Cooldown performance capability of atmospheric steam dump system

The steam generator atmospheric steam dump (ASD) system is evaluated to assess its thermal-hydraulic ability to cool down the reactor coolant system and steam generators following a design basis event (DBE) in which the main steam isolation valves close. A number of pressurized-water reactors are examined to evaluate ASD system performance within the constraints of the available licensing feedwater supply. Calculations using Final Safety Analysis Report data show that, although the ASD system is vital for safety following a DBE, design inadequacies exist which indicate unresolved safety and licensing issues at a number of operating plants