Canadian Approach on regulatory issues regarding ageing management, long term

operation and plant life management

2nd PLiMShanghai, China

October 2007

Authors:A. Blahoianu, K. Kirkhope, T. Viglasky

Presented by: Andrei Blahoianu

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Introduction

• Ageing of safety related SSC’s can reduce its ability to meet design function and performance requirements

• Ensuring safety and reliability of ageing NPP’s is one of most important tasks facing both industry and regulators◦ Ageing fleet of NPP’s◦ Life extension / long term operation

• Effective Ageing Management is Key

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Presentation Outline

• Background on CANDU ageing issues • Regulatory Approach

◦ Response to Ageing Degradation◦ Ageing Management Programs◦ AM Reviews for Life Extension◦ Regulatory Standard on AM

• Path forward• Conclusion

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Background• 22 CANDU reactors licensed by CNSC

◦ Pickering A start-up in 1971◦ Darlington start-up in 1993

• In early operating years, Canadian CANDU plants operated with good capacity factors

• As plants aged, degradation mechanisms that were not previously identified began to have an effect

• Examples of CANDU ageing issues are summarized in the following slides

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Specific CANDU Ageing Concerns

FuelBundle

Pressure Tube

SpacerAnnulus

Gas

CalandriaTube

FUEL CHANNELSFUEL CHANNELS••Creep, DHC, property Creep, DHC, property changeschanges••Could lead to failure of PT, Could lead to failure of PT, inadequate fuel cooling, inadequate fuel cooling, impairment of SDS 2impairment of SDS 2∴∴Inspect, detect leaks, Inspect, detect leaks, chemistry control, replacechemistry control, replace

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Specific CANDU Ageing Concerns

1st

Feeder Bend

FEEDER PIPINGFEEDER PIPING••FAC, SCC, LowFAC, SCC, Low--T Creep T Creep CrackingCracking••Could lead to failure of feeder Could lead to failure of feeder piping, primary coolant leakspiping, primary coolant leaks∴∴Chemistry control, chemical Chemistry control, chemical inhibitors, inspect..... repair, inhibitors, inspect..... repair, replacereplace

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Specific CANDU Ageing ConcernsSTEAM GENERATORSSTEAM GENERATORS

••Corrosion, erosion, wearCorrosion, erosion, wear••Could lead to tube leaking or Could lead to tube leaking or rupture, possible releasesrupture, possible releases∴∴Chemistry control, primary Chemistry control, primary side cleaning, antiside cleaning, anti--vibration vibration supportssupports

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Specific CANDU Ageing Concerns

REACTOR ASSEMBLYREACTOR ASSEMBLY••Corrosion, erosion, fatigue, Corrosion, erosion, fatigue, creep, creep, embrittlementembrittlement of of different partsdifferent parts••Could lead to loss of Could lead to loss of moderator containment, moderator containment, shieldingshielding∴∴Monitoring, leak detection, Monitoring, leak detection, lifetime predictions/ condition lifetime predictions/ condition assessmentsassessments

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Specific CANDU Ageing Concerns

CABLESCABLES••Radiation and temp induced Radiation and temp induced embrittlementembrittlement••Could lead to insulation Could lead to insulation failure and current leaks and failure and current leaks and short circuitsshort circuits∴∴Testing, visual inspections, Testing, visual inspections, EQ programsEQ programs

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Specific CANDU Ageing Concerns

CONTAINMENT CONTAINMENT STRUCTURESTRUCTURE

••Cracking, creep, stress Cracking, creep, stress relaxationrelaxation••Could lead to loss of leak Could lead to loss of leak tightness, structural integrity, tightness, structural integrity, and possible releasesand possible releases∴∴Pressure testing, visual Pressure testing, visual inspection, concrete coatingsinspection, concrete coatings

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Regulatory Approach –Response to Ageing Degradation

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Regulatory Approach –Response to Ageing Degradation• This process is primarily reactive

◦ Responds to in-service inspection results and in-service failures

• CNSC also recognized that a more preventative approach NPP ageing is required

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Regulatory Approach –Ageing Management Programs• In 1990 CNSC issued a Generic Action Item for

licensees to address ageing to ensure ◦ Ageing degradation of SSCs’ condition is dealt with before challenging the defence-in-depth philosophy;

◦ Ageing related programs are effectively integrated to result in a disciplined overall review of safety;

◦ Safety analysis and TLAA remain valid;◦ Reviews of degradation mechanisms & OPEX;◦ Planned maintenance programs are adequate.

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Regulatory Approach –Ageing Management Programs• All licensees developed Plant Life Management (PLiM) or Ageing Management Programs based on IAEA (SRS 15) or industry guidelines (e.g. AP913).

• Life-Cycle Management Plans were also developed for major CANDU components

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Regulatory Approach –Ageing Management Programs• CNSC recognizes that the current level of AM effort may need to be increased to ensure plant safety as Canada’s NPPscontinue to age.◦ Strengthening the role of proactive ageing

management ◦ Life Extension Projects◦ Regulatory Standard on AM

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Regulatory Approach –AM Reviews for Life Extension• CNSC Regulatory Guide G-360

◦ Outlines key elements to be considered when a licensee undertakes a project to extend life of a nuclear power plant.

• Integrated Safety Review (ISR) ◦ Comprehensive review of the extent to which

plant conforms to modern standards, material condition, and the adequacy of arrangements for long term operation.

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Regulatory Approach –AM Reviews for Life Extension• ISR review areas (“Safety factors”) related to Ageing◦ Actual Condition of SSC’s◦ Ageing Management◦ Plant Design◦ Equipment Qualification◦ Deterministic and Probabilistic Safety

Analysis

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Regulatory Approach –AM Reviews for Life Extension• Specific review elements for the Safety Factor on Ageing Management include:◦ AMP policy, organization and resources.◦ Method & criteria to identify SSC’s covered by

AMP.◦ Evaluation and documentation of potential

ageing degradation, validation of TLAA.

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Regulatory Approach –AM Reviews for Life Extension• Specific review elements for the Safety Factor

on Ageing Management (cont.):◦ Availability of data for assessing ageing degradation.◦ Effectiveness of O&M programs in managing ageing of replaceable components.

◦ Effectiveness of Programs for timely detection and mitigation of ageing mechanisms and/or ageing effects.

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Regulatory Approach –AM Reviews for Life Extension• Results of ISR evaluation of Plant Condition and

Ageing Management should confirm:◦ Actual physical condition of SSC's.◦ Ageing mechanisms and their effects understood.◦ Ageing behaviour is consistent with predictions.◦ Life limiting issues have been identified ◦ Adequate margins exist to ensure safe operation for extended life / LTO

◦ Effective supporting programs (e.g. chemistry, maintenance, and inspection) in place.

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Development of S-334 Regulatory Standard on Ageing Management• Effective regulatory oversight of licensees’

AMPs is hampered by lack of explicit regulatory requirements on AM◦ Lack of common benchmark makes it difficult to ensure consistency and uniformity of compliance assessments of AMPs at different licensee sites

◦ Evident in ISR ageing reviews for life extension• CNSC staff regulatory program improvement

initiative to develop a new regulatory standard on AM requirements

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Development of S-334 Regulatory Standard on Ageing Management• Objectives of the regulatory standard:

◦ describe organizational characteristics of an effective AMP;

◦ describe general attributes of an effective AMP;

◦ inform NPP licensees of CNSC expectations and recommendations for AMP; and,

◦ facilitate CNSC evaluations of AMPs

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Development of S-334 Regulatory Standard on Ageing Management• Review of international and licensee best practices identified certain key aspects of an effective ageing management approach ◦ Proactive systematic (Plan, Do, Check, Act)◦ Life Cycle Approach◦ Periodic re-assessments of ageing

assumptions in design and programs

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Development of S-334 Regulatory Standard on Ageing ManagementProactive ageing management aims to:• Focus on important SSC susceptible to ageing• Provide for good understanding of their ageing• Minimize premature ageing • Adjust the use of proactive and reactive AM

strategies based on current understanding of SSC ageing

• Involve continuous improvement of SSC specific AM programs

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Development of S-334 Regulatory Standard on Ageing Management• Life-Cycle Approach◦ a proactive strategy requires AM activities throughout the lifecycle of NPPs and their SSC's.

◦ design, fabrication, construction and commissioning, operation and decommissioning

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Development of S-334 Regulatory Standard on Ageing Management• Life-Cycle Approach - Design

◦ Systematically identify all potential ADMs, ◦ Ageing effects appropriately accounted for in the safety analysis and in specifications

◦ Adequate safety margins for ageing and wear-out◦ Provisions for monitoring, testing, inspection to

� assess the progression of ageing mechanisms, � verify design predictions� identify unanticipated behaviour or degradation that may occur during operation.

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Development of S-334 Regulatory Standard on Ageing Management• Life-Cycle Approach - Construction

◦ Effects of fabrication techniques on the eventual ageing of the structure or component must be considered.

◦ Include provisions to monitor ageing degradation, such as the use of surveillance specimens particularly where inspection of a component is difficult or dangerous

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Development of S-334 Regulatory Standard on Ageing Management• Life-Cycle Approach - Operation

◦ Organizational arrangements � Responsibilities and interfaces for coordinating and implementing AM activities

� Enhance and coordinate existing programs for AM – e.g. O&M, chemistry control, EQ, periodic and in-service inspection, R&D.

◦ AM Program Implementation ◦ AM Program Review and Improvement

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Development of S-334 Regulatory Standard on Ageing Management• Life-Cycle Approach – Decommissioning

◦ Ageing management activities should continue into decommissioning for all SSCs required to perform during the decommissioning phase.

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Development of S-334 Regulatory Standard on Ageing Management• This regulatory standard will benefit both CNSC and its licensees:◦ NPP licensees will use it for self-

assessments of their AMPs◦ CNSC will use it as a regulatory basis for

ongoing compliance inspections of their AMPs & for comprehensive licensing assessments for operating plants, as well as for long term operation and new builds

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Path Forward• In addition to improving general AMP

requirements, CNSC foresees the need for further development in the areas of:◦ Risk-informed operation

� Using probabilistic tools for condition assessments and condition monitoring

◦ Process-based regulatory approvals for self-dispositioning of low-risk inspection indications in accordance with accepted FFSGs and procedures

◦ “Conventional System” inspection requirements

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Conclusion• Ageing management practices are now in

place at all Canadian NPPs• Appropriate licensing & compliance

activities are being carried out by CNSC • The CNSC and licensees are moving

towards a more proactive approach to address the ageing of Canadian NPPs◦ Regulatory Standard to increase AMP effectiveness

◦ Ongoing risk-informed research

ThankYou !