PSI - Issue 59

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 59 (2024) 36–42

© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers Abstract In-Vessel Melt Retention (IVMR) strategy is wildly recognized all over the world as a conception for mitigation the Severe Accidents (SA) with complete core melting. The idea is to cool the external reactor pressure vessel (RPV) wall by flooding the cavity if the core is melted during the accident. Implementation of this strategy started in the last decade of twenty century for a medium-power reactors like WWER-440 and AP-600. It was proved that such type of reactors have a good margin and as the main thermal failure criteria was used, i.e. boiling crisis. Of course, thermal failure mechanism will be main if the reactor is depressurized. Boiling crisis might happen if the heat flux through the RPV wall exceed the critical heat flux value, thus the flow regime suddenly changes from nucleate boiling to film boiling. As a supplementary criterion, a residual wall thickness was used. It is obvious that the reactor wall should not be melted through by the core, especially considering the „focusing effect‟ of the upper metallic level. The residual wall thickness becomes more important if IVMR strategy is applied for a high-power reactor like WWER-1000. Nevertheless, exist an ambiguity in residual wall thickness analysis, due to RPV steel corrosion at interaction with molten corium. It was shown that due to corrosion the wall thickness can be lower, which may accelerate other damage mechanisms. The present work investigates the possible acceleration of RPV failure due to interaction of creep and corrosion. The work is performed using 2D FE model of RPV wall with a complete melted corium. It is shown that corrosion consideration has no effect to the reactor wall carrying capacity, since only hardly damaged elements near the corium are excluded. © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers VII International Conference “In -service Damage of Materials: Diagnostics and Prediction ” (DMDP 2023) In-Vessel Melt Retention analysis of WWER reactor with consideration of corrosion processes Yaroslav Dubyk a,b *, Olha Zvirko b a IPP-CENTRE, 5B, Budindustrii Str. Kyiv 01013, Ukraine b Karpenko Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Naukova St. 5, Lviv 79060, Ukraine

* Corresponding author. Tel.: +38 (044) 502-45-70. E-mail address: dubyk-yr@ipp-centre.com.ua

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers 10.1016/j.prostr.2024.04.007