Detectability of BWR Core Shroud Separation Through Anomalous Core Characteristics

If a boiling water reactor core shroud is postulated to completely crack at any of the horizontal welds, an upward load might cause the upper portion of the shroud to lift. Anomalous core characteristics resulting from the flow through the gap could be detected, and the operators would immediately shut down the plant. These anomalies [anomalous core power, total primary loop recirculation (PLR) system flow, core-support-plate P, PLR pump inlet temperature, etc.] are quantified using RETRAN-02/MOD4.

A noding method has been introduced to precisely simulate gap leakage flow and its enthalpy. The detectability of shroud separation was confirmed through anomalous core characteristics.