Stressed-deformed state and vibration resistance of the RBMK-1000 reactor collectors and pipes at the Leningrad, Kursk and Chernobyl'sk NPPs

Calculational results for the strength of the multiple forced circulation circuits (MFC) at the Leningrad, Kursk and Chernobyl'sk NPPs are given. The stngth calculation for collectors and pipes is performed for the following loads: internal pressure; external mechanical loads and their own mass; stresses resulted from self-compensation of thermal expansions, - support motions, tension in supports, due to fringe effect in pipe joints with different wall thickness, during heating due to difference in linear expansion coefficients for the metal and coatings. The collectors and pipes of pipelines are made of two-layer material (22 K low-carbon steel with 0.8Kh18N10T stainless steel coating). Analysis of the results obtained shows that maximum value of total stresses from all loading factors constitutes for the Kursk and Chernobyl'sk NPPs approximately 95% and for the Leningrad NPP it is about 80% of permissible stresses. Low frequencies of proper oscillations of MFC circuit pipelines at the Leningrad-2 NPP are in the range of 2.6-5 Hz and the difference in low oscillation frequencies with spring supports and without them doesn't exceed 0.3 Hz. It is concluded that the joint unit of a pipeline suction part with a pump and a section of pipeline bend joint with a horizontal pipeline section are the most loaded points of the RBMK-1000 MFC circuit