RETRAN's improved small break modeling capability

The RETRAN-02 computer code has been used extensively to analyze both operational transients and small break loss-of-coolant accidents (SBLOCA). While the results of these analyses are generally in good agreement with data, the explicit solution method sometimes requires small time-steps for portions of the small break calculations. The RETRAN-03 code, now under development, is incorporating additional models to extend the capability of RETRAN-02 and improve the code efficiency for SBLOCA's. Included in these models is a stable, implicit solution method which has provided a significant reduction in CPU requirements while maintaining satisfactory analyses results. The new models for RETRAN-03 and results of small break analyses using RETRAN-03 are briefly discussed in this paper. (orig.)