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Spent Fuel Performance Assessment and Research

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Spent Fuel Performance Assessment and Research IAEA-TECDOC-1343 Spent fuel performance assessment and research Final report of a Co-ordinated Research Project on Spent Fuel Performance Assessment and Research (SPAR) 1997–2001 March 2003 The originating Section of this publication in the IAEA was: Nuclear Fuel Cycle and Materials Section International Atomic Energy Agency Wagramer Strasse 5 P.O. Box 100 A-1400 Vienna, Austria SPENT FUEL PERFORMANCE ASSESSMENT AND RESEARCH IAEA, VIENNA, 2003 IAEA-TECDOC-1343 ISBN 92–0–102703–6 ISSN 1011–4289 © IAEA, 2003 Printed by the IAEA in Austria March 2003 FOREWORD As of the beginning of 2002, more than 150 000 Mg U spent fuel is currently being stored in various storage facilities. Most of this fuel is under water, but dry storage is becoming a widely used technology with more than 9000 Mg U currently stored in various countries. In the future spent fuel storage capacity needs will continue to increase and some of these fuels will have to be stored for 50 years or more, before their reprocessing or final disposal takes place. As a result, interim storage for long periods of time will continue to be a key technology for all Member States. A number of countries are planning or have already initiated research programmes on spent fuel storage performance, or are developing a high confidence database which evaluates the storage of spent fuel for extremely long periods of time, to determine their consequence on disposal. Spent fuel storage technology (particularly dry storage) is undergoing a rapid evolution, new fuel and material design changes are coming on stream and target burnups are steadily increasing. These improvements will ask for new studies and potential adaptations of the storage technologies currently used. As a consequence, the IAEA initiated in 1997 a Co-ordinated Research Project on Spent Fuel Performance Assessment and Research (SPAR) to collect and exchange spent fuel storage experience of the participating countries, to build a comprehensive international database supporting the licensing of present and future technologies; to carry out research work which will evaluate and justify the storage of spent fuel for extremely long periods of time (more than 50 years); and to assist in defining how the requirements for spent fuel storage and for the whole back end of the fuel cycle are connected. The present publication is based on results obtained in the participating countries. The draft manuscript was prepared and discussed during the last research co-ordination meeting, held in Cordoba, Spain, 1–5 October 2001, and finalized at a consultants meeting in February 2002. The report provides an overview of technical issues related to spent fuel wet and dry storage and summarizes the objectives and major findings of research, carried out within the framework of the CRP. The IAEA gratefully acknowledges the contribution of the CRP participants and the consultants who participated in the drafting and review of the report. The IAEA staff member responsible for this publication was H.P. Dyck of the Division of Nuclear Fuel Cycle and Waste Technology. EDITORIAL NOTE 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. CONTENTS 1. INTRODUCTION AND OBJECTIVES............................................................................ 1 2. HISTORY OF THE BEFAST AND SPAR CO-ORDINATED RESEARCH PROJECTS .................................................................... 2 3. WET STORAGE ................................................................................................................ 4 3.1. Spent fuel storage experience.................................................................................... 4 3.1.1. General performance...................................................................................... 4 3.1.2. Wet storage experience in the participating countries ................................... 5 3.2. Pool water chemistry................................................................................................. 9 3.2.1. Water quality control ................................................................................... 14 3.2.2. Sources of pool water activity...................................................................... 15 3.3. Inactive content ....................................................................................................... 16 3.3.1. Sources of pool water particulates ............................................................... 17 3.3.2. Water treatment............................................................................................ 17 3.3.3. Water temperature........................................................................................ 18 3.4. Pool components and materials............................................................................... 18 3.4.1. Pool lining.................................................................................................... 18 3.4.2. Storage racks................................................................................................ 19 4. DRY STORAGE .............................................................................................................. 19 4.1. Introduction ............................................................................................................. 19 4.2. Dry storage status and experience........................................................................... 21 4.3. Research activities related to dry storage................................................................ 26 5. SOURCE TERMS ............................................................................................................ 30 5.1. Subcriticality ........................................................................................................... 31 5.2. Thermal calculations ............................................................................................... 32 5.3. Radiation sources .................................................................................................... 32 5.4. Aspects associated with high burnup fuel ............................................................... 33 5.5. Aspects associated with burnup credit .................................................................... 35 6. FUEL INTEGRITY.......................................................................................................... 38 6.1. Definition of fuel integrity ...................................................................................... 38 6.1.1. Loss of fuel cladding integrity ..................................................................... 41 6.1.2. Loss of fuel assembly lifting features .......................................................... 41 6.1.3. Geometrical rearrangement of a fuel assembly ........................................... 41 6.2. Determination of spent fuel integrity ...................................................................... 41 6.2.1. At reactor detection systems ........................................................................ 41 6.2.2. Away from reactor detection systems.......................................................... 44 6.3. Criteria..................................................................................................................... 45 6.3.1. Utilities......................................................................................................... 45 6.3.2. Transportation.............................................................................................. 45 6.3.3. AFR facilities............................................................................................... 45 7. FUEL ASSEMBLY DEGRADATION MECHANISMS IN DRY AND WET STORAGE ........................................................................................... 45 7.1. Degradation mechanisms of fuel assembly components......................................... 45 7.1.1. LWR............................................................................................................. 45 7.1.2. AGR............................................................................................................. 46 7.1.3. Magnox ........................................................................................................ 47 7.1.4. CANDU....................................................................................................... 47 7.1.5. RMBK andWWER-440/1000...................................................................... 49 7.2. Degradation mechanisms affecting the fuel cladding ............................................. 49 7.2.1. LWR............................................................................................................. 49 7.2.2. Wet storage .................................................................................................. 50 7.2.3. Dry storage................................................................................................... 51 7.2.4. AGR............................................................................................................. 57 7.2.5.
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