Application of the Uncertainty Analysis Method to Evaluating the Mechanical Strength of Steam Generator Metal at PWR-based NPPs During Hydraulic Tests and Seismic Loads

Abstract

The problem of using the uncertainty and sensitivity analysis methodology in performing strength analyses is addressed. This matter is relevant for ensuring reliable operation of PWR-based nuclear power facilities. In view of measurement errors and use of empirical models, the computer codes feature some uncertainty. Two loading modes were analyzed: the hydraulic test pressure and seismic impact on a pipeline. The calculations were carried out strictly in compliance with the requirements of the regulatory documentation [enterprise standards (STO) and codes and regulations (NP)] adopted at the Rosatom State Atomic Energy Corporation. For each of the modes, the obtained stress state and deformations were studied. Based on the calculation results, a distribution close in appearance to a normal one has been obtained, but there are also extreme values that go beyond the normal distribution, which may have the nature of outliers with a low realization probability. A sensitivity analysis for these loading modes is considered. It has been shown that the Poisson's ratio and Young's modulus have the strongest effect. The results obtained may be relevant for cyclic and long-term cyclic strength analyses of pipelines that have long been in operation, for vibration strength analysis, as well as in modeling the pipeline destruction in the analysis of severe accidents.