Liquid high-level radioactive wastes are currently being stored in carbon steel tanks at the Hanford Site. The waste storage was originally initiated in single-shell tanks (SSTs) that were not stress relieved. One of the safety initiatives identified for accelerating resolution of waste tank safety issues at the Hanford Site required determination of failure mechanisms and corrosion control options to minimize further degradation of the SSTs. This paper deals with an assessment of Hanford Site SST degradation by a literature survey of carbon steel data in environments similar to the SST wastes, and also by a review of the work performed at the Savannah River Site (SRS), where similar wastes are stored in similar carbon steel tanks. TMs approach indicated that in Mgh nitrate (NO3−) wastes containing insufficient quantities of hydroxide (OH−) and nitrite (NO2−), carbon steel will fail by stress corrosion cracking (SCC) especially in weld heat affected zones. Support for the above conclusion is obtained from correlation studies performed on the waste types stored in the SSTs vs the leak status of these tanks. In addition, carbon steels are expected to corrode by pitting in crevices if the OH− concentration is reduced below a pH value of 10. The paper also includes a discussion of some specific and general recommendations for corrosion control in SSTs.

Subject
Composition, Corrosion rate, Walls, Leaks, Vapors, Liquids, Mechanical failure, Interfaces, Pitting, Carbon steel, Wastes, Corrosion potential, Stress corrosion cracking
Keywords:
single-shell tanks, carbon steel, stress corrosion cracking, liquid high-level radioactive wastes, sludge, salt cake, corrosion inhibitor, Hanford
© 1995 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).
1995
Association for Materials Protection and Performance (AMPP)
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