Cooling of Debris Beds

The dependence of the dryout heat flux for volume-heated particulate beds on bed height (40cm), particle diameter (0.06 to 16 mm), stratification and boundary conditions (saturated and subcooled liquid, adiabatic and cooled bottom and sidewalls) has been determined for water and Freon-113. Channel penetration through subcooled layers and “downward boiling”  due to capillarity effects have been observed. Different types of bed disturbances have been identified, and their effect on dryout has been studied. Using existing theoretical models, which have been verified by the experiments, the upper limit of the thermal load on support structures has been calculated as a function of the particle size and bottom temperature for reactor accident conditions (Pu/U-oxide particles in sodium).