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1、Use of Periodic Safety Review for Long Term Operation of Nuclear Power PlantsSafety Reports SeriesNo.121INTERNATIONAL ATOMIC ENERGY AGENCYVIENNAA comprehensive assessment of the safety of a nuclear power plant is an important precondition for its continued operation beyond the original time frame.A

2、periodic safety review is considered an effective way to obtain an overall view of actual plant safety,and to determine the reasonable and practicable modifications that will ensure that a high level of safety is maintained during continued operation.The periodic safety review typically addresses th

3、e period until the next periodic safety review or,where appropriate,until the end of planned operation.The continued operation of a nuclear power plant beyond the time frame originally anticipated for its operation(typically 3040 years)needs to be justified by a safety assessment,with consideration

4、given to the life limiting processes and features of structures,systems and components important to safety.This publication addresses the scope of assessment,methods and applicable criteria applied within the periodic safety review and long term operation programmes framework to support decision mak

5、ing for long term operation of nuclear power plants.Safety Reports Series No.121 Use of Periodic Safety Review for Long Term Operation of Nuclear Power PlantsAtoms for PeaceAtoms for PeaceIAEA SAFETY STANDARDS AND RELATED PUBLICATIONSIAEA SAFETY STANDARDSUnder the terms of Article III of its Statute

6、,the IAEA is authorized to establish or adopt standards of safety for protection of health and minimization of danger to life and property,and to provide for the application of these standards.The publications by means of which the IAEA establishes standards are issued in the IAEA Safety Standards S

7、eries.This series covers nuclear safety,radiation safety,transport safety and waste safety.The publication categories in the series are Safety Fundamentals,Safety Requirements and Safety Guides.Information on the IAEAs safety standards programme is available on the IAEA Internet sitehttps:/www.iaea.

8、org/resources/safety-standardsThe site provides the texts in English of published and draft safety standards.The texts of safety standards issued in Arabic,Chinese,French,Russian and Spanish,the IAEA Safety Glossary and a status report for safety standards under development are also available.For fu

9、rther information,please contact the IAEA at:Vienna International Centre,PO Box 100,1400 Vienna,Austria.All users of IAEA safety standards are invited to inform the IAEA of experience in their use(e.g.as a basis for national regulations,for safety reviews and for training courses)for the purpose of

10、ensuring that they continue to meet users needs.Information may be provided via the IAEA Internet site or by post,as above,or by email to Official.Mailiaea.org.RELATED PUBLICATIONSThe IAEA provides for the application of the standards and,under the terms of Articles III and VIII.C of its Statute,mak

11、es available and fosters the exchange of information relating to peaceful nuclear activities and serves as an intermediary among its Member States for this purpose.Reports on safety in nuclear activities are issued as Safety Reports,which provide practical examples and detailed methods that can be u

12、sed in support of the safety standards.Other safety related IAEA publications are issued as Emergency Preparedness and Response publications,Radiological Assessment Reports,the International Nuclear Safety Groups INSAG Reports,Technical Reports and TECDOCs.The IAEA also issues reports on radiologica

13、l accidents,training manuals and practical manuals,and other special safety related publications.Security related publications are issued in the IAEA Nuclear Security Series.The IAEA Nuclear Energy Series comprises informational publications to encourage and assist research on,and the development an

14、d practical application of,nuclear energy for peaceful purposes.It includes reports and guides on the status of and advances in technology,and on experience,good practices and practical examples in the areas of nuclear power,the nuclear fuel cycle,radioactive waste management and decommissioning.USE

15、 OF PERIODIC SAFETY REVIEW FOR LONG TERM OPERATION OF NUCLEAR POWER PLANTSAFGHANISTANALBANIAALGERIAANGOLAANTIGUA AND BARBUDAARGENTINAARMENIAAUSTRALIAAUSTRIAAZERBAIJANBAHAMASBAHRAINBANGLADESHBARBADOSBELARUSBELGIUMBELIZEBENINBOLIVIA,PLURINATIONAL STATE OFBOSNIA AND HERZEGOVINABOTSWANABRAZILBRUNEI DARU

16、SSALAMBULGARIABURKINA FASOBURUNDICABO VERDECAMBODIACAMEROONCANADACENTRAL AFRICAN REPUBLICCHADCHILECHINACOLOMBIACOMOROSCONGOCOSTA RICACTE DIVOIRECROATIACUBACYPRUSCZECH REPUBLICDEMOCRATIC REPUBLIC OF THE CONGODENMARKDJIBOUTIDOMINICADOMINICAN REPUBLICECUADOREGYPTEL SALVADORERITREAESTONIAESWATINIETHIOPI

17、AFIJIFINLANDFRANCEGABONGAMBIAGEORGIAGERMANYGHANAGREECEGRENADAGUATEMALAGUYANAHAITIHOLY SEEHONDURASHUNGARYICELANDINDIAINDONESIAIRAN,ISLAMIC REPUBLIC OF IRAQIRELANDISRAELITALYJAMAICAJAPANJORDANKAZAKHSTANKENYAKOREA,REPUBLIC OFKUWAITKYRGYZSTANLAO PEOPLES DEMOCRATICREPUBLICLATVIALEBANONLESOTHOLIBERIALIBYA

18、LIECHTENSTEINLITHUANIALUXEMBOURGMADAGASCARMALAWIMALAYSIAMALIMALTAMARSHALL ISLANDSMAURITANIAMAURITIUSMEXICOMONACOMONGOLIAMONTENEGROMOROCCOMOZAMBIQUEMYANMARNAMIBIANEPALNETHERLANDSNEW ZEALANDNICARAGUANIGERNIGERIANORTH MACEDONIANORWAYOMANPAKISTANPALAUPANAMAPAPUA NEW GUINEAPARAGUAYPERUPHILIPPINESPOLANDPO

19、RTUGALQATARREPUBLIC OF MOLDOVAROMANIARUSSIAN FEDERATIONRWANDASAINT KITTS AND NEVISSAINT LUCIASAINT VINCENT AND THE GRENADINESSAMOASAN MARINOSAUDI ARABIASENEGALSERBIASEYCHELLESSIERRA LEONESINGAPORESLOVAKIASLOVENIASOUTH AFRICASPAINSRI LANKASUDANSWEDENSWITZERLANDSYRIAN ARAB REPUBLICTAJIKISTANTHAILANDTO

20、GOTONGATRINIDAD AND TOBAGOTUNISIATRK?YETURKMENISTANUGANDAUKRAINEUNITED ARAB EMIRATESUNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELANDUNITED REPUBLIC OF TANZANIAUNITED STATES OF AMERICAURUGUAYUZBEKISTANVANUATUVENEZUELA,BOLIVARIAN REPUBLIC OF VIET NAMYEMENZAMBIAZIMBABWEThe following States are Memb

21、ers of the International Atomic Energy Agency:The Agencys 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 object

22、ive is“to accelerate and enlarge the contribution of atomic energy to peace,health and prosperity throughout the world.Safety Reports Series No.121USE OF PERIODIC SAFETY REVIEW FOR LONG TERM OPERATION OF NUCLEAR POWER PLANTSINTERNATIONAL ATOMIC ENERGY AGENCY VIENNA,2023 IAEA,2023Printed by the IAEA

23、in AustriaOctober 2023STI/PUB/2010COPYRIGHT NOTICEAll 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 Organizati

24、on(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 welco

25、med and considered on a case-by-case basis.Enquiries should be addressed to the IAEA Publishing Section at:Marketing and Sales Unit,Publishing SectionInternational Atomic Energy AgencyVienna International CentrePO Box 1001400 Vienna,Austriafax:+43 1 26007 22529tel.:+43 1 2600 22417email:sales.public

26、ationsiaea.org www.iaea.org/publicationsIAEA Library Cataloguing in Publication DataNames:International Atomic Energy Agency.Title:Use of periodic safety review for long term operation of nuclear power plants/International Atomic Energy Agency.Description:Vienna:International Atomic Energy Agency,20

27、23.|Series:IAEA safety reports series,ISSN 10206450;no.121|Includes bibliographical references.Identifiers:IAEAL 23-01608|ISBN 9789201178237(paperback:alk.paper)|ISBN 9789201179234(pdf)|ISBN 9789201180230(epub)Subjects:LCSH:Nuclear power plants Safety measures.|Nuclear power plants Maintainability.|

28、Nuclear power plants Management.Classification:UDC 621.039.58|STI/PUB/2010FOREWORDA comprehensive assessment of the safety of a nuclear power plant is an important precondition for continuing its operation beyond the originally anticipated time frame.Most Member States consider periodic safety revie

29、w to be an effective way to obtain an overall view of actual plant safety and determine reasonable and practicable modifications to be made in order to ensure that a high level of safety is maintained during continued operation.The complex process of conducting a periodic safety review can be aided

30、by appropriately subdividing the tasks into several safety factors.These safety factors are selected based on international experience and are intended to cover all aspects important to the safety of an operating nuclear power plant.In cases where the number of safety factors used and/or their group

31、ing is different because of the specific needs of the operating organization or regulatory body,or owing to particular aspects of the nuclear power plant under review,the comprehensiveness of the periodic safety review can be ensured by other means.A periodic safety review typically addresses the pe

32、riod until the next periodic safety review or,where appropriate,until the end of planned operation,and considers whether there are any foreseeable circumstances that could endanger the operation of the nuclear power plant in the interim.Continuation of operation of a nuclear power plant beyond the o

33、riginally anticipated time frame(typically 3040 years)has become a priority for many operating organizations.Long term operation needs to be justified by safety assessment,with consideration given to the life limiting processes and features of structures,systems and components.As the typical interva

34、l between periodic safety reviews is ten years,this means that the third or fourth periodic safety review will possibly evaluate the safety factors related to long term operation,namely design;actual status of structures,systems and components;equipment qualification and ageing.This publication is i

35、ntended to provide a common basis and criteria for using periodic safety reviews in support of justification of long term operation or licence renewal,as well as to discuss current challenges,synergies,good practices and examples of corrective actions and safety improvements related to the applicati

36、on of periodic safety reviews for justifying long term operation of nuclear power plants.The IAEA officers responsible for this publication were A.Duchac,R.Krivanek and G.Petofi of the Division of Nuclear Installation Safety.EDITORIAL NOTEAlthough great care has been taken to maintain the accuracy o

37、f information contained in this publication,neither the IAEA nor its Member States assume any responsibility for consequences which may arise from its use.This publication does not address questions of responsibility,legal or otherwise,for acts or omissions on the part of any person.Guidance and rec

38、ommendations provided here in relation to identified good practices represent expert opinion but are not made on the basis of a consensus of all Member States.The use of particular designations of countries or territories does not imply any judgement by the publisher,the IAEA,as to the legal status

39、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

40、 endorsement or recommendation on the part of the IAEA.The IAEA has no responsibility for the persistence or accuracy of URLs for external or third party Internet web sites referred to in this book and does not guarantee that any content on such web sites is,or will remain,accurate or appropriate.CO

41、NTENTS1.INTRODUCTION.11.1.Background.11.2.Objective.21.3.Scope.21.4.Structure.32.STRATEGY AND METHODOLOGY FOR PERIODIC SAFETY REVIEW IN SUPPORT OF LONG TERM OPERATION JUSTIFICATION.42.1.Scope and content of periodic safety review for justification of long term operation.42.2.Periodic safety review b

42、asis document.142.3.Methodology and acceptance criteria.163.COORDINATION OF PERIODIC SAFETY REVIEW AND LONG TERM OPERATION ACTIVITIES.213.1.Areas in which the long term operation programme could provide inputs to periodic safety review.213.2.Key outputs from periodic safety review for justification

43、of long term operation.434.GLOBAL ASSESSMENT.574.1.Purpose of global assessment.574.2.Deviations and their safety significance.584.3.Analysis of interfaces,gaps and overlaps.594.4.Analysis of the combined effects of findings.604.5.Assessment of defence in depth.604.6.Determination of reasonably prac

44、ticable safety improvements 624.7.Development of an integrated implementation plan.644.8.Assessment of the overall level of plant safety.665.IMPLEMENTATION OF PROGRAMMES,COMMITMENTS AND IMPROVEMENTS.675.1.Introduction.675.2.Processes for implementation of long term operation and periodic safety revi

45、ew.685.3.Mapping of similar long term operation areas to the safety factors in the periodic safety review.705.4.Implementation of the programmes for long term operation and periodic safety review.745.5.Recommended tools for implementation of the programmes for periodic safety review and long term op

46、eration.776.ROLES AND RESPONSIBILITIES IN PREPARATION FOR SAFE LONG TERM OPERATION WHEN INTEGRATED WITH PERIODIC SAFETY REVIEW.816.1.General.816.2.Roles and responsibilities of involved parties.816.3.Communication between the operating organization and the regulatory body.846.4.Coordination of submi

47、ssions for long term operation.846.5.Government and public information.856.6.Regulatory expectations for PSR and long term operation.857.DOCUMENTATION IN SUPPORT OF JUSTIFICATION OF LONG TERM OPERATION.86REFERENCES.89ANNEX I:MEMBER STATES EXPERIENCES AND PRACTICES 91ANNEX II:EXAMPLE OF A GLOBAL ASSE

48、SSMENT 105ABBREVIATIONS.115CONTRIBUTORS TO DRAFTING AND REVIEW.1171.INTRODUCTION1.1.BACKGROUNDOperational nuclear power plants(NPPs)are generally subject to routine reviews of plant operational safety and ad hoc safety reviews in response to operational events.In many Member States,these safety revi

49、ews have specific areas of focus and do not typically consider all factors relevant to long term operation(LTO),such as changes in codes,standards and regulations;the cumulative effects of plant ageing;plant modifications;feedback of operating experience;and developments in science and technology.To

50、 capture the aggregate effect of these factors on plant safety,many Member States periodically conduct a comprehensive,integrated safety review,commonly referred to as a periodic safety review(PSR).This type of review relies on a systematic and comprehensive process whereby up to date codes,standard

51、s and regulations are considered to provide assurance of the continued viability of the plants licensing basis,given the cumulative impacts of emerging national and international standards,evolving regulatory requirements,plant ageing,operating experience and technological developments.PSR provides

52、an effective way to obtain an overall view of actual plant safety and the quality of the safety documentation and to determine reasonable and practical modifications to ensure or improve safety.The main goal of the PSR is to drive the continuous safety improvement of the plant.As the usual interval

53、between PSRs is ten years,this means that the third or fourth PSR is typically used to evaluate the safety factors related to operation beyond the originally planned or licensed lifetime,usually referred to as long term operation.Relevant safety factors include(among others)plant design safety;actua

54、l condition of structures,systems and components(SSCs)important to safety;equipment qualification and ageing.The term safety factor,introduced in IAEA Safety Standards Series No.SSG-25,Periodic Safety Review for Nuclear Power Plants 1,refers to those aspects of the safety of an operating NPP that ar

55、e considered important and are not expected to change over the course of LTO.As the LTO assessment and the PSR programme often do not run in parallel,several inputs from LTO to PSR,such as corrective actions and the LTO action plan,are to be fully incorporated into the subsequent PSR.In February 202

56、0,the IAEA organized a Technical Meeting on Use of Periodic Safety Review in Support of Long Term Operation Safety Assessment.The meeting provided a forum for discussion of current challenges,synergies,good practices and examples of corrective actions and safety improvements related to the applicati

57、on of PSR for justifying LTO for NPPs.The final round table 1discussion underlined the IAEAs recommendations on the implementation of PSR(reflected in SSG-25 1)and LTO(reflected in IAEA Safety Standards Series No.SSG-48,Ageing Management and Development of a Programme for Long Term Operation of Nucl

58、ear Power Plants 2),which are broadly used by Member States.Because the scope and use of PSR in support of the justification of LTO varies among Member States,the operating organizations and regulatory bodies sought IAEA assistance in clarifying the use of PSR to support decision making for the long

59、 term.Furthermore,guidance was sought to improve Member States understanding of the IAEA Safety Standards on PSR and LTO,as well as their adequate implementation.1.2.OBJECTIVEThe objectives of this publication are:(a)To provide a common basis and criteria for using PSR results in support of justific

60、ation of LTO;(b)To provide information regarding use of results from LTO activities in PSR;(c)To describe current challenges,synergies and examples of Member States practices related to the application of PSR to support the LTO of NPPs;(d)To define good practices for LTO and PSR programmes at NPPs;(

61、e)To improve understanding of the IAEA Safety Standards on PSR,ageing management and LTO.This publication is intended for operating organizations,regulatory bodies and their technical support organizations,consultants and advisory bodies.Guidance and recommendations provided here in relation to iden

62、tified good practices represent expert opinion but are not made on the basis of a consensus of all Member States.1.3.SCOPEThis publication addresses the scope of the LTO assessment,methods and applicable criteria to support decision making within the PSR and LTO programmes framework.It is intended t

63、o verify whether:(a)The plant adequately conforms to modern standards and practices;(b)The(updated)licensing basis will be valid throughout the plants intended period of operation;2(c)The arrangements that are in place ensure the maintenance of safe plant operation during LTO;(d)The improvements to

64、be implemented address any safety issues that have been identified.This publication describes in detail:(a)Augmentation and amendment of a PSR strategy and methodology when the PSR will be used in support of LTO;(b)Coordination and synergies of PSR and LTO activities;(c)The function of the PSR globa

65、l assessment in the justification of LTO;(d)Roles and responsibilities in preparation for safe LTO.The assessment methods described in this publication are not meant to replace other evaluations required by national regulations and national or international standards.Rather,they are intended to prov

66、ide additional tools for improved coordination and guidance regarding finding potential synergies among the programmes for LTO and PSR.Due to the nature of the subjects being considered,this publication applies to NPPs.This publication may have a wider applicability,for example,to radioactive waste

67、management facilities,spent fuel storage or handling facilities located on the reactor site.The approaches described in this publication can be adapted,with judgement,to other nuclear installations(e.g.small modular reactors,research reactors).This publication references several IAEA Safety Standard

68、s and Safety Report Series that are needed for cross-referencing purposes while reading this publication.It is strongly recommended that the reader be familiar with Refs 1 and 2 before reading this publication.1.4.STRUCTUREThis publication consists of seven sections.In addition,there are two annexes

69、 illustrating practices in Member States.Following the introduction,Section 2 discusses the PSR strategy and methodology in support of justification of LTO.Section 3 is from the perspective of both an LTO programme and a PSR programme.Section 4 describes the method of global assessment.Section 5 des

70、cribes the implementation of programmes,commitments and improvements for LTO.Section 6 describes the roles and responsibilities involved in preparation for safe LTO.Section 7 provides a description of the documentation needed in support of justification of 3LTO.Annex I provides Member States experie

71、nces and practices.Finally,Annex II provides an example of the steps to be taken in a global assessment.2.STRATEGY AND METHODOLOGY FOR PERIODIC SAFETY REVIEW IN SUPPORT OF LONG TERM OPERATION JUSTIFICATION2.1.SCOPE AND CONTENT OF PERIODIC SAFETY REVIEW FOR JUSTIFICATION OF LONG TERM OPERATIONThe obj

72、ective of PSR,as specified in SSG-25 1,is to determine by means of a comprehensive assessment:(a)The adequacy and effectiveness of the arrangements and the SSCs(equipment)that are in place to ensure plant safety for:The next planned PSR;The end of planned operation(if the NPP will cease operation be

73、fore the next regular PSR);The end of LTO(if the PSR is planned to be used in support of justification of LTO).(b)The extent to which the plant conforms to current national and/or international safety standards and operating practices.(c)Necessary safety improvements and timescales for the implement

74、ation.(d)The extent to which the safety documentation,including the licensing basis,remains valid.In general,the PSR outputs could be used in support of justification of LTO in the following ways:(a)To obtain an overall assessment of actual plant safety;(b)To confirm that sufficient safety margins o

75、f SSCs exist for the next operational period;(c)To verify the effectiveness of the operating and maintenance programmes for LTO;(d)To identify any safety concern(s)that require corrective actions;(e)To determine reasonable safety improvements to enhance plant safety and reliability;(f)To establish a

76、 corrective action plan.4PSR also evaluates the plant organization,processes,programmes and management systems in order to confirm that they are adequate to support the safe operation of the facility.When PSR is used as an input to decision making for LTO,the documentation needs to clearly define th

77、e scope of the assessments related to LTO that are carried out in the PSR.The differences between a standard PSR and a PSR for LTO are as follows:(a)The PSR scope is extended in accordance with Requirement 16 of IAEA Safety Standards Series No.SSR-2/2(Rev.1),Safety of Nuclear Power Plants:Commission

78、ing and Operation 3.This extended PSR requires:A review of the preconditions for LTO,which covers programmes and documents relevant for ageing management;A review of ageing management and its alignment with SSG-48 2,especially with regard to scope setting,including special attention to SSCs that are

79、 to be included in the scope,in accordance with para.5.16(b)1 of SSG-48 2.(b)LTO is an extended operation necessitating a feasibility study and a subsequent analysis in terms of financial return,as justification.The results of the assessment of a PSR for LTO of an NPP need to confirm the assumptions

80、 of the feasibility study for LTO.(c)A PSR in support of LTO is a part of the programme for LTO.The volume of physical modifications is typically higher because of objectives related to design improvements,preserving and extending equipment qualification,and addressing technological obsolescence iss

81、ues.(d)Intending to use PSR in support of LTO may have a crucial impact on its scheduling,especially if an environmental impact assessment is also required for LTO and if the overall closure of the PSR is needed just before or after entering the period of LTO.(e)LTO of more than ten years needs to b

82、e justified in such a way that the evaluations in the PSR are extended from ten years to the period of LTO.(f)A review of long term resource planning,preserving competences and knowledge for the entire period of LTO,is included and takes into account 1“Other SSCs whose failure may prevent SSCs impor

83、tant to safety from fulfilling their intended functions.Examples of such potential failures are:Missile impact from rotating machines;Failures of lifting equipment;Flooding;High energy line break;Leakage of liquids(e.g.from piping or other pressure boundary components).”5the increasing retirement of

84、 experienced personnel and possible challenges in recruiting suitably qualified and experienced replacements.Paragraph 2.10 of SSG-25 1 states that a PSR can be used“as a systematic safety assessment carried out at regular intervals”and“in support of the decision making process for long term operati

85、on”.SSG-25 1 is not specifically intended to provide recommendations for the activities performed during LTO of an NPP.However,the scope of the review of the safety factors can be adapted to facilitate an assessment of the feasibility of LTO.According to Section 3 of SSG-25 1,PSR is considered an ef

86、fective way to obtain an overall view of actual plant safety and to determine reasonable and practicable modifications to be made in order to ensure that a high level of safety is maintained during LTO.The safety improvements identified in the PSR are used as inputs into the decision as to whether t

87、o approve LTO(see para.3.10 of SSG-25 1).PSR and LTO programmes need to identify life limiting features of the NPP in order to determine if there is a need to modify,refurbish or replace certain SSCs for the purpose of extending its operating lifetime.Therefore,the scope of the safety factors needs

88、to be adapted to determine the feasibility of LTO.For example,the scope of the safety factor relating to ageing may be expanded to include an evaluation of the safety analyses with time limited assumptions and assessments of ageing effects.In the review,increased importance is given to ageing effect

89、s,degradation mechanisms and ageing management programmes(AMPs)2.If a combined PSR can be performed for several units at a site,then the results of the PSR could also be used to support an LTO programme covering several units.2.1.1.Time frame of PSR for LTONormally,a PSR covers ten years of operatio

90、n of an NPP.However,if a PSR is used to justify LTO,the time span considered in the review of the safety factors covers the entire intended period of LTO(see para.3.7 of SSG-25 1).This is typically 20 years,but the time span could be different,depending on national regulations and the plants intenti

91、ons.As specified in para.7.38 of SSG-48 2,the timespan for reviewing safety factors 2 to 5,which relate to the actual condition of SSCs,equipment qualification,ageing and deterministic safety analysis(DSA),respectively,could be adapted to cover the period of LTO if the PSR is used to support LTO.The

92、 operating organization continues to carry out PSR every ten years during the period of LTO(see para.3.7 of SSG-25 1).If an LTO orientated PSR is completed several years(e.g.23 years)prior to the start of the intended period of LTO,some results might no longer be valid.6Additional analyses may be re

93、quired to confirm the validity of the evaluation results for the justification for LTO.Part of this could be due to obsolescence:a possible solution is to carry out gap analyses within the organization to identify the gaps to be filled.2.1.2.Scope setting of SSCsSSG-25 1 sets the scope of SSCs for c

94、onducting PSR at a high level as“SSCs important to safety”and“any non-safety-classified SSCs”whose failure might inhibit or adversely affect a safety function.Paragraph 5.16 of SSG-48 2 is more specific regarding the selection of in-scope SSCs and identifies three categories of SSCs for inclusion in

95、 the scope of ageing management,as follows:(a)SSCs important to safety that are necessary to fulfil the fundamental safety functions;(b)Other SSCs whose failure may prevent SSCs important to safety from fulfilling their intended safety functions;(c)Other SSCs that are credited in the safety analyses

96、(deterministic and probabilistic)as performing the function of coping with certain types of events,consistent with national regulatory requirements.Table 1 outlines the correlation between the SSCs identified for evaluating safety factors 14 in PSR at the high level(i.e.SSCs important to safety and

97、non-safety-classified SSCs whose failure might inhibit or adversely affect safety functions)and the SSCs selected using criteria(a),(b)and(c)above(defined in more detail in SSG-48 2,para.5.16)for ageing management review(AMR).The process of selecting SSCs using the three criteria defined in SSG-48 2

98、,para.5.16,for AMR is based on SSCs safety functions or their intended functions,whereas the process of SSC selection for PSR described in SSG-25 1 is based on a high level safety classification(i.e.items important to safety and certain items not important to safety).The three criteria defined in SS

99、G-48 2 provide a more comprehensive and clearer basis for the selection of SSCs than that given in SSG-25 1.A comprehensive,well documented and up to date safety case,including safety analysis,is required to adequately complete the scope setting process for LTO.The safety case can also be used to su

100、pport the PSR of safety factors 1,5,6 and 7 relating to plant design and safety analysis.A clear distinction between those SSCs considered to be within the scope and those out of the scope needs to be defined and documented by the licensee at a structure or component level,including a clear statemen

101、t about the boundary between the two items,where appropriate.7Typically,the list of SSCs important to safety only considers permanent or anchored equipment.Following the nuclear accident at the Fukushima Daiichi nuclear power station,most NPPs have non-permanent(mobile)equipment to be used for accid

102、ent mitigation,which may be outside the scope of safety classification.It is necessary to specify how non-permanent equipment,as well as radiation protection related equipment,emergency planning equipment and associated emergency response facilities,will either be included in the scope of 8TABLE 1.C

103、ORRELATION OF THE CRITERIA FOR SCOPE SETTING OF SSCs PROVIDED IN SSG-25 1 AND SSG-48 2In-scope SSCs for safety factors 14 of PSR(SSG-25 1)DefinitionIn-scope SSCs for LTO(applicable selection criteria(a),(b)and(c)as defined in para.5.16 of SSG-48 2)Safety systemsA system important to safety,provided

104、to ensure the safe shutdown of the reactor or the residual heat removal from the reactor core,or to limit the consequences of anticipated operational occurrences and design basis accidents 4Selection criterion(a)applies directly and includes SSCs delivering the three fundamental safety functions(con

105、trol of reactivity,cooling and confinement of fissile material)Safety related itemsAn item important to safety that is not part of a safety system 4Selection criterion(b)applies and includes SSCs whose failure may prevent SSCs important to safety from fulfilling their intended functions.Criterion(b)

106、may include items not important to safety,according to para.5.51 of SSG-25 1Items not important to safetyAny non-safety classified SSCs whose failure might inhibit or adversely affect safety functions(para.5.51 of SSG-25 1)Several items not important to safety may be included in the scope for LTO ba

107、sed on the selection criteria(b)and(c)Safety features for design extension conditionsItem that is designed to perform a safety function for,or that has a safety function for,design extension conditions 4Selection criterion(c)applies and includes SSCs needed to cope with design extension conditions o

108、r to mitigate the consequences of severe accidentsan LTO programme or be on a separate,dedicated equipment list to be evaluated in terms of the respective safety factors in the PSR.Consideration of safety significant SSCs identified by the probabilistic safety assessment(PSA)can also be incorporated

109、 into the scope setting process of LTO.This might involve identifying SSCs for normal operation,with no original safety function identified in the design,but credited in accidents or severe accident procedures.PSA could be used to determine component risk importance measures to provide a grading met

110、hodology for the in-scope equipment.Further information on the scope setting process for LTO can be found in Safety Reports Series No.106,Ageing Management and Long Term Operation of Nuclear Power Plants:Data Management,Scope Setting,Plant Programmes and Documentation 5.2.1.3.Scope of the most relev

111、ant safety factors for justification of LTOThe scope of the safety factors related to ageing needs to be expanded to include an evaluation of the time limited assumptions and assessments of ageing effects.In the review,increased importance is placed on ageing effects,degradation mechanisms,AMPs and

112、obsolescence(see para.4.6 of SSG-48 2).Areas being evaluated in a PSR that provides justification for LTO are typically the same as in a normal PSR.The term safety factor,introduced in SSG-25 1,refers to those aspects of safety of an operating NPP that are considered important and are not expected t

113、o be different during the period of LTO.However,some of these important aspects of safety may gradually be challenged over time or extended operation because of physical degradation,ineffective knowledge and competence transfer to new plant personnel,evolution of technology or new developments in re

114、quirements,codes and standards.These aspects and their associated risks need to be effectively managed to ensure safe LTO.Within this document,the term relevant is used for those PSR safety factors that relate to the analysis of these aspects of safety.A PSR that is used to support justification for

115、 LTO requires a more detailed analysis of the relevant safety factors,as they provide a demonstration of how the related risks are managed to ensure safe LTO.Table 2 shows the most relevant safety factors required to support justification of LTO.The results of an in depth assessment of these safety

116、factors provide important inputs for justification of LTO.The scope of SSCs is expanded to meet criteria according to SSG-48 2,paras 5.16 and 5.17.910TABLE 2.THE MOST RELEVANT SAFETY FACTORS FOR JUSTIFICATION OF LONG TERM OPERATION(according to SSG48 2)Safety factorNamePurpose of the reviewSF1Plant

117、designThe review of this safety factor is crucial to the identification of additional safety improvements necessary to ensure that the licensing basis remains valid during the period of LTO.Such improvements might include refurbishment,the provision of additional SSCs,safety features and/or addition

118、al safety analysis and engineering justifications.SF2Actual condition of SSCsThe review of this safety factor determines the actual condition of in-scope SSCs and assesses whether they are adequate and capable of meeting design requirements at the end of LTO.SF3Equipment qualificationThe review of t

119、his safety factor aims at determining whether plant equipment subject to qualification has been properly identified and qualified(including for environmental conditions)and whether equipment qualification status is preserved through an equipment qualification programme,maintenance,inspection and tes

120、ting that provides confidence in the delivery of safety functions until at least the next PSR.The environmental qualification has been identified as a time limited ageing analysis(TLAA).TLAAs are re-evaluated for the planned period of LTO.The revalidation is to demonstrate that the equipment will ma

121、intain an adequate safety margin until the end of LTO.SF4AgeingThe review of this safety factor determines whether the ageing aspects affecting in-scope SSCs are effectively managed and whether an effective AMP is in place so that all required safety functions will be delivered until the end of LTO.

122、The review of this safety factor identifies any plant programme enhancements needed to ensure that the structures or components will be able to perform their intended functions during LTO.The review of this safety factor also assesses whether the plant obsolescence management programme will remain e

123、ffective for the period of LTO.TLAAs can be revalidated within this safety factor for the planned period of LTO.The revalidation demonstrates that the equipment will maintain its safety margin at the end of LTO.2.1.4.Scope of other safety factors considered for justification of LTOAdditional areas w

124、ithin other PSR safety factors that can support justification of LTO are the capacity for long term storage of spent fuel and radiation waste,environmental monitoring and authorized discharges,plant safety performance and review of non-ageing related processes,such as the processes for corrective ac

125、tions and operating experience.There are several other safety factors whose areas of focus are also essential for justification of LTO.These safety factors,shown in Table 3,are typically used in synergy with the PSR.Where used to support LTO,they are to be thoroughly reviewed.The results of in depth

126、 assessment of these safety factors provide supplementary information needed for the justification of LTO.TABLE 3.EXAMPLES OF THE USE OF OTHER SAFETY FACTORS TO SUPPORT JUSTIFICATION OF LONG TERM OPERATIONSafety factorNamePurpose of the review for LTOSF5Deterministic safety analysisThe review of thi

127、s safety factor determines to what extent the existing DSA is complete and remains valid,taking into account the actual plant design,the actual condition of SSCs important to safety and their predicted state at the end of LTO,and the existence and adequacy of safety margins.An updated safety analysi

128、s report reflects the configuration of the plant that will operate during LTO.These updates include design changes such as replacements and upgrades of plant systems,new analyses and calculations using ageing related data,revalidation of TLAAs and other time limited assumptions(e.g.update of pressur

129、ized thermal shock analysis).SF6Probabilistic safety assessmentThe review of this safety factor determines the extent to which the existing PSA study remains valid as a representative model of the NPP,whether it reflects the latest plant configuration and identifies weaknesses in the design and oper

130、ation of the plant and whether it evaluates and compares proposed safety improvements in the global assessment.An adequate and up to date PSA model is an important precondition for appropriate selection of SSCs for the LTO scope setting.11TABLE 3.EXAMPLES OF THE USE OF OTHER SAFETY FACTORS TO SUPPOR

131、T JUSTIFICATION OF LONG TERM OPERATION(cont.)Safety factorNamePurpose of the review for LTOSF7Hazard analysisThe review of this safety factor demonstrates the adequacy of protection against internal and external hazards,with account taken of the plant design,site characteristics,actual condition of

132、the in-scope SSCs important to safety and their predicted state at the end of the LTO period.A comprehensive site reassessment could be required for justification of LTO.SF8Safety performanceThe review of this safety factor determines whether the plants safety performance indicators and records of o

133、perating experience,including the evaluation of root causes of plant events,are effective or indicate any need for safety improvements,and whether extrapolation of safety performance trends has been considered for the whole LTO period.SF9Use of experience from other plants and research findingsThe r

134、eview of this safety factor determines whether there is adequate feedback of relevant experience from other NPPs and research from the findings,and whether this is used to introduce reasonable and practicable safety improvements at the plant or operating organization.Consideration of the latest inte

135、rnational experience and research findings related to LTO could be a special focus for the review of this safety factor when the PSR is used to support LTO.SF10Organization,management system and safety cultureThe review of this safety factor determines whether the organization,the management system

136、and the safety culture are adequate and effective to ensure the safe operation of the NPP.This safety factor is an important precondition for safe LTO.The review determines whether an adequate policy regarding LTO is present and whether the effectiveness of dedicated organizational structures and su

137、fficient resources will be warranted for the duration of LTO.12TABLE 3.EXAMPLES OF THE USE OF OTHER SAFETY FACTORS TO SUPPORT JUSTIFICATION OF LONG TERM OPERATION(cont.)Safety factorNamePurpose of the review for LTOSF11ProceduresThe review of this safety factor determines whether the operating organ

138、izations processes for managing,implementing and adhering to operating and working procedures,as well as for maintaining compliance with operational limits,conditions and regulatory requirements,are adequate and effective and ensure plant safety for the period of LTO.SF12Human factorsThe review of t

139、his safety factor evaluates the various human factors that may affect the safe operation of the NPP and seeks improvements that are reasonable and practicable for the whole period of LTO.Issues related to the availability of sufficiently qualified staff,including the effective knowledge and competen

140、ce management necessary for the LTO period,are included in the review of this safety factor.SF13Emergency planningThe review of this safety factor determines whether the operating organization has in place adequate plans,staff,facilities and equipment for dealing with emergencies;and whether the ope

141、rating organizations arrangements have been adequately coordinated with the arrangements of local and national authorities and are regularly exercised.Due consideration of changes at the plant site,its surroundings and the status of equipment and facilities used for emergency preparedness are provid

142、ed by the review of this safety factor to confirm their pertaining adequacy during LTO.SF14Radiological impact on the environmentThe review of this safety factor determines if the operating organization has an adequate and effective programme for monitoring the radiological impact of the plant on th

143、e environment,which ensures that emissions are properly controlled and are as low as reasonably achievable.This review includes the impact on the environment of the activities carried out during the LTO period of the plant(e.g.refurbishment,replacement,new waste storage).132.2.PERIODIC SAFETY REVIEW

144、 BASIS DOCUMENTThe PSR basis document defined in para.4.6 of SSG-25 1 is a key document in the PSR.It defines the scope of the review and how it will be conducted.It serves as the agreement between the utility and the regulator regarding the PSRs scope and methodology.The intent of SSG-25 1 is not s

145、pecifically to provide recommendations for the activities performed during LTO of an NPP.However,the scope of the review of the safety factors,which is specified in the PSR basis document,can be adapted to support an assessment of the feasibility of LTO,as indicated in para.2.10 of SSG-25 1.2.2.1.De

146、velopment of the PSR basis documentThe PSR basis document describes how the review of safety factors is conducted to meet the key objectives of the PSR.The PSR basis document is developed taking into account how it fits into the overall LTO safety justification.When defining the scope of the PSR,it

147、is important to consider the stage of the justification of LTO at which the PSR is being conducted.The responsibility for developing the PSR basis document rests with the licensee,in accordance with the requirements and guidance issued by the regulatory body(see Section 5 for details on roles and re

148、sponsibilities).The quality and completeness of the PSR basis document significantly affect the efficiency of performing a PSR,the quality of the results and eventually the success of the PSR in meeting its objectives.An independent review of the PSR basis document may be required to ensure the expe

149、cted results are obtained,especially in the case of a first PSR or a major update of a previously used PSR basis document.This major update could include changes incorporated into the PSR basis document in support of justification of LTO.Independent review by the IAEA or other recognized internation

150、al organizations could be considered.In order to facilitate the production of the PSR basis document and obtain the regulatory bodys concurrence,it is pragmatic to have different cut-off dates:one for the codes and standards against which the review will be conducted and another,later one for the NP

151、P status.This will facilitate the identification of,and agreement on,applicable requirements and documents that will define the scope of the review.Appropriate cut-off dates are determined in accordance with the adopted strategy and time schedules for PSR and LTO,included in the PSR basis document a

152、nd agreed with the regulatory body.When establishing the project schedule for the PSR,it is important to consider the regulatory requirements regarding the submission date for both the PSR and the justification of LTO.This is to ensure a suitable time frame to 14support justification of LTO,as well

153、as adequate time necessary for the resolution of any deviation identified in the PSR that could hamper LTO.2.2.2.Content and structure of the PSR basis documentAppendix II of SSG-25 1 provides the recommended content of the PSR basis document.The proposed content and the structure of this PSR basis

154、document example are also suitable for a PSR that will be used to support LTO.If the PSR is performed concurrently with the preparation for LTO,the PSR basis document typically includes a description of interactions between the PSR and LTO projects.This could include the communication strategy and i

155、nterface meetings between the two teams to take advantage of any potential synergies,as well as meetings with the regulatory body involving both teams.A global assessment is a part of the PSR basis document(see section 6 of SSG-25 1).This assessment provides the methodology for processing the result

156、s of the safety factor review with the objective of defining an integrated implementation plan and providing justification for LTO.The procedures of the global assessment are generally robust and generic in order to successfully accommodate the LTO assessment and its results,but the assessment perio

157、d is to be extended to the period of LTO.Based on the expected schedules of the PSR and LTO projects and their anticipated synergies,the global assessment could be reviewed and updated as necessary(see Section 4).2.2.3.Regulations,codes and standards considered in the PSRThe PSR basis document conta

158、ins a list of applicable regulations,codes and standards,as well as clear criteria for selecting those that will be used in the PSR.The list could be updated to reflect the date of the review.It typically includes:(a)National laws and regulations;(b)Operation licence and other relevant licences;(c)I

159、AEA Safety Standards;(d)Codes and standards issued by the State of the vendor of the technology;(e)The latest revisions of these codes and standards.Other requirements,such as international safety standards and operating practices,as well as national or international guides,are to be met as much as

160、practicable.The selection and hierarchy of safety standards and operating practices considered are clearly stated in the PSR basis document,with special consideration given to safety standards issued by the State of the vendor of the technology.15Reference can also be made to international codes and

161、 standards(such as those of the IAEA,the International Organization for Standardization(ISO)or the International Electrotechnical Commission(IEC)or,where appropriate,to the codes and standards of a recognized organization of a particular State(for example,the American Society of Mechanical Engineers

162、(ASME),the Nuclear Safety Standards Commission(Kerntechnischer Ausschuss)or the Institute of Electrical and Electronics Engineers(IEEE).The practices of international organizations,such as good practices collected by the World Association of Nuclear Operators(WANO)and the IAEA,as well as the informa

163、tion generated by owners groups,could also be relevant and taken into account.2.3.METHODOLOGY AND ACCEPTANCE CRITERIA2.3.1.IntroductionThis section describes the methodology and criteria entailed in a review of safety factors in PSR,focusing on the most relevant ones for justification of LTO.Suggest

164、ed adjustments to the scope and content are proposed and discussed where the PSR is intended to support an LTO assessment.The main safety aspects to be evaluated in a PSR are typically grouped into five categories,which pertain to the plant(safety factors 14),safety analyses(safety factors 57),safet

165、y performance and feedback from operating experience(safety factors 89),management(safety factors 1013)and the environment(safety factor 14).The safety factors most related to LTO are safety factor 1(plant design),safety factor 2(actual condition of SSCs),safety factor 3(equipment qualification)and

166、safety factor 4(ageing)(see Table 2).Other safety factors,as shown in Table 3,are also relevant for LTO.2.3.2.Review of safety factorsGeneral review recommendations for the PSR safety factors are provided in paras 4.184.20 and paras 5.45.14 of SSG25 1.The methodology and the criteria for the review

167、of safety factors,agreed upon with the national regulatory body,are provided in the PSR basis document.The review of the safety factors aims to determine the following:(a)The degree of validity of the licensing basis and safety documentation;16(b)The adequacy and effectiveness of provisions that ens

168、ure the safety of the installation until the next PSR,or if the PSR is used for supporting justification of LTO,for the whole period of LTO;(c)The extent to which the plant complies with current national and international regulations,guidelines and good practices in the field of nuclear safety;(d)Th

169、e adequacy of plant programmes considered in the safety factors relating to plant design,actual condition of in-scope SSCs,equipment qualification and ageing;(e)If the management system adequately addresses quality management and configuration management;(f)If TLAAs are valid for the period of LTO;(

170、g)If programmes for promoting safety culture focus on the pursuit of excellence in all aspects of safety management and human factors.The review of the safety factors is an iterative process that requires coordination and integration among the teams carrying out the evaluation of the individual safe

171、ty factors.Although the methodology of the review differs among safety factors,the evaluation focuses on identifying positive and negative findings with respect to the scope of each safety factor.Findings from the safety factor reviews are to be further assessed in the PSR global assessment with res

172、pect to their safety relevance.Findings from different international peer review services may provide valuable inputs into the evaluation of certain safety factors or may support the evaluation.Examples include IAEA technical safety review(TSR)services2,safety aspects of LTO(SALTO)3 peer review serv

173、ice for safety factors relevant to ageing management and LTO,and operational safety review team(OSART)4 peer reviews for assessing operational aspects of the plant.To obtain structured and comparable results,harmonization of methodical approaches for reviewing each safety factor is essential.This ca

174、n be achieved by setting out each safety factor into a clearly defined structure,typically based on regulatory requirements or plant operating practices.Most of the activities carried out at an NPP are managed and organized by programmes and processes with defined content,methodologies with defined

175、review criteria and quality management systems,as well as interfaces with each other.The established 2 IAEA technical safety review services include probabilistic safety assessment review,design safety review,generic reactor safety review,PSR and accident management review.3 An IAEA peer review serv

176、ice focusing on ageing management and organizational aspects of long term operation.A high level review of the PSR programme may be included in the scope.4 An IAEA peer review service focusing on operational safety.It includes the review of ageing related aspects,as well as programmatic review of PS

177、R.17structure of an individual safety factor could thus,as far as possible,support a review based on a process approach,consisting of two levels as follows:(a)High level review,where the review focuses on whether documentation for management and processes,high level policies and methodologies set ad

178、equate and clear requirements for fulfilling specific criteria.(b)Detailed review,which focuses on a particular situation at the plant addressed and managed by one of the aforementioned high level documents or processes;it is verified whether the established requirements are fulfilled and implemente

179、d in practice.Evidence of verification may be based upon procedures,records,schemes,measurements and tests.2.3.2.1.Applicable criteriaSelected criteria for review are typically brief,unambiguously formulated statements that provide a good basis for verifying the conformity of a specific aspect of a

180、PSRs safety factor.The basis for the formulation of a criterion is provided by referencing documents,whose order of priority is determined by their legally binding nature.Possible sources of reference documentation can be,among others,national laws and regulations,regulatory guidance and requirement

181、s,technical standards,IAEA requirements and safety guides or WANO documents.Where applicable,Western European Nuclear Regulators Association(WENRA)safety reference levels and documents of reviews organized by the European Nuclear Safety Regulators Group(ENSREG)may also serve as reference.Experience,

182、good technical practices and findings from research and development can provide inputs as to which criteria can be considered.In some cases,criteria can be identified by means of surveys,interviews and analysis of audits.The applicable criteria for reviewing the safety factors are established prior

183、to the review of safety factors in the PSR.These are discussed and agreed with the national regulatory body and thus set the desired level of review detail.This leads to a variable level of detail of the review(see para.5.5 of SSG-25 1)and to different review strategies tailored to the national regu

184、latory process(see para.4.4 of SSG-25 1).For example,some safety factors might be evaluated at the higher system level,rather than at the level of components.An LTO assessment requires a systematic,per component analysis,as described in section 7 of SSG-48 2.This difference needs to be considered wh

185、en using a PSR for justification of LTO,and the level of detail of a PSR needs to be adjusted to fit the scope of LTO.If the PSR is to be used in support of an LTO assessment,a relevant underlying methodology could be to follow SSG-25 1,where several criteria are provided for reviewing each safety f

186、actor in the PSR.18Sections 2.3.2.22.3.2.5 below describe the methodology for reviewing the plant related safety factors when considering LTO,including some adjustment to the individual safety factors methodology in cases where the PSR is used to support LTO.2.3.2.2.Safety factor 1(plant design)The

187、methodology for reviewing this safety factor is described in paras 5.195.26 of SSG25 1.Examples of aspects of an LTO programme covered by safety factor 1 include,among others,a review of the list of SSCs important to safety,including its documentation,and the compliance of the SSCs actual status wit

188、h the plant design(configuration management).Continuous plant processes in scope for this safety factor,such as the licensing basis management programme,the final safety analysis report(FSAR)management programme and configuration management,can also be used in an LTO programme.In cases where the PSR

189、 is used in support of LTO,the list of in-scope SSCs and out of scope SSCs specified in paras 5.16 and 5.17 of SSG-48 2 is used.This list and other relevant documentation are used to establish the compliance of current design basis with current nuclear safety standards,as well as to identify differe

190、nces.Where the PSR is to be used in support of LTO,any necessary safety improvements are identified(see para.3.5 of SSG-25 1).Benchmarking the design against other similar installations of comparable age can identify possible modifications to improve plant safety.In the specific case of a PSR suppor

191、ting LTO,such a benchmarking could focus on NPPs that have already undergone an LTO assessment.In the review of safety factor 1,according to para.5.19 of SSG-25 1,a clause by clause review of the listed standards is to be performed.2.3.2.3.Safety factor 2(actual condition of SSCs important to safety

192、)The methodology for reviewing this safety factor is described in paras 5.305.36 of SSG25 1.Examples of aspects of an LTO programme covered by safety factor 2 include,among others,the list of in-scope SSCs,their classification and intended function,a review of the in-scope SSCs functional capability

193、,a review of in-service inspection and maintenance programmes,and the assessment of the current physical status of in-scope SSCs.The current design basis and the list of in-scope SSCs,evaluated as part of safety factor 1,are required for the review of this safety factor.Plant programmes(maintenance,

194、in-service inspections,surveillance and monitoring)are checked against the nine attributes of an effective AMP provided in table 2 of SSG-48 2.One of the preconditions to LTO is that documentation relevant for the LTO assessment,such as plant programmes,is in place at the plant(see para.194.1 of SSG

195、-48 2).Plant programmes are in scope for safety factor 2,meaning that the review of this safety factor has to be performed for the verification of preconditions when the PSR is used to support LTO.2.3.2.4.Safety factor 3(equipment qualification)The methodology for reviewing this safety factor is des

196、cribed in paras 5.425.44 of SSG25 1.Examples of aspects in an LTO programme covered by safety factor 3 include,but are not limited to,the review of the qualification status of in-scope SSCs,review of the equipment qualification programme and an evaluation of activities for preserving the equipment q

197、ualification(e.g.environmental monitoring).Continuous plant processes in scope for this safety factor that can be used for justification of LTO are programmes for the plants lifetime management,the proactive obsolescence programme and programmes for the replacement of major components.The list of in

198、-scope SSCs,evaluated as part of safety factor 1,is required for the review of this safety factor.The adequacy of the organizations equipment qualification programme is assessed by reviewing the available documentation and the environmental conditions of qualified SSCs,checking qualification databas

199、es for completeness and assessing the effectiveness of the equipment qualification programme by means of plant walkdowns.One of the preconditions to LTO is that an equipment qualification programme is in place at the plant(see Section 3.1.2 of this publication and para.4.1 of SSG-48 2).2.3.2.5.Safet

200、y factor 4(ageing)The methodology for reviewing this safety factor is described in paras 5.495.51 of SSG25 1.Examples of aspects of an LTO programme covered by PSR relating to safety factor 4 include,but are not limited to,review of the ageing management strategy,review of AMPs and revalidation of T

201、LAAs.The review of safety factor 4 ensures that the ageing effects are adequately managed for the next PSR for the duration of LTO(see para.5.51 of SSG-25 1).If the PSR is used to support justification of LTO,the review of the ageing management strategy of the organization has to take into account a

202、 systematic approach described in SSG-48 2,summarized in the plandocheckact cycle(also known as the Deming cycle).A strategy for addressing technological obsolescence is also part of this safety factors review(see para.5.48 of SSG-25 1 and section 6 of SSG-48 2).In-scope SSCs are typically clustered

203、 into commodity groups in order to perform the AMR(see para.5.20 of SSG-25 1).The use of commodity groups could thus be considered when reviewing safety factor 4 if the PSR is used in support 20of LTO.The scope of this safety factor needs to be expanded by including the re-evaluation of TLAAs(see pa

204、ra.3.6 of SSG-25 1),such as radiation embrittlement of the reactor vessel and fatigue analysis.For an extended list of TLAAs,see appendix II of Safety Reports Series No.82(Rev.1),Ageing Management for Nuclear Power Plants:International Generic Ageing Lessons Learned(IGALL)6.3.COORDINATION OF PERIODI

205、C SAFETY REVIEW AND LONG TERM OPERATION ACTIVITIES3.1.AREAS IN WHICH THE LONG TERM OPERATION PROGRAMME COULD PROVIDE INPUTS TO PERIODIC SAFETY REVIEWThis section illustrates how PSR and LTO programmes can be coordinated to avoid repeating,recurrent or overlapping activities and to ensure that no imp

206、ortant activities are omitted.In areas where significant work has already been completed in the programme for LTO,the PSR of those areas could be limited to programmatic reviews.Those safety factors where this opportunity exists include safety factor 2(actual condition of SSCs important to safety),s

207、afety factor 3(equipment qualification)and safety factor 4(ageing).The selected programmatic approach to incorporate assessment results from LTO into a PSR needs to be reflected in the PSR basis document with an appropriate justification(see para.5.5 of SSG-25 1),as well as agreed with the regulator

208、y body.This section describes potential inputs expected from the LTO programme to the PSR programme and the stage at which the inputs could be ideally obtained.This section also provides considerations on the sharing of responsibilities and coordination between the LTO programme and the PSR programm

209、e necessary to justify LTO.3.1.1.Actual condition of SSCs important to safety(safety factor 2)When the timing of a PSR for the plant comes close to the intended period of LTO,certain activities inherently required for the development of a programme for LTO,as described in SSG-48 2,could be used to s

210、upport the review of safety factor 2.The methodologies for the review of safety factors presented 21in SSG-25 1,for which synergies exist within the guidance in SSG-48 2,include the following:(a)The current condition of SSCs(see para.5.30 of SSG-25 1).This is a review of the current condition of the

211、 plant using knowledge of relevant ageing effects and non-physical(obsolescence)issues.The review considers the expected condition of the plant over the PSR period or the intended period of LTO if the PSR is being used directly to justify LTO.(b)The adequacy of plant programmes that support confiden

212、ce in the condition of SSCs(see paras 5.31 and 5.32 of SSG-25 1).This consists of a review of the plant programmes(e.g.maintenance,obsolescence)and programmes that are used to demonstrate the condition of SSCs(e.g.in-service inspection,surveillance,water chemistry).(c)The alignment between the curre

213、nt condition of SSCs and their design basis(see paras 5.35 and 5.36 of SSG-25 1).This review assesses the implications of changes to design requirements or standards.In addition,the current and anticipated condition of the plant is checked for consistency against the current design basis.Major chang

214、es in the plants operational strategy(e.g.cycle length,flexible generation)or power rating could challenge the effectiveness of using the current condition of SSCs in assessments of future performance.These changes may coincide with a plants LTO as commercial considerations change or major enhanceme

215、nts are implemented.Sections 3.1.1.1 and 3.1.1.2 below identify those key steps in developing a programme for LTO that could directly support an assessment of safety factor 2 during the PSR.The extent to which LTO activities described in these sections may be beneficial to the PSR depends upon their

216、 timing and a mutual understanding of the requirements,processes and constraints associated with the two programmes of work.Identification of synergies at an early stage of the LTO programme is likely to offer significant and beneficial input into the review of safety factor 2.Although this section

217、focuses on synergies between LTO programme activities and safety factor 2,it is recognized that other safety factors,notably safety factor 3(equipment qualification),safety factor 4(ageing),safety factor 5(deterministic safety analysis)and safety factor 7(hazard analysis),can also benefit from the o

218、utput of the programme for LTO in this area.3.1.1.1.Preconditions for LTO assessmentsWhere existing plant programmes are to be credited for managing ageing during LTO,they need to be comprehensive and properly implemented.22Programmes monitoring the performance of,or detecting ageing effects of,in-s

219、cope SSCs 2 are particularly relevant for safety factor 2 and include the following:(a)Maintenance;(b)In-service inspection;(c)Surveillance;(d)Water chemistry.Data from these activities,from the plants maintenance programme and from targeted walkdowns,are used for trending and evaluating the conditi

220、ons of in-scope SSCs.These data are retained in an auditable format.These programmes need to be consistent with the nine generic attributes of an effective AMP as defined in table 2 of SSG-48 2.Data presented in the System Health Report,or other records credited for the management of ageing,also nee

221、d to be checked for consistency with the observed condition of in-scope SSCs,as well as for their effectiveness in assessing and mitigating ageing degradation.3.1.1.2.AMR for LTOA key activity of an LTO programme is an AMR,which is a systematic review of the ageing management of in-scope SSCs 2 that

222、 will,for each SSC,identify and assess ageing effects and degradation mechanisms,both potential and already observed.This review will identify the AMPs,new and existing,applicable to the SSCs whose effectiveness is assessed against the nine generic attributes of an AMP described in table 2 of SSG-48

223、 2.The AMR for LTO consists of the following steps:(a)Assessment of the current condition of the structure or component;(b)Identification of ageing effects and degradation mechanisms based on fundamental knowledge for understanding ageing;(c)Identification of the appropriate programme for ageing man

224、agement;(d)Reporting on the AMR.It is necessary to evaluate the impact of ageing on the capability of SSCs to perform their intended safety functions,so the current condition of those plant items is appraised.According to para.5.32 of SSG-25 1,“the validity of existing records should be checked to e

225、nsure that they accurately represent the actual condition of the SSCs important to safety,including any significant findings from ongoing maintenance,tests and inspections.”23In order to ensure that the scope of the credited AMP is comprehensive,an evaluation of the condition of SSCs should include

226、degradation mechanisms that have the potential to affect safety performance,the current and postulated service and environmental conditions,the range of installation sites and installation or maintenance history.Based upon a fundamental understanding of the SSCs safety functions,current condition an

227、d the relevant ageing degradation mechanisms,the AMR will identify the required ageing management strategy.Existing AMPs can then be reviewed for applicability to the SSCs under consideration and their completeness.The need for new AMPs or supplementary activities may be identified in areas where cr

228、itical data are identified as missing,in order to establish adequate ageing management.Such activities could include the following:(a)Grouping SSCs important to safety for the purpose of AMR according to functional system or type,as recommended in para.5.34 of SSG-25 1.(b)Performing special tests or

229、 monitoring the in-scope SSCs and the stressors responsible for ageing.Paragraph 5.32 of SSG-25 1 states:“Where data are lacking,they should be generated or derived by performing special tests,plant walkdowns and inspections as necessary.”(c)Performing and evaluating research and development activit

230、ies.(d)Replacing the in-scope SSC with one for which ageing is successfully managed.(e)Reviewing the established good practices in ageing management of in-scope SSCs that are comparable in terms of their equipment:Function(performance requirements under normal and design basis accident conditions,no

231、ting the qualified condition and/or post fault claim);Materials;Form(technology and physical construction);In-service condition(environmental,process or operating regime).(f)Reducing uncertainties.Paragraph 5.33 of SSG-25 1 states that“uncertainties may be reduced by considering evidence from simila

232、r components from other plants or facilities that are subject to similar conditions and/or knowledge of the relevant ageing processes and operating conditions.”The AMR will result in the identification of one or more AMPs for each in-scope SSC.The AMPs will either meet the nine attributes of an effe

233、ctive AMP or corrective actions will need to be identified and managed to ensure that comprehensive AMPs will be established.The status of these programmes,including the maintenance and up to date status of records,are part of the 24consideration of the actual condition of SSCs and are key inputs fo

234、r PSR safety factor 2.Safety factor 2 can benefit from following the guidance for the development of a programme for LTO provided in paras 7.1 to 7.41 of SSG-48 2,meeting the preconditions for LTO,completing the scoping process and establishing effective AMPs resulting from a comprehensive AMR.3.1.2

235、.Equipment qualification(safety factor 3)3.1.2.1.Concept and process for equipment qualificationParagraph 4.48 of SSR-2/2(Rev.1)3 states:“Appropriate concepts and the scope and process of equipment qualification shall be established,and effective and practicable methods shall be used to upgrade and

236、preserve equipment qualification.”The equipment qualification is required to demonstrate that the equipment will be capable of performing its intended safety function(s)under the range of service conditions specified for the nuclear installation in operational states and in accident conditions.This

237、includes an evaluation of the ability of systems or components to perform these safety functions under the effects of specified service conditions during plant states and during external events included in the design of the nuclear installation(e.g.seismic events).In contrast,internal fires,explosio

238、ns,internal flooding,tornadoes and hurricanes are not normally considered in the equipment qualification programmes because the design generally protects the equipment from the effects of these events.One of the objectives of equipment qualification is the prevention of common cause failures arising

239、 from the exposure of equipment to the specified service conditions.The equipment qualification process comprises three phases:(a)Establishment of appropriate design inputs(e.g.safety functions,service conditions);(b)Establishment of equipment qualification process steps(e.g.type testing,analysis,op

240、erating experience,combined methods);(c)Preservation of the status of qualified equipment.The equipment qualification includes seismic qualification,environmental qualification for mild and harsh environments(e.g.temperature,pressure,humidity,contact with chemicals,radiation exposure,meteorological

241、conditions,submergence and ageing mechanisms),and electromagnetic qualification(e.g.effects of electromagnetic or radiofrequency interference).25Although seismic qualification generally applies to all SSCs,the environmental qualification applies primarily to electrical and active mechanical equipmen

242、t,instrumentation and control(I&C)equipment,and components associated with this equipment(e.g.seals,gaskets,lubricants,cables,connections,mounting and anchoring structures).The qualification process for passive mechanical components(e.g.piping and vessels),for which the safety performance is assured

243、 by design,is performed in accordance with applicable codes.3.1.2.2.Review of equipment qualificationThe objective of the review of equipment qualification within safety factor 3 is to determine whether plant equipment subject to qualification has been properly qualified(including for environmental

244、conditions)and whether this qualification,as discussed above,is being preserved through an adequate programme of maintenance,inspection and testing that provides confidence in the delivery of safety functions until at least the next PSR(see para.5.38 of SSG-25 1).The review of safety factor 3 typica

245、lly includes an assessment of the following:(a)Changes in the equipment classification resulting from design modifications;(b)Qualification for all designed environmental conditions;(c)The availability of equipment that is required to fulfil safety functions;(d)Confirmation of the state of the equip

246、ment and any necessary supporting structures(such as equipment anchorage for seismic)that are necessary to ensure the equipment qualification;(e)Quality management provisions that ensure that an effective qualification programme is in place.Walkdowns and inspections are carried out to verify that th

247、e installed equipment matches the required qualification described in the safety documentation and to provide an input into the review of the adequacy of the plants procedures for maintaining equipment qualification.The plant equipment(or its component parts)that is subject to environmental qualific

248、ation has different time frames for which the qualified life is established(e.g.a qualified sensor has a shorter qualified life,whereas a qualified cable has a longer qualified life).Before the equipment(or some of its parts)can reach the end of its qualified life,it is either replaced at time speci

249、fied intervals(e.g.through an equipment replacement programme)or reassessed during its lifetime,taking into account the actual operating environment of the equipment and current understanding of equipment degradation mechanisms.In 26this regard,the PSR needs to verify whether equipment whose qualifi

250、ed life is about to expire will be replaced in accordance with a time specified interval,or whether the equipment can be requalified so that it can maintain its qualification status for the period until the next PSR.3.1.2.3.Preservation of equipment qualification a precondition for LTOA preservation

251、 of equipment qualification is required for the entire lifetime of the NPP.Preservation of equipment qualification is an integral part of the equipment qualification programme,which is a precondition for LTO.The preservation activities that are performed during the entire plant lifetime include the

252、following:(a)A periodic surveillance of qualified equipment,which ensures that:The operation and maintenance activities do not compromise the status of qualified equipment by changing the configuration,mounting orientation(horizontal or vertical supports)or electrical,pneumatic or hydraulic interfac

253、es;The systems and components continue to meet their performance requirements;Abnormalities in the configuration of the equipment are detected and corrective actions are completed in a timely manner to preserve the status of qualified equipment;The criteria for identifying premature ageing degradati

254、on are specified;During the periodic surveillance,if unexpected degradation is observed,the effect of this degradation on the capability of the equipment to perform the assigned safety function is evaluated.(b)A periodic or continuous monitoring of environmental conditions in both mild and harsh env

255、ironmental zones to ensure that the assumptions used to determine the equipments qualified life remain unchanged.For example,normal operating temperature in the reactor building is lower than considered in the design of environmentally qualified components(except core neutron detectors).In this rega

256、rd,the original time limited assumptions related to ambient temperature in the reactor building remain valid.(c)Detection of any hot spots(e.g.elevated temperatures,elevated radiation,humidity,chemical impact)that could result in a significant degradation mechanism originally not considered when est

257、ablishing the equipment qualified life.(d)Periodic replacement of component parts at time specified intervals(e.g.seals,gaskets,lubricants,filters)that are more susceptible to degradation.Such parts may need to be periodically replaced(i.e.as opposed 27to being reused)during maintenance activities s

258、pecifically undertaken for equipment qualification purposes.(e)Monitoring the storage conditions of the qualified equipment and spare parts.(f)Planning for obsolescence(e.g.records of the non-availability of replacement components from the original equipment manufacturer and the acceptability of app

259、ropriately qualified replacement components).(g)Configuration management(change control)to ensure that the implications of equipment qualification are appropriately considered whenever changes occur to the installation,to equipment or to operating,maintenance or replacement activities.3.1.2.4.Inputs

260、 from the LTO programme to the assessment of safety factor 3 in the PSRAn LTO programme includes a comprehensive review of the equipment qualification programme.The equipment subject to qualification is identified and included in the scope for LTO assessment consistently with an approach on scope se

261、tting for SSCs for LTO,as defined in paras 5.145.21 of SSG-48 2.The scope of review of equipment qualification for LTO is comparable to a standard review of safety factor 3 in the programme for PSR.However,the results of the re-evaluation of the TLAA related to equipment qualification may impact the

262、 initial assumptions(e.g.seismic,environmental parameters,electromagnetic interference)used for establishing the equipment qualification.In this case,the equipment qualification programme needs to be reviewed for potential impact.The review of equipment qualification for LTO includes the results of

263、a comprehensive review of the following subjects:(a)Monitoring of environmental conditions to verify whether:The assumptions in the equipment qualification are consistent with the ambient conditions in the part of the installation in which the equipment is installed;The design limits of the equipmen

264、t are not being exceeded;The status of qualified equipment remains valid.(b)Monitoring of the condition of qualified equipment to investigate whether:The initial assumptions used to establish an ageing programme are still valid;There are additional ageing effects not identified when the equipment qu

265、alification was initially established.28(c)Evaluation of ageing effects on the qualified status of the equipment to verify whether:Any new ageing effect or increase in the effects of previously known ageing effects are identified that would require the equipment qualification programme to be reviewe

266、d to determine whether changes in the qualified life or maintenance of the equipment are needed;Periodic preventive maintenance,predictive maintenance,equipment calibration,surveillance,testing,condition monitoring,corrective action,identification of trends in equipment failures and operating experi

267、ence reviews allow for identifying and mitigating unanticipated ageing degradation that was not accounted for when establishing the original equipment qualification;Appropriate condition indicators for a given type of equipment are selected to help detect changes caused by significant ageing effects

268、.(d)Revalidation of the TLAA related to equipment qualification.The results of processes that identify ageing related failures or significant material degradation of qualified equipment are used to assess the need to revise the maintenance,surveillance and replacement programmes that are related to

269、equipment qualification.3.1.2.5.Revalidation of TLAAsAs part of the revalidation of TLAAs,the environmental qualification is reassessed to confirm that time limited assumptions made when establishing the equipments qualified life remain unchanged,or,if these were changed,to establish how this affect

270、s the plant equipment qualification programme and update it accordingly.The revalidation of environmental qualification is performed when the intended period of plant operation is extended to demonstrate that the equipment will maintain its safety margin until the end of the extended plant life.Reva

271、lidating TLAAs during an LTO assessment could provide useful inputs into safety factor 3 where the effects of ageing degradation(e.g.due to irradiation,corrosion,humidity)are taken into account for equipment qualification(see paras 5.39 and 5.40 of SSG-25 1).The methodology for revalidating equipmen

272、t qualification consists of the methods and criteria for confirming that the initial assumptions used for environmental qualification are either valid or have changed.Revalidation of TLAA confirms whether:(a)The environmental zones and associated environmental parameters have changed;29(b)The equipm

273、ent installed within the environmental zones has adequate qualification;(c)The effects of ageing on the intended function(s)remain valid for the duration of LTO;(d)Any new significant degradation mechanism that could impact the status of the qualified equipment is identified;(e)Activities prescribed

274、 to preserve the qualification are still comprehensive.If the revalidation of TLAAs shows that the initial assumptions used for establishing the equipments qualified life have changed,the equipment qualification programme needs to be reviewed and corrective actions defined and implemented in a timel

275、y manner.Examples of corrective actions include the following:(a)Revision of the equipment qualification master list(e.g.adding new equipment for which significant ageing degradation mechanisms were identified);(b)Reassessment or requalification of equipment(or qualification of the newly installed e

276、quipment)for the new environmental parameters(e.g.seismic,environmental parameters due to accident conditions,electromagnetic interference,radiofrequency interference);(c)Replacement of equipment that did not pass requalification or for which the requalification could not confirm a qualified life fo

277、r the entirety of the extended plant life;(d)Modification of interfacing plant programmes(e.g.operation,maintenance,ageing management).A methodology to extend the equipment qualified life(e.g.cables)may consider reducing the excessive conservatism incorporated into the original qualification basis.F

278、or example,the excess conservatism adopted by the ageing model(e.g.Arrhenius model)to extend the qualified life may be reduced by:(a)Evaluating the initial assumption of the actual ambient and/or operating temperature;(b)Lowering overly conservative activation energy,as discussed in IGALL 6(and simi

279、larly in section X.E1,Environmental Qualification of Electric Equipment,of NUREG-2191,Vol.2,Generic Ageing Lessons Learned for Subsequent License Renewal(GALL-SLR)Report 7).For example,the reanalysis could replace the initially assumed ambient temperature in the Arrhenius model that was used to deri

280、ve the ageing temperature 30and duration.If the component was operating at a lower ambient and/or operating temperature,the reanalysis would result in a longer qualified life.The opposite is also true for higher actual ambient and/or operating temperatures.3.1.2.6.Reassessment of the qualified life

281、of equipmentThe qualified life of equipment is reassessed throughout the lifetime of the installation to take into account changes in the actual service conditions,such as temperature and radiation levels,and development in the knowledge and understanding of degradation mechanisms.Consequently,an ev

282、aluation of the data from monitoring environmental conditions and the condition of equipment is typically used to reassess the qualified life of equipment.A well established and documented technical basis is necessary to support an extension of the qualified life of equipment.In addition,any conclus

283、ions regarding the status of qualified equipment are re-evaluated to consider any changes in performance requirements or plant conditions.For example,methods such as re-evaluation of the conservativism of assumptions made in the original equipment qualification,type testing of naturally aged equipme

284、nt with additional ageing to support the extension of the qualified life,and equipment replacement and refurbishment are used for reassessing the qualified life.Changes in the stressor intensity(e.g.changes in temperature and radiation levels)may also be evaluated to reassess the qualified life.3.1.

285、2.7.Review of the equipment qualification programmeThe equipment qualification programme is a relevant programme to LTO.Crediting the equipment qualification programme for LTO includes evaluating its consistency with the nine attributes of an effective AMP,provided in table 2 of SSG-48 2,to determin

286、e whether the programme is effective in detecting,monitoring and preventing or mitigating any effects and degradation mechanisms that could impair the qualification status of the components.If the evaluations conclude that the existing equipment qualification programme is not sufficiently effective,

287、this programme needs to be improved or modified,consistent with the nine attributes in table 2 of SSG-48 2.3.1.2.8.IAEA framework for equipment qualificationIAEA Safety Standards Series No.SSG-69,Equipment Qualification for Nuclear Installations 8,provides guidance on how to meet the relevant safety

288、 requirements established in SSR-2/1(Rev.1)9 and SSR-2/2(Rev.1)3.Specifically,SSG-69 8 provides recommendations on a structured approach 31for establishing and preserving equipment qualification in nuclear installations,in order to minimize exposure to common cause failures of the equipment.Qualific

289、ation methods described in SSG-69 8 apply to both nuclear grade products and commercial grade products that need to be assessed or qualified to confirm their suitability to meet the functional and performance requirements while operating within specified service conditions.3.1.3.Ageing(safety factor

290、 4)In-scope SSCs are subject to some form of physical change caused by ageing,which could eventually impair their safety functions and service lives.To control the ageing degradation of SSCs within acceptable limits,an AMP for the NPP is implemented that covers the systematic arrangements aimed at p

291、roviding adequate ageing management measures,specifically engineering,operations and maintenance actions.The basic concept of ageing management as presented in SSG-48 2 covers both physical ageing and non-physical ageing.Physical ageing represents ageing of SSCs due to physical,chemical and/or biolo

292、gical processes.Physical ageing is managed using AMPs and other plant programmes(further discussed in Section 3.1.3.1)and using activities resulting from TLAA revalidation(further discussed in Section 3.1.3.2).Non-physical ageing is referred to as obsolescence.There are three different types of obso

293、lescence(for details,see also table 1 in SSG-48 2):(i)obsolescence of technology;(ii)obsolescence of regulations,codes and standards;and(iii)obsolescence of knowledge.Technological obsolescence is discussed further in Section 3.1.3.3.Within the PSR,the cumulative effects of ageing on NPP safety,the

294、effectiveness of AMPs and the need for improvements to AMPs,as well as technological obsolescence,are all covered and reviewed in safety factor 4(ageing).3.1.3.1.Review and improvement of plant programmes and AMPs for LTOThe main IAEA requirements relevant to AMPs and LTO are as follows:(a)Paragraph

295、 4.50 of SSR-2/2(Rev.1)3 states:“The ageing management programme shall determine the consequences of ageing and the activities necessary to maintain the operability and reliability of structures,systems and components.The ageing management programme shall be coordinated with,and be consistent with,o

296、ther relevant programmes,including the programme for periodic safety review.”32(b)Paragraph 4.53 of SSR-2/2(Rev.1)3 states:“The justification for long term operation shall utilize the results of periodic safety review and shall be submitted to the regulatory body,as required,for approval on the basi

297、s of an analysis of the ageing management programme,to ensure the safety of the plant throughout its extended operating lifetime.”An AMP covers the systematic arrangements that are aimed at providing adequate consideration of ageing management measures,specifically engineering,operations and mainten

298、ance actions to limit the ageing degradation of SSCs to acceptable levels.An AMP is a set of plant activities relating to the understanding,prevention,detection,monitoring and mitigation of a specific ageing effect on a structure,component or group of components.Effective ageing management for SSCs

299、includes maintenance,in-service inspection,testing and surveillance activities,with the goal of improving the reliability of SSCs(see Safety Reports Series No.82(Rev.1)6).In general,ageing effects on SSCs can be managed by AMPs and/or existing plant programmes.Examples of programmes to manage ageing

300、,as described in Ref.6,include the following:(a)Plant specific AMPs;(b)Plant specific maintenance strategies and programmes,including active components;(c)Activities resulting from TLAA revalidation;(d)Activities for preserving equipment qualification;(e)Plant specific programmes and procedures;(f)I

301、GALL based AMPs,either fleetwide or NPP specific.Several ways to accomplish ageing management include the following AMP types,as described in Ref.6:(a)Degradation mechanism specific AMPs(e.g.flow accelerated corrosion,stress corrosion cracking,thermal ageing);(b)Structure or component specific AMPs(

302、e.g.containment,reactor coolant pumps,control rod drive housing);(c)General AMPs(e.g.in-service inspection,chemistry).A list of AMPs is provided in appendix I of Ref.6.AMPs are divided into three groups AMPs for mechanical components,AMPs for electrical and I&C components,and AMPs for civil structur

303、es.33Ageing management activities,as described in SSG-48 2,can be specific to an SSC(e.g.reactor pressure vessel,pressurizer,reactor coolant pump,concrete containment structure)or commodity group(e.g.motors,valves,cables,pumps).They are typically included in either the plant specific AMPs or in the

304、following plant programmes,which are essential to ageing management and evaluation for LTO:(a)Maintenance programmes;(b)Equipment qualification programmes;(c)In-service inspection programmes;(d)Surveillance programmes;(e)Water chemistry programmes.The identification of programmes to manage relevant

305、ageing effect and degradation mechanisms for in-scope SSCs represents one of the outputs of the AMR.The programme for LTO demonstrates that ageing effects will be adequately managed for each in-scope SSC in such a way that their intended function(s)will be maintained throughout the planned period of

306、 LTO.Therefore,the existing plant programmes used for ageing management and existing AMPs are reviewed to ensure that they will remain effective in managing the effects identified for the planned period of LTO(see para.7.26 of SSG-48 2).A systematic review of the existing plant programmes ensures th

307、at all required activities related to ageing management are implemented and effective.The recommended method of review and evaluation of AMPs and plant programmes is to check their consistency with the nine attributes of an effective AMP as described in SSG-48 2.A detailed description of how to perf

308、orm the consistency review for the above mentioned plant programmes is given in Ref.6.The review and update of AMPs and existing plant programmes for the planned period of LTO is performed within the ageing management or LTO programme based on the results of the AMR.This review can lead to the follo

309、wing:(a)Confirmation that AMPs and existing plant programmes are effective at managing ageing effects for the planned period of LTO;(b)Modification of existing AMP(s)and/or plant programmes necessary to ensure fulfilment of intended safety function(s)of in-scope SSCs;(c)Need for,and development of,n

310、ew AMP(s)and/or plant programmes.34Reasons for the modification of existing AMPs or the development of new AMPs resulting from AMR conclusions could include the following:(a)The original scope of AMPs and plant programmes does not cover all in-scope SSCs for LTO;(b)Ageing effects of in-scope SSCs fo

311、r LTO are not identified and/or managed by the existing AMP;(c)Missing,inadequate or ineffective activities related to the existing ageing effects(e.g.monitoring,prevention,mitigation)are identified;(d)Insufficient activities related to the existing ageing effects(e.g.periodicity of inspection,condi

312、tion monitoring performed on number of samples)are identified;(e)Incomplete or missing documentation of in-scope SSCs is revealed;(f)Insufficient knowledge of operating history is identified;(g)Qualified life is not documented for the period of LTO;(h)An insufficient number of samples in surveillanc

313、e programmes for the period of LTO is identified;(i)Newly discovered ageing effects or more detailed analyses of existing ones are revealed;(j)Missing plant procedures,methodologies and/or guidelines are identified.As a next step,corrective measures to address deficiencies identified in the review o

314、f AMPs are proposed,and an action list is developed.Proposed corrective actions can vary in nature,such as:(a)Development of a new AMP;(b)Development of new plant procedures,methodologies and/or guidelines;(c)Modification and/or replacement of in-scope SSCs;(d)Modification of the existing AMP concer

315、ning programme scope(SSC),detection methods,condition monitoring,preventive and mitigation activities;(e)Improvement of implementation methodology and/or control of activities of the existing AMP;(f)Modification of operation regimes;(g)Performance of new analyses and/or tests.Based on the proposed c

316、orrective measures and the corresponding action list,an LTO action plan is developed and implemented.As the main goal of many plant programmes is to manage ageing,activities undertaken as part of the programme for LTO can significantly inform and/or 35support the review of safety factor 4.The follow

317、ing aspects need to be considered when coordinating PSR and LTO activities:(a)All in-scope SSCs are evaluated and reported when reviewing relevant safety factors;(b)The review of safety factor 4 is performed on a component level,not on a programme level;(c)Periodic review and reassessment of AMP eff

318、ectiveness is included in the LTO programme;(d)Periodic evaluation of plant programmes and AMPs is performed to pursue ageing management throughout the period of LTO;(e)The existing plant programmes credited for LTO fully cover all attributes of an effective AMP.3.1.3.2.Revalidation of TLAAsThe obje

319、ctive of revalidation of TLAAs is to demonstrate that ageing effects for considered in-scope SSCs will be adequately managed throughout the intended period of operation(see para.5.67(c)of SSG-48 2).This partly overlaps with the objective of safety factor 4(see para.5.46 of SSG-25 1).The results of r

320、evalidations of TLAAs are documented in safety factor 4.The design and safe operation of some in-scope SSCs may rely upon time limited assumptions with respect to ageing,which remain valid throughout the original design life of the plant.In the case of LTO,the validity of TLAAs is reassessed,extendi

321、ng to cover the entire period of LTO,as described in paras 5.645.69 of SSG48 2.The evaluation of TLAAs involves two time dependent parameters,as described in para.5.66 of SSG-48 2.The first parameter is the independent variable(e.g.neutron fluence,number of reactor startups,shutdowns)and is determin

322、ed from the operating history of the plant.The second parameter accounts for the ageing effects(e.g.radiation embrittlement,cumulative usage factor).The assessment of TLAAs is typically not part of the scope of a PSR based on SSG-25 1.However,a review of their revalidation is included if the PSR is

323、to be used in support of LTO(see para.3.6 of SSG-25 1).The structures and components subject to revalidation of TLAAs are identified during the scope setting process.A similar approach could be followed if a PSR is used to support an LTO assessment,as shown in figures 3 and 4 of SSG-48 2.In addition

324、,the LTO may generate additional time limited assumptions that need to be considered for the entire period of LTO(see para.5.65 of SSG-48 2 and section 7.2.3 of IAEA Nuclear Energy Series No.NP-T-3.24,Handbook on Ageing Management for Nuclear Power Plants 10).Revalidating TLAAs demonstrates 36that a

325、ll in-scope SSCs are capable of performing their intended safety functions throughout the whole period of LTO.Since TLAAs involve several time limited assumptions,their revalidation is closely related to those safety factors of a PSR that focus on time dependent aspects,of which ageing is the most p

326、rominent.Revalidation of TLAAs covers the intended period of LTO,which may be equal to or longer than the time span covered by a regular PSR(ten years).This means that the results obtained from the revalidation of TLAAs would also be valid for the time span covered by the PSR.3.1.3.3.Technological o

327、bsolescenceMany utilities are facing increasing demands related to technological obsolescence.Although this type of obsolescence does not manifest as physical ageing,it can result in the following:(a)Unreliable or unavailable safety related SSCs;(b)Commercial challenges from stretched or outsourced

328、supply chains or higher prices;(c)A shrinkage in the capabilities of industry and suppliers,and loss of diversity or loss of quality assurance of nuclear product lines;(d)An increased burden associated with the management of modifications.As part of safety factor 4,para.5.48 of SSG-25 1 identifies t

329、he obsolescence of technology used in the NPP as one of the technical aspects to be considered in this review.The attainment of LTO requires an in depth review of ageing management.Part of this review concerns the effectiveness of the proactive identification of obsolescence in advance and the corre

330、ctive actions taken to address it.A comprehensive technological obsolescence management programme is expected to be in place to identify,prioritize and implement solutions to the obsolescence of SSCs,particularly those important to safety.The review of the following safety factors needs to consider

331、technological obsolescence:(a)Safety factor 2(actual condition of SSCs important to safety):Paragraphs 5.27 and 5.29 of SSG-25 1 identify the importance of knowing the current and anticipated state of obsolescence of in-scope SSCs and later list the review of this topic as a task within the scope of

332、 safety factor 2.(b)Safety factor 4(ageing):Paragraph 5.48 of SSG-25 1 includes an evaluation of the impact from the obsolescence of technology.An obsolescence management programme satisfying the guidance given in section 6 of 37SSG-48 2 will meet the intent of para.5.48 of SSG-25 for PSR.In additio

333、n,the prioritization of obsolescence issues requires an understanding of the in-scope SSCs reliability and failure history.Data gathered to support this review are important inputs when considering the effectiveness of AMPs.(c)Safety factor 8(safety performance):Paragraphs 5.86 and 5.94 of SSG-25 1 determine whether the plant safety performance indicators and use of operating experience are effect