RETRAN Simulation of Three Mile Island Unit 2 Startup Overfeed Incident

The RETRAN system analysis code has been used to simulate a Three Mile Island Unit 2 overfeeding transient that occurred during a plant startup. Excessive feedwater was fed into the steam generators and resulted in a sudden depressurization of the reactor coolant system (RCS). The reactor tripped on low RCS pressure and safety injection was initiated. The RETRAN simulation of this event shows the same trends and predicts the same sequence of events as the plant data and thus develops a reliable understanding of the relationship between the primary RCS and the secondary feed and steam systems. The model developed is useful in studying the margin to protective system limits during disturbances at low power.