United States Nuclear Regulatory Commission - Protecting People and the Environment

Characterization and Head-Loss Testing of Latent Debris from Pressurized-Water-Reactor Containment Buildings (NUREG/CR-6877)

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Publication Information

Manuscript Completed: August 2004
Date Published: July 2005

Principal Investigator: B.C. Letellier

Prepared by:
M. Ding 1, A. Abdel-Fattah 1, S. Fisher1 , B.C. Letellier1
K. Howe2, J. Garcia 2
C.J. Shaffer 3

Principal Contractor:
1Los Alamos National Laboratory
Los Alamos, NM 87545
2University of New Mexico
Department of Civil Engineering
Albuquerque, NM 87110

3ARES Corporation
Albuquerque, NM 87106

T. Y. Chang, 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

Availability Notice


To properly evaluate the performance of a pressurized water reactor (PWR) emergency core cooling system (ECCS) containment recirculation capability, it is necessary to estimate the total amount of debris that may be present in the containment pool during the recirculation phase. To be as accurate as possible, it is important to include a reasonable estimate of the latent dirt and foreign material that can be found in containment, in addition to the debris generated by a highpressure pipe rupture. Past and recent testing has shown that even small volumes of fibrous debris present on an ECCS sump screen can filter particulates present in the sump pool very effectively, leading to the formation of composite debris beds that can produce significant pressure losses. Debris present during routine operations that is subjected to containment spray and pool transport may be a significant contribution to the particulates and/or fiber material that compose the sump screen debris bed.

To investigate the significance of this issue, the United States (U.S.) Nuclear Regulatory Commission (NRC) directed Los Alamos National Laboratory (LANL) to characterize the material composition and the hydraulic flow properties of actual plant debris samples.

This study was performed from August 2003 to June 2004. The purpose of the study was to quantify parameters critical to the proper application of the NUREG/CR-6224 head-loss correlation, such as specific surface area. Microfiltering, optical microscopy, and organic dissolution chemistry tests were performed to fractionate the fibrous and particulate components. Most tests were performed at the geochemistry laboratory of the Isotope and Nuclear Chemistry Facility at LANL, which has the necessary analytic equipment to make direct measurements of the hydraulic flow properties and to handle potential low-level radioactive waste streams. Hydraulic parameters representative of latent particulates were measured by testing larger quantities of surrogate debris in a vertical-flow test loop at the University of New Mexico. In addition to our attempt to provide the first quantitative characterization of PWR latent debris properties, this study provides a model of participation and cooperation between the US PWR industry and the NRC. Five volunteer plants contributed samples collected during their recent condition assessment surveys. Descriptions of test procedures and quantitative results are provided in the applicable sections of this report.

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