Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Assessment of risks of damage of welded joint of manifold and steam generator connection sleeve for NPP with VVER

12/25/2016 2016 - #04 Global safety, reliability and diagnostics of nuclear power installations

Netyaga N.N. Saakyan S.P. Povarov V.P.

DOI: https://doi.org/10.26583/npe.2016.4.04

UDC: 621.311.25

The problems of determining the risks of failure of equipment of operating NPP and, particularly, plants with a long service life are highly relevant especially in association with approaching expiration of the design service life (25 – 30 years) of power units of NPPs in the RF, as well as with extended design service life of the newly built power units (up to 60 years). Expiration of the design service life of existing NPPs, as well as extension of design service life of the newly built power units predetermine the need to develop new approaches in order to ensure reliable and safe operation of the most critical elements of the thermal and mechanical equipment and pipelines.

One of such elements is the welded junction (WJ) zone No. 111 where hot collector is welded to the vessel of steam generator where development of operational defects is possible, and these defects are systematic in nature and affect safety of operation of the whole power unit.

Statistics of failures in WJ zone No. 111 between the hot and cold manifolds of the steam generator to the DU-1200 pipeline for VVER reactors is given in the present paper. Classification of approaching limiting conditions of failures is suggested for WJ zone No. 111 of the steam generator. Calculation of risk for the power unit in case of development of one of the limiting conditions was performed. The size of losses in cases of damage of the welding joint of a manifold with steam generator connection sleeve in a zone WJ No. 111 is considerable. The probability of emergence of unacceptable defects within zone WJ No. 111 remains to be very high and requires undertaking measures for controlling the moment of their initiation and development.

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steam generator manifold refusal damage risk zone of a welded joint