An experimental investigation of boiling water reactor parallel channel effects during a postulated Loss of Coolant Accident

This thesis describes an experimental study of parallel channel effects (PCE) on the distribution of emergency core spray cooling water in a Boiling Water Nuclear Reactor (BWR) following a postulated design basis Loss Of Coolant Accident (LOCA). The experiments were conducted in a scaled test section in which the reactor coolant was simulated by Freon-114 at conditions similar to those postulated to occur in the reactor vessel shortly after a LOCA. A BWR/4 was simulated by a test section which contained three parallel heated channels to simulate fuel assemblies, a core bypass channel, and a jet pump channel. The test section also included scaled regions to simulate the lower and upper plena, downcomer, and steam separation regions. A scaling analysis was performed to insure simulation of countercurrent flow limiting (CCFL) phenomena and real-time system response. Most of the test section was fabricated from glass pipe to permit flow visualization. Nine transient experiments were conducted at simulated BWR conditions. The lower plenum vaporization rate and heater rod power were parametrically varied, while the core spray flow rate was held constant. During these experiments the flow distributions and heat transfer phenomena were observed and measured