Structural integrity assessment and lifetime prediction for the control rods couplings of the WWER-440 reactor. Part 2. Assessment of the coupling structural integrity and justification of its material degradation monitoring interval

Abstract

The structural integrity of the control rods couplings of the WWER-440 reactor is analyzed. On the basis of material investigation of the control rod couplings (martensitic-ferritic stainless steel grade 14Kh17N2, analogue of AISI 431 steel) that were under operation in the Unit 3 of Novovoronezh NPP it is shown that the structural integrity of the coupling is satisfied until the radiation-induced hardening of its material does not exceed 423 units of Vickers hardness.