United States Nuclear Regulatory Commission - Protecting People and the Environment

GSI-191 Technical Assessment: Summary and Analysis of U.S. Pressurized Water Reactor Industry Survey Responses and Responses to GL 97-04 (NUREG/CR-6762, Volume 2)

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Publication Information

Manuscript Completed: August 2001
Date Published: August 2002

Prepared by:
D. V. Rao, B. C. Letellier, K. W. Ross*
L. S. Bartlein, M. T. Leonard**

Los Alamos National Laboratory
Los Alamos, NM 87545

Subcontractors:
*OMICRON
2500 Louisiana N.E.
Albuquerque, NM 87110

**dycoda LLC
70 Andres Sanchez Road
Belen, NM 87002

M. L. Marshall, NRC Project Manager

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

NRC Job Code Y6041

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Abstract

This report documents the findings of a survey of operating U. S. pressurized water reactors (PWR) plants that was conducted, as part of the resolution of the Nuclear Regulatory Commission (NRC) Generic-Safety-Issue (GSI) 191, to compile plant specific data relative to the resolution of GSI-191. The purpose of the GSI-191 study is to determine if the transport and accumulation of debris in a containment following a loss-of-coolant accident (LOCA) will impede the operation of the ECCS in operating PWRs. In the event of a LOCA within the containment of a PWR, thermal insulation and other materials in the vicinity of the break will be damaged and dislodged. A fraction of this material would be transported to the recirculation (or emergency) sump and accumulate on the screen thereby forming a debris bed. Excessive head loss across this bed could prevent or impede the flow of water into the core or containment.

A set of questions designed to obtain needed plant specific information was formulated and forwarded to the licensees of all operating US PWRs. The questions asked for the details regarding specific design features (e.g., sump design), sources of debris, and thermal hydraulic data (e.g., sump flooding levels). The responses to GL 97-04, "Assurance of Sufficient Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal Pumps," provided additional information important to the assessment of PWR recirculation sump performance (e.g., pump flow rates). The responses to these questions were reviewed, compiled, and summarized in this report.

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