Principles of representative thermohydraulical scenarios choosing used for strength simulation of npp units

Abstract

Safe operation of main equipment of nuclear power plants requires periodic estimation of such factors as size of accumulated fatigue damages of elements constructions and predicted value of fatigue damage on rated period of future operation. One of the most important stages of nuclear power plant resource prolongation is analysis of thermomechanical influence of the operational regimes on the strength of the elements and its units. Herewith for one of the element operational regimes a couple of several variations are performed, each of which is characterized by its unique set of thermomechanical parameters, such as pressure, temperature, velocity of coolant consumption, etc. A huge amount of such variations can increase of calculation time and software requirements. The main goal of this research is decreasing of amount of thermohydraulic scenarios justification of possible operational regimes of main equipment of nuclear power plants that are subjected by full analysis during possible amount of fatigue damages determination. This research describes a possibility of decreasing amount of required simulations using reasonable exclusion of unrepresentative variants on the basis of mathematic based comparison. This paper described main principles of thermohydraulical scenarios while using this methodic for strength simulation of pressure compensator of nuclear power plants with WWER-1000. The numerical parameters for estimation on typical scenarios diagrams are performed, and it gives a possibility to determine reasonable scenarios from groups that are close by their character of simulated processes. The accuracy of obtained data during reasonable thermohydraulical scenarios is at satisfactory level according to its total analysis, and it gives possibility to recommend the pro-posed approach for usage.