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Novel Similarity Level Characterization Methodology Informed by CFD for RCIC System Scaling
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The Reactor Core Isolation Cooling (RCIC) System is a safety system that provides water to the reactor pressure vessel during off-normal Boiling Water Reactor (BWR) conditions, such as reactor isolation from the turbines or loss of AC power. Under loss of AC power conditions, the RCIC System is expected to fail due to battery depletion within 4 to 8 hours of operation for many units. However, the system did not fail until about 70 hours into the accident at Fukushima Dai-ichi Unit 2, which was well past the time of battery depletion. To investigate the full potential of the RCIC System, the Laboratory for Nuclear Heat Transfer Systems (NHTS) at Texas A&M University is modifying an existing experimental test facility to enable performance evaluation of BWR RCIC System components under nominal and beyond design basis event conditions. A careful scaling analysis is essential to ensure proper representation of the RCIC System’s key components and phenomena in the experimental testing. This dissertation describes and applies a method to estimate the scaling Similarity Level of the RCIC system turbomachinery and Suppression Pool. The methodology is demonstrated with the Texas A&M University facility but can be applied to other RCIC system facilities. With respect to any full-scale RCIC system, upon availability of data from a full-scale system of interest, the scaling Similarity Level values can be determined for the NHTS facility system. Those values will determine whether the NHTS facility is appropriate for studying that particular full-scale system’s behavior. Additionally, the scaling Similarity Level values can decide what modifications would need to be done to the NHTS facility to make it appropriate for a particular system, as well estimating the testing operating conditions. Scaling will justify the use of the NHTS facility as is or with modifications to understand the full-scale system behavior and investigate ways to expand operation for longer time, which is of great interest to the U.S nuclear industry. This study is the first of its kind to employ Computational Fluid Dynamics (CFD) to obtain necessary input for the scaling analysis and Similarity Level estimation. Output from CFD analysis with the STAR-CCM+ code were used to obtain characteristic time ratio input parameters for Similarity Level estimation of the RCIC System’s Terry Turbine. Original contributions of this study are the derivation of Similarity Level equations for the RCIC System turbomachinery and BWR Suppression Pool, the development of CFD models for the Terry Turbine, the validation of one of the CFD models against experimental data and application of the CFD simulation results to provide input for Similarity Level estimations. Using the information provided by the CFD analyses, the Similarity Level between the GS-1 and ZS-1 Terry Turbines were computed, and showed that a high level of similarity exists between the actual turbines. Furthermore, the characteristic time ratios of the Suppression Pool were calculated for the NHTS facility to provide reference data for Similarity Level calculations.
Hawila, Mohammad Abdel Majid Mustafa (2018). Novel Similarity Level Characterization Methodology Informed by CFD for RCIC System Scaling. Doctoral dissertation, Texas A & M University. Available electronically from