Time Dependence of Test Fuel Power Coupling During Transient Reactor Test Facility Irradiation Experiments

Studies have been conducted at the Transient Reactor Test Facility (TREAT) to determine the variation during transient irradiation experiments of the ratio of axial midplane test fuel power to reactor power as measured by ex-core ion chamber current. It is shown that the dependence of this ratio on core temperature is generally small. However, effects due to control rod motion can be substantial. A simple mathematical expression that predicts the dependence of this ratio on control rod position is shown to give good agreement with integral experimental data. This work makes possible refinements in obtaining the desired power-versus-time behavior in test fuel by accounting for the effects of instantaneous position of control rods and core temperature during transient operation.