Thermalydraulic Processes in the Reactor Coolant System of a BWR under Severe Accident Conditions

Abstract

This chapter provides a brief discussion of the boiling water reactor (BWR) control blade, channel box, core plate, control rod guide tube, and reactor vessel safety relief valve configuration and the effects of these structural components upon thermal hydraulic processes within the reactor vessel under severe accident conditions. The BWR reactor vessel is protected from overpressure by multiple safety relief valves mounted on the horizontal piping runs of the main steam lines between the vessel and the inboard main steam isolation valves. Multiple control blades are employed in the BWR design. Of the dominant BWR accident sequences leading to core melt, Short-Term Station Blackout involves the shortest period of time between reactor shutdown and the onset of core degradation and fission product release from fuel. The chapter discusses only the major unique characteristics of BWR severe accident response that would affect considerations of in-vessel fission product transport.