Developments of models for boiling and dryout in LWR debris beds: Chapter 15

The coolability of solid self-heated fuel debris in water is a topic of major interest in probabilistic safety analyses of light water reactors. Many experiments have been undertaken using simulant heating methods and simulant materials for the particulate, to investigate the dependence of the dryout heat flux (i.e. that heating rate at which liquid coolant is no longer able to adequately penetrate the debris bed, such that local temperatures may rise considerably in excess of the coolant's boiling point). The paper considers further developments and applications of these models. The particular topics discussed are (i) the transient approach to dryout for deep beds, (ii) the effect of a gradation in particulate size (i.e. the mean particle diameter varies with position in the bed), and (iii) the inclusion of a dried out layer in a one-dimensional model