United States Nuclear Regulatory Commission - Protecting People and the Environment

Knowledge Base Report on Emergency Core Cooling Sump Performance in Operating Light Water Reactors (NUREG/CR-7172)

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Publication Information

Manuscript Completed: April 2013
Date Published: January 2014

Prepared by:
K. Natesan, A. Moisseytsev, C. Bahn, and D. R. Diercks
Argonne National Laboratory
9700 S. Cass Avenue
Argonne, IL 60439

C. Shaffer
ARES Corporation
851 University Blvd., SE, Ste 100
Albuquerque, NM 87106

John Burke, NRC Project Manager

NRC Job Code N6954

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

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Abstract

This report describes the current status of the knowledge base regarding the performance of long-term core and containment cooling in operating light water reactors. The report discusses the substantial knowledge that has been amassed as a result of the research on clogging issues related to the suction strainers in boiling water reactors (BWRs) and the sump strainers in pressurized water reactors (PWRs). These issues concern the potential insulation and other debris generated in the event of a postulated loss-of-coolant accident within the containment of a light water reactor and the subsequent transport to and accumulation on the recirculation strainers. This debris accumulation could potentially challenge the plant's capability to provide adequate long-term cooling water to the pumps in the emergency core cooling and in the containment spray systems.

The report briefly discusses the historical background on the sump performance issue and presents the NRC regulatory considerations, with emphasis on guidance provided by NRC to the licensees during recent years. The report presents the current state-of-the-art resolution methodology for understanding the strainer blockage phenomena and processes that have evolved over the years. In particular, the report discusses the details of plant-by-plant licensee responses to the NRC Bulletin 2003-01 and the NRC Generic Letter 2004-02. The licensee responses were collected in several areas such as strainer characteristics, physical and plant modifications, head loss testing procedures, head loss test information, net positive suction head data, debris generation, debris characteristics, coating debris, chemical effects, downstream effects, etc. as well as assessment of net positive suction head requirements and availability.

The report is designed to serve as a source of updated information from the previous reports (Rao et al. 2001, NUREG/CR-6808) on all aspects of issues concerning the emergency core cooling sump performance in both BWRs and PWRs.

Page Last Reviewed/Updated Monday, September 29, 2014