Location Dependent Loss of Coolant Accident Frequencies for Risk-Informed Resolution of Generic Safety Issue 191

This paper summarizes the analysis of loss of coolant accident (LOCA) frequencies in support of a risk-informed (RI) evaluation of Generic Safety Issue (GSI) 191 for the South Texas Project Electric Generating Station (STPEGS) Units 1 and 2. The STP RI-GSI 191 Closure Study investigates the size and location of loss of coolant accidents (LOCAs) more finely than in traditional PRAs in order to assess the risk of debris formation during the LOCAs that could interfere with the operation of the emergency core cooling systems (ECCSs) or inhibit coolant flow through the core during the recirculation phase after a LOCA. The size and location of the break could influence the amount and chemistry of debris formation and the timing and need for actions to initiate or terminate containment sprays and recirculation cooling. This application requires the capability to estimate LOCA frequencies as a function of break size at each location within the Class 1 pressure boundary with due regard to the proper characterization and quantification of uncertainties.