Research On The Principles And The Computer Aided Technology Of The GO-FLOW

The modern engineering system behaves dynamically in its life cycle and this characteristic of dynamism should be considered in the risk assessment of the system. The conventional probabilistic risk assessment methods adopt the static analytic view. They cannot solve the problem of dynamism in the security of the actual engineering system. In view of this, the conventional probabilistic risk assessment methods must be improved, especially in the treatment of time dependence. GO-FLOW methodology can treat time dependence. It can describe the functions of a system with a complex operating sequence and multiple states. The system probabilistic risk at the time points can be easily obtained after simple calculation. GO-FLOW has provided an effective way for analyzing and evaluating the security of dynamic engineering system. However, it has to be improved as there are still some weaknesses in its graphical modeling capability, calculation and application in complex engineering systems. GO-FLOW methodology has been developed ever since the 1990's, but it has been rarely studied in China. Based on the project "security analysis technique of dynamic systems", this thesis firstly carries out a detailed and systematic study of the basic principles of GO-FLOW. It particularly makes the following extensions to GO-FLOW:(1) Some new logical modeling operators such as "K/N" gate, "Not" gate, "Phased mission" gate are introduced and corresponding calculating principles are also given.(2) A precise algorithm is provided to calculate the reliability of complex systems with shared-signals.(3) A framework is provided to treat with the common-cause failure problem.(4) The principles and methods of treating a phased mission problem with the help of GO-FLOW are brought up in this paper.(5) GO-FLOW is combined with HAZOP to obtain an all-round analyzing result.Secondly, the paper provides a software frame of computer aided GO-FLOW study. In addition to the composition and function of the software, the working process, data organization and the main techniques and methods of its realization were introduced in detail.Finally, the operation of PWR-AFW system is analyzed on the basis of the improved GO-FLOW and computer-aided GO-FLOW software. This sample shows the advantages of GO-FLOW methodology in solving the security problem of dynamic systems.