On the melting of reactor core particle beds

Conference · Tue Dec 01 04:00:00 EST 1987

OSTI ID:5122261

Dosanjh, S S

During severe nuclear reactor accidents similar to Three-Mile Island, fragmentation of the fuel rods can convert the reactor core into a large rubble bed composed primarily of UO/sub 2/ and ZrO/sub 2/ particles. In the present study a one-dimensional model is developed for the melting and refreezing of such a bed. The analysis includes mass conservation equations for the species of interest (UO/sub 2/ and ZrO/sub 2/); a momentum equation that represents a balance among drag, capillary and gravity forces; an energy equation which incorporates the effects of convection by the melt, radiation and conduction through the bed and internal heat generation; and a UO/sub 2-ZrO/sub 2/ phase diagram. A few key results are that (1) capillary forces are only important in beds composed of particles smaller than a few millimeters in diameter and in such beds, melt relocates both upward and downward until it freezes, forming crusted regions above and below the melt zone; (2) as melt flows downward and freezes, a flow blockage forms near the bottom of the bed and the location of this blockage is determined by the bottom thermal boundary layer thickness; (3) the maximum thickness of the lower crust increases linearly with the height of the bed; and (4) deviations from intially uniform composition profiles occur because ZrO/sub 2/ is preferentially melted and these deviations decrease as the initial ZrO/sub 2/ concentration is increased.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5122261
• Report Number(s): SAND-87-2376C; CONF-880724-5; ON: DE88004683
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220900* -- Nuclear Reactor Technology-- Reactor Safety
ACCIDENTS
ACTINIDE COMPOUNDS
CHALCOGENIDES
ENERGY TRANSFER
HEAT TRANSFER
MATHEMATICAL MODELS
MELTDOWN
ONE-DIMENSIONAL CALCULATIONS
OXIDES
OXYGEN COMPOUNDS
POWER REACTORS
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTOR CORE DISRUPTION
REACTOR CORES
REACTORS
TRANSITION ELEMENT COMPOUNDS
URANIUM COMPOUNDS
URANIUM DIOXIDE
URANIUM OXIDES
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES