Flow-accelerated corrosion rate and residual life time estimation for the components of pipeline systems at nuclear power plants based on control data
There is large number of nondestructive operation control data at each NPP units. To prove reliable operation and optimal both volume and period of control it is necessary to develop computer codes, regulatory and modified procedures to estimate FAC rate and residual life time [1, 2, 3]. The paper deals with different approaches to FAC rate estimation based on control data. Some kinds of piping elements from different types of NPP units are researching in this paper. FAC process peculiarities at piping straight parts and welding of NPP units with PWR and BWR are discussed in previous paper . Corrosion products deposit on interior surface of piping leads to residual life time formally to arise. However, real state of piping wall thickness is unknown as well as initial one. Researching performed directs to improve FAC rate estimation procedure on the base of control data to adapt calculation results to real situation according «rational conservatism».
The main idea of paper is to estimate FAC rate in piping elements by the same manner. Besides, there are suggested some procedures to estimate correcting coefficients taking into account technological tolerance on manufacturing, element geometry, corrosion products deposits influence on both initial and minimal wall thickness, based on control data and standards.
Researching performed show the efficiency of procedures developed for welding. For homogeneous sample of bends there was performed analysis of both known and developed procedures. As result the ranking was fulfilled according to criterion «conservatism of residual service life estimation».
Application of correcting coefficients leads to more high conservatism in service life estimation in with using of nominal wall thickness, and result demands on element geometry and size and also on type of NPP unit.
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