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GSI-191 PWR Sump Screen Blockage Chemical Effects Tests: Thermodynamic Simulations (NUREG/CR-6912)On this page: Download complete document The following links on this page are to documents in Adobe Portable Document Format (PDF). See our Plugins, Viewers, and Other Tools page for more information. For successful viewing of PDF documents on our site please be sure to use the latest version of Adobe. Publication InformationManuscript Completed: November 2006 Prepared by Center for Nuclear Waste Regulatory Analyses B.P. Jain, NRC Project Manager Prepared for AbstractThis report summarizes chemical modeling studies and experiments performed to support the
resolution of GSI–191. Along with entrained debris components, the formation of secondary
precipitates and gels have the potential to impede the performance of Emergency Core Cooling
System pumps, Containment Spray System pumps, or other components downstream of the
sump strainer after a loss-of-coolant accident (LOCA). The purpose of this study was to
examine the use of chemical modeling software as a tool in predicting whether secondary
precipitates would be likely to form in specific post-LOCA chemical environments. Within the
limits of the available thermodynamic data for the model, the software also identified which
solids would be expected to form and their quantities, and it indicated how the containment
water chemistry was affected by these reactions. Several existing, widely available chemical
modeling programs—EQ3/6 (Lawrence Livermore National Laboratory, 1995), OLI Systems
StreamAnalyzer (OLI Systems, Inc., 2005), The Geochemist's Workbench® REACT (RockWare,
Inc., 2004), and PHREEQC (U.S. Geological Survey, 2003)—and their accompanying
thermodynamic database files were evaluated to simulate the potential formation of precipitates
under post-LOCA conditions. Detailed simulations were performed for five representative post-
LOCA environments, in which alkaline or neutral borated containment waters interacted with
metals, concrete, and insulation materials at 60 °C [140 °F] for times up to 720 hours. The
modeled conditions corresponded to the Integrated Chemical Effects Test (ICET) experiments
conducted at the University of New Mexico, and results of the experiments were used to
benchmark and calibrate the simulations. The input water compositions for the simulations
were estimated from specified initial containment water compositions, previously derived
corrosion rates for the metals of interest, and dissolution rates from new experiments involving
insulation materials and concrete. The modeling programs EQ3/6 and PHREEQC were used to
perform blind predictions of the experiment results. Analytical data and qualitative observations
of precipitation (or lack of it) from the ICET experiments were used to refine the conceptual The study determined that the most important requirements for developing more accurate
chemical effects simulations were (i) a realistic estimate of starting water compositions and
dissolution rates, and (ii) the availability of an adequate set of thermodynamic data, particularly
for amorphous or metastable solids that would be expected to form under the simulated
conditions. The study concluded that the codes as tested were broadly useful in assessing |
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