RETRAN Analysis of the San Onofre Unit 2 Turbine Trip from 100% Power

The RETRAN analysis of San Onofre Nuclear Generating Station Unit 2 (SONGS 2) turbine trip from 100% power is a continuing effort of our in-house RETRAN model development to benchmark the calculations against the plant test data. The previous benchmarked calculations—RETRAN analyses of SONGS 2 flow measurements and low-power natural circulation test—showed very good agreement with the plant test data. The latter RETRAN model was then expanded for the current study to include steam generator secondary side, main steam line pipings, control valves, and plant control systems. The benchmarked turbine trip model has been used to analyze the station-requested plant operational transients. These are (a) assessment of strategies for performing turbine overspeed surveillance, (b) determining a manual position of one steam bypass valve following a reactor trip from 100% power, and (c) plant response to one main steam isolation valve closure at 90 and 50% power levels. In addition, the RETRAN calculations employing benchmarked models can be used to verify the simulator predictions and assess the existing plant operating procedures.