Evaluation of severe accident risks: Quantification of major input parameters

This report records part of the vast amount of information received during the expert judgment elicitation process that took place in support of the NUREG-1150 effort sponsored by the U.S. Nuclear Regulatory Commission. The results of the Containment Loads and Molten Core/Containment Interaction Expert Panel Elicitation are presented in this part of Volume 2 of NUREG/CR-4551. The Containment Loads Expert Panel considered seven issues: (1) hydrogen phenomena at Grand Gulf; (2) hydrogen burn at vessel breach at Sequoyah; (3) BWR reactor building failure due to hydrogen; (4) Grand Gulf containment loads at vessel breach; (5) pressure increment in the Sequoyah containment at vessel breach; (6) loads at vessel breach: Surry; and (7) pressure increment in the Zion containment at vessel breach. The report begins with a brief discussion of the methods used to elicit the information from the experts. The information for each issue is then presented in five sections: (1) a brief definition of the issue, (2) a brief summary of the technical rationale supporting the distributions developed by each of the experts, (3) a brief description of the operations that the project staff performed on the raw elicitation results in order to aggregate the distributions, (4) the aggregated distributions, and (5) the individual expert elicitation summaries. The Molten Core/Containment Interaction Panel considered three issues. The results of the following two of these issues are presented in this document: (1) Peach Bottom drywell shell meltthrough; and (2) Grand Gulf pedestal erosion. 89 figs., 154 tabs.