2021 №03 (01) DOI of Article
2021 №03 (03)

Automatic Welding 2021 #03
Avtomaticheskaya Svarka (Automatic Welding), #3, 2021, pp. 10-16

Mathematical modeling of residual stresses in WWER-1000 elements after heat treatment

O.V. Makhnenko1, S.M. Kandala1, N.R. Basistyuk1, M.V. Cherkashin2
1E.O. Paton Electric Welding Institute of the NAS of Ukraine. 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: office@paton.kiev.ua
2«Ukrtsniitmash» Company, 7a Vasylenka Str., 03124, Kyiv, Ukraine. E-mail: ukrcniitmash@ukr.net

Determination of residual life and extension of safe operating life of WWER-1000 internals for a term of up to 60 years beyond the design period is an important scientific and engineering objective for nuclear power industry of Ukraine. During long-term operation the internal elements: reflection shield and cavity are exposed to intensive impact of damaging radiation dose that causes the processes of radiation embrittlement, swelling and creep in the material (austenitic steel 08Kh18N10T). Technological residual stresses after welding and subsequent heat treatment should be taken into account at calculation-based substantiation of the safe operating life of reactor internal elements. In the work mathematical modeling was used to derive residual stress distributions in the volume of the reflection shield and internal cavity after electroslag welding and their redistribution fields after post-weld heat treatment by autenitizing mode. It is determined that the residual welding stresses are largely relaxed during austenitizing. In the reflection shield, however, which is of complex geometry with a variable wall thickness and cooling channels, high residual stresses develop, due to occurrence of a significant temperature gradient at cooling during austenitizing. These stresses should be taken into account at determination of the residual life of WWER-1000 internals. Ref. 8, Fig. 8.
Keywords: WWER-1000, reactor internals, reflection shield, internal cavity, electroslag welding, heat treatment, austenitizing, residual stresses

Received: 01.03.2021


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