Transient Following Partial Loss of Feed Water for Thorium-based Natural Circulation Reactor

A new reactor system under design study is a vertical pressure tube-type boiling light water cooled and heavy water moderated. Main heat transport system consists of reactor core, core inlet and outlet extensions, inlet feeders, tailpipes, steam drums, downcomer, and inlet header. It incorporates several advanced passive safety features, e.g., heat removal through natural circulation both during normal operation and reactor shutdown without the use of any coolant pump. Safety remains the paramount consideration in the design, while plant availability is the next. Several reactor trip set points are provided in design to tackle the disturbances in operation, and many safety systems are provided to mitigate different accidental conditions. A major objective of the reactor design is to provide a capability to withstand a wide range of postulated events (PIEs) without exceeding the acceptance limits, thereby maintaining fuel integrity. Partial loss of feed water is one of such PIEs. Following article highlights the modeling and overall transient behavior and its safety implication.