Associations of Pd, U and Ag in the SiC layer of neutron-irradiated TRISO fuel

TM Lillo, IJ Van Rooyen - Journal of Nuclear Materials, 2015 - Elsevier
TM Lillo, IJ Van Rooyen
Journal of Nuclear Materials, 2015Elsevier
Abstract Knowledge of the associations and composition of fission products in the neutron
irradiated SiC layer of high-temperature gas reactor TRISO fuel is important to the
understanding of various aspects of fuel performance that presently are not well understood.
Recently, advanced characterization techniques have been used to examine fuel particles
from the Idaho National Laboratory's AGR-1 experiment. Nano-sized Ag and Pd precipitates
were previously identified in grain boundaries and triple points in the SiC layer of irradiated …
Abstract
Knowledge of the associations and composition of fission products in the neutron irradiated SiC layer of high-temperature gas reactor TRISO fuel is important to the understanding of various aspects of fuel performance that presently are not well understood. Recently, advanced characterization techniques have been used to examine fuel particles from the Idaho National Laboratory’s AGR-1 experiment. Nano-sized Ag and Pd precipitates were previously identified in grain boundaries and triple points in the SiC layer of irradiated TRISO nuclear fuel. Continuation of this initial research is reported in this paper and consists of the characterization of a relatively large number of nano-sized precipitates in three areas of the SiC layer of a single irradiated TRISO nuclear fuel particle using standardless EDS analysis on focused ion beam-prepared transmission electron microscopy samples. Composition and distribution analyses of these precipitates, which were located on grain boundaries, triple junctions and intragranular precipitates, revealed low levels, generally <10 atomic %, of palladium, silver and/or uranium with palladium being the most common element found. Palladium by itself, or associated with either silver or uranium, was found throughout the SiC layer. A small number of precipitates on grain boundaries and triple junctions were found to contain only silver or silver in association with palladium while uranium was always associated with palladium but never found by itself or in association with silver. Intergranular precipitates containing uranium were found to have migrated ∼23 μm along a radial direction through the 35 μm thick SiC coating during the AGR-1 experiment while silver-containing intergranular precipitates were found at depths up to ∼24 μm in the SiC layer. Also, Pd-rich, nano-precipitates (∼10 nm in diameter), without evidence for the presence of either Ag or U, were revealed in intragranular regions throughout the SiC layer. Because not all grain boundaries and triple junctions contained precipitates with fission products and/or uranium, along with the differences in migration behavior between Pd, Ag and U, it was concluded that crystallographic grain boundary and triple junction parameters likely influence migration behavior.
Elsevier
以上显示的是最相近的搜索结果。 查看全部搜索结果