Debris filters with flow bypass for boiling water reactors

Abstract

In a boiling water nuclear reactor fuel bundle, a debris catching arrangement is disclosed for incorporation within the flow plenum up stream or below the rod supporting grid of the lower tie plate assembly. The device is preferably placed within the lower tie plate flow plenum between the fuel bundle inlet and the rod supporting grid structure supporting the fuel rods; alternate placement can include any inlet channel upstream of the fuel rods including the fuel support casting. The disclosed debris catching designs include strainer structures defining spatially separated straining or obstructing layers imparting to the fluid in the plenum a circuitous flow path. This circuitous flow path causes the two phase separation of the heavier debris from the lighter transporting water by flow direction change with the debris directed and detoured to a trapping structure. Further, a strainer structure is provided in the plenum that does not constitute a continuum of fine structure across the strained plenum which might become clogged to the extend that overall flow is restricted. The strainer structure is positioned so that eventual trapping of the debris occurs upon cessation of flow so that with removal of the plenum from the reactor, such as removal of the fuel bundle, the debris is likewise removed. Embodiments are disclosed which include swirling deflection, cone deflection, and strainer structure deflection of debris.