Post-accident core retention for LMFBR's. 2. Technical report, 1 July 1973--30 June 1974

This report describes work performed at UCLA on Post Accident Heat Removal for the period July 1973 to July 1974. The work includes a preliminary identification of sequences of events that could lead to a completely disassembled core and analysis of several in-vessel processes relevant to establishing whether or not containment can be achieved. Preliminary observations on the dry-out of debris beds are reported. The effects of both stabilizing temperature gradients and thermal radiation on increases in the downward heat transfer from a molten layer of UO2 are found to be significant. Boiling of the molten layer is considered and the existing experimental data is found to be inadequate. Predictions of heat transfer from a downward facing surface to a low Prandtl number fluid are not available. Recommendations for future work are made. The effects of disturbances on a quiescent molten layer are presented. A simple fast method of estimating recriticality is given and an estimate of possible ramp rates is made. Areas of uncertainty requiring further work are identified. (U.S.)