In the process of operation of RBMK reactors damage took place on welded pipings produced from austenitic stainless steel of the type 08X18H10T. The inspection of damaged sections in pipings has shown that in most cases crack-like defects were of corrosion and mechanical character. This paper considers in detail the reasons for the damage appearance and their development for this type of welded joints of downcomers (empty set 325 x 16 mm, which were fabricated from austenitic stainless steel using TIG and MAW welding methods. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.