This report describes results of the drywell debris transport study. The objective of this study is to develop a methodology for estimating fraction of LOCA generated fibrous insulation debris that would be transported from the location of their generation in the drywell to the suppression pool. The study decomposed the problem into several components that were amenable to resolution by the knowledge base that can be developed from separate effects experiments, analytical modeling, and engineering calculations. Experiments and analytical studies were undertaken to compile the necessary knowledge base on debris transport during blowdown, washdown of debris by ECCS water flow, and debris sedimentation on the drywell floor. Logic charts were used to link both experimental and analytical results. The results of the study were used to delineate plant features and transport phenomena that dominate debris transport in the BWR drywell. A separate logic chart was developed for each postulated accident senario and genetic plant type analyzed. The logic charts can be modified to take into account effects of the plant-specific features. The overall method is comprehensible to engineers who are not exports in the subject of debris transport. Also, it is sufficiently flexible that new evidence and assumptions, related to debris size and distribution, can be easily accommodated.


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