Ageing Nuclear Power Plants

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<ul><li><p> IAEA-TECDOC-1361 </p><p>Assessment and management of ageing of major nuclear </p><p>power plant components important to safety </p><p>Primary piping in PWRs </p><p>July 2003 </p></li><li><p> The originating Section of this publication in the IAEA was: </p><p>Engineering Safety Section International Atomic Energy Agency </p><p>Wagramer Strasse 5 P.O. Box 100 </p><p>A-1400 Vienna, Austria </p><p>ASSESSMENT AND MANAGEMENT OF AGEING OF MAJOR NUCLEAR POWER PLANT COMPONENTS IMPORTANT TO SAFETY </p><p>IAEA, VIENNA, 2003 IAEA-TECDOC-1361 </p><p>ISBN 9201080034ISSN 10114289 </p><p> IAEA, 2003 </p><p>Printed by the IAEA in Austria July 2003 </p></li><li><p>FOREWORD </p><p>At present, there are over four hundred operational nuclear power plants (NPPs) in IAEA Member States. Operating experience has shown that ineffective control of the ageing degradation of the major NPP components (caused for instance by unanticipated phenomena and by operating, maintenance or manufacturing errors) can jeopardize plant safety and also plant life. Ageing in these NPPs must therefore be effectively managed to ensure the availability of design functions throughout the plant service life. From the safety perspective, this means controlling, within acceptable limits, the ageing degradation and wearout of plant components important to safety so that adequate safety margins remain, i.e. integrity and functional capability in excess of normal operating requirements. </p><p>This TECDOC is one in a series of reports on the assessment and management of ageing of the major NPP components important to safety. The reports are based on experience and practices of NPP operators, regulators, designers, manufacturers, technical support organizations and a widely accepted Methodology for the Management of Ageing of NPP Components Important to Safety, which was issued by the IAEA in 1992. Since the reports are written from a safety perspective, they do not address life or life cycle management of plant components, which involves economic considerations. </p><p>The current practices for the assessment of safety margins (fitness-for-service) and the inspection, monitoring and mitigation of ageing degradation of selected components of Canada deuteriumuranium (CANDU) reactors, boiling water reactors (BWRs), pressurized water reactors (PWRs), and water moderated, water cooled energy reactors (WWERs) are documented in the reports. These practices are intended to help all involved directly and indirectly in ensuring the safe operation of NPPs, and to provide a common technical basis for dialogue between plant operators and regulators when dealing with age-related licensing issues. The guidance reports are directed at technical experts from NPPs and from regulatory, plant design, manufacturing and technical support organizations dealing with specific plant components addressed in the reports. </p><p>This report addresses the primary piping in PWRs including main coolant piping, surge and spray lines, Class 1 piping in attached systems, and small diameter piping that cannot be isolated from the primary coolant system. Maintaining the structural integrity of this piping throughout NPP service life in spite of several ageing mechanisms is essential for plant safety. </p><p>The work of all contributors to the drafting and review of this publication, identified at the end, is greatly appreciated. In particular, the IAEA would like to acknowledge the contributions of C. Faidy (EdF, France), J. Schmidt (Siemens, Germany), and V. Shah (ANL, USA). The IAEA officer responsible for the preparation of the report was J. Pachner of the Division of Nuclear Installation Safety. </p></li><li><p>EDITORIAL NOTE </p><p>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. </p><p>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. </p></li><li><p> CONTENTS </p><p>1. INTRODUCTION.................................................................................................................. 1 </p><p>1.1. Background................................................................................................................ 1 1.2. Objective.................................................................................................................... 3 1.3. Scope.......................................................................................................................... 3 1.4. Structure..................................................................................................................... 4 </p><p>References to Section 1 .............................................................................................................. 4 </p><p>2. DESCRIPTION: DESIGN, MATERIALS, FABRICATION, AND WATER CHEMISTRY......................................................................................................... 6 </p><p>2.1. US design and materials ............................................................................................ 6 2.1.1. Main coolant loop piping design ................................................................... 6 2.1.2. Surge and spray line design and materials .................................................... 9 2.1.3. Charging system design and materials ........................................................ 16 2.1.4. Safety injection system design and materials.............................................. 17 2.1.5. Design and materials of residual heat removal system ............................... 20 </p><p>2.2. French design........................................................................................................... 24 2.3. Japanese design........................................................................................................ 25 2.4. German design ......................................................................................................... 26 2.5. Russian design ......................................................................................................... 30 </p><p>2.5.1. WWER 440 ................................................................................................. 30 2.5.2. WWER 1000 ............................................................................................... 37 </p><p>2.6. Main coolant loop piping materials and fabrication ................................................ 39 2.6.1. Clad carbon steel main coolant loop piping ................................................ 40 2.6.2. Stainless steel main coolant loop piping ..................................................... 51 2.6.3. Dissimilar metal welds ................................................................................ 53 </p><p>2.7. Pre-service inspections ............................................................................................ 54 2.8. Pre-service testing.................................................................................................... 60 2.9. Reactor coolant system water chemistry ................................................................. 60 </p><p>References to Section 2 ............................................................................................................ 61 </p><p>3. DESIGN BASIS: REGULATIONS, CODES AND GUIDES ............................................ 62 </p><p>3.1. US Regulations, codes and standards ...................................................................... 62 3.1.1. US regulations ............................................................................................. 62 3.1.2. US referenced codes and standards ............................................................. 63 3.1.3. Other US codes and standards..................................................................... 63 </p><p>3.2. Regulations, codes and standards in other countries ............................................... 63 3.3. Design basis (expected) transients ........................................................................... 64 3.4. Design fatigue analysis of piping............................................................................. 69 </p><p>3.4.1. Present ASME Code Design Requirements ................................................ 69 3.4.2. Fatigue analysis practice in Germany ......................................................... 70 3.4.3. Fatigue analysis practice in France ............................................................. 70 </p><p>3.5. Assessment of fracture toughness............................................................................ 70 References to Section 3 ............................................................................................................ 72 </p><p>4. AGEING MECHANISMS AND OPERATING EXPERIENCE ........................................ 73 </p><p>4.1. Thermal fatigue of pipes and nozzles ...................................................................... 74 </p></li><li><p> 4.1.1. Thermal fatigue of surge line ...................................................................... 74 4.1.2. Thermal fatigue of spray line and nozzles................................................... 82 4.1.3. Thermal fatigue of other connected lines .................................................... 84 4.1.4. Thermal fatigue of dissimilar metal welds ................................................ 102 </p><p>4.2. Vibratory fatigue of small lines ............................................................................. 104 4.2.1. Excitation mechanisms.............................................................................. 106 4.2.2. Characteristics of socket welds ................................................................. 106 4.2.3. Experience in the USA.............................................................................. 108 4.2.4. French experience...................................................................................... 111 </p><p>4.3. Thermal ageing of cast stainless steel piping and welds ....................................... 111 4.3.1. Thermal ageing of cast stainless steel piping ............................................ 112 4.3.2. Thermal ageing of austenitic stainless steel welds .................................... 117 </p><p>4.4. Primary water stress corrosion cracking of alloy 600............................................ 118 4.4.1. Initiation key parameters ........................................................................... 118 4.4.2. Crack growth rate key parameters............................................................. 120 4.4.3. Primary water stress corrosion cracking operating experience ............ 122 </p><p>4.5. Boric acid corrosion............................................................................................... 125 4.6. Atmospheric corrosion........................................................................................... 126 </p><p>References to Section 4 .......................................................................................................... 127 </p><p>5. ASSESSMENT METHODS.............................................................................................. 133 </p><p>5.1. Assessment of thermal fatigue............................................................................... 133 5.1.1. Fatigue analysis of piping by ASME code method................................... 133 5.1.2. Thermal fatigue assessment of surge line.................................................. 148 5.1.3. Thermal fatigue assessment of branch lines and connections................... 152 5.1.4. Consequences of fatigue damage on dynamic load carrying capacity </p><p>of pipings .................................................................................................. 154 5.2. Assessment of vibratory fatigue of piping connections......................................... 154 5.3. Assessment of thermal ageing ............................................................................... 156 </p><p>5.3.1. Cast stainless ............................................................................................. 156 5.3.2. Stainless steel welds .................................................................................. 162 </p><p>5.4. Primary water stress corrosion cracking of alloy 600............................................ 162 5.4.1. Crack initiation .......................................................................................... 162 5.4.2. Crack growth ............................................................................................. 163 </p><p>5.5. Assessment of boric acid corrosion ....................................................................... 166 5.6. Assessment of atmospheric corrosion of dissimilar metal welds .......................... 166 5.7. Leak-before-break analysis.................................................................................... 167 </p><p>5.7.1. The approach in the USA .......................................................................... 167 5.7.2. The approach in Germany ......................................................................... 169 5.7.3. The approach in France ............................................................................. 174 5.7.4. The approach in Japan............................................................................... 177 5.7.5. Russian approach....................................................................................... 178 5.7.6. Calibration of leak detection system (LDS) .............................................. 178 5.7.7. Check of leak/break reaction forces .......................................................... 179 5.7.8. LBB safety margins................................................................................... 179 5.7.9. Toughness assessment............................................................................... 179 </p><p>References to Section 5 .......................................................................................................... 183 </p><p>6. INSPECTION, MONITORING AND LEAK DETECTION ............................................ 187 </p></li><li><p> 6.1. Inspections of PWR primary piping ...................................................................... 187 6.1.1. Inspection requirements ............................................................................ 187 6.1.2. Material considerations ............................................................................. 190 6.1.3. Past experience/augmented examinations ................................................. 193 6.1.4. In-service inspection methods/reliability .................................................. 197 6.1.5. Emerging in-service inspection techniques ............................................... 200 </p><p>6.2. Monitoring of low-cycle fatigue ..........................</p></li></ul>

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