred C. Montgomery; Tyler J. Gerczak; Robert N. Morris; Grant W. Helmreich; Paul A. Demkowicz; Jason M. Harp; John D. Stempien

doi:10.1016/j.nucengdes.2017.09.017

Initial examination of fuel compacts and TRISO particles from the US AGR-2 irradiation test

John D. Hunn, Charles A. Baldwin, Fred C. Montgomery, Tyler J. Gerczak, Robert N. Morris, Grant W. Helmreich, Paul A. Demkowicz, Jason M. Harp, John D. Stempien

Particle Fuel Forms

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34 Scopus citations

Abstract

Post-irradiation examination was completed on two as-irradiated compacts from the US Advanced Gas Reactor Fuel Development and Qualification Program's second irradiation test. These compacts were selected for examination because there were indications that they may have contained particles that released cesium through a failed or defective SiC layer. The coated particles were recovered from these compacts by electrolytic deconsolidation of the surrounding graphitic matrix in nitric acid. The leach-burn-leach (LBL) process was used to dissolve and analyze exposed metallic elements (actinides and fission products), and each particle was individually surveyed for relative cesium retention with the Irradiated Microsphere Gamma Analyzer (IMGA). Data from IMGA and LBL examinations provided information on fission product release during irradiation and whether any specific particles had below-average retention that could be related to coating layer defects or radiation-induced degradation. A few selected normal-retention particles and six with abnormally-low cesium inventory were analyzed using X-ray tomography to produce three-dimensional images of the internal coating structure. Four of the low-cesium particles had obviously damaged or degraded SiC, and X-ray imaging was able to guide subsequent grinding and polishing to expose the regions of interest for analysis by optical and electron microscopy. Additional particles from each compact were also sectioned and examined to study the overall radiation-induced microstructural changes in the kernel and coating layers.

Original language	English
Pages (from-to)	89-101
Number of pages	13
Journal	Nuclear Engineering and Design
Volume	329
DOIs	https://doi.org/10.1016/j.nucengdes.2017.09.017
State	Published - Apr 1 2018

Funding

This work was sponsored by the U.S. Department of Energy, Office of Nuclear Energy, through the Idaho National Laboratory Advanced Reactor Technologies Technology Development Office as part of the Advanced Gas Reactor Fuel Development and Qualification Program. Analysis of leach solutions was provided by the ORNL Nuclear Analytical Chemistry & Isotopics Laboratory. Hot cell activities were supported by the staff of the ORNL Irradiated Fuels Examination Laboratory and the INL Hot Fuel Examination Facility.

Funders	Funder number
Advanced Gas Reactor Fuel Development and Qualification Program
Idaho National Laboratory Advanced Reactor Technologies Technology Development Office
U.S. Department of Energy
Office of Nuclear Energy
Oak Ridge National Laboratory

Keywords

Cesium release
High-temperature gas-cooled reactor (HTGR) fuel
Post-irradiation examination (PIE)
SiC failure
Tristructural isotropic (TRISO) particles

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10.1016/j.nucengdes.2017.09.017

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title = "Initial examination of fuel compacts and TRISO particles from the US AGR-2 irradiation test",

abstract = "Post-irradiation examination was completed on two as-irradiated compacts from the US Advanced Gas Reactor Fuel Development and Qualification Program's second irradiation test. These compacts were selected for examination because there were indications that they may have contained particles that released cesium through a failed or defective SiC layer. The coated particles were recovered from these compacts by electrolytic deconsolidation of the surrounding graphitic matrix in nitric acid. The leach-burn-leach (LBL) process was used to dissolve and analyze exposed metallic elements (actinides and fission products), and each particle was individually surveyed for relative cesium retention with the Irradiated Microsphere Gamma Analyzer (IMGA). Data from IMGA and LBL examinations provided information on fission product release during irradiation and whether any specific particles had below-average retention that could be related to coating layer defects or radiation-induced degradation. A few selected normal-retention particles and six with abnormally-low cesium inventory were analyzed using X-ray tomography to produce three-dimensional images of the internal coating structure. Four of the low-cesium particles had obviously damaged or degraded SiC, and X-ray imaging was able to guide subsequent grinding and polishing to expose the regions of interest for analysis by optical and electron microscopy. Additional particles from each compact were also sectioned and examined to study the overall radiation-induced microstructural changes in the kernel and coating layers.",

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Initial examination of fuel compacts and TRISO particles from the US AGR-2 irradiation test

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Keywords

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