BS ISO 27468:2011 BSl Standards Publication Nuclear criticality safety - Evaluation of systems containing PWR UOX fuels - Bounding burnup credit approach bsi. ..making excellence a habit. BS ISO 27468:2011 BRITISH STANDARD National foreword This British Standard is the UK implementation of IS 27468:2011. The UK participation in its preparation was entrusted to Technical Committee NCE/9, Nuclear fuel cycle technology. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. @BSI 2011 ISBN9780580652103 ICS 27.120.30 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2011. Amendments issued since publication Date Text affected BS ISO 27468:2011 ISO INTERNATIONAL STANDARD 27468 First edition 2011-07-01 Nuclear criticality safety Evaluation of systems containing PWR UOX fuels Bounding burnup credit approach Sureté-criticiteEvaluationdessystemesmettant enceuvredes combustiblesREPUOX-Approcheconservativedecredit burnup Referencenumber ISO 27468:2011(E) @ISO 2011 BS ISO 27468:2011 ISO27468:2011(E) COPYRIGHTPROTECTEDDOCUMENT ISO2011 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, ISO's member body in the country of the requester. ISO copyright office Case postale 56.CH-1211Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail [email protected] Web www.iso.org Published in Switzerland ii @ ISO 2011 All rights reserved BSISO27468:2011 ISO27468:2011(E) Contents Page Foreword .iv Introduction 1 Scope. 2 Normative references. 3 Terms and definitions. 4 Methodologyfor criticality safety evaluations considering burnup of the fuel..... 5 Implementationofcriticalitysafetyevaluationsconsideringburnupofthefuel... Annex A (informative)Validation of the depletion codes against post-irradiation examination data ......7 AnnexB (informative)Operational implementationof aburnupcreditapplication.... Bibliography...... @ ISO 2011 - All rights reserved ii BS ISO 27468:2011 ISO27468:2011(E) Foreword IsO (the International Organization for Standardization) is a worldwide federation of national standards bodies (isO member bodies). The work of preparing International Standards is normally carried out through IsO non-governmental, in liaison with IsO, also take part in the work. IsO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/lEC Directives, Part 2. adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. IsO shall not be held responsible for identifying any or all such patent rights. ISO27468 was prepared by Technical CommitteeISO/TC 85,Nuclear energy,nuclear technologies, and radiologicalprotection,SubcommitteeSC5,Nuclearfuelcycle. iv @ ISO 2011 All rights reserved BS ISO 27468:2011 ISO27468:2011(E) Introduction For many years, criticality evaluations involving irradiated uranium oxide (UOx) fuels in pressurized water after irradiation could usually have resulted in considerable criticality safety margins. The use of PWR UOX fuel with increased enrichment of 235u motivates evaluation of burnup credit in existing actual effective neutron multiplication factor, keff, of a system involving irradiated fuel is possible with methods available to nuclear criticality safety specialists. Thus, the maximum estimated keff value duri