Migration of ThO/sub 2/ kernels under the influence of a temperature gradient

Technical Report · Mon Nov 01 04:00:00 EST 1976

DOI:https://doi.org/10.2172/7129433· OSTI ID:7129433

Smith, C. L.

BISO coated ThO/sub 2/ fertile fuel kernels will migrate up the thermal gradients imposed across coated particles during HTGR operation. Thorium dioxide kernel migration has been studied as a function of temperature (1300 to 1700/sup 0/C) and ThO/sub 2/ kernel burnup (0.9 to 5.8 percent FIMA) in out-of-pile, postirradiation thermal gradient heating experiments. The studies were conducted to obtain descriptions of migration rates that will be used in core design studies to evaluate the impact of ThO/sub 2/ migration on fertile fuel performance in an operating HTGR and to define characteristics needed by any comprehensive model describing ThO/sub 2/ kernel migration. The kinetics data generated in these postirradiation studies are consistent with in-pile data collected by investigators at Oak Ridge National Laboratory, which supports use of the more precise postirradiation heating results in HTGR core design studies. Observations of intergranular carbon deposits on the cool side of migrating kernels support the assumption that the kinetics of kernel migration are controlled by solid state diffusion within irradiated ThO/sub 2/ kernels. The migration is characterized by a period of no migration (incubation period) followed by migration at the equilibrium rate for ThO/sub 2/. The incubation period decreases with increasing temperature and kernel burnup. The improved understanding of the kinetics of ThO/sub 2/ kernel migration provided by this work will contribute to an optimization of HTGR core design and an increased confidence in fuel performance predictions.

• Research Organization: General Atomic Co., San Diego, CA (USA)
• DOE Contract Number: E(04-3)-0167-PRJ-17
• OSTI ID: 7129433
• Report Number(s): GA-A-14058
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
210300* -- Power Reactors
Nonbreeding
Graphite Moderated
ACTINIDE COMPOUNDS
AMOEBA EFFECT
BURNUP
CHALCOGENIDES
COATED FUEL PARTICLES
FUEL PARTICLES
GAS COOLED REACTORS
GRAPHITE MODERATED REACTORS
HTGR TYPE REACTORS
OXIDES
OXYGEN COMPOUNDS
REACTORS
TEMPERATURE DEPENDENCE
TEMPERATURE GRADIENTS
THORIUM COMPOUNDS
THORIUM OXIDES