Convective cooling of simulated core debris beds

Natural convection within simulated core debris beds has been experimentally investigated. The effect of heating method, viz., direct, Joule, or bottom heating on bed behavior has been examined and found to be extremely important. For directly heated beds, variations of the downward power fractions and Nusselt numbers with bed loading, heating rate, particle size, overlying fluid layer height and top surface boundary condition have been determined. Velocity and temperature profiles within the bed and overlying fluid have been determined using particle tracing techniques and Mach-Zehnder interferometry. These data have been compared with the predictions of the transient three-dimensional natural convection computer code COMMIX-1A with the aim of validating the code for debris bed applications. (orig.)