Physical characteristics of the steam discharge system of PWR, which consists of valves, piping, steam sparger, and steam accomodating tank, have been analyzed and a preliminary analysis system has been set up for development of the analysis and design methodology for the system. The work was the results of the second year research in the planned research period of four years. Analysis has been made for the characteristics of rapid transient and steady flow in the piping, steam condensation, small and hermetically sealed tank performance, bubble behavior and wall pressure oscillation in a large and open tank, coupling between wall pressure oscillation and structure vibration. Based on the analysis results, conceptual methods for controlling the hydraulic load on the wall have been devised and evaluated. (Author).