The work described in this paper reports on the additional research and development conducted in support of the Risk-informed Over Deterministic (RoverD) approach to address the concerns raised in Generic Safety Issue 191 (GSI-191). In this work, a method is developed using a RELAP5-3D PWR model coupled with a MELCOR large, dry containment model to obtain conservative containment pressure estimates used together with conservative sump pool temperature estimates in order to comply with the regulatory guidance. The current regulatory guidance on Emergency Core Cooling System (ECCS) performance, "Revised Content Guide for Generic Letter 2004 02 Supplemental Responses, November 2007" (ADAMS Accession No. ML073110278), and Regulatory Guide 1.82, "Water Sources for Long Term Recirculation Cooling Following a Loss of Coolant Accident," is briefly reviewed as it applies to flashing in the ECCS pumping system. Because the guidance does not specify the method that should be used to comply with the conservative assumptions, an acceptable approach must be developed by the utility engineer.