Peculiarities of corrosion damage of weld joints in steam generators of WWER-1000 nuclear power plant
The causes of the cracking of welded joints of collectors with steam generators in WWER-1000 nuclear power plant are studied. It is found that the cracks are filled with iron hydroxide Fe(OH)2, and the surrounding metal has a high hydrogen content. Results of Charpy impact tests of specimens cutout from perlite Mn – Ni – Mo steel template and fractographic investigations confirm a quasi-brittle mechanism of metal fracture due to cracks propagation. Mechanism of cyclic corrosion cracking of welded joint material under the wedging action of local stresses induced by formation of corrosion products has been proposed.