IEC_61468-2021.pdf

IEC 61468 Edition 2.0 2021-04 INTERNATIONAL STANDARD Nuclear power plants Instrumentation systems important to safety In-core instrumentation:Characteristics and test methods of self-powered neutron detectors IEC 61468:2021-04(en)THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright 2021 IEC,Geneva,Switzerland All rights reserved.Unless otherwise specified,no part of this publication may be reproduced or utilized in any form or by any means,electronic or mechanical,including photocopying and microfilm,without permission in writing from either IEC or IECs member National Committee in the country of the requester.If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,please contact the address below or your local IEC member National Committee for further information.IEC Central Office Tel.:+41 22 919 02 11 3,rue de Varemb infoiec.ch CH-1211 Geneva 20 www.iec.ch Switzerland About the IEC The International Electrotechnical Commission(IEC)is the leading global organization that prepares and publishes International Standards for all electrical,electronic and related technologies.About IEC publications The technical content of IEC publications is kept under constant review by the IEC.Please make sure that you have the latest edition,a corrigendum or an amendment might have been published.IEC publications search-webstore.iec.ch/advsearchform The advanced search enables to find IEC publications by a variety of criteria(reference number,text,technical committee,).It also gives information on projects,replaced and withdrawn publications.IEC Just Published-webstore.iec.ch/justpublished Stay up to date on all new IEC publications.Just Published details all new publications released.Available online and once a month by email.IEC Customer Service Centre-webstore.iec.ch/csc If you wish to give us your feedback on this publication or need further assistance,please contact the Customer Service Centre:salesiec.ch.IEC online collection-oc.iec.ch Discover our powerful search engine and read freely all the publications previews.With a subscription you will always have access to up to date content tailored to your needs.Electropedia-www.electropedia.org The worlds leading online dictionary on electrotechnology,containing more than 22 000 terminological entries in English and French,with equivalent terms in 18 additional languages.Also known as the International Electrotechnical Vocabulary(IEV)online.IEC 61468 Edition 2.0 2021-04 INTERNATIONAL STANDARD Nuclear power plants Instrumentation systems important to safety In-core instrumentation:Characteristics and test methods of self-powered neutron detectors INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 27.120.20 ISBN 978-2-8322-9706-3 Registered trademark of the International Electrotechnical Commission Warning!Make sure that you obtained this publication from an authorized distributor.2 IEC 61468:2021 IEC 2021 CONTENTS FOREWORD.4 INTRODUCTION.6 1 Scope.8 2 Normative references.8 3 Terms and definitions.8 4 Abbreviated terms.12 5 Self-powered neutron detectors general advantages and disadvantages.13 6 Composition and construction.13 7 Application recommendations.16 7.1 General.16 7.2 Fluence rate mapping Core monitoring and surveillance.16 7.3 Power regulation Feedback control.16 7.4 Core protection.16 7.5 Reactor noise analysis.16 7.6 Classification.16 8 Design recommendations.17 8.1 General.17 8.2 Reproducibility of SPND characteristics.17 8.3 Background signal.17 8.4 Electrical interference noise.17 8.5 Lifetime.17 9 Test methods.17 9.1 General.17 9.2 Prototype testing.18 9.3 Production tests.18 10 Detector calibration.18 10.1 Place of calibration.18 10.2 Absolute calibration.19 10.3 Comparison calibration.19 10.4 In-core calibration.19 10.5 Calibration procedure.19 10.6 Recommended calibration periods.20 Annex A(informative)Self-powered detector principles and characteristics.21 A.1 SPND response mechanisms.21 A.2 Beta decay(delayed response).21 A.3 Neutron capture(prompt response).21 A.4 Photoelectric effect(prompt response).21 A.5 Compton effect(prompt response).21 A.6 Nature of SPND response.22 A.7 Thermal neutron interactions.22 A.8 Gamma interactions.22 A.9 Dynamic characteristics of SPND.22 A.10 Detector burn-up life.23 A.11 Measurement errors.23 A.11.1 General.23 A.11.2 Error for determination of SPND actual response.23 IEC 61468:2021 IEC 2021 3 A.11.3 Error determined by gamma-component of SPND current.24 A.11.4 Error determined by leakage currents.24 A.11.5 Error determined by signal wire current.25 A.12 Self-powered detector operating characteristics.25 A.12.1 General.25 A.12.2 Vanadium emitter characteristics.26 A.12.3 Cobalt emitter characteristics.26 A.12.4 Rhodium emitter characteristics.26 A.12.5 Silver emitter characteristics.27 A.12.6 Platinum emitter characteristics.27 A.12.7 Hafnia emitter characteristics.27 A.13 Self-powered detector assemblies.28 A.13.1 General.28 A.13.2 Typical bottom-mounted rhod