personnel: high stress; reduced time for performance of the action; impossibility of the action in-situ due to conditions that prevent from performance of the action; decreased information support in the MCR. X. Analysis of systems and modeling of accident sequences It is recommended to elaborate the accident sequences model of the seismic PSA on the basis of the available accident sequences models of PSA for internal IEs. It is recommended to use event trees and fault trees from models of PSA for internal IEs as the basis for the PSA model being developed including any necessary additional events and/or changes in system models related to dependent failures in systems due to seismic effects. It is recommended to take into account the fact that types and consequences of failures at various seismic force levels can vary, and differ from those considered in PSA for internal IEs for one and the same element. It is recommended to include elements from the final seismic list into the probabilistic model. It is recommended to consider various levels of seismic effect according to the seismic hazard curve that can influence the aggregated probability of severe accidents with fuel melting. Consideration of various levels of seismic effect is recommended by imposing specific boundary conditions. Using AS models elaborated within NPP PSA of level 1 for internal IEs can be possible when developing scenarios of seismic effects to account for specific seismic effect consequences (multiple failures and spurious actuations). In these cases it is recommended to develop new AS models upon condition that the principles of modeling
personnel: high stress; reduced time for performance of the action; impossibility of the action in-situ due to conditions that prevent from performance of the action; decreased information support in the MCR. X. Analysis of systems and modeling of accident sequences It is recommended to elaborate the accident sequences model of the seismic PSA on the basis of the available accident sequences models of PSA for internal IEs. It is recommended to use event trees and fault trees from models of PSA for internal IEs as the basis for the PSA model being developed including any necessary additional events and/or changes in system models related to dependent failures in systems due to seismic effects. It is recommended to take into account the fact that types and consequences of failures at various seismic force levels can vary, and differ from those considered in PSA for internal IEs for one and the same element. It is recommended to include elements from the final seismic list into the probabilistic model. It is recommended to consider various levels of seismic effect according to the seismic hazard curve that can influence the aggregated probability of severe accidents with fuel melting. Consideration of various levels of seismic effect is recommended by imposing specific boundary conditions. Using AS models elaborated within NPP PSA of level 1 for internal IEs can be possible when developing scenarios of seismic effects to account for specific seismic effect consequences (multiple failures and spurious actuations). In these cases it is recommended to develop new AS models upon condition that the principles of modeling
RB-123-17%20ENG.docx