PYROLYTIC-CARBON-COATED CARBIDE FUEL PARTICLES AND THEIR USE IN GRAPHITE- MATRIX FUEL COMPACTS

Technical Report · Tue Oct 30 00:00:00 EST 1962

OSTI ID:4769881

Goeddel, W.V. ed.

A summary of the development and evaluation of pyrolytic-carbon-coated carbide fuel particles and graphitematrix fuel compacts is presented. A process that was developed for the preparation of particles of thorium-uranium dicarbide is described. Granulated particles composed of powdered UO/sub 2/, ThO/sub 2/, and carbon are suspended in a bed of graphite flour and heated to convert the oxides to dicarbides. The particles are then melted to densify and spheroidize them, while the graphite flour keeps them separated so they will not flow together. Coating the (Th, U)C/sub 2/ particles with pyrolytic carbon is accomplished in a fluidizedbed apparatus using a methane--helium mixture at a temperature of approximates 1400 deg C. Data are presented on the properties of coatings deposited at temperatures to 2400 deg C. Graphitematrix fuel compacts of high density are prepared by a hotpressing process. Graphfte flour is used as the filler and pitch as the binder; the use of graphite flour, rather than coke, permtts the attainment of good thermal properties In the compacts wtthout the necessity for high processing temperatures. The hot-pressing process is described and the properties of the compacts are given. The thermal stability of coated fuel particles was evaluated at temperatures to 2000 deg C and for times up to one year. Some coated particles were found to fail in thermal gradient tests because of the movement of the particle through the coating on the high- temperature side; this was named the amoeba effect.'' Tests of coated particles show that there should be no thermal instability at temperatures up to 1500 deg C for periods of at least three years. Results of extensive irradiation tests of graphite-matrix fuel compacts prepared by the hot-pressing process are presented. The compacts containing uncoated (Th, U)C/sub 2/ particles were dimensionally stable after burnups of 6.9 x 10/sup 19/ fissions/cm/sup 3/ at 1100 to 1500 deg C. Compacts cortaining coated particles were tested to burnups of 1.2 x 10/sup 20/ fissions/cm/sup 3/ at temperatures as high as 2000 deg C. A few per cent of the particle coatings were found to be broken after these tests. Possible explanations for these failures are presented. (auth)

• Research Organization: General Atomic Div., General Dynamics Corp., San Diego, Calif.
• DOE Contract Number: AT(04-3)-314
• NSA Number: NSA-17-001929
• OSTI ID: 4769881
• Report Number(s): GA-3588
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-63
• Country of Publication: United States
• Language: English

Related Subjects

METALS, CERAMICS, AND OTHER MATERIALS
AMOEBA
BURNUP
CARBIDES
CARBON
CEMENTS
COATING
COMPACTING
DENSITY
FAILURES
FISSION
FUELS
GRAPHITE
HEATING
HELIUM
HIGH TEMPERATURE
HOT WORKING
IRRADIATION
LABORATORY EQUIPMENT
MATERIALS TESTING
MECHANICAL PROPERTIES
MELTING
METHANE
MICROORGANISMS
POWDERS
PREPARATION
PYROLYSIS
SOLUTIONS
SPHERES
STABILITY
TENSILE PROPERTIES
THERMODYNAMICS
THORIUM ALLOYS
URANIUM CARBIDES
USES