Following the loss of vital AC power and the Residual Heat Removal Systems (RHRS) during shutdown of Vogtle Unit 1 on March 20, 1990, much attention has been focused on the need to evaluate system performance following a loss of the RHRS. Because there is a lack of understanding of the thermal-hydraulic behavior and nuclear steam supply system performance following a loss of the RHRS, system performance analyses were performed to identify the key phenomenological behaviors characterizing such an event. To evaluate system performance following such an event a simplified transient system performance code was developed to predict reactor coolant and secondary system performance following a loss of RHRS event. In the evaluation of system performance following a loss of the RHRS, the use of the steam generators as an alternate means of decay heat removal was assessed. Because the RCS is maintained at reduced inventories with air in the primary, pressurization of the RCS will occur with pressure eventually stabilizing as steam produced due to boiling in the core is condensed in the steam generator. This alternate means of decay heat removal is potentially attractive since the successful use of the steam generators to remove heat, should the RHRS fail and boiling occur, would not require the addition of coolant to the RCS. This document provides the objectives, results, and conclusions of this evaluation.
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