Interaction of uranium dioxide with molten zircaloy

Technical Report · Wed Apr 01 04:00:00 EST 1987

OSTI ID:6521795

Kim, Kyu Tae

Laboratory experiments in which gram quantities of molten Zircaloy were held in contact with UO/sub 2/ for known times (20 to 600 s) and temperatures (1900 - 2200/sup 0/C) were conducted. Sections were examined by optical microscopy, electron microprobe, scanning Auger microscopy, and X-ray fluorescence spectroscopy. In the first experiment, the molten metal was contained in a UO/sub 2/ crucible. The dissolution rate in this system was found to be dominated by natural convention in the melt driven by density gradients established by the dissolving uranium. The mechanism of the interaction also was observed to involve penetration and detachment of the grains of the oxide by the molten metal. Similar tests with single-crystal UO/sub 2/ specimens showed similar dissolution behavior. Less severe attach occurred because of the absence of grain boundaries, although subgrain boundaries or dislocations provided high-diffusivity pathways for preferential oxygen removal. In the third type of test, a disk of UO/sub 2/ was placed at the bottom of a ThO/sub 2/ crucible. This arrangement prevented establishment of unstable density gradients in the liquid phase, resulting in a purely diffusion-controlled interaction. A remarkable seven-region structure was observed in the quenched specimens. This structure could be explained by analysis of the quenching of the high-temperature interaction zone with the aid of the available ternary phase diagrams of the U-Zr-O system. The layers grew parabolically in time. The relevance of the data obtained to the melting on fuel pellets in a severe fuel damage accident was assessed.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6521795
• Report Number(s): LBL-23310; ON: DE87010987
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220900* -- Nuclear Reactor Technology-- Reactor Safety
ACCIDENTS
ACTINIDE COMPOUNDS
ALLOYS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CONVECTION
CORROSION
DIFFUSION
DISSOLUTION
ENERGY TRANSFER
FUEL ELEMENT FAILURE
HEAT TRANSFER
KINETICS
MASS TRANSFER
MELTING
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHASE TRANSFORMATIONS
REACTION KINETICS
REACTOR ACCIDENTS
THORIUM COMPOUNDS
THORIUM OXIDES
TIN ALLOYS
URANIUM COMPOUNDS
URANIUM DIOXIDE
URANIUM OXIDES
VERY HIGH TEMPERATURE
ZIRCALOY
ZIRCONIUM ALLOYS
ZIRCONIUM BASE ALLOYS