Probabilistic Estimation of the Residual Lifetime of the VVER Coolant Loop Elements in Aging Control
The main processes that limit the lifetime of the elements of the reactor coolant circuit (RCC) are high- and low-cycle fatigue, various types of embrittlement of materials as well as fatigue crack growth. These processes can be intensified by the influence of corrosion. Important for making decisions on the operation of the RCC is the residual resource, i.e., the time to the limit state, on the basis of which the lifetime (aging) is controlled. The residual life is estimated using mathematical models (both analytical and simulation ones) of aging processes in the form that is possible on the basis of the existing operating experience and control data. Methods for obtaining estimates of residual lifetime for various descriptions of aging processes are related to the problem of level crossing either by an observed process, or by a damage accumulation process, or by a fatigue crack growth process. In this case, the traditional deterministic conservative calculation can be supplemented by obtaining a probabilistic estimate of the lifetime, if relevant information is available, in the form of operational control data, as well as taking into account the uncertainties associated with the characteristics of the metal, the quality of the control means, the method of mathematical description of the operating modes of the elements, etc. The article deals with the issues of obtaining probabilistic lifetime estimates as indicators of reliability for some models of aging processes as part of lifetime management. The idea refers to ways of building a time series using control points and obtaining lifetime estimates with appropriate confidence intervals.
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Link for citing the article: Gulina O.M., Merkun A.V., Yurin V.E. Probabilistic Estimation of the Residual Lifetime of the VVER Coolant Loop Elements in Aging Control. Izvestiya vuzov. Yadernaya Energetika. 2022, no. 3, pp. 95-105; DOI: https://doi.org/10.26583/npe.2022.3.09 (in Russian).