Method of estimation of structural reliability of heat exchangers of steam generators

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 Until now all predictions of SG HET pluggings in Ukraine were performed only with the simple linear extrapolation. The literature analysis, including the proceedings of OKB “GIDROPRESS” International Seminars on Horizontal Steam Generators, shows that the development method, which would be physically and statistically based, is a actual and very important task.

  The developed method based on stochastic laws of crack dimensions distribution with taking into account its growth, limit load model of cracked tube and steam generator plugging statistics. Based on the history of the tubes plugging of specific SG three statistical parameters have to be found: initial number of defects, stochastic parameter of defect depth and the defect growth rate.

 

The developed method was used for the prediction of HET failure for Ukrainian SG as well as for justification of pressure reduction of periodic hydrostatic test for primary circuit of WWER-1000 and WWER-440 NPPs.

  Within the project, based on the Ukrainian history of WWER-1000 SG operation, the database of HET plugging is created.

  Developed method is expected to be the complementary tool for the optimization of HET ISI program and for the modernization of HET plugging criteria.

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HET pluging statistiсs of SG #4 of Unit 1 of South Ukraine NPP