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S afety Aspects PROCEEDINGS OF A SYMPOSIUMVIENNA o f the Ageing H29 JUNE-3 U JULY H 1987 and M aintenance o f Nuclear Pow er Plants NUCLEAR POWER PLANTS REACHING 25 OR 30 YEARS OF OPERATION WITHIN YEARS 1990-2000 25 years 30 years NUCLEAR SAFETY INFORMATION CENTRE PLEASE RETURN TO ROOM B0655 3 INTERNA _____ _ nUl.i,OY, VIENNA, 1 9 8 8 NUCLEAR SAFETY INFORMATION LIBRARY PLEASE RETURN A2643 SAFETY ASPECTS OF THE AGEING AND MAINTENANCE OF NUCLEAR POWER PLANTS The following States are Members of the International Atomic Energy Agency: AFGHANISTAN GUATEMALA PARAGUAY ALBANIA « HAITI PERU ALGERIA HOLY SEE PHILIPPINES ARGENTINA HUNGARY POLAND AUSTRALIA ICELAND PORTUGAL AUSTRIA INDIA QATAR BANGLADESH INDONESIA ROMANIA BELGIUM IRAN, ISLAMIC REPUBLIC OF SAUDI ARABIA BOLIVIA IRAQ SENEGAL BRAZIL IRELAND SIERRA LEONE BULGARIA ISRAEL SINGAPORE BURMA ITA LY SOUTH AFRICA BYELORUSSIAN SOVIET JAMAICA SPAIN SOCIALIST REPUBLIC . JAPAN SRI LANKA CAMEROON JORDAN SUDAN CANADA KENYA SWEDEN CHILE KOREA, REPUBLIC OF SWITZERLAND CHINA KUW AIT SYRIAN ARAB REPUBLIC COLOMBIA LEBANON THAILAND COSTA RICA LIBERIA TUNISIA COTE D ’IVOIRE LIBYAN ARAB JAMAHIRIYA TURKEY CUBA LIECHTENSTEIN UGANDA CYPRUS LUXEMBOURG UKRAINIAN SOVIET SOCIALIST CZECHOSLOVAKIA MADAGASCAR REPUBLIC DEMOCRATIC KAMPUCHEA MALAYSIA UNION OF SOVIET SOCIALIST DEMOCRATIC PEOPLE'S MALI REPUBLICS REPUBLIC OF KOREA MAURITIUS UNITED ARAB EMIRATES DENMARK MEXICO UNITED KINGDOM OF GREAT DOMINICAN REPUBLIC MONACO BRITAIN AND NORTHERN ECUADOR MONGOLIA IRELAND EGYPT MOROCCO UNITED REPUBLIC OF EL SALVADOR NAMIBIA TANZANIA ETHIOPIA NETHERLANDS UNITED STATES OF AMERICA FINLAND NEW ZEALAND URUGUAY FRANCE NICARAGUA VENEZUELA GABON NIGER VIET NAM GERMAN DEMOCRATIC REPUBLIC NIGERIA YUGOSLAVIA GERMANY, FEDERAL REPUBLIC OF NORWAY ZAIRE GHANA PAKISTAN ZAMBIA GREECE PANAMA ZIMBABWE The Agency’s Statute was approved on 23 October 1956 by the Conference on the Statute o f the IAE A held at United Nations Headquarters, New York; it entered into force on 29 July 1957. The Headquarters o f the Agency are situated in Vienna. Its principal objective is “ to accelerate and enlarge the contribution o f atomic energy to peace, health and prosperity throughout the world". © IAEA, 1988 Permission to reproduce or translate the information contained in this publication may be obtained by writing to the International Atomic Energy Agency, Wagramerstrasse 5, P.O. Box 100, A-1400 Vienna, Austria. Printed by the IAEA in Austria January 1988 PROCEEDINGS SEMES SAFETY ASPECTS OF THE AGEING AND MAINTENANCE OF NUCLEAR POWER PLANTS PROCEEDINGS OF AN INTERNATIONAL SYMPOSIUM ON SAFETY ASPECTS OF THE AGEING AND MAINTENANCE OF NUCLEAR POWER PLANTS ORGANIZED BY THE INTERNATIONAL ATOMIC ENERGY AGENCY AND HELD IN VIENNA, 29 JUNE - 3 JULY 1987 INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 1988 SAFETY ASPECTS OF THE AGEING AND MAINTENANCE OF NUCLEAR POWER PLANTS IAEA, VIENNA, 1988 STI/PUB/759 ISBN 92-0-020088-5 FOREWORD The IAEA International Symposium on Safety Aspects of the Ageing and Main tenance of Nuclear Power Plants, held in Vienna from 29 June to 3 July 1987, was arranged with a view to providing a forum for the exchange of technical information on the approach to ageing phenomena at NPPs and for the exchange of technical and economic information on the approach to plant life extension. The symposium was attended by 141 participants from 31 countries and three international organizations. The symposium was the first organized by the IAEA on this subject. It consisted of six technical sessions, one poster session and three panel discussions. The proceed ings, which include 35 technical papers presented during the symposium and four extended synopses of posters presented, should be valuable to a broad spectrum of experts involved in nuclear power programmes: technical and managerial staff engaged in NPP operation, regulatory body staff, consulting and architect engineer ing organizations, vendor technical and managerial staff and NPP technical and managerial staff involved in maintenance activities. Some NPPs are already approaching or are even beyond the end of their planned lifetime of 25 to 40 years of operation. In the year 2000 approximately 160 plants will be 25 years old and 69 will be 30 years old or more. The question of the safe operation of rather ‘old’ plants and the question of NPP life extension as an alterna tive to decommissioning will therefore be of growing importance worldwide. Nuclear power plant equipment ageing and the consequent failure of compo nents could have a strong impact on both plant availability and safety if degradation of key components, systems and structures is not detected before loss of functional capability and if appropriate corrective measures are not taken. The ageing process also alters the probability of component failures in systems which are designed to mitigate transients and accidents and thereby reduces safety margins, possibly caus ing transients and accidents to be initiated. Ageing degradation could represent a potentially significant contribution to common cause failure of safety related equip ment during transients and accidents. Coping with the ageing process of NPPs requires a systematic approach in analysing these phenomena. Experimental and theoretical methods should be deve loped to evaluate the impact of ageing on NPP performance. Effective methods of inspection, surveillance and monitoring should be implemented during operation to evaluate the ‘qualified life’ of the components, systems and structures. This should be the basis for their timely and effective maintenance, repair and replacement, with particular attention to systems and components important to safety. There is an important relationship between safety and ageing and the availability and reliability of NPPs. With the high investment costs involved in NPPs, and with worldwide attention focused on nuclear safety, the safe and undisturbed operation of NPPs is a major concern. Owing to capital cost development, extension of the life times of existing NPPs beyond their design life may be economically justifiable even if significant capital expenditures are required to assure nuclear safety and reasonable availability. A broad spectrum of technical, economic and regulatory aspects have to be understood before decisions can be taken concerning plant life extension, but NPP life extension in the planning of nuclear power systems development was not scheduled for discussion during the symposium. The IAEA wishes to thank all those who contributed papers and took part in the general discussion; gratitude is also expressed to the chairmen of the technical sessions and panels and to participants in panel discussions. EDITORIAL NOTE The Proceedings have been edited by the editorial staff of the IAEA to the extent considered necessary for the reader's assistance. The views expressed remain, however, the responsibility of the named authors or participants. In addition, the views are not necessarily those of the governments of the nominating Member States or of the nominating organizations. Although great care has been taken to maintain the accuracy of information contained in this pub lication, neither the IAEA nor its Member States assume any responsibility for consequences which may arise from its use. 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 institu tions 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. Material prepared by authors who are in contractual relation with governments is copyrighted by the IAEA, as publisher, only to the extent permitted by the appropriate national regulations. CONTENTS GENERAL SAFETY ASPECTS OF AGEING (Session 1) United States Nuclear Regulatory Commission research program to understand aging and manage its effects in nuclear power plants (IAEA-SM-295/33) ................................................................... 3 G.A. Arlotto, J.E. Richardson, J.P. Vora Envejecimiento y seguridad (IAEA-SM-295/1).................................... 23 A. Femández-Femández, J.M. Vitale An aging failure survey of light water reactor safety systems and components (IAEA-SM-295/36)................................................... 29 P.E. MacDonald, D.G. Satterwhite, B.M. Meale, J.P. Vora CONCEPTUAL APPROACH TO THE SAFETY ASPECTS OF NPP AGEING (Session 2) Approche conceptuelle des problèmes de sûreté posés par le vieillissement des centrales nucléaires (IAEA-SM-295/15) ..................................... 49 D.B. Lévy, C. Feltin Quantitative relationships between aging failure data and risk (IAEA-SM-295/34) .................................................................... 57 W.E. Vesely, J.P. Vora Problemas comunes en centrales antiguas y estrategia regulatoria para su tratamiento (IAEA-SM-295/3) ...................................................... 77 R.E. Touzet Poster presentation Rple of the national regulatory body in evaluation of preventive maintenance efficiency in Finland (IAEA-SM-295/10P) ............................ ........