A state-of-the-art report on the experimental and theoretical studies on LB-LOCA reflood

To establish the experiment requirements and techniques for reflood experiment, this report investigates the existing PIRTs related to the thermal hydraulic phenomena of reflood, and summarizes the existing reflood experimental facility and the experimental results. Also, this report analyzes the thermal hydraulic system codes that are widely used to analyze reflood process, and identifies the shortcomings of the reflood models implemented in the system codes. Existing reflood experiments are performed focusing on the generation of the data for the overall verification of the thermal hydraulic system codes. The shortages of the existing studies for the reflood are 1) the insufficiency of the detailed data to develop individual models, 2) the scarcity of the quantitative experimental data for the effect of the spacer grids with mixing vane, and 3) the deficiency of the understanding and experimental data for the dispersed film boiling phenomena. Four kinds of PIRT results are summarized for the LB-LOCA reflood in which the important phenomena and individual process are identified. The reflood models implemented in the thermal hydraulic system codes are reviewed, and the prediction capability and the uncertainty are assessed for each heat transfer region. A few of the existing reflood experiments adopted some advanced instruments. However, there are a lot of difficulties for the analysis of the local phenomena because the reliability and accuracy of the instruments are not so good. Thus, to analyze the reflood phenomena in detail, it is necessary to develop the advanced instrumentation systems with improved reliability and accuracy. This report will be useful for the design of the reflood experimental facility, the identification of the important thermal hydraulic phenomena, the development and the use of the advanced instrument for the generation of the detailed experimental data, and the setup of the test matrix