1. 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

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

3. Overview of COG CANDU / PHWR Reactors Worldwide
COG Members
Operational Units
Installed CANDU Capacity (Mw(e))
Bruce Power 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.
1400
Nucleoeléctrica Argentina SA
648
Pakistan Atomic Energy Commission
137
TOTAL 47
24445
All PHWR reactors worldwide are COG members.
Also have 16 supplier participants and that # is rapidly growing.

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

5. Overview of COG The Business
$75M 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
The Business has grown steadily over the last several years – reflecting Members views that they get good value from COG It currently runs between $60M and $65M.
It’s All About Value to the Members

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

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

8. Overview of COG CANDU NPP Performance
CANDU 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/ BWRs
Conditions are aggressive:
High temperature
High pressure
High flow
High neutron flux

10. 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 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 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).

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

13. 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 ( )
JP 4363 (FCLM Phase 1) Completed ( )
JP 4452 (FCLM Phase 2) Completed ( )
JP 4491 (FCLM Phase 3) In progress ( )
JP 4983 (FCLM Phase 4) In progress ( )
JP 4984 (Spacer Life Management) About to start ( )

14. 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.

15. 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.

16. 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

17. 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.

18. 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

19. 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.
Beginning in 2010, the FCLM project has managed the execution of an extensive research and development work, bringing together leading industry experts to determine how material properties in the fuel channels are changing with age and what impact those changes could have on long term operability. The FCLM project supplemented the substantial base COG R&D Program, adding mare than 70 unique work packages covering both experimental work, analytical work and model development.
Through this research and development work, and with a mountain of inspection data, the project partners (OPG, BP and AECL) to assess the impact of specific degradation mechanisms which may challenge the integrity and functionality of pressure tubes and annulus spacers, critical components of the fuel channel, within the target service life.
In this presentation, I will be sharing with you the benefits of this project to the CANDU industry, and to OPG in particular.
As always, I will leave you with some thoughts on further enhancements that would like this community to address.

20. Benefits of the R&D to industry
For current operation
Increased confidence in operational plans
Refocused inspection and maintenance efforts
Support for license renewals
OPG, as well as our project partners, have a major investment in CANDU and have long term business plans that rely heavily on continued safe, reliable and economic performance of our plants for their full expected service life. This project has provided the information needed to assess one of our biggest risks, performance of aging fuel channel components. With the information, analytical tools, and predictive models generated by the project, we now have much increased confidence in our operational and business plans.
The information and tools generated have also allowed us to better understand fuel channel conditions and expected future degradation, which in turn has given us the insights to refocus and optimize our future fuel channel inspection and maintenance efforts. As fuel channel work is expensive, in terms of dollars / outage time/ and radiation dose, it is always important to maximize the value obtained for effort expended.
OPG has a major initiative underway to seek a 10 year license for Darlington station , a first ever in Canadian industry. This initiative is important to providing certainty in license requirements throughout the timeframe when we refurbish all four Darlington units. The fuel channel R&D work has shown that fuel channels can be safely managed over the expected service life, which will be key part of the basis supporting a 10 year license.

21. Benefits of the R&D to industry
Longer 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)
One of the key benefits to OPG was the ability to support continued operation of Pickering Units 5 through 8 up to a minimum 247,000 Equivalent Full Power Hours of operation. This is 37,000 hours longer than the nominal design life of 210,000 EFPH. 37,000 hours, equivalent to almost 5 years, of additional operation greatly enhances the value of the Station, provides stability to the Ontario Power system, keeps electricity prices stabilized for consumers, all while enhancing OPG’s business plan. The value of operating Pickering Units 5 through 8 is worth hundreds of millions of dollars over the coming years.
The Pickering station is currently in the midst of a re-licensing application, with Day Two hearings scheduled over the next few days. This re-licensing application is the first application within Canada to operate a unit beyond the nominal fuel channel design life of 210,000 EFPH.
Based on the results of the updated condition assessment, the Pickering fuel channel fitness-for-service plan was prepared and submitted to the Canadian Nuclear Safety Commission (CNSC) in June Within two short months, the CNSC accepted the plan with only minimal conditions, citing Ontario Power Generation's (OPG) firm understanding of the degradation mechanisms and a strong monitoring strategy as key indications that fuel channel integrity is well managed at Pickering. Demonstrating continued fitness for service of the Pickering fuel channels out to a minimum of 247,000 EFPH, along with a well defined and focussed inspection and maintenance program, have been key elements in support for the re-licensing application.
The fact that fuel channel life management was barely discussed at the Day One license hearing shows the thoroughness of the work done, in large part the FCLM project and Base R&D programs, to understand fuel channel condition and have sound predictive models.
Looking at potential future extensions to 300k EFPH!

22. Benefits of the R&D to industry
For refurbishment projects
Identified valuable refinements in component specifications
Identified potential design improvements
alternate spacer designs considered and adopted for refurbishments
As you know, OPG is preparing for the refurbishment of Darlington units over the next decade.
Clearly we want to refurbish using the best possible components, so that we can minimize the risks of achieving the full target service life for the refurbished units and minimize the fuel channel inspection and maintenance workload in the second life of the reactor.
In this respect, we are looking to interrogate the new information generated throughout this project to refine component specifications to get better material and improve component designs to achieve an improved and more uniform performance of components in the second life time.
One area of follow up work that OPG has initiated is a study to look at alternative designs (material and mechanical design) of the fuel channel annulus spacer.
I will talk more about our current spacers in a moment.

23. 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.

24. CANDU Excellence through Collaboration