Analysis of the Computing Methods of Structural Reliability of Process Flow Diagrams for the Power Generating Units of Nuclear Power Plants

Анотація

This paper gives consideration to the methods used for the computation of the reliability of complicated engineering systems that allow us to specify the probability of failure-free operation of the equipment used by the power generating units of NPP, in particular the enumerating technique of states, the methods of minimal ways and minimal cross-sections, the reliability computing method based on the expansion of a relatively ²special² elements, and the ²fault tree² construction method. The reliability computing method based on the enumerating technique of states is grounded on the logic algebra tool and uses the computing methods of the reliability indices of series, parallel and combined connections in bridge circuits. When implementing the reliability computing method based on minimum ways and cross-sections minimum ways should be determined first. Then minimum cross-sections are determined, i.e. such options of element ways that in case of the failure of one element cause failure of the entire diagram in spite of the functionality of other ways. The reliability computing method based on the expansion of a relatively ²special² element provides for the isolation of one (²special²) element in the calculable system that is unconditionally faultless (the probability of the operable condition is equal to the unit) or unconditionally fault (the probability of the operable condition is equal to the zero). The analysis of the ²fault tree² consists in the determination of such a combination of elements whose simultaneous failure results in the knot of tree, i.e. in the failure of the entire calculable system. In particular cases the set of elements is possible whose failure results in the failure of entire system. The knots of tree are the logic operations of an ²AND² or ²OR² type (that define the product or the sum of events).