Comparison of transient responses for SCWRs with different flow path designs under loss of flow accident

Many various supercritical water-cooled reactor (SCWR) conceptual designs have been proposed by different researchers in last few years. However, the research on comparison of these concepts to judge the advantage and shortcoming of each conceptual design has little been carried out. This study is devoted to comparing transient flow characteristics and the consequent safety performance of SCWRs with different flow path design. Three different SCWR concepts such as SCWR with mixed spectrum core (SCWR-M), American SCWR design and Simplified Supercritical Water-Cooled Reactor (SSCWR) are respectively selected as the representations of multi-pass core, one-pass core with water rods and one-pass core without water rods. The comparative analysis of loss of flow accident is performed for the three SCWR concepts by new developed code TACOS. The flow rate and cladding temperature behaviors following the same transient assumptions are compared to each other. The results show that the SCWR-M and the American SCWR concepts have more complicated flow characteristics than the SSCWR. Inverse flow occurs both in the SCWR-M and the American SCWR when pump coastdown ends. The effect evaluation of Auxiliary Feedwater System (AFS) flow rate indicates that the flow path design of the SCWR-M would require larger injection flow rate than the other two concepts. The comparison indicates that the flow path design of SSCWR could adapt better for the transient conditions than the other two concepts.