To assess severe accident risks and to develop a methodology of safety assessment for advanced LWR, a containment response analysis method was applied to a passive LWR (AP600). The methodologies performed for U.S. NRC``s "Severe Accident Risks," NUREG-1150 were used in the present study, but the detailed process is somewhat different from those of current PWRs. Major steps of the quantification of severe accident risks from a nuclear power plant and the methodologies of containment response analysis for severe accidents performed for NUREG-1150 are first outlined. Then, the application procedures of these methods to a passive LWR are described in detail : plant specific features important to containment response analysis and accident progression event tree (APET) quantification procedures for AP600 are summarized. In addition, the uncertainty issues were investigated on the basis of those issues identified in conventional PWRs. Finally, a brief summary of the containment response analysis results of point-estimate and statistical-estimate is presented to provide a perspective on the passive LWR containment response for postulated severe accident. Some problems of the containment response analysis method are summarized, and also tasks that are incomplete in the present study are presented for the further study.