spine: 5.455 mm 81 pages OECD–IAEA Paks Fuel Project Final Report INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA 09-2210-PUB-1389-cover.indd 1 2010-06-29 10:12:33 OECD–IAEA PAKS FUEL PROJECT The following States are Members of the International Atomic Energy Agency: AFGHANISTAN GHANA NIGERIA ALBANIA GREECE NORWAY ALGERIA GUATEMALA OMAN ANGOLA HAITI PAKISTAN ARGENTINA HOLY SEE PALAU ARMENIA HONDURAS PANAMA AUSTRALIA HUNGARY PARAGUAY AUSTRIA ICELAND PERU AZERBAIJAN INDIA PHILIPPINES BAHRAIN INDONESIA POLAND BANGLADESH IRAN, ISLAMIC REPUBLIC OF PORTUGAL BELARUS IRAQ QATAR BELGIUM IRELAND REPUBLIC OF MOLDOVA BELIZE ISRAEL ROMANIA BENIN ITALY RUSSIAN FEDERATION BOLIVIA JAMAICA SAUDI ARABIA BOSNIA AND HERZEGOVINA JAPAN SENEGAL BOTSWANA JORDAN SERBIA BRAZIL KAZAKHSTAN SEYCHELLES BULGARIA KENYA SIERRA LEONE BURKINA FASO KOREA, REPUBLIC OF SINGAPORE BURUNDI KUWAIT SLOVAKIA CAMEROON KYRGYZSTAN SLOVENIA CANADA LATVIA SOUTH AFRICA CENTRAL AFRICAN LEBANON SPAIN REPUBLIC LESOTHO SRI LANKA CHAD LIBERIA SUDAN CHILE LIBYAN ARAB JAMAHIRIYA SWEDEN CHINA LIECHTENSTEIN SWITZERLAND COLOMBIA LITHUANIA SYRIAN ARAB REPUBLIC CONGO LUXEMBOURG TAJIKISTAN COSTA RICA MADAGASCAR THAILAND CÔTE D’IVOIRE MALAWI THE FORMER YUGOSLAV CROATIA MALAYSIA REPUBLIC OF MACEDONIA CUBA MALI TUNISIA CYPRUS MALTA TURKEY CZECH REPUBLIC MARSHALL ISLANDS UGANDA DEMOCRATIC REPUBLIC MAURITANIA UKRAINE OF THE CONGO MAURITIUS UNITED ARAB EMIRATES DENMARK MEXICO UNITED KINGDOM OF DOMINICAN REPUBLIC MONACO GREAT BRITAIN AND ECUADOR MONGOLIA NORTHERN IRELAND EGYPT MONTENEGRO UNITED REPUBLIC EL SALVADOR MOROCCO OF TANZANIA ERITREA MOZAMBIQUE UNITED STATES OF AMERICA ESTONIA MYANMAR URUGUAY ETHIOPIA NAMIBIA UZBEKISTAN FINLAND NEPAL VENEZUELA FRANCE NETHERLANDS VIETNAM GABON NEW ZEALAND YEMEN GEORGIA NICARAGUA ZAMBIA GERMANY NIGER 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’’. OECD–IAEA PAKS FUEL PROJECT FINAL REPORT INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 2009 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: Sales and Promotion, Publishing Section International Atomic Energy Agency Vienna International Centre PO Box 100 1400 Vienna, Austria fax: +43 1 2600 29302 tel.: +43 1 2600 22417 email: [email protected] http://www.iaea.org/books For further information on this publication, please contact: Safety Assessment Section International Atomic Energy Agency Vienna International Centre PO Box 100 1400 Vienna, Austria email: [email protected] OECD–IAEA PAKS FUEL PROJECT IAEA, VIENNA, 2010 © IAEA, 2010 Printed by the IAEA in Austria May 2010 FOREWORD It is important for nuclear power plant designers, operators and regulators to effectively use lessons learned from events occurring at nuclear power plants since, in general, it is impossible to reproduce the event using experimental facilities. In particular, evaluation of the event using accident analysis codes is expected to contribute to improving understanding of phenomena during the events and to facilitate the validation of computer codes through simulation analyses. The information presented in this publication will be of use in future revisions of safety guides on accident analysis. During a fuel crud removal operation on the Paks-2 unit of the Paks nuclear power plant, Hungary on 10 April 2003, several fuel assemblies were severely damaged. The assemblies were being cleaned in a special tank under deep water in a service pit connected to the spent fuel storage pool. The first sign of fuel failures was the detection of some fission gases released from the cleaning tank. Later, visual inspection revealed that most of the 30 fuel assemblies suffered heavy oxidation and fragmentation. The first evaluation of the event showed that the severe fuel damage had been caused by inadequate cooling. The Paks-2 event was discussed in various committees of the OECD Nuclear Energy Agency (OECD/NEA) and of the International Atomic Energy Agency (IAEA). Recommendations were made to undertake actions to improve the understanding of the incident sequence and of the consequence this had on the fuel. It was considered that the Paks-2 event may constitute a useful case for a comparative exercise on safety codes, in particular for models devised to predict fuel damage and potential releases under abnormal cooling conditions and the analyses of the Paks-2 event may provide information which is relevant for in-reactor and spent fuel storage safety evaluations. The OECD-IAEA Paks Fuel Project was established in 2005 as a joint project between the IAEA and the OECD/NEA. The IAEA provided financial support to the operating agent (Hungarian Academy of Sciences KFKI Atomic Energy Research Institute (AEKI)) and reviewed the progress of the project within the framework of Technical Cooperation Project, RER9076, on Strengthening Safety and Reliability of Fuel and Material in Nuclear Power Plants. Thirty organizations from sixteen countries participated in the project. The following participants performed analyses of the event using numerical models based on a common database: • AEKI (Hungary), • SUEZ – TRACTEBEL ENGINEERING • BME NTI (Hungary), (Belgium), • GRS (Germany), • NRC (United States of America), • IRSN (France), • VEIKI (Hungary), • IVS (Slovakia), • VTT (Finland), • KI (Russian Federation), • VUJE (Slovakia). The main results of calculations are summarized in the present report. The IAEA and the OECD/NEA acknowledge the work of the participating experts and wish to thank them for their valuable contributions to this publication. In particular, the work of Z. Hozer in compiling the report is gratefully acknowledged, as well as N. Tricot for completing the final stages of preparation. The corresponding report has been issued as an NEA/CSNI publication as NEA/CSNI/R(2008)2. The IAEA and the OECD/NEA officers responsible for the preparation of this publication were Y. Makihara and C. Vitanza, respectively. 1 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 EXECUTIVE SUMMARY........................................................................................................ 1 1 INTRODUCTION ........................................................................................................... 1\ 1.1. Background......................................................................................................... 1 1.2. Structure.............................................................................................................. 4 2 DESCRIPTION OF THE INCIDENT.............................................................................. 5 2.1 Preliminaries....................................................................................................... 5 2.2 Operation of the cleaning tank............................................................................ 7 2.3 Chronology of the incident............................................................................... 10 2.3.1 Formation of steam volume .................................................................. 11 2.3.2 Plastic deformation of cladding and high temperature oxidation ......... 12 2.3.3 Quench.................................................................................................. 13 2.4 State of damaged fuel ....................................................................................... 14 2.5 Post-incident investigations.............................................................................. 15 2.6 The recovery work............................................................................................ 16 3 MAJOR RESULTS OF ANALYSES............................................................................. 18 3.1 Participant SUEZ - TRACTEBEL ENGINEERING ....................................... 19 3.1.1 Code description................................................................................... 19 3.1.2 Model description................................................................................. 20 3.1.3 Chronology of main events................................................................... 22 3.1.4 Conclusions..........................................................................................