[en] The Limiting Factors Analysis of a high availability nuclear plant are reported herein following a detailed study of two and one-half years of mature plant operation of the Maine Yankee Atomic Power Plant. The study plant is an 800 MWe PWR, with an NSSS design by Combustion Engineering (C-E) and a Balance of Plant design by Stone and Webster (S and W). C-E was prime contractor to EPRI for this study and S and W a subcontractor. Field engineers from C-E and S and W were stationed at the plant site for eighteen months of detailed data gathering. The data were computerized and sorted to obtain the quantitative results of the study in terms of systems and components which caused lost generation