IAEA-TECDOC-1942 IAEA-TECDOC-1942 IAEA TECDOC SERIES Coolant Chemistry Control and Effects on Fuel Reliability in Pressurized Heavy Water Reactors Water Coolant Chemistry Control and Effects on Fuel Reliability in Pressurized Heavy IAEA-TECDOC-1942 Coolant Chemistry Control and Effects on Fuel Reliability in Pressurized Heavy Water Reactors Report of a Technical Meeting International Atomic Energy Agency Vienna @ COOLANT CHEMISTRY CONTROL AND EFFECTS ON FUEL RELIABILITY IN PRESSURIZED HEAVY WATER REACTORS The following States are Members of the International Atomic Energy Agency: AFGHANISTAN GEORGIA OMAN ALBANIA GERMANY PAKISTAN ALGERIA GHANA PALAU ANGOLA GREECE PANAMA ANTIGUA AND BARBUDA GRENADA PAPUA NEW GUINEA ARGENTINA GUATEMALA PARAGUAY ARMENIA GUYANA PERU AUSTRALIA HAITI PHILIPPINES AUSTRIA HOLY SEE POLAND AZERBAIJAN HONDURAS PORTUGAL BAHAMAS HUNGARY QATAR BAHRAIN ICELAND REPUBLIC OF MOLDOVA BANGLADESH INDIA ROMANIA BARBADOS INDONESIA RUSSIAN FEDERATION BELARUS IRAN, ISLAMIC REPUBLIC OF RWANDA BELGIUM IRAQ SAINT LUCIA BELIZE IRELAND BENIN ISRAEL SAINT VINCENT AND BOLIVIA, PLURINATIONAL ITALY THE GRENADINES STATE OF JAMAICA SAN MARINO BOSNIA AND HERZEGOVINA JAPAN SAUDI ARABIA BOTSWANA JORDAN SENEGAL BRAZIL KAZAKHSTAN SERBIA BRUNEI DARUSSALAM KENYA SEYCHELLES BULGARIA KOREA, REPUBLIC OF SIERRA LEONE BURKINA FASO KUWAIT SINGAPORE BURUNDI KYRGYZSTAN SLOVAKIA CAMBODIA LAO PEOPLE’S DEMOCRATIC SLOVENIA CAMEROON REPUBLIC SOUTH AFRICA CANADA LATVIA SPAIN CENTRAL AFRICAN LEBANON SRI LANKA REPUBLIC LESOTHO SUDAN CHAD LIBERIA SWEDEN CHILE LIBYA SWITZERLAND CHINA LIECHTENSTEIN SYRIAN ARAB REPUBLIC COLOMBIA LITHUANIA TAJIKISTAN COMOROS LUXEMBOURG THAILAND CONGO MADAGASCAR TOGO COSTA RICA MALAWI TRINIDAD AND TOBAGO CÔTE D’IVOIRE MALAYSIA TUNISIA CROATIA MALI TURKEY CUBA MALTA TURKMENISTAN CYPRUS MARSHALL ISLANDS UGANDA CZECH REPUBLIC MAURITANIA UKRAINE DEMOCRATIC REPUBLIC MAURITIUS UNITED ARAB EMIRATES OF THE CONGO MEXICO UNITED KINGDOM OF DENMARK MONACO DJIBOUTI MONGOLIA GREAT BRITAIN AND DOMINICA MONTENEGRO NORTHERN IRELAND DOMINICAN REPUBLIC MOROCCO UNITED REPUBLIC ECUADOR MOZAMBIQUE OF TANZANIA EGYPT MYANMAR UNITED STATES OF AMERICA EL SALVADOR NAMIBIA URUGUAY ERITREA NEPAL UZBEKISTAN ESTONIA NETHERLANDS VANUATU ESWATINI NEW ZEALAND VENEZUELA, BOLIVARIAN ETHIOPIA NICARAGUA REPUBLIC OF FIJI NIGER VIET NAM FINLAND NIGERIA YEMEN FRANCE NORTH MACEDONIA ZAMBIA GABON NORWAY ZIMBABWE The Agency’s Statute was approved on 23 October 1956 by the Conference on the Statute of the IAEA held at United Nations Headquarters, New York; it entered into force on 29 July 1957. The Headquarters of the Agency are situated in Vienna. Its principal objective is “to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world’’. IAEA-TECDOC-1942 COOLANT CHEMISTRY CONTROL AND EFFECTS ON FUEL RELIABILITY IN PRESSURIZED HEAVY WATER REACTORS REPORT OF A TECHNICAL MEETING INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 2021 COPYRIGHT NOTICE All IAEA scientific and technical publications are protected by the terms of the Universal Copyright Convention as adopted in 1952 (Berne) and as revised in 1972 (Paris). The copyright has since been extended by the World Intellectual Property Organization (Geneva) to include electronic and virtual intellectual property. Permission to use whole or parts of texts contained in IAEA publications in printed or electronic form must be obtained and is usually subject to royalty agreements. Proposals for non-commercial reproductions and translations are welcomed and considered on a case-by-case basis. Enquiries should be addressed to the IAEA Publishing Section at: Marketing and Sales Unit, Publishing Section International Atomic Energy Agency Vienna International Centre PO Box 100 1400 Vienna, Austria fax: +43 1 26007 22529 tel.: +43 1 2600 22417 email: [email protected] www.iaea.org/publications For further information on this publication, please contact: Nuclear Fuel Cycle and Materials Section International Atomic Energy Agency Vienna International Centre PO Box 100 1400 Vienna, Austria Email: [email protected] © IAEA, 2021 Printed by the IAEA in Austria February 2021 IAEA Library Cataloguing in Publication Data Names: International Atomic Energy Agency. Title: Coolant chemistry control and effects on fuel reliability in pressurized heavy water reactors / International Atomic Energy Agency. Description: Vienna : International Atomic Energy Agency, 2021. | Series: IAEA TECDOC series, ISSN 1011–4289 ; no. 1942 | Includes bibliographical references. Identifiers: IAEAL 21-01382 | ISBN 978-92-0-134021-4 (paperback : alk. paper) | ISBN 978-92-0-133921-8 (pdf) Subjects: LCSH: Nuclear reactors — Cooling. | Pressurized water reactors. | Nuclear fuels. | Corrosion. FOREWORD The structural materials of the primary circuit of pressurized heavy water reactors (PHWRs) experience corrosion as they are exposed to the coolant. Passive oxide layers formed on the structural materials are dissolved to some extent in the coolant and transported as corrosion products throughout the primary circuit. These soluble and insoluble corrosion products can be deposited on fuel cladding surfaces. For PHWRs with natural uranium fuel and with specific coolant chemistry control, it has been accepted that corrosion deposits on the fuel cladding are relatively harmless for the fuel integrity, unlike for light water reactors. This may be dependent on the physical form and location of the deposits and their possible influence on the heat transfer. However, in 2008, a power reactor operator in Canada discovered black deposits on the fuel cladding, which increased interest in the significance of corrosion deposits. These observations of deposits on fuel bundles discharged from the reactor have raised concerns regarding operational safety (e.g. an increase of local cladding temperature, leading to a reduction of margin to dryout) in operating PHWRs. To minimize the impact of fuel deposits on fuel fitness for service, coolant chemistry control may need to be reoptimized. In PHWRs, coolant chemistry control is achieved mainly through dosing and control of the ‘apparent pH’ of the primary coolant pHa and the deuterium concentration by adjusting the concentration of lithium and hydrogen, as appropriate. It also needs to be noted that concentration of lithium under fuel bundle bearing pads could lead to crevice corrosion, localized over relatively small regions such as areas of low flow or stagnation, and potentially cause fuel failures and pressure tube damage. The present publication is based on the presentations and discussions from the Technical Meeting on the Control and Monitoring of Coolant Chemistry and Related Issues on Fuel Reliability in Pressurized Heavy Water Reactors, organized by the IAEA and held in Toronto, Canada, on 25–28 November 2019. The publication provides information on national practices to control the coolant chemistry under various operating conditions and R&D programmes to understand the corrosion phenomena and their influence on fuel fitness for service in the primary heat transport system of PHWRs. The IAEA wishes to thank all the participants in the technical meeting for their active involvement and presentations, as well as the subject matter experts, including J.G. Roberts (Canada), D. Lister (Canada), R. Srinivasan (India) and P. Chan (Canada), for their valuable contributions to the drafting of this publication. Special acknowledgement is given to the Canadian Nuclear Safety Commission for hosting the technical meeting and the CANDU Owners Group for providing the venue. The IAEA officer responsible for this publication was K. Sim of the Division of Nuclear Fuel Cycle and Waste Technology. EDITORIAL NOTE This publication has been prepared from the original material as submitted by the contributors and has not been edited by the editorial staff of the IAEA. The views expressed remain the responsibility of the contributors and do not necessarily represent the views of the IAEA or its Member States. Neither the IAEA nor its Member States assume any responsibility for consequences which may arise from the use of this publication. This publication does not address questions of responsibility, legal or otherwise, for acts or omissions on the part of any person. The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries. The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA. The authors are responsible for having obtained the necessary permission for the IAEA to reproduce, translate or use material from sources already protected by copyrights. The IAEA has no responsibility for the persistence or accuracy of URLs for external or third party Internet web sites referred to in this publication and does not guarantee that any content on such web sites is, or will remain, accurate or appropriate. CONTENTS 1. INTRODUCTION ........................................................................................................................................ 1 1.1. Background......................................................................................................................................