Analysis of Core Characterization Transients for TREAT Restart

A core characterization process was completed as part of the Transient Reactor Test Facility (TREAT) restart project. The core characterization process is normally performed following a reconfiguration of the TREAT core. This characterization process includes performance of three temperature-limited transients. Prior to performing the transients, analysis is performed using KENO-VI to determine the high-temperature locations and the initiating reactivities for each transient. The point-kinetics code Simulating TREAT Reactor Kinetics (STREK) is used to estimate the peak power, peak temperature, and total energy deposition in the core. STREK also provides plots of pertinent parameters as functions of time to observe time-dependent behavior of the transient. After the transients are complete, the resulting data from these transients are used to develop operating limits for continued operation with the core configuration being characterized. The three transients for the characterization are performed in a progression of increasing initiating reactivity. The first transient has an initiating reactivity of 1.8%Δk/k. The second transient has an initiating reactivity of 3.0%Δk/k. The third transient has an initiating reactivity of 3.85%Δk/k. After the first two transients are performed, a two-point extrapolation of the data is used to determine a temporary estimate of the core operating limits. Once the third transient is complete, the resulting data are fit to an equation, and a three-point extrapolation of the operating limits for the core configuration is generated. This completes the characterization process and provides conservative limits for transient operation of TREAT.