PSI - Issue 60

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

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 60 (2024) 311–323

Third International Conference on Structural Integrity 2023 (ICONS 2023) Embrittlement of Cr-Mo-V-Ni Steel for Reactor Pressure Vessel Applications Under In-Situ Hydrogen Electrochemical Charging Gopal Sanyal a , Chiradeep Gupta a* , Ram Niwas Singh a

a Mechanical Metallurgy Division, Bhabha Atomic Research Centre, Mumbai 400085, India.

© 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 the ICONS 2023 Organizers Abstract The hydrogen embrittlement of reactor pressure vessel (RPV) steel is studied using in-situ testing techniques. Hydrogen pickup by reactor vessel of pressurized water nuclear reactor during service through radiolysis of coolant water and local corrosion reactions may be of concern for long term safety. The combined action of coolant pressure, temperature and radiation during service are expected to increase the probability for hydrogen embrittlement (HE) of the reactor pressure vessel (RPV) steel. In-situ mechanical test with electrochemical charging provides most apt condition for assessing severe manifestations of HE under dynamic variation of stress. For this purpose,mechanical tests were carried out at 25°Con Cr-Mo-V-Ni steel for VVER (Water-Water Energy Reactor) RPV applications with specimens immersed in electrolytic bath setup. The experiments were carried out at different current densities in a bath of 1N-H 2 SO 4 by employing very slow pull rates of the UTM where severe manifestations of HE is reported in steels. It was found that for tensile tests using slow pull rates, the lowering of ductility in terms of reduction of area is ~ 90% or greater for current density range of 20 – 400 mA/cm 2 at strain rate of 8.3x10 -6 s -1 . Under these conditions the fracture toughness in the K Jc format reduced by about 50%. The significant reduction of tensile and fracture properties as a result of in-situ electrochemical charging could be rationalised to the change in fracture mode from ductile dimpled failure to brittle intergranular failure. The nature of fracture surfaces suggested that failure is likely to be due to embrittlement bydecohesion mechanism in Cr-Mo-V-Ni steel due to in-situ electrochemical hydrogen charging . © 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 the ICONS 2023 Organizers Keywords: Hydrogen Embrittlement; Reactor pressure vessel steel; In-situ electrochemical charging; HEDE; Slow strain rate tensile test *Corresponding Author , Email : cgupta@barc.gov.in

2452-3216© 2024 The Authors. Published by ELSEVIER B.V.* Corresponding author . Email: cgupta@barc.gov.in 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 the ICONS 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 the ICONS 2023 Organizers 10.1016/j.prostr.2024.05.052