Prediction of GE-Atlas Transient Boiling Transition Data Using RETRAN-02/RETRAN-15F

The steady-state operating limit for boiling water reactors (BWRs) is determined by calculating the transient change in the critical power ratio (CPR). To determine the operating limit CPR, a method for calculating the ΔCPR during transients is needed. The RETRAN code can be used as a tool in the evaluation of transient CPRs for determining the operating margin for BWRs. Since the RETRAN code does not contain a critical power calculation, the ΔCPR cannot be obtained directly from RETRAN. Therefore, a program, TCPYA01, designed to evaluate transient CPR (and ΔCPR) based on the GEXL correlation using time-dependent conditions from RETRAN was used. The justification for using the RETRAN code is provided by predicting transient boiling transition data taken at the GE-ATLAS loop facility. Results of the sensitivity studies performed on nodalization, void models, and time-step size are also provided.