John H Moore Program Manager Fuel Channel Life Management Fourth International IAEA Conference on Nuclear Power Plant Life Management October 2327 2017 Lyon France Paper IAEACN24674 ID: 1019211
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1. PHWR Fuel Channel Life Management Activities by the CANDU Owners Group John H. MooreProgram Manager – Fuel Channel Life ManagementFourth International IAEA Conference on Nuclear Power Plant Life ManagementOctober 23-27, 2017Lyon, FrancePaper IAEA-CN-246-74
2. Presentation OutlineCOG OverviewOriginal CANDU target lifeAgeing mechanismsFuel Channel Life Management ProjectBenefits of the R&DClosing Remarks
3. COG MembersOperational UnitsInstalled CANDU Capacity (Mw(e)) Bruce Power86224 New Brunswick Power1680 Ontario Power Generation106618 Nuclear Power Corporation of India Ltd.184460 Korea Hydro and Nuclear Power42867 Societatea Nationala Nuclearelectrica21411 China National Nuclear Operation Co.21400 Nucleoeléctrica Argentina SA1648 Pakistan Atomic Energy Commission1137TOTAL4724445Overview of COGCANDU / PHWR Reactors WorldwideAll PHWR reactors worldwide are COG members.Also have 16 supplier participants and that # is rapidly growing.
4. Overview of COG COG Mission and VisionCANDU Excellence through Collaboration
5. Overview of COG The BusinessIt’s All About Value to the Members
6. Overview of COGThe OrganizationStrong cross-functional ties between lines of businessInformation exchange Nuclear safety & environmental affairsResearch & development OPEX EPRI interfaceCommunicationsWorkshops and conferencesSupplier participantsKnowledge managementNuclear safetyEnvironmental affairsRegulatory affairsIAEA interface and supportFuel channelsSafety & licensingHealth, safety & environmentChemistry, materials & componentsIndustry standard tool setSupport functionsPresident & CEOFuel channel life managementJoint projectsCANPACCIQBISFOKJoint projects & services
7. Overview of COGR&D and Joint Project InvestmentProjects to improve safety, reliability, cost for CANDU NPPsCOG Joint Project InvestmentCOG R&D Investment
8. Overview of COGCANDU NPP PerformanceCANDU NPPs Are Amongst the Top Performers Worldwide
9. CANDU Fuel channels Are the pressure boundary for CANDU reactors, but are much thinner than in PWRs/ BWRsConditions are aggressive:High temperatureHigh pressureHigh flowHigh neutron flux
10. Original CANDU target lifeConservative estimate was 30 years at 80% capacity factor.Equivalent to 210,240 effective operating hours at full power (EFPH) (i.e. 30 x 0.8 x 24 x 365).In early life, ageing mechanisms were not clearly understood and there were few operating ‘surprises’. This operating experience drove changes in design, materials, operation, inspection and CSA standards (primarily N285.8 “Technical requirements for in-service evaluation of zirconium alloy pressure tubes in CANDU reactors”).As plants approached their original target life, utilities became interested in life extension possibilities.Question became what is the safe limit to which these fuel channels can be operated to?
11. Ageing of fuel channels and spacersDeformation;Elongation/diametric expansion/sag/wall thinning;Can cause issues with end fitting bearing travel, fuel flow bypass, blister formation;Corrosion and deuterium ingress;Wall thinning and hydriding;Increased probability of delayed hydride cracking;Flaws and defects;Can be developed during fabrication, installation, commissioning or operation (e.g. flow causing vibration, foreign material debris causing damage to channels);Material property changes;Neutron flux and deuterium ingress reduce ductility (and so margin to failure).
12. Fuel Channel Life Management ProjectInitiated in 2009;Designed to accelerate base R&D program efforts and support continued operation of fuel channels beyond 210,000 EFPH;Operators needed a high level of confidence in the current life predictions and required high quality data to support:operational needs;life cycle management planning;licensing and license extensions beyond the original target life of 210k EFPH; reactor refurbishment plans.Project provides experimental data for operators and regulators to support fitness for service claims.
13. Fuel Channel Life ManagementProject PhasesFCLM project has been phased as follows:Fuel Channel R&D (base program) Continual workJP 4299 (burst test program) Completed (2009-2015)JP 4363 (FCLM Phase 1) Completed (2009-2015)JP 4452 (FCLM Phase 2) Completed (2013-2016)JP 4491 (FCLM Phase 3) In progress (2015-2018)JP 4983 (FCLM Phase 4) In progress (2017-2020)JP 4984 (Spacer Life Management) About to start (2018-2022)
14. Example experiment: Burst testingMeasures the fracture toughness of irradiated pressure tube material with elevated equivalent hydrogen concentrationsSpecimens are hydrided and temperature cycled to produce a morphology considered representative of in-service pressure tubes with high equivalent hydrogen concentrations;Specimens then pressurized to failure and then hydride morphology is analyzed.
15. Current efforts focus on:Improving fracture toughness modelInvestigating various effects on fatigue crack initiation (e.g. operating conditions, materials, flaw root radius, etc.), delayed hydride cracking initiation and hydride overload. Work is done with both non-irradiated and irradiated material.Probabilistic fracture evaluation computer modelling (acceptance criteria for probability of pressure tube rupture supporting FFS)Improving spacer integrity modelling and analysis (e.g. fatigue, loading impacts) to develop FFS guidelines. Includes elevated irradiation program of new spacer material using HFIR research reactor (ORNL) and examination of removed spacers from operating reactors. Includes crush testing, endurance testing.Third party reviews in support of regulatory submissions.
16. Fuel Channel Life Management Project ScopeDeuterium ingress and impact on material propertiesSpacer integrity and movementModelling and accelerated ageing in high flux reactorCrack initiation Development of refined models for fatigue, DHC, and overloadRelated fitness-for-service applicationsLeak-Before-BreakProbabilistic Core Assessment
17. What have we achieved?Increased understanding of degradation mechanisms on fuel channelChange in PT material properties;Change in material condition of Inconel X-750 spacer material Unique effects in CANDU environment (significant material transmutation), previously not considered;Custom rigs for spacer testing.
18. What have we achieved?Improved analytical and predictive tools (deterministic and probabilistic)New fracture toughness models Hydride overload modelFatigue modelInconel X-750 spacer testingRisk-informed decision making from a probabilistic approachProbabilistic core assessment for flawsProbabilistic core assessment for PT/CTProbabilistic Leak Before Break
19. Key Project SuccessesIncreased knowledge of how key fuel channel properties are changing with ageDevelopment of new and improved analytical tools and predictive modelsOPG and Bruce Power have received regulatory approval to operate beyond the original target life; The project work formed the basis and provided tools for:Updated reactor condition assessments;Improved life cycle management plans; andIncreased confidence in operation / business plans.
20. For current operationIncreased confidence in operational plansRefocused inspection and maintenance effortsSupport for license renewalsBenefits of the R&D to industry
21. Benefits of the R&D to industryLonger life!Bruce and Pickering units approved for continued operation to 247k EFPH life (5 years additional years of life assuming 80% CF)Darlington units to 235k EFPH (to planned refurbishment outages, 3.5 additional years of life assuming 80% CF)Looking at potential future extensions to 300k EFPH!
22. Benefits of the R&D to industryFor refurbishment projectsIdentified valuable refinements in component specificationsIdentified potential design improvements alternate spacer designs considered and adopted for refurbishments
23. Our knowledge of fuel channels has increased significantly, with a well directed programWe have improved confidence in CANDU, with our shareholders and regulatorsOPG and Bruce Power have received FC life extensions for the Pickering, Darlington and Bruce NPPs. Up to 80 years life is considered feasible.The CANDU-6 fleet of plants in South Korea, China, Romania, Argentina and New Brunswick (Canada) are interested in utilizing the body of research done to date. The ongoing challenge is to continue supporting safe, reliable and economic operation of CANDUs, while maximizing economic value of the investment. Closing Remarks
24. CANDU Excellence through Collaboration