The Pacific Northwest Laboratory, under contract to the U.S. Nuclear Regulatory Commission, has conducted an assessment of the values (benefits) and impacts (costs) associated with potential resolutions to Generic Issue 143—“Availability of Heating, Ventilation, and Air Conditioning (HVAC) and Chilled Water Systems.” The key objectives of the study were to (a) identify vulnerabilities related to failures of HVAC, chilled water, and room-cooling systems, (b) develop estimates of room heatup rates and safety-related equipment vulnerabilities following losses of HVAC/room-cooler systems, (c) develop estimates of the core damage frequencies and public risks associated with failures of these systems, (d) develop proposed resolution strategies to this generic issue, and (e) perform a value/impact analysis of the proposed resolutions. Detailed probabilistic risk assessments for four representative plants form the basis for the core damage frequency and public risk calculations. Internally initiated core damage sequences as well as external events were considered. Three proposed resolution strategies were developed for this safety issue, and it was determined that all three were not cost effective. Additional evaluations were performed to develop “generic” insights on potential design-related vulnerabilities and potential high-frequency (> 10−4/reactor-yr) accident sequences that involve failures of HVAC/room-cooling functions. It was concluded that, although high-frequency accident sequences may exist at some plants, these sequences are plant-specific in nature or have been resolved through hardware and/or operational changes. The plant-specific individual plant examinations appear to be an effective vehicle for identification and resolution of these plant-specific anomalies and hardware configurations.