PHWR Fuel Channel Life Management Activities by the

PHWR Fuel Channel Life Management Activities by the CANDU Owners Group John H. Moore Program Manager – Fuel Channel Life Management Fourth International IAEA Conference on Nuclear Power Plant Life Management October 23 -27, 2017 Lyon, France Paper IAEA-CN-246 -74

Presentation Outline COG Overview Original CANDU target life Ageing mechanisms Fuel Channel Life Management Project Benefits of the R&D Closing Remarks 2

Overview of COG CANDU / PHWR Reactors Worldwide Operational Units Installed CANDU Capacity (Mw(e)) 8 6224 New Brunswick Power 1 680 Ontario Power Generation 10 6618 Nuclear Power Corporation of India Ltd. 18 4460 Korea Hydro and Nuclear Power 4 2867 Societatea Nationala Nuclearelectrica 2 1411 China National Nuclear Operation Co. 2 1400 Nucleoeléctrica Argentina SA 1 648 Pakistan Atomic Energy Commission 1 137 47 24445 COG Members Bruce Power TOTAL All PHWR reactors worldwide are COG members. Also have 16 supplier participants and that # is rapidly growing. 3

Overview of COG Mission and Vision Mission • Improve performance of CANDU stations worldwide through member collaboration Role • Complement IAEA, WANO, INPO and EPRI CANDU Excellence through Collaboration 4

Overview of COG The Business $75 M annual not-for-profit business bringing value to its Members by: Leveraging investments by identifying common needs and collaborating through Joint Projects Solving industry problems by either linking Members to solution sources or facilitating solutions Managing CANDU operationally focused R&D investment Providing OPEX – Events, Pattern Analysis, Alerts, Good Practices Linking Members to a warehouse of Information It’s All About Value to the Members 5

Overview of COG The Organization President & CEO Support functions Information exchange Joint projects & services – OPEX – Fuel channel life management – EPRI interface Nuclear safety & environmental affairs Research & development – Nuclear safety – Fuel channels – Safety & licensing – Communications – Joint projects – Environmental affairs – Workshops and conferences – CANPAC – Regulatory affairs – Health, safety & environment – CIQB – Supplier participants – ISFOK – IAEA interface and support – Chemistry, materials & components – Industry standard tool set – Knowledge management Strong cross-functional ties between lines of business 6

Overview of COG R&D and Joint Project Investment COG R&D Investment Projects to improve safety, reliability, cost for CANDU NPPs 7

Overview of COG CANDU NPP Performance CANDU NPPs Are Amongst the Top Performers Worldwide 8

CANDU Fuel channels Are the pressure boundary for CANDU reactors, but are much thinner than in PWRs/ BWRs Conditions are aggressive: High temperature pressure flow neutron flux 9

Original CANDU target life Conservative 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 N 285. 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? 10

Ageing of fuel channels and spacers Deformation; 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). 11

Fuel Channel Life Management Project Initiated 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 210 k EFPH; reactor refurbishment plans. Project provides experimental data for operators and regulators to support fitness for service claims. 12

Fuel Channel Life Management Project Phases FCLM project has been phased as follows: Fuel Channel R&D (base program) Continual work JP 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 (20182022) 13

Example experiment: Burst testing Measures the fracture toughness of irradiated pressure tube material with elevated equivalent hydrogen concentrations Specimens 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. 14

Current efforts focus on: Improving fracture toughness model Investigating 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. 15

Fuel Channel Life Management Project Scope Deuterium ingress and impact on material properties Spacer integrity and movement Modelling and accelerated ageing in high flux reactor Crack initiation Development of refined models for fatigue, DHC, and overload Related fitness-for-service applications Leak-Before-Break Probabilistic Core Assessment 16

What have we achieved? Increased understanding of degradation mechanisms on fuel channel Change 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. 17

What have we achieved? Improved analytical and predictive tools (deterministic and probabilistic) New fracture toughness models Hydride overload model Fatigue model Inconel X-750 spacer testing Risk-informed decision making from a probabilistic approach Probabilistic core assessment for flaws Probabilistic core assessment for PT/CT Probabilistic Leak Before Break 18

Key Project Successes Increased knowledge of how key fuel channel properties are changing with age Development of new and improved analytical tools and predictive models OPG 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; and Increased confidence in operation / business plans. 19

Benefits of the R&D to industry For current operation 1. 2. 3. Increased confidence in operational plans Refocused inspection and maintenance efforts Support for license renewals 20

Benefits of the R&D to industry Longer life! Bruce and Pickering units approved for continued operation to 247 k EFPH life (5 years additional years of life assuming 80% CF) Darlington units to 235 k EFPH (to planned refurbishment outages, 3. 5 additional years of life assuming 80% CF) Looking at potential future extensions to 300 k EFPH! 21

Benefits of the R&D to industry For refurbishment projects 1. 2. Identified valuable refinements in component specifications Identified potential design improvements alternate spacer designs considered and adopted for refurbishments 22

Closing Remarks Our knowledge of fuel channels has increased significantly, with a well directed program We have improved confidence in CANDU, with our shareholders and regulators OPG 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. 23

CANDU Excellence through Collaboration 24