Drywell Debris Transport Study (NUREG/CR-6369, Volume 1)

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Publication Information

Manuscript Completed: February 1998
Date Published: September 1999

Prepared by:
D. V. Rao, C. Shaffer, E. Haskin

Science and Engineering Associates, Inc.
6100 Uptown Blvd. NE
Albuquerque, NM 87110

Prepared for:
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code W6325

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Abstract

This report describes results of the drywell debris transport study. The objective of the 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 scenario and generic 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 experts 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.