Surveys of steam generator tube failures in water-cooled power reactors have shown that some failures were caused by intergranular stress corrosion cracking (SCC) of Inconel-600 tubes[1,2]. The cracks initiated from the secondary side in regions of poor circulation. Failures were observed in steam generators on all volatile treatment (AVT)[3], on congruent phosphate treatment[4] and during transition from one type of chemical treatment to the other[5]. It is believed that SCC was caused by excessive hydroxide alkalinity in the steam generator produced by leakage of condenser cooling water or by high sodium to phosphate molar ratios (>2.85)[4,5]. Free hydroxide concentrated on the tube surfaces in poorly wetted crevices or within the sludge on the tubesheet and attacked the tube material. Only a small fraction of the total number of tubes in service have failed by this mechanism. However, since the failure of even one steam generator tube can lead to an expensive shutdown of the station, it is important to understand the factors which influence the SCC of tube materials in sodium hydroxide (caustic) solutions.

Subject
Materials, Hydrogen concentration, Tubes, Steam generators, Stress cracking, Thermal stress, Intergranular cracking, Stress, C ring stress corrosion testing, Heat, Sodium hydroxide, Heat treatment, Stress corrosion cracking
© 1978 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1978
Association for Materials Protection and Performance (AMPP)
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