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# Statistical analysis of the nuclear power plant equipment failure data in nonhomogeneous failure flow

### UDC: 519.7:519.23/.24/.25

In the paper systems with the operable state and the down state are considered. Functioning process of technical equipment can be divided into three operating periods. There are a burn-in period, a normal life or useful life period and an ageing period. Reliability coefficients of equipment and methods for their calculating depend on the operating period. The failure flow parameter is relatively constant on the useful life period. But we should take into consideration the burn-in period with a decreasing failure flow parameter and the ageing period that exhibits an increasing failure flow parameter. In general more complex time dependences can take place. Also we can assume that the repair flow consists of the «non-homogeneous» (concerning a distribution) repair time. For instance a mean time to repair can gradually rise since an equipment ages and a fault location time and a repair complication rise. The aim of this paper is to develop the new mathematical model that can take into account possible «distortions» of an event flows and allow to calculate reliability coefficients of the systems, which probabilistic characteristics can vary in time. The new mathematical model can take into account possible «distortions» of an event flows by means of a normalizing flow function Ψ. The normalizing flow function model is presented.

Examples of data analysis at each stage of the study on the basis of statistical information about failures element KNK-56 control and protection system (CPS) unit EGP-6 Bilibino derived from operating experience were performed. On presented algorithm were calculated reliability coefficients for a large group of elements of the reactor control rods EGP-6 on the basis of information over a long period of operation (from 1974 to 2014).

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