The following report serves as a formal introduction to the water-based Natural convection Shutdown heat removal Test Facility (NSTF) program at Argonne. Since 2005, this US Department of Energy (DOE) sponsored program has conducted large scale experimental testing to generate high-quality and traceable validation data for guiding design decisions of the Reactor Cavity Cooling System (RCCS) concept for advanced reactor designs.The most recent facility iteration, and focus of this report, is the operation of a 1 /2 scale model of a water-RCCS concept. Several features of the NSTF prototype align with the conceptual design that has been publicly released for the AREVA 625 MW t SC-HTGR. The design of the NSTF also retains all aspects common to a fundamental boiling water thermosiphon, and thus is well poised to provide necessary experimental data to advance basic understanding of natural circulation phenomena and contribute to computer code validation. Overall, the NSTF program operates to support the DOE vision of aiding US vendors in design choices of future reactor concepts, advancing the maturity of codes for licensing, and ultimately developing safe and reliable reactor technologies.In this report, the top-level program objectives, testing requirements, and unique considerations for the water cooled test assembly are discussed, and presented in sufficient depth to support defining the program's overall scope and purpose. A discussion of the proposed 6-year testing program is then introduced, which outlines the specific strategy and testing plan for facility operations. The proposed testing plan has been developed to meet the toplevel objective of conducting high-quality test operations that span across a broad range of single-and two-phase operating conditions. Details of characterization, baseline test cases, accident scenario, and parametric variations are provided, including discussions of later-stage test cases that examine the influence of geometric variations and off-normal configurations.The facility design follows, including as-built dimensions and specifications of the various mechanical and liquid systems, design choices for the test section, water storage tank, and network piping. Specifications of the instrumentation suite are then presented, along with specific information on performance windows, measurement uncertainties, and installation locations. Finally, descriptions of the control systems and heat removal networks are provided, which have been engineered to support precise quantification of energy balances and facilitate well-controlled test operations.

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Impact of 33% break initiated at t=57.6min. Average riser ∆T saw a 7.4 • C rise . . . 191 Impact of 33% break initiated at t=57.6min. Average riser heat flux saw a -9.33%

The Natural convection Shutdown heat removal Test Facility (NSTF) at Argonne National Laboratory (Argonne) was built to study the performance of passive safety systems for advanced nuclear reactors. It is a large-scale thermal hydraulics test facility designed to carry out highly instrumented experiments to validate the performance of Reactor Cavity Cooling System (RCCS) concepts for reactor decay heat removal that rely on natural convection cooling with either air-or water-based systems. With the successful conclusion of the airbased testing program in FY16, the transition to a water-based RCCS concept is underway. The overall assembly of the water-based NSTF will reflect a ½ axial scale and 12.5° sector slice of the primary design features of a full scale AREVA concept.This report documents the FY17 progress and achievements made in the computational analyses of the water-based NSTF. Both system-level and high fidelity Computational Fluid Dynamics (CFD) analyses were performed to gain a complete understanding of the complex flow and heat transfer phenomena in natural convection systems. The progress on the waterbased NSTF design, instrumentation, and test planning are summarized in a companion report (ANL-ART-98).The primary objective of the NSTF analyses is to assess the limitations in typical approaches for modeling this type of natural circulation RCCS concepts, and validate the analysis methods and computer codes which may be used in licensing. Additionally, the NSTF analyses aid in the RCCS design optimization, and supporting experiment activities, i.e. helping assure that the experimental procedures, setup, and measurements follow best practices and produce high quality, traceable data.

60439. For information about Argonne and its pioneering science and technology programs, see www.anl.gov. DOCUMENT AVAILABILITYOnline Access: U.S. Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free at OSTI.GOV (http://www.osti.gov/), a service of the US Dept. of Energy's Office of Scientific and Technical Information.