Nuclear Technology Development and Economics
2021

Long-Term Operationof Nuclear Power Plants
and Decarbonisation
Strategies

NE A

Nuclear Technology Development and Economics

Long-Term Operation of Nuclear Power Plants
and Decarbonisation Strategies© OECD 2021
NEA No. 7524
NUCLEAR ENERGY AGENCY
ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENTORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENTThe OECD is a unique forum where the governments of 38 democracies work together to address the
economic, social and environmental challenges of globalisation. The OECD is also at the forefront of efforts
to understand and to help governments respond to new developments and concerns, such as corporate
governance, the information economy and the challenges of an ageing population. The Organisation provides
a setting where governments can compare policy experiences, seek answers to common problems, identify
good practice and work to co-ordinate domestic and international policies.
The OECD member countries are: Australia, Austria, Belgium, Canada, Chile, Colombia, Costa Rica, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Israel, Italy, Japan,
Korea, Latvia, Lithuania, Luxembourg, Mexico, the Netherlands, New Zealand, Norway, Poland, Portugal, theSlovak Republic, Slovenia, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States.
The European Commission takes part in the work of the OECD.
OECD Publishing disseminates widely the results of the Organisation’s statistics gathering and research on
economic, social and environmental issues, as well as the conventions, guidelines and standards agreed by its
members.

This work is published under the responsibility of the Secretary-General of the OECD. The opinions expressed andarguments employed herein do not necessarily reflect the official views of the member countries of the OECD or its
Nuclear Energy Agency.

NUCLEAR ENERGY AGENCYThe OECD Nuclear Energy Agency (NEA) was established on 1 February 1958. Current NEA membershipconsists of 34 countries: Argentina, Australia, Austria, Belgium, Bulgaria, Canada, the Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Korea, Luxembourg,
Mexico, the Netherlands, Norway, Poland, Portugal, Romania, Russia, the Slovak Republic, Slovenia, Spain,
Sweden, Switzerland, Turkey, the United Kingdom and the United States. The European Commission and theInternational Atomic Energy Agency also take part in the work of the Agency.
The mission of the NEA is:–

to assist its member countries in maintaining and further developing, through international
co-operation, the scientific, technological and legal bases required for a safe, environmentallysound and economical use of nuclear energy for peaceful purposes;–

to provide authoritative assessments and to forge common understandings on key issues as input
to government decisions on nuclear energy policy and to broader OECD analyses in areas such asenergy and the sustainable development of low-carbon economies.

Specific areas of competence of the NEA include the safety and regulation of nuclear activities, radioactive
waste management and decommissioning, radiological protection, nuclear science, economic and technicalanalyses of the nuclear fuel cycle, nuclear law and liability, and public information. The NEA Data Bank
provides nuclear data and computer program services for participating countries.

This document, as well as any data and map included herein, are without prejudice to the status of or sovereignty over any territory, to thedelimitation of international frontiers and boundaries and to the name of any territory, city or area.
This edition replaces the previous edition released on 29 July 2021. Corrigenda to OECD publications may be found online at:www.oecd.org/about/publishing/corrigenda.htm.
© OECD 2021
You can copy, download or print OECD content for your own use, and you can include excerpts from OECD publications, databases and multimedia
products in your own documents, presentations, blogs, websites and teaching materials, provided that suitable acknowledgement of the OECD assource and copyright owner is given. All requests for public or commercial use and translation rights should be submitted to neapub@oecd-nea.org.
Requests for permission to photocopy portions of this material for public or commercial use shall be addressed directly to the Copyright ClearanceCenter (CCC) at info@copyright.com or the Centre français d'exploitation du droit de copie (CFC) contact@cfcopies.com.
Cover photos: Beznau nuclear power plant (Swissnuclear); Maintenance of a low pressure section of a steam turbine at the Balakovo Nuclear Power Plant(CPI BalNpp, Alexander Seetenky/Creative Commons).

FOREWORD

Foreword

The long-term operation of nuclear power plants is a topic of growing interest as more and morecountries using nuclear energy are committing to increasingly ambitious decarbonisation targets.
Decisions regarding extending the operating licences for these facilities are complex and require
the simultaneous evaluation of multiple factors. In response to this growing interest, the Nuclear
Energy Agency (NEA) published in 2019 Legal Frameworks for Long-Term Operation of Nuclear Power
Reactors, a first-of-a-kind report that provides a comprehensive review of the legal and regulatory
implications of LTO of nuclear reactors. During that same year, the International Energy Agency
highlighted in Nuclear Power in a Clean Energy System the essential role of licence extensions tosecure sustainable development targets. Consistent with the holistic approach necessary for longterm operation of nuclear reactors previously described by the NEA, Long-Term Operation of Nuclear
Power Plants and Decarbonisation Strategies addresses the key policy, regulatory, technical, humanand economic aspects necessary to enable licence extensions during the transition towards a lowcarbon economy.
This publication is crucial for two reasons. First, with an average age of more than 30 years, thebulk of the existing nuclear fleet worldwide will inevitably be faced with operation decisions in
the next decade. It is thus important to have a clear understanding of both the main ageing
phenomena related to life-limiting components and of existing technical and operating
experience related to the refurbishment of nuclear facilities to support safe nuclear operations
beyond the initial licencing period. If most nuclear capacity is shut down after 40 years ofoperation, it could put electricity systems under considerable stress and place “Net Zero” goals
further out of reach. This situation will not only hamper decarbonisation efforts but also
undermine the affordability and the security of supply of electricity provision, with countries
retiring in parallel significant amounts of dispatchable, fossil fuel generation to meet emission
reduction targets.
Second, the timeline is becoming tighter to achieve carbon neutrality because of the increase ingovernment pledges to reach such objectives sooner, and in most cases by 2050. The
implementation of mature solutions will be essential to succeed in reaching such objectives.
Countries currently operating nuclear reactors will find in long-term operation of their plants asafe, ready-to-deliver and competitive option to support the most ambitious decarbonisation
pathways, while reconciling the affordability and security dimensions associated with electricity
provision. Although the choice to proceed with long-term operation is a matter of national policy,
Long-Term Operation of Nuclear Power Plants and Decarbonisation Strategies nevertheless provides
timely evidence for policymakers and decision makers on how to decarbonise current electricity
systems through the long-term operation of existing nuclear reactors, without making thisimmense endeavour more challenging than necessary.

William D. Magwood, IV
Director-General, Nuclear Energy Agency

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

3

ACKNOWLEDGEMENTS

Acknowledgements

The present study was written by Antonio Vaya Soler from the Nuclear Energy Agency Division of
Nuclear Technology Development and Economics (NTE) under the guidance of the NEA Ad Hoc
Expert Group on Maintaining Low-Carbon Generation Capacity through Long-Term Operation(LTO) of Nuclear Power Plants: Economic, Technical and Policy Aspects (EGLTO). The group ischaired by Arnaud Meert (Belgium) and Jan-Erik Lindback (Sweden). Michel Berthélemy (NTE),
Marc Deffrennes (formerly at NTE), along with Kimberly Sexton Nick and Pierre Bourdon (NEA
Office of Legal Counsel, OLC), participated in the drafting and review of the report. Management
oversight and additional input was provided by Sama Bilbao y León and Diane Cameron, theformer and current Head of the Division of Nuclear Technology Development and Economics. All
are gratefully acknowledged for their contributions.
The NEA would also like to thank the NEA member countries, international organisationsand various industry representatives who provided a large number of substantive and insightfulcomments during the review process of the report. A full list of those who contributed to thestudy is provided in Appendix 1 of the present report.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

5

TABLE OF CONTENTS

Table of contents

List of abbreviations and acronyms .................................................................................................. 11
Executive summary .............................................................................................................................. 13
Long-term operation: Supporting the sustainability, competitiveness and security ofthe electricity supply in ambitious decarbonisation strategies .................................................. 13
No major technical showstoppers for longer operating operations and adaptations ............. 15
Supply chain capabilities: An emerging source of concern despite continuing
improvements in nuclear operations ............................................................................................ 16
The role of government in enabling LTO of nuclear power......................................................... 17
1. Introduction ....................................................................................................................................... 19
1.1. The context: The challenge of decarbonisation efforts without the long-term
operation of nuclear power plants ......................................................................................... 19
1.2. Motivation, methodology and structure of the report ......................................................... 23
References .......................................................................................................................................... 25

Part 1: Analysis of the external environment for long-term operation.............................................. 27
2. Energy policy aspects ....................................................................................................................... 29
2.1. Overview of the existing nuclear fleet ................................................................................... 29
2.2. LTO and energy policy making: Opportunities and challenges .......................................... 34
References .......................................................................................................................................... 50
3. Regulatory and legal aspects .......................................................................................................... 53
3.1. LTO in nuclear regulations ...................................................................................................... 53
3.2. Regulation and LTO economics .............................................................................................. 63
References .......................................................................................................................................... 64

Part 2: Analysis of the internal capabilities of nuclear power facilities for long-term operation ......67
4. Technical aspects .............................................................................................................................. 69
4.1. Materials challenges for LTO ................................................................................................... 69
4.2. The LTO programme ................................................................................................................ 81
4.3. Replacement, refurbishments and upgrades ........................................................................ 86
References .......................................................................................................................................... 90
5. Operational and human aspects .................................................................................................... 95
5.1. Insights on the performance of nuclear power plants ........................................................ 95
5.2. The role of the supply chain ................................................................................................. 100
5.3. Nuclear workforce and competence assessment ............................................................... 110
References ........................................................................................................................................ 117

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

7

TABLE OF CONTENTS

6. Economic aspects ............................................................................................................................ 121
6.1. The generation costs of LTO.................................................................................................. 121
6.2. Recovering the costs of LTO .................................................................................................. 133
References ........................................................................................................................................ 143
7. Conclusions and policy recommendations: Enabling long-term operation ......................... 147
LTO is a safe and mature solution to foster ambitious decarbonisation
strategies ........................................................................................................................................... 147
Existing nuclear power plants can be enhanced to cope with a changing environment ......... 148
The supply chain is critical in sustaining operational and economic performance .............. 149
Recognising the full value of the LTO option in decarbonisation strategies ........................... 149
Appendix 1: List of experts ................................................................................................................ 151

List of boxes_
1.1:
2.1:
2.2:
2.3:
2.4:
3.1:
4.1:
4.2:
4.3:
5.1:
5.2:
5.3:
5.4:
6.1:
6.2:
6.3:
6.4:
6.5:

Examples of early closures of nuclear power plants for techno-economic reasons ....... 21
Replacing nuclear power in the short term........................................................................... 37
Policy uncertainty and nuclear power industry performance – The case of Belgium ..... 43
Assessing reliability concerns in low-carbon electricity systems ...................................... 46
Ensuring the adequacy of funding for decommissioning and waste management
activities through LTO – The case of Spain ........................................................................... 49
Examples of post-Fukushima safety measures .................................................................... 59
Overview on RPV embrittlement mitigation strategies in LWRs........................................ 72
Enhancing ageing management approaches with digital solutions andsimulation tools ........................................................................................................................ 83
LTO refurbishment examples ................................................................................................. 87
The role of INPO and WANO in the operational excellence of nuclear power ................. 97
The role of the size of the nuclear fleet and standardisation levels in the
supply chain: Overview of national opportunities and challenges.................................. 103
The KELPO project .................................................................................................................. 106
Building nuclear capabilities at the national level: The case of France .......................... 113
Estimating LTO overnight costs: The Swedish case ........................................................... 125
Quantifying the financial benefits of delaying the closure of a nuclear power plant ...... 128
LTO OCC and LCOE analysis for PHWRs .............................................................................. 130
The impact of market conditions on LTO............................................................................ 137
Pricing emission avoidance for nuclear power through ZECs: The US experience ....... 140

List of figures
E1:
E2:
1.1:
1.2:
1.3:
1.4:
2.1:
2.2:
2.3:

8

Levelised cost of electricity by technology, 2025 .................................................................. 14
Qualitative evolution of the performance level of a nuclear power plant over time ......... 16
Electricity generation by source in OECD countries, 2019 ................................................... 19
Plant closures by country and reason, according to stated policies in OECD
countries, 2011-2025 ................................................................................................................. 21
Nuclear capacity projections in Europe absent of further investment in newbuild and licence renewal regulatory trends in the United States..................................... 22
EGLTO methodological framework and structure of the report ......................................... 23
LTO by technology and country, 2020 .................................................................................... 30
Age distribution of nuclear power by region, 2020 ............................................................... 31
Global nuclear capacity by scenario, 2020-2050 ................................................................... 32
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TABLE OF CONTENTS

2.4: The energy policy trilemma for the long-term operation of nuclear power plants ........ 34
2.5: Configuration of the electricity mix and associated carbon footprint in selected
European countries, 2019 ......................................................................................................... 35
2.6: Breakdown of annual CO2 emissions avoided with nuclear power in the IEA NZE
by LTO scenario, 2050 ............................................................................................................... 36
2.7: Electric power generation by fuel, New York ISO, Jan 2017-Dec 2022 ............................... 38
2.8: LCOE by technology, 2025 ........................................................................................................ 41
2.9: Foreseen fuel management strategy for Doel units 1 and 2 in 2015 to meet 2003
Belgian phase-out law .............................................................................................................. 43
2.10: Electricity generation mix in France between 27-29 March, 2020 ...................................... 45
2.11: Evolution of nuclear and coal capacity in Europe according to stated policies, 2040 ..... 47
3.1: Generic definition of LTO......................................................................................................... 54
3.2: LTO approval approaches ........................................................................................................ 58
4.1: Illustration of the impact of irradiation on fracture toughness margins in the
inner wall of an RPV ................................................................................................................. 71
4.2: Qualitative impact of different RPV embrittlement mitigation measures ........................ 72
4.3: Example of pattern cracking and pop-outs of ASR-affected concrete ............................... 74
4.4: Cable exposed to high ambient, mechanical stress (sharp metal edge), andradiation effected cables on reactor head ............................................................................. 76
4.5: Qualitative representation of the impact of long-term shut-down periods on
SSC ageing ................................................................................................................................. 78
4.6: CANDU reactor design ............................................................................................................. 80
4.7: Different types of sensors inserted in the VERCORS mock-up ........................................... 83
4.8: Systematic approach for ageing management ..................................................................... 85
5.1: Qualitative evolution of the performance level of a nuclear power plant over time ...... 98
5.2: Evolution of global performance indicators for the existing nuclear fleet, 2020 ............. 99
5.3: Main nuclear suppliers by region and component versus installed capacityand distribution of main suppliers in the European region, 2020 .................................... 101
5.4: Companies holding an N-type ASME qualification, 2006-2019......................................... 102
5.5: Pyramid of competencies and skills for the nuclear industry workforce ....................... 111
5.6: Evaluation of the total number of STEM graduates in NEA/OECD countries.................. 112
5.7: Public energy technology R&D and demonstration spending by IEA member
country and by technology, 1977-2019 ................................................................................ 116
6.1: Generic distribution of costs and LTO investments over the lifetime of a nuclear
power plant.............................................................................................................................. 123
6.2: Yearly investments in the Swedish nuclear fleet, 2000-2045 ........................................... 125
6.3: Evolution of the decommissioning fund as a function of the LTO
period and the discount rate ................................................................................................. 128
6.4: LTO LCOE comparison between LWR and PHWR technologies ........................................ 130
6.5: Evolution of LTO LCOE for different LTO periods, and the cost profile of LTO
versus new nuclear build ....................................................................................................... 131
6.6: Sensitivity analysis of the LCOE of new build, and LTO of nuclear power plants ......... 132
6.7: Qualitative representation of the system value and technology cost for LTO ............... 133
6.8: Capacity additions in Europe by market regulatory framework ...................................... 135
6.9: Number of negative, hourly wholesale prices on selected, day-ahead trading
platforms.................................................................................................................................. 136
6.10: US nuclear operating capacity by market type, 2019 ......................................................... 137
6.11: Operation of the ZEC framework .......................................................................................... 140

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

9

TABLE OF CONTENTS

List of tables
2.1: Overview of nuclear stated policies in selected European countries ................................ 33
5.1: Potential classification of nuclear components according to their quality
assurance requirements ........................................................................................................ 106
5.2: Proposed new roles for regulatory approvals of plant-, system- and device level
design and manufacturing oversight for nuclear SSCs according to the KELPO
project ...................................................................................................................................... 107
6.1: LTO LCOE values for LWRs as a function of the LTO period, discount rate,
overnight costs and the capacity factor............................................................................... 129

10LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

LIST OF ABBREVIATIONS AND ACRONYMS

List of abbreviations and acronyms

AMP

Ageing management programme

AarhusConvention

Convention on Access to Information, Public Participation in
Decision-Making and Access to Justice in Environmental Matters

BDBEE

Beyond-design-basis external event

BWR

Boiling water reactor

CAISO

California ISO (TSO in California)

CANDU

Canadian deuterium uranium (reactor)

CASS

Cast austenitic stainless steel

CCGT

Combined cycle gas turbine

CCUS

Carbon capture, use and storage

CGD

Commercial grade dedication (process)

COVID-19

Coronavirus-19

CPUC

California Public Utilities Commission

DGR

Deep geological repository

DOE

Department of Energy (United States)

EGLTO

Ad Hoc Expert Group on Maintaining Low-Carbon Generation
Capacity through Long-Term Operation of Nuclear Power Plants:
Economic, Technical and Policy Aspects (NEA)

EIA

Environmental impact assessment

EPRI

Electric Power Research InstituteEspoo Convention

Convention on Environmental Impact Assessment in a
Transboundary Context

GCR

Gas-cooled reactor

gCO2eq/kWh

Grammes of carbon dioxide equivalent to kilowatt hours

Gen-II, III, III+, IV

Generation II, III, III+, IV (reactors, or reactor concepts)

GtCO2

Gigatonnes of carbon dioxide

GW

Gigawatt

HAZ

Heat affected zones

IAEA

International Atomic Energy Agency

IASCC

Irradiation-assisted corrosion cracking

I&C

Instrumentation and controls

INPO

Institute of Nuclear Power Operators

IPCC

Intergovernmental Panel on Climate Change

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

11

LIST OF ABBREVIATIONS AND ACRONYMS

JRC

Joint Research Centre (Europe)

kWe

Kilowatt electric

LCOE

Levelised cost of electricity

LTO

Long-term operation

LWGR

Light water graphite reactor

LWR

Light water reactor

MAI

Materials Ageing Institute (France)

MWh

Megawatt hour

NEA

Nuclear Energy Agency

NEI

Nuclear Energy Institute

NRC

Nuclear Regulatory Commission (United States)

NTE

Division of Nuclear Technology Development and Economics (NEA)

OCC

Overnight construction costs

OEM

Original equipment manufacturer

OPEX

Operational expenditures

PHWR

Pressurised heavy water reactor

PSR

Periodic safety review

PTS

Pressurised thermal shock

PV

Photovoltaic (solar)

PWR

Pressurised water reactor

RPV

Reactor pressure vessel

SALTO

Safety Aspect of Long Term Operation (IAEA missions)

SAMGs

Severe accident management guidelines

SBO

Station blackout

SDS

Sustainable Development Scenario (IEA)

SG

Steam generator

SLR

Subsequent licensing renewal (United States)

SSCs

Systems, structures and components

TEPCO

Tokyo Electric Power Company (Japan)

TLAAs

Time limited ageing analyses

TSO

Technical support organisation

TWh

Terawatt hour

UCL

Unplanned capability loss

VRE

Variable renewable energy

WANOWorld Association of Nuclear Operators

WENRA

Western European Nuclear Regulators Association

ZECs

Zero-emission credits

12

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

EXECUTIVE SUMMARY

Executive summary

Long-term operation: Supporting the sustainability, competitiveness and security ofthe electricity supply in ambitious decarbonisation strategies
Globally, nuclear power capacity is expected to grow if countries are to meet the carbon
emission reduction targets of the 2015 Paris Agreement. The International Energy Agency (IEA)
sees nuclear generation doubling to achieve carbon neutrality by 2050. The increasing role ofnuclear energy has also been recognised by the Intergovernmental Panel on Climate Change(IPCC). For those countries already operating nuclear reactors, two complementary means cancontribute to sustaining nuclear development in the energy transition: i) building new capacity;and ii) pursuing the long-term operation (LTO) of existing nuclear power plants.
Long-term operation can be defined as operation, justified by a comprehensive safetyassessment, that goes beyond a previously established time frame corresponding to initialdesign assumptions (typically referred to as “original design lifetime” and usually 30-40 years
depending on the design). These initial assumptions, however, do not represent a technicalconstraint inhibiting longer operating time frames and should not be confounded with theremaining, useful life of the facility, which is periodically re-evaluated taking into account theactual plant conditions and the latest available knowledge. In almost all cases, the useful life of
the facility is greater than the originally assumed design lifetime. Additional support for licenceextensions can also be found in most countries’ laws and regulations, where original operating
licences are not used to establish the ultimate operating lifetime of the plants. In fact, most laws
or regulations provide for indefinite terms, or allow for unlimited licence extensions.
As of the end of 2020, over 100 nuclear reactors worldwide were operating beyond their initial
40-year licensed periods, and more than 30% of the nuclear fleet was considered to be operating
under LTO conditions, according to existing country regulations. Building on the operational
experience of older plants, the role of LTO is expected to expand in the next decade as the averageage of the world nuclear fleet is greater than 30 years and more countries are committing to more
ambitious carbon emission reduction targets. The value of licence extensions nonetheless goesbeyond the decarbonisation dimension. A sustainable energy transition simultaneously tackles:i) environmental protection; ii) economics and affordability; and iii) electricity security and thereliability of electricity supply – or the so-called “energy trilemma”. Nuclear power, and inparticular licence extensions, perform well in all three of these dimensions.

Carbon management
LTO is not a decarbonisation tool per se but are rather an effective way to avoid emissions (i.e. in
the case that they are replaced by fossil fuel-burning power plants) and manage decarbonisation
pathways in a more predictable manner. Nuclear power could save up to 2.9 gigatonnes of carbon
dioxide (GtCO2) annually (almost 10% of today’s carbon emission levels) while supporting netzero emissions by 2050. Around 40% of these savings (i.e. 1.2 GtCO2/year) could vanish without
LTO, hampering global efforts to reduce carbon emissions. Recent experience shows that, in the
short term, nuclear capacity is likely to be replaced by a combination of variable renewableenergy (VRE) backed up by fossil fuel-fired plants, mainly because flexible solutions (e.g. longterm electricity storage, demand response, sector coupling) still do not have the required level oftechnological and industrial maturity for the large-scale deployment necessary to limit relianceon fossil-fired capacity. In countries with nuclear power, LTO acts as a backbone of low-carbon
capacity upon which other low-carbon solutions can be built to enhance overall decarbonisation
capabilities while the necessary innovations to meet climate targets progress in parallel towards
achieving commercial viability
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

13

EXECUTIVE SUMMARY

Affordability and investment efficiency
According to IEA/NEA estimates (IEA/NEA, 2020), in many regions of the world, licenceextensions are the most cost-competitive, low-carbon solution at the plant level (see Figure E1).
Overnight costs typically range between USD 450-950 per kilowatt electric (kWe) with anassociated levelised cost of electricity (LCOE) of USD 25-50 per megawatt hour (MWh). Thisvariability can be explained by the operational and investment history of each plant, as well as
by national regulations. Such ranges also capture potential reductions in the load factor overthe short term. Refurbishing existing plants is also simpler from a technical and managerial
perspective than building a new plant. This, combined with a positive learning curve sustainedby a significant number of recent and future projects, contributes to significantly lowering therisks of LTO delays or cost overruns.
At the system level, LTO will extend the dispatchability attributes of nuclear power overtime, thus reducing system stress, grid reinforcement needs and other system effects that could
increase the overall integration costs of high shares of VRE. Added benefits can be expectedfrom licence extensions, particularly as regards limiting the external costs induced by air
pollution and climate change.

Figure E1: Levelised cost of electricity by technology, 2025
250

LCOE [USD/MWh]

200
150
100

Fossil fueltechnologies

Gas (CCGT, CCUS)

Coal (CCUS)

Lignite (CCUS)

Biomass

Geothermal

Hydro (run of river, >= 5MW)

Hydro (reservoir, >= 5 MW)

Solar thermal (CSP)

Solar PV (residential)

Solar PV (commercial)

Solar PV (utility scale)

Offshore wind

Onshore wind (>= 1 MW)

Nuclear (LTO)

NuclearGas (CCGT)

Coal

0

Lignite50

Low-carbon technologies

Note: Values at 7% discount rate. Box plots indicate maximum, median and minimum values. Boxes indicate the central 50% of values(i.e. the second and third quartile). USD/MWh = US dollars/megawatt hour; CCGT = combined cycle gas turbine; CCUS = carbon
capture, use and storage.
Source: IEA/NEA, 2020.

Security and reliability of the electricity supply
LTO allows countries to extend the benefits that nuclear power plants provide in terms of fuelavailability and diversity, as well as in terms of ancillary services such as inertia, primary andsecondary frequency control and load following.
More importantly, one of the major security-of-supply concerns in most countries is system
adequacy, or the availability of physical capacity in the mid to long term. This issue is becoming
critical in the context of more ambitious emission targets, and will certainly require the closureof dispatchable generators such as coal and gas plants in future. In addition, nuclear phase-out
policies will further reduce capacity margins. In Europe, coal and nuclear capacity (40% of

14

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

EXECUTIVE SUMMARY

dispatchable generation in 2020) is set to drop 66% (160 gigawatts [GW]) by 2040, according tostated policies. The higher VRE additions are expected to have a limited impact given their low
capacity factors. Flexibility from interconnectors could also decrease with various countries
simultaneously phasing out dispatchable generators. The prospects of a large-scale deploymentof other flexibility options (e.g. long-term storage, demand response, sector coupling) remains
uncertain. LTO is, on the other hand, part of proven solutions that can enhance electricity
security in decarbonisation strategies.

Uncertainty
In general, deciding when to cease operations at an existing facility is subject to significantly
less uncertainty than making the decision to initiate new build or determining wheninnovations have reached full industrial and commercial viability. At the same time, it isextremely difficult to foresee, ex ante, the full impact that energy policies will have on societies,
particularly when significant political, economic, industrial and social implications are at stake.
Multiple factors could impact emission trajectories, raise system costs and undermine thereliability of the system, thus pushing governments to reconsider their initial plans. In addition,in the absence of a fully co-ordinated approach, individual countries do not have control overthe decisions of neighbouring countries, adding even more uncertainty to the process.
In this context, technology diversity, time and ease of implementation can be valuable
resources for policymakers. They are quickly accessible through timely LTO decisions and provide
greater flexibility in energy planning so as to better cope with a wide range of unforeseen risks.
Overall, LTO can be considered as a technology option in its own right that policymakers canmobilise to properly manage all of the dimensions of the energy transition and reduce the extent
of the challenge.

No major technical showstoppers for longer operations and adaptations
Nuclear facilities are not static assets. During their lifetimes, most of their structures, systems
and components (SSCs) are replaced as part of normal maintenance procedures and more
extensive refurbishments. These replacements mitigate the impacts of ageing and allow
operators to implement the necessary safety upgrades in accordance with the latest available
regulations, knowledge and operating experience.
There are, however, SSCs for which replacement is considered unfeasible for technicaland/or economic reasons. Consequently, the ageing of these components will ultimately limit
the operations of the plant. Critical life-limiting components are the reactor pressure vessel(RPV) and concrete containment structures. Depending on economic considerations, some coreinternals and cabling systems can also be considered as life-limiting. After several decades ofresearch and operating experience, the main ageing mechanisms, stressors and associateddynamics in life-limiting SSCs are now well understood. In practice, this technical evidence has
been combined with ageing management programmes (AMPs) to monitor and ensure that safetymargins remain acceptable during operations, regardless of ageing, in particular for life-limiting
components. The governing frameworks associated with LTO programmes also allow forinternal, periodic re-evaluations and external peer reviews in order to identify potential
shortfalls and provide access to the best international practices.
As a result, if utilities implement enhanced ageing management programmes using readily
available technical evidence, while performing the necessary repairs and replacements, longterm operation should not face any major, generic, technical barriers. Provisions in safetymargins and continuous monitoring through AMPs and research efforts will be needed in orderto properly anticipate and manage the potential technical risks that may arise, especially oververy long operating periods.
Industrial experience also shows that operators use the long outages of LTO refurbishments
to perform additional plant retrofits, such as power uprates, instrumentation and control
upgrades, flexible operations and overall plant modernisation activities. The overall objective isto adapt the plant to a changing environment while improving the economic value of the LTO
investment.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

15

EXECUTIVE SUMMARY

Supply chain capabilities: An emerging source of concern despite continuing
improvements in nuclear operations
The evolution of nuclear power plant performance indicators (e.g. unplanned capability loss,
unplanned scrams) suggests that, globally, nuclear operations have observed steady
improvements despite ageing. To explain these patterns, it is essential to examine all of thetechnical and organisational factors that will ultimately determine the safety and reliabilityof a nuclear facility. The combination of replacements, new technical progress (including
enhanced ageing management programmes), expanding operational experience andadditional safety upgrades enable operators to effectively manage the effects of materials
ageing (see Figure E2). The governing framework (e.g. national regulations, international peer
reviews) ensures that all these measures are implemented in a timely manner and arereviewed according to international standards so as to continuously improve the operation of
the plant from technical and organisational points of view. As a result, performance levels
should not abruptly decline (or even improve) as long as the necessary investments andenhancements continue to be carried out as part of the LTO programme.
These performance trends are also supported by industrial capabilities that remain robust
thanks to the constant inflow of projects and components being procured. SSC obsolescenceand supply chain issues have nevertheless become an emerging source of concern over recent
years as a result of policy uncertainties and degraded market perspectives, combined with highqualification needs. These trends vary from country to country depending on the size andstandardisation of domestic nuclear programmes. Thus far, the nuclear industry has been able
to manage these risks with the introduction of a commercial grade dedication, and higher
collaboration and harmonisation levels. Examples exist at the national level of regulators andoperators working co-operatively to reinforce the network of qualified suppliers. In parallel,
nuclear operators have planned and managed the retirement of an ageing workforce, althoughattracting and retaining talent has also become a major concern.
With nuclear power plants operating for longer periods, the ability of utilities to sustain
operational excellence and economic performance could be undermined by the lack of aqualified SSCs and skilled workforce. Nuclear industrial policies and international collaboration
will be key in enabling joint undertakings among governments, industry, regulators, research
institutes and academia necessary to sustain supply chain capabilities in the long term.

Performance level

Figure E2: Qualitative evolution of the performance level of a nuclear power plant over time

Year 0Materials
ageingReplacements

Technical
progress

Operational
experience

Governing
framework

Safetyupgrades

LTO

Time

16

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

EXECUTIVE SUMMARY

The role of government in enabling LTO of nuclear power
Most of the factors that could prevent nuclear reactors from operating over longer periods are infact policy driven. First of all, early closures are principally motivated by policy decisions. In
Europe, around 80% of the reactors that will cease operations by 2025 will do so for policy reasons.
The absence of stable and long-term policies in relation to the nuclear sector is thus a source ofadditional risk that can have an impact on nuclear activities and potentially raise LTO costs.
Secondly, in some regions, sustained, low wholesale prices that do not reflect the climate andreliability attributes of existing nuclear reactors are pushing some utilities to close nuclear
reactors earlier than initially planned. In the United States, where gas prices are low, eight units
have ceased operations since 2013 as a result of negative market prospects, and five more areplanned to be retired by 2022 for similar reasons. Market pressures can also reduce the economic
attractiveness of plant investments, ultimately inhibiting future LTO decisions. Various
regulations and support mechanisms are being used to support the development of low-carbon
technologies, and such regulations and mechanisms could be extended to LTO. This has been thecase, for instance, for zero-emission credits (ZECs), implemented in some US states to remunerate
carbon emission avoidance.
While efforts to keep the highest safety standards and operational performance must
continue, policymakers have a key role to play to support LTO in order to facilitate
decarbonisation strategies. With suitable and timely policies, nuclear countries hold the keys toenabling LTO programmes, and thus embracing the benefits. Some of these policies can be
rapidly implemented as they simply require policy commitment, ad-hoc support mechanisms
and/or the review of nuclear taxation regimes. Other policy reforms, such as structural market
reforms, may take more time. Overall, policymakers have a solid base to design policy packages
that combine various solutions to fit specific national circumstances.

Key policy recommendations
1. Maintain existing low-carbon capacity: Decarbonising the electricity system will be even more difficult
if existing low-carbon nuclear capacity is not included in the equation. LTO is a safe and expeditious
solution to avoid carbon emissions for decades to come and to manage emission reduction trajectories ina predictable manner under ambitious decarbonisation pathways.
2. Enlarge the technical basis of information on ageing mechanisms and their management: Current
LTO trends have been possible thanks to extensive research that has been conducted over the years.
Longer operational time frames will increase the demands on materials and life-limiting components andwill require continued R&D efforts to provide the necessary technical evidence for safe operation. Initiatives
fostering international collaboration on lessons learnt in ageing management should continue to be
pursued.
3. Support new technologies and plant enhancements: Nuclear operators have at their disposal robust
technical options to enhance and adapt their assets to an evolving context. With stable policies and risksharing initiatives, governments can facilitate their adoption and encourage additional performance
improvements during LTO.
4. Foster co-operation to capitalise on extensive industrial experience: An increasing number of utilities
around the world are undertaking LTO refurbishments and implementing new technologies. External peer
reviews and sharing of international operational experience are effective tools to secure best practices and toenable longer operating periods and plant adaptations. Timely dialogue and co-operation with regulators arein most cases possible to accelerate the adoption of the most innovative solutions.
5. Sustain supply chain capabilities and nuclear expertise at all levels: By committing to LTO, countries will
directly sustain existing supply chain capabilities and send clear signals to younger generations to renew thenuclear workforce. These actions should be complemented by joint undertakings with regulators, industry
and academia to foster nuclear expertise at all levels. Ongoing international collaboration can also play a rolein preserving knowledge and developing human capital in the nuclear sector.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

17

EXECUTIVE SUMMARY

18

6.

Build long-term and predictable industrial plans: High fixed cost technologies such as nuclear power
require policy certainty. Coping with policy risks is sometimes possible, but with a significant cost penalty.
Through nuclear industrial strategies, governments can provide the long-term, stable framework necessary
to plan and optimise licence extensions.

7.

Reform market regulations to ensure that the system value of long-term operation is adequately
remunerated: In many regions, different types of regulations and mechanisms are used to overcome
market challenges and support low-carbon technologies. These regulations and mechanisms can beextended to LTO in order to adequately remunerate the value that they provide to the system in terms ofemission avoidance, but also in terms of system adequacy and grid reliability. Other options such as thereview of nuclear taxation regimes can be envisaged as well.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

INTRODUCTION

1. Introduction

1.1. The context: The challenge of decarbonisation efforts without the long-term
operation of nuclear power plants
Meeting carbon dioxide (CO2) emission targets at the pace dictated by the Paris Agreement is anenormous and complex endeavour that will require the mobilisation of all mature low-carbon
technologies, including nuclear power. Today, with 444 reactors in operation worldwide,
accounting for 393 GW of net installed capacity (IAEA, 2021), nuclear power represents around
10.1% of the global electricity consumption, remaining the world’s largest source of low-carbon
electricity following hydropower (16.2%) (IEA, 2021a). In OECD countries, nuclear energy accounts
for 18% of the electricity generation, acting as the top low-carbon source of electricity in thesecountries (see Figure 1.1). The existing nuclear reactors around the world thus constitute a
backbone of low-carbon capacity that saves around 1.6 Gt of CO2 every year (IEA, 2019a).

Figure 1.1: Electricity generation by source in OECD countries, 2019
5 000

2%

TWh

4 000

13%

30%

3 000
14%
2 000
1 000
0
1990
Coal
Hydro
Other

1995

2000 2005
Oil
Nuclear20102015 2019
Natural gas
Renewables

18%

23%
Oil
Nuclear

Hydro
Coal

Renewables
Natural gas

Note: “Renewables” include contributions from solar photovoltaic (PV), solar thermal, wind power, geothermal energy, biofuels andtidal power. The “other” category regroups waste and other sources. TWh = terawatt hour.
Source: IEA, 2021a.

According to the International Energy Agency (IEA) Sustainable Development Scenario (SDS),
the role of nuclear power in low-carbon electricity systems is expected to increase, with global
generation growing 55% by 2040 compared to 2019 levels (IEA, 2020c). To reach carbon neutrality
globally by 2050, the IEA Net-Zero Emissions by 2050 Scenario (NZE), indicates that nuclear
output should at least double from 2020 levels (IEA, 2021d). 1 These figures are consistent with1.

Under the IEA SDS, the temperature rise remains below 1.8°C with a 66% probability, without relianceon global net-negative CO2 emissions, which is equivalent to limiting the temperature rise to 1.65°C
with a 50% probability. Also, global CO2 emissions will have fallen from 33 Gt in 2018 to less than 10 Gt
by 2050 and are on track to net-zero emissions by 2070 (IEA, 2019b). The IEA NZE supplements SDS andprovides additional analysis on what would be needed by 2030 to put carbon emissions on a pathway
to net-zero emissions globally by 2050 (IEA, 2020d).

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

19

INTRODUCTION

the projections of the Intergovernmental Panel on Climate Change (IPCC), which foresees asignificant rise of nuclear output by 2030 and 2050 under the large majority of scenarios
modelled (IPCC, 2018). 2 There are essentially two nuclear development levers to meet theseprojections: i) new nuclear build; and ii) long-term operation (LTO) of existing nuclear capacity,
the latter being the subject of the present report.
The International Atomic Energy Agency (IAEA) defines LTO of nuclear power plants as“operation beyond an established time frame […] justified by safety assessment [which] may takeplace within a broader regulatory process […]” (IAEA, 2018). The time frame is typically referred toas “original design lifetime” 3 , which is informed by initial design assumptions regarding theminimum expected lifetimes of non-replaceable structures, systems and components. These
initial design assumptions, however, do not represent a technical constraint inhibiting longer
operating time frames. These initial design assumptions should not be confounded with theactual remaining useful life of the facility, which is periodically re-evaluated by taking into
account actual plant conditions and the latest available knowledge. In almost all cases, theremaining useful life is greater than the originally assumed design lifetime. 4
Supported by an extensive knowledge base on ageing phenomena (NEA, 2006, 2012, 2015)
and considerable operating experience beyond 40 years 5, the number of licence extensions of
nuclear power plants has been steadily growing in recent years. For example, as of the end of
2020, over 100 operating reactors were older than 40 years (IAEA, 2021), and more than 30% of
the nuclear fleet was considered to be operating under LTO conditions, according to existing
country regulations (see Chapter 2). At the same time, nuclear reactors nonetheless continue tobe shut down prematurely, in some cases even before reaching their initial design lifetime. The
cumulative nuclear capacity that has been retired since 2011 will account for 82 GW by 2025
(20% of the today’s installed nuclear capacity) according to stated policies in OECD countries.
A closer look at the reasons 6 for these closures (see Figure 1.2) reveals that almost 70% aremotivated by external factors, such as policy decisions and negative market prospects. The
impact of policies is particularly acute, accounting for 45% of the total closures, and can belargely attributed to the accelerated nuclear phase-out following the Fukushima Daiichi nuclear
power plant accident in 2011, especially in Europe. Early closures based on market pressures
represent around a quarter of the closures, and they are principally located in several US statesand in Sweden. These regions experience low wholesale electricity prices that do not reflect thesystem value provided by existing nuclear capacity.
Another quarter of closures in OECD countries between 2011 and 2025 results from technoeconomic factors. In this case, the refurbishments required for LTO of a plant may constitute a
considerable technical challenge and/or be considered too costly to be economically viable
under market conditions prevalent at the time (see Box 1.1). This has been the situation in Japan
where the investments required to meet new safety standards could not be recovered over theremainder of operating lifetimes, pushing some utilities towards the decision to cease
operations (see Figure 1.2).

2.
3.

4.

5.
6.

20

Depending on the decarbonisation pathway, the increase in nuclear supply from 2010 levels varies between
59% to 106% by 2030 and between 150% to 468% by 2050.
The IAEA Safety Glossary (IAEA, 2019) defines design lifetime as “the period of time during which a facility
or component is expected to perform according to the technical specifications to which it was produced”.
Similarly, the Western European Nuclear Regulators Association (WENRA, 2011) defines design lifetime of a
nuclear power plant as “the minimal value of lifetimes of all its non-replaceable structures, systems andcomponents”, for example the reactor pressure vessel and the containment building (see Chapter 4).
This definition also demonstrates that the term “lifetime extension” is not completely accurate since thelifetime of the plant is not extended in practice. What is actually extended is the authorisation term or
operating licence based on a technical assessment of the capabilities of the plant to safely operate beyond
initial design assumptions. The role of initial design lifetime to inform the initial operating licence and LTO
is further explored in Chapter 3.
In the present report, it is assumed that a reactor enters LTO after the age of 40 years.
It is important to note that the closure of a nuclear power plant is a complex decision involving the evaluationof multiple factors and parameters. The reasons highlighted in Figure 1.2 point to the main drivers that,
according to the different experts consulted for the present study, had the most influence on the final decision.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

INTRODUCTION

Figure 1.2: Plant closures by country and reason, according
to stated policies in OECD countries, 2011-2025
25
5%

23%

45%

Number

20
15
10
5
0
27%

PolicyTechnico-economic

MarketAccident

Note: The technologies covered are LWRs and PHWRs. Plant closures resulting from policy decisions in Japan were made by theutilities, considering the requests from national and/or local governments.

Box 1.1: Examples of early closures of nuclear power
plants for techno-economic reasons
Crystal River 3 (United States)
Unit 3 of Crystal River in the United States observed damage in the containment building during the replacementof steam generators in 2009. The operation required a large hole be made in the containment structure. As partof preparations to make the opening in the containment building, tendons in the containment building wall weredetensioned. Then, while creating the opening, workers observed concrete delamination 7 affecting the outerbuilding wall. The concrete delamination issue was not expected and had not been seen before during steam
generator replacement activities at other nuclear plants. The damage was centred on the steam generator
opening and did not affect other bays of containment. Further engineering studies concluded that the main causeof the delamination could be attributed to the scope and sequence of the tendon detensioning. The operator
attempted to repair the damage, but later decided to decommission the reactor (NRC, 2010).
Ohi 1 and 2 (Japan)
In Japan, Kansai Electric Power Company decided to decommission units 1 and 2 of the Ohi nuclear power
plant in 2017 as a result of the technical difficulties associated with the implementation of new safety standards
introduced after the Fukushima accident. These units were in fact the only reactors in Japan using ice
condenser emergency cooling systems. In the event of an accident, these systems employ blocks of ice in abasket installed around the containment vessel to rapidly condense the steam that is released and reduce thepressure. In order to comply with the new applicable safety requirements, the walls of the containmentbuilding would have had to be thickened, among other significant safety upgrades. Additionally, the new
equipment to be installed in the containment building would have narrowed the amount of free space,
impeding operating and maintenance work (KEPCO, 2017).

7.

Concrete delamination is the detachment of thin layers of concrete from the concrete surface. As aresult, the surface becomes more vulnerable, potentially weakening the structure.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

21

INTRODUCTION

Oyster Creek (United States)
The American utility Exelon decided to decommission the Oyster Creek nuclear power plant ten years earlier than
expected in order to avoid the installation of two new cooling towers after revision of the water rule in the stateof New Jersey. This plant upgrade was considered too expensive by the owner, given the unfavourable market
conditions in the United States (NEI, 2018).

With the average age of the world’s nuclear fleet at 31 years (35 years in advanced
economies), the next decade will be considered critical for LTO. Without timely licenceextensions and slow capacity additions, nuclear capacity could sharply decline by 2040,
hindering global decarbonisation strategies. In Europe, a region characterised by higher policy
uncertainties, installed nuclear capacity could fall 44%, with a significant number of plants
closing before 50 years of operations (see Figure 1.3, left). These closures will have significant
implications, not only in terms of emission trajectories but also in relation to the affordability
and security of electricity provision by 2040 (IEA, 2019a).
At the same time, carbon emission reductions are far from being on track. In 2019, emissions
flattened following two years of increases (IEA, 2020a), but more structural changes will beneeded during the recovery phase of the COVID-19 pandemic to prevent emissions frombouncing back (IEA, 2020b). Recent estimates predict that carbon emissions are projected torebound and grow by 4.8% by 2021, the largest single increase over the last decade (IEA, 2021b).
More recently, various countries have pledged to achieve carbon neutrality by 2050-2060, which
will require greater decarbonisation efforts and the use of mature and shovel-ready, low-carbon
solutions. This task becomes even more challenging when dimensions such as affordability andenergy security – at the core of sustainable energy systems and policies – are taken into account.
In the United States, more than 90% of the nuclear fleet has received regulatory approval for
60 years of operation, and the number of reactors approved to operate until 80 years isincreasing. (see Figure 1.3, right). Additionally, utilities in France and Canada are also carryingout major refurbishment programmes to enable LTO of most of their nuclear units. These trends
confirm that, if utilities continue to implement the necessary repairs, replacements and ageing
management programmes using already available technical evidence, no major technical issues
should preclude the existing nuclear fleet from operating over longer periods so as to secure
more ambitious decarbonisation strategies.

Figure 1.3: Nuclear capacity projections in Europe absent of further investment in new build(left); and licence renewal regulatory trends in the United States (right)
140
-44%

120

GW

100
80
60
40
20
0
2020

2025

2030

2035

Europe

2040

100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
60 yearsCompleted

80 years

Under review

Intended

Note: OECD/NEA, based on NRC (2021) and NEI (2020).

22

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

INTRODUCTION

1.2. Motivation, methodology and structure of the report
In light of these trends, the NEA Expert Group on Maintaining Low-Carbon Generation Capacity
through LTO of Nuclear Power Plants: Economic, Technical and Policy Aspects (EGLTO) wasestablished in 2018 with the purpose of assessing the role of LTO in the energy transition, as well
as of identifying a key set of measures that could help maintain low-carbon capacity through LTO.

Figure 1.4: EGLTO methodological framework and structure of the report

External
analysisInternal
analysis

Enabling
LTO• Chapter 1: Introduction• Chapter 2: Policy aspects• Chapter 3: Regulatory and legal aspects• Chapter 4: Technical aspects• Chapter 5: Operational and human aspects• Chapter 6: Economic aspects• Conclusions and policy recommendations

EGLTO recognised the techno-economic work already performed by the NEA on LTO andproposed a methodological framework for the present study. In line with the conclusions of the
NEA study entitled The Economics of Long-Term Operation of Nuclear Power Plants (2012), thismethodology builds on the holistic nature of LTO decisions requiring the simultaneous evaluationof multiple factors.
To be effective, LTO first needs regulatory approval from national safety authorities. Thisdecision is taken after evaluation of the technical evidence and action plans provided by theutilities, which ensure that the plant will comply with the applicable safety requirements during
the extended period. Concurrently, operators will also assess the economic viability of thenecessary investment, taking into account expected market conditions and internal capabilities.
Finally, even if previous dimensions yield a positive output, there are various external factors
influencing the final LTO decision and future economic performance, such as public acceptance,changes in national policies and the introduction of new regulations.
In order to identify the key factors to enable LTO, a three-step strategic assessment istherefore considered in the present report, as follows:•Part 1 – Analysis of the external environment for long-term operation: After recognising
the role of LTO in decarbonisation strategies (Chapter 1), a comprehensive analysis of thecontext in which LTO will take place is undertaken. This analysis includes policy issues(Chapter 2) and regulatory and legal aspects (Chapter 3).

•

Part 2 – Analysis of the internal capabilities of nuclear power facilities for longterm operation: The external analysis is complemented by an assessment of theinternal capabilities of nuclear facilities to withstand the pressures imposed throughtheir ecosystem. In this case, technical issues (Chapter 4), operational and humanaspects (Chapter 5) and economics (including market issues) of LTO (Chapter 6) arecovered in detail.

•

Conclusions and policy recommendations – Enabling long-term operation: Based on
the outcomes of the two previous steps, it is then possible to identify the key factors thatwill enable LTO in the years to come under the best possible conditions.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

23

INTRODUCTION

The methodological framework and the structure of the report are summarised in Figure 1.4
above.
While the methodological framework presented above establishes a clear separation
between internal and external factors, the interactions and synergies existing between thesetwo dimensions, as well as among the various factors themselves, should not be neglected. As
will be illustrated many times in this report, policy action (external) can have a direct impact on
the ability of operators (internal) to perform LTO, and ultimately on their overall economic
performance. Another example is market issues, which are the result of policy decisions, or
regulatory and economic forces. These market issues will be addressed from different
perspectives in several chapters.
Lastly, another objective of the present report is to update the LTO cost data presented in
NEA (2012) and provide additional insight into the evaluation of such costs. The findings of thepresent study show a strong rationale for the evaluation of LTO as a technology option in its
own right, alongside new nuclear build and other low-carbon technology options. In this respect,
the cost and evidence collected within EGLTO for the elaboration of this study were also used
for the computation of country-specific LTO cost data presented in the 2020 edition of the
Projected Costs of Generating Electricity (IEA/NEA, 2020).

Key findings

24•

Nuclear power is the top low-carbon source of electricity generation in OECD countries, and it is expected
to play a growing role in meeting sustainable development goals elaborated via IEA and IPCC projections.
Two main nuclear development levers can be mobilised to meet these objectives: new nuclear build; andlong-term operation.

•

Long-term operation can be defined as operation, justified by a comprehensive safety assessment, that
goes beyond a previously established time frame corresponding to initial design assumptions (typicallyreferred to as “original design lifetime” and usually 30-40 years depending on the design). The initialdesign assumptions, however, should not to be confounded with the actual remaining useful life of the
facility, which is periodically re-evaluated taking into account actual plant conditions and the latest
available knowledge. In almost all cases, the useful life is greater than the originally assumed design
lifetime.

•

Long-term operation investment trends are steadily increasing, supported by technical evidence andgrowing operating experience. Nuclear power plants nevertheless continue to be prematurely shut down
in some regions, principally due to phase-out policies and expanding market pressures. Closures fortechno-economic reasons have also been observed when the necessary investments to continue
operation are not economically viable.

•

The next decade will be critical for LTO as the existing world’s nuclear fleet will reach an average age of
40 years. Without widespread licence extensions, nuclear capacity could experience a sharp decline,
compromising emission targets, as well as the costs and the security of electricity provision.

•

Making the decision for long-term nuclear operations is complex and requires the analysis of policy,
regulatory, technical, human and economic aspects. The present report therefore proposes a holistic
approach that reviews all of these dimensions in order to define potential enabling measures that will
help improve LTO prospects so as to support ambitious decarbonisation efforts.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

INTRODUCTION

References
IAEA (2021), Power Reactor Information System (PRIS) (database), https://pris.iaea.org/PRIS/home.aspx(accessed on 24 June 2021).
IAEA (2019), IAEA Safety Glossary, Terminology Used in Nuclear Safety and Radiation Protection 2018 Edition,
IAEA, Vienna, www.iaea.org/publications/11098/iaea-safety-glossary-2018-edition.
IAEA (2018), Ageing Management and Development of a Programme for Long Term Operation of Nuclear
Power, Specific Safety Guide, No. SSG-48, IAEA Safety Standards, IAEA, Vienna, wwwpub.iaea.org/MTCD/Publications/PDF/P1814_web.pdf.
IEA (2021a), Data & statistics (database), www.iea.org/statistics/ (accessed on 28 June 2021).
IEA (2021b), Global Energy Review 2021, IEA, Paris, www.iea.org/reports/global-energy-review2021.
IEA (2021c), Net Zero by 2050, A Roadmap for the Global Energy Sector, IEA, Paris,
www.iea.org/reports/net-zero-by-2050.
IEA (2020a), Global CO2 emissions in 2019 (Data Release), IEA, Paris, www.iea.org/articles/globalco2-emissions-in-2019.
IEA (2020b), Global Energy Review 2020, IEA, Paris, www.iea.org/reports/global-energy-review2020.
IEA (2020c), World Energy Outlook 2020, IEA, Paris, www.iea.org/reports/world-energy-outlook2020.
IEA (2020d), World Energy Model Documentation, IEA, Paris, https://iea.blob.core.windows.net/
assets/bc4936dc-73f1-47c3-8064-0784ae6f85a3/WEM_Documentation_WEO2020.pdf.
IEA (2019a), Nuclear Power in Clean Energy Systems, IEA, Paris, www.iea.org/reports/nuclearpower-in-a-clean-energy-system.
IEA (2019b), “Sustainable Development Scenario”, in World Energy Model, IEA, Paris,
www.iea.org/reports/world-energy-model/sustainable-development-scenario.
IEA (2018), World Energy Investment, IEA, Paris, www.iea.org/wei2018/.
IEA/NEA (2020), Projected Costs of Generating Electricity, OECD Publishing/IEA, Paris, www.oecdnea.org/jcms/pl_51110/projected-costs-of-generating-electricity-2020-edition.
IPCC (2018), Special Report: Global Warming of 1.5°C, IPCC, Geneva, www.ipcc.ch/sr15/.
NEA (2019), Legal Frameworks for the Long-term Operation of Nuclear Power Reactors, OECD Publishing,Paris, www.oecd-nea.org/law/pubs/2019/7504-long-term-operation-npp.pdf.
NEA (2015), “Questionnaire on Long-Term Operation of Commercial Nuclear Power Plants”,
OECD Publishing, Paris, www.oecd-nea.org/nsd/docs/2015/csni-r2015-13.pdf.
NEA (2012), The Economics of Long-Term Operation of Nuclear Power Plants, OECD Publishing, Paris,
www.oecd-nea.org/ndd/reports/2012/7054-long-term-operation-npps.pdf.
NEA (2006), Nuclear Power Plant Life Management and Longer-term Operation, OECD Publishing, Paris,
www.oecd-nea.org/ndd/pubs/2006/6105-npp-life-management.pdf.
NEI (2020), “Nuclear by the Numbers”, NEI, Washington, DC, www.nei.org/resources/factsheets/nuclear-by-the-numbers.
NRC (2021), Status of Subsequent License Renewal Applications, NRC, Rockville, www.nrc.gov/
reactors/operating/licensing/renewal/subsequent-license-renewal.html.
NRC (2010), “Crystal River Nuclear Plant – Special inspection Report”, NRC, Rockville,
www.nrc.gov/docs/ML1028/ML102861026.pdf.
KEPCO (2017), “Report to Fukui Prefecture and Ohi Town concerning the decision of closure of
Ohi Nuclear Power Plant Units 1 and 2”, KEPCO, Osaka, (in Japanese only)
WENRA (2011), Pilot Study on Long term operation of nuclear power plants, Reactor Harmonization
Working Group, WENRA.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

25

Part 1:
Analysis of the external environment
for long-term operation

ENERGY POLICY ASPECTS

2. Energy policy aspects

Policy aspects are key in the decision-making process regarding long-term operation (LTO) of a
nuclear power plant. Around 45% of the closures between 2011-2025 in OECD countries are
driven by policy decisions (see Figure 1.2). In Europe, the impact of energy policies on decisions
concerning LTO is more acute, accounting for about 80% of the total retirements over the sametime period; in some cases even before reaching the initial design lifetime.
At a time when many governments are undertaking major efforts to decarbonise electricity
systems, it is essential for policymakers to understand the opportunities and challenges of the
LTO of nuclear power plants in maintaining low-carbon dispatchable generation. Beyond
decarbonisation efforts, economic aspects (at the plant, system and social levels) and electricity
security concerns also need to be fully acknowledged.
After assessing the status and configuration of the existing nuclear fleet worldwide, thischapter will thus explore the role of LTO under the three pillars of energy policies:i) environmental protection; ii) economics; and iii) affordability and security, and reliability ofthe electricity supply. While some of the aspects addressed in this chapter are generic to nuclear
power, particular attention is given to opportunities associated with LTO, as well as to thepotential consequences of a sharp decline in nuclear capacity in the years to come.

2.1. Overview of the existing nuclear fleet
2.1.1.Status and configuration
With 444 reactors in operation (an installed capacity of around 393 GW) in more than
30 countries around the world, nuclear power provides 10% of the global electricity supply,and is thus the second source of low-carbon electricity after hydropower. In OECD countries,
this number is even higher, with nuclear power meeting 18% of electricity needs, making it
the largest source of low-carbon electricity in OECD countries (IEA, 2021b). Excluding research
reactors and other advanced concepts, the world’s nuclear fleet is composed of four maintechnologies: light water reactors (LWRs) 1, pressurised heavy water reactors (PHWRs), gascooled reactors (GCRs) and light water graphite reactors (LWGRs). LWR technology dominates,
accounting for more than 350 of the reactors (82% of the existing fleet) in operation,
principally in Europe, the United States, Japan and Russia (see Figure 2.1). 2 Mainly in operationin Canada and India, PHWRs represent 11% of the reactors in operation globally. GCRs and
LWGRs together make up the remaining 7%.
LWRs typically have an initial design lifetime of 30-40 years, depending on the reactor type.
Initial design lifetimes for PHWRs, GCRs and LWGRs are typically 30 years. These values are
consistent with the initial term length imposed by regulators in some countries (NEA, 2019a).
Taking into account these initial design assumptions, it is possible to estimate that about 35%

1.

LWRs cover three families of reactors: pressurised water reactors (PWRs), boiling water reactors (BWRs),
and Russian-type PWRs or VVERs. Generation-II (Gen-II) LWRs represent more than 80% of global nuclear
installed capacity (IAEA, 2021). Throughout this report, the term LWR refers to existing Gen-II designs andnot Gen-III/III+ concepts.

2.

LWRs, and in particular PWRs and VVERs, also predominate in nuclear development, representing 90%of the reactors under construction around the world.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

29

ENERGY POLICY ASPECTS

of global installed capacity (i.e. approximately 150 reactors) is already operating in LTO
conditions. 3 In absolute terms, the number of LWRs in LTO is greater than for any othertechnology. The ongoing expansion of this particular technology around the world offers an
explanation as to why most LWR units remain within their initial design lifetimes. PHWRs, GCRs
and LWGRs on the other hand were essentially deployed during the first nuclear wave in the1960 and 1980s, and had more limited global development. These trends, combined with an
initial design lifetime of 30 years, result in a relatively high share of reactors in LTO for suchtechnologies. Similarly, LTO patterns by country are also conditioned by reliance in someterritories on a particular technology (see Figure 2.1). For instance, Canada, Russia, Ukraine, andthe United Kingdom have high shares of reactors in LTO as their fleets have a significant numberof Gen-II VVERs, PHWRs and GCRs. Europe and the United States account for approximately 50%of the existing nuclear fleet and licence extensions. Countries such as the People’s Republic ofChina and Korea, where nuclear programmes were initiated in the 1990s, have a relatively young
fleet with no reactors in LTO.
Based on this evidence, the NEA Expert Group on Maintaining Low-Carbon Generation
Capacity through LTO of Nuclear Power Plants: Economic, Technical and Policy Aspects (EGLTO)
considered it appropriate to primarily address LTO issues related to LWRs. Additional insights
on PHWRs and VVERs are also provided in some sections of the present report hence covering
95% of the reactors in operation worldwide. While acknowledging the importance of LTO in
GCRs and LWGRs, these technologies remain outside of the scope of the present study.

Figure 2.1: LTO by technology and country, 2020
400

120

350

100

300

80
NumberNumber

250
200
150
100

60
40
20

50

0

0
LWRs

PHWRs

GCRs

LWGRs

Within initial lifetime
operating licence

Life-time extension
Long-term
operation

Note: European figures include Swiss reactors. The initial operating period by technology has been assumed to be 40 years forwestern LWRs and 30 years for PHWRs, VVERs, GCRs and LWGRs (see NEA, 2019a).
Source: OECD/NEA, using data from IAEA (2021).

2.1.2.Age distribution and nuclear capacity projections
A closer look into the age distribution of the current nuclear fleet provides some indication of
the potential LTO trends in different regions for the coming years. In general, global nuclear
capacity is rapidly ageing. During the 1960s, nuclear power experienced a rapid expansion
across the United States, and this expansion was then replicated in Europe between the 1970
and 1980s. After the Chernobyl accident in 1986, nuclear development experienced a major

3.

30

A survey performed in NEA (2019b), covering 80% of operating reactors worldwide, reveals that
129 reactors (30% of the global fleet) are already in LTO.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

slowdown, and capacity additions have been stagnating ever since in OECD countries. Over thelast five years, only 40 GW of new capacity has been added to the grid, mainly in non-OECD
countries and predominantly in China (IEA, 2020e). As a result, the age distribution of the global
nuclear fleet has “shifted to the top” with an average age worldwide of 31 years (see Figure 2.2).
The United States has one of the oldest nuclear fleets, with an average age of 40 years, and 50%of reactors have already entered LTO. While nuclear reactors in Europe are on average five years
younger compared to US reactors, almost 60% of the European fleet is within the range of
30-39 years. In other words, in the absence of widespread LTO, a significant share of low-carbon
capacity could fade away over the next decade on this continent.

Figure 2.2: Age distribution of nuclear power by region, 2020
> 40

20-29

Avg. Age

Age

30-39

10-19
< 10
0%

10%

20%

30%

40%

50%

60%

70%

45
40
35
30
25
20
15
10
5
0

40
36
31

% fleetUS

EuropeWorld

Note: European figures include reactors from Switzerland and United Kingdom.
Source: OECD/NEA, using data from IAEA (2021).

Planned LTO projections illustrated in Figure 2.3, nevertheless, suggest that licenceextensions will be a global trend, leading to average operating time frames greater than 40 years.
The combination of LTO with planned new build projects will also enable nuclear capacity todevelop and keep up with IEA Net-Zero Emissions by 2050 Scenario (NZE) 4 targets by 2030.
Beyond this time frame, the NZE nuclear capacity gap steadily grows, adding 330 GW to planned
new constructions by 2050. This will require capacity additions to increase up to 25 GW per year
starting from 2030: a pace 4 times greater than 2020 levels. Such nuclear deployment rates are
consistent with those already observed during the 1980s (IEA/NEA, 2015). Achieving them,
however, may require policy actions from today to secure the access to the necessary industrial
capabilities. On the other hand, considering 80 years of operations for existing reactors – anincreasing trend in the United States – could drastically ease the need for new nuclear projects
and help meet carbon neutrality commitments by 2050, in particular after 2040, where planned
LTO will experience a sharp decline. Overall, Figure 2.3 confirms the key role of LTO in the nearterm to sustain, along with new build, nuclear development prospects as well as its strong
potential to secure carbon neutrality by 2050.

4.

As indicated previously, NZE complements IEA Sustainable Development Scenario (SDS) and reflects
on the higher efforts needed to reach carbon neutrality globally by 2050. Capacity gaps using SDS as
the reference scenario are thus of a lower magnitude given the lower ambition of this scenario
compared to NZE.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

31

ENERGY POLICY ASPECTS

Figure 2.3: Global nuclear capacity by scenario, 2020-2050
900
800
700

GW

600
500
400
300
200
100
0
2020

2025

Planned LTO

2030

Planned Construction

2035
NZE gap

2040

2045
80 years

2050
40 years

Note: Planned LTO projections take into account announced closures and licence extensions (i.e. 60 and 80 years), in line withstated policies, market conditions and regulatory approvals principally in Europe and the United States. Planned construction are
essentially driven by new build scenarios in India and China. For the remaining projections, plannned LTO trends have beenadjusted assuming operating time frames of 40 years (all reactor types) and 80 years (only LWRs and PHWRs).

2.1.3.Policy environment
An overview of the political context surrounding LTO reveals contrasting trends depending on
the country. Europe, Japan and North America together possess more than 50% of the existing
nuclear fleet. Policy decisions in these regions could hence heavily influence nuclear capacity
prospects in the near future.
The United States, the country with the largest and oldest nuclear fleet, is globally very
supportive of LTO. 5 The first LTO programme in the United States started in 1983 (NEA, 2019a)
and ever since, utilities and regulators have been accumulating extensive experience in LTO
with an increasing number of reactors reaching the 40-year threshold. To date, from the 93
operating reactors in this country, 85 (more than 90% of the fleet) have been granted a firstlicence renewal, allowing operating time frames from 40 to 60 years. More recently, ten reactors
have filed for subsequent licence renewals (SLRs) from 60 to 80 years. Two were approved in
December 2019, two in March 2020 and another two in May 2021. A total of 4 applications arestill under review, three under acceptance review, and the owners of 11 additional reactors haveannounced their intent to file for SLRs, with 2 units having already submitted official letters ofintent to the regulatory body (NRC, 2021b; NEI, 2020). More recently, the NRC has been exploring
the possibility of developing a new licensing framework that would allow nuclear reactors to
run up to 100 years (NRC, 2021a). In Canada, the Darlington and Bruce PHWR units in Ontario
are undergoing a multi-year, multi-billion-dollar refurbishment that will allow the plants tooperate well beyond mid-century, reflecting the favourable LTO policies also present in thiscountry. Both projects are progressing well and are expected to be completed by 2026
(Darlington) and 2033 (Bruce). 632

5.

Policies may nevertheless vary from one state to another. For instance, the two units of the Diablo
Canyon nuclear power plant in California will be retired for policy reasons by 2025 (NEI, 2018).

6.

The Pickering nuclear power plant in Canada is planned to be decommissioned by 2024 for technoeconomic reasons. It will continue to secure electricity generation during the refurbishments at the
Darlington and Bruce nuclear power plants.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

In Europe, however, the political context is more heterogeneous and less favourable towards
LTO in some regions (see Table 2.1). Since 2011, a total of 13 reactors have been shut down forpolicy reasons: 11 in Germany and 2 in France. Considering the strong phase-out policies in
Belgium, Germany and Spain, and the uncertain situation in countries such as Sweden and
Switzerland, more than 50 reactors could be decommissioned by 2040 in the worst-casescenario: 7 around 44% of the nuclear installed capacity on this continent. Given constructionplans announced, this capacity drop could however be limited to 30%. 8 Consequently, Europe
could experience the largest decline in nuclear generation in advanced economies, droppingfrom 25% to 5% by 2040 (IEA, 2020c). These prospects are not on track with the European longterm strategy for a climate neutral economy that sets the share of nuclear generation at 12-15%
by 2050 (EC, 2018).

Table 2.1: Overview of nuclear stated policies in selected European countries
Country

Nuclearphase-out policy

New build

GermanyYesNo

11 units retired following the Fukushima
accident; 6 remaining units to be retiredby 2022.

Belgium

Yes

No

Complete phase-out by 2025. First units
to be retired by 2022.

FranceNo

Decision to betaken in 2021.

50% nuclear generation by 2035.

No

Complete phase-out between 2027 and
2035.

Spain

Yes

Policy risks

Comments

2 units shut down in 2020. 12 units to be
retired between 2025 and 2035, and 1
unit under construction.

Slovak Republic

No

Yes

New units under construction.

SloveniaNo

Yes

New unit under consideration.

SwitzerlandNoNo

No nuclear power plant closure calendar.
Energy Strategy 2050 indicates progressive
withdrawal from nuclear power.

SwedenNo

No

No nuclear power plant closure calendar.
100% renewables by 2040.

United Kingdom

No

Yes

New units under construction andplanned.

FinlandNo

Yes

New unit under construction and anotherbeing planned.

Czech Republic

No

Yes

New units planned.

HungaryNo

Yes

New units planned.

BulgariaNo

Yes

New units planned.

PolandN/AYes

New units planned.

Nuclear phase-out policy with a closure calendar.
No phase-out policies, but several units to be retired in the coming years.
Strong support for nuclear power.

7.

This scenario considers the retirement of the 7 units in Belgium, 12 in France, the 6 remaining units inGermany, 7 in Spain, 7 in Sweden, 4 in Switzerland and 15 in the United Kingdom, with no additional
new projects.

8.

New build projects in Europe could add roughly 15 GW of nuclear capacity by 2040, including those incountries such as Bulgaria, the Czech Republic, Finland, Hungary and Poland.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

33

ENERGY POLICY ASPECTS

Following the Fukushima Daiichi accident in March 2011, Japan has also experienced theconsequences of political turbulence and eroded public acceptance towards nuclear power. In
2019, the Tokyo Electric Power Company (TEPCO) announced the closure of the four units at the
Fukushima Daini plant in response to demands from local government (WNN, 2019). As of June
2021, 16 reactors have successfully completed the Nuclear Regulatory Authority (NRA) safety
reviews, 9 of which only 9 have already resumed operations. Additionally, four reactors havebeen granted a licence extension from 40 to 60 years, which, according to current Japanese
regulations, can only take place once. At the same time, the 5th Strategic Energy Planning
foresees a share of 20-22% for nuclear power in Japan’s electricity supply by 2030. Achieving thistarget will require the restart of at least 30 reactors and a concerted effort among stakeholders
to accelerate NRA reviews and local government agreements (IEA, 2021c).
In light of these trends, maintaining low-carbon capacity through the LTO of nuclear power
plants will require energy policy frameworks that fully acknowledge the potential societal
benefits arising from LTO decisions.

2.2. LTO and energy policy making: Opportunities and challenges
Translating sustainable development goals into energy policy making entails the analysis ofseveral interconnected dimensions. While environmental issues (e.g. carbon emissions) tend to
attract most of the attention of policymakers, they are not the sole objective when it comes toimproving energy sustainability and the value of electricity systems. A sound energy policy shouldtackle the three dimensions known as the “energy trilemma” in a simultaneously manner (seeFigure 2.4):•

environmental protection;•

economics and affordability of the electricity supply;•

security and reliability of the electricity supply.

In the next sections, the role of LTO is analysed under the prism of the energy trilemma,
highlighting the different opportunities at the disposal of policymakers, but also the potential
challenges of excluding LTO from the portfolio of the available technical solutions.

Figure 2.4: The energy policy trilemma for the long-term
operation of nuclear power plants
Environmental
protection

Sustainability
and system value

Economics andaffordability ofelectricity supply

9.

34

Security andreliability ofelectricity supply

The NRA safety reviews consist of two parts: a safety assessment based on the new regulatory
standards in place following the Fukushima accident (in particular on external hazards) and a briefing
by operators of concerned local governments.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

2.2.1.Environmental protection
Four aspects deserve particular attention when assessing environmental protection throughthe lens of the LTO of nuclear power plants: carbon management, safety and performance,
decommissioning and waste management, and other environmental impacts.

Carbon management
In terms of the carbon footprint (grammes of CO2 equivalent emissions per kWh [gCO2eq/kWh]),
nuclear power is one of the cleanest sources of energy with a median value of 12 gCO2eq/kWh(Bruckner, 2014). 10 Fission is a carbon-free process with no direct emissions. The low-carbon
footprint of nuclear power is the result of indirect carbon emissions (construction, infrastructure,etc.) combined with significant amounts of carbon-free electricity, thanks to high-capacity factors(i.e. 85%) and long operating time frames (i.e. 40 years or more).
As an example, European countries that have already achieved IEA SDS 2030 targets in termsof the carbon intensity of the electricity supply (i.e. under 81 gCO2eq/kWh [IEA, 2020a]) rely onhigh shares of nuclear generation (greater than 30%) and hydropower. 11 In fact, building a lowcarbon mix that takes advantage of the dispatchability of nuclear energy to effectively displacecoal and gas plants, enhances overall decarbonisation efforts (see Figure 2.5). This particularly
the case in regions with more limited access to hydropower resources and/or interconnections.

Figure 2.5: Configuration of the electricity mix and associatedcarbon footprint in selected European countries, 2019
100%

400

90%

356

350

80%
259

60%
50%

250
189

40%

183

150

30%

100

20%
10%

200

gCO2/kWh

300

70%

68

45

50

0%

0
SwedenFranceRenewables
Coal
OthersGermany

UK
Hydro
Oil
Carbon intensity

Denmark

Finland
NuclearNatural gas
SDS 2030

Note: The red dotted line represents a carbon footprint of the electricity system by 2030 – consistent with theParis Agreement – of 81 gCO2/kWh in Europe. Carbon intensity has been computed using the mean values
for each technology from Bruckner (2014).
Source: OECD/NEA analysis, based on IEA (2020a; 2021b; 2019a).

10.

Similar values are reported for wind power. The median carbon footprint for hydropower is
24 gCO2eq/kWh, followed by solar PV at around 45 gCO2eq/kWh. The technology with the highest
carbon footprint is coal, which has a median value of 820 gCO2eq/kWh. These numbers can varydepending on the assumptions and methodologies considered for their computation. A methodologythat is codified and widely used by the scientific community is the life cycle assessment, based on ISO
14040 and 14044 standards.

11.

This is the case, for instance, for France and Sweden.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

35

ENERGY POLICY ASPECTS

A contraction of nuclear capacity could therefore have severe implications on the trajectoryof carbon emissions (IEA, 2019). Assuming that the nuclear capacity gap to meet NZE targets isessentially filled with gas-fired plants, annual carbon emissions could rise by 2.9 Gt by 2050 12(approximately 10% of today’s carbon emission levels). Around 40% of these emissions (1.2 GtCO2)
are avoided by planned licence extensions, but their share sharply declines after 2040. A high LTO
scenario relying more extensively on 80 years of operations keeps carbon avoidance capabilitiesof the current nuclear fleet beyond 2040 while supporting new build to achieve carbon neutrality
targets (see Figure 2.6). Moreover, reactors with 80 years of operation could account for 25% of theemissions avoided by 2050, offering an effective way to cope with potential delays in the
deployment of new nuclear builds and/or to absorb shortfalls in emission reductions, if they do
not materialise at the expected rate.

Figure 2.6: Breakdown of annual CO2 emissions avoided with nuclear
power in the IEA NZE by LTO scenario, 2050
100%
17%

90%
80%

41%

70%

40%

60%
50%
40%

40%
24%

30%
20%
10%

19%

19%

Stated policies andregulatory approvals

High LTO

0%

Planned LTO

80 years

Planned construction

NZE gap

Note: It is assumed that nuclear power is displaced by gas with acarbon footprint of 490 gCO2eq/kWh (Bruckner, 2014).

Because LTO only concerns reactors already in service, it cannot be considered as an overall
decarbonisation option per se but rather can be seen as an effective means to manage carbon
emissions in a predictable manner. The predictability of LTO results from two main reasons:i) the maturity of this option built upon significant industrial experience 13 and ii) the low
uncertainty around closure decisions compared to licensing, building and commissioning new
capacity. Furthermore, recent experience shows that the closure of existing nuclear power
plants without the construction of new low-carbon dispatchable capacity (e.g. nuclear andhydropower) could result in an increase in the carbon footprint of the electricity sector in the
short-term, as nuclear capacity is likely to be replaced by a combination of VRE backed up by
fossil-fired plants, especially gas plants. For the time being, stability and flexibility solutions (e.g.
long-term electricity storage, demand response, sector coupling) do not have the required levelof technological and industrial maturity for the large-scale deployment required to limit
reliance on fossil-fired capacity, in particular at high shares of VRE (see Box 2.1). In thosecountries with nuclear power, LTO secures a backbone of low-carbon capacity upon which new

36

12.

These numbers could double if nuclear capacity is replaced by coal plants.

13.

As indicated previously, more than 30% have already entered LTO.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

low-carbon solutions can be built so as to enhance overall decarbonisation capabilities while
innovative solutions gain in maturity. The necessity for mature and shovel-ready solutions suchas LTO also becomes more apparent since emissions reductions target by 2030 are becoming
increasingly ambitious and more countries are pledging to reach carbon neutrality by 2050. 14

Box 2.1: Replacing nuclear power in the short term
A nuclear power plant produces large amounts of low-carbon electricity upon demand. Load factors fornuclear reactors are typically of 85% and these facilities possess certain manoeuvrability allowing to control
their power output. Furthermore, they are synchronous generators with a rotating mass coupled to grid thatstabilises the system by providing inertia and short-circuit power (i.e. system strength). When the system faces
a disturbance, these machines automatically help to stabilise the grid frequency by releasing some of the
kinetic energy stored in their rotating rotor before other reserves take over. These aspects are essential for thesmooth operation of any electricity system, and conventional generators with a rotating mass such as nuclear
station are the cornerstone network stability. Consequently, when replacing a nuclear power plant, anequivalent amount of low-carbon electricity will be required but also solutions that provide the same level ofservice to the grid in order to avoid potential system disruptions.
A low-carbon technology option with similar attributes to nuclear power stations is hydropower. Most of thebest locations, however, are already equipped reducing overall hydropower potential. In addition, its
dependence on orographic conditions makes of hydropower a low-carbon resource not available in all
countries, which stunts its scalability. Wind and solar power are also part of the low-carbon solutions available
to fill the gap left by a nuclear facility. These technologies are cheap, scalable and can be deployed in shortlead-times, however, they are intrinsically variable and dependent on weather conditions. Their output can bepredicted and curtailed but never dispatched on demand, requiring the rest of the residual (and dispatchable)
system to adapt once they are generating. Additionally, in contrast to conventional power plants, VRE are nonsynchronous generators and their capability to provide power strength to stabilise the network is very limited.
In practice, VRE should be complemented with other technologies and measures to equate the level of service
provided by a nuclear power plant.
While the variability of solar and wind is manageable at low shares, higher penetration rates will increase thestress on the system, especially at shares greater than 30-40% (NEA, 2019). According to the IEA (2021a), an
electricity system solely built upon high shares of VRE resources must meet four strict conditions to betechnically feasible: i) ability to provide system strength under significant inertia reduction ii) adequate system
adequacy and flexibility levels at all times iii) availability of sufficient operational reserves and iv) substantial
grid development. The report finds that, while solution exist to provide system strength and flexibility in
networks with high shares of VRE, they are still at the research and development stage and therefore not readyto be deployed at scale. Greater technical difficulties are likely to be encountered in highly distributed systems.
This is consistent with the findings of IEA (2020b) which indicates that more than 50% of the technologies
needed to meet carbon neutrality by 2050 have not still reached industrial maturity. At the same time, given
the absence of proof of concept and operating experience of large-scale electricity systems with high sharesof VRE, technical challenges may arise. Moreover, costs and social implications associated which such systems
may be significant, which could hinder their adoption.
As a result, and without the possibility to install new hydropower and nuclear units, existing nuclear reactors
are likely to be replaced by a combination of VRE backed by fossil-fired plants (principally gas plants and to alesser extent coal) in order to provide the necessary stability and flexibility to the system. Gas plants have also
the benefit to be relatively affordable for mid-merit and peak generation and have short construction leadtimes, if properly anticipated. This situation, however, will directly lead to an increase of CO2 emissions in the
short-term in the absence of further mitigation measures, as illustrated by the examples below. Energy
efficiency and system flexibility measures can be envisioned in parallel to reduce the reliance to fossil fuel inthe mid and longer run. The latter include interconnections, storage, demand-side response and sector

14.

The European Green Deal, for example, sets out a clear vision for the European Union (EU) to achieve
climate neutrality by 2050, with emission reductions of up to 50-55% by 2030 compared to 1990 levels(EC, 2019), an increase from the former goal of 40% More recently, countries such as China, Japan, Korea
and the United States have also pledged their intentions to reach carbon neutrality by 2050-2060.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

37

ENERGY POLICY ASPECTS

coupling approaches. Prospects of large-scale deployment of flexibility options, nevertheless, remain
uncertain with significant efforts still to be made in coming years to take some technologies to industrial-scale
deployment, for example large-scale flexibility from electric vehicles or synthetic fuels production (power-tohydrogen or power-to-gas) and storage (IEA, 2021a).
United States
In the state of New York, in the United States, nuclear units of Indian Point 2 and 3 where retired earlier thanplanned after a settlement agreement between Entergy Corp, operator of the reactors, the state of New York
(Larson, 2017) amid negative market prospects. The capacity gap was compensated with electricity generation
coming from the gas plants of Bayonne Energy Center II (120 MW), CPV Valley Energy Center (678 MW), andCricket Valley Energy Center (1 020 MW), built three years before in anticipation of the closure of Indian Point
units (EIA, 2021b). Figure 2.7 illustrates how gas plants take over nuclear generation soon after the reactors
ceased operations, as well as the subsequent increased in the carbon footprint of the New York State’s
electricity system.

Figure 2.7: Electric power generation by fuel, New York ISO, Jan 2017-Dec 2022
Indian Point 2 retires
April 30, 20209

Indian Point 3 retires
April 30, 2021

300

200

TWh

6

150
100

3

gCO2/kWh

250

50
0

NuclearRenewables

Natural gas
Avg. carbon footprintoct-22juil-22

avr-22oct-21janv-22juil-21

avr-21oct-20janv-21juil-20

avr-20oct-19janv-20juil-19

avr-19oct-18janv-19

juil-18

avr-18oct-17janv-18

juil-17

avr-17janv-170

Hydropower

Note: Carbon intensity has been computed using the mean values for each technology from Bruckner (2014).
Source: OECD/NEA using data from EIA (2021b).

In the state of California, in preparation for closure of the Diablo Canyon nuclear power plant units and ageing
gas-fired plants, the California Public Utilities Commission (CPUC) is working on a procurement order of 11.5
GW to be rolled out between 2023 and 2026. While significant efforts are being made to include only clean
energy sources in the proposal, the fossil fuel option is still open (Balamaran, 2021a; S&P Global, 2021).
Depending on the outcomes of further system adequacy analyses, new gas plants could be procured to replace
Diablo Canyon units hampering climate action.
Japan
Before the Fukushima accident, nuclear power accounted for 25% of the electricity generation in Japan. Afterthe accident, all reactors were shut down for safety inspections and upgrades to comply with new regulatory
requirements, leading to a surge of gas and coal consumption. As a result, annual carbon emissions in theelectricity sector immediately rose of around 25%. Since 2014, the carbon footprint of the Japanese electricity
sector is steadily declining thanks to the development of VRE and more reactors resuming operations. As of
2019, nevertheless, emissions were still higher than pre-Fukushima levels (IEA, 2021b).

38

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

Belgium
Nuclear power is an important part of the electricity mix in Belgium. In 2019, nuclear generation represented
nearly 50% of the total electricity of the country, and 70% of the total low-carbon electricity generation.
The federal government reconfirmed the nuclear phase-out in October 2020. Under current legal requirements
nuclear reactors in Belgium will cease operations between April 2022 and December 2025. However, thegovernment indicated that 2 GW of nuclear capacity may be needed beyond 2025 to ensure generation
adequacy.
The nuclear phase-out will have a large impact in the Belgian electricity system. In the short term, in order tomitigate electricity security risks, gas generation is expected to increase along with VRE. Consequently, carbon
emissions are estimated to grow 30% with gas representing a sizeable share of the electricity generation by
2030 and beyond, in particular if no additional policy efforts are undertaken (BFP, 2017; EEA, 2018).

Safety and performance
Nuclear power plants are assets in constant evolution. Most of the structures, systems andcomponents (SSCs) of a nuclear power plant are replaced as part of normal maintenanceprocedures and more extensive LTO refurbishment. In fact, regulatory frameworks in mostcountries impose periodic and LTO-specific safety reviews to assess if the plant complies with
its licensing basis during the initial design lifetime, as well as during the LTO period (seeChapter 5).
On the other hand, there are SSCs for which replacement can be considered unfeasible fortechnical and/or economic reasons. 15 Consequently, the ageing of these components will
ultimately limit the operation of the plant. Critical life-limiting components are typically thereactor pressure vessel (RPV) and concrete containment structure (NEA, 2012b), and these aresubject to specific ageing management programmes (see Chapter 3). Extensive research andoperating experience nonetheless support safe operation beyond 40 years (NEA, 2006, 2012b,
2015). In addition, global performance indicators suggest that older plants do not necessarily
face more operational issues as they can benefit from experienced teams and refinedorganisational procedures resulting from 40 years of operation (see Chapter 4).

Decommissioning, waste management and other environmental aspects
According to the European Joint Research Centre (JRC) (2021), there is an international scientificconsensus that nuclear energy does not do more harm to human health and environment thanother low-carbon technologies. This conclusion includes both radiological and non-radiologicalimpacts over the entire life cycle of a nuclear power plant, and thus the LTO period.
The decommissioning process is independent from the lifetime of the plant, meaning that
LTO will have a very limited impact on the technical aspects of decommissioning (NEA, 2016).
In addition, from an economic perspective, some financial benefits may arise from delaying
the decommissioning decision (see Box 6.1). 16
In terms of high-level waste (i.e. spent nuclear fuel, reprocessing), however, LTO willautomatically lead to additional quantities of nuclear waste, proportional to the duration of
LTO. 17 Such a situation would therefore require the availability of physical infrastructures tosafely store waste. Available solutions include interim or centralised wet storage in pools or

15.

That is, it would either present too great a technical challenge, and/or it would simply be too costly tobe justified.

16.

Assuming that the benefits outweigh potential cost escalations and inflation.

17.

After 40 years of operation, for example, adding 20 years of operations would increase the amount of
nuclear waste by roughly 50%.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

39

ENERGY POLICY ASPECTS

dry storage in casks, and these solutions can be implemented as part of the LTO programme. 18
In parallel, long-term disposal solutions such as deep geological repositories (DGRs) havemade significant progress in various countries. There is a strong, international and scientificconsensus that DGRs are a safe, appropriate and effective approach to the permanent disposalof high-level waste and spent nuclear fuel (NEA, 2020a; JRC, 2021). The first DGR to becommissioned will likely be in Finland, with operations beginning around 2023, but similar
projects in France and Sweden are well advanced.
Other environmental impacts of power generation activities include aspects such as air
pollution, land use, resource depletion and water use. As a carbon-free, energy-dense resource,
nuclear power performs well in terms of air pollution and land use, including via mining
activities (IAEA, 2018; NEA, 2018b; JRC, 2021). Similarly to carbon emissions, LTO offers theopportunity to efficiently manage these issues and extend the environmental benefits over time.
In terms of resource depletion, uranium reserve-to-production ratios remain high withvalues typically around 100 years or more (NEA, 2018b, 2020b). 19 LTO of the existing global fleet
will therefore not represent a threat in terms of resource depletion. In parallel, progresscontinues to be made in minimising the environmental impacts of mining activities (NEA,
2020b). Beyond uranium resources, the demand for critical minerals (e.g. copper, lithium, silicon,rare earths) is set to rise during the energy transition given the higher material intensity of alow-carbon mix that relies on high shares of VRE. 20 (IEA, 2021c) As for carbon emissions, LTO
can be regarded as a lever to manage critical resource supply issues, as well as to limit thepotential environmental impacts associated with increased mining activities (Beylot et al., 2020).
Moreover, the life cycle impacts per GWh of generated electricity originating from concrete,steel and other building materials used in the construction of a plant, from construction anddecommissioning activities and from the decommissioning of waste will decrease substantiallyover time through LTO (JRC, 2021).
The water footprint is also a growing concern, especially in light of heatwaves and draught
episodes that are expected to be more frequent and intense in the years to come. In general,
reactors in operation have been designed to adequately meet site-specific environmental andwater-cooling constraints. Technically, it is possible to increase the efficiency of the coolingsystems and adapt nuclear facilities to meet more stringent regulations and water footprint
limits, even during the LTO period (NEA, forthcoming).
Finally, in most legal and regulatory frameworks, environmental impact assessments arepart of the LTO-review process. These assessments are designed to ensure that nuclear power
plants continue to operate in a safe and environmentally friendly manner (NEA, 2019a).

2.2.2.Economics and affordability of the electricity supply
Having access to cheap and stable sources of electricity is key to the development andcompetitiveness of each country. At the same time, national realities differ, leading to a myriad of
possible ways to combine technologies so as to build a low-cost electricity system. Carbon
constraints are nevertheless reducing the choice of technologies available to provide an affordable,
low-carbon system. Meeting ambitious emission reduction targets require the deployment of
mature and proven low-carbon solutions, including nuclear power. For those countries choosing
LTO of existing nuclear assets, it is essential for policymakers to have a clear understanding of theimplications of this decision from a full cost perspective. This full cost perspective entails looking
beyond individual plants and technologies and considering system and socio-economic
considerations. To do so, the different regulations and policy measures in place should properly
recognise the value that LTO can provide to the electricity system while sustaining affordability
over time. Residual risk, however, will always remain, and governments are best placed to absorb
them and create the appropriate context for optimal industrial performance, and therefore lower
costs.

40

18.

Storage pools have been characterised as a mature technology based on over 50 years of operating
experience and dry cask storage systems as passive systems with over 30 years of operating experience(NEA, 2020c).

19.

Taking into account conventional resources that are not exploitable under current uranium prices,proven reserves could satisfy more than two centuries at current consumption levels.

20.

Four-fold under SDS and six-fold under NZE, compared to 2020 levels.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

Technology costs and market issues
The full costs of electricity provision typically fall into three categories: plant-level costs, systemcosts and social costs (NEA, 2018a). LTO, similar to other power generation technologies,
contribute to each category.
From a plant-level cost perspective, the results of the present study confirm that LTO of theexisting nuclear fleet is one of the most cost-competitive options on the basis of the levelised
cost of electricity (LCOE) in many regions, with overnight construction costs (OCC) ranging from
USD 450-950/kWe and a LCOE between of USD 25-50/MWh (see Chapter 6). Similar results arereported in IEA (2019) and IEA/NEA (2020) (see Figure 2.8).

Figure 2.8: LCOE by technology, 2025
250

LCOE [USD/MWh]

200
150
100

Fossil fueltechnologies

Gas (CCGT, CCUS)

Coal (CCUS)

Lignite (CCUS)

Biomass

Geothermal

Hydro (run of river, >= 5MW)

Hydro (reservoir, >= 5 MW)

Solar thermal (CSP)

Solar PV (residential)

Solar PV (commercial)

Solar PV (utility scale)

Offshore wind

Onshore wind (>= 1 MW)

Nuclear (LTO)

NuclearGas (CCGT)

Coal

0

Lignite50

Low-carbon technologies

Note: Values at 7% discount rate. Box plots indicate maximum, median and minimum values. Boxes indicate the central 50% of values(i.e. the second and third quartile).
USD/MWh = US dollars/megawatt hour; CCGT = combined cycle gas turbine; CCUS = carbon capture, use and storage.
Source: IEA/NEA, 2020

Despite these favourable cost trends, nuclear power plants are being retired earlier than
expected as a result of negative market prospects, especially in the United States. Fixed costs
remain high for licence extensions, which makes these assets particularly sensitive toavailability downturns and/or sustained, low electricity prices. In parallel, market conditions
have dramatically changed over the last decade with the irruption of higher shares of VRE,
underscoring the limits of current market designs to secure low-carbon capacity in the longterm. As a result, various regulations and support mechanisms cohabit within competitivemarkets to support the development of low-carbon technologies, and these could, theoretically,
be extended to LTO (see Chapter 6). This is the case, for instance, for zero emission credits in
the United States (see Box 6.5).
Beyond plant-level costs, system costs arise from the interaction of individual technologies
with the overall electricity infrastructure in order to meet demand at all times. With nuclear
capacity fading away without timely LTO decisions, and assuming that wind and solar power

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

41

ENERGY POLICY ASPECTS

are the main technologies being considered as a replacement for nuclear power, low-carbon
energy systems could be more expensive. Without the dispatchability attributes of nuclear
power, electricity systems could also be subject to higher strains (e.g. steeper and more frequent
ramps) and require grid reinforcement in order to accommodate higher peak loads from thehigher shares of nuclear power and VRE. As a result, electricity supply costs could be close to
USD 80 billion higher per year on average for advanced economies as a whole (IEA, 2019).
Additional quantitative evidence on the systems costs of electricity systems with shares ofnuclear power and VRE is provided in NEA (2019b). The extent of these effects may varydepending on the structure of the generating portfolio and the availability of flexibility resources,
for instance in the case of hydropower, interconnections and storage.
Finally, social costs quantify the impact of a generation technology on individual andcommunity well-being. This category covers a multitude of social and environmental costs,
involving local and regional air, water and soil pollution, climate change, the consequences ofmajor accidents, land use and resource depletion. While acknowledging the uncertainties
behind these full cost estimates, a comparison with the external costs of fossil fuel reveals thatthe benefits in terms of climate change and air pollution offered by nuclear power largely
outweigh the social costs (Burtraw et al., 2012; NEA, 2018b). LTO, alongside with other lowcarbon sources, is therefore an effective and predictable lever to manage and attenuate thenegative externalities of air pollution and climate change.

Insights on policy making and economic performance
Policy aspects and the economic performance of projects or industrial sectors are intimately
related, in particular if the socio-economic impacts at stake are high. The context under which
critical activities are executed thus takes on great importance and becomes a potential source ofpolicy risk – typically out of the reach of industrials – that can severely undermine the final
economic outcomes if not properly managed. This is the case for any major energy infrastructure
upgrade, including LTO programmes.
In order to address potential policy risks associated with licence extensions, long-term
industrial policies can be developed for a better risk allocation between the industry and thegovernment, while providing high levels of policy commitment and adequate regulations:42•

Policy commitment: governments are best placed to ensure the long-term stability,
visibility and planning that LTO activities require. These conditions are of utmost
importance for various reasons. First, most costs are fixed, meaning that any sudden
deviation from the initial strategy will come at a higher economic penalty. In addition,
longer amortisation periods and stable prices usually improve the profitability of LTO
investments. Second, meeting high safety standards requires continuous technicalassessments in co-ordination with regulators and across the entire value chain. These
activities are better performed under more predictable policies since any unexpectedchange could trigger significant amounts of rework and undermine the overall
economics (see Box 2.2 below).

•

Regulations: policymakers have various options to improve the economic performanceof a technology (or of the electricity system as whole) either affecting the costs, revenues
or both. The speed of deployment and potential impacts can also vary. For instance,
reviewing taxation regimes (lowering costs) and support mechanisms (guaranteeing
revenues) for a given technology are easy to do and can lead to rapid and effective results.
More structural market reforms, however, may require careful planning to avoid
undesirable distributional effects or public opposition, but the reward can be higher andmore noticeable in the long term (see Chapter 6). The resulting policies will certainly be
a combination of various measures tailored according to the specificities of the context
and various policy motivations in order to maximise the social benefits.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

Box 2.2: Policy uncertainty and nuclear powerindustry performance – The case of Belgium
In 2003, the “Progressive phase-out of nuclear power for electricity for industrial purposes” law was enacted in
Belgium, according to which construction of new reactors for the generation of electricity was banned. At thesame time, the remaining reactors would cease operations once the 40-year limit was reached. The first units
impacted by this law were Doel 1 and 2, and Tihange 1, all of which were to be shut down by 2015.
Despite this phase-out policy decision, the main Belgian utility, Electrabel, anticipated between 2009 and 2012
the safety LTO-review necessary to operate these plants beyond the 40-year threshold. Following regulatory
approval, received in 2012, the operator started to implement the necessary safety upgrades and plantenhancements at Tihange 1 and decided to start decommissioning work on Doel units 1 and 2.
The decommissioning plans for Doel units 1 and 2 were optimised in order to make the best use of the energy
in the fuel assemblies, whether in the core or in the storage pool, and to minimise the size of the fresh reloads
in the terminating fuel cycles. This required the implementation of a new fuel management strategy consistingof the design of a specific core loading for unit 2 that combined 2/3 of the irradiated assemblies of unit 1 with
1/3 of the counterparts of unit 2. This approach provided enough reactivity margins to run unit 2 at hot fullpower until the end of 2015, minimising overall fuel costs (see Figure 2.9). The approach of course required
specific safety studies to demonstrate that such unusual core loading met all the safety criteria.

Figure 2.9: Foreseen fuel management strategy for Doel units 1
and 2 in 2015 to meet 2003 Belgian phase-out law

Source: Courtesy of Electrabel.

When approaching 2015, it appeared that new VRE installed capacity was not enough to compensate for the
closure of the three nuclear units, giving rise to security and energy independence concerns. Consequently, in2014 the government reconsidered its initial phase-out decision and allowed Doel units 1 and 2 to operate
beyond 40 years until 2025. The law was finally amended in mid-2015.
However, from an industrial perspective, this political reversal implied a major redesign of the previous
decommissioning plans and fuel management strategy under a very challenging schedule. Unit 2 wasimmediately stopped in order to perform all of the necessary inspection and maintenance activities to safely
operate the plant beyond its initial term of termination. Further, with the fuel assemblies of unit 1 alreadyloaded in unit 2, a full new core had to be procured. Going back to the usual conditions also required fuelassemblies with very special characteristics and complex negotiations with suppliers, resulting in higher
overall fuel costs.
This case provides valuable insights into the actual technical and economic implications of performing nuclear
activities under uncertain conditions. While adjustments are possible, experience has shown that these are often
carried out in far from optimal conditions, potentially leading to additional costs that would have been avoided
with more anticipation and a long-term vision. The Belgium examples also indirectly illustrate how LTO canabsorb shortfalls in electricity supply if low-carbon capacity additions do not progress as initially planned.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

43

ENERGY POLICY ASPECTS

2.2.3.Security and reliability of the electricity supply
Security of electricity is at the heart of economic progress in modern societies. The COVID-19
pandemic has more recently illustrated the critical importance of having a reliable and robustelectricity system in order to ensure the smooth operation of economy-wide essential activities
and business continuity to limit economic losses.
The characteristics of a secure electricity supply may vary according to different stakeholders.
While the final consumers are essentially concerned about uninterrupted supply, transmission
system operators rely on robust methodologies and technical criteria. 21 The NEA report The
Security of Energy Supply and the Contribution of Nuclear Energy (2010) identifies three dimensions
relevant for policymakers when assessing the contribution of different technology options for the
security of supply:•

the physical availability of fuel and generating capacity (i.e. system adequacy) at all times;•

the ability of generating capacity to the smooth operation of the electricity system in thepresence of sudden shifts in demand, particularly during periods of peak demand;•the contribution of generation capacity to the stable economic behaviour of the electricity
system when supply is scarce.

These dimensions also cover different physical and temporal scales. For instance, in highlyinterconnected networks, security of supply concerns may be more adequately addressed in close
co-ordination with neighbouring countries, or even at the continental level. Accommodating
demand and price shifts are routine activities in modern electricity systems, but ensuring system
adequacy requires long-term planning and specific regulations. Nuclear power, and more
specifically LTO, performs well in all three of these dimensions.

Nuclear fuel and dispatchability attributes
In terms of fuel availability, nuclear fuel is an energy-dense resource, 22 which can be easily andsafely stored. In this sense, countries with nuclear power plants can secure strategic fuelstockpiles for several years of operation 23 improving overall fuel security and diversity. Asbaseload generators, nuclear reactors usually run without interruptions during cycles of
18-24 months between fuel loading outages. This results in average load factors of 85%. 24 The
dispatchability of nuclear power also contributes to the reliability and quality of the electricity
supply. As a manoeuvrable asset with a rotating mass, nuclear power plants can, for example,
provide ancillary services such as inertia, primary and secondary frequency control (low rapid
power variations ranging from 5 to 2% of the nominal power) and load following (slower power
variations of more than 50%), all while respecting technical and safety constraints (IEA, 2019;
NEA, 2012a). The body of knowledge surrounding flexible operations in considerable and future
innovations could also enhance flexibility attributes including non-electric applications (NREL,
2020) (see Chapter 6) These dispatchability attributes also have implications in terms of theeconomic behaviour of the system. The possibility to accommodate load fluctuations throughload following stabilises electricity prices, thus limiting the impact and occurrence of negative
prices (see Figure 2.10). These conditions also facilitate the integration of higher shares of VRE
at lower system costs while reducing the reliance on fossil-fired backup. With electricity
systems becoming more and more interconnected, these effects are becoming noticeable acrossa number of countries.

21.

22.
23.
24.

44

According to the electricity security standards of the French transmission system operator, ensuring
the perfect balance of supply and demand may require exceptional load shedding measures(e.g. interrupting the production of electro-intensive industries, reducing the voltage in the distribution
network, implementing rolling blackouts) on average for three hours per year (France Stratégie, 2021).
As an order magnitude, 1 tonne of natural uranium extracted for a PWR provides 10 000 times moreenergy than 1 tonne of oil or coal, and 1 000 cubic metres of natural gas (CEA, 2018).
For instance, it is estimated that France has enough nuclear fuel on its territory to secure three to five
years of full operation for the entire nuclear fleet (SFEN).
This value is also dependent on system constraints. In France, where the existing nuclear capacity
covers more than the baseload region in the load duration curve, capacity factors are at around 75%,
with reactors performing load following.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

Figure 2.10: Electricity generation mix in France between 27-29 March 2020
35

70 00030

60 00025
20

40 00040 GW

30 000

15

26 GW

30 GW

10
5

EUR/MWhMWh

50 0000

20 000-5

10 000

-10
-15

Wind

Solar

Nuclear

Hydro

Fossil fuels

21:00

18:00

15:00

12:00

09:00

06:00

03:00

00:00

21:00

18:00

15:00

12:00

09:00

06:00

03:00

00:00

21:00

18:00

15:00

12:00

09:00

06:00

03:00

00:00

0

Spot priceSource: OECD/NEA, using data from RTE (2021) and Nord Pool (2021).

Thanks to LTO, nuclear power can continue to offer its support to the security and reliabilityof the electricity supply at reasonable costs, all the while avoiding carbon emissions. Industrial
experience has furthermore shown that existing reactors can be retrofitted to improve theirmanoeuvrability capabilities. Operators undertaking major refurbishments for LTO may see
value in implementing additional plant enhancements to adapt the plants to a changing context,
while mutualising costs and licensing efforts. The associated technical requirements, as well as
the potential economic advantages of flexible operations during LTO, are further explored in
Chapters 3 and 6, respectively.

System adequacy considerations
Ensuring system adequacy (or the availability of physical generating capacity) is becoming a
critical issue in light of more ambitious emission targets, which will most likely require theclosure of dispatchable generators such as coal and gas plants. Nuclear phase-out policies may
also further reduce capacity margins. In some regions, the capability of the electricity system torespond to peak demand surges under extreme events (e.g. heat and cold waves) is already being
undermined and could worsen beyond the 2025 time frame in the absence of remediation action(see Box 2.3).
The installation of additional VRE capacity will certainly have a positive impact in terms of
the security of supply – especially if wind and solar power additions are combined– but theircontributions will be very limited given their low capacity credit. 25 The flexibility provided
through interconnectors could also be reduced, with various countries simultaneously phasingout dispatchable generators. Storage (e.g. batteries and long-term storage solutions), sector
coupling and other innovations are part of the solutions required to accommodate high sharesof VRE, but their large-scale deployment prospects remain uncertain.

25.

Capacity credits give an appreciation of how much a system operator can rely on a technology to meetpeak demand. On-shore and off-shore wind have capacity credits of around 10-20%, respectively, andsolar PV at 2%. The higher penetration level of VRE in the electricity system, the lower their capacity
credit is. This can be explained by the intrinsic variability of renewables and their high autocorrelation.
Conventional, dispatchable generators, on the other hand, have capacity credits of around 85%, similar
to their load factor (NEA, 2019; France Stratégie, 2021).

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

45

ENERGY POLICY ASPECTS

As long as uncertainty exists in relation to the transformation of the power system, realistic
and proven solutions need to be pursued as a technological hedge against such uncertainty.
Countries with nuclear reactors in operation can enhance electricity security by fostering adiversified low-carbon mix that benefits from the dispatchability of nuclear power through LTO(IEA, 2020f). Higher levels of cross-country co-ordination would also be beneficial. While some
initiatives exist, in the majority of cases capacity closures are largely decided in a unilateralmanner (see Box 2.3 below). These measures could be complemented with market regulations
that send the right price signals to support the construction of new capacity in the long term(see Chapter 6).

Box 2.3: Assessing reliability concerns in low-carbon electricity systems
The energy transition is profoundly transforming the electricity system. Significant amounts of fossil-fired,dispatchable generators (i.e. mainly coal plants) are being replaced by VRE additions. While necessary to
reduce emissions, these replacements could lead to capacity shortfalls in meeting peak demand, especially if
nuclear power is also removed from the grid. Achieving carbon emission reductions at the expense ofelectricity security is not a sustainable approach. Recent episodes of grid stress and capacity projections
underscore the impacts of deploying VRE without adequate planning and new measures, which are needed
to avoid rising reliability concerns.
California
The state of California in the United States is committed to achieving carbon neutrality by 2045. As a result,electricity generation from coal has already been completely abandoned and additions of solar PV have morethan doubled over the last five years. In 2019, solar and wind power represented around 21% of electricity
generation in California, with the remainder procured essentially from gas (43%), hydropower (19%), nuclear(8%) and geothermal power (5%) (EIA, 2021a). The rapid deployment of solar PV has strongly impacted theresidual load profile of dispatchable generators and increased flexibility needs. 26 When the sun sets, ramps ofaround 13 GW are required to rapidly compensate for the reduced generation of solar power (CAISO, 2016).
In August 2020, in the midst of a heat wave, the Californian grid operator, California ISO (CAISO), issued a “Stage
3 Electrical Emergency” and implemented load-shedding measures for several days to maintain grid reliability,
including through rolling blackouts that impacted around 200 000-250 000 consumers per hour. An ex-postroot cause analysis of the main reasons behind this event demonstrated that a lack of resource planning tokeep up with a changing electricity mix, exacerbated by excessive demand induced by the extreme heat wave
and some market practices, was the primary cause (Morehouse, 2021). In 2019, CAISO had already warned theCalifornia Public Utilities Commission (CPUC) of a capacity shortfall of 4.7 GW by 2022 (GTM, 2020). The CPUC
and CAISO are working in close co-ordination to install new capacity in 2021 and to increase resource adequacy
targets for specific hours of peak demand. CAISO is also expediting a stakeholder process that will allow it tomore accurately determine real time supply and demand during constrained conditions. In the short term,some of these measures may include further contracts for additional electricity generation with gas plants,
threatening the state’s clean energy goals (Balamaran, 2021b)
EuropeIn 2019, some European grid operators underscored increasing grid reliability risks in the years to come as
more countries were phasing-out dispatchable capacity, without consulting neighbouring countries, andrelying on more imports to compensate for the capacity loss (Reuters, 2019). As of 2020, there was around
240 GW of combined coal and nuclear capacity, representing 40% of dispatchable generation in Europe.
Projections based on stated policies show a 66% reduction in this capacity (160 GW) by 2040, which should becompensated by other resources. Assuming that nuclear energy remains at 2020 levels, the fall in capacity
could be limited to 45% (see Figure 2.11 below).

26.

46

Because of the particular form of residual demand (i.e. very low when solar panels are generating andrapidly increasing as the sun goes down), this phenomenon is typically known as the duck curve.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

A recent study from France Stratégie finds similar grid reliability concerns (France Stratégie, 2021) with
Belgium, France and Germany the countries impacted the most. All three countries foresee the phase-out of
nuclear capacity in the short term. According to France Stratégie (2021) estimates, Germany in particular would
not be able to meet peak demand by solely relying on dispatchable generation beyond 2025. France could
experience a similar situation by 2035 when around 12 nuclear reactors will be retired from the grid. The
European electricity network is more and more interconnected, and therefore interdependent. Structuraldecisions on the energy mix (e.g. capacity retirements), however, rely exclusively on national authorities andare still taken with limited co-ordination among EU member states. Initiatives such as the European Resource
Adequacy Assessment should help to collectively identify and address potential resource adequacy issues
while new co-ordination mechanisms at the European level are explored.

Figure 2.11: Evolution of nuclear and coal capacity in Europe
according to stated policies, 2040
300
250

GW

200
-160 GW

150
100
50
0
2020

2025

2030
Coal

2035

2040

Nuclear

Note: It is assumed that no additional investments in new nuclear build would take place by 2040.

2.2.4.The full value of the LTO option
While the consequences of current energy policies by 2030 may be known, it is more difficult
to elucidate what the optimal low-carbon energy system might look like in 2050, and the fulleconomic and social implications of such a system. Sizeable risks and unexpected costs exist
in any major energy transformation endeavour and should be acknowledged in existing energy
policy frameworks. Beyond the energy trilemma objectives (decarbonisation, affordability andsecurity of supply), issues such as time and technology maturity or choice are valuable
resources that will help to cope with unforeseen situations while increasing the chances ofsuccess for the different decarbonisation pathways. At the same time, it is important forpolicymakers to keep in mind that the technical and economic spillover of nuclear energy
could be useful in recovery times. Including the LTO option in policy frameworks can offer thefollowing additional benefits:•

Ensuring the availability of funding and infrastructure for decommissioning and waste
management activities: LTO can provide additional time to secure the necessary funding
for back-end activities, if necessary, while limiting the financial burden on operators inthe short term (see Box 2.4). The LTO period can be used to upgrade the waste
management infrastructure in order to perform back-end activities under optimal safety,
industrial and economic conditions.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

47

ENERGY POLICY ASPECTS

27.

48

•

Investment efficiency: The transition towards a low-carbon system will require themobilisation of massive amounts of capital in a relatively short period. Policymakers
should seize any opportunity to smooth these investments, while securing emission
targets and system affordability. The relatively low generation costs of LTO comparedto other low-carbon options can limit the overall, upfront financial burden of building
low-carbon systems and bring additional value by delaying and/or staggeringdecommissioning expenses over time. At the system level, additional savings in VRE
integration can be realised by prolonging the dispatchability of nuclear power throughLTO. These considerations are even more important in the post-COVID-19 era, wherein
LTO could be an effective measure to guarantee investment efficiency under severebudgetary constraints.

•

Risk management: When policies are designed, it is difficult to identify and properly
address all of the risks associated with a particular decarbonisation pathway. This iseven more the case with strengthened emission reduction targets since these targets
require that extensive economic, industrial and social transformations take placeacross shorter timelines. As illustrated in the different sections of this chapter,
multiple factors could impact emission trajectories, raise system costs and undermine
the reliability of the system, pushing governments to reconsider their initial plans (seeBox 2.2). Technical challenges remain in relation to the large-scale deployment offlexible solutions, such as long-term electricity storage, demand response and sector
coupling. In addition, in the absence of a co-ordinated approach, individual countries
do not have control over the decisions of neighbouring countries, adding more
uncertainty to the process. In this context, an enlarged technology portfolio combining
innovative and ready-to-deliver solutions that include LTO allows for greater flexibility
in energy planning so as to properly manage unexpected risks. In general, LTO emerges
as a well-suited solution to simultaneously tackle carbon emission reduction shortfalls,
affordability and reliability concerns.

•

Industrial development and innovation: The additional time provided by LTO can beused to optimise industrial plans, build supply chain capabilities in different sectors anddevelop new technologies. As indicated by (IEA, 2020b), more than 50% of thetechnologies necessary to reach carbon neutrality are still at the research anddevelopment stage or lack of the industrial maturity to be rolled out at scale. LTO couldin this way be considered as a bridging technology towards more disruptive innovations,or until some technologies become commercially viable.

•

Shovel-ready projects and jobs for recovery times: LTO projects face low construction andfinancing risks, representing a credible, shovel-ready option to support decarbonisation
strategies and boost economic recovery in the short term (IEA, 2020d). Its economic
potential, however, may be constrained by the limited number of ongoing projects, as wellas the dependence on regulatory approval. In terms of employment, nuclear sector salaries
are typically higher than for any other technologies (Oxford Economics, 2019), and an
important proportion of the jobs are local and long term. 27 Around 700-1 700 workers areneeded to run a nuclear site, depending on the number of units (NEA, 2018a).

Considering the entire life cycle of a nuclear power plant, these activities could last for over a century
in a given community.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

Box 2.4: Ensuring the adequacy of funding for decommissioning
and waste management activities through LTO – The case of Spain
According to the “polluter pays” principle, decommissioning and waste management costs (i.e. those related
to the back-end of the fuel cycle) are fully internalised, and operators must make annual contributions to
dedicated funds through an allocation of provisions or through specific fees levied from the operators’
revenues during operations of the plant. The amount of these annual contributions is calculated based on
estimates of back-end costs, which are periodically re-evaluated.
The aggregated value of these annual contributions combined with the accumulated return of the fund during
operations should, in theory, ensure the full coverage of initial decommissioning and waste management costestimations. In practice, these costs may be subjected to inflation, escalation, new regulations and otheruncertainties that can jeopardise their availability as the plant approaches the end of its operations.
In 2018, the Spanish Court of Auditors estimated that the gap in the funding of nuclear back-end activities wasaround EUR 3 billion. This amount represented several years of economic contributions from nuclear operators
under the 40-year nuclear power plant operation scenario contemplated in the 6th edition of the General
Radioactive Waste Plan approved in 2006.
The Spanish government, nuclear operators and Enresa initiated a series of discussions to determine a realistic
scenario to cover this funding gap. Based on the reference of 40-years of operations, a 60% increase of the fee
levied from nuclear operators would be necessary. In contrast, operations of 50 years (i.e. 10 years of LTO)
would lead to a 19% reduction of the fee and still meet funding needs (El Economista, 2019). Finally, in January
2020, a compromise was agreed among the involved parties on a scenario that set a 19% increase of this fee(from EUR 6.69/MWh to EUR 7.98/MWh) and a new average operating time for the Spanish nuclear fleet of 46
years (i.e. 6 years of LTO) instead of the initial 40-year reference. Enresa now expects to collect the necessary
funds by 2035, the same year during which the last Spanish reactor will be shut down.
The financial benefits associated with licence extensions in terms of decommissioning and waste management
trust funds are assessed in more detail in Box 6.2.

Key findings•

More than 30% of the existing nuclear fleet is already in LTO according to the regulations of different
countries. Most of these reactors are LWRs operating in Europe, Russia and the United States. With anaverage of 31 years, most of the world’s nuclear fleet will be confronted with LTO decisions in the next
decade. Assuming that most nuclear power plants are shut down after 40 years of operation, global
nuclear capacity could be halved by 2040.

•

The policy environment for LTO varies geographically. While most US states are supportive of licenceextensions, the context in Europe and Japan is more uncertain. Policy uncertainty can be an impediment
for the performance of nuclear activities, including LTO, in the best optimal conditions.

•

LTO performs well in every dimension of the energy trilemma: i) environmental protection, ii) affordability
and iii) security and reliability of the electricity supply). By avoiding around 1.6 Gt of CO2 emissions
annually, current nuclear capacity could help, along with new build, keep decarbonisation trajectories on
track by 2030. The role of 80-year licence extensions becomes particularly relevant beyond 2040 bridging
the gap to meet net-zero targets by 2050. At the same time, LTO remains one of the most competitive,
low-carbon options in many regions and can bring sizeable benefits in terms of VRE integration and social
costs. Potential security and reliability concerns resulting from the closure of significant amounts ofdispatchable fossil-fired generation could be mitigated with LTO of existing nuclear reactors.

•

The LTO option holds additional value for policymakers beyond the energy trilemma. The time, technicalmaturity and enlarged portfolio of technology options provided through LTO can make positive
contributions in terms of the adequacy of funding for back-end activities, investment efficiency, newtechnology development and overall risk management of ambitious decarbonisation pathways.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

49

ENERGY POLICY ASPECTS

References
Balamaran, K. (2021a), “CPUC ditches natural gas in 11.5 GW proposal but leaves door open for
future fossil fuel procurement”, Utility Dive, www.utilitydive.com/news/cpuc-ditchesnatural-gas-in-115-gw-proposal-but-leaves-door-open-for-futu/602336/.
Balaraman, K. (2021b), “Groups fear California blackout prevention plan could increase gas use,threaten climate goals”, Utility Dive, www.utilitydive.com/news/groups-fear-californiablackout-prevention-plan-could-increase-gas-use-thr/594237/.
Beylot, A. et al. (2020), “Mineral raw material requirements and associated climate-change
impacts of the French energy transition by 2050”, Journal of Cleaner Production, Vol. 208, pp.
1198-1205, www.sciencedirect.com/science/article/abs/pii/S0959652618331718.
BFP (2017), Le paysage energetique belge à l’horizon 2050 : Perspectives à politique inchangée, Bureau
Federal du Plan, Brussels, www.plan.be/uploaded/documents/201710270928090.For_Energy_2017_11531_F.pdf
Bruckner T. et al. (2014), “Energy Systems”, Climate Change 2014: Mitigation of Climate Change,
IPCC, Geneva, www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_chapter7.pdf.
Burtraw, D. et al. (2012), “The True Cost of Electric Power: An Inventory of Methodologies to
Support Future Decision making in Comparing the Cost and Competitiveness of Electricity
Generation Technologies”, Resources for the Future, Washington, DC, https://media.rff.org/
archive/files/sharepoint/WorkImages/Download/RFF-RptBurtrawKrupnick%20TrueCosts.pdf.
CAISO (2016), “What the duck curve tells us about managing the grid”, CAISO, Folsom,www.caiso.com/Documents/FlexibleResourcesHelpRenewables_FastFacts.pdf.
CEA (2018), Mémento sur l’Energie - Energy Handbook, CEA, Gif-sur-Yvette, www.cea.fr/multimedia/
Documents/publications/ouvrages/memento-energie-2018.pdf.
El economista (2019), ¿Cuánto costará desmantelar las centrales nucleares? No tendrá impacto para el
Estado, pero afectará a 7.000 empleos, www-eleconomista-es.cdn.ampproject.org/v/s/
www.eleconomista.es/noticias-amp/9776955/El-cierre-de-las-nucleares-y-la-gestion-desus-residuos-no-provocara-deficit-?amp_js_v=0.1.
EC (2019), The European Green Deal, European Commission, Brussels, https://ec.europa.eu/info/
sites/info/files/european-green-deal-communication_en.pdf
EC (2018), A Clean Planet for all: A European strategic long-term vision for a prosperous, modern,competitive and climate neutral economy, European Commission, Brussels, https://eurlex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52018DC0773&from=EN.
EEA (2018), Projections of greenhouse gas emissions by sources and removal by sinks: Information on
the assumptions, parameters, methods and model description, Reporting under Article 18 ofRegulation (EU) 2018/1999, Belgium Dataflows, European Environment Agency,
https://reportnet.europa.eu/public/country/BE.
EIA (2021a), California: State profile and energy estimate (database), www.eia.gov/state/?sid=CA(accessed on 29 June 2021).
EIA, (2021b), “New York’s Indian Point nuclear power plant closes after 59 years of operation”,
website, Energy Information Administration, www.powermag.com/deal-reached-topermanently-close-indian-point-nuclear-plant/.
France Stratégie (2021), Quelle sécurité d’approvisionnement électrique en Europe à horizon 2030,
République Française, Paris, www.strategie.gouv.fr/publications/securite-dapprovisionnementelectrique-europe-horizon-2030.
GTM (2020), “California’s Shift From Natural Gas to Solar Is Playing a Role in Rolling Blackout”,
Greentech Media, www.greentechmedia.com/articles/read/how-californias-shift-fromnatural-gas-to-solar-is-playing-a-role-in-rolling-blackouts.

50

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ENERGY POLICY ASPECTS

IAEA (2021), Power Reactor Information System (PRIS) (database), https://pris.iaea.org/PRIS/home.aspx(accessed on 28 June 2021).
IAEA, (2018), Climate Change and Nuclear Power, IAEA, Vienna, www-pub.iaea.org/MTCD/
Publications/PDF/CCNAP-2018_web.pdf.
IEA (2021a), Conditions and requirement for the technical feasibility of a power system with a high sharesof renewables in France towards 2050, IEA, Paris, www.iea.org/reports/conditions-andrequirements-for-the-technical-feasibility-of-a-power-system-with-a-high-share-ofrenewables-in-france-towards-2050.
IEA (2021b), Data & statistics (database), www.iea.org/statistics/ (accessed on 29 June 2021).
IEA (2021c), Japan 2021 Energy Policy Review, IEA, Paris, www.iea.org/reports/japan-2021.
IEA (2021d), The Role of Critical Minerals in Clean Energy Transitions, IEA, Paris, www.iea.org/
reports/the-role-of-critical-minerals-in-clean-energy-transitions.
IEA (2020a), Carbon intensity of electricity generation in selected regions in the Sustainable
Development Scenario, 2000-2040 (Data Release), IEA, Paris, www.iea.org/data-andstatistics/charts/carbon-intensity-of-electricity-generation-in-selected-regions-in-thesustainable-development-scenario-2000-2040.
IEA (2020b), Energy Technology Perspectives 2020, IEA, Paris, www.iea.org/reports/energytechnology-perspectives-2020.
IEA (2020c), European Union 2020: Energy Policy Review, IEA, Paris, www.iea.org/reports/europeanunion-2020.
IEA (2020d), Sustainable Recovery, World Energy Outlook Special Report, IEA, Paris, www.iea.org/
reports/sustainable-recovery.
IEA (2020e), “Nuclear Power” in Tracking Clean Energy Progress: Nuclear power, IEA, Paris,
www.iea.org/reports/nuclear-power.
IEA (2020f), Power Systems in Transition, IEA, Paris, www.iea.org/reports/power-systems-intransition/electricity-security-matters-more-than-ever.
IEA (2019), The Role of Nuclear Power in Clean Energy Systems, IEA, Paris, www.iea.org/reports/nuclearpower-in-a-clean-energy-system.
IEA/NEA, (2020), Projected Costs of Generating Electricity, 2020 Edition, OECD Publishing/IEA, Paris,
www.oecd-nea.org/jcms/pl_51110/projected-costs-of-generating-electricity-2020-edition.
IEA/NEA (2015), Technology Roadmap: Nuclear Energy, OECD Publishing/IEA, Paris, www.oecdnea.org/pub/techroadmap/techroadmap-2015.pdf.
JRC (2021), “Technical assessment of nuclear energy with respect to the ‘do not significant harm’criteria of Regulation (EU) 2020/852 (‘Taxonomy Regulation’)”, Joint Research Center,
Luxembourg, https://ec.europa.eu/info/sites/default/files/business_economy_euro/banking_and_finance/documents/210329-jrc-report-nuclear-energy-assessment_en.pdf.
Larson, A., (2017), “Deal Reached to Permanently Close Indian Point Nuclear Plant”, Powermag,
www.powermag.com/deal-reached-to-permanently-close-indian-point-nuclear-plant/.
Morehouse, C. (2021), California releases final root cause analysis of August rolling blackouts, Utility
Dive, www.utilitydive.com/news/california-releases-final-root-cause-analysis-of-augustrolling-blackouts/593436/.
NEA (forthcoming), Climate Change: Assessment of the Vulnerability of Nuclear Power Plants andApproaches for their Adaptation, OECD Publishing, Paris.
NEA (2020a), Management and Disposal of High-Level Radioactive Waste: Global Progress and Solutions,OECD Publishing, Paris, www.oecd-nea.org/rwm/pubs/2020/7532-dgr-geological-disposalradioactive-waste.pdf.
NEA (2020b), Uranium 2020: Resources, Production and Demand, OECD Publishing, Paris, www.oecdnea.org/jcms/pl_52718/uranium-2020-resources-production-and-demand.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

51

ENERGY POLICY ASPECTSNEA (2019a), Legal Frameworks for Long-Term Operation of Nuclear Power Reactors, OECD Publishing,Paris, www.oecd-nea.org/law/pubs/2019/7504-long-term-operation-npp.pdf.
NEA (2019b), The Cost of Decarbonisation: System costs with high shares of nuclear and renewables,
OECD Publishing, Paris, www.oecd-nea.org/ndd/pubs/2019/7299-system-costs.pdf.
NEA (2018a) Measuring Employment Generated by the Nuclear Power Sector, OECD Publishing, Paris,
www.oecd-nea.org/ndd/pubs/2018/7204-employment-nps.pdf.
NEA (2018b), The Full Costs of Electricity Provision, OECD Publishing, Paris, www.oecdnea.org/ndd/pubs/2018/7298-full-costs-2018.pdf.
NEA (2016), Costs of Decommissioning Nuclear Power Plants, OECD Publishing, Paris, www.oecdnea.org/ndd/pubs/2016/7201-costs-decom-npp.pdf.
NEA (2015), “Questionnaire on Long-Term Operation of Commercial Nuclear Power Plants”,
OECD Publishing, Paris, www.oecd-nea.org/nsd/docs/2015/csni-r2015-13.pdf.
NEA (2012a), Nuclear Energy and Renewables, OECD
nea.org/ndd/pubs/2012/7056-system-effects.pdf.

Publishing,Paris,

www.oecd-

NEA, (2012b), The Economics of Long-term Operation of Nuclear Power Plants, OECD Publishing, Paris,
www.oecd-nea.org/ndd/reports/2012/7054-long-term-operation-npps.pdf.
NEA (2010), The Security of Energy Supply and the Contribution of Nuclear Energy, OECD Publishing,Paris, www.oecd-nea.org/ndd/pubs/2010/6358-security-energy-sup.pdf.
NEA (2006), Nuclear Power Plant Life Management and Longer-term Operation, OECD Publishing, Paris,
www.oecd-nea.org/ndd/pubs/2006/6105-npp-life-management.pdf.
NEI (2020), “Nuclear by the Numbers”, NEI, Washington, DC, www.nei.org/resources/factsheets/nuclear-by-the-numbers.
NEI (2018), “Nuclear Costs in Context”, NEI, Washington, DC, www.nei.org/CorporateSite/media/filefolder/resources/reports-and-briefs/nuclear-costs-context-201810.pdf.
Nord Pool (2021), Market data (database), www.nordpoolgroup.com/Market-data1/ - /nordic/map(accessed on 2 August 2020).
NRC (2021a), Public meeting on potential technical issues and guidance document development
related to license renewal that would authorize operation for up to 100 years, NRC, Rockville,
www.nrc.gov/pmns/mtg?do=details&Code=20201407.
NRC (2021b), “Status of Subsequent License Renewal Applications”, website, NRC, Rockville,
www.nrc.gov/reactors/operating/licensing/renewal/subsequent-license-renewal.html.
NREL (2020), Flexible Nuclear Energy for Clean Energy Systems, Technical report, National
Renewable Energy Laboratory, Denver, www.cleanenergyministerial.org/sites/default/files/2020-10/CEM%20Flexible%20Nuclear%20Energy%20for%20Clean%20Energy%20
Systems_0.pdf.
Oxford Economics (2019), Nuclear power pays: Assessing the trends in electric power generation
employment and wages, Oxford Economics, New York.
Reuters (2019), “France's RTE urges policymakers to talk energy mix with EU peers”,
www.reuters.com/article/us-europe-electricity-france/frances-rte-urges-policymakersto-talk-energy-mix-with-eu-peers-idUSKCN1S12ET.
RTE (2021), éCO2mix (database), www.rte-france.com/eco2mix (accessed on 2 August 2020).
Sfen, “L’Uranium dans le monde”, www.sfen.org/energie-nucleaire/panorama-nucleaire/uraniummonde.
S&P Global Platts (2021), “California regulators order 11.5 GW of clean energy additions as
nuclear exit looms”, Nucleonics Week, Vol. 62, No. 26.
WNN (2019), “Tepco declares Fukushima Daini for decommissioning”, https://world-nuclearnews.org/Articles/Tepco-declares-Fukushima-Daini-for-decommissioning.

52

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

REGULATORY AND LEGAL ASPECTS

3. Regulatory and legal aspects

A necessary condition of any long-term operation (LTO) programme is to have authorisation orapproval 1 from a governmental body (i.e. the government/ministry or regulatory body) tocontinue operations. How the LTO of nuclear power reactors is integrated into nuclear
regulations and the associated review process varies from one country to another. An LTOreview process, although not necessarily an LTO-specific review process, is always required,and in most cases its scope is not limited to safety aspects. At the same time, this process canresult in new safety requirements that need to be fulfilled by nuclear operators and can,ultimately, affect the economics of LTO. The objective of the present chapter is to provide
additional information about the intersection of nuclear regulations with the technical andeconomic aspects of LTO.
This chapter builds on the outcomes of three previous NEA publications:•“The Economics of Long-Term Operation of Nuclear Power Plants” (NEA, 2012): This study
provides technical information on the safety requirements and approaches for LTO, inparticular the necessary post-Fukushima upgrades, which are still relevant today.

•“Legal Frameworks for Long-Term Operation of Nuclear Power Reactors” (NEA, 2019): This study
is based on a survey covering 80% of reactors in operation worldwide, with the reportproviding unique insights into laws, regulations and policies for LTO, including countryspecific reports.

•“Unlocking Reductions in the Construction Costs of Nuclear: A Practical Guide for Stakeholders”(NEA, 2020): Some of the conclusions drawn in this report on the economics of nuclear
regulation are also applicable to the case of LTO.

3.1. LTO in nuclear regulations
According to the IAEA (2018), LTO is “operation beyond an established time frame […] justified
by safety assessment … [which] may take place within a broader regulatory process […]” (IAEA,2018). This definition contains two terms that are key to understanding how regulators interpret
LTO and when potential technical and economic implications of the regulatory process for LTO
may arise:•

Established time frame: First, it is necessary to define an initial period during which a
nuclear power plant is allowed and expected to operate in safe conditions. This timeframe corresponds to the authorisation term for nuclear operations 2 (i.e. operating
licence), which in turn is typically defined using initial design assumptions.

•

Safety assessment: second, in order to continue operations after a certain time frame,
the licensee must undergo a comprehensive safety assessment to verify that the plant
will continue to meet regulatory requirements. New safety requirements – specific to
LTO or not – can often be imposed as a result of the safety assessment. While the safetyassessment is a critical regulatory step in LTO, the broader term “LTO-review process”

1.

The survey carried out in NEA (2019) revealed that, depending on the country, regulators employ
different words to refer to the same or very similar concept to LTO. The present report will use as muchas possible the generic legal terms defined in the Chapter 1 of NEA (2019).

2.

For the sake of simplicity, referred to as the “authorisation term” in the remainder of this report.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

53

REGULATORY AND LEGAL ASPECTS

will be used in the present chapter because it encompasses safety considerations andother aspects that are an integral part of the LTO evaluation, such as: environmental
impact assessments, transboundary notifications, the provision of information, andpublic consultation and participation.
After the LTO-review process, regulators may authorise a given nuclear power plant tooperate over a new time frame known as the LTO period (see Figure 3.1). The next sections inthis chapter provide a more detailed picture of the regulatory frameworks that have been
adopted in different countries based on the concepts of “authorisation term” and “LTO-review
process”. This approach is consistent with that used in previous NEA reports (2012; 2019) andcovers most of the key regulatory aspects for LTO.

Figure 3.1: Generic definition of LTO
Initial design lifetime

Operating within initial design lifetime

Long-term operation

Licensee:preparation of the LTO
documentation andtechnical studies
Regulator:
LTO review process

3.1.1.Insights on the initial authorisation term
The development of a nuclear programme in a given country is accompanied by several
strategic decisions that will have important implications in the long-term governance of thistechnology. From a regulatory point of view, the choice of the length of the authorisation termof a nuclear power plant is one of these decisions. An overview of the different authorisation
terms in various selected countries is provided in Table 3.1.
Typically, there are two types of authorisation terms: a specific, time-limited term, or anindefinite duration. Most countries use a specific, time-limited authorisation term 3 of 30 or
40 years. This duration is usually aligned with the initial design life of the reactor design.
The initial design life (or initial design lifetime) corresponds to “the period of time during
which a facility or component is expected to perform according to the technical specifications
to which it was produced” (IAEA, 2019). At the plant level, the Western European Nuclear
Regulators Association (WENRA) defines the initial design lifetime of a nuclear power plant as
the “the minimal value of lifetimes of all its non-replaceable structures, systems andcomponents” (WENRA 2011). As described in Chapter 3, there are few, non-replaceable
components in a nuclear power plant (e.g. the reactor pressure vessel and containmentbuilding). Moreover, the original design lifetime does not represent a technical limit inhibiting

3.

54

Of the countries responding to the NEA (2019) survey, 60% provided specific, time-limited authorisation
terms, while 40% provided an indefinite duration authorisation.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

REGULATORY AND LEGAL ASPECTS

operations since, from a safety perspective, there may be no real cliff edge effect 4 resulting fromageing when a nuclear power plant operates longer than the initial design lifetime (WENRA,
2011).
For this reason, the regulatory provisions of countries with specific, time-limited
authorisation terms foresee longer operating time frames via a specific authorisation for LTO. The
decision is granted after assessing the capability of a given plant to comply with the applicablesafety requirements over the LTO period (i.e. safety aspects of the LTO-review process). The length
usually considered for the LTO authorisation term is 10-20 years. In most cases, there is no limit
in the number of renewals of the LTO authorisation. 5
On the other hand, there are some countries that have adopted an indefinite or open-ended
authorisation for nuclear operations. In these countries, the definition of LTO, built on thenotion of the initial design lifetime, is not so relevant. 6 A nuclear power plant subjected to thistype of licence term can operate as long as it complies with the applicable regulatory
requirements, without any time limitation. The initial design lifetime of the plant thus becomesa sort of technical input to anticipate and inform the regulatory process. According to thecountries surveyed in NEA (2019), no specific authorisation for LTO is required with an indefinite
licence term.
Overall, the overview of the authorisation term adopted in different countries confirms that:i) the original design lifetime is not used to set the ultimate operating lifetime of nuclear power
plants; and ii) laws or regulations stating that nuclear reactors are not allowed to operate
beyond an ultimate operating lifetime are also rare. In fact, most laws or regulations provide forindefinite terms or allow for unlimited licence extensions.

Table 3.1: Overview of the authorisation term
for nuclear operations in selected countries
Country

Term type

Initial term
length(generally)

Type ofreactor

Notes on the initial term Term lengthfor LTO
length(generally)

Notes on the term lengthfor LTO

Argentina

Specific

10 years

PHWRs

Initial design life ofreactors is approximately
30 years.

10 years

LTO programme is designed
to allow another 25-30 years.

Belgium

Indefinite

Indefinite

PWRs

Initial design life ofreactors is 40 years.

10 yearsThree nuclear powerreactors were allowed togenerate electricity for ten
additional years.

CanadaSpecific

10 years

PHWRs

Determined on a case-by- 10 years
case basis; the initialdesign life of reactors isapproximately 30 years.

Refurbishment process canenable LTO of a reactor forseveral decades(e.g. another 30 years).

Czech
Republic

Indefinite

Indefinite

PWRs

Initial design life ofreactors is approximately
30 years.

No limit on operation aslong as the reactor
continues to meet its safety
obligations subject tocontinuous safetyassessment, a special safetyassessment and PSRs,
among other requirements.

4.

5.
6.

Indefinite

An instance of severely abnormal plant behaviour caused by an abrupt transition from one plant status
to another following a small deviation in a plant parameter, thus giving rise to a sudden large variationin plant conditions in response to a small variation in input.
The exceptions include countries such as Hungary, Japan and Slovenia where the nuclear power plant
operation lifetime (initial authorisation term plus LTO period) is limited to 60 years.
WENRA (2011) indicates that, in general, the initial design lifetime of some non-replaceable components(e.g. pressure vessel) may no longer be relevant as actual plant operations and conditions, as well as
current knowledge about ageing phenomena, provide a more accurate prediction of the ultimate usefullife of these types of components.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

55

REGULATORY AND LEGAL ASPECTS

Table 3.2: Overview of the authorisation term
for nuclear operations in selected countries (cont’d)Country

Term type

Initial term
length(generally)

Type ofreactor

Notes on the initial
term length

Term lengthfor LTO(generally)

Notes on the term lengthfor LTO

FinlandSpecific

30 or 40
years

PWRs and
BWRs

Determined on a caseby-case basis, usuallybased on the initialdesign life of reactors.

Case-by-casebasis (inpractice, 20
years).

No limit on the number ofrenewals.

FranceIndefinite

Indefinite

PWRs

Initial design hypothesis
for certain equipment is
40 years.

Indefinite

No limit on operation aslong as it fulfils its safety
obligation, as reviewed
during decennial, periodic
reviews.

Hungary

Specific

30 years

PWRs

Based on initial design
life of reactors.

20 years

Only one licence extension
allowed.

Japan

Specific

40 years

PWRs andBWRs--

20 years

Only one renewal allowed.

Korea

Specific30, 40 or 60
years

PWRs and
PHWRs

Based on initial design
life of reactors.

10 years

No limit on the number ofrenewals.

Netherlands

Indefinite

Indefinite

PWR

Initial design life of thereactor is 40 years.

Determinedon a case-bycase basis.

Operation beyond the 40year technical design life
specified in the safety
report required an updateof this safety report, which
also required anamendment of theoperating licence. The
licence remained indefinite
although the reactor’s
technical design life was
extended for an additional
20 years.

Romania

Specific

30 years

PHWRs

Based on the initialdesign life of reactors
and other factors.

Determinedon a case-bycase basis.

No limit on the number ofrenewals.

RussiaSpecific

30 years

PWRs,
LWGRs and
FBRs

Determined on a caseby-case basis according
to the initial design life of
the reactors and otherfactors.

Determinedon a case-bycase basis.

No limit on the number ofrenewals.

SlovakRepublic

Indefinite

Indefinite

PWRs

--

Indefinite

No limit on operation aslong as the reactor fulfils its
safety obligations, as
reviewed during decennial
PSRs.

Slovenia

Specific

40 years

PWR

Based on the design lifeof reactors.

10 years

Only 2 licence extensions
allowed (for a total of 20
years).

Spain

Specific

10 years

PWRs and
BWR

Determined on a caseby-case basis; the initialdesign life of reactors isapproximately 40 years.

10 years

Determined on a case-bycase basis.

SwedenIndefinite

Indefinite

PWRs and
BWRs

The initial design life ofreactors is 40 years.

Indefinite

No limit on operation aslong as the reactor fulfils its
safety requirements, as
reviewed during decennial
PSRs.

56

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

REGULATORY AND LEGAL ASPECTS

Table 3.3: Overview of the authorisation term
for nuclear operations in selected countries (cont’d)Country

Term type

Initial term
length(generally)

Type ofreactor

Notes on the initial
term length

Term lengthfor LTO(generally)

Notes on the term lengthfor LTO

Switzerland

Indefinite

Indefinite

PWRs and
BWRs--

Indefinite

No limit on operation aslong as the reactor fulfils its
safety obligations;operation past 40 years
requires proof of safety for
LTO and a decennial PSR.

UkraineSpecific

30 years

PWRs

Based on the initialdesign life of reactors.

10-20 years

No limit on the number oflicence extensions.

UnitedKingdom

Indefinite

Indefinite

AGRs and
PWR--

Indefinite

No limit on operation aslong as the reactor fulfils its
safety obligations,
including a decennial PSR.

United StatesSpecific

40 years

PWRs andBWRs--

20 years

No limit on the number ofrenewals.

Notes: Pressurised water reactors (PWRs), boiling water reactors (BWRs), pressurised heavy water reactors (PHWRs), advanced gas reactors (AGRs),
light water graphite reactors (LWGRs) and fast breeder reactors (FBRs). PSR = periodic safety review.
Source: NEA (2019).

3.1.2.The LTO-review process
Approach
Two main regulatory approaches have traditionally been identified for the LTO-review process:i) licence renewal (LR); and ii) periodic safety review (PSR) (NEA, 2012). The primary difference
between the two processes lies in how often the authorisation or approval to continue nuclear
operations is renewed. LR is directly linked to the use of a specific, time-limited authorisation.
At the end of the term, (i.e. typically corresponding to the end of the initial design lifetime)
operators must apply to the competent authority for a licence renewal and provide all thenecessary technical evidence that the plant will continue to comply with the licensing basis
during LTO. Under a PSR approach, the authorisation or approval to operate is granted based on
the outcome of safety evaluations carried out periodically, typically every ten years. Bothapproaches are part of the broader regulatory process that generally allow safety improvements
on a continuous basis, based on set criteria, and regardless of the LTO dimension.
Actual regulatory practice shows that most countries rely on the principles of the PSR, withsome countries adopting features from both approaches (NEA, 2012; 2019). In fact, NEA (2019)emphasises that the LR and/or PSR dichotomy is perhaps not the most appropriate distinction
to use. A new distinction could necessary since LR is a specific approach used by only three
responding countries. Approaches for the LTO-review process instead fall into three distinct
categories (see Figure 3.2):

7.

•

PSR-based review process;•

PSR with an LTO-specific review process; 7•

LTO-specific process.

“Because not all LTO-specific review processes (whether linked or not to a PSR) result in a licensing action,
it is more precise to speak generically of an LTO-specific review process, which may or may not be linked
to the decennial PSR, within which an LTO-specific licensing process is a subcategory.” (NEA, 2019)

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

57

REGULATORY AND LEGAL ASPECTS

According to this new categorisation, around 45% of the responding countries in NEA (2019)
undertake a PSR process combined with LTO-specific considerations. This hybrid approachtakes advantage of the efficiency associated with traditional PSR processes while allowing someadjustments to assess specific LTO-related issues (e.g. ageing).
The authority responsible for performing the LTO-review process (either PSR-based, LTOspecific process or both) is, in most countries, the regulatory body. In some cases, this process
is carried out in co-ordination with technical support organisations (TSOs). 8 Regulatory bodies
are also responsible in most cases for approving or authorising LTO. In some countries, the final
LTO approval or authorisation is granted either by a ministry or the government on either thebinding opinion of the regulatory body or based on the regulatory body’s LTO review (NEA, 2019).

Figure 3.2: LTO approval approaches

Source: NEA (2019).

Safety assessment and its technical implications
During any LTO-review process, and independent of the approach undertaken, regulators will
evaluate – using the inputs provided by the licensees and their own verifications – if a given
plant will comply with applicable safety requirement during the LTO period. 9 The scope of theregulatory safety review for LTO focuses on the following topics (NEA, 2012):•

ageing issues;•

safety and security improvements based on operating experience, the latest knowledgeof the technology, new safety standards and other emerging issues.

Ageing issues require a comprehensive evaluation of the actual conditions of the plant inorder to identify the most critical ageing-related phenomena during the foreseen LTO period.
While the main ageing mechanisms are generally common across all nuclear power plants,
there can be specific concerns depending on the type of design, and the operational history andexperience of the plant. By means of time limited ageing analyses (TLAAs), operators are able
extrapolate the impact of ageing mechanisms to assess operational margins. Some issues will
require specific ageing management programmes (AMPs) to ensure that the concerned
structures, systems and components (SSCs) perform as expected during LTO (Chapter 3).

58

8.

Depending on the country, the TSO is either an external body or is integrated within the regulatory
body.

9.

This is the most fundamental principle for all regulators (NEA, 2012) and operators.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

REGULATORY AND LEGAL ASPECTS

At the same time, original plant design deficiencies may be revealed through operating
experience (both in a given plant and internationally 10 ) or when compared with recent
knowledge and technology developments, and new emerging issues. All of these aspects are
considered by regulators during the LTO-review process and can lead to the introduction of
new safety and security requirements with their associated design modifications andinvestments. It is important to underline, however, that these new requirements are notnecessarily related to LTO and can be simply the result of a continuous safety improvement
logic. In fact, most of the regulatory frameworks have additional processes to introduce newsafety requirements outside of the LTO-review process (NEA, 2019).
One clear example of safety improvements is the introduction of post-Fukushima measures
to enhance the protection of existing nuclear power plants against external hazards. Some of theplant modifications and upgrades for severe accident management following the Fukushima
accident are illustrated in Box 3.1. Other emerging issues involve the revision of cybersecurity
guidelines for the utilisation of digital instrumentation and controls (I&C) (NRC, 2020a), as well as
the surveillance of climate-related events, such as heatwaves. 11 All operating nuclear power
plants are potentially concerned by these regulations either as part of, or outside of, the LTOreview process depending on the regulatory framework. This is particularly the case for postFukushima measures (see Box 3.1). Additionally, operators can opt for the implementation of
additional plant enhancements on a voluntary basis as part of LTO (e.g. power uprates). In general,these types of plant retrofits require an update to the licensing basis and thus a specific review toobtain regulatory approval.
Lastly, the scope of the regulatory safety review for LTO is not the same across plants andcountries, for various reasons. First, LTO ageing issues may vary depending on the condition of
the plant, operational history and past investments. Second, LTO-specific provisions can change
depending on regulatory frameworks. Third, additional reviews may be required to evaluate thesafety impacts of specific plant enhancements. All these aspects explain, to some extent, thedifferences in the LTO costs observed across plants and countries (see Chapter 6).

Box 3.1: Examples of post-Fukushima safety measures
After the Fukushima accident in 2011, many countries with operating nuclear power plants initiatedcomprehensive risk and safety assessments to evaluate the ability of plants to withstand site-specific, extreme
natural hazards that could potentially lead to severe accidents across several units. This work was performed
under regulatory oversight and in parallel to other international initiatives led by the NEA and IAEA. The studies
concluded that, in general, existing nuclear power plants have satisfactory safety levels against external
hazards and did not require immediate shutdown (NEA, 2012). The lessons from these evaluations revealed,
however, areas in need of safety improvements, and new regulatory guidelines were introduced in existing
frameworks in order to increase the robustness of nuclear power plants under extreme scenarios.
Post-Fukushima measures involve safety upgrades against extreme events and their combined effects toenhance mitigation capabilities for station blackout and the loss of ultimate heat sink, affecting the reactor
and the spent fuel storage pools. Such measures would need to be evaluated on a case-by-case basis, as not
all plants are equally exposed to the risks associated with external hazards. As a result, some plants could
require extensive plant modifications, involving the installation of new fixed equipment on-site, as well asorganisational improvements in terms of severe accident management and emergency preparedness. The
implementation of such measures could take a considerable amount of time, which may necessitate specificplanning and prioritisation of measures in co-ordination with regulators (see the French case below). PostFukushima safety requirements are already an integral part of existing regulations, meaning that any plant,
independently of its age or its intention to seek LTO authorisation or approval, should perform the necessary
safety upgrades. At the same time, the evaluation and implementation of post-Fukushima measures could bepart of an LTO-review process (particularly in the case of major safety upgrades) in order to take advantage of
economies of scale and potential efficiency gains on both the regulator and licensee side.

10. As described in Chapter 4, nuclear power plants are part of a governance model that enables operating
experience to be shared among operators around the world (e.g. WANO).
11. In France, since the heat wave episode of 2003, the capability of nuclear power plants to withstandextreme heat conditions has been continuously monitored by the regulator (IRSN, 2020) and evaluatedas part of decennial PSRs (Vicaud, 2019).
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

59

REGULATORY AND LEGAL ASPECTS

United States
As part of safety enhancements envisaged after the Fukushima accident, the US Nuclear Regulatory Commission(NRC) adopted the industry’s proposed safety strategy called “Diverse and Flexible Mitigation Capability” or FLEX
(NRC, 2020b).
Before the Fukushima accident, defence-in-depth levels 12 required protective measures for plant equipment
based on design-basis external events, as well as certain coping capabilities to prevent fuel damage in the caseof station blackout (SBO). In order to mitigate the potential consequences of nuclear accidents, nuclear power
plants also had severe accident management guidelines (SAMGs) and emergency response plans. The
introduction of the FLEX strategy would increase the level of defence in depth in a nuclear power plant in caseof beyond-design-basis external events (BDBEEs) that could simultaneously lead to the loss of external power
and ultimate heat sink. These higher defence-in-depth levels are achieved via:•

The use of portable equipment that provides a means to obtain power and water so as to maintain andrestore safety functions for all of the reactors at the site. This equipment includes portable pumps,
generators, batteries and battery chargers, compressors, hoses, couplings, tools, debris clearing
equipment, temporary flood protection equipment, and other supporting equipment or tools.

•

Reasonable staging and protection of portable equipment from BDBEEs applicable to a given site inorder to provide assurance that the equipment would be deployable after such an event.

•

Development of procedures and guidance to implement FLEX strategies and to improve existingprocedures to cope with BDBEEs.

•

Programmatic controls that ensure the continued viability and reliability of FLEX strategies. To doso, standards are established for quality, maintenance, testing of FLEX equipment, configuration andmanagement, and periodic training of personnel (NEI, 2016).

The implementation of FLEX follows a systematic approach that assesses the vulnerability of plants against
BDBEEs. The initial coping capabilities of a plant relying on already installed equipment are first determined
before transitioning to on-site FLEX equipment and additional off-site support at the regional level. Thisapproach is consistent with the NRC’s guidance on mitigation strategies for BDBEEs (NRC, 2017).
FranceBetween 2012 and 2014, the French Nuclear Safety Authority, ASN, issued new safety requirements and plantmodifications to be implemented at each of the 19 French nuclear power plants, based on lessons learnt fromthe Fukushima accident (ASN, 2014). These measures were the result of complementary safety assessments
carried out by the ASN with a strong focus on BDBEEs not properly covered by the safety standards available
before the accident. The main, post-Fukushima safety provisions included:•

Definition of new “hard core” safety measures for severe accidents: These measures would rely on
existing SSCs in nuclear power plants, and new SSCs built redundantly, whenever possible, as independent
systems to ensure ultimate power generation, cooling capabilities and accident management. Specific “hardcore” plant modifications involved the installation of ultimate diesel generators, ultimate heat sink,
additional water inventories and cooling circuits for both the primary circuit and spent fuel storage pools, acomplementary control room for “hard core” systems and regional response centres.

•

Establishment of a specialised force of fast response (FARN): Since 2016, four FARN units are operationalat the Civaux, Dampierre, Paluel and Bugey nuclear power plants. This special force can be mobilised at any
French nuclear power plant in less than 24 hours, and the force is specifically trained to restore power watersupplies using portable equipment in the case of a major accident. Regular training and emergency
simulations are performed at particular sites in order to sustain and improve FARN capabilities (EDF, 2020).

Different phases have been considered for the implementation of post-Fukushima measures in France. The
deployment of FLEX strategies (i.e. availability of portable equipment) and the establishment of FARN took
place between 2012 and 2016. The plant modifications associated with “hard core” safety measures will be
performed progressively by 2030, as part of the ongoing French LTO programme called “Grand Carénage”(i.e. the “Major Refit”).

12. Prevention, control and mitigation measures for nuclear accidents.

60

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

REGULATORY AND LEGAL ASPECTS

Environmental impact assessment and transboundary notifications
While denominations may vary in different countries, an environmental impact assessment(EIA) is broadly defined as a tool to assess the impacts of a specific project or activity on theenvironment, which typically includes the preparation of specific documentation, consultations
with members of the public and evaluations by decision-making authorities, which are
expected to integrate the results of assessments in the decisions. 13 In most countries, applicablenational, regional or international legal frameworks clearly require that an EIA is carried out
prior to the initial licensing of nuclear facilities, including nuclear power plants.
There is, however, significant legal uncertainty in many countries regarding whether an EIA
is required before a nuclear power reactor enters the stage of LTO, as part of an LTO-related
review (NEA, 2012; 2019). From the 20 countries surveyed in NEA (2019), 65% reported requiring
an environmental review as part of the LTO-related review, and 35% indicated no suchrequirement. However, the survey noted that the extent of such environmental reviews differs
and may not always amount to a full-fledged EIA or the equivalent. 14
In addition, many national legal frameworks provide for an obligation to notify and consult
the authorities of other countries whose environment may be affected by a project or activities aspart of their EIA requirements – a process commonly referred to as “transboundary EIA”. The
primary source of this obligation is found in the Convention on Environmental Impact Assessment
in a Transboundary Context (Espoo Convention), 15 which counts 45 parties within the United
Nations Economic Commission for Europe (UNECE) region, including the EU and its member states.
The issue concerning the applicability of the Espoo Convention to the LTO of nuclear power plants
has been the subject of significant review at national and international levels for over a decade. 16
With a view to clarify this situation, and notably to assist the Convention’s Implementation
Committee in its review of several LTO cases, 17 the Meeting of the Parties to the Espoo Convention
endorsed in 2020 the “Guidance on the applicability of the [Espoo] Convention to the lifetime
extension of nuclear power plants”. 18 This guidance provides and elaborates on the criteria
according to which the Espoo Convention may or may not apply to LTO of nuclear power plants,

13. See, for example, Article 1(2)(g) of Directive 2011/92/EU of the European Parliament and of the Councilof 13 December 2011 on the assessment of the effects of certain public and private projects on theenvironment, as amended by the Directive 2014/52/EU of the European Parliament and of the Councilof 16 April 2014, OJ L 124 (25 April 2014) (EIA Directive). In the field of nuclear energy, an EIA may include
all or some of the following issues: uranium fuel cycle impacts, waste management, surface water
quality, aquatic ecology, groundwater use and quality, terrestrial resources, threatened or endangered
species, air quality, land use, human health, socio-economics, postulated accidents, decommissioning
and environmental justice (NEA, 2012).
14. Country specificities include, but are not limited to, the body responsible for performing the EIA, thescope of the EIA, the need to systematically perform a full EIA, or perform one just in the case of major
plant modifications, and whether the EIA is formally linked to LTO or not (NEA, 2019).
15. Convention on Environmental Impact Assessment in a Transboundary Context (1991), 1989 UNTS 310,
entered into force 10 September 1997 (Espoo Convention).
16. In 2011, an NGO introduced a communication before the Espoo Convention Implementation Committee
alleging that Ukraine had breached its obligations under the Espoo Convention regarding the LTO of
the Rivne nuclear power plant. This case was reviewed by the Implementation Committee and, in 2014,
the Meeting of the Parties to the Espoo Convention endorsed its findings and recommendations that atransboundary EIA should have been carried out prior to this specific licence extension. See UNECE(2014), “Decisions adopted by the Meeting of the Parties to the Convention”, “Decision VI/2, Review ofcompliance with the Convention”, ECE/MP.EIA/20.Add.1 – ECE/MP.EIA/SEA/4.Add.1, Meeting of theParties to the Convention on its sixth session and of the Meeting of the Parties to the Convention serving
as the Meeting of the Parties to the Protocol on its second session, Geneva, 2-5 June 2014, p. 14.
17. At the time of the drafting of the present report, there were five LTO-related cases pending before theEspoo Convention Implementation Committee, under references EIA/IC/INFO/15, EIA/IC/INFO/18,
EIA/IC/INFO/19, EIA/IC/INFO/20 and EIA/IC/INFO/28.
18. UNECE (2020), “Guidance on the applicability of the Convention to the lifetime extension of nuclear
power plants”, ECE/MP.EIA/2020/9, Meeting of the Parties to the Convention on Environmental Impact
Assessment in a Transboundary Context, Vilnius, 8-11 December 2020.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

61

REGULATORY AND LEGAL ASPECTS

acknowledging variations in the legal frameworks of parties to the convention. In this regard, theguidance recognises that “as there is no one-size-fits-all approach, when assessing possible casesof lifetime extension, a case-by-case determination through the consideration of the principles
and factors laid down in the guidance is recommended” (UNECE, 2020). It should also be notedthat the obligation to carry out an EIA, including transboundary consultations, was also subject tolegal review under EU law. In particular, the Court of Justice of the European Union rendered apreliminary ruling in July 2019 concluding that a specific national law enabling LTO of a specificnuclear power plant had been adopted in breach of EU law as a result of the absence of apreliminary EIA. 19 In that instance, the court considered that the LTO project, which included
major works intended to modernise the concerned nuclear power plant, “must be found to be ofa scale that is comparable, in terms of the risk of environmental effects, to that when those power
stations were first put into service”. 20
These cases illustrate some of the legal uncertainties surrounding LTO-related processes anddecisions, but also the trend of increasing requirements applicable to such decisions in terms ofenvironmental reviews. Operators should take in account these uncertainties early in the LTO
programme in order to minimise the exposure to legal risks that could impact LTO.

Provision of information and public consultation and participation
Public interest in LTO projects is high, and it is generally considered desirable for the regulatory
frameworks to consider legal provisions that would make the information of the LTO reviews
available whenever possible (NEA, 2012). Among the various legal instruments dealing withpublic access to environmental information (including nuclear safety-related information), theConvention on Access to Information, Public Participation in Decision-making and Access toJustice in Environmental Matters (Aarhus Convention) 21 establishes requirements 22 regarding:•access to environmental information held by public authorities upon request from amember of the public;•collection and dissemination of environmental information by public authorities in theabsence of a request.

Similar provisions are found in the EU secondary legislation, mainly in the Directive on
Public Access to Environmental Information. 23 While these legal instruments are not specific tonuclear energy nor to LTO, most of the responding countries that took part in the NEA (2019)study indicated that they include in their regulatory frameworks specific provisions on thedissemination of information to the public as part of the LTO-review process, or they makeinformation available to the public on request. Some specific exemptions limit publicaccessibility to confidential information that would inter alia adversely affect public security orcommercial interests.
In addition to legal requirements related to public access to environmental information, mostcountries’ legal frameworks include requirements that public authorities provide members of the
public with an opportunity to participate in decision-making processes for a wide range of nuclear,energy-related activities. In this regard, Article 6 of the Aarhus Convention sets out the legal
requirement that public authorities provide for a public participation procedure in decision
making for activities that may significantly affect the environment, including those related to

19. Court of Justice of the European Union, Judgment of 29 July 2019, Inter-Environnement Wallonie ASBL
and Bond Beter Leemilieu Vlaanderen ASBL v. Conseil des ministres, C-411/17, EU:C:2019:622.
20. Ibid. paragraph 79.
21. The Convention on Access to Information, Public Participation in Decision-making and Access to Justicein Environmental Matters (1998), 2161 UNTS 450, entered into force on 30 October 2001 (Aarhus
Convention).
22. See UNECE (2014), The Aarhus Convention: An Implementation Guide, 2nd edition, United Nations,Geneva, pp. 75-117.
23. Directive 2003/4/EC of the European Parliament and of the Council of 28 January 2003 on public accessto environmental information and repealing Council Directive 90/313/EEC, OJ L 041 (14 February 2003)(Directive on Public Access to Environmental Information).

62

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

REGULATORY AND LEGAL ASPECTS

nuclear power plants. In the context of LTO, Article 6(10) of the Aarhus Convention provides thatthe requirements for public participation in the initial decision-making procedure must be appliedmutatis mutandis whenever a public authority “reconsiders or updates the operating conditions” ofa concerned activity. In line with the findings of NEA (2012), NEA (2019) revealed contrasted
requirements regarding public participation as part of the LTO-review process among the different
countries consulted. Most of the countries reported having legal requirements to engage with the
public in various forms (e.g. hearings, comments) as part of their LTO-review process andindicated that due account was taken of comments received in the final decision. On the other
hand, eight countries reported no specific legal requirements for public consultation in the LTOreview process, primarily because of the absence of a formal and dedicated decision-making
procedure for LTO in their respective domestic laws.
The aforementioned report also concluded that in the majority of instances, the body incharge of ensuring public access to environmental information (either upon request or
through dissemination) and responsible for public participation is the decision-making publicauthority (e.g. the nuclear regulatory authority, another environmental public authority or
the government). However, some countries reported that under their national legal
frameworks the licensee is responsible for these activities either alone or in collaboration withthe decision-making authorities.

3.2. Regulation and LTO economics
Interaction between nuclear regulations and economics usually receives limited coverage, but
its analysis is necessary to have a complete picture of the economic performance of nuclear
power, including during LTO. In general, regulations, as is the case for any other economic
activity, tend to increase costs. These additional costs, however, should be regarded as the priceto pay to reduce the externalities associated with nuclear power, and thus maximise social
benefits. Theoretically, the regulatory optimum in economic terms is achieved when themarginal cost of protection equates to the marginal social benefits of the harm avoided. In
practice, this is more difficult to achieve given the high uncertainties associated with both themarginal costs of regulatory practices and the benefits of the risks avoided (Lévêque, 2014).
Nuclear regulations can impact the economics of LTO in two principal ways. First, theintroduction of new regulations once the LTO project has already been launched can provoke
delays and productivity downturns. This is particularly detrimental for the on-site works
because of the presence of significant fixed-cost equipment and manpower. Second, regulatorychanges can lead to plant retrofits and the installation of new SSCs. This is the case, for instance,for post-Fukushima safety improvements, which can represent up to 20-25% of the overnight
costs for the refurbishment needed for LTO of a plant 24 (see Box 3.1).
NEA (2020) proposes some principles to enhance regulatory interactions withoutcompromising safety and environmental standards. They are supported by actual past andrecent experience in nuclear constructions. Two of these principles are particularly importantfor LTO:

24•

Ensure regulatory stability and predictability: The adoption of new rules has to be
anticipated and planned well in advance in order to avoid costly retroactive projectchanges and rework, particularly with ongoing on-site work. The new safety standards
pursued by regulators should be clear and adequately translated into technicalspecifications so as to facilitate subsequent engineering studies and design modifications.

•

Avoid misinterpretation of safety requirements: Linked with the principle ofpredictability, poorly interpreted requirements resulting from a lack of communication
among regulators and licensees can lead to unnecessary and dispersed engineering
efforts with limited added safety benefits.

These are generic orders of magnitude that could vary considerably depending on plant conditions at
the moment of initiating the LTO programme.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

63

REGULATORY AND LEGAL ASPECTS

For the implementation of these principles, it is important that licensees adopt a proactiverole and work closely with regulators in developing clear and robust safety cases, and resolving
potential shortfalls when they arise. Governments can also foster enhanced regulatoryinteractions by aligning stakeholders’ interests and objectives while providing the necessarymeans to guarantee the independence and transparency of regulatory decisions.

Key findings•

The authorisation term and the LTO-review process are the main dimensions to be addressed whenassessing the regulatory aspects of LTO and their technical and economic implications.

•An overview of the authorisation terms adopted in different country regulations confirms that: i) the original
design lifetime is not used to set the ultimate operating time frame of nuclear power plants; and ii) laws or
regulations stating that nuclear reactors are not allowed to operate beyond an ultimate operating timeframe are also rare. In fact, most laws or regulations provide for indefinite terms or allow for unlimited licenceextensions.

•

In terms of safety, ageing issues and new safety and security requirements are the main areas of concern
for the LTO-review process. Safety improvements, however, may not necessarily be related to LTO but
may respond to a continuous safety improvement logic instead. In some cases, extensive plantmodifications may be required to comply with these new regulations (e.g. post-Fukushima measures).

•

Environmental impact assessments (EIA), including in a transboundary context, access to information andpublic participation are the main environmental, procedural aspects likely to be part of the LTO-review
process. Recent legal issues suggest that operators should consider associated legal provisions well inadvance of their LTO programmes in order to avoid potential concerns.

•

Regulations, as is the case for any other industrial activity, tend to increase the cost of nuclear power. PostFukushima measures, for instance, can represent around 20-25% of the overnight costs of LTO in somecases. Regulatory stability, predictability and a clear interpretation of safety requirements are also
important aspects that could impact the economic performance of LTO.

References
ASN (2014), Évaluations complémentaires de sûreté, Autorité de sûreté nucléaire, www.asn.fr/
Controler/Evaluations-complementaires-de-surete/Decisions-de-l-ASN/Decisions-2014-del-ASN.
EDF (2020), La force d’action rapide du nucléaire en exercice à Flamanville, www.edf.fr/groupeedf/nos-energies/carte-de-nos-implantations-industrielles-en-france/centrale-nucleairede-flamanville/actualites/la-force-d-action-rapide-du-nucleaire-en-exercice-a-flamanville.
IAEA (2019), IAEA Safety Glossary: Terminology Used in Nuclear Safety and Radiation Protection (2018
Edition), IAEA Doc. STI/PUB/1830, IAEA, Vienna, www-pub.iaea.org/MTCD/Publications/
PDF/PUB1830_web.pdf.
IAEA (2018), Ageing Management and Development of a Programme for Long Term Operation of Nuclear
Power Plants, IAEA Safety Standards, Specific Safety Guide No. SSG-48, IAEA, Vienna, wwwpub.iaea.org/MTCD/Publications/PDF/P1814_web.pdf.
IRSN (2020), Réacteurs électronucléaires – EDF – Grand Chaud – Retour d’expérience de la canicule del’été 2019, Avis IRSN no. 2020-00010, www.irsn.fr/FR/expertise/avis/2020/Documents/
janvier/Avis-IRSN-2020-00010_version-commentee_04032020.pdf.
Lévêque, F. (2014), The Economics and Uncertainties of Nuclear Power, Cambridge University Press,
Cambridge.

64

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

REGULATORY AND LEGAL ASPECTSNEA (2020), Unlocking Reductions in Construction Costs of Nuclear Power: A practical guide for stakeholders,OECD Publishing, Paris, www.oecd-nea.org/jcms/pl_30653/unlocking-reductions-in-theconstruction-costs-of-nuclear.
NEA (2019), Legal Frameworks for Long-Term Operation of Nuclear Power Reactors, OECD Publishing,Paris,
www.oecd-nea.org/jcms/pl_15154/legal-frameworks-for-long-term-operation-ofnuclear-power-reactors?details=true.
NEA (2012), The Economics of Long-Term Operation of Nuclear Power Plants, OECD Publishing, Paris,
www.oecd-nea.org/jcms/pl_14752.
NEI (2016), Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, NEI 12-06, Rev 4., NEI,
Washington, DC, www.nrc.gov/docs/ML1635/ML16354B421.pdf.
NRC (2020a), Digital Instrumentation and Controls Research, website, www.nrc.gov/aboutnrc/regulatory/research/digital.html (accessed on 29 June 2021).
NRC (2020b), FLEX Equipment – Maintain Key Functions with Backup and Redundant
Equipment, website, www.nrc.gov/reactors/operating/ops-experience/post-fukushimasafety-enhancements/flex-equipment.html (accessed on 29 June 2021).
NRC (2017), “Compliance with Order EA-12-O49, Order Modifying Licenses with Regard to
Requirements for Mitigation Strategies for Beyond-Design-Basis External Events, Revision
to JLD-ISG-2012-01”, www.nrc.gov/docs/ML1700/ML17005A188.pdf.
Vicaud, A., (2019), Eau, Centrales nucléaires et changement climatique, Revue Générale Nucléaire,
Sfen, Paris, https://rgn.publications.sfen.org/articles/rgn/abs/2019/01/rgn20191p38/rgn20
191p38.html?mb=0.
WENRA (2011), Pilot study on Long term operation (LTO) of nuclear power plants, WENRA Reactor
Harmonization Working Group, www.wenra.eu/sites/default/files/publications/ltoofnpps_1.pdf.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

65

Part 2:
Analysis of the internal capabilities of nuclear
power facilities for long-term operation

TECHNICAL ASPECTS

4. Technical aspects

Most nuclear reactors currently in operation are Generation II (Gen-II) reactors built in the 1970s
and 1980s, using the technical basis of the first prototypes and the materials performance inenergy systems available at that time. Commercial operating experience for Gen-II reactors wasthus limited and initial conservative assumptions were introduced in the design of criticalstructures, systems and components (SSCs), including significant safety margins to cope withpotential technical uncertainties. These criteria also served to develop regulatory requirements
so as to evaluate whether reactors were operating according to safety standards (i.e. licensing
basis) and be able to issue licences for new reactors.
As with any energy assets, materials ageing is a major concern for nuclear reactors,
potentially reducing their operating time frame. Since the start-up of the first Gen-II reactors,
extensive research has been carried out in order to identify and understand the main ageing
mechanisms and their associated kinetics under nominal and transient operating conditions.
Today, this research, combined with more than 13 500 1 years of nuclear operating experience
worldwide, constitutes solid technical evidence supporting the long-term operation (LTO) of
nuclear power plants. Technical uncertainties have been significantly reduced, and in mostcases original safety margins remain adequate for critical SSCs to be operated beyond theirinitial design lifetime. This knowledge base continues to be enriched with new national andinternational research activities, alongside growing operating experience.
LTO is therefore based on the technical evaluation that a nuclear power plant will comply witha given “licensing basis” during LTO. How this is demonstrated, and the technical basis needed,
will depend on regulatory strategies in individual countries. In general, LTO programmes are theresult of a systematic process mobilising the available technical evidence and best international
practices to assess current and projected plant conditions, and to identify the necessary actions
that will ensure that “important-to-safety” SSCs remain capable of performing their intended
functions during LTO. Periodic re-evaluations are also part of the process. Lastly, the role of LTO
refurbishments is not limited to ageing issues since nuclear operators often take the opportunity
to introduce additional plant enhancements to improve the overall safety, availability andeconomics of the plant.
Most of the technical evidence presented in this chapter is based on the operating experienceof light water reactors (LWRs). This technology is of the greater interest because it represents morethan 80% of the existing fleet. Specific aspects associated with pressurised heavy water reactors(PHWRs) and other reactor designs are also addressed in different sections of this chapter.

4.1. Materials challenges for LTO
The operating time frame for a nuclear power plant is ultimately governed by the ageing of
critical SSCs. Having an extensive understanding of the main ageing phenomena in different
conditions and nuclear systems is hence key to enabling LTO. In general, assessing material
degradation in nuclear systems is a complex endeavour, owing to the variety of materials 2

1.

An average of 31 years of operation for 444 operating reactors worldwide.

2.

There are around 25 different metal alloys within the primary and secondary systems of LWRs (Allenet al., 2010). Additional types of materials can be found in the containment building, instrumentation,and control equipment and cabling.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

69

TECHNICAL ASPECTS

and the unique combination of environmentally-induced stressors (high pressure andtemperature, intense neutron irradiation and chemical compatibility with the coolant), whichvary depending on their position in the system. After several decades of research andoperating experience, the main ageing mechanisms, stressors and related impacts in nuclear
systems are nevertheless well-known and understood today (NRC, 2006).
Of particular importance are non-replaceable components in nuclear systems. If thesecomponents fail, the nuclear power plant may be forced to cease operations, thus limiting the
lifetime of the plant. Such components are hence considered as “life-limiting”. While ageing
phenomena are observed in most nuclear systems regardless of the reactor type, some designs
have specific features and configurations that may slightly redefine the boundaries between
SSCs that are life-limiting and those that are replaceable, as well as alter the dynamics of ageing.
Moreover, the duration of particular plant conditions (e.g. full power versus cold shutdown) will
also influence final degradation levels. As knowledge on materials ageing in nuclear systems
progresses, some operators are envisaging longer operational time frames that could lead tonew materials challenges, which will need to be properly assessed.

4.1.1.Potential life-limiting components and associated ageing phenomena
In the past, life-limiting components of LWRs included the reactor pressure vessel (RPV), vesselinternals, steam generators, main pumps, cables and the concrete structures (NEA, 2000).
Technical advances and new engineering techniques have resulted in the re-classification ofcomponents that were initially considered non-replaceable, with significant industrial experiencedemonstrating that steam generators and vessel internals can be replaced (IAEA, 2008a).
Currently, all of the components of LWRs can be replaced, except perhaps 3 the RPV andsome containment structures (NEA, 2006, 2012b). Nevertheless, economics plays an importantrole in the decision-making process to replace some of these components. The economic
attractiveness of a major refurbishment increases with the size of the reactor and the remaining
operating time. As a plant ages, the remainder of the operating time frame may be too short toensure recovery of the investment in heavy equipment and components. Market conditions andfuture electricity price projections can also condition the final outcome. Some RPV internals andcabling are typically some of the components that could be considered life-limiting, or not,depending on economic considerations 4.
Based on this evidence, the following SSCs may become life-limiting:•

RPV (LWRs);•

reactor coolant system piping, welds and core internals (LWRs, PHWRs);•

large, civil and concrete structures, such as the containment building (LWRs, PHWRs);•

large sections of the plant’s electrical cable system (LWRs, PHWR).

Reactor pressure vessel (LWRs)
RPVs are fabricated by welding together 20 cm-thick ring forgings of bainitic, low alloy and plaincarbon steels. 5 RPV ageing occurs as a result of microstructural changes in materials due to both
thermal and irradiation exposure; the latter being the most marked and a major life-limiting factor.
Low-alloy steels show reduced toughness at low temperatures. While the onset of reduced
ductility is initially below temperatures of operational concern, irradiation induces a high densityof nanoscale defects and the formation of precipitates, which impede dislocation motion, leading

70

3.

Studies have demonstrated the technical feasibility of replacing the RPV in BWRs (Mizutani, et al., 2001).

4.

The type of technico-economic analysis, for example, behind some of the early plant closures, as reported
in Box 1.1.

5.

The typical composition is 1-2% manganese (Mn), 0.5-1% nickel (Ni), ~0.5% molybdenum (Mo) and 0.150.4% silicon (Si) (Zinkle, Was, 2013).

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

to a hardening and embrittlement of these types of materials. Consequently, the yield andultimate strengths of the RPV walls increases, with a corresponding decrease in materials ductility
and resistance to flaw propagation (fracture toughness). The toughness at all temperatures istherefore reduced with the shift from ductile to brittle transition temperature (DBTT) 6 to higher
temperatures (see Figure 4.1). The shift of the DBTT (or ∆DBTT) is thus important because it limits
the pressure and temperature conditions to which the reactor pressure boundary systems can be
exposed, which consequently reduces the margins, particularly during heat up and cool down
cycles 7 and those related to pressurised thermal shock (PTS) conditions. 8 Under PTS conditions,the resulting loss of fracture resistance can accelerate the propagation of a critical-size flaw
through the embrittled wall, jeopardising the integrity of the RPV (NEA, 2012).
It appears that the impact of irradiation is strongly dependent on the chemical compositionof the vessel materials (e.g. copper [Cu], sulphur [S], phosphorus [P] and nickel [Ni]) and isparticularly sensitive to Cu content. Welds and heat affected zones (HAZ) are also relatively
more sensitive to radiation exposure than the base metal resulting from potential variations incomposition and microstructures during their execution. Embrittlement is significantly acute in
the “beltline” region (and associated welds and HAZs) corresponding to the region surrounding
the active height of the core.

Energy Absorbed (J)Figure 4.1: Illustration of the impact of irradiation on fracture
toughness margins in the inner wall of an RPV

-200

∆DBTT

Margins

-150

-100

-50

0

50

100

150

200

250

300

Temperature (°C)
IrradiatedUnirradiatedTransientApproaches to RPV ageing management use surveillance capsules containing samples ofthe vessel materials and associated welds that are strategically placed inside the vessel inorder to accumulate an accelerated dose similar to the vessel itself, or even greater. 9 These
capsules are periodically removed and the contents tested to monitor changes in materials
toughness within temperature ranges that are relevant to reactor service (i.e. heat up and cool
down transients) and potential emergency conditions. The results from these tests also serve
to develop and calibrate embrittlement trend models that predict vessel material properties,
including the crucial changes in toughness expected with longer lifetime service. These
activities are complemented with in-service inspection of most irradiated zones in the vessel

6.

This phenomenon is also referred to in the literature as reference temperature for nil ductility transition.

7.

During the start-up or shutdown of the reactor.

8.

PTS conditions arise from certain low-probability accidental scenarios (e.g. loss of coolant), potentiallyinvolving the injection of cold water or overpressure at low temperature.

9.

Depending on their position in the vessel, these specimens can be exposed to a neutron fluence four times
higher than the inner wall, which enables the prediction of mechanical properties beyond 40 years.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

71

TECHNICAL ASPECTS(i.e. beltline region) using non-destructive evaluation (NDE) techniques to detect flaws and/or
follow their evolution in size through the wall. 10 The process is fully automated with robotic
ultrasonic and gamma radiography testing machines that are capable of scanning the RPV
inner wall and of identifying flaws with high accuracy within regions of 125 mm2 or less
(Benhamou, Vidard, 2019). Several strategies can also be envisaged to mitigate embrittlementon RPV walls and remediate ageing effects (see Box 4.1 below).
Additional degradation phenomena that have been observed in RPV structures involved
corrosion phenomena, in particular stress corrosion cracking of Ni-based alloys present in thevessel penetrations (i.e. upper and lower head), combined with boric acid corrosion of lowcarbon steels. The most notable example of such a degradation mode was observed in thepressure vessel head of the Davis Besse reactor in 2002 (Zinkle, Was, 2013). This type ofdegradation mechanism is not usually life-limiting as pressure vessel heads can be easily
replaced during normal outages.

Box 4.1: Overview on RPV embrittlement mitigation strategies in LWRs
In order to mitigate RPV embrittlement, it is necessary to limit the exposure of the inner wall to irradiation. Thisis possible with the adoption of core designs that minimise neutron leakage. For example, with in-out fuelloading patterns, depleted (and thus more absorbent) fuel assemblies are placed in the periphery, acting as ashield against excessive neutron irradiation while improving overall fuel economics. Shielding effects can befurther enhanced by inserting highly absorbent Hafnium control rods in some peripheral fuel assemblies.
Other mitigation approaches foresee higher temperatures of the water in the emergency safety injection tolimit PTS risks in accidental conditions. The effect of all these measures on the evolution of the fluenceobserved by the RPV wall is illustrated in Figure 4.2.
Figure 4.2: Qualitative impact of different RPV embrittlement
mitigation measures

Fluence (n/cm2)

Design fluence
Optimised fuel loading
Optimised fuel loading + Hafnium control rods

0

10

20

30

40

50

60

70

Years

10. Most of the cracks found in the beltline region are shallow cracks ranging from 10 to 15 mm (Chen etal., 2014).

72

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

Reactor coolant system piping welds and core internals (LWRs, PHWRs)
The reactor vessel internals and most of the piping in LWR systems are usually fabricated fromhigh-alloy 11 austenitic stainless steel of grades 304, 316 and 347. These materials are selected
because of their desirable combinations of moderate strength, good corrosion resistance, andexcellent ductility and toughness. They are also easily formable into the plate, forgings, bolts
and tubular structures needed to fabricate some of the components. The “austenitic” structureof these materials means that they are more highly resistant to embrittlement than the bainitic
steels used for the higher stress-bearing and larger pressure-retaining components, such as thereactor pressure vessel, vessel heads, steam generators and pressurisers.
Different ageing mechanisms can be identified depending on the type of stainless steel
and its position in the primary circuit. Pressure vessel internals perform in an environment
characterised by elevated temperatures 12 and very intense neutron fields. Austenitic stainlesssteels are susceptible to irradiation-induced – but not thermally-induced – hardening and lossof toughness. However, this occurs at much higher irradiation fluences (around 1 000 times)
compared to low-alloy steels. The higher irradiation regimes also induce void swelling andirradiation creep that can cause undesirable stress relaxation. Combined with corrosion, it
can lead to irradiation-assisted corrosion cracking (IASCC). This phenomenon is a genericchallenge across all LWRs, observed in at least four reactor designs, eleven different alloys
and dozens of components (Zinkle, Was, 2013), but it does not represent a safety-relatedpressure boundary issue. 13 Potential mitigation measures include chemistry control, upflow
conversion to reduce mechanical solicitations in the core baffle and better cooling of the bolts
via holes in the former (Pokor et al., 2018). Vessel internals (including bolts and springs) can
also be replaced (IAEA, 2008a).
IASCC is not an issue for primary circuit piping, since the dose is much lower than onreactor vessel internals. Piping and some internals structures are often fabricated by welding
and a cast form of the austenitic stainless steels (CASS). These materials can be susceptible
to loss of toughness on extended thermal exposure (i.e. thermal ageing), even in lowirradiation environments. This greater susceptibility is derived from the structure of welds
and castings, which contain some volume fraction of ferrite phase that is responsible for thesevere irradiation and thermal embrittlement found in low-alloy and plain-carbon steels. This
phase is intentionally induced to assist in the production of crack free welds and castings. In
general, added susceptibility is managed and controlled by limiting the amount of thedeleterious “ferrite” phase in the weld and casting structures. Welds are also periodicallyinspected using several NDE techniques and can also be repaired, depending on their level ofdegradation.

Large, civil and concrete structures (LWRs, PHWRs)
Large, civil and concrete structures are of high priority when assessing nuclear power plant
ageing. In fact, most of the concrete systems are not replaceable, and in some cases, they cannot
be directly accessed for inspection (US DOE, 2012). Among all large, civil and concrete structures
present in nuclear power plants, those that are critical for LTO include the containment building,
biological shielding and spent fuel pools.
The containment building of a nuclear power plant represents the third barrier (after the
nuclear steam supply system and the fuel) against radioactive releases. It consists of thick,reinforced concrete structures using low-carbon rebar, which are post-tensioned with tendons toprovide additional tensile strength in case of overpressure during severe accidents. 14 Additional

11. High-alloy steels have a higher content of chromium and nickel compared to low-alloy steels.
12. Temperatures typically range from 288°C in a boiling water reactor (BWR) and up to 360°C in a PWR (insome locations with high gamma heating).
13. For instance, in case of baffle bolt degradation, only peripheral fuel assemblies could be impacted.
14. The differences in containments across reactor designs are essentially driven by the internal pressureof the primary circuit, which will determine the ultimate internal energy that the containments mustwithstand in case of an accident.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

73

TECHNICAL ASPECTS

leak tightness can be obtained with a steel liner. The containment building structures are exposedto three main ageing phenomena:•

Concrete drying: As concrete ages, it loses its water content. This induces macrostructuralchanges such as shrinkage, creep (especially in post-stressed concrete structures) andincreased permeability, leading to a reduction of the leak tightness of the containment overtime. Given the low tensile strength and lack of ductility of concrete, these changes will
also lead to the formation of cracks. Cracking occurs virtually in all concrete structures andcan never be completely eliminated.

•

Rebar corrosion: In general, the high alkaline conditions provided by concrete inhibits
corrosion of the reinforcing steel in the concrete systems. However, the increased
permeability and microcracking over time may favour carbonation 15 processes, thepresence of chloride ions and moisture that ultimately can result in corrosion. Corrosion
is also the main ageing issue of the steel liner (low carbon steel) and follows similar
patterns as those for conventional reinforcing steels. Typically, liner steels are coated (i.e.
zinc-rich primer with polyamide epoxy or modified phenolic coatings) to provide higher
resistance against corrosion.

•

Alkali-silica reaction (ASR) 16: ASR occurs when reactive silica in the aggregate reacts
with hydroxyl ions (-OH) and alkali ions (Na+, K+) in the concrete pore solution. When
this concrete is in contact with water, a gel can form around the aggregate that induces
tensile stresses on the surrounding concrete, which then results in microcracking. Witha sufficient amount of internal expansion and tensile stresses, the result is patterncracking (see Figure 4.3) that could lead to complete destruction of the concrete (NRC,
1996). Pop-outs and glassy appearing seepage of varying compositions can also appear(see Figure 4.3). Since no means of preventing chemical attack existed before the 1990s,
the past few years have been characterised by intense research efforts to provide thetechnical basis, the necessary early detection tools and the ageing management
measures for ASR-affected concrete structures (EPRI, 2015, 2017).

Figure 4.3: Example of pattern cracking and pop-outs of ASR-affected concrete

Source: Baills-Barraco, Courtois, 2018, courtesy of EDF.

15. Calcium hydroxide is converted to calcium carbonate (calcite).
16. Other, less frequent forms of chemical attack in nuclear power plant containment buildings involve
internal sulphate (-SO2) reactions with similar consequences as those of ASR.

74

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

Overall, the above ageing patterns are slow and are not necessarily detrimental to the pointthat reinforced concrete would not be able to meet its functional and performance requirements.
Experience also shows that severe degradation mechanisms in concrete systems are very
dependent on material selection, construction methods, procedures and curing approaches. 17
Thus far, quality control/quality assurance programmes at nuclear power plants generally havebeen very effective in ensuring that these factors are adequately addressed (NRC, 1996).
Concrete biological shielding (BS) is the reinforced concrete structure surrounding the RPV,
which protects the environment from the radiation emanating from the core while providing
structural support to heavy components. It is the only concrete system that is expected toexperience severe degradation due to neutron fluence and gamma heating. When neutrons
from the reactor core exit the RPV and encounter the concrete BS, they cause heating and point
defects in the concrete aggregates. Gamma rays produce radiolysis of water exacerbatingconcrete drying effects to a limited extent. Similar to the low-carbon steel in the RPV, rebar canalso experience embrittlement and hardening. Consequently, prolonged exposure to radiation
can result in a loss of tensile and compressive strength, decreases in the modulus of elasticity
and radiation-induced volumetric expansion (RIVE) (NRC, 1996; Bruck et al., 2019). Irradiation
effects have a primary impact on the structural capability of the BS but not on the shielding
properties, which remain practically the same. 18 Work performed by Hilsdorf (1978), Field (2015)
and Maruyama (2017) have shown that degradation of mechanical properties in concrete ispossible beyond neutron fluence levels of 1 x 1019 n/cm2 (E > 0.1 MeV) and gamma irradiationlevels of around 2.3 x 1010 Rad. These fluence and gamma thresholds are likely to be achievedfor operating lifetimes above 60 years (Bruck et al., 2019) but individual plant evaluations would
be necessary to provide precise values for a specific plant application. Recent studies performedby Oak Ridge National Laboratory and the Electric Power Research Institute (EPRI) provide
guidance on evaluating in detail the RIVE of concrete and the potential effects that expansion
may have on structural capacity (EPRI, 2018a). The mitigation measures used to limit RPV
embrittlement can also attenuate degradation of the BS.
Lastly, spent fuel pools are concrete structures containing water at high concentrations ofboric acid for criticality control. Most of them have a stainless-steel liner that is seam welded
together from stainless steel plates, acting as the primary moisture barrier. The ageing of spent
fuel pools causes cracks in the seam and weld plugs with borated water potentially leaking into adrainage collection system. As a result, the boric acid can interact with the concrete substructure
and the constituents of the concrete, leading to boric acid attack and delamination/cracking of
concrete. Recent research performed by EPRI provides a good technical basis for thecharacterisation of degradation of concrete due to aqueous boric acid, and presents a basis for thedevelopment of plant-specific ageing management programmes (EPRI, 2016).
When accessible, concrete structures are subjected to periodic visual inspection andmonitoring. In containment buildings, displacements are measured by means of pendulums,
extensometers and vibrating wire strain gauges embedded in the concrete structure. Periodic
overpressure tests are performed to check if leak tightness levels conform to the licensing
basis. The data collected through in-situ inspections are then analysed to evaluate thekinetics of the defects and ultimately adopt reinforced corrective methods, if necessary.
Repairs and other remediation strategies can be foreseen for most concrete structures,
particularly when they are easily accessible. Extensive industrial experience exists regarding
the evaluation of defects on concrete structures and the identification of repair criteria andmethodologies (NEA, 2002).

17. During the construction of concrete civil structures most of the components are sourced locally, which
can lead to slightly different ageing patterns depending on the plant. Additionally, the Crystal River 3
case described in Box 1.1 illustrates the accelerated degradation mechanisms that can be triggered inconcrete structures in the case of non-respect of procedures.
18. Little variations can be observed as a result of the accelerated reduction in water content due to gamma
heating.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

75

TECHNICAL ASPECTS

Plant electrical cabling system (LWRs, PHWRs)
Cables are made of conductor materials (i.e. copper or aluminium) insulated and arranged indifferent configurations (coaxial, triaxial, etc.) within a cable jacket. Both the wire insulationand the cable jacket are made of different types of polymers, 19 depending on the design andrequirements. Most of the cabling in a nuclear power plant is used for I&C signals (i.e. to activate
relays, pumps, valves and motors), and it is typically designed for low voltage (< 1 kV) andampacity. On the other hand, power cables withstand higher voltage and the currents necessary
for medium- and high-voltage equipment such as pumps.
Cable ageing induces embrittlement and cracking of the polymers (i.e. the insulation andjacket) surrounding the conductor. This physical ageing combined with environmental stressors,
such as high temperatures, humidity or wet environments, cycling mechanical stress, andradiation exposure, can accelerate insulation degradation (see Figure 4.4). Electrical cable systems
were initially categorised as long-lived, passive components that did not require any specificperiodic maintenance, except the cables that were required for safe shutdown of the plant under
accident conditions. 20 As long as the cables were installed properly and were not exposed toenvironmental conditions beyond their design basis, they could be assumed to be reliable without
requiring condition monitoring for the original design life of the plant (typically 30-40 years).
Operating experience has nevertheless shown that cables could fail earlier than expected 21 incabling that operated energised in wet conditions, near design limits and for which initial design
and installation had not been carried out properly. The most common failure mode has been
insulation degradation from water treeing. When moisture reaches the polymers in continuallyenergised power cables (> 2 kV), tree-shaped cracks propagate as a result of electrochemical
reactions, leading to a loss of dielectric properties and potentially jeopardising the integrity of theinsulation.

Figure 4.4: Cable exposed to high ambient, mechanical stress (sharp metal edge),
and radiation effected cables on reactor head

Source: Courtesy of EPRI.

This situation, combined with the need to ensure reliable operation of the cabling during the
LTO period, has led both licensees and regulators to re-evaluate how cable insulations will
perform throughout plant life. Most of these issues can be managed with condition monitoring
approaches, mainly involving plant visual inspections and electric measurements. 22 Periodic
walkdowns with trained personnel are very effective to visually identify cases where a harsh

19. The most common are polyethylene, cross-linked polyethylene, polyvinyl chloride and ethylene
propylene rubber.
20. Nuclear power plant cables have different qualification levels depending on their expected function indifferent scenarios. For instance, the cabling in the nuclear island is expected to perform at hightemperature and irradiation levels (even under loss-of-coolant accident conditions), whereas cables in theconventional island have lower requirements.
21. Around 90% of the failures occurred in normally energised power cables that had been in service
between 11 and 30 years. The failures took place either in service or during inspection tests (NRC, 2010).
22. Chemical and mechanical tests also exist.

76

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

environment, as well as possible installation-related stressors, may require reinforced condition
monitoring. At the same time, various non-destructive electrical measurements can also be
performed in-situ 23 to check the quality of the insulation and identify other anomalies. They
usually involve impedance measurements, partial discharge and Tan Delta 24 testing, among
many other techniques. Nevertheless, these methods provide very little information about cabling
degradation levels and kinetics, nor about the remaining useful life. How to monitor cabledegradation and determine the remaining useful life of cables remain two of the main challenges
for plant operators during LTO. There are several approaches 25 that can be employed to reevaluate the qualified life of cables. Their cost varies significantly depending on the type oftechnique. The most economic strategies simply recalculate the qualified life reducing
conservatisms and harnessing actual environmental plant conditions. Another possibility
consists of leveraging on condition monitoring measurements and elongation at break curves toreassess the residual life. Ongoing research is making significant progress in establishing
relationships between the condition measurements and the kinetics of ageing stressors, but thisapproach has yet to be implemented at an industrial scale. The remaining methods use harvested
cables that are artificially aged to the desired ageing period (i.e. 60-80 years) and then subject themto requalification testing to establish the new lifetime. These methods are very expensive andhave typically been driven by specific regulatory-driven demands.
Large-scale cable replacements, while being technically possible, 26 may be prohibitively
expensive. Operators will therefore favour the implementation of cable qualified life reevaluations and ageing management programmes for cables during LTO. If performed in the most
severe localised environment, cable ageing can be managed economically and efficiently sincecabling in more benign conditions is covered by analyses performed in more severe conditions.
Alternatively, replacing small sections of cabling may be envisaged as a more attractive option
from an economic point of view. Obsolescence issues can also motivate the replacement of some
cables (see Chapter 5).

4.1.2.Ageing considerations during long-term shutdowns
The ageing phenomena affecting critical components described in the previous section, as wellas their associated kinetics, have been observed in reactors operating at nominal conditions 27
for long periods. However, nuclear reactors accumulate a significant amount of time during
which they are not operating at full power. This is typically the case for normal outages or longterm shut-down periods necessary to undertake major refurbishments and/or safety upgrades.
If long-term shut-down periods are considered as fully operational years from an ageing
degradation point of view, the economic attractiveness of performing LTO could be significantly
reduced, especially is those countries where the LTO period is fixed and limited by the law (e.g.
in Japan).
In order to assess the impact of long-term outages on SSC ageing, it is necessary tounderstand the physical state of the plant under these conditions. When reactors are shut down,
the fission reaction is stopped (i.e. zero nuclear power) and the primary circuit is progressively
cooled down until it reaches “cold” conditions corresponding to temperatures lower than 100°C
and atmospheric pressure. The decay heat removal system is also connected to evacuate decay
heat from fission products. As a result, most major environmental stressors (e.g. intense
neutron fluxes, high temperatures, pressure and fatigue) are removed, and maintenance andinspection work are also facilitated.

23. Tests that can be performed without disconnecting the cable from its in-service connections or
removing the end device.
24. Also known as dissipation factor, this technique can be used to effectively manage water treeing andthermal insulation degradation in medium-voltage cables. Standards such as IEEE 400.2 provide thenecessary guidance.
25. Standards such as IEEE/IEC 323/60780, for instance.
26. This was the case, for instance, for the Beznau nuclear power plant in Switzerland (Murty, 2013).
27. Full core power with the primary circuit at 285-320°C and 155 bars for PWRs, for instance.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

77

TECHNICAL ASPECTS

Recent research confirms that the main ageing degradation mechanisms are significantly
slowed down in life-limiting components during long-term shut-down conditions (JNO, 2018;
EPRI, 2018b). If complemented with the adequate maintenance approaches and punctual
replacements, when necessary, long-term outages should not reduce the typical duration of
LTO periods (see Figure 4.5).

Figure 4.5: Qualitative representation of the impact of long-term
shut-down periods on SSC ageing
Normal operating conditions

Extended shut-down period

Degradation

Degradation limit

0

10

20

30

40

50

60

70

80

Years

4.1.3.Recent progress on operation beyond 60 years in LWRs
LTO of nuclear reactors beyond 60 years will increase demands on materials and components,
potentially increasing their susceptibility to ageing phenomena or even triggering new
degradation modes.
The United States is one of the countries with the oldest LWR fleet. In 2012, the United States
initiated a systematic review to identify the main technical issues and to prioritise the necessary
research activities that would support LTO beyond 60 years through subsequent licence renewal(SLR). The main research areas for SLR involve:•

RPV neutron embrittlement: Data on embrittlement and hardening phenomena at highfluences is sparse, or non-existent in some cases. Specimens can be irradiated in core andin test reactors to accelerate ageing and generate the necessary experimental data.
Available research data for fast reactors could also be used. However, technical limits may
arise from the use of surrogate materials and the validity of accelerated testing that may
lead to non-conservative extrapolations. There is also experimental evidence that Ni-richprecipitates could appear at high fluence levels (the so-called “late blooming”), rapidly
reducing fracture toughness margins. Under these conditions, performing thermal
annealing 28 could be envisaged during LTO beyond 60 years. It is therefore necessary tounderstand the behaviour of annealed RPVs, as well as the potential impact of this
remediation measure on the surrounding SSCs (i.e. concrete BS). Further, potential
attenuation of RPV embrittlement through wall thickness should be further assessed as it
could provide extra operational margins. Additional studies are also necessary to properly
judge thermal ageing on the RPV over very long operating time frames (Busby et al., 2008).

28. Heat treatment applied to the inner wall of the RPV to restore its mechanical properties. This process
can be performed in nuclear reactors both in wet and dry conditions. Dry annealing is usually more
effective but requires specific tooling to be performed.

78

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS•

Ageing management for reactor vessel internals and welds: Beyond 60 years of operation,
reactor internals will also experience severe irradiation-induced phenomena, leading tomicrostructural changes and swelling, and increasing their susceptibility to corrosion.
While significant research has been performed on IASCC, the underlying physicalmechanisms are complex, especially over long operational lifetimes (Busby et al., 2008).
Thermal ageing and the formation of a ferrite phase in CASS also requires additional
evaluations. Welds and heat affected zones (HAZ) are also particularly sensitive to ageing.
To be reliable over very long time frames, advanced simulation tools designed to accurately
assess the residual stress in welds, and the development of new welding technologies forrepair, could be useful.

•Concrete and civil structure ageing management and degradation assessment: For
successful operation beyond 60 years, containments could benefit from materials
properties data for long-term performance, improved predictive models (see Box 4.2),
and global inspection and (NDE) methods. In terms of the concrete BS, simulations
carried out by EPRI have shown that irradiation levels after 80 years of operation could
be greater than 1 x 1 019 n/cm2 (Bruck et al., 2019), requiring a better understanding of
the long-term impacts on concrete at elevated temperatures and high irradiation.

•

Electrical cable ageing management guidance and condition assessment: If design
and material specifications during installation are respected, cables can also performsafely for long periods. Ongoing efforts are being made to develop multi-scale
approaches (from microstructural to global polymer behaviour and measurements) tounderstand the kinetics of ageing in cables and assess the degradation state based on
in-situ measurements and tests.

Co-ordinated research performed in the aforementioned areas over the last decade by EPRI,
the US Department of Energy’s (US DOE) Light Water Reactor Sustainability Program (LWRS) andthe US Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research hasprovided the necessary technical basis to assess SSC degradation beyond 60 years, and develop
dedicated ageing management approaches. The results indicate that if utilities implement
enhanced ageing management programmes using the technical evidence already available,
while performing the necessary repairs and replacements, LTO of LWRs until 80 years may not
face any generic technical barriers. To date, six reactors in the United States have been grantedwith SLR, and more utilities are expected to file for SLR in the near future. These trends support
the technical feasibility of LTO operations beyond 60 years. More recently, the NRC has been
exploring the possibility of developing a new licensing framework, allowing US plants to run up
to 100 years (NRC, 2021). Additional research will, however, be required to provide robust
technical evidence supporting safe operation for longer periods.

4.1.4.SSC ageing in other reactor systems
Most ageing degradation mechanisms and considerations described in the previous sections for
LWRs apply to all reactor types, particularly with regard to concrete and cable ageing. Dependingon the system configurations and materials selected, some degradation mechanisms could
nevertheless be accelerated (or attenuated), requiring different ageing management andreplacement approaches. Life-limiting components could also change.

PHWRs
PHWRs use heavy water (or deuterium [D2O]) as a moderator instead of light water, which enables
the use of natural uranium. One of the most prevalent designs is the Canadian Deuterium
Uranium (CANDU) reactor (see Figure 4.6). This reactor technology consists of horizontal fuelchannels that pass through a sizeable calandria vessel that contains a large inventory of low
pressure and temperature deuterium. Inside each fuel channel, 29 there is a string of naturaluranium fuel bundles cooled by high pressure and temperature deuterium, which carries the

29. The fuel channels are formed of calandria tubes and pressure tubes in a coaxial configuration, and othercomponents such as end fittings and spacers.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

79

TECHNICAL ASPECTS

thermal energy through the feeders to four steam generators (SGs). Depending on their burn-up,
the natural-uranium fuel bundles are replaced using online refuelling (without shutting thereactor down), which increases the availability of this type of reactor. More than 95% of the PHWRs
in operation worldwide are CANDU reactors or an indigenous version of this design (e.g. India)(IAEA, 2021). 30

Figure 4.6: CANDU reactor design

Source: Courtesy of SNC Lavalin.

In terms of ageing considerations, reactor assembly components in PHWRs will be subject toembrittlement, corrosion and stress corrosion cracking, erosion, fatigue and creep and stressrelaxation (IAEA, 2001). In general, neutron embrittlement is less severe than in the case of LWRs
because of the fuel channel materials 31 and the efficient shielding provided by D2O. The main
ageing issue involves the calandria tube rolled joint stress relaxation and calandria tube sag. The
latter can deform under irradiation creep and enter in contact with the horizontal liquid injection
shut-down unit nozzles, leading to fretting wear. This phenomenon has been successfully
managed with routine inspections, but it may become a real concern if PHWRs are operated
beyond 30 years, which corresponds to their initial design lifetime. 32 Consequently, LTO beyond
30 years in the case of PHWRs requires a full retubing to resolve this issue. 33 Stress corrosion
cracking in SGs is also a concern in PHWRs, but experience confirms that with adjustments andremedial measures (i.e. active chemical control) they can operate safely until 60 years without
replacement. 34 Cables and concrete structures will follow similar considerations as thosedescribed in Section 4.1.1.

30

31.
32.

33.
34.

80

Consequently, when referring to PHWRs in the present report, it is implicitly assumed that the reactor isa CANDU-type concept using horizontal pressure tubes. Atucha 1 & 2 units being operated in Argentina,
however, are a type of PHWR developed by the German vendor Siemens-KWU using a vertical RPV
configuration similar to LWR designs. Siemens-KWU PHWRs are not covered in present study.
Reactor assemblies in PHWRs are made of stainless steel and zirconium-niobium, which can withstandhigher neutron fluxes before showing severe embrittlement.
The original design lifetime for PHWRs is not expressed in years but rather in operational hours, and it
can be stated as 210 000 effective full power hours (EFPH), corresponding to approximately 30 years at a
capacity factor of 80%. Operational experience confirms the existence of margins that enable a licenceextension (without extensive refurbishment) to 225 000 EFPH or even to 300 000 EFPH, depending on thedesign and plant conditions.
For CANDU-6 reactors, this would mean the replacement of the 380 calandria tubes, 380 pressure tubes,
760 end fittings, 760 feeders, and various supporting and connecting components.
SGs can be replaced, and some operators may decide to perform in-situ SG replacement as part of thescope of LTO projects, depending on plant conditions (see Box 4.3).

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

Overall, the concrete containment and the calandria vessel are the only non-replaceable
components that could ultimately limit the life of PHWR plants. Recent analyses suggest that athird life cycle of 30 years (thus 90 years of operation) may be technically feasible. It would,
however, require a second retubing and certainly a more extended refurbishment, potentially
including SGs. With regard to the calandria vessel, the low temperature and fluence environment
under which it operates guarantees 90 years of safe operation. The inspections performed until
present support these conclusions.

VVERs
VVER is the acronym of “Vodo-Vodyanoi Energetichesky Reaktor”, a PWR design developed by
Russia in the 1960s and then exported to several countries. As of 2020, there are 62 VVERs in
operation in 8 countries and several projects under construction. Around 60% of the VVER fleet
is older than 30 years. The main differences in relation to VVERs with respect to traditional
PWRs include:•••

horizontal steam generators;
a different core configuration with triangle lattice, hexagonal fuel assemblies andrelatively smaller cores with higher enrichment;
an RPV with a lower diameter, no penetration in the bottom and two levels of coolant
piping.

The physics between VVERs and traditional PWRs are essentially the same. The RPV and theconcrete containment building remain the primary life-limiting components. However, thefollowing specific ageing considerations should be mentioned:•

RPV embrittlement: the RPV materials of early VVER versions (built before the mid1970s) contained high concentrations of copper and phosphor, which accelerated theembrittlement of the inner walls, reducing fracture toughness margins (NEA, 2012b).
Mitigation measures implemented by the operators involved low-fluence fuel loadings,
higher water temperatures in the emergency cooling system, and enhanced in-service
inspections and NDE (Katona, 2011). Several RPVs have also been annealed to enable
extended operation up to 60 years. 35 Various design improvements in subsequent
VVER versions provide significant additional margins against RPV embrittlement.

•

SG performance: the horizontal configuration of SGs in VVERs provides a large surface forevaporation with lower heat flux, thus reducing mechanical stresses and vibrations.
Sediments (sludge) are lower compared to vertical SGs, and they deposit underneath thetube bundle. Also, horizontal SGs can be easily accessed for maintenance. The main ageing
mechanism observed is outer diameter stress corrosion cracking (ODSCC) of the SG tubes.
Operating experience has shown that it appears typically in the grid structure supporting
the tube bundle. A series of modifications have slowed down the rate of ODSCC. The feedwater distributor has also experienced accelerated ageing due to erosion, and it has been
replaced in some VVER reactors. All of these aspects, combined with the suitability of the
SG tube materials, enable LTO without SG replacement.

4.2. The LTO programme
While a solid knowledge of ageing degradation mechanisms is key to enabling LTO, additional
actions are often required to ensure that for a given SSC the associated safety functionality isavailable throughout the LTO period. A LTO programme is a systematic process that combines
both technical evidence and organisational aspects to maximise the life of a nuclear power plant.
Proven tools and procedures guide operators through the process, enabling the identification ofpotential replacements, as well as specific measures for life-limiting components. The
governing frameworks associated with LTO programmes also allow for internal periodic reevaluation and external peer reviews in order to identify potential shortfalls and provide accessto the latest knowledge available and best proven international practices.

35. Around 15 VVER-440 RPVs were annealed between 1987 and 2017 (Kryukov, Rubtsov, 2017).
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

81

TECHNICAL ASPECTS

An LTO programme for a given nuclear power plant generally has three main stages:i) feasibility studies and preconditions; ii) LTO assessment; and iii) LTO approval andimplementation (IAEA, 2008b).

4.2.1.Feasibility studies and preconditions
After 30 or 40 years of operation, the context in which a nuclear power plant operates may havechanged considerably. A preliminary technical assessment can be performed to identify potential
plant enhancements and replacements, and their economic feasibility based on current andprojected market conditions and energy policies. Regulatory changes and their implications
should also be assessed at this stage. Preconditions for LTO include quality assurance systems, aswell as the availability of the latest safety analyses and associated assumptions.

4.2.2.LTO assessment
If the outcome of feasibility studies is favourable to the LTO option, it is then necessary to
determine the scope of LTO activities in more detail. In this process, all relevant SSCs areanalysed in order to define the best strategy to deal with ageing so as to enable LTO. In general,
the following steps are considered:•82

Individual plant assessment (IPA): Based on specific operating experience and plantconditions, all of the SSCs are screened and classified according to their importance tosafety. Cost and reliability considerations are also taken into account in this assessment.
At the end of the IPA, operators should have a clear understanding of the parts of a given
plant which are:–Non-critical and can be run to failure and replaced without major implications in termsof safety and reliability.

–

Critical but replaceable and thus falling into the category of components that can bepart of the LTO refurbishments (see Section 4.1.1). This is the case for most critical
SSCs in nuclear power plants.

–

Life-limiting as they cannot be replaced for techno-economic reasons, and for which
particular ageing management measures are required during LTO (see Section 4.1.1).

•

Ageing management reviews (AMRs): Critical components are then subjected todetailed reviews in order to identify the main degradation mechanisms, and in whichmaterials, areas and environments they are taking place. The technical evidence onmaterials ageing described in Section 4.1 is considered when performing AMRs.

•

Time limited ageing analysis (TLAA): Using the information collected during the AMRs,
specific time dependent safety analyses are performed in order to extrapolate theimpacts of ageing mechanisms over the period of extended operations and assess
operational margins.

•

Ageing management programmes (AMPs): The issues identified by AMRs and TLAAs
in critical SSCs are resolved through specific ageing management programmes. They
usually cover understanding degradation mechanisms, as well as the prevention,
detection, monitoring, mitigation and remediation of such mechanisms. Associatedactivities include maintenance, in-service inspection, and testing and surveillance.
Inspections are typically supported by NDE involving numerous techniques, dependingon the type of component being inspected. Radiographic (gamma or X-rays), magnetic
and ultrasound methods are used to detect cracks in metallic components and welds.
Eddy current techniques are used to check SG tubes and heat exchangers. Maintenanceapproaches may also vary depending on the AMP needs. Preventive maintenance isusually adopted as it allows for the replacement components before a failure occurs.
Maintenance approaches can be further improved by harnessing risk metrics and data
concerning the actual condition of components (i.e. condition-based maintenance).
The emergence of new digital solutions and simulation tools offers new opportunities
to improve maintenance, ageing management practices and the evaluation of safetymargins in general (see Box 4.2 below). Several examples of ageing management
measures for life-limiting components are provided in Section 4.1.1.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

Box 4.2: Enhancing ageing management approacheswith digital solutions and simulation tools
Several digital solutions are gaining maturity and could be rapidly deployed in the nuclear industry, leading
not only to safety improvements but also to operation and maintenance cost reductions.
Digital twins
Digital twins are virtual and dynamic representations of physical assets. The data provided by sensors
embedded in the real assets or by wearable and mobile devices carried by workers (e.g. cameras, tablets)during inspections are used to feed powerful predictive models that simulate the physical behaviour of theasset over time. As a result, digital twins close the loop between the physical and virtual realms to represent
the current (and future) ageing condition of a given component almost in real time.
Nuclear operators are already developing these solutions to enhance their ageing management plans. One
example is the VERCORS project led by the French utility, EDF. VERCORS aims at developing a digital twin of
the concrete containment building of a French 1 300 MWe PWR (P’4 series). For the development of VERCORS,
a one-third scaled mock-up of a P’4 containment building was built. Because of its reduced size, the concrete
drying is around nine times faster than the larger-scale model, leading to accelerated ageing patterns that aremonitored in real-time thanks to the numerous sensors inserted in the main structures of the mock-up (seeFigure 4.7 below). Tests performed in 2016 validated the main ageing assumptions and models. In 2019, ageingin the VERCORS mock-up was greater than in actual P’4 containment buildings, allowing it to become a fully
predictive tool. Thanks to VERCORS, EDF expects to increase its understanding of the leak-tightness evaluationin these types of containment vessels beyond 40 years, as well as to optimise maintenance strategies. EDF is
also developing digital twins of SGs to better predict the evolution of corrosion and tube clogging andtherefore increase the availability of the French nuclear fleet.
Figure 4.7: Different types of sensors inserted in the VERCORS mock-up

Source: Mathieu, Masson, 2018.

Integrated and unified information systems
Nuclear power plants already generate enough data to enable the proper assessment of ageing issues.
Retrieving this information is nevertheless very time consuming for the most part since it is distributed acrossseveral isolated databases in different locations and formats, and with different access rights. The traceabilityof data changes is often lacking, hindering the identification of initial assumption and technical choices.
To overcome these issues, some operators are developing shared platforms, and integrated and unified
information systems that provide quick access to relevant information during the elaboration of ageing
management studies. This is the case, for instance, for the piping and component analysis and monitoring system(PAMS) developed by the Finnish utility, TVO (Smeekes et al., 2013). This tool consists of several interconnected
databases and various modules allowing high levels of automation to be achieved when performing mechanicalanalysis of the piping. The new results are automatically synchronised, ensuring that the information in the
databases is always up-to-date. PAMS has been successfully used to support the licence extension of Olkiluoto
units 1 and 2, and could be easily extended to other types of components and technical studies.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

83

TECHNICAL ASPECTS

Advanced analytics and machine-learning applications
The considerable amounts of data generated by sensors inserted in nuclear components can be used to feedadvanced analytics models and machine-learning tools to enable condition-based maintenance plans andpredict adverse situations. Evidence is being accumulated in the United States on the implementation of thesetypes of tools by nuclear operators. In some cases, actionable faults have been predicted accurately more than
three months in advance (Reuters, 2017; WNN, 2018). As a result, ageing management activities could be adjusted
in real time, improving safety margins while streamlining resources. Enhanced or automated chemistry control
for corrosion is also possible with these tools.
Improved simulation tools
Materials ageing analysis is a multidisciplinary approach resulting from the combination of irradiation history,
thermal-hydraulic boundary conditions and mechanical properties. Initial design evaluations for Gen-II
technologies were performed using simplified analytical models 36 based on bounding cases with penalised input
data, accounting for uncertainties and thus leading to very conservative results. Improvements in computer
power have enabled the use of more powerful simulation tools capable of performing three-dimensional, multiphysics and time-dependent simulations, which has resulted in a more precise assessment of actual safetymargins today than in the past, and which supports LTO. In co-ordination with safety authorities, these new tools
and methods have been qualified for use at an industrial scale. Examples include the utilisation of computational
fluid dynamics for RPV integrity assessment and new simulation tools to accelerate the qualification of advanced
NDE (MAI, 2018).

National and international experience on ageing management
With more than 30% of the global nuclear fleet already operating in LTO, there are numerous
national examples of LTO programmes and related ageing management programmes (AMPs).
At the same time, the experience accumulated by some countries represents an opportunity to
improve ageing management worldwide by sharing best practices. International collaborationis also important to accelerate research and extend the knowledge basis in key areas.
Organisations such as the International Atomic Energy Agency (IAEA) and EPRI have played aleading role in setting internationally recognised standards for ageing management and increating the necessary platforms for collaboration and exchanges on LTO experience.
The IAEA International Generic Ageing Lessons Learned (IGALL) initiative was initiated in 2010
and is based on the US Generic Ageing Lessons Learned (GALL) approach. 37 The programme has
facilitated the exchange of experience and the dissemination of best practices with regard to theidentification, establishment and implementation of AMPs. The IGALL programme covers PWRs,
BWRs, VVER, PHWRs and also advanced gas-cooled reactors. The main IGALL document is the
Safety Reports Series No. 82 (IAEA, 2015), which is complemented by the publicly available “IGALL
database”, containing more than 2 000 line items in the AMR table, 76 AMPs and 27 TLAAs to
support LTO assessments all over the world.
Peer reviews in selected countries are also a key element of the global governance of LTO
experience. Every year since 2005, the IAEA organises Safety Aspect of Long Term Operation(SALTO) missions, gathering international experts and IAEA staff to review LTO activities andguide countries on the entire process. The scope of SALTO missions covers IPAs, AMRs, AMPs
and knowledge management, which includes the review of written materials and databases,
interviews with experts and nuclear power plant staff and direct observations on the nuclear
site. The main outcome of the peer review is a report with recommendations and suggestions
for improvement in areas where performance falls short according to international bestpractices. Some examples of issues identified thanks to SALTO missions include: lack of accessto the design basis, incomplete scoping and screening of SSCs for LTO, inconsistency of
databases, inadequate AMP for the containment and insufficient human resources for LTO
activities (Nuclear Engineering International, 2014).

36. Typically one- or two-dimensional analysis with decoupled (non-interacting) physical models.
37. The nuclear power plants in the United States are, on average, five to ten years older than nuclear
plants in Europe and Asia, and their operating experience and management philosophy has informed
the development of the first set of AMPs required for licence renewal by the US NRC. These AMPs helped
create the US GALL report, which became a starting point and forerunner for the IAEA IGALL initiative.

84

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

4.2.3.LTO approval and implementation
Once the LTO assessment has been performed, all of the related documentation and ageing
management measures for the LTO period undergo regulatory review according to national andinternational standards. Depending on the regulatory framework, the scope of the LTO evaluation
is identical to the periodical safety reviews imposed by regulators. In some cases, once the plant
has reached its initial design lifetime, regulations may reinforce AMPs in life-limiting components.
These aspects are further explored in Chapter 5.
During the implementation of an LTO programme, and according to the outcome of the IPAs
and specific plant conditions, some components will be completely replaced (see Section 4.3.1)
or follow specific AMPs. The success of the programme will rely on a systemic approach that:•co-ordinates ageing management activities at all organisational levels;•

continually monitors programme effectiveness to identify potential shortfalls;•

screens international best practices and follows peer reviews;•

applies corrective actions as necessary.

These principles are those of Deming’s continuous improvement and total quality
management “plan-do-check-act” summarised in Figure 4.8 below. Extensive documentation isavailable to develop and implement LTO programmes.

Figure 4.8: Systematic approach for ageing management

Source: IAEA, 2018a.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

85

TECHNICAL ASPECTS

4.3. Replacement, refurbishments and upgrades
The primary objective of LTO refurbishments is to compensate materials ageing, but experience
shows that operators use the extended shutdown period 38 to implement additional plant
retrofits. The objective is not only to update the plant to new safety standards but also toincrease the overall economic attractiveness of the LTO business case. The LTO extension periodahead will heavily influence the return on investment of some of these solutions and thus the
final scope of work.

4.3.1.Scope of LTO refurbishments
Most of the components of a nuclear power plant can be replaced. As part of LTO assessments,
operators determine which components will be changed, as well as those that will follow specificAMPs, taking into account technical and economic considerations. The final scope is plant-specific,
and is based on the design characteristics, operational experience and history, as well as previous
refurbishments.
The typical scope of LTO refurbishments includes:•

Mechanical equipment – upper vessel heads, steam generators, turbines, pumps, motors,
etc.;

•

Fluid systems – service water piping replacement with corrosion resistance materials,
independent core cooling system, large diameter piping, buried piping replacement withhigh-density polyethylene, etc.

•

Electrical equipment – alternators, transformers, high voltage posts, electrical boards, etc.;•

Instrumentation and controls – control room, cables, sensors, etc.;•

Civil works – cooling towers, for example;•

Post-Fukushima – filter vents, emergency diesel generators, additional ultimate coolingsystems, etc.;•

Other – fire protections, etc.

This list of components accounts for most of the overnight costs associated with LTO
investment (see Chapter 6). It is important to highlight that LTO replacement and safety
upgrades usually go together as both are evaluated by regulators to approve licence extensions.
This is the case, for instance, for post-Fukushima safety upgrades. It could be argued that postFukushima measures are not an LTO expense per se as they do not directly relate to ageing.
Nevertheless, under the current regulatory framework, no licence extension could be granted
without complying with post-Fukushima standards. In addition, some safety improvements arealso implemented on a voluntary basis by operators, and do not follow any regulatory demand.
Some examples of the scope of LTO refurbishments for specific plants and designs areillustrated in Box 4.3.

38. Of several months or even years.

86

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

Box 4.3: LTO refurbishment examples
France (PWRs, Tricastin-1 case)
Tricastin 1 was the first 900 MWe unit to finalise the 4th decennial outage in late 2019 as part of the Frenchlong-term operation programme. 39 French regulations require an update of the licensing basis every ten years
according to the most recent designs. 40 A significant part of the work was thus related to the implementationof post-Fukushima safety measures to ensure the management of severe, beyond-design-basis accidents.
These measures included the installation of two ultimate emergency diesel generators, additional diversified
emergency cooling systems for the secondary circuit, spent fuel pools and the containment, U5 filter vents, acorium stabiliser, reinforcement of the protection against earthquakes and an additional control room for
operation under extreme events. 41 As part of periodic safety re-evaluations, stress tests (i.e. over pressurisation)
were performed in the primary and containment buildings to verify their leak tightness. The RPV was also
subjected to an overall inspection with cameras and automated NDE. Some replacements involved electricalequipment, the rotor of the alternators and the filters for the pumping station of the tertiary circuit (Payen,
Willot, 2019).
Refurbishment work at Triscastin-1 took around 23 months 42 for a total investment of EUR 250 million. The final
regulatory approval for extended operations beyond 40 years was granted by the end of 2020 with possible
additional requirements by 2023, depending on the outcome of the regulatory oversight. Similar refurbishments
will be executed in 21 additional 900‑MWe units before 2025.
Argentina and Canada (CANDU-type PHWR, the case of Embalse, and of Darlington units)
To date, seven CANDU reactors worldwide have undertaken major refurbishments to extend operations for an
additional 30 years. As indicated previously, this requires at least a full retubing (or replacement of calandria
and pressure tubes, as well as related feeders and end fitting) of the plant. This activity typically represents
more than 50% of the scope of work of LTO projects. Two CANDU refurbishments have been successfully
finalised in recent years: Embalse in Argentina and Darlington-2 in Canada.
Embalse is a CANDU 6 reactor run by the Argentinean utility, NA-SA, since 1983. This unit was the thirdCANDU 6 plant to go through refurbishments, after Wolsong 1 in Korea and Point Lepreau in New Brunswick,
Canada. After several years of planning, preparation and training, the unit was taken offline in December 2015
and returned to service around 3 years later in January 2019. The Embalse LTO project is the most extensive
refurbishment of a CANDU 6 reactor executed to date, involving a series of upgrades throughout the station
beyond full retubing, such as:
•
•
•
•
•
•

steam generator replacement;
control computer replacement;
turbine and balance of plant refurbishment, for example a power uprate of 6%;
diesel generator replacement;
moderator heat exchanger and valve replacement;
safety systems improvement and modernisation.

Because of its unique enlarged scope, the Embalse project faced various, first-of-a-kind challenges in CANDU
refurbishments, in particular the interference of the retubing work with the steam generator replacement. The
experience gathered provides valuable lessons for ongoing and future CANDU refurbishments taking place inCanada.

39. Other French reactors that have already completed their 4th decennial outages are Bugey 2 (February2021) and 4 (June 2021) units.
40. In other words, a 900 MWe unit operated beyond 40 years must fulfil the requirements for EPR designs.
41. Other post-Fukushima measures for the entire French nuclear fleet include the establishment of a
special force for rapid action (or FARN). In the case of a nuclear accident, this team is capable of offering
assistance in less than 24 hours at any nuclear power plant on French territory and of mobilising
portable cooling systems.
42. A total of 18 months with the reactor in operation, and 5 months of decennial outage.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

87

TECHNICAL ASPECTS

The aforementioned aspects are also applicable to the larger CANDU9 units at the Darlington site. Its four units
started operations in the early 1990s and supply 3 524 MW to the Ontario grid. Major LTO work has beenscheduled to take place between 2016 and 2026. The first unit that was taken offline for refurbishment was
Darlington 2, which resumed operations in April 2020.
The IPA performed on Darlington reactors confirmed that the calandria vessel and steam generators were fit
for at least an additional 30 years of operations. Consequently, the refurbishment scope is essentially limited
to retubing. The extended refurbishment outage nevertheless presents an opportunity to perform
maintenance or upgrades on the turbine generator set and balance of plant equipment, including the cleaningof the steam generators and the installation of access ports to improve inspection capabilities. The ten-year
period also allows for many extra activities to be performed, which are not directly related to unit
refurbishments covering safety upgrades (e.g. installation of emergency power generators and filter vents),
personnel training (e.g. full-scale control room simulator), enhanced operational flexibility and improved
access to the plant (e.g. new highway interchange).
The six units at Bruce nuclear power plant will experience similar refurbishments between 2020 and 2033.
Overall, LTO investments in Canada will represent CAD 24 billion for an additional 30 years of operation.

4.3.2.Plant enhancements for LTO
Typical plant enhancements executed during LTO outages include power uprates, I&C upgrades,
flexible operations and plant modernisation. The latter two are real options for utilities inelectricity systems facing increasing market pressures and grid constraints due to higher VRE
penetration levels (see Chapter 2). Supply chain obsolescence is also forcing some operators to
update the I&C systems of the plants.

Power uprates
A power uprate is an increase of the net electrical power of a nuclear power plant. These
uprates usually vary between 2-7% of the nominal power and leverage on existing design
margins enabling the accommodation of higher outlet temperatures and steam flows. Moreextensive power uprates (>20%) may require major plant modifications, affecting highpressure turbines, condensate pumps and motors, main generators, and/or transformers (NRC,2020). Power uprates result in permanent higher temperatures and neutron fluxes for the RPV
and core internals, as well as higher fatigue, hence accelerating materials ageing. Since 1977,
a total of 164 power uprates, ranging from 1% to 20% have been approved by the NRC in the
United States, resulting in 7.9 GWe of additional generating capacity. While power uprates
tend to reduce materials degradation margins, their impacts are well-known, measurable andpredictable, and they do not hinder extended operations of nuclear power plants.

Flexible operations
Extensive operational experience exists in load-following mode for PWRs, emanating from
France and Germany, among other countries (NEA, 2012a). More recently, some nuclear power
plants have been operating in flexible mode in North America (Canada and the United States).
Many of the existing LWRs in the above countries have been upgraded to improve theiroperational performances and manoeuvring capabilities. Retrofitting mostly involves the I&C
system, the in-core measurement and monitoring equipment, the adoption of less absorbing
control rods (grey rods) and the optimisation of fuel rods and pellets. Today, ramps of 1-5%
power variations per minute can be performed with maximal changes in 30 seconds of 5-10%.
Nuclear power plants participate in the primary and secondary frequency control, and someunits follow a variable load programme with one or two large power changes per day. The
implementation of flexible operation also requires specific ageing management approaches
and personnel training. The necessary plant modifications to enable flexible operations in
LWR and PHWR designs have been well documented by EPRI (2014).
The additional plant transients and cycling associated with flexible operations may induce
wear, erosion, and fatigue in many systems and have implications on fuel management andfuel elements that need to be evaluated. Specific ageing issues reported for PWRs involve valves

88

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

in the chemical and volume control systems, control rod drive mechanisms and the surge linein the pressuriser. Temperature transients may also impact secondary systems (erosion of pipes,
ageing of heat exchangers). No impact to fuel reliability and fuel failures have been reported todate. Overall, all of these ageing impacts can be accommodated by existing operational margins
and properly managed via reinforced inspections and maintenance approaches. More detailed
information about the potential impacts of flexible operation on nuclear power plants andpossible remediation measures is provided in the IAEA report entitled Non-Baseload Operation in
Nuclear Power Plants: Load following and Frequency Control Modes of Flexible Operations (2018b).

I&C upgrades
Most of the Gen-II I&C systems are analogue 43 with a life cycle ranging between 30 and 40 years.
Analogue systems have proven to be adequately designed and reliable enough to meet theirintended function over their original design lifetime; however this has not prevented some
operators from evaluating their replacement by digital systems for extended operations. In
addition to the economic advantages associated with the adoption of digital devices, such as
lower operational costs and a greater reliability and availability of the assets, technologicalobsolescence has become a real concern over the last years. Given unattractive market
conditions, the main original equipment manufacturers (OEMs) have disappeared or have
simply disinvested in I&C analogue equipment, leading to a loss of critical know-how andinhibiting timely replacement of these systems. In some cases, operators have been able tosecure strategic stocks of critical equipment and devices that are periodically re-evaluated.
Reverse engineering is also used by alternative suppliers to design similar analogue applications,which comes at a significant cost premium owing to the lack of economies of volume.
There are examples demonstrating that it is possible to replace analogue I&C by digitaltechnology even for the highest safety class applications. In Sweden, for instance, a major digital
upgrade on the Ringhals 2 PWR included the control room, reactor protection and control
systems, and turbine control, as well as the installation of a new plant simulator. Projectplanning began in the 1990s, and major installation and testing was performed in 2009-2010
during a 10-month outage for a total cost of EUR 10 million. Similar projects have been carriedout in Finland for the Loviisa units (i.e. LARA and ELSA projects) and in France for 1 300 MWe
reactors (i.e. the M2C project).
Successful digital I&C refurbishment requires significant upfront efforts in terms of detailed
definitions and planning, personnel training, and close co-operation between operators, suppliers
and regulators. Qualification and licensing are often cited as the main obstacles for the adoptionof digital applications in the nuclear industry. Some regulators may be reluctant to embrace thesetypes of solutions because of potential black box effects 44 and increased vulnerabilities in termsof common cause failure and cybersecurity. Low IT maturity levels in some utilities can also
prevent operators from taking advantage of the latest technology available and may need extra
investment. The more frequent software updates related to digital applications can also be
regarded as plant modifications and thus require safety review, increasing the overall cost burden.
For these reasons, despite the recognised benefits of digital technology, plant-specific evaluations
are needed to properly assess the return of I&C investments and the obsolescence strategy.

Plant modernisation
The ongoing digital transformation taking place in other industries provides a wide range ofopportunities to modernise existing nuclear power plants. Rather than simply focusing on the
introduction of new technologies, plant modernisation provides an opportunity to rethink thecurrent value processes at nuclear power plants around advanced digital technologies in orderto reduce operational costs and maximise the availability of the plant. Examples from otherindustries provide valuable lessons to accelerate this process while minimising overall
implementation risks.

43. Some designs, such as the French 1 300 MWe and N4, as well as more advanced versions of CANDU
reactors, integrate digital I&C systems to some extent. This is also the case for Gen III/III+ designs.
44. Difficulties in analytically linking the input of a system with its output.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

89

TECHNICAL ASPECTSWork conducted by EPRI in collaboration with the Nuclear Energy Institute (NEI) and DOE inthe United States have identified at least 12 enabling processes that could be deployed in the
nuclear industry (Barker, 2019). Immediate applications to save on costs involve conditionbased equipment maintenance (see Box 4.2), integrated monitoring and diagnosis, mobile work
execution, automated work planning and automated chemistry monitoring. Other technicalareas cover wireless connectivity throughout the plant, risk-informed engineering and decision
making, common information models, and continuous monitoring of radiation levels and realtime anomaly analyses in life-limiting components (EPRI, 2019a).
Similarly to I&C upgrades, plant modernisation faces challenges related to qualification,
licensing, cybersecurity concerns and uncertainty around the effective return of investment. Early
involvement with regulators could facilitate the licensing process, especially when important-tosafety SSCs are concerned. Moreover, most of these digital tools require robust IT infrastructuresand effective change management (e.g. training of personnel) to deliver their full potential,
requiring additional expenses that should not be neglected. In economic terms, initial estimates
performed for US nuclear power plants suggest that many utilities can justify plant modernisation
investment of more than USD 100 million. Justifiable investment for some US plants could reach
USD 500 million for a 25% cost reduction and USD 1 billion for a 50% reduction (EPRI, 2019b).

Key findings•

Significant research has been completed on the identification and management of the main ageing
phenomena in life-limiting SSCs in nuclear systems, providing a solid technical basis for safe, long-term
operation, if the necessary replacements, maintenance and ageing management policies are performed.

•

The technical knowledge base is complemented by ageing management programmes and robust
governance models consisting of periodic re-evaluations, peer reviews and best practice sharing globally,
which ultimately enables early detection of potential deviations and the application of corrective
measures when necessary.

•

Most of the components of a nuclear power plant can be replaced, and significant industry efforts can be
carried out throughout plant life to refurbish the plant components and maintain or even improve plantmaterial conditions.

•

LTO refurbishments are also an ideal opportunity to upgrade the safety of the plant, as well as toimplement additional plant enhancements, such power uprates, I&C upgrades (e.g. replacement of
analogue equipment with digital one), flexible operations and overall plant modernisation. The objective
is mainly to improve safety, but also overall plant economics through increased availability and reduced
operating costs during the LTO period.

References
Allen, T., J. Busby, M. Meyer et al. (2010), “Materials challenges for nuclear systems”, Materials
Today, Vol. 13, No. 12, pp 14-23, https://doi.org/10.1016/S1369-7021(10)70220-0.
Baills-Barraco, L., A. Courtois (2018), “Ageing of concrete civil structures: Some aspects of EDF’s
in-service inspection program and risk-informed approach”, MAI 10 years Anniversary
Scientific Day, Materials Ageing Institute, Moret-sur-Loing.
Barker, B. (2019), “Preliminary EPRI Analysis: 25% or More Cost Reduction May Be Viable for Many
Plants”, EPRI Journal, https://eprijournal.com/can-nuclear-power-become-more-economicaland-help-address-climate-change-by-modernizing-old-plants/.
Benhamou, C., S. Vidard (2019), “Durée de fonctionnement de la cuve“, Poursuivre le fonctionnement
des réacteurs nucléaires après 40 ans, Journée Technique, Sfen, Paris90

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

Bruck, P.M., Esselman, T.C., Wall, J.J. et al. (2019), “Structural assessment of radiation damage inlight water power reactor concrete biological shield walls”, Nuclear Engineering and Design,
No. 350, pp. 9-20, www.sciencedirect.com/science/article/pii/S0029549319300950.
Busby, J.T., R.K. Nanstad, R.E. Stoller et al. (2008) Materials Degradation in Light Water Reactors: Life
after 60 years, ORNL report, https://info.ornl.gov/sites/publications/Files/Pub12715.pdf.
Chen. M, F. Lu, R. Wang et al. (2014), “Structural integrity assessment of the reactor pressure
vessel under the pressurized thermal shock loading”, Nuclear Engineering Design, No. 272, pp.
84-91, www.researchgate.net/publication/261218964_Structural_integrity_assessment_of_
the_reactor_pressure_vessel_under_the_pressurized_thermal_shock_loading.
EPRI (2019a), Nuclear Plant Modernization – Initiative Plan 2019, Technical report, 3002015804,
www.epri.com/research/products/000000003002015804.
EPRI (2019b), The Economics of Nuclear Plant Modernization in U.S. Markets, Technical Update,
3002014737, www.epri.com/ - /pages/product/000000003002014737/?lang=en-US.
EPRI, (2018a), Irradiation Damage of the Concrete Biological Shield, Basis for Evaluation of Concrete
Biological Shield Wall for Aging Management, Technical Report, 3002011710, www.epri.com/ /pages/product/3002011710/?lang=en-US.
EPRI (2018b), Materials Reliability Program: Electric Power Research Institute (EPRI) Review of theJapanese Nuclear Operators’ (JNOs’) Aging Management Plan for Prolonged Shutdown Periods (MRP435), Technical Report, 3002014336, www.epri.com/ - /pages/product/000000003002014336/?lang=en-US).
EPRI (2017), Long Term Operations: Aging Management of Concrete Structures Affected by Alkali-Silica
Reaction, Technical Report, 3002010093, www.epri.com/ - /pages/product/3002008117/?lang=en-US.
EPRI, (2016), Aging Management for Leaking Spent Fuel Pools, Technical Report, 3002007348,
www.epri.com/ - /pages/product/3002007348/?lang=en-US.
EPRI (2015), Tools for Early Detection of ASR in Concrete Structures, Technical Report, 3002005389,
www.epri.com/ - /pages/product/3002005389/?lang=en-US.
EPRI (2014), Program on Technology Innovation: Approach to Transition Nuclear Power Plants to Flexible
Operations, Technical Report, 3002002612, www.epri.com/research/products/000000003002
002612.
Field, K., et al. (2015), “Radiation effects in concrete for nuclear power plants – Part I:
Quantification of radiation exposure and radiation effects”, Nuclear Engineering and Design,
pp. 282 126, www.sciencedirect.com/science/article/pii/S0029549314005603.
Hilsdorf, H. et al. (1978), The Effects of Nuclear Radiation on the Mechanical Properties of Concrete,
American Concrete Institute Report SP-55-10, pp. 223-254, http://large.stanford.edu/
courses/2015/ph241/anzelmo1/docs/hilsdorf.pdf.
IAEA (2021), Power Reactor Information System (PRIS) (database), https://pris.iaea.org/PRIS/home.aspx(accessed on 29 June 2021).
IAEA (2018a), Ageing Management and Development of a Programme for Long Term Operation of Nuclear
Power Plants, Specific Safety Guide, No. SSG-48, IAEA, Vienna, www-pub.iaea.org/MTCD/Publications/PDF/P1814_web.pdf.
IAEA (2018b), Non-Baseload Operation in Nuclear Power Plants: Load following and Frequency Control
Modes of Flexible Operations, IAEA, Vienna, www-pub.iaea.org/MTCD/Publications/PDF/
P1756_web.pdf.
IAEA (2015), Ageing Management for Nuclear Power Plants: International Generic Ageing Lessons
Learned (IGALL), Safety Report Series, No. 82, IAEA, Vienna, www-pub.iaea.org/MTCD/
Publications/PDF/Pub1675web-6125893.pdf.
IAEA (2008a), Heavy Component Replacement in Nuclear Power Plants: Experience and Guidelines, IAEA,
Vienna, www-pub.iaea.org/MTCD/Publications/PDF/Pub1337_web.pdf.
IAEA (2008b), Safe Long Term Operation of Nuclear Power Plants, Safety Report Series. No. 57, IAEA,
Vienna, www-pub.iaea.org/MTCD/publications/PDF/Pub1340_web.pdf.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

91

TECHNICAL ASPECTS

IAEA (2001), Assessment and management of ageing of major nuclear power plant components importantto safety: CANDU reactor assemblies. IAEA-TECDOC-1197, IAEA, Vienna, www-pub.iaea.org/
MTCD/publications/PDF/te_1197_prn.pdf.
JNO (2018), Technical Report regarding the Effects of Nuclear Power Plant Operating Period on Aging
Degradation of Major Components/Structures, Japanese Nuclear Operators.
Katona, T. J. (2011), Long-Term Operation of VVER Power Plants, Nuclear Power - Deployment, Operationand Sustainability, Pavel Tsvetkov, IntechOpen, www.intechopen.com/books/nuclear-powerdeployment-operation-and-sustainability/long-term-operation-of-vver-power-plants
Kryukov, A., V. Rubtsov (2017), “Effectiveness assessment of “wet” annealing for VVER reactor
in reactor pressure vessels”, 4th International Conference on NPP Life Management, IAEA, Vienna.
MAI (2018), “MANDENA-2: Computer modelling of Non-destructive Evaluation Methods fornuclear applications”, MAI 10 years Anniversary Scientific Day, Materials Ageing Institute,
Moret-sur-Loing.
Maruyama, I., et al., (2017) “Development of Soundness Assessment Procedure for Concrete
Members affected by Neutron and Gamma-ray Irradiation”, Journal of Advanced Concrete
Technology, 15 (9), pp. 440-523, www.jstage.jst.go.jp/article/jact/15/9/15_440/_article.
Mathieu J-P., Masson, B., et al., (2018), “VERCORS Project: An Effort to Develop Digital Twins”,
MAI 10 years Anniversary Scientific Day, Materials Ageing Institute, Moret-sur-Loing.
Mizutani, J. et al. (2001) Study on Reactor Vessel Replacement (RVR) for 1100 MWe class BWR Plants inJapan, https://inis.iaea.org/collection/NCLCollectionStore/_Public/33/003/33003507.pdf?r=1.
Murty, K. L., (2013), Materials’ ageing and degradation in light water reactors: Mechanisms andmanagement, Woodhead Publishing Series in Energy, No. 44, Woodhead Publishing, Cambridge.
NEA (2012a), Nuclear Energy and Renewables, OECD Publishing, Paris, www.oecd-nea.org/ndd/
pubs/2012/7056-system-effects.pdf.
NEA, (2012b), The Economics of Long-term Operation of Nuclear Power Plants, OECD Publishing, Paris,
www.oecd-nea.org/ndd/reports/2012/7054-long-term-operation-npps.pdf.
NEA (2006), Nuclear Power Plant Life Management and Longer-term Operation, OECD Publishing, Paris,
www.oecd-nea.org/ndd/pubs/2006/6105-npp-life-management.pdf.
NEA (2002), “OECD_NEA Workshop on the evaluation of defects, repair criteria & methods ofrepair for concrete structures on nuclear power plants, Committee on Safety of Nuclear
Installations”, OECD Publishing Paris, www.oecd-nea.org/upload/docs/application/pdf/2020-01/csni-r2002-7-vol2.pdf.
NEA (2000), Status Report on Nuclear Power Plant Life Management, OECD Publishing, Paris,
www.oecd-nea.org/ndd/docs/2000/sen-ndc2000-6.pdf.
Nuclear Engineering International (2014), “A peer review for long term operation”,
www.neimagazine.com/features/featurea-peer-review-for-long-term-operation-4356303/.
NRC (2020), Types of power uprates, www.nrc.gov/reactors/operating/licensing/poweruprates/type-power.html.
NRC (2010), Essential elements of an electric cable condition monitoring program, NUREG/CR-7000 BNLNUREG-90318–2009, NRC, Washington, DC.
NRC (1996), Report on Aging of Nuclear Power Plant Reinforced Concrete Structures, NUREG/CR-6424,
www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr6424/cr6424.pdf.
US DOE (2012), Materials Aging and Degradation Technical Program, Light Water Reactor
Sustainability Program, US DOE, www.energy.gov/sites/prod/files/LWRS_Materials_Aging_%
26_Degradation_Technical_Program_Plan_September2012.pdf.
Payen, L., E. Willot (2019), “Evolutions techniques liées à la 4ème Visite Décennale: case de
Tricastin”, Poursuivre le fonctionnement des réacteurs nucléaires après 40 ans, Journée Technique,Sfen, Paris.
Pokor, C., B. Allouch, A. Demma et al. (2018), Vessel Internals Projects, Materials Ageing Institute.

92

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

TECHNICAL ASPECTS

Reuters (2017), “GE Hitachi expands Exelon analytics learnings to US nuclear fleet”, www.reuter
sevents.com/nuclear/ge-hitachi-expands-exelon-analytics-learnings-us-nuclear-fleet.
Smeekes, P. et al. (2013) “Applications of the TVO Piping and Component Analysis andMonitoring System (PAMS)”, Transactions, SMiRT-22, San Francisco.
WNN (2018), “PSEG plants to use Rolls-Royce Big Data services”, https://world-nuclearnews.org/Articles/PSEG-plants-to-use-Rolls-Royce-Big-Data-services.
Zinkle, S.J., Was, G.S. (2013) “Materials challenges in nuclear energy”, Acta Materialia, Vol. 61,
No.3, pp. 735-758, www.sciencedirect.com/science/article/abs/pii/S1359645412007987.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

93OPERATIONAL AND HUMAN ASPECTS

5. Operational and human aspects

Countries evaluating the possibility to extend the operation of their nuclear power plants beyond
their initial design lifetimes must understand the operational implications of such decisions.
While the ageing of structures, systems and components (SSCs) will certainly determine the final
lifetime of a nuclear power plant, it does not necessarily imply that safety or reliability concerns
will be observed over the long term. As demonstrated in Chapter 3, nuclear operators have various
options and approaches at their disposal to cope with ageing and to sustain safe operations during
the long-term operation (LTO) period. These options and approaches include SSC replacements
and technical advances, but also organisational improvements; all of which are carried out underpermanent regulatory oversight, and in most cases, under the aegis of international peer reviews.
Industry-led regulation activities may complement these approaches with the objective ofachieving higher levels of operational excellence.
At the same time, the LTO of nuclear power plants is only possible if countries have the ability
to ensure its success, which also requires access to a robust supply chain that provides highquality components at a reasonable cost, as well as the presence of a constant inflow of a highskilled workforce at all levels. Increasing supply chain pressures and a loss of attractiveness inrelation to nuclear activities are raising concerns in the nuclear sector. Concerted efforts among
various stakeholders (e.g. governments, industry, research institutes and academia) are alreadyunderway to overcome these issues and to secure safe and reliable operations for longer periods.

5.1. Insights on the performance of nuclear power plants
Good performance in nuclear operations is represented through a combination of high safety
and reliability (i.e. energy production) levels. 1 The evolution of the performance of a nuclear
power plant over time will depend on several interrelated factors, from technical, organisationaland governance perspectives:

1.

•

Materials ageing: Materials ageing is the main technical concern that could prevent SSCs
from complying with their expected function during the LTO period. An extensive
knowledge base already exists in terms of the main degradation mechanisms of criticalcomponents in a nuclear power plant and the evolution of their primary mechanicalcharacteristics under a variety of conditions. Of particular importance is the ageing oflife-limiting components, which could ultimately define the lifetime of the plant. These
components require specific measures to mitigate the effects of ageing (see Chapter 3).

•

Replacements: All of the components of a nuclear power plant can generally be replaced,
except the reactor pressure vessel (RPV) and the containment building, the latter ofwhich are life-limiting components. Cabling and RPV-internals can also be considered as
life-limiting components, but their possible replacement is subject to economic
considerations. The final scope of replacements necessary for LTO is not universal since
it varies according to plant-specific conditions and regulatory requirements that areevaluated during the individual plant assessment for LTO.

•

Technical progress: The nuclear sector has also benefited from continuous progress inmaterials development, engineering and computer science, among other disciplines.

In the present chapter, the term “performance” implicitly refers to both adequate safety and reliability
levels, with safety being the overriding priority.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

95

OPERATIONAL AND HUMAN ASPECTS

Advances in multi-physics simulation have expanded knowledge in relation to thecomplex interactions taking place within nuclear reactors and has allowed for a moreaccurate assessment of safety margins. Probabilistic safety analyses have been developed
to enable the use of risk metrics, which are designed to improve maintenance strategies
based on the criticality of systems and actual plant conditions. Today, the latter can bemonitored, for example by means of sensors embedded in components and postprocessing tools, which further increases the reliability of the plant. LTO refurbishments
provide good opportunities to incorporate all of these technical advances and modernise
existing nuclear power plants (see Chapter 3).

96•

Operational experience: The first years of operation of a nuclear power plant are
typically characterised by lower availability levels. It is the so-called “running-in” period,
during which personnel learn how the different systems work. Minor technicaladjustments are also implemented to achieve smooth operations. After this period,
performance levels tend to increase as the workforce has a better understanding of the
facility and knows how to proceed under specific conditions, minimising potential
downtimes. Today, nuclear operators and regulators have a better understanding thanforty years ago of how nuclear reactors operate and age, which has a direct and positive
impact on plant operation. As experience continues to evolve, only best practices are
retained and disseminated among new personnel, thus sustaining good performancelevels over time. At the same time, existing nuclear governing frameworks facilitate
operating experience sharing among different plants and operators. Nuclear operators
can hence adopt best safety and operating standards while identifying potential
shortcomings in advance. In fact, younger plants can learn from older nuclear power
plants in LTO in any part of the world and undertake the necessary actions in advanceto avoid potential operational issues. These organisational dynamics explain, to someextent, the continuous improvement of global performance indicators in relation toexisting nuclear facilities despite ageing (see Figure 5.2).

•

Governing framework: Nuclear power plants operate under a governing framework withunique characteristics. First, nuclear power plants are subjected to the regulatory oversightof a competent and independent national authority that ensures that nuclear facilities
comply with the required safety standards. 2 Second, the governing framework operates incontinuous improvement logic at both the regulatory and operational levels. For instance,
regulators periodically review the safety of nuclear power plants using the technicalevidence provided by operators, and by carrying out on-site inspections. As part of the LTOprogrammes, operators continually monitor ageing management practices for criticalcomponents to identify potential deviations. Third, international collaboration andexperience sharing are at the core of nuclear activities. International organisations, suchas the International Atomic Energy Agency (IAEA), the Nuclear Energy Agency (NEA), theElectric Power Research Institute (EPRI) and the European Nuclear Safety Regulators Group(ENSREG), among other organisations, periodically gather operators and regulators
together to exchange on relevant safety- and operational-related topics. Peer reviews (e.g.
IAEA SALTO, ENSREG) 3 involving different experts are usually undertaken as an effective
way to check that the different strategies in place at a given nuclear power plant arealigned with international standards and best practices. Fourth, economic theory supports
the existence of strong incentives for operators to internally regulate their activities in the
nuclear sector. Given the high fixed costs of nuclear generation, operators will tend to
maximise the availability of the plant and implement the necessary enhancements to
reduce unexpected shutdowns. On the other hand, reduced availability can not only
reduce potential revenues, but it can also undermine the reputation of the operator (andthus public perception) and even anticipate closure of the plant. Lastly, in the case of amajor nuclear accident, the asset would be completely lost, leading to a significant

2.

This means that any nuclear power plant currently in operation has approval from the national
authority to operate since it complies with existing regulations; if not, the plant would be taken off-line
and forced to implement the necessary corrective actions.

3.

ENSREG performs topical peer reviews (TPRs) every six years (i.e. European Nuclear Safety Directive)
and the topic examined is always a different one. The TPRs are carried out per country and not per
nuclear power plant, as is the case for IAEA SALTO missions or their equivalents by WANO.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

financial impact and jeopardising the global nuclear business as a whole (Lévêque, 2014).
All of these aspects have pushed nuclear operators to create organisations such as theInstitute of Nuclear Power Operators (INPO) in the United States and the World Associationof Nuclear Operators (WANO), which today make significant contributions to improve
nuclear operations worldwide (see Box 5.1).
•

Safety upgrades: In most regulatory frameworks, the safety of the nuclear power plantis periodically reviewed, and operators must implement new safety upgrades in order tocomply with the latest safety standards (see Chapter 5). The most recent example is theintroduction of post-Fukushima safety measures to reinforce protection against extreme
events potentially requiring accident management in harsh environments, extended
loss of power and/or loss of cooling functions, and accidents simultaneously affecting
multiple units (NEA, 2012b).

Box 5.1: The role of INPO and WANO in the operational excellence of nuclear power
INPO
Internal regulation of the nuclear industry started in the United States with the creation of INPO in 1979 – ninemonths after the Three Mile Island (TMI) accident – based on the recommendations of the Kemeny Commission.
It was clear for US nuclear operators that the reputational risks associated with TMI could have importanteconomic implications on the nuclear business, and that the industry should work together to achieve higher
levels of safety and reliability. As a non-governmental organisation that operates on a non-profit basis, the missionof INPO is to promote excellence in the operation of the US commercial nuclear fleet. The core of its activity is toconduct on-site peer reviews called plant evaluations. The outcomes of these peer reviews are distributed among
INPO members (note that the name of the plant is not typically included) as a way to share best practices andcommon weaknesses. Since 1980, INPO has carried out nearly 1 200 plant evaluations, meaning that each plantin the United States has been inspected at least 16 times, once every two years on average.
The success of INPO was not guaranteed when it was established in the 1980s. This type of industry-driven
endeavour does not escape from the “free-rider” problem (Lévêque, 2014). In theory, some operators tend to be
bad performers to avoid investments, benefiting nonetheless from the good image projected by INPO’s good
performers. However, INPO has somehow overcome these issues through peer pressure that drives change (Pate,
Ellis, 2011). 4 Another powerful incentive provided by INPO to promote operational excellence comes from INPO
ratings, which are used by the industry’s collective insurance company, also known as Nuclear Electric Insurance
Limited (NEIL). Since TMI, every operator requires an insurance from NEIL and, in turn, NEIL considers INPO
membership as a condition for insurability. Depending on plant evaluation ratings, some operators may besubjected to higher insurance premiums, thus undermining the profitability of the plant.
WANO
Similar to INPO, WANO is a not-profit, international organisation with a mission to maximise the safety andreliability of the world’s commercial nuclear power plants. It was established on 15 May 1989 after the
Chernobyl accident, and its members operate 203 nuclear power plants in over 30 countries (WANO, 2020a).
The organisation enables members to provide mutual support, exchange on safety knowledge and operating
experience, and share best practices so as to improve performance through five main programmes: peer
review, performance analysis, member support, training and development, and corporate communications.
The peer review programme provides a critical assessment of plant performance by an experienced team ofglobal industry peers using nuclear industry standards of excellence as defined by the WANO performance
objectives and criteria. A significant milestone was reached in 2009, with every commercial nuclear power
plant in the world peer reviewed at least once.

4.

INPO’s influence has led some operators to implement specific safety upgrades. In one notable case, acompany’s Board of Directors made changes in its executive leadership in response to escalating
concerns pointed out by INPO concerning their corporate management’s lack of responsiveness.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

97

OPERATIONAL AND HUMAN ASPECTS

The performance analysis programme collects, screens and analyses operating experience and performancedata, providing members with lessons learnt and industry performance insight reports, using an international
electronic information exchange system. If particular concerns become evident, a special operating event
report (SOER) is prepared and distributed among members. A SOER was prepared, for instance, six days after
the Fukushima accident, and responses from WANO members were received within two months.
Overall, the benefits of regulation via the nuclear industry through organisations such as INPO and WANO are
acknowledged. Countries fostering similar initiatives as part of their nuclear governing framework could
observe safety and reliability gains for the existing fleet. To increase its effectiveness, internal regulation mustbe performed independently and in a complementary manner to the external oversight carried out by national
regulatory oversight.

As a result, despite the negative effects of materials ageing, the combination of
replacements, new technical progress (including enhanced ageing management programmes),
an expansion of operational experience and additional safety upgrades may all lead to therestoration – or even enhancement – of overall performance levels during the LTO period (seeFigure 5.1). The governing framework ensures that all these measures are implemented in atimely manner and are reviewed according to best international standards in order tocontinuously improve operations at the plant from a technical and organisational point ofview. Existing Gen-II reactors can therefore be seen as evolving assets that are periodically
retrofitted and enhanced for regulatory and economic reasons. In this sense, performancelevels should not abruptly decline as long as the necessary investments and improvements
continue to be carried out as part of the LTO programme.

Performance level

Figure 5.1: Qualitative evolution of the performance level of a nuclear power plant over time

Year 0Materials
ageingReplacements

Technical
progress

Operational
experience

Governing
framework

Safetyupgrades

LTO

Time

Furthermore, global performance indicators support the aforementioned trends and provide
additional insight into the interplay between materials ageing and technical, as well asorganisational, improvements in nuclear power plant operations (see Figure 5.2). Of particularimportance is the evolution of the unplanned capability loss (UCL) factor 5 over time. UCL levels

5.

98

Unplanned capability loss factor accounts for the energy that was not produced during a given period
because of unplanned shutdowns, outage extensions or unplanned load reductions resulting fromcauses under plant management control. Energy loss is considered to be unplanned if it is not scheduled
at least four weeks in advance (IAEA, PRIS).

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

for young plants are typically high and large variations can be observed. These variations are a
result of the running-in period of the facility, during which several systems and procedures areprogressively fine-tuned before reaching steady-state operating conditions. As operational
experience develops, UCL rapidly declines and stabilises at a lower level. From 30 years ofoperation, ageing mechanisms tend to prevail over operational experience, driving UCL levels up
again. Thanks to major replacements and plant enhancements taking place in preparation for LTO,
performance levels beyond 40 years once again become close to those of 20 years before. The
reliability of nuclear power plants may therefore follow a somewhat sinusoidal behavioural
pattern, driven by SSC ageing, replacements and growing operational experience. Reactors
entering LTO after major retrofits should observe lower unplanned outages (Kang, Krivanek, 2017).

Figure 5.2: Evolution of global performance indicators
for the existing nuclear fleet, 2020
Unplanned capability loss factor
8
7
6

5,8

UCL(%)

5
4
3,5

3

3,3
2,4

2,3

2
1
0
0-9

10-19

20-29
Age (years)

30-39

40-49

Note: Each column captures the variability of UCL between 2015 and 2020 for a given age range. The point corresponds to the averagevalue observed during this period.

Unplanned scrams per 7 000 hours critical
1,2
1

Number

0,8
0,6
0,4
0,2
0
2000

2002

2004

2006

2008

2010
US

2012

2014

2016

2018

2020

2022

World

Source: OECD/NEA, using data from IAEA, 2021.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

99

OPERATIONAL AND HUMAN ASPECTS

Similarly, the number of unplanned scrams per 7 000 hours critical provides indirectindications of how well a plant is being maintained and operated. According to the IAEA PRIS
database, this parameter can be defined as the number of unplanned automatic/manualscrams normalised to 7 000 hours of critical operation. Its purpose is to monitor performanceefforts to reduce the number of unplanned reactor shutdowns.
The decreasing trend for both indicators (see Figure 5.2) suggests that the factors presented in
Figure 5.1 contribute to improvements in performance levels despite ageing. A comparison with
US values – the oldest nuclear fleet in the world, with an average age of 40 years and showing
similar patterns – reinforces this conclusion (see Figure 5.2). Similar trends can also be observedin WANO’s global performance indicators (WANO, 2020b). More detailed evaluations considering
actual plant conditions, as well as managerial and human aspects, may be needed to draw similar
conclusions for individual plants.

5.2. The role of the supply chain
Utilities make continuous efforts to refurbish and modernise their nuclear power plants overthe entire lifetime of the plant so as to meet regulatory requirements and to improve plant
performance and economics. LTO therefore requires utilities to have access to a robust andreliable supply chain, capable of delivering high quality components and services. Thus far, thenuclear suppliers have proven their capabilities, with more than 30% of the existing fleet alreadyoperating beyond the initial design life (see Chapter 2). However, supply chain challenges like
SSC obsolescence or difficulties of finding new suppliers are of rising concern, especially inthose countries with a small installed nuclear capacity. Several strategies exist to mitigate
supply chain risks and new approaches can be developed with the approval of regulators tosustain market opportunities while meeting stringent standards.

5.2.1.The characteristics of the nuclear supply chain
A unique characteristic of the nuclear supply chain is the high level of quality assurance andqualification efforts required to produce nuclear SSCs. Only the aviation sector works with asimilar level of stringency and scrutiny. The quality and equipment qualification standards for
SSCs are directly correlated with the safety requirements of the nuclear industry. SSCs innuclear reactors must remain reliable under normal operation, plant transient conditions(e.g. reactor start-ups or shutdowns) and even design-basis accidents (DBAs). Depending on
their functions and their significance for plant safety, 6 SSCs can be classified in three different
safety classes (SC) (IAEA, 2014):•

SC1: any SSC for which failure would lead to consequences of “high” severity;•

SC2: any SSC for which failure would lead to consequences of “medium” severity;•

SC3: any SSC for which failure would lead to consequences of “low” severity.

Safety-classified SSCs are subject to specific nuclear codes and standards (NC&S). They define,in a comprehensive manner, the requirements for the design, manufacturing, installation,commissioning, operation, and maintenance of safety-classified SSCs in accordance with their
expected level of safety and performance. According to NC&S, SSCs are referred to as “nuclear
grade”.
The first NC&S were developed in the 1960s-1970s since conventional industry standards
in those days were not adapted to meet the requirements of the nuclear industry, in particularin terms of quality control (QC) and quality assurance (QA). A number of countries withdomestic nuclear power programmes developed NC&S (sometimes for specific reactor designs)

6.

100

This includes, for instance, their capabilities to prevent accidents and/or limit the radiologicalconsequences of accidents should they occur.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

to primarily serve their national industrial needs. Some examples include Boiler and Pressure
Vessel Code (BPVC) Sections III and XI of the US American Society of Mechanical Engineers(ASME), and the French “Règles de Conception et Construction” (RCC) series, developed by
AFCEN. 7 In some countries, specific NC&S are mandated by national nuclear regulations(e.g. ASME BPVC in the United States and Slovenia).
At the same time, supplying nuclear-grade SSCs requires the supplier to establish a nuclear
QA programme (e.g. ASME NQA-1) with the corresponding certification. In some cases, thiscertification needs to be renewed periodically (e.g. in the United States). This results insignificant qualification efforts for the suppliers, which require a sufficiently large order bookover time to become economically attractive. 8
The diversity of NC&S poses a challenge for the nuclear industry. Running a nuclear QA
programme for a specific NC&S allows the supplier to only produce SSCs that comply with one
specific set of rules, which artificially limits the available pool of suppliers.

5.2.2.Global trends and challenges for LTO
The nuclear industry is composed of more than 100 companies, providing key nuclear SSCs
worldwide (WNA, 2020). A significant number of suppliers produce nuclear-grade valves, pumps,
I&C systems and piping. These SSCs can also be found in other industrial sectors, which
increases market opportunities for suppliers. Companies supplying heavy conventional SSCs
(e.g. turbines) and SSCs for the nuclear steam supply system (e.g. vessel head, steam generators)
are less numerous, resulting from both a need for economies of scale and lower demandprospects for such specific components. Over time, competitive pressures have led to higher
levels of consolidation and localisation in the nuclear supply chain (NEA, 2015). Europe, Japanand the United States represent together more than 65% of the world’s nuclear fleet (IAEA, PRIS)
and these regions still have local suppliers for all of the key SSCs. The size of the industry is also
proportional to the installed capacity (see Figure 5.3). While the industry remains weighted
towards domestic markets, most of the leading vendors are internationally diversified in termsof corporate make-up and supplier structure.

Figure 5.3: Main nuclear suppliers by region and component versus installed capacity (left)and distribution of main suppliers in the European region (right), 2020
40

140

35

120

8%

100

25

80

20

60

15

GW

Number

30

8%

43%

14%

40

10

20

5
0

0
EuropeNorth
America

RPV head
Pumps
ValvesSG
TurbineCapacityJapan
Piping
I&C

14%
13%
FranceGermany

Czech Republic
Spain

UK
Other

Source: OECD/NEA, using data from WNA (2020).

7.

“Association française pour les règles de conception, de construction et de surveillance en exploitation
des matériels des chaudières électro-nucléaires”.

8.

Experience from the United States after the Three Mile Island accident shows that suppliers can drop
their QA programme in the absence of favourable market prospects.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

101

OPERATIONAL AND HUMAN ASPECTS

Thus far, this industrial base has enabled LTO for more than 30% of the existing nuclear
fleet and provided a constant inflow of components for regular maintenance. This volume ofactivity has also served to develop significant industrial capabilities for LTO projects, which
has led to a low risk profile that increases the economic attractiveness of LTO projects (seeChapter 6). Around 140 reactors are projected to undergo licence extensions, representing
USD 4 billion of investments per year on average (i.e. 30% of the total nuclear investment
levels as of 2020) until 2040 (WNA, 2020). These projections will positively contribute tosustaining industrial capabilities over time.
Some regions are nevertheless facing reduced market perspectives (i.e. early capacity
retirements) that, combined with the high qualification needs and policy uncertainties, areincreasing nuclear supply chain challenges in two ways:•

SSC obsolescence: A significant number of original equipment manufacturers (OEMs)
have stopped producing nuclear-grade SSCs or have even left the nuclear sector
altogether. For some critical SSCs, the OEM may even no longer exist. This is the case inparticular for analogue I&C systems of nuclear power plants. (IAEA, 2016). Consequently,
utilities are increasingly confronted with obsolescence issues that could become morecritical in the near term, in the absence of strategic measures and with an increasing
number of reactors being operated for longer periods.

•

Reduced pool of qualified suppliers and the difficulty to find new suppliers: There wereabout 400 companies holding an N-type certificate from ASME in 1980, mostly in the
United States. Today, most N-type certificate holders are found outside the United States,
and the overall number has been in steady decline by about 5% per year since 2013, from
395 to 270 in 2019 (WNA, 2020). Furthermore, the regulatory hurdles to adopt modern
state-of-the-art technologies for safety-classified SSCs in nuclear power plants poses abarrier to entering the nuclear sector for the suppliers of such technologies. Modern
state-of-the-art technologies may only be deployed for safety-classified SSCs after
extensive qualification and their inclusion in existing NC&S.

Figure 5.4: Companies holding an N-type ASME qualification, 2006-2019
450
374

400

Number

380
340

331

350

323

308

270

300
250
200

395

173

180

2006

2007

196

294

270

221

150
100
50
0
2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

Source: OECD/NEA, using data from WNA (2020).

These supply chain challenges are forcing nuclear operators to postpone replacement and tochoose “elaborative maintenance” and repairs of installed SSCs as the preferred strategies. If“elaborative maintenance” is not possible, operators need to replace installed SSCs, preferably as
like-for-like replacement, which could involve reverse engineering, if necessary. Replacementwith modern SSCs of improved functionality (not like-for-like) could be an option if this leads toadditional benefits in terms of functionality and costs. This option normally requires lengthy
design modification and associated equipment qualification processes.

102

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

It is important to highlight that not all countries are equally affected by supply chain
challenges (Martin, Abbt, 2020). Depending on the configuration of their nuclear fleet in termsof installed capacity and standardisation levels, a great variety of situations, strategies andeven specific opportunities exist (see Box 5.2).

Box 5.2: The role of the size of the nuclear fleet and standardisation levels in the supply
chain: Overview of national opportunities and challenges
Existing nuclear capacity was developed through the adoption of different national strategies that may haveconsequences in the supply chain today. Those countries that envisaged large nuclear programmes had strong
economic incentives to build domestic capabilities as a way to reduce costs while boosting the national economy.
Around 45% of nuclear suppliers in Europe are from France (see Figure 5.4), the country with the largest nuclear
fleet in Europe. At the same time, building large numbers of the same reactor is an opportunity to harness thebenefits of standardisation. Standardisation is an industrial strategy aimed at increasing the efficiency of the
supply chain through the homogenisation of design and transactions. Productivity and quality levels are thus
substantially increased by the greater volume of production of identical components. Qualification needs are also
limited to a unique standard, which enables the development of a larger pool of suppliers, as well as long-term
contracting.
On the other hand, countries with reduced nuclear construction plans found it more convenient to takeadvantage of foreign supply chains with more developed capabilities. While this provided a clear economic
advantage by avoiding the huge costs associated with the development of domestic nuclear power plants,
these countries became dependent on technology suppliers and their NC&S.
In general, countries with low installed capacity, involving different reactor designs and/or single-unit nuclear
power plants, are the most vulnerable to supply chain risks. In contrast, countries operating large nuclear fleetsof standardised reactors are far less affected. In these countries, orders are larger in volume, more frequent andmore predictable. Experience shows that high levels of standardisation offer significant business opportunities
for suppliers. Two bounding cases can be found, with a variety of national realities and strategies in between:•

Small nuclear programmes mainly with single-unit nuclear power plants and different reactor designs.
Examples are Switzerland (LWRs) and Argentina (PHWRs).

•

Large nuclear programmes with multi-unit sites having the same or similar reactor designs. Examples are
France (PWRs) and Canada (PHWRs).

Small nuclear programmes mainly with single-unit nuclear power plants and different reactor designs
Switzerland (LWRs)
As of 2020, Switzerland operated four nuclear reactors at three sites, representing a total of 3 GW of installedcapacity:•

Gösgen: Siemens-KWU PWR 1 100 MWe;•

Beznau units 1 and 2: Westinghouse, PWR 2 Loop 2 x 365 MWe;•

Leibstadt: GE, BWR 6 Mark III, 1 220 MWe.

Swiss reactors respresent different LWR designs from different vendors. Gösgen nuclear power plant was
designed and built according to German KTA standards, which were no longer developed following the nuclear
phase-out decision in Germany. Beznau and Leibstadt were designed according to the American ASME Boiler andPressure Vessel Code (BPVC). Consequently, Switzerland is a country where a small number of reactors of different
designs and NC&S cohabit, creating a challenging context for the supply chain.
Existing, preventive maintenance strategies and procurement processes are facing increasing obsolescenceissues, which is requiring more efforts than in the past. In most cases, the original equipment can be procured,
but reverse engineering approaches have already been used in the past for specific SSCs.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

103

OPERATIONAL AND HUMAN ASPECTS

Swiss regulations also allow for the use of non-nuclear industrial standards for SC3 components as long as theoriginal design is based on such standard. Further, industrial experience already exists with these types ofapproaches. The use of alternative NC&S to ASME BPVC and KTA standards for SC1 and SC2 SSCs could also beenvisaged, but it would require additional efforts to demonstrate the compliance with design rules. Swiss
utilities have also adopted a common supply chain management strategy with the objective of increasing
bargaining power, economies of scale and scope, and of enabling more competitive orders.
Argentina (PHWRs)
Argentina has three PHWRs, Atucha I, Atucha II (both Siemens-KWU) and Embalse (CANDU reactor), run by thestate-owned company, Nucleoeléctrica Argentina S.A. (NA-SA). One of the most recent projects was the licenceextension of the Embalse unit for 30 additional years. Since its inception, the Argentinian nuclear energy
programme has promoted high levels of local participation, despite the reduced number of projects. The
Embalse LTO project was thus essentially designed to be executed using local capabilities.
The main challenge was to convince local suppliers to qualify their processes so as to produce nuclear-grade
components, especially after a 12-year hiatus from nuclear construction. The Argentinian government rapidly
introduced an attractive policy framework that encouraged suppliers to ramp up nuclear capabilities based onnew, future perspectives. At the same time, NA-SA adopted a project strategy that included the qualification
process in the contracts with the main suppliers. The selected companies were required to obtain a certificate
of authorisation to start the manufacturing of nuclear components (ASME from the United States or TSSA from
Canada). Throughout the process, the suppliers were technically assessed by the design provider as part of thetechnology transfer agreement, which was surveyed by the owner with permanent QC at the shop, andaudited by the regulator during key milestones. The project also benefited from experience gained in theconstruction of the Atucha II reactor.
As a result, activities such as steam generator and moderator heat exchanger replacements and balance-ofplant modifications were implemented with less than 15% of foreign support specialists. The personnel werealso trained using 1:1 scale mock-ups, and supervised by NA-SA for critical welding and tubing conforming
processes. These localisation efforts increased the overall costs of the project compared to other PHWR
refurbishments, but they should bring long-term benefits for future nuclear projects (e.g. LTO of Atucha II).
Large nuclear programmes with multi-unit sites having the same or similar reactor designs
France (PWRs)
In total, France has 56 reactors in operation with an installed capacity of 61.3 GW. One of the uniquecharacteristics of the French nuclear fleet is its high level of standardisation, with the development of three
generic PWR series 9 of 900 MWe (32 reactors), 1 300 MWe (20 reactors) and 1 450 MWe (4 reactors). Different
designs cohabit within each series, but the differences are very limited (i.e. position of the turbine hall), which
ensures the overall standardisation of the series.
The French regulatory framework imposes an in-depth periodic safety review (PSR) every ten years to renew
the operating licence. PSRs typically require new safety studies and the implementation of safety upgrades,
which results in a significant amount of work that is easily predictable by the suppliers, thus mitigating supply
chain risks.
Furthermore, most of the reactors in the 900 MWe series are set to operate until 50 years upon the requirements
specified by the French regulator (ASN, 2021), with additional LTO investments already undertaken. Work tosecure a 10-year licence from 30 to 40 years of operation for the 1 300 MWe series is also underway. EDF decided
to structure all these activities under a specific programme called the “Grand Carénage” (i.e. the “Major Refit”),
gathering around 20 projects with a total investment of EUR 49.4 billion (EDF, 2020). This programme takes fulladvantage of the standardisation benefits in relation to the French fleet thanks to:••

generic studies and proposals for modifications by series;
generic regulatory oversight by series, complemented by on-site verifications and authorisations for each
unit;

•

long-term contracts with key partners for several units.

9.

104

A fourth series is under development with the construction of the first EPR, Flamanville 3.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

The Grand Carénage is also an opportunity to boost the national economy while also benefiting from the skills
and expertise developed by the French nuclear industry over many years. EDF engineering centres placeorders with local or nationwide industrial partners, establishing long-term partnerships with thesecontractors. 10 Given the size of the internal market, EDF can also adopt strategies aimed at finding acompromise between sustaining domestic capabilities while increasing competition to reduce costs. In fact,
French companies often bid alongside foreign suppliers for EDF offers.
Canada (PHWRs)
As of 2020, Canada had 19 nuclear reactors in operation, representing an installed capacity of 13.5 GW. These
reactors are distributed among four main nuclear sites. The Canadian nuclear programme is based on thedomestic PHWR CANDU design. The two biggest nuclear power plants in the country in terms of capacity are
the Darlington (3.5 GW) and Bruce (7.8 GW) nuclear power plants. Both host CANDU reactors with power
outputs between 750-900 MWe and with important levels of design standardisation.
Both nuclear power plants are planned to undergo major refurbishment in order to enable operations for 30
additional years, for a total cost of CAD 24 billion. Works started at Darlington unit 2 in 2016 and are scheduled
to finish by 2026 with unit 4. Refurbishment at the Bruce nuclear power plant will take place between 2021
and 2033 and will involve six units. The period of highest stress for the supply chain corresponds to 2021-2024,with five reactors simultaneously undergoing major refurbishment. The two main nuclear operators in the
country, Ontario Power Generation and Bruce Power, have already expressed their shared desire to work in aco-ordinated manner so as to enhance supply chain performance and minimise potential risks (Bruce Power,
2016). Areas of collaboration include sharing lessons learnt on retubing activities, leveraging economies ofscale through joint procurement, the creation of shared tooling for CANDU refurbishments, and schedulingand critical resource planning optimisation to avoid supply bottlenecks.

5.2.3.Enhancing supply chain capabilities for LTO
Increasing nuclear supply chain challenges could seriously hamper the ability of some countries
to ensure the LTO of nuclear power plants. International safety standards such as those developedby the IAEA already include guidelines to effectively deal with the obsolescence of safety-related
SSCs (IAEA, 2018). As part of the LTO-programme, operators can also adopt a programmatic
approach, allowing for the identification of obsolete SSCs and the implementation of maintenance,engineering and supply chain management strategies. Their objective is to increase the pool of
suppliers and drive costs down through keener competition, while maintaining (or evenincreasing) the quality and reliability of SSCs. The selected approaches may vary depending on
the safety class (and thus the QA standards) of the SSCs, as well as on the situation of the country,
as described in Box 5.2.

Increasing the number of industrial/commercial grade components
A growing number of utilities are using commercial components and equipment to operate
as safety-classified SSCs, thanks to the introduction of commercial-grade dedication (CGD).
This process provides reasonable assurance that the commercial item (i.e. the industrialgrade component or equipment) delivers its safety function when used in a nuclear facility.
The dedication process is normally performed by the utility or a competent third-party
organisation acting on behalf of the utility. 11 CGD enables companies that normally do not
produce nuclear-grade items to supply the nuclear sector, without the need to run a costly
nuclear QA programme, hence increasing the pool of suppliers for utilities. Table 5.1 provides
an overview of QA requirements for nuclear-grade items versus commercial items.

10. The tube heat exchangers installed at the Tricastin-1 unit as part of its fourth decennial outage were
manufactured, for example, using a new high-tech alloy developed in Lyon. A factory located in MantesLa-Jolie was in charge of the production of several nuclear-grade pumps that were replaced in the reactor.
11. Typically, reactor vendor companies running a nuclear QA programme.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

105

OPERATIONAL AND HUMAN ASPECTS

Table 5.1: Potential classification of nuclear components according
to their quality assurance requirements
Nuclear-grade components
Safety-classified items

Industrial-grade components

Safety-significant items

Enhanced quality assurance programme is mandatory.

Quality assurance programme may
be required.

Production process is subject toinspection verification or testing.

Good commercial practice required.
Analysis of past performancerequired.

Defects or non-compliance must bereported and corrected.
Performance testing according to
specified codes or standards isrequired.

Performance testing according to
special codes or standards is required.

Performance testing according to
specified codes or standards may berequired.

Source: Adapted from NEA, 2015.

The Slovenian utility, NEK, operating the single-unit Krško nuclear power plant, is a good
example to demonstrate the benefits of a well-established CGD process. 12 Utilities andlicensees in the Czech Republic, Finland and Sweden are currently implementing CGD andrunning the corresponding pilot projects in close interaction with regulators (see Box 5.3
below). Swiss utilities (see Box 5.2) and the Belgian utility ENGIE-Electrabel have also
undertaken some CGD trials in the past for a limited number of SSCs. These initiatives provide
valuable experience for utilities seeking to enhance their supply chain capabilities for LTO
through CGD processes. It is nevertheless important to highlight that CGD requires regulatory
approval, and existing nuclear regulations may need to be adjusted in most countries before
CGD becomes a common practice in the nuclear industry. 13

Box 5.3: The KELPO projectAs part of the discussions on the necessary preconditions for LTO in Finland, in 2018 the industrial consortium ledby the Fortum, TVO and Fennovoima utilities launched the KELPO project. Its main objective is to reinforce
national supply chain capabilities by developing new procedures to license and qualify high-quality industrial
SSCs for nuclear installations, based on the experience of other industries (Fortum, TVO, Fennovoima, 2019). Thisinitiative benefits from the approval of the national Finnish regulator, STUK, also participating as an observer.
The KELPO project consists of three phases. Phase 1 was finalised in 2018 and led to a potential redefinition of
responsibilities with regard to the supervision of the manufacturing and QC/QA of safety-classified SSCs as
shown in Table 5.2. While the regulator, STUK, will continue to have a leading role at the plant and systemlevels for SC1 and SC2 SSCs, the proposed framework encourages utilities to take a more active role in theprocess, especially for low SC SSCs and at the device level. For SC3 devices and components, the utility could
be fully responsible with the option of involving a specialised third-party organisation.

12. NEK has been successfully using CGD processes since 1995. It follows EPRI guidelines consistent with
US practice and other international nuclear industry groups dealing with SSC obsolescence andsearching for dedicated solutions. As a result, NEK has considerably mitigated supply chain challenges,
despite operating only a single unit nuclear power plant.
13. The use of non-nuclear SSCs for low SCs may be possible after additional specific testing (e.g. seismic
standards), but higher SCs will continue to require additional efforts.

106

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

Table 5.2: Proposed new roles for regulatory approvals of plant-, system- and device level design andmanufacturing oversight for nuclear SSCs according to the KELPO projectNote: The authorised inspection organisation is an organisation that conducts tasks related to theconformity assessment, and approval of the design and manufacturing of components andstructures in nuclear facilities on behalf of the regulator, which in this case is STUK.
Source: Martin, Abbt, 2020.

Additional outcomes of Phase 1 include measures such as:•

Increasing collaboration among national utilities (similar to the Canadian case in Box 5.2);•

Avoiding duplications;•Utilising common approvals;•

Defining common and coherent documentation for safety-classified SSCs;•

Developing a qualification and dedication process with a focus on SC2 and SC3 SSCs.

The aim of phases 2 and 3 is to prove the viability of the new qualification and dedication process in relation
to a number of selected components, such as a valve (i.e. mechanical component), a battery (i.e. electricaldevice) and pressure transmitters (i.e. automation devices). The experience gained should then be used todevelop a common qualification and dedication process for all Finnish utilities. Moreover, the evidencecollected by STUK throughout the different phases of the KELPO project could inform potential adjustments
in terms of Finnish regulations.
Lastly, the KELPO project also represents a great opportunity to engage with other interested countries(e.g. Sweden) and make additional contributions towards more harmonised licensing practices at the EU level.

Since CGD processes shift dedication activities away from the supplier to the utility, or to athird-party organisation, some upfront investment by utilities may be required to build thenecessary skills for their adoption. These efforts should nevertheless be outweighed by thebenefits over the long term. Another possibility is to perform CGD processes for individualcomponents and equipment in a collaborative and cross-border manner, involving utilities fromdifferent countries. This could include, for instance, the joint issuing of technical specificationsfor SSCs to be procured and data sharing of qualification and dedication tests.
Lastly, the use of high-quality, non-nuclear industry standard components and equipment
for safety-classified SSCs in nuclear installations could bring benefits for nuclear safety. Risks
and additional costs for first-of-a-kind designs could be avoided as suppliers are allowed to use
the industry standards and manufacturing methods with which they are most familiar. The
possibility of common cause failures could also be reduced given the potential opportunities todeploy commonly used components and equipment with long-term experience from otherindustries. More importantly, the timely and correct replacement of SSCs could be facilitated,
reducing the number of unexpected shutdowns and improving the overall safety and reliabilityof nuclear power plants.

Higher collaboration and harmonisation levels
Utilities planning to undertake major refurbishments should consider working closely with key
suppliers from the early stages of the LTO programme as a way of anticipating and mitigating
supply chain risks. Recent experience from countries like France (see Box 5.4) and from new

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

107

OPERATIONAL AND HUMAN ASPECTS

nuclear build 14 show that collaboration between utilities and suppliers is a key factor of success,especially for companies that are new to the nuclear industry. Contracts between utilities andsuppliers can be designed with the right incentives so as to drive the performance of all the
involved parties and not simply to primarily protect the individual interests of the companies
when issues arise (e.g. quality flaws). The commercial interests of stakeholders also need toremain aligned throughout the project in order to avoid adverse impacts on delivery.
In parallel, greater collaboration can be pursued as a way to increase the competitivenessof the supply chain, particularly for high SC SSCs. Utilities in different countries could explore,
for instance, the joint cross-border qualification of suppliers in order to avoid any duplicationof efforts. SSCs with a good operational record should be easily transferable to other countries(if they technically fit into the plant system configuration) with fewer extra qualification
efforts, which could ultimately result in several NC&S being used in the same country or evenin the same nuclear power plant. While mixing various NC&S is, in general, not consideredgood practice, there may be no other option in some cases. 15 The use of different NC&S issomething already being done in Belgium, and the corresponding regulatory guidance exists.
At the same time, the adoption of SSCs that have been produced with alternative NC&S is notformally forbidden in most countries. Extensive work, however, is likely to be required toprove to regulators that alternative NC&S can deliver similar SSC quality and reliability
without compromising safety (Martin, Abbt, 2020).
Another option involves increasing harmonisation levels of existing NC&S throughinternational collaboration. In general, the different NC&S are similar in scope but differ in thedetail of and emphasis on certain items. At the same time, there is a general understanding thateach NC&S is a complete set of rules on its own basis, whose sections are interrelated andinterdependent. In this sense, complete harmonisation may be unrealistic – and in somerespects, undesirable. It is possible, however, to identify some areas where meaningful common
positions can be achieved. Three major, ongoing international harmonisation initiatives include:•

Cooperation in Reactor Design Evaluation and Licensing (CORDEL): Since its creation by
the World Nuclear Association in 2007, this initiative has made significant efforts tobenchmark existing NC&S and identify potential areas of harmonisation. CORDEL also
works closely with the Standards Development Organisations Convergence Board 16 toachieve greater convergence of existing NC&S.

•

CEN Workshop 64: This project is run under the umbrella of the European Committee forStandardization (CEN) 17 with the purpose of making recommendations on the further
evolution of AFCEN codes (i.e. the French RCC series) and the required underlying research.
The CEN Workshop 64 opens up the development of the AFCEN codes to the nuclear
stakeholders of other EU member states in order to achieve higher levels of versatility.

•

Nuclear Quality Standard Association (NSQA): Founded by Bureau Veritas andFramatome (formerly AREVA NP) in 2010, NSQA efforts have resulted in the publicationof ISO 19443. This standard provides specific requirements to suppliers of safety relevant
SSCs in relation to the application of ISO 9001 (Naden, 2018) and combines the bestpractices in quality management, including ISO 9001:2015, IAEA GSR part II and ASME
NQA-1. ISO 19443 also harmonises a minimum level of requirements, covering many
regulatory, industrial, national and international rules. As most companies are familiar
with the ISO 9000 standards family, the qualification process and subsequent audits areaccelerated. In order to achieve wide applicability of ISO 19443, further efforts may beneeded in the accreditation process of certification bodies, implementation oversight
among different tier suppliers and the definition of a wider set of criteria for qualification.
Management of this process by the industry, with the endorsement of regulatory bodies,
is a key element for the possible implementation of the quality management standard.

14. This is the case, for instance, for the Hinkley Point C EPR project in the United Kingdom (Owen, 2018).
15. For example, if the nuclear power plant design is based on a NC&S that is no longer maintained. Thisis the case of German designs using KTA standards.
16. An assembly of standard development organisations, including ASME and AFCEN.
17. The acronym represents the French “Committee European pour Normalisation”. This organisation is incharge of developing and maintaining European standards.

108

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

Supply chain management considerations
Supply chain management starts at the nuclear power plant operator level. Maintenance andprocurement services should include processes and methodologies to continuously evaluate
existing stocks of spare parts for critical SSCs, identify and track obsolete components andrenew suppliers when necessary. Good practices also cover the development of strategic
contracts to sustain the capabilities of key suppliers, and securing a hoarding stock by buying
appropriate quantities of key items if the supplier plans to cease production.
A single player in the market, operating just one or two nuclear reactors, may find somedifficulties in generating enough demand to create attractive market conditions. This low
bargaining power could potentially lead to higher prices, and thus the overall competitivenessof the company is undermined. Under such circumstances, various utilities can join forces todevelop a common supply chain strategy in order to avoid work duplication, streamline
processes and set new standards for supply chain management, as well as reduce costs andshare risks through economies of scale 18 and scope. 19 Joint supply chain strategies have beendeveloped in Canada (see Box 5.2) and are one of the key findings of the KELPO project toovercome supply chain issues (see Box 5.3).

Reverse engineering and plant modernisation
When the specific SSCs created by the original equipment manufacturers (OEMs) are no longer
available in the market and/or the aforementioned measures do not yield the expected results,
utilities can also envisage two additional strategies: reverse engineering and plant modernisation.
According to EPRI, reverse engineering can be defined as “the process of developing technicalinformation sufficient to duplicate an item by physically examining, measuring, or testing existing
items; reviewing technical data; or performing engineering analysis”. Guidelines already exist on
how to perform reverse engineering in nuclear power plants (EPRI, 1998). The process starts in asimilar manner as that of procuring any other item (e.g. choosing a supplier, defining technicaland quality requirements), but requires close collaboration between vendors or suppliers andoperators to collect high-quality information concerning the component so that it can be reverse
engineered. 20 If this information is not available, additional exams and measurements may beneeded. Therefore, replacements based on reverse engineering approaches typically cannot be
considered as like-for-like replacements, and additional item equivalency evaluations arenecessary (IAEA, 2016). For these different reasons, reverse engineered components may come at
an important cost penalty for one single nuclear power plant. The emergence of new
manufacturing and digitalisation technologies (e.g. additive manufacturing) is also increasing theattractiveness of reverse engineering approaches. In the Krško nuclear power plant in Slovenia, a
3D-printed impeller for a fire protection pump was manufactured using design data collected
through the examination of obsolete components (WNN, 2017).
In some cases, the most cost-effective alternative for operators is to undertake major
modernisation programmes in order to introduce new components consistent with the latest
state-of-the-art technology, which provides more functionality and is supported by a larger
pool of suppliers (e.g. replacing analogue by digital I&C). As highlighted in Chapter 3, plantmodernisation approaches can also bring cost and reliability benefits. Proposals should
consist of solid economic justifications and risk assessments associated with the introductionof the new technology.

18. Reduction of the unit cost of a product or a service based on the inverse relationship between thevolume of production and fixed costs per unit in a company. Utilities undertaking a common supply
chain strategy can reduce the incidental cost for both the contractor and the purchaser as a result of anincreased demand of products and services. The specific tooling and machinery necessary for LTO
refurbishments can also be developed jointly and amortised through a greater number of projects. The
higher volume of joint orders also increases the bargaining power of utilities, potentially leading tomore attractive prices for SSCs.
19. Economies of scope occur when producing a wider variety of goods or services in tandem is more costeffective for a firm than producing less of a variety, or producing each good independently. Utilities canshare the costs of developing diversified suppliers, providing the variety of products necessary for LTO.
20. Typical information includes the original procurement specification, drawings, historical performancedata, operating environment conditions and interfaces with other systems.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

109

OPERATIONAL AND HUMAN ASPECTS

The use of modern, state-of-the-art technologies (e.g. additive manufacturing, advanced
analytics) for safety-related applications is only possible if these technologies are alreadycovered by the applicable NC&S, or have undergone an extensive qualification process. Their
adoption may be easier for low SC SSCs not belonging to the nuclear island (Martin, Abbt, 2020).

5.3. Nuclear workforce and competence assessment
Supply chain concerns related to the production of safety-classified SSCs can also be extended
to the nuclear workforce. Similar to the aforementioned high qualification needs, excellencein nuclear skills requires time, investment and training. While operators and regulators havebeen somewhat successful in planning and replacing an ageing workforce, 21 attracting andretaining the best talent is becoming more difficult given increasing political uncertainty anddegraded perspectives in the nuclear sector. The situation could worsen as longer operational
lifetimes are being envisaged, ultimately undermining the ability of operators to sustain
operational excellence and economic performance. Again, aspects such as the scale of thenuclear programme can facilitate human resource management. However, the particularcharacteristics of nuclear knowledge need specific long-term strategies at all levels to ensure
the timely availability of a skilled workforce. Many international organisations have been
active over the years, attempting to foster collaboration in nuclear human resource planning,knowledge management and building robust international academic networks.

5.3.1.Nuclear knowledge and knowledge management
Working in the nuclear industry is a knowledge-intensive activity. A significant amount of training,
specialised studies, experience and managerial skills is required in order to perform at the highest
levels of safety and quality expected by the industry, regulators and the public. Operating andmodernising a nuclear power plant, in particular, involves considerable skills and interrelated
disciplines 22 that, in most cases, require long time frames to be properly mastered. 23 The highlevel of technical and managerial skills is not limited to the nuclear power plant itself, and must
be extended to regulators and suppliers that ensure excellence throughout the entire value chain.
A closer look at the different types of education, qualification and skills needed in the nuclear
energy sector leads to the following classification of the nuclear workforce (see Figure 5.5):•

Nuclear-aware: generic skills gained through vocational training or professional
qualifications;•

Nuclearised: a tertiary education in science, technology, engineering and mathematics(STEM) disciplines;•

Nuclear: specialists who have a tertiary education qualification in nuclear energy andnuclear-related subjects, and who possess specialised skills that take a considerable
amount of time to acquire. These specialists include leading experts who have developed
broad knowledge and experience in the nuclear field and are able to tackle challenges
and resolve problems, as well as steer and lead organisations.

Efforts are required at all levels of the pyramid to sustain nuclear capabilities over time. Thelong cycles associated with nuclear knowledge are, moreover, particularly unique and needspecific planning. A nuclear power plant engages a local community for around one century,with the operating phase representing 60 years 24 or more, if LTO is undertaken. This time frame
is longer than the professional career of a single person. Human resource planning andknowledge management thus become critical at some point in the life of a nuclear power plant.

21. Similar to supply chain issues, countries with a small nuclear fleet, with an uncertain policy and market
context, may generally face more difficulties in replacing an ageing workforce.
22. Fundamental and nuclear physics, plant operation, fluid mechanics, thermo-dynamics, chemistry,materials science, electricity, electronics, etc.
23. Nuclear experts generally hold high-level qualifications, such as an MSc or PhD.
24. Including the preparatory and infrastructure development phases (10-15 years), construction (5-10 years),
operation (60 years) and decommissioning (15-20 years).

110

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

According to the IAEA (2012), knowledge management is “the integrated, systematic
approach for identifying, managing, sharing and transferring an organization’s knowledge
and enabling persons to create new knowledge collectively and thereby help achieve theobjectives of that organization.” One of the main challenges of transferring knowledge is thatmost of this knowledge is generated in a tacit 25 manner within organisations (Dudézert A. et
al. 2012). Tacit knowledge is the result of experience, trial and error, human interactions andwork practices, and thus it is inseparable from individuals and difficult to transfer. Whenpersonnel leave an organisation, the loss of human capital can lead to operational disruptions
and lower performance. Consequently, those organisations that rely heavily on knowledge
are more vulnerable and require a critical mass of activity that ensures a constant inflow ofskilled workers in order to minimise the risks associated with turnover (NEA, 2020). Countries
with large nuclear programmes may face less difficulties in maintaining an adequate volume
of work to sustain skills. Knowledge management can also be used to properly mobilise people,
technologies and processes to effectively transfer tacit knowledge to new staff.

Figure 5.5: Pyramid of competencies and skills
for the nuclear industry workforce

Source: NEA, 2020.

5.3.2.Global trends and challenges
As a general trend, the workforce in the nuclear field is ageing. Personnel that gained uniqueexperience during the commissioning and operation of the nuclear fleet in the 1970s and 1980s
have already retired or are close to retirement. The majority of the workforce is older than
40 years of age, and it is estimated that around 20% of the workforce will retire in the next 10 to
20 years (NEA, 2020b). Retirement, however, is not specific to the nuclear power industry, as it
affects every industry and can be properly managed if planned in advance. What requires
specific attention in the case of the nuclear sector is the high reliance on knowledge across thevalue chain, which may exacerbate operational issues induced by retirement.
To date, there is evidence suggesting that the nuclear industry has been capable ofrenewing its personnel and transferring knowledge generated over the years. A survey
performed by the Nuclear Energy Institute (NEI) in 2015 for the US nuclear industry showed abroadening of age distribution, with the number of employees in the 48- to 57-year-old range
in continuous decline (Reuters, 2015). In France, EDF has also been successful in overcoming
retirement issues by assessing workforce ageing over the past 15 years and by ensuring active
recruitment and training (Fillon, 2019). In parallel, global performance indicators continue toimprove (see Figure 5.2), indirectly supporting these trends.

25. Conversely, knowledge can also be explicit. Explicit knowledge is codified in books, archives, drawings,
etc., and it is easily storable, retrievable and reproducible. Nuclear organisations have thus far beensuccessful in making knowledge more explicit.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

111

OPERATIONAL AND HUMAN ASPECTS

The main issue for the nuclear industry is related to the capability of the sector to attract andretain the best talent. Some nuclear operators have reported a reduction in the number ofapplicants for a given position of more than 60% compared to 2010 levels (Fillon, 2019). The lackof nuclear graduates has been a growing concern since 2000. However, a detailed quantitative
analysis at the OECD level is difficult to find (NEA, 2020b). Such patterns arise from a combinationof several factors. First, the legacy of nuclear accidents in public acceptance and difficulties
encountered in recent new build projects have contributed to creating a bad reputation for nuclear
power. At the same time, strong policy support to other low-carbon technologies has resulted innuclear energy being perceived as an outdated technology. Second, the increasing politicaluncertainty following the Fukushima accident, and reduced market perspectives induced by
nuclear phase-out in some countries, makes it more challenging to recruit new personnel. Third,
increasing market pressures are forcing utilities to reduce the budget associated with building
internal competence and proposing more attractive job offers. The situation is not uniform acrossall NEA countries, and depends to a great deal on the national context.
On the other hand, the number of STEM graduates is steadily increasing (see Figure 5.6), andtherefore the potential pool of young professionals willing to pursue a career in the nuclear
sector. In the United States, the number of nuclear graduates has also been growing since 2000,
suggesting that it is possible to sustain the talent pipeline with specific, co-ordinated efforts
between industry, government and academia (NEA, 2020b).

Figure 5.6: Evaluation of the total number of STEM
graduates in NEA/OECD countries

Source: OECD, 2018.

Lastly, attracting and retaining the best talent in the nuclear sector will also require abetter understanding of generational issues. In the coming years, the global workforce will
essentially be formed by millennials (i.e. the generation Y 26 ), followed by an increasing
number of generation Z staff 27. Compared to their predecessors, these generations change
jobs more frequently. According to a survey from Deloitte (2018), 43% of millennials expect toleave their organisations within two years. Only 28% plan to stay beyond five years. These
numbers get worse with younger generations, with only 12% of generation Z indicating thatthey would be likely to stay in an organisation beyond five years. Evidence from the United
Kingdom suggests that, while a high salary remains central in attracting young professionals
to the nuclear industry, job satisfaction and progression are the main motivations to stay in
a given company (YNPF, 2018). The higher turnover rates associated with generations Y and
Z personnel are however inconsistent with the long timescales required for the development
and transfer of nuclear knowledge. New technologies that would enable the enhancement ofknowledge management approaches and provide more sophisticated and rapid training could
help to overcome these issues.

26. People born in the 1980s and the beginning of the 1990s.
27. Young professionals born in early 2000s.

112

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

5.3.3.Building skills for LTO
Nuclear organisations have at their disposal a series of strategies to systematically assess theirinternal human capabilities so as to minimise potential performance risks. These approaches
are based on rigorous human resource development and management practices, investments
in communication and modern technologies, and knowledge management practices. Additional
efforts may be required at the national level with governments, industry and academia working
together to create a functional framework for workforce development, including R&D
investments, attractive university and training programmes and apprenticeship opportunities.
All of these measures can be supported with national plans, providing the right incentives tothe nuclear industry to invest in their personnel and reinforce international collaboration.

Human resource development and management
Human resource development strategies involve different aspects that are common to every
company, such as workforce planning, career management, remuneration, recruitment,
training and talent development. All these dimensions have to be taken into account to attract
not only the necessary resources but also the best talent to meet the high levels of excellencein the nuclear industry. Each nuclear organisation and facility should set up specificmanagement systems to identify any growing performance risks associated with the loss ofcritical skills, and then trigger the necessary countermeasures in due time. Early planning,proactive recruitment and reinforced education and training can be effective measures andshould be supported with continuous monitoring. In parallel, companies can also invest in
soft skills such as leadership (NEA, 2019), as well as talent identification and promotions thatconsider the motivations of younger generations.
Similar approaches can be adopted at the national level, with the elaboration of humanresource plans for the entire nuclear sector. These government-led programmes can be created inconsultation with industry and academia in order to properly address specific long-term capability
needs. France is a good example of this type of nationwide endeavour (see Box 5.4 below).

Box 5.4: Building nuclear capabilities at the national level: The case of France
Nuclear knowledge and skills require long-term planning and strategies. In light of the potential shortage ofskills for new build projects and LTO, France has been undertaking concerted efforts at all levels of the nuclear
value chain – involving the government, industrial key players and academia – to secure these skills in future.
Sustaining capabilities through national, industrial planning
The nuclear sector in France consists of around 2 600 companies, 50% of which have export activities, andgenerates 220 000 direct and indirect jobs. In order to provide a stable policy framework consistent with theenergy strategy, the main French representatives from government and the nuclear industry signed a nuclear
sector deal 28 in January 2019, which includes reciprocal commitments in four key areas (Conseil National del’industrie, 2019):•

jobs, skills and training;•

digital transformation of the nuclear sector;•

research and development and the circular economy (i.e. back-end activities);•

international market opportunities.

The deal also includes specific mechanisms to boost the development of small and medium nuclear
enterprises. The initiative followed the creation of the French nuclear industry platform called GIFEN 29 in 2018.
GIFEN gathers key nuclear industry players and other associations with the objective of co-ordinating industry

28. Contrat Stratégique de la Filière Nucléaire Française.
29

The acronym GIFEN stands for Groupement des industriels Français de l’énergie nucléaire, or in English,
Group of French nuclear energy industrialists.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

113

OPERATIONAL AND HUMAN ASPECTS

efforts in areas such as: skills and training, nuclear safety and quality, digital transformation and R&D,
development perspectives of the sector in France and abroad, European and international affairs andcommunication with the public.
Reinforcing nuclear curricula and R&D efforts
Since its creation in 1956, the public higher education institution, Institut national des Sciences et Techniques
Nucléaire (INSTN), has been training young engineers, researchers and technicians to support thedevelopment of the French nuclear programme. The INSTN is administered by the French Alternative Energies
and Atomic Energy Commission (CEA) and works in close collaboration with the industry in order to support
its workforce needs. As a result of this long-standing dialogue, the International Master of Nuclear Energy wascreated in 2009 with the objective of sustaining the talent pipeline, providing a specialised nuclear cursus toFrench and foreign high-level students in the following subject areas: fuel cycle, nuclear reactor physics andengineering, nuclear plant design, operations, decommissioning and waste management. Nuclear industry
professionals from EDF, Framatome and CEA also participate in the teaching. This master’s degree takes fulladvantage of a unique partnership between academia and industry to provide on-site specific training in
nuclear power plants and research laboratories, as well as attractive job offers in the most prestigious nuclear
companies for students willing to perform their career in the French nuclear sector.
Another success story of national and international industrial collaboration is the creation of the Materials
Ageing Institute (MAI). Founded by EDF in 2008, MAI regroups nuclear operators, reactor vendors and research
institutes 30 from all over the world to accelerate research in nuclear materials ageing. The main R&D areas
include all of the life-limiting SSCs and associated ageing phenomena covered in Chapter 3 of the present
report. The mission of MAI is to improve materials ageing simulation, bringing together materials scientists,
modellers and nuclear operators with actual operational data to improve the accuracy and accelerate thedevelopment of advanced simulation models and tools. Another key activity of the institute is to provide
training on materials ageing to students and young nuclear professionals (MAI, 2020).
Engaging young professionals through apprenticeships
Around 5 000 apprentices today receive hands-on training in nuclear organisations during their studies inFrance. These students have access to offers through a dedicated apprenticeship web portal that includes
the offers of approximately 2 500 companies. Around 25% of jobs offers in nuclear companies are filled byapprentices (RGN, 2017).

Communication and job advertisements
The difficulties faced by the nuclear industry in attracting new talent can be explained, to someextent, by limited advertisement efforts and the use of outdated communication approaches.
Countries that are willing to pursue the nuclear option could advertise the role of nuclear powerin their countries through public talks and visits to nuclear facilities as part of school education.
The boom of social media is also an opportunity to revisit current communication strategies so
as to update them with more modern, fresh and targeted content to increase the interest ofyoung graduates in nuclear jobs. In parallel, companies could participate more actively in local,
national and international job events. When organised locally, these events can strengthen therelationship with local communities and provide opportunities to better communicate thebenefits of nuclear activities in the local economy.

Know-how and know-why transfer
A starting point of any knowledge transfer plan is the elaboration of a comprehensive knowledge
map within the organisation to have a clear picture of who does what and anticipate potential
critical skills shortfalls. Specific knowledge management programmes can then be built around
critical knowledge areas, including activities to make knowledge more explicit (e.g. through the

30. MAI membership currently includes: EDF (France), TEPCO (Japan), EPRI (United States), Rosenergoatom(REA, Russia), EDF Energy (United Kingdom), China General Nuclear Power Group (CGN), Kansai ElectricPower Company (Japan), Mitsubishi Heavy Industries Ltd. (MHI, Japan), Central Research Institute ofElectric Power Industry (CRIEPI, Japan), CEA (France), Framatome (France), as well as a robust scientificnetwork of universities across these countries.

114

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

generation of expert documents and video recorded interviews), as well as the creation of specifictraining, mentoring and communities of practice 31 to properly handle tacit knowledge.
Also, it is important to differentiate “know-how” from “know-why” when transferringknowledge. While the former is limited to the generative processes of a given phenomenon,
the latter requires a deep understanding of the underlying physical principles. Know-how cantherefore be effectively transferred through training and knowledge management efforts as it
involves a “nuclear-aware” workforce and, to some extent, nuclearised personnel. However,know-why transfer requires complementary efforts in higher education in order to replace
nuclear specialists (see Figure 5.5).

Research and development, and higher education activities
Nuclear research contributes to building the knowledge base necessary for safe nuclear
operations over longer periods. Key areas of research to support LTO are materials ageing andplant modernisation (see Chapter 3). Research laboratories and industry can combine theirforces to accelerate research in these areas, combining scientific advances with actual plantdata. In 2008, MAI was created in France with the mission to develop more accurate predictivemodels (see Box 5.4). In the United States, the Light Water Reactor Sustainability Program (LWRS)
regroups utilities, regulators, universities, nationals and other international organisations todevelop the scientific basis, and science-based methodologies and tools, for LTO (LWRS, 2020).
The technical evidence generated by LWRS has been used to support the safety cases of recent
subsequent licensing renewals (SLRs) in the United States.
Moreover, research activities in combination with higher education programmes are
essential to provide highly specialised nuclear professionals (see Figure 5.5). Since the 1970s,
R&D investment has been steadily declining, suggesting decreasing academic activity 32 andnuclear expertise in some areas (see Figure 5.7). The industry and academia can work together
to establish a specific nuclear cursus that leverages existing research and nuclear facilities(e.g. on-site training, talks to nuclear professionals) to provide high-quality and attractive
educational experiences. Some examples include the creation of the Master of Nuclear Energy
at the INSTN in France (see Box 5.4) and the European Master in Innovation in Nuclear Energy(EMINE, 2020) at the European level. Post-doctorate schemes can be set up around the mostcomplex technical issues to reinforce capabilities. In countries that are planning to phase out
nuclear power in the near or mid-term, R&D and education become the main levers tosustaining nuclear capabilities given the expected lower commitments from industry.
Germany, for example, has not reduced R&D efforts in nuclear activities 33 despite its nuclear
phase-out. In 2019, investments in nuclear R&D represented 22% of the total budget, withsimilar amounts allocated to energy efficiency and renewables (IEA, 2021).

31. Networks of people who work on similar processes or disciplines, and who come together to develop
and share their knowledge in that field for the benefit of their organisation and themselves (IAEA, 2012).
A key advantage of communities of practice is that knowledge is managed collectively and thus is lessvulnerable to the turnover of its members.
32. Nuclear R&D budgets in IEA member countries represented in 2019 22% of the total R&D investmentcompared to 75% in 1974 (IEA, 2021).
33. The main research areas include: nuclear safety, waste management and disposal, basic sciences andnon-power applications, such as materials behaviour and fusion energy.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

115

OPERATIONAL AND HUMAN ASPECTS

Figure 5.7: Public energy technology R&D and demonstration spending
by IEA member country and by technology, 1977-2019
25 000

Cross-cutting,unallocated, other
Electricity andstorage

USD (2019) billion

20 000Hydrogen, fuelcells and CCUS

15 000

Nuclear

10 000

Renewable energy

5 000

Fossil fuels
Energy efficiency

0
1977

1987

1997

2007

2017

Note: Nuclear R&D includes nuclear fission and fusion activities. CCUS = carbon capture, use and storage.
Source: IEA, 2020a.

Apprenticeship opportunities
Apprenticeships are an efficient approach to mobilise both industry and education centres so
as to secure the necessary nuclear workforce in a mutually beneficial way. On the one hand,apprenticeship contracts provide graduates with hands-on experience to complement theiracademic background, which can also help to attract new students. On the other hand,companies benefit from additional and inexpensive resources that will be fully operational if
apprentices are selected for full-time jobs. Apprenticeships can be adapted to any type of degree
and qualification (from higher education to vocational training) and recourse to such an option
varies from one country to another. In France, recruitment after a successful apprenticeshipperiod is a common practice in the nuclear industry (see Box 5.4).

Industry development plan and international collaboration
The opportunities are significant to build a competent nuclear workforce at the industry andacademic levels. However, factors such as policy risks and public perception can make this task
more difficult and can only be properly addressed by governments. This situation has pushed
several countries to create nationwide nuclear industry policies in an attempt to guide industry
and academic efforts while creating a stable policy framework to face potential the LTO
challenges ahead. In June 2018, for example, the government of the United Kingdom released its“Nuclear Sector Deal” with a strong, joint commitment to developing a highly skilled workforce(BEIS, 2018). Similar joint endeavours were published in France in January 2019 (see Box 5.4).
These types of agreements also provide positive policy signals to address public perception issues
among young generations and help industry to sustain its capabilities.
At the international level, several organisations are contributing to nuclear human workforce
development in various ways. The IAEA has represented the reference in terms of knowledge
management methodologies and guidance for the nuclear sector since the early 2000s. The
organisation also provides knowledge management services to members that need specificassistance (IAEA, 2020). In Europe, organisations such as the European Nuclear Education Network(ENEN) and the European Nuclear Energy Forum (ENEF) support nuclear knowledge preservation,higher education and training. The European Commission (EC) Joint Research Centre (JRC) hosts
and manages the European Human Resources Observatory for Nuclear (EHRO-N). This initiative
was set up by ENEF with the aim of monitoring supply and demand for nuclear human resourcesin the European Union and making recommendations on specific policies to address potential
gaps (EHRO-N, 2020). The NEA has also assisted member countries in addressing issues associatedwith nuclear workforce capabilities (NEA, 2000; 2012a). The NEA Nuclear Education, Skills and116

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTS

Technology (NEST) Framework, for example, recently entered into force in February 2019. The
main objective of this initiative is to foster nuclear skills capacity building, knowledge transfer andtechnical innovation in the international context (NEA, 2020).

Key findings•

Globally, nuclear power plants have steady improvements in safety and reliability levels despite an ageing
nuclear fleet. The explanation for such improvements can be found in replacements of structures, systems
and components (SSCs) during plan refurbishments, increasing technical progress and operating
experience, combined with governing frameworks that foster continuous improvements and theadoption of best international practices.

•

The nuclear supply chain remains robust and mature after more than one hundred LTO projects around theworld. From a technical and managerial perspective, LTO projects are simpler than new build projects,
contributing to their overall low risk profile. SSC obsolescence and supply chain issues, however, are a risingconcern as a result of increasing policy risks, degraded market perspectives and high qualification needs. The
severity of these issues varies from country to country depending on the size and standardisation of thenuclear programme. Several strategies can be adopted to reduce supply chain risks associated with theprocurement and qualification of critical structures, systems and components, including the introduction ofcommercial grade dedication and higher collaboration and harmonisation levels across countries. Somecountries are undertaking national initiatives in this direction, in co-operation with regulators.

•

Recent experience shows that the nuclear industry has sufficiently planned and managed the retirementof a significant share of its workforce. Attracting and retaining talent nonetheless remains a major
concern. The industry and academia can join forces to increase the attractiveness of the sector, butgovernments are key in addressing public perception issues that could hamper nuclear workforce
development. National nuclear industry policies provide a functional framework to properly guide joint
undertakings among government, industry, research institutes and academia.

References
ASN (2021), “Décision n° 2021-DC-0706 de l'ASN du 23 février 2021”, Autorité de Sûreté Nucléaire,
Paris, www.asn.fr/Reglementer/Bulletin-officiel-de-l-ASN/Installations-nucleaires/Decisionsindividuelles/Decision-n-2021-DC-0706-de-l-ASN-du-23-fevrier-2021.
Bruce Power (2016), Working Together to Deliver the Future of Nuclear in Ontario: An Interim Report on
Collaboration to Extend Ontario’s Nuclear Fleet, Ontario Power Generation/Bruce Power,
www.opg.com/wp-content/uploads/2019/04/WorkingTogetherToDeliverTheFutureOfNuclear
InOntario.pdf.
BEIS (2018), Policy Paper Nuclear Sector Deal, Policy Paper, UK Department for Business, Energy andIndustrial Strategy, www.gov.uk/government/publications/nuclear-sector-deal/nuclearsector-deal.
Conseil National de l’industrie (2019), “Signature du contrat stratégique de la filière nucléaire”,(press document), https://minefi.hosting.augure.com/Augure_Minefi/r/ContenuEnLigne/Down
load?id=80613611-8D41-4EBC-95CD-6AC5957798F1&filename=992%20%20%20Contrat%20de%20la%20fili%C3%A8re%20Nucl%C3%A9aire.pdf.
Deloitte, (2018), 2018 Deloitte Millennial Survey, Deloitte, www2.deloitte.com/content/dam/Deloitte/global/Documents/About-Deloitte/gx-2018-millennial-survey-report.pdf.
Dudézert, A. et al. (2012), “Le KM au cœur de la stratégie d'entreprise”, Documentaliste-Sciences
de l'Information, Vo. 49, No. 2, pp. 26-43, www.cairn.info/revue-documentaliste-sciencesde-l-information-2012-2-page-26.htm.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

117

OPERATIONAL AND HUMAN ASPECTSEDF (2020), “EDF adjusts the costs of its Grand Carénage Programme”, www.edf.fr/sites/default/
files/contrib/groupe-edf/espaces-dedies/espace-medias/cp/2020/2020-10-29-prcertified_edf-adjusts-the-cost-of-its-grand-carenage-programme.pdf.
EHRO-N (2020), European Human Resource Observatory for the Nuclear Energy Sector, website,
https://ec.europa.eu/jrc/en/ehro-n (accessed on 29 June 2021).
EMINE (2020), European Master’s in Nuclear Energy, website, www.innoenergy.com/forstudents-learners/master-school/master-s-in-nuclear-energy/ (accessed on June 29 2021).
EPRI (1998), Guideline for Reverse Engineering, Rep. TR-107372, EPRI, Palo Alto, http://jtaken.csoft.net/school/excelsior/Corco/School/EPRI%20TR-107372%20-%20Reverse%20Eng.PDF.
Fillon, B. (2019), Attracting, Training and Retaining the Next Generation of Nuclear
Professionals”, NEA-IAEA-WANO Workshop on Human Capital, NEA, Paris.
Fortum, TVO, Fennovoima (2019), KELPO - Development of the licensing and qualification processes forthe systems and equipment of nuclear facilities in Finland: Final Report, https://energia.fi/files/
3665/KELPO_-_Development_of_the_licensing_and_qualification_processes_for_the_systems_and_equipment_of_nuclear_facilities_in_Finland_-Final_report.pdf.
IAEA (2021), Power Reactor Information System (PRIS) (database), https://pris.iaea.org/PRIS/home.aspx(accessed on 29 June 2021).
IAEA (2020), Nuclear Knowledge Management, website, IAEA, Vienna, www.iaea.org/topics/
nuclear-knowledge-management (accessed on 29 June 2021).
IAEA (2018), Ageing Management and Development of a Programme for Long Term Operation of Nuclear
Power Plants, Specific Safety Guide No. SSG-48, IAEA, Vienna, www-pub.iaea.org/
MTCD/Publications/PDF/P1814_web.pdf.
IAEA (2016), Procurement Engineering and Supply Chain Guidelines in Support of Operation and
Maintenance of Nuclear Facilities, IAEA, Vienna, www-pub.iaea.org/MTCD/Publications/
PDF/Pub1725_web.pdf.
IAEA (2014), Safety Classification of Structures, Systems and Components in Nuclear Power Plants,
Specific Safety Guide, No. SSG-30, IAEA, Vienna, www-pub.iaea.org/MTCD/Publications/
PDF/Pub1639_web.pdf.
IEA (2021), Energy Technology RD&D Budget Database (database), www.iea.org/data-and-statistics/
data-product/energy-technology-rd-and-d-budget-database-2 (accessed on 29 June 2021).
IEA (2020a), Energy Technology Perspective 2020, IEA, Paris, www.iea.org/reports/energytechnology-perspectives-2020.
IEA (2020b), Germany 2020: Energy Policy Review, IEA, Paris, www.iea.org/reports/germany-2020.
Kang, K-S Krivanek, R. (2017), IAEA Contributions to Plant Life Management and Long Term Operation,
4th International Conference on Nuclear Power Plant Life Management, IAEA, Lyon.
Lévêque, F. (2014), The Economics and Uncertainties of Nuclear Power, Cambridge University Press,
Cambridge.
LWRS (2020), Light Water Reactor Sustainability, website, https://lwrs.inl.gov/SitePages/Home.aspx(accessed on 29 June 2020).
MAI (2020), Materials Ageing Institute, website, https://themai.org/#:~:text=Currently%2C%20
eleven%20members%20include%20the,%2C%20Japan)%2C%20Central%20Research%20Institute (accessed on 29 June 2020).
Martin, O. and Abbt, M. (2020), Current Challenges of the European Nuclear Supply Chain, Joint
Research Centre, Luxembourg, https://ec.europa.eu/jrc/en/publication/eur-scientific-andtechnical-research-reports/current-challenges-european-nuclear-supply-chain.
Naden, C. (2018), “New standard to improve safety in the nuclear sector”, ISO, www.iso.org/
news/ref2296.html.

118

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

OPERATIONAL AND HUMAN ASPECTSNEA (2020), The Nuclear Education, Skills and Technology (NEST) Framework, website,www.oecd-nea.org/jcms/pl_21786/nuclear-education-skills-and-technology-nestframework (accessed on 29 June 2021).
NEA (2019), “Outcomes of the NEA/IAEA/WANO Workshop on Human Capital – Towards a Global
Community Approach”, NEA/IAEA/WANO Workshop on Human Capital, OECD/NEA,
www.oecd-nea.org/download/hans/workshops/2019/human-capital/outcomes-2019.pdf.
NEA (2015), Nuclear New Build: Insights into Financing and Project Management, OECD Publishing,Paris,
www.oecd-nea.org/jcms/pl_14904/nuclear-new-build-insights-into-financing-andproject-management.
NEA (2012a), Nuclear Education and Training: From Concern to Capability, OECD Publishing, Paris,
www.oecd-nea.org/jcms/pl_14668.
NEA (2012b), The Economics of Long-Term Operation of Nuclear Power Plants, OECD Publishing, Paris,
www.oecd-nea.org/jcms/pl_14752.
NEA (2000), Nuclear Education and Training: Cause for Concern?, OECD Publishing, Paris, www.oecdnea.org/jcms/pl_13372.
OECD (2018), Education at a Glance 2018, OECD Publishing, Paris, www.oecd-ilibrary.org/
education/education-at-a-glance-2018_eag-2018-en.
Owen, K., (2018), “Hinkley Point C – Industrial Collaboration”, Nuclear Supply Chain Management
Workshop, OECD/NEA.
Pate. Z., Ellis, J. (2011), “The Evolution of Nuclear Safety”, WNA Personal Perspectives, www.worldnuclear.org/uploadedFiles/org/Archive/WNA_Personal_Perspectives/evolution_of_nuclear_sa
fety(1).pdf.
Reuters (2015), “Knowledge transfer strategies require long-term, digital approach”,
www.reutersevents.com/nuclear/operations-maintenance/knowledge-transfer-strategiesrequire-long-term-digital-approach.
RGN (2017), “L’alternance, une voie d’exellence pour rejoindre la filière nucléaire”, Préparer lanouvelle épopée nucléaire, Revue Générale Nucléaire, Sfen, Paris, https://rgn.publications.
sfen.org/articles/rgn/abs/2017/04/rgn20174p40/rgn20174p40.html.
WANO (2020a), Global Membership Map 2020, World Association of Nuclear Operators,
www.wano.info/Web/files/f2/f20d3d7c-7580-4586-809f-8a14a83486b3.pdf.
WANO (2020b), Performance indicators 2020, World Association of Nuclear Operators,
www.wano.info/getmedia/c77f6990-37c8-4550-bb1f-2cd4b69829a4/2004-WANOPerformance-Indicator-Electronic-Document-6pp.pdf.aspx.
WNA (2020), The World Nuclear Supply Chain: Outlook 2040, WNA, London, www.worldnuclear.org/press/press-statements/launch-of-the-world-nuclear-supply-chain-outlook2.aspx - :~:text=Under the reference scenario, revenues,OECD area, including China).
WNN (2017), “Siemens prints part for Krško plant, World Nuclear News”, www.world-nuclearnews.org/NN-Siemens-prints-part-for-Krsko-plant-0903174.html.
YNPF (2018), Generational Analysis for the Recruitment and Retention of Talent within the Nuclear
Industry, Young Nuclear Professionals’ Forum, www.nuclearinst.com/write/MediaUploads/SDFdocuments/YNSPF/NGSReport_Final_v1.0.pdf.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

119

ECONOMIC ASPECTS

6. Economic aspects

The economics of nuclear power have been the subject of intense study and scrutiny in past
years given the importance of understanding the cost and risk drivers of this technology so as
to adhere to sustainable development capacity scenarios. Economic trends observed in recent
new nuclear build projects within OECD countries have also nourished general policy and public
perceptions that all nuclear investments should be expensive and risky, even those that concern
existing reactors currently in operation. However, actual evidence from most nuclear power
plants operating around the world today does not confirm these perceptions.
While new build and long-term operation (LTO) are related to the same technology, theassociated investments are significantly different from an economic perspective. The LTO of a
nuclear power plant requires brownfield investments on assets that are already built and, to alarge extent, amortised. The extent and complexity of the technical work is also less significant
compared to building a new facility. The results of the present report confirm that LTO remains
the most competitive, low-carbon technology option in many regions around the world, andthat refurbishment costs are predictable and well-contained. A closer look at LTO economics
reveals that cost and risk breakdown patterns can help to explain why policymakers should
regard LTO as an independent and separate solution in the low-carbon technology portfolio. 1
The 2020 edition of Projected Costs of Generating Electricity (IEA/NEA, 2020) thus introduces for the
first time LTO investments. 2
Like any other low-carbon technology, existing nuclear reactors nevertheless have sizeable
fixed costs that can make them more exposed to market risks. Challenges in existing market
designs, amplified by regional conditions (e.g. abundant cheap fossil fuels), is pushing some
operators to cease operation earlier than expected, particularly in the United States. Around
25% of early closures between 2011-2025 resulted solely for market reasons, and another quarterof these closures have been influenced by electricity price prospects that may not guarantee thereturn of the necessary LTO investments (see Figure 1.2). The present economic analysis
therefore encompasses both cost and market dimensions in order to provide a full picture of
the economic conditions in relation to the existing nuclear fleet worldwide, as well as of theareas where effective policy action could enable LTO.

6.1. The generation costs of LTO
6.1.1.Breakdown and cost metrics
The generation costs of nuclear power, similar to any other electricity generation technology,
fall essentially into four main categories: i) capital costs; ii) operation and maintenance (O&M)
costs; iii) fuel costs; 3 and iv) decommissioning costs. Capital costs can be split, in turn, intoovernight construction costs (OCCs) and financing costs.

1.

Other low-carbon technologies with long lifetimes, in particular hydro-electric plants, could be similarly
attractive for such LTO investments (IEA/NEA, 2020).

2.

A shorter version of the LTO economic analysis developed in this chapter is presented in Chapter 8 of
IEA/NEA (2020).

3.

O&M and fuel costs can be grouped together, and considered as operational expenditures (OPEX).

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

121

ECONOMIC ASPECTSThe OCC represent all of the expenses necessary to design, build and commission the plant.
For the particular case of LTO, the OCC cover the investments necessary to sustain operations
for a given period. The OCC metric assumes that all of the investment is disbursed at once
(i.e. overnight), and consequently, it does not capture any time-related effects in the form offinancial interests or discounted payments. These costs are typically reported in US dollars (USD)
per installed kWe. In essence, the OCC reflects the intrinsic cost of a given technology andenables cross-technology comparison, independently of financial conditions.
The different cashflows associated with each of the aforementioned cost categories(i.e. investment, O&M, fuel and decommissioning) can then be evaluated over the expected
lifetime of the asset, discounted and levelised through electricity generation over the same period
according to an expected capacity factor to compute the LCOE. 4 The LCOE can be interpreted as
the minimum average price of electricity needed over a lifetime for the investment to reach the
break-even point, and it is typically expressed in USD per MWh (or cents per kWh). System costs(i.e. balancing, grid and profile costs 5) and other externalities beyond decommissioning and waste
management (i.e. air pollution cost) (see Chapter 2) are not captured via the LCOE calculation.
Additional explanations of the different cost categories involved in the calculation of the nuclear
power LCOE can be found in IEA/NEA (2020) and NEA (2020).
The LCOE methodology was originally developed to assess baseload technologies operating
under rate-regulated and stable electricity prices. After the deregulation wave of the power
sector initiated in the 1990s, this can no longer be considered the case. At the same time, thepenetration of higher shares of variable renewable energy (VRE) generation is progressively
reducing the window of the LCOE to adequately reflect the economic performance of atechnology in the electricity market. Aspects such as systems costs and dispatchability
attributes (e.g. capacity credit, flexibility) need to be properly accounted for in the metrics toensure a proper comparison between VRE resources and conventional generators. For thisreason, new complementary metrics such as the value-adjusted LCOE (VALCOE) 6 are being used
to provide a fuller economic picture (IEA/NEA, 2020).
The Nuclear Energy Agency’s Ad Hoc Expert Group on Maintaining Low-Carbon Generation
Capacity through Long-Term Operation (LTO) of Nuclear Power Plants: Economic, Technical andPolicy Aspects (EGLTO) acknowledged the limitations associated with the use of the LCOE in thecurrent and future energy context, but concluded that this cost figure should be at the core of
the economic analysis of LTO for two main reasons:•

The simplicity and transparency of the LCOE makes it a well-understood metric that isstill widely used today in energy modelling and policy making.

•It is important to be consistent with the approach used in IEA/NEA (2020), enabling rapid
cost comparisons among technologies, countries, and past and recent studies.

Other metrics that may be relevant from a policy and utility perspective include CO2
emissions abatement costs, net present value (NPV), payback time and internal rate of return.
While in practice these may be important in the overall LTO decision-making process, most ofthese metrics are outside of the scope of the present study.

6.1.2.Economic and methodological considerations
LTO costs have the particularity of applying to existing assets (i.e. brownfield investments incontrast to new construction or greenfield investments), which means that they can beconditioned by the operational and investment history of the plant. In addition, someassumptions may be required to deal with past investments that have not been fully
depreciated. After reviewing the existing literature and several industrial cases, the EGLTO

4.

The exact formula can be found in IEA/NEA (2020), page 35.

5.

System expenses resulting from an increase in the generation costs for the rest of the electricity system,in response to the variability of VRE output, and the sub-optimal use of residual dispatchable capacity.

6.

Introduced in the 2018 edition of the International Energy Agency’s (IEA) World Energy Outlook(IEA, 2018), VALCOE incorporates all traditional plant-unit cost elements, but also adds three categoriesof the value in power systems: energy, flexibility and capacity. Combining these costs and value
measures provides a stronger basis for comparisons between VRE and conventional generators.

122

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

drew upon several economic and methodological considerations for the evaluation of costs
associated with any LTO project. The purpose is to provide a consistent and conservative
estimate of the LTO costs while ensuring a certain degree of freedom to adapt to the specificconditions of each project.

OCC
As illustrated in Figure 6.1, once a nuclear power plant is built, generation costs are low andstable. However, as the end of the initial design lifetime approaches (i.e. typically around 30-40
years for light water reactor technologies), investment patterns tend to increase rapidly as
operators start to undertake the necessary replacements and modifications for LTO of the plant
for a defined period. 7 These expenses correspond to the LTO OCC costs (or LTO investments)
and the evaluation of such costs is not always straightforward.

Figure 6.1: Generic distribution of costs (left) and LTO investments (right)
over the operating time frame of a nuclear power plant

-7

-2

3

12

Source: NEA, 2015.

18

25 30
Year

36

Regular maintenance

LTO

Sunk

42

48

54

30

35

40

45
Year

50

LTO

55

60

Source: Courtesy of CEZ.

One of the first difficulties arises from the definition of the exact envelope of the LTO
investment. LTO investments are those specifically incurred to extend operation of the plant
and are therefore different from regular and maintenance investments that can be assimilated
to fixed O&M (see Figure 6.1, right). Three main categories can be identified:7.

•

LTO programme: These expenses cover all the necessary studies and inspections required
to define the scope of the LTO programme (e.g. individual plant assessments, time limited
ageing analysis, as shown in Chapter 3), and the management of the regulatory andlicensing interfaces. They can largely be considered as indirect costs. They can also coveradditional ageing management programme activities (i.e. monitoring, testing, in-service
inspection, maintenance) that could eventually lead to a re-evaluation of the O&M costs
during the LTO period.

•

Replacement of heavy components and other works: This category usually represents
the bulk of LTO investments and includes the replacement of mechanical and electricalequipment, fluid systems, instrumentation and controls (I&C) and civil works. Additional

These investment trends are quite specific to nuclear power as they are, to some extent, aligned withthe regulatory calendar of the LTO review process of each country. This is not the case, for instance, forother technologies, for which LTO expenses do not spike in accordance with regulatory decisions andcan simply be assimilated as fixed O&M costs. The specific trends of nuclear investment on existing
assets support the treatment of LTO as a different “technology” from an economic perspective.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

123

ECONOMIC ASPECTS

details of the specific nuclear power plant components typically being replaced during
LTO refurbishment is detailed in Chapter 3. Both the direct costs of the components andthe necessary equipment and labour for their installation should be accounted for in thiscategory, as well as project management and other engineering services.
•

Post-Fukushima 8 : These are the investments necessary to meet the post-Fukushimasafety standards. They cover extensive plant upgrades and the installation of new,redundant systems. Some examples are presented in Chapter 5 of the present report.

While this categorisation can be considered consistent from a technical and economic
perspective, in practice it may face some shortcomings. First, operators usually perform
additional plant enhancements and safety upgrades alongside LTO refurbishments. Accounting
rules used by utilities may not differentiate LTO expenses from other expenses, making LTO
cost data difficult to retrieve. Second, these categories are not identical from one company toanother, which inhibits the application of standard cost categories for more transparent datacollection and comparison across projects.
The analyses carried by the EGLTO experts also concluded that, rather than determining asingle cost figure for LTO, it would be more convenient to define a cost range, covering with ahigh degree of confidence the typical envelope of LTO expenses. While most utilities willroughly devote the same number of resources to define the extent of the LTO programme, thescope of the components to be replaced, as well as of post-Fukushima safety upgrades, can varyconsiderably from one project to another. The final LTO OCC will essentially be conditioned byvarious factors, as confirmed in the findings of The Economics of Long-Term Operation of Nuclear
Power Plants (NEA, 2012):
•
•
•
•
•

specific design characteristics;
operational experience and history;
previous investments and retrofits already implemented at the plant;
the regulatory framework;
potential safety upgrades or plant enhancements performed by operators on a voluntarybasis.

Another challenge lies in the time distribution of LTO investments. In fact, the applicationof the LCOE methodology requires the treatment of all LTO expenses as an overnight cost thatis discounted over time. For brownfield investments, previous investment should be considered
as sunk (see Figure 6.1, left). 9 However, this may not be a realistic representation of the actual
expenditure patterns for LTO as most of the capital costs are continuous and incremental rather
than upfront at the age of 40 years (see Figure 6.1, right). As such, it is possible to identify somenuclear power plants for which the actual LTO investments at the end of the original design
lifetime are very low since operators had been investing on a continuous basis in ordermaximise the lifetime of the asset. In this situation, LTO OCC costs can be estimated by defining
a baseline of regular investments to sustain plant operations 10 and then by identifying any
excess investment that could be attributable to LTO over a given period. This approach isillustrated in Box 6.1 below.
Among the different LTO projects examined in this report, some of them reported upfront
OCC and others reported yearly investments over a defined period; the reality for most plants

8.

EGLTO experts have argued that post-Fukushima investment cannot be considered as an LTO cost perse since it is not related to the ageing of the plant. In fact, if the Fukushima accident had not takenplace, post-Fukushima measures may not have been necessary. However, there was an overall
consensus among EGLTO experts that no LTO authorisation or approval would be granted by regulators
today without complying with post-Fukushima safety standards. It is, however, to be noted that thescope of the modifications related to a “post-Fukushima” upgrade can highly differ from plant to plant.

9.

From an economic point of view, it is possible to include some sort of depreciation term in the LCOE so
as to account for past investments. Such an approach is not considered in the present economic
analysis to be consistent with the methodology used in IEA/NEA (2020).
10. This baseline corresponds, for instance, to periodic maintenance investments for more short-lived
systems, structures and components (SSCs), and these can be assimilated to fixed O&M costs.

124

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

being somewhere in between. The evaluation of the LTO OCC must therefore be undertaken ona case-by-case basis, considering whenever possible annual investment patterns and making
the necessary adjustments to isolate LTO investments and treat them as actual OCC. This
process should be conservative, for instance, by not discriminating LTO expenses from otherplant enhancements and/or safety upgrades, and therefore leading to overestimated (butconservative) LTO figures (see Box 6.1 below).

Box 6.1: Estimating LTO overnight costs: The Swedish caseIn 2016, the consultancy firm, SWECO, prepared a report as an input to assist the Swedish government in its
economic evaluation of the different technology options (SWECO, 2016). 11 The SWECO report provides dataon annual yearly investments for the entire Swedish nuclear fleet 12 from 2000 to 2045, reconstructed frompublicly available sources such as yearly income statements from the utilities (see Figure 6.2 below).
The baseline shown in Figure 6.2 indicates the annual volume-aggregated investments for all Swedish nuclear
power plants as being in the order of USD 350 million per year. 13 This is the investment level in the plateau
from 2020 and 2030. The investment volume beyond 2030 gradually falls below this base level, which can be
expected when approaching the last years of operation. For the period between 2005 and 2020, higher
volumes of investment above the base level are observed. These greater expenses can be attributed to themajor safety improvements required by the regulator that are carried out in combination with ageing
management measures, and in some cases, power uprates. A major, additional safety upgrade finalised in 2020
was the design and construction of complementary independent core cooling systems as part of postFukushima measures (NucNet, 2020), which explains why the total investment volume exceeds the regularbaseline between 2016 and 2020. Investment levels in the period 2000-2004 are, on the other hand,
exceptionally low, which may be attributed to minimised investments on the part of operators during thisperiod as a result of high political uncertainty regarding the future of nuclear power, as well as increasing
market pressures following the deregulation of the electricity market in Sweden in the late 1990s.
Figure 6.2: Yearly investments in the Swedish nuclear fleet, 2000-2045
1 000Million USD

800
600
400
200
2000
2002
2004
2006
2008
2010
2012
2014
2016
2018
2020
2022
2024
2026
2028
2030
2032
2034
2036
2038
2040
2042
2044

0

Regular

LTO

Note: These investment projections include Oskarshamn units 1 and 2, and Ringhals 1 and 2,
which in the end did not pursue LTO.
Source: OECD/NEA, adapted from SWECO (2016).

11 The original title of the report in Swedish is “Ekonomiska förutsättningar för skilda kraftslag”.
12. Note that these cost figures include investments undertaken in the Oskarshamn units 1 and 2, andRinghals 1 and 2, which in the end did not pursue LTO. These investments were made prior to theintention of considering LTO. In fact, these reactors operated slightly beyond 40 years.
13. Considering 10 GW of installed capacity in Sweden, this corresponds to USD 30-40 million per kWe,which is consistent with the typical investment levels (or volume of work) that can be engaged during
normal outages in a nuclear power plant.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

125

ECONOMIC ASPECTS

The SWECO report indicates that the aggregated annual investment between 2005 and 2014 is on averagearound USD 680 million, which corresponds to a total excess investment over ten years of USD 3.3 billion thatcan conservatively be attributed to LTO, as shown in the above figure. Considering a total installed capacity of
10 GW, and assuming all expenses as overnight, this yields USD 330 per kWe. A total of USD 60-120 million perreactor should furthermore be taken into account during 2016 and 2020 as part of post-Fukushima measures,
leading to an additional USD 105 per kWe. 14
In conclusion, the LTO OCC in Sweden can be estimated to be around USD 440 per kWe. Actual LTO OCC are,however, less significant since most of these expenses cover safety upgrades engaged since 2005, as well as
power uprates for some reactors that are not necessarily related to LTO. The most direct LTO-specificinvestments involve LTO-verification and justification (including time limited ageing analyses [TLAAs]) of thereactor pressure vessel, environmental qualification, ageing-related turbine/alternator replacements, as wellas the management of obsolescence in relation to spare parts for I&C components.

O&M costs
O&M and fuel costs represent operating expenditures (OPEX), which, for nuclear power, remain
low and stable (see Figure 6.1), which explains why this technology is well-fitted for baseload
generation. It is, however, necessary to provide some insight into factors that could drive up (ordown) OPEX over time (or before and after LTO refurbishment), as well as some justifications inrelation to this type of expenditure, and to which extent, it can be assumed to be similar torecent Gen III/III+ reactors.
In terms of O&M trends, in D’haeseleer’s Synthesis on the Economics of Nuclear Energy (2013),
the author illustrates how O&M costs vary significantly across countries, which can be
explained by the different accounting conventions. O&M costs are often divided into a fixed
and a variable part, but most of the time it is not clear what is included in each part. In practice,
the fixed O&M part may correspond to the regular baselines illustrated in Figure 6.1 and in
Figure 6.2, capturing the refurbishments associated with short-lived components. Overall, thefinal baseline can be set at different levels according to different rules, but from an LCOE
perspective, the result will essentially be the same.
The fixed part of O&M can also be lowered thanks to economies of scale and on-site multiunit and nuclear fleet standardisation effects, which can spread fixed charges across various
reactors. At the same time, it can be argued that maintenance costs may increase over time due
to ageing. However, as illustrated in Chapter 4, there are other drivers that should be considered,such as operational experience and technical progress that can contribute to containing (or evenreducing) O&M costs. In fact, lower O&M costs can be observed following major plantmodernisation efforts that have been carried out during LTO refurbishments.
In light of these trends, EGLTO concluded that the evolution of O&M costs during extended
operations may not always be evident. Considering the O&M costs of Gen III/III+ new build forthe calculation of LTO figures could be a good approach, therefore, and would be consistent withthe conclusions of D’haeseleer (2013).

Fuel costs
Fuel costs can be separated into front-end (i.e. mining, enrichment and manufacturing of thefuel assemblies) and back-end (i.e. reprocessing, conditioning and final waste disposal) costs,
covering the whole fuel cycle. These costs can vary depending on the type of fuel cycle chosen(open or closed cycle) and on the course of fissile material prices. For existing reactors, it ispossible to improve front-end fuel economics with optimised fuel loading and the adoption offuels that allow for higher burn-up. The consideration of front-end cost data for new build
nevertheless remains a robust approximation.

14. Only the remaining six reactors in operation, accounting for a total capacity of 6.9 GW, are consideredin this case.

126

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

At the same time, it is necessary to account for the costs of managing the radioactive waste
generated during the LTO period. EGLTO acknowledged that these expenses could varysignificantly depending on country-specific conditions. In some cases, for instance, at the
moment that LTO is being considered, most of the infrastructure to store any additional waste
generated is already available, which would mean no major re-evaluation of back-end costs.
Conversely, other countries may require new interim storage facilities and/or may introduce
new regulations that could potentially lead to higher back-end costs during the LTO period.
These aspects can be conservatively addressed by considering cost data for new build, anapproach consistent with D’haeseleer (2013).
Lastly, when assessing fuel back-end costs, it is important to distinguish between theeconomic and the financial perspectives. In fact, postponing the closure of a nuclear power
plant can bring some financial benefits 15 (e.g. waste management trust funds will be able togenerate returns for a longer time frame than initially planned, reducing the provisions thatneed to be allocated to the funds) and therefore the LCOE (see Box 6.2). Conservatively, these
aspects are not included in the calculations presented in the present report.

Refurbishment period
One of the key characteristics of LTO refurbishments is that some of the work can be executed
while the plant is in operation. The LTO work, for example, in the LWR unit Triscastin-1 in
France took a total of 23 months: 18 months with the reactor online and a long outage of
5 months with the reactor shut down (Payen, Willot, 2019). EGLTO made a conservative estimateof two years (with the reactor completely shut down) as the refurbishment period for the
calculations of LWR LTO LCOE. It is important, nevertheless, to highlight that the refurbishment
period can vary depending on the envelope of the LTO work, and the technology. For instance,
given the larger volume of activity associated with “retubing” 16 of a pressurised heavy water
reactor (PHWR), four years would be the estimate for these types of reactors (see Box 6.3).

LTO period
For LWRs, the LTO period varies between 10 and 20 years according to the existing regulations
in most countries. 17 For PHWRs more specifically, the LTO period considered is 30 years.
Additional technical and regulatory insights on these numbers are provided in Chapters 3 and5, respectively.

Decommissioning costs
With regard to decommissioning costs, evidence from the Loviisa project in Finland indicatesthat an increase of the operational lifetime of a nuclear power plant has no significant impact
on decommissioning costs (NEA, 2016). For this reason, decommissioning costs can beconsidered as almost independent and invariant in relation to the operating life of a nuclear
power plant. The potential cost increments associated with the dismantling and handling ofcontaminated components during LTO refurbishment are very low and generally directly
included in LTO investments. As such, initial decommissioning costs can be considered ashaving been fully provisioned during the initial lifetime period (IAEA, 2018), with no additional
cost during the LTO period.
Similar to the back-end fuel costs, delaying decommissioning cost outlays would translate
into a negative cost (benefit), and it will therefore not be considered in the present calculations(see Box 6.2 below).

15. Assuming that inflation and potential cost escalations do not outweigh these benefits.
16. For the CANDU 6 PHWR design “retubing” means the replacement of the 380 calandria tubes, 380 pressure
tubes, 760 end fittings, 760 feeders, and various supporting and connecting components (see Chapter 3).
17. In some countries, 30 years are granted for VVER designs.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

127

ECONOMIC ASPECTS

Box 6.2: Quantifying the financial benefits of delaying the closure of a nuclear power plant
Before evaluating the value of delaying the closure of a nuclear facility, it is important to distinguish economic
treatment from the actual financial implications of decommissioning and waste management (D&WM) costs
for nuclear power plant operators. In general, and according to the “polluter pays” principle, D&WM costs are
fully internalised. The LCOE formula uses two cost components to internalise D&WM costs: i) decommissioning
costs (i.e. for the actual dismantling, handling and storage of irradiated components); and ii) back-end fuelcosts (i.e. fuel removal, interim storage and final waste disposal) integrated into the overall fuel cycle costs. In
the present study, for instance, fuel cycle costs are estimated at USD 9.33/MWh, with back-end fuel costs
representing USD 2.33/MWh (IEA/NEA, 2020).
In practice, however, the internalisation of D&WM costs is carried out in a different manner. Operators makeannual contributions to dedicated funds through an allocation of provisions or through specific fees leviedfrom the operators’ revenues during the operation of the plant. The amount of these annual contributions is
calculated based on estimates of D&WM costs that are periodically re-evaluated. The process, as well as theorganisations responsible for managing these funds and the repartition of liabilities, are aspects that vary fromone country to another, and thus are out the scope of the present study.
The fact that operators make annual contributions to a dedicated fund as long as the plant is running brings
direct financial benefits 18 if LTO is pursued. These benefits can be quantified in two ways. First, the returns of
the dedicated fund continue to grow every year. Assuming a discount rate of 2%, the total available fund canincrease by 15% for a LTO period of ten years. The longer the LTO period, the greater the benefits (see Figure
6.3 below).
Figure 6.3: Evolution of the decommissioning fund as a functionof the LTO period and the discount rate
1,50
1,00
0,50
0,00
Initial fund1%
10 years LTO

2%

3%

20 years LTO

Note: The decommissioning costs allocated to the fund are assumed to be disbursed five years after
the last operational year, for a duration of decommissioning work lasting ten years (IEA/NEA, 2020)

Second, the plants will continue to provide annual contributions to the fund during the LTO period. Assumingthat the necessary funding remains constant, LTO can significantly reduce the number of annual contributions,thus improving the profitability of operators. In Spain, adding ten years of operations can reduce fees byaround 50% (MITECO, 2018). Similarly, in an audit on the evaluation of the decommissioning costs performedin France, government experts estimated that an extension of the operating time frame from 40 to 50 years
could lead to a reduction of the required provisions for decommissioning of the existing fleet by approximately
EUR 3.2 billion (DGEC, 2015).
Overall, the financial benefits of delaying the closure of a nuclear power plant increase almost linearly with its
operating time frame. Its value could be captured in the LCOE formula as a negative cost (benefit), leading tolower LCOE values. In the present study, however, this effect has not been taken into account in order toincrease the degree of conservatism of the LTO cost figures and to be consistent with the methodology
employed in IEA/NEA (2020). In addition, these results show that LTO will make a positive contribution toensuring the adequacy of funding for D&WM activities (see Box 2.4).

18. This example abstracts from inflation and escalation effects, as well as new regulations that could
potentially offset these benefits.

128

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

6.1.3.Evaluation of LTO generation costs
LTO OCC and LCOE analysis
Given the considerations described in the previous section, as well as various case studies, EGLTO
concluded that an average overnight LTO investment for LWRs 19 in OECD countries would range
from USD 450-950 per kWe. This variability can largely be explained by the differences in thescope of LTO investments for reasons previously indicated (e.g. operating experience, previous
investment in the plant, regulatory framework, See Section 6.1.2). Moreover, these numbers havebeen estimated in a conservative manner as they treat all plant enhancements as LTO expenses. 20

Table 6.1: LTO LCOE values for LWRs as a function of the LTO period,
discount rate, overnight costs and the capacity factor
Overnight LTO
investment costs(USD/kWe)

3%

450
700
950

29.4
33.4
37.4

450
700
950
Min
Max

31.9
36.5
41.0

LWR LTO LCOE (USD/MWh)
LTO period = 10 years
LTO period = 20 years
Discount rate
Discount rate
7%
10%
3%
7%
Capacity factor = 85%
31.2
32.6
26.4
28.6
36.1
38.3
28.7
31.4
41.1
44.1
31.0
34.7
Capacity factor = 75%
33.9
35.5
28.4
30.5
39.5
42.0
31.0
34.2
45.1
48.5
33.6
37.9
29.4
26.4
48.5
41.6

10%
29.7
33.8
38.0
32.2
36.9
41.6

Note: These values have been computed assuming a refurbishment period of two years, fixed O&M costs of USD 85/kWe, variable O&M
costs of USD 1.5/kWe, front-end fuel costs of USD 7/MWh and back-end fuel costs of USD 2.33/MWh, consistent with the values for newbuild projects considered in IEA/NEA (2020). The overnight LTO investment cost includes other plant enhancements beyond LTO and 5%of contingencies. Decommissioning costs are not included as they have largely depreciated during the initial design lifetime.

A closer look into the structure of the LTO OCC confirms that most investment consists of thereplacement of heavy components and other work, including the labour necessary for theirinstallation. The indirect costs associated with project management, regulatory and licensing
interfaces and the initial engineering efforts necessary to evaluate the extent of LTO
refurbishments (i.e. LTO programme) are not negligible and typically account for 20-25% of thetotal investment. The updated review of the costs associated with Fukushima upgrades for several
projects shows that they can vary considerably, depending on the project, but they could represent
in some cases 20-25% of the total OCC. This represents an increase compared to preliminary
estimates of 10-17% in NEA (2012), which does not threaten the overall competitiveness of LTO
investments. Table 6.1 above shows the LTO LCOE for different overnight costs, real discount rates,
capacity factors and LTO periods. 21 The assumptions are summarised at the bottom of the table.
The table is intended to cover all of the expected LCOE associated with LTO of LWR in OECD
countries. 22 The case of a capacity factor of 75% captures the short-term economic penalty
associated with higher shares of variable renewables in the electricity system. Taking into account

19. LWRs represent roughly 85% of installed nuclear capacity worldwide.
20. This means that power uprates, safety upgrades and other types of plant enhancements not associatedwith licence extension for LTO of the plant are included in the overnight costs of LTO considered in thepresent study.
21. The LTO periods presented in Table 3.1 (i.e. 10 and 20 years) are the typical values considered for LWR
reactors in most countries. Other technologies, such as PHWRs and VVERs, take into account 30 additional
years of operations.
22. For instance, country values for France, Sweden, Switzerland and the United States included in IEA/NEA(2020) fall into the results presented in Table 6.1.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

129

ECONOMIC ASPECTS

all of these aspects, LTO LCOE is expected to fall into the range of USD 25-50 per MWh. A similar
analysis for PHWRs is presented in Box 6.3. Overall, these results confirm that the LTO of nuclear
power plants remains one of the most competitive options of low-carbon electricity generation,in line with recent IEA (2019) and IEA/NEA (2020) findings.

Box 6.3: LTO OCC and LCOE analysis for PHWRs
According to Ontario Power Generation (OPG, 2015), refurbishment work for four CANDU units at the Darlington
nuclear power plant are estimated to cost USD 7 billion leading to an OCC of around USD 2 000 per kWe. 23 The
scope of PHWR refurbishment is significantly larger than for LWRs because of work related to the retubing of thereactor. These activities represent more than 55% of the scope of the replacement of heavy components. The
estimated share of indirect costs is consistent with other LTO projects, representing 27% of the total overnight
investment.
Additional, relevant economic considerations differing from LWRs include:••••

LTO period: PHWR refurbishments are meant to cover 30 years of additional operations, which also
explains its larger technical scope;
refurbishment period: Recent experience has shown that the work can take around three to four years tocomplete; 24
capacity factor: Online refuelling enables higher load factors, which can on average be close to 90%;
fuel costs: the use of natural uranium provides savings in front-end fuel costs of around 40% (i.e. no needfor fuel enrichment; NEA, 2013), but it has the drawback of requiring deuterium production facilities. 25

Based on these considerations, EGLTO experts determined that a conservative estimate of the LTO OCC for
PHWRs could be in the range of USD 2 000-2 500 per kWe with an associated LCOE between 35-70 per MWh.
These LCOE values show that PHWRs are practically in the same competitiveness range as LWRs (seeFigure 6.4) and remain one of the most cost-competitive, low-carbon options in the countries in which they
are operating. Similar to LWRs, a sensitivity analysis performed by OPG (2015) underscores the importance ofthe load factor (or future production prospects and electricity prices) in the economic performance ofextended operations. However, the discount rate and potential uncertainties also have a noticeable impact on
the final LCOE, given the greater size of LTO investments in PHWRs.
Figure 6.4: LTO LCOE comparison between LWR and PHWR technologies
80

USD/MWh

60
40
20
0
LWR

PHWR

Note: These values have been computed assuming overnight costs of 2 000-2 500/kWe, a load factor ranging between 75-90%,
a refurbishment period of four years, fixed O&M costs of USD 85/kWe, variable O&M costs of USD 1.5/kWe, front-end fuel costsof USD 4.2/MWh and back-end fuel costs of USD 2.33/MWh, consistent with the values for new build projects considered in
IEA/NEA (2020). The front-end fuel costs do not take into account enrichment costs corresponding approximately to 40% of thetotal cost of front-end fuel activities (NEA, 2013). The overnight LTO investment cost includes other plant enhancements beyond
LTO and 15% of contingencies. Decommissioning costs are not included as they have largely depreciated during the initialdesign lifetime. Maximum and minimum values for LWR come from Table 6.1.

23. This value does not consider any contingency, interest or cost escalation.
24. These estimates do not take into account potential programme and learning effects at the Darlington
or Bruce sites in Canada, which could reduce the overnight construction costs and lead times for the
refurbishment of individual plants.
25. In the present analysis, the cost associated with these facilities is considered as sunk.

130

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

Insights on risks and financing
From a technical and managerial perspective, the scope and complexity of LTO projects is lesssignificant than for new build projects. Refurbishments do not need the same number of criticalcomponents and engineering studies, and have neither the same number of contracts andsuppliers to co-ordinate nor the same volume of manpower to be managed on-site. As of end
2020, more than 100 reactors worldwide were older than 40 years, meaning that the learning
curve of LTO is at quite an advanced stage and supported with a sufficient volume of projects
that are contributing to sustaining industrial capabilities and reducing the costs and delivery
times (see Figure 6.5, left). All of these aspects contribute considerably to reducing the real andperceived construction risks of LTO refurbishments. This situation, combined with the small
size of LTO investments compared to new build projects, allows nuclear operators to carry theseprojects in their balance sheets with limited financing costs (see Figure 6.5, right).
While project risks are low and market risks manageable, fixed costs still represent asignificant share of the expenses of existing nuclear reactors (70% compared to the 85% for newbuild). In countries where market and policy uncertainties are significant, the resulting risk
premium can challenge the economic viability of some plants.

LCOE (USD2018/MWh)Figure 6.5: Evolution of LTO LCOE for different LTO periods (left),
and the cost profile of LTO versus new nuclear build (right)
90

100%

80

90%

70

80%

12%
30%

17%

70%

60

13%

60%

50

50%

40

41%

40%

30

30%

20

20%

15%

10

10%

0

0%

14%

10 years

10 years

20 years

LTO 2012

LTO 2020

20 years

Note: LTO 2012 values from NEA (2012) have been computed for overnight
costs ranging from USD2010500 to USD20101 090 per kWe, discount rates of 3%
and 8% and a capacity factor of 85%. LTO 2020 values represent the resultspresented in Table 6.1.

57%

LTO
Financing

New build
OCC

O&M

Fuel

Note: Overnight costs of USD 700 and USD 4 500 per
kWe for LTO and new build, respectively. Real discountrate of 7% at a capacity factor of 85%. The operational
expenditure assumptions are detailed in Table 6.1.

Sensitivity analysis
The sensitivity analysis presented Figure 6.6 provides additional insight into the expectedeconomic performance of LTO under existing market conditions. Existing nuclear power plants
will be, by large, primarily affected by plant availability downturns or, on the revenue side, lowelectricity prices. The IAEA report, Economic Assessment of the Long Term Operation of Nuclear
Power Plants: Approaches and Experience (2018), arrives at the same conclusion, with a similar
analysis based on the net present value (NPV) metric at the plant level. 26 This pattern explains
the early closures of some reactors observed in the United States for market reasons, and to alesser extent, in Sweden. The dominance of parameters governing the revenue side over thecosts also indicates that operators have a strong incentive to perform power uprates (or any
other plant enhancement that increases the availability of the plant) during LTO projects as thiswill directly improve the attractiveness of the business case.

26. In fact, the LCOE corresponds to a net present value equal to zero.
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

131

ECONOMIC ASPECTS

The discount rate is the least dominant factor, given a cost profile essentially dominated byoperational expenditures (70% of the generation costs, see Figure 6.5, right). This cost structure issomehow similar to that of fossil fuel plants, which confers a certain economic advantage to better
withstand market shifts and improves the economic rationale for flexible operations, which
increases the overall value of LTO of existing fleet (IEA/NEA, 2020).
The thinner LTO bands compared to new build reflects the higher predictability and lower
project risks of LTO refurbishments. Potential cost overruns and shorter operating time frames
can be absorbed more easily than reductions in the plant’s availability and/or electricity prices.
Longer LTO periods tend to improve the overall economics but do not change the main trends.
O&M and fuel cost variations are more unlikely to happen given the stability of operation
expenditures in nuclear power (see Figure 6.6, left). Nevertheless, this does not prevent nuclear
operators from undertaking continuous efforts to reduce OPEX and improve the overall economicsof plants.

Figure 6.6: Sensitivity analysis of the LCOE of new build, and LTO of nuclear power plants
LTO 10 years

LTO 20 years

Load factor

Load factor

Overnight costs

Overnight costs

Lifetime

Lifetime

Discount rate

Discount rate
-10

0

10

20

30

-10

200

200

180

180

160

160

140

140

120
100
80
60

5

10

15

20

25

120
100
80
60

40

40

20

20

0

0

Discount rate

LCOE [USD/MWh]

LCOE [USD/MWh]Capacity factor-50
10% 20% 30% 40% 50% 60% 70% 80% 90%

0 2% 4% 6% 8% 10%12%14%16%18%20%

Source: OECD/NEA, using data from IEA/NEA (2020).

132

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

6.2. Recovering the costs of LTO
Despite LTO being one of the most cost-competitive, low-carbon technology options, this does notnecessarily mean that it recovers all of its generation costs under all circumstances to remain
profitable. In some regions, nuclear power plants close prematurely for market reasons. Enabling
LTO thus requires a comprehensive economic analysis that assesses both the technology costs
and revenue trends or market prospects (see Figure 6.7). It is the combination of both of these
dimensions, under regulatory compliance of course, that will trigger the final investment for LTO
of a nuclear power plant.
On the other hand, current electricity markets are designed to adequately reflect over timethe value of the system through marginal cost pricing mechanisms. The system value includes
the volume of electricity generation and the delivery of electricity where needed at any moment,satisfying certain quality standards (i.e. frequency). In this sense, generators are both energy(i.e. energy-only markets) and grid service providers (i.e. system adequacy and ancillary services).
In order to be sustainable and maximise social welfare, the electricity and the associated grid
services must also be low-carbon and resilient. In theory, current market designs ensure, in the
short term, optimal dispatch at the lowest cost for the customer while providing the right signal
to ensure, over the long-term, optimal capacity adequacy. In practice, markets face somedifficulties reconciling all of these system features and require support mechanisms to guide lowcarbon investments, especially in the long-term. As a result, those power markets encompassing
a series of measures to promote long-term decarbonisation, affordability and security of supply
will more likely benefit LTO.

Figure 6.7: Qualitative representation of the system value
and technology cost for LTO
Decommissioning andwaste management fee
Taxes

USD per MWh

LCOE
Support mechanisms
Ancillary services
Capacity
EnergyRevenues

Costs

6.2.1.Insights in the decision-making process for continuing operation
In the decision-making process to continue (or completely cease) operations of an existing
nuclear power plant, many interrelated factors (i.e. policy, technical, regulatory and economic)
come into play. The different chapters of the present report cover all of these factors and provide
an overall appreciation of the holistic approach necessary to assess LTO decisions. From an
economic perspective, the following key criteria can be considered (NEA, 2012):•

existing production and asset portfolio of the country;•

energy policy of the country, including aspects such as taxes, carbon policy and securityof supply aspects;

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

133

ECONOMIC ASPECTS•

new availability factor of the plant after refurbishment and the predictability of future
electricity prices;•

need for equipment upgrades and replacements, associated overnight costs and LCOE;•

other risks and uncertainties related to the site, the political situation, and financial
and/or regulatory aspects.

The costs, therefore, do not provide the full picture, and utilities usually include theirevaluation price projections and policy factors 27 in different scenarios to account for all potential
risks and adjust their strategy accordingly. Depending on the timescale, the expenses that caneffectively be managed by the utility are, in addition, not the same, which directly influences
operational decisions.

Short term
In the short term, the operation of a power plant is justified if at least the marginal costs arerecovered. The marginal costs are essentially fuel costs and variable O&M costs that varydepending on the technology. When electricity prices are low, fossil-fired plants, which are
dominated by fuel costs, improve their economics by reducing the power output or even bymothballing their production until prices can be recovered. For high fixed cost technologies suchas nuclear power, the economic optimum is to operate as baseload power. However, in a very
long-term perspective, even fixed costs become variable.

Long term
In the long term, all of the expenditures (i.e. fixed and variable) are included in the decisionmaking process of continuing operations. LTO investments are evaluated in the context of a longtime frame because they need several years (or even decades) to be completely amortised. LCOE
(see Table 6.1) and/or NPV-based approaches are commonly used to inform the final decision.
Revenues play a central role in the economic outcome (see Figure 6.6), and they are usuallyestimated using electricity price and other derivative 28 forecasts under different conservative
scenarios. If the LCOE is too high (or the NPV is negative in most scenarios), the company may
decide to cease nuclear operations completely. It is therefore necessary to understand the main
factors governing electricity market trends in the long term, as well as the main regulatory andpolicy strategies that can be harnessed to address potential challenges.

6.2.2.Market trends
Energy-only markets and their emerging shortcomings
Energy-only markets are the main revenue source for all power generators in current electricity
systems. There are essentially two types of energy-only markets: regulated and deregulated. In
regulated markets, vertically-integrated utilities centralise and co-ordinate investment
decisions in the entire value chain. 29 The overall economic viability of the investment is ensured
by regulated electricity tariffs set by market regulators. In the 1990s, on the other hand, anumber of regions and countries (e.g. Europe and some states in the United States) initiated thederegulation of electricity markets, unbundling the value chain and introducing competitivemarkets in generation and retail activities.
At the generation level, this implies that all dispatch and investment decisions in new
capacity are strictly commercial and properly incentivised by electricity prices. In the short term,
generators participate in day-to-day bids according to their marginal costs, balancing demandand supply over different time frames (i.e. marginal price-setting mechanisms). The resulting
price ensures optimal dispatch at the lowest cost for the final consumers, while at the same

27. Through higher risk premia, for instance.
28. Especially if the utility hedges future income to a large extent.
29. The electricity value chain is formed by the generation, transport, distribution and retail of activities.

134

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

time fostering innovation. In the long term, electricity prices should trigger the necessary
investments to guarantee optimal capacity adequacy in the system.
Empirical evidence indicates, however, that current deregulated electricity markets may
suffer from a “missing money” problem, with prices that do not adequately reflect the value of
new capacity investments to meet customer expectations and a reliable electricity supply (NEPP,
2016; Hogan, 2017). This is particularly the case for low-carbon capacity, since the high-fixed
cost structure of this type of asset requires long-term price stability to become economicallyattractive for investors. Over the last ten years, most of the investments in deregulated markets
have not been incentivised by the market but rather by specific regulations, subsidies oradditional long-term payment mechanisms not emanating from energy-only markets (seeFigure 6.8). Only a small share of total investment is merchant, as utilities prefer to undertake
investments under support mechanisms to reduce their exposure to merchant risk, reflecting
the limits of current deregulated markets to attract capital-intensive, low-carbon investments
relying solely on market price signals.
These trends are set to continue over the next decade with significant, low-carbon
investments needed to meet the emission targets set by the Paris Agreement. In practice,deregulated electricity markets may become more hybrid, combining deregulated mechanisms
to ensure optimal dispatch in the short term, with some sort of public intervention and planning
to properly guide investment trends and maximise system value and social benefits in the longterm (Roques, 2017).

Figure 6.8: Capacity additions in Europe by market regulatory framework
500

GW

450

100%
Monopoly

Liberalised
market

90%

400

80%

350

70%

300

60%

250

50%

200

40%

150

30%

100

20%

50

10%

0

0%
1971-1980

1981-1990

1991-2000

2001-20102011-2020

Clean – support
mechanisms
Conventional –supportmechanisms
Clean –
merchant
Conventional –merchant
Regulated tariffs% Regulated

2021-2030

Source: OECD/NEA, adapted from Roques (2021).

In order to properly assess the recovery of LTO costs over a given period, it is necessary tounderstand the main drivers influencing the formation of wholesale electricity prices inelectricity markets.
The irruption of massive amounts of variable renewables (mainly wind and solar photovoltaic)
over the last decade, underpinned by governmental support (see Figure 6.8) is pushing wholesale
electricity prices down. Given the very low or zero marginal costs associated with VRE, they aredispatched ahead of any other technology, setting the final price at a lower marginal cost (i.e. themerit order effect). At high levels of VRE generation (and protected by out-of-the-market support

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

135

ECONOMIC ASPECTS

mechanisms), VRE can become marginal units 30 and bid at zero or even negative prices. Episodesof zero or negative prices have been rising in Europe over the past years (see Figure 6.9) and could
continue in the absence of measures to improve system flexibility in the short term and/or the
implementation of more structural market reforms. This situation forces conventional generatorssuch as nuclear power plants to further rely on uncertain and more volatile periods, when capacity
is scarce, to recover their fixed costs, increasing overall risks and undermining their economic
viability. In some regions, such an approach may not be politically feasible since price spikes may
give rise to public concerns about market powers calling for administrative measures such as pricecaps (NEPP, 2016) or additional taxes.
Gas prices (or fuel costs) also play an important role in the formation of wholesale electricity
prices as gas plants are usually marginal units. The decline of global gas prices that has been
observed since 2012 has certainly contributed to lowering average wholesale electricity prices (EC,2018). At the same time, strong geographical variations in gas prices exist, with gas transportation
costs being higher than oil transportation costs. This results in three primary, segmented markets,with the United States presenting the lowest gas prices, 31 Asia the highest and Europe somewhere
in between. While increasing liquified natural gas (LNG) exports may contribute to homogenisinggas prices around the globe, gas market segmentation is also reflected, to some extent, inelectricity prices which are set at different levels depending on the region.
Other factors influencing wholesale electricity prices include electricity demand growth andcarbon pricing trends (IEA, 2019). Their relative importance varies from one country to another.

Figure 6.9: Number of negative, hourly wholesale prices
on selected, day-ahead trading platforms
350
300
250
200
150
100
50
0
1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6
2017

2018

2019

2020

Note: The selected trading platforms are: N2EX, EXAA/EPEX-AT, APX-NL, SEMO-IE, CROPEX-HR, BSP-SI, OTE-CZ, DK1 west, BPX-BE,
PNX-FR and EEX-DE.
Source: OECD/NEA, adapted from EC (2020).

As a result of the above factors, wholesale electricity prices have experienced various yearsof steady decline, thereby undermining the economic viability of LTO in some regions. Since
2012, 11 nuclear units in OECD countries have been retired purely for market reasons, more than
50% of them in the United States. In Europe, because of the higher gas and carbon prices, theoverall number of early closures for economic reasons is more limited, with some isolated cases
in Sweden (see Box 6.4 below). Overall, around 50% of the plant closures by 2025 will be directly

30. The marginal cost of the last unit of electricity produced, which sets the final electricity prices for agiven period.
31. Following the shale gas revolution.

136

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

motivated by the plant economics (i.e. market and techno-economic factors; see Figure 1.2). 32
Based on the positive attributes of LTO in terms of decarbonisation, affordability and securityof supply (see Chapter 2), this could lead to a net loss in the overall value of the system – andfor the society as a whole. Different options exist to address the existing shortcomings ofderegulated energy-only markets and foster the development of low-carbon systems in the longterm, including LTO. In some particular cases, revenue diversification might also be an option
to be explored in order to improve the economics of existing nuclear power.

Box 6.4: The impact of market conditions on LTO
The market is one the main causes of early closures of nuclear power plants following policy decisions. Trends
vary geographically, with the United States the country with highest number of closures for market reasons.
Operators around the world have made significant efforts to achieve more efficient operations and reduce
production costs. Nevertheless, in some cases, these efforts have been insufficient to offset the fall in power
prices, and additional policy measures and regulations are thus required to enable competitive LTO.
United States
Between 2008 and 2015, wholesale electricity prices dramatically dropped in the United States: around 36% in
the Midwest and 46% in the Mid-Atlantic regions (Haratyk, 2017). This low USD 30 per MWh range has been
typical for electricity prices in recent years, resulting mainly from stagnant electricity demand since the 2008
financial crisis, combined with the shale gas boom in 2010 and the penetration of higher shares of VRE. Gas
prices have more than halved since 2008, and they are 60% lower compared to prices in Europe, leading tomore severe market pressures for nuclear reactors in the United States (IEA, 2019). In the face of suchchallenges, twelve plants have been taken off the grid since 2013, eight of them essentially based on negative
market prospects, with five additional reactors to be retired by 2022 33 for similar reasons.

Figure 6.10: US nuclear operating capacity by market type, 2019
State policy

13%Power purchase agreement

2%Competitive

30%

Regulated

55%
0%

10%

20%

30%

40%

50%

60%

Nuclear capacity share
Source: EIA, 2019.

32. Note that, indirectly, positive market trends improve the economic case of LTO and enable more
extensive refurbishment than would otherwise not have made economic sense under more degradedmarket conditions.
33. Palisades, Byron 1 and 2 and Dresden 2 and 3. According to the nuclear operator Exelon, Bradwood and
LaSalle, nuclear power plants are also at risk of early closure for market reasons (S&P Global Platts,
2021a). Diablo Canyon units will be retired by 2025 for policy reasons (NEI, 2020).

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

137

ECONOMIC ASPECTS

The US market landscape is also quite heterogeneous in terms of market design, and mechanisms vary from one
state to another. In general, US reactors operate either in regulated or competitive markets. Two nuclear power
plants are selling their output under power purchase agreements, and some states support continuing operations
with specific state polices (see Figure 6.10 above). More specifically, around 30% of the installed capacity performs
under competitive markets and relies solely upon market signals to determine whether the plant should close orcontinue operations. These “merchant” plants are of course more exposed to market shifts and have a higher riskof shutting down prematurely than those owned by a regulated utility or a public power company.
The total production cost of the US nuclear fleet has fallen on average by almost 32% since 2012. Current
generating costs are on average USD 38/MWh for single units and USD 28/MWh for multi-unit sites (NEI, 2020).
Nevertheless, as of 2017, around two thirds of the nuclear fleet were still unprofitable, based on negative
revenue gaps, 34 with the Midwest, California and Texas the most challenging market environments for nuclear
energy (Haratyk, 2017; INL, 2017). The revenue gaps were on average USD 3.5-5.5/MWh, suggesting that mostof these closures could be avoided at a cost lower than subsidising VRE and other support mechanisms.
Recently, zero-emission credits (ZECs) have been approved in some states to support the continuing operationof nuclear power plants, based on their low-carbon attributes (see Box 6.5).
SwedenFour plants (i.e. Oskarshamn units 1 and 2, and Ringhals units 1 and 2) were retired in Sweden in 2015 for market
reasons. Nordic bidding zones observe structurally lower wholesale electricity prices than the rest of Europe,
given the abundance of hydro and wind power and the stagnating electricity demand. In addition, these closure
decisions were taken at a time when the nuclear capacity tax of EUR 8 per MWh was in place, but this tax wascompletely abandoned in 2018 as part of the parliamentary energy agreement reached in 2016. In fact, at thetime that this tax was introduced (before the 1990s) power prices were high enough to ensure sufficient profit
margins. However, because of falling power prices, the overall tax burden ended up representing around 30-40%
of total revenues for nuclear operators. More recently, Swedish wholesale electricity prices have been steadily
increasing (i.e. since 2016), partly as a result of the EU Emissions Trading System (ETS) reform, further improving
the competitiveness of the remainder of the nuclear fleet in the country (IEA, 2019).

Energy-only market reforms
As illustrated in the previous section, energy-only markets have some limits in terms of sending
long-term price signals that would ultimately enable the system to encompass value features,such as capacity, flexibility (i.e. dispatchability) and low emissions. The former two are becoming
increasingly important in light of massive additions of VRE and uncertain prospects for the largescale deployment of low-carbon, flexible solutions (e.g. storage, demand-side response, sector
coupling). A range of additional remuneration mechanisms have been introduced to address theshortcomings of energy-only markets and foster low-carbon capacity investments in future. Theirtype, design and revenues vary according to national regulatory frameworks, energy policy
objectives and system-specific constraints. While some of these mechanisms are quite
straightforward and could rapidly support LTO in most unfavourable markets, questions remain
concerning whether these additional remuneration mechanisms are to be a transitional measureor whether more structural market reforms may be needed to build and efficiently operate theclean energy infrastructures of tomorrow.

Capacity remuneration mechanisms

Capacity remuneration mechanisms provide additional revenues to operators that ensure thata certain level of capacity will be available at a given point in time according to the system’s
needs, and dictated by national transmission system operators to meet peak demand. There are
essentially two types of capacity mechanisms: strategic reserves and capacity markets.

34. The difference between the electricity prices and total generating costs of a nuclear unit.

138

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

Strategic reserves are meant for capacity that is expected to run a few times per year andthat would be unprofitable otherwise without this type of special support. Its establishment isquite straightforward and has a limited impact on competitive energy-only markets. 35 On theother hand, capacity markets remunerate capacity that will be used more frequently, forinstance to accommodate power fluctuations associated with high shares of VRE in the system.
Typically, dispatchable technologies such as nuclear power, with its high-capacity credits 36(approximately 95%), are eligible to bid in capacity markets.
Over the last years, a number of regions (e.g. some countries in Europe and states in the
United States) have introduced capacity payments to overcome existing shortcomings inenergy-only markets so as to ensure long-term system adequacy. The introduction of capacity
markets should lead to an increase of installed capacity and enhance the ability of the system
to meet peak demand at all times. In general, the revenues from capacity markets remain low
compared to energy-only markets. The share of nuclear power in overall capacity eligible forcapacity payments is typically lower percentage-wise than the share for gas plants (Jenkin et al.,2016; Ofgem, 2020). Such aspects largely depend on the specificities of each electricity system.
In some cases, ill-designed capacity markets may encourage over-investments and distortcross-border trade and competition, especially if different national initiatives are developed in
an uncoordinated manner (NEPP, 2016). 37



Direct support mechanisms

The feed-in tariff, feed-in premium, contract for difference and production tax credit are someexamples of direct support mechanisms. In their design, these instruments either isolate lowcarbon generators from market prices by guaranteeing a fixed revenue per unit of output, reduce
the exposure to market risk or provide a tax credit for every MWh produced. In principle, they
can be applied to any low-carbon technology and are the result of various policy motivations
seeking to: i) support a specific technology; ii) recognise the economic disadvantages of lowcarbon generators in current electricity markets; or iii) compensate low-carbon electricity
generation (IEA/NEA, 2020). Thus far, these support mechanisms have been very effective in
fostering the deployment of VRE and lowering their production costs (Figure 6.8). The protectionthat they confer from market shifts, however, have also induced some market distortions(e.g. generators bidding at negative prices in some countries, system costs not properlyinternalised) that have underscored the limits of current energy-only markets.
To date, the introduction of support mechanisms for LTO of nuclear power plants has beenvery limited. This can be explained by the competitiveness of this technology option, as well as bypolicy reasons. In the United States, where market pressures are significant, ZECs have been theprivileged solution to sustain low-carbon capacity from nuclear power (see Box 6.5). While ZECs
have proven to be an effective measure in the short term, additional efforts and more structuralreforms may be necessary to support widespread LTO in the United States.

35. Strategic reserves cannot participate in the regular wholesale market but are activated by grid operators
upon demand.
36. The capacity credit indicates how much a technology is relied upon to meet peak demand from aplanning perspective (IEA/NEA, 2020).
37. This is typically the case in Europe.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

139

ECONOMIC ASPECTS

Box 6.5: Pricing emission avoidance for nuclear power through ZECs: The US experience 38
Zero emission credits (ZECs) are payments that electricity generators receive to compensate for the valuable
attribute of not emitting greenhouse gases during the production of electricity. ZECs work similarly to renewable
obligations that support renewable energy production in many US states. Similar to renewable energy credits(RECs) that are generated by wind and solar generators and sold to utilities, ZECs are sold to utilities that are
required to purchase a certain number of these credits from low-carbon generators. The utility then rolls the costof the credits into electricity customers’ bills, similar to the increase in retail electricity prices that would be
expected through the introduction of a carbon tax or an emission trading system. From the point of view of a
nuclear plant owner, ZECs provide a source of revenue for the service of reducing climate change-inducing
greenhouse gas emissions, which had previously been provided free of charge. Some state air regulators andpublic health advocates have recognised these clean-air benefits, without anyone directly paying for thesebenefits directly. At the very least, ZECs internalise the service of low-carbon power production.
Since the idea of a ZEC is to provide the incentive to preserve non-emitting generation, the price of the ZEC
should be related to the value of the avoided emissions. Initial ZEC programmes in New York and Illinois used
the social cost of carbon (SCC) as the starting point for determining credit value. The SCC indicates the longterm economic impact of emissions. A central estimate of the SCC was established at USD 42 per tonne of CO2.
On this basis, regulators converted the SCC into a USD-per-megawatt-hour value by multiplying the SCC by
the average emissions generated by plants running on natural gas or coal. For instance, New York set the valueof the ZEC at USD 17.48/MWh. This is higher than the revenue gap observed in most US plants (INL, 2016).
How the basic ZEC framework operates is illustrated in Figure 6.11. Without ZEC, there is a one-to-one
relationship between the market price of electricity and the final value received by the nuclear generator, as
would happen in standard electricity markets. When a ZEC is introduced, the wholesale electricity price directly
increases from a pre-set level. When electricity prices exceed a certain threshold, the value of a ZEC decreases
based on a phase-out provision. In other words, in current designs, ZECs act as a price floor that is gradually
removed as market prices rise, demonstrating the extent to which current ZEC programmes are temporary
expedients to compensate for low electricity prices.
Figure 6.11: Operation of the ZEC framework

Market revenue plus ZEC(USD per MWh)

Revenues without ZEC programme

Revenues with ZEC programme

90

90

80

80

70

70

60

60

50

50

40

40

30
20

20

10

10

30

0

0
20 25 30 35 40 45 50 55 60 65 70 75 80

20 25 30 35 40 45 50 55 60 65 70 75 80

Wholesale electricity price(USD per MWh)

Wholesale electricity price(USD per MWh)

Source: IEA/NEA 2020.

38. Most of the content of this box is taken from IEA/NEA (2020) and it is based on a personal contribution
by Mathew P. Crozat, Senior Director, Business Policy, Nuclear Energy Institute (NEI), United States.

140

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

While ZECs are an innovative policy instrument to remunerate low-carbon producers for the service ofemission avoidance, they also impose an added cost on utilities, and to the extent that the latter can pass themon, to electricity consumers. ZEC programmes have thus been challenged in federal courts. It is also widely
accepted that more widespread carbon pricing would be a more robust solution to these state-by-statesolutions. From an economic point of view, it would be preferable if the contribution to emission avoidanceby nuclear power, renewables and hydro were correctly valued at the SCC in a comprehensive carbon
management policy framework. However, carbon pricing prospects seem remote in a US context. Overall, theZEC programme could constitute a blueprint for remunerating emission avoidance in nuclear power, and the
US experience could be useful for other countries.



Carbon pricing

Carbon pricing mechanisms internalise the negative externalities of burning fossil-fuels(e.g. climate change, air pollution) by setting a price on carbon and making carbon-intensive
generation less competitive. There are two primary means of establishing a carbon price:i) governments can impose a carbon tax to encourage a switch to less carbon-intensive
production or consumption; or ii) they can introduce a cap-and-trade system (e.g. in Europe, the
EU Emissions Trading System [EU ETS]). Hybrid approaches can also be adopted. The potential
advantages and disadvantages of each mechanism are out of the scope of the present study, butthese are discussed in more detail in IEA/NEA (2020).
As of April 2020, 20% of the global greenhouse gas emissions were covered by 61 carbon
pricing initiatives: 31 using market-based emission trading systems and 30 using carbon taxes.
Carbon prices vary widely across schemes, from less than USD 1 per tonne of CO2 equivalent(tCO2-eq) to USD 127/tCO2-eq (i.e. the Swedish carbon tax). Since 2017, carbon prices in Europe
have been steadily increasing after a reform limiting the number of carbon allowances. In May
2021, carbon prices in Europe reached 50 per tCO2, a tenfold increase compared to price levels
prior to the reform. Overall, carbon prices remain low, meaning that they have a modest impact
on driving electricity prices up. Most of the initiatives set carbon prices lower than USD 30 per
tCO2 with only 5% being consistent with Paris Agreement pathways (IEA, 2020). 39
Regarding the potential effects of carbon pricing, it is possible to identify different timescales.
In the short term, the increase in the generation costs of carbon emitters will favour fuel switching(e.g. coal to gas). In the mid to long term, capital investment and demand patterns could change,
as could technology deployment trends. In all situations, nuclear power and the existing fleet will
directly benefit from carbon pricing approaches given its low-carbon emissions. At the same time,the distributional effects of carbon pricing 40 should not be neglected as they can raise social equity
and acceptance concerns. There are indications that subsidising emission avoidance throughsupport mechanisms is considered a politically more sustainable solution in a number of OECD
countries (IEA/NEA, 2020).
In conclusion, both support and carbon pricing mechanisms are aimed at reducing
emissions and properly recognising low-carbon emitters, but the policy and distribution
implications are not the same. Thanks to a greater understanding and growing experience withthese mechanisms, governments have a solid base to design packages encompassing both
solutions in order to find the right balance between economic efficiency, emission reductions,and social equity and acceptance.

39. Explicit carbon price levels consistent with the Paris Agreement should be at least USD 40-80 tCO2-eq
by 2020 and USD 50-100 tCO2-eq by 2030 (IEA/NEA, 2020).
40. Welfare transfers between different types of generators, as well as between electricity consumers,
generators and governments, amount to USD billions annually (IEA/NEA, 2020).
LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

141

ECONOMIC ASPECTS

Flexible operations
From a technical perspective, nuclear power plants are dispatchable generators, and extensive
operational experience exists on their ability to provide services to the grid in terms of inertia,
frequency control and load following. The dispatchability attributes of nuclear reactors can beenhanced, and some operators might consider implementing plant retrofits for flexible
operations if the economics are sufficiently attractive (see Chapter 3).
The value that could be captured by nuclear reactors operating more flexibly, however,remains bounded by the characteristics of the system. The high fixed costs of nuclear makethis technology economically suitable for baseload operation. Any variation in the capacity
factor resulting from flexible operation will come at a significant economic penalty. On theorder hand, more frequent and longer periods of zero or negative wholesale electricity prices
in an electricity system with high shares of VRE may push utilities to perform load variations
so as to stabilise prices and explore additional revenues arising from arbitrage considerations(i.e. saving fuel for periods with high electricity prices). The associated economic case forflexible operations in such contexts must be sound – and most likely supported by specificmarket regulations. Otherwise, baseload operations will naturally emerge as the mosteconomic option for existing reactors.

Non-electric applications
Existing nuclear power plants can provide products other than electricity, which could help todiversify their revenues and better withstand electricity market changes after some plant
adjustments. These products include heat production for district heating applications and the
production of hydrogen, as well as the generation of radioisotopes. Such applications are not anovelty as they have already been implemented in the past in some operational reactors, inparticular district heating and radioisotope generation applications. 41 The first pilot projects forhydrogen generation in existing reactors are under development in the United States. 42 The
need to decarbonise hard-to-abate sectors and the associated market opportunities are reviving
interest in nuclear non-electric applications.
The economic case for these types of applications relies on an opportunity cost assessment,
the principle being to use the power generated in the core for other purposes when electricity
prices are not attractive. The different opportunities currently being assessed are either pilot
projects or are limited to specific plants close to demand or niche applications. Their economic
viability and widespread deployment to support LTO remains uncertain, and is strongly subject
to the competitiveness of other alternatives, especially for heat and hydrogen production. 43 In
the case of radioisotopes, the impact on power output is negligible and can be considered as aco-product, directly improving the plant’s revenues. The safety evaluations necessary for the
implementation of non-electric applications should not be neglected as they entail licensing
costs and additional investments that may not be recovered over the LTO period.

41. For instance, the two units of the Beznau nuclear power plant in Switzerland have operating in cogeneration mode since 1985, supplying the Refuna district heating grid with 80 MWth. CANDU reactors
take advantage of their online refuelling capabilities to ensure the generation of radioisotopes on areliable basis, especially for medical radioisotopes that have to be supplied just-in-time given theirshort lifespans (e.g. molybdenum-99).
42. Various utilities, in collaboration with national laboratories and the US Department of Energy, areexploring the economic potential of hydrogen generation with low-temperature proton exchange
membrane electrolysers and high temperature electrolysis at some specific plants. The technical andsafety cases are making good progress. Currently, all of the hydrogen being produced serves the exclusive
demand of the individual plants, but the objective in future is to scale-up the electrolysis facilities in orderto improve the economics and sell hydrogen to nearby industrial customers (e.g. refineries, cement
production facilities) (S&P Global Platts, 2021b).
43. Radioisotope generation can be considered as a niche market with a tight supply. These conditions
significantly improve the business case.

142

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

Key findings•

Most LTO costs fall into three main categories: i) LTO programme; ii) the replacement of heavy components
and other works; or iii) post-Fukushima costs. These categories can face significant shortcomings in practice,
however, given the variety of accounting conventions and project scopes, which usually include expenses
not strictly related to LTO. At the same time, actual investment patterns tend to be continuous andincremental rather than upfront. As such, it is possible to identify excess investments beyond regular
maintenance costs over a given period, which can conservatively be attributable to LTO.

•

LTO overnight construction costs can be conservatively estimated at USD 450-950 per kWe, which would
lead to an LTO LCOE roughly ranging between USD 25-50 per MWh for most of the world’s nuclear fleet.
Consequently, LTO remains one of the most cost-competitive, low-carbon technology options in many
regions, as confirmed by other recent studies (IEA, 2019; IEA/NEA, 2020).

•

LTO project risks are low given their smaller and simpler scope compared to new build, and existing welldeveloped industrial capabilities. As a result, nuclear operators can carry these projects in their balance
sheets with limited financing costs. At the same time, the cost structure of existing reactors is dominated byoperational expenditures, which confers an economic advantage to withstand changing market conditions
while improving the economic rationale for flexible operations. The share of fixed costs is neverthelesssignificant, increasing the exposure of existing plants to market risks, especially in those regions withsustained, low electricity prices.

•

The result has been early closures for purely market reasons in some regions. These trends also reflect thelimits of deregulated energy-only markets to secure low-carbon capacity in the long term. Various
regulations and mechanisms are being used to support the development of low-carbon technologies,
and these could be extended to LTO. The case of zero emission credits in the United States illustrates theeffectiveness of such measures, but more in-depth and structural reforms may be required to reconcile
low emissions, affordability and security of supply in current electricity markets. In some specific plants,
revenue diversification based on non-electrical applications could be explored.

References
DGEC (2015), “Audit sur les modalités d’évaluation des charges brutes permettant le calcul desprovisions de déconstruction des réacteurs d’EDF en cours d’exploitation”, Direction
générale de l’énergie et du climat, France, www.ecologique-solidaire.gouv.fr/sites/
default/files/061015Synth%C3%A8se%20 rapport%20audit%20Dampierre_0.pdf.
D’haeseleer, (2013), Synthesis on the Economics of Nuclear Energy: Study for the European Commission,
DG Energy, Final Report, KU Leuven, Leuven, www.mech.kuleuven.be/en/tme/research/energy_environment/Pdf/wpen2013-14.pdf.
EC (2020), Quarterly Report on European Electricity Markets with special focus on extra-EU electricity
trade, Market Observatory for Energy, DG Energy, Volume 13, Issue 2, Brussels,
www.ukrenergoexport.com/sites/default/files/2020-11/quarterly_report_on_european_electricity_markets_q_2_2020.pdf.
EC (2018), Study on energy process, costs and their impact on industry and households, European
Commission, Brussels, https://d1owejb4br3l12.cloudfront.net/sites/default/files/aboutus/case-study/energy-prices-costs-eu-study.pdf.
EIA (2019), “Five states have implemented programs to assist nuclear power plants”, Today in
Energy, www.eia.gov/todayinenergy/detail.php?id=41534.
Haratyk, G. (2017), “Early nuclear retirements in deregulated U.S. markets: Causes, implications
and policy options”, Energy Policy, No. 110, pp-150-166, www.sciencedirect.com/science/
article/abs/pii/S0301421517305177.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

143

ECONOMIC ASPECTS

Hogan, F. (2017), “Follow the missing money: Ensuring reliability at least cost to consumers in
the transition to a low-carbon power system”, The Electricity Journal, No. 30, pp. 55-61,
www.sciencedirect.com/science/article/pii/S1040619016302512!.
IAEA (2018), Economic Assessment of the Long Term Operation of Nuclear Power Plants: Approaches andExperience, IAEA, Vienna, www-pub.iaea.org/MTCD/Publications/PDF/PUB1813_web.pdf.
IEA (2020), Implementing Effective Emissions Trading Systems: Lessons from international experiences,
IEA, Paris, https://webstore.iea.org/implementing-effective-emissions-trading-systemslessons-from-international-experiences.
IEA (2019), Nuclear Power in Clean Energy Systems, IEA, Paris, www.iea.org/reports/nuclear-powerin-a-clean-energy-system.
IEA (2018), World Energy Outlook 2018, IEA, Paris, www.iea.org/reports/world-energy-outlook2018.
IEA/NEA, (2020), Projected Costs of Generating Electricity, 2020 Edition, OECD Publishing/IEA, Paris,
www.oecd-nea.org/jcms/pl_51110/projected-costs-of-generating-electricity-2020-edition.
INL (2017), Economic and Market Challenges Facing the U.S. Nuclear Commercial Fleet – Cost andRevenue Study, Energy Systems, Strategies, Assessments, and Integration, INL, Idaho Falls,
https://lwrs.inl.gov/Systems%20Analysis%20and%20Emerging%20Issues/Economic_Market_Challenges_Facing_the_US_Nuclear_Commercial_Fleet_Cost_Revenue_Study.pdf.
INL (2016), Economic and Market Challenges Facing the U.S. Nuclear Commercial Fleet, Energy Systems
Strategic Assessment Institute, INL, Idaho Falls, https://gain.inl.gov/Shared%20Documents/Economics-Nuclear-Fleet.pdf.
MITECO (2018), “Comisión de Expertos de Transición Energética: Análisis y propuestas para ladescarbonizacion”, Ministerio para la Transición Ecológica y el Reto Demográfico, Spain,
http://www6.mityc.es/aplicaciones/transicionenergetica/informe_cexpertos_20180402_vedi
tado.pdf.
NEA (2016), Costs of Decommissioning Nuclear Power Plants, OECD Publishing, Paris, https://doi.org/
10.1787/9789264255555-en.
NEA (2015), Nuclear New Build: Insights into Financing and Project Management, OECD Publishing,Paris,
www.oecd-nea.org/jcms/pl_14904/nuclear-new-build-insights-into-financing-andproject-management.
NEA (2013), The Economics of Back End and Nuclear Fuel Cycle, OECD Publishing, Paris, www.oecdnea.org/jcms/pl_14764.
NEA (2012), The Economics of Long-Term Operation of Nuclear Power Plants, OECD Publishing Paris,
www.oecd-nea.org/ndd/reports/2012/7054-long-term-operation-npps.pdf.
NEA (Forthcoming), On the Role and Economics of Nuclear Cogeneration in a Low-Carbon Energy Future,
OECD Publishing, Paris.
NEI (2020), “Nuclear Costs in Context”, Nuclear Energy Institute, www.nei.org/resources/reportsbriefs/nuclear-costs-in-context.
NEPP (2016), Ten statements about the future power market design, North European Power
Perspectives, www.nepp.se/etapp1/pdf/10_slutsatser_hela_low.pdf.
Jenkin, T., et al. (2016) Capacity Payments in Restructured Markets under Low and High Penetration
Levels of Renewable Energy, NREL, Washington, DC, www.nrel.gov/docs/fy16osti/65491.pdf.
NucNet (2020), “Regulator Says All Nuclear Plants Meet New Independent Cooling Requirements”,
www.nucnet.org/news/regulator-says-all-nuclear-plants-meet-new-independent-coolingrequirements-12-5-2020.
Ofgem (2020), Annual Report on the Operation of the Capacity Market in 2019/20, Ofgem, London,
www.ofgem.gov.uk/system/files/docs/2020/09/2019-20_annual_report_on_the_operation_of_cm_0.pdf.

144

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

ECONOMIC ASPECTS

OPG (2015), “Darlington Nuclear Refurbishment Project, Report to Board of Directors”, Ontario
Power Generation.
Payen, L., E. Willot (2019), “Evolutions techniques liées à la 4ème Visite Décennale: case de
Tricastin”, Poursuivre le fonctionnement des réacteurs nucléaires après 40 ans, Journée Technique,Sfen, Paris.
Roques, F., Finon, D. (2017) “Adapting electricity markets to decarbonisation and security of supply
objectives: Toward a hybrid regime?”, Energy Policy, No. 105, pp. 584-596, www.science
direct.com/science/article/abs/pii/S0301421517301106.
Roques. F., (2021), “Market design for financing capital intensive low-carbon technologies”,
NEA/IFNEC Financing Initiative, Kick-off Virtual Workshop, www.ifnec.org/ifnec/jcms/
g_13772/fabien-roques-associate-professor-dauphine-university-executive-vice-presidentcompass-lexecon.
S&P Global Platts (2021a), “Illinois to probe Exelon nuclear fleet finances”, Nucleonics Week,
Vol. 62, No. 3.
S&P Global Platts (2021b), “Nuclear power plants could become hydrogen ‘energy parks’”,
Nucleonics Week, Vol. 62, No. 3.
SWECO (2016), Ekonomiska förutsättningar för skilda kraftslag, SWECO, Stockholm, www.sou.gov.se/
wp-content/uploads/2017/01/Underlagsrapport_Sweco_Ekonomiska-förutsättningar-förskilda-kraftslag.pdf.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

145

CONCLUSIONS AND POLICY RECOMMENDATIONS: ENABLING LONG-TERM OPERATION

7. Conclusions and policy recommendations:
Enabling long-term operation

More and more countries are pledging to reach carbon neutrality by 2050, and most of thesecountries are currently operating nuclear reactors. Achieving the objective of carbon neutrality
will be an enormous endeavour, requiring drastic emission reductions and a profoundtransformation of today’s economic models in the coming decades. Against this backdrop, it has
become increasingly apparent that phasing out existing nuclear capacity could make thetransition towards the clean energy systems of tomorrow unnecessarily more challenging.
Affordability and electricity security concerns are also at the core of sustainable energy policies,
and the contribution of the existing nuclear fleet worldwide to each of these dimensions should
not be neglected. Licence extensions, however, cannot be solely decided based upon policy
priorities. They are first and foremost the result of safety considerations, which then must be
evaluated under the lens of technical, operational and economic factors. Accordingly, the present
report proposes a holistic approach that offers an overview of all of these factors in an attempt toidentify the key enablers for long-term operation (LTO) of nuclear power plants. The approachassesses to what extent the internal capabilities (i.e. ageing, operational and human aspects, costs)of existing reactors would allow nuclear technology to remain competitive in the current andnear-term external context (i.e. regulations, market and policy trends).
As demonstrated in the report, most of the risks that today prevent nuclear reactors fromoperating longer are driven largely by policy issues. In fact, early closures of nuclear reactors
are primarily motivated by political decisions. In some regions, sustained, low wholesale pricesthat do not reflect the climate and reliability attributes of existing nuclear reactors are pushingsome utilities to cease operations earlier than expected. While ongoing efforts to keep thehighest safety standards and reduce operational costs must remain key priorities for the nuclear
industry, government and policymakers nonetheless have a key role to play in supporting LTO
so as to facilitate decarbonisation strategies.

LTO is a safe and mature solution to foster ambitious decarbonisation strategies
With 444 reactors in operation worldwide, nuclear power remains one of the main sources of
low-carbon electricity generation in advanced economies. Long-term operation (LTO) trends
continue to increase, with more than 30% of the existing nuclear fleet already operating beyond
its initial design lifetime, according to different national regulations. Without widespread
licence extensions in the next decade, annual carbon emissions could increase by 1.2 gigatonnesof carbon dioxide (GtCO2) by 2050 (assuming that nuclear capacity is replaced by gas), putting
emissions trajectories under stress.
At the same time, LTO is supported by an extensive scientific basis on the main ageing
mechanisms and their management, as well as by a considerable amount of operating experience.
If utilities continue to implement enhanced ageing management programmes using technicalevidence already available, while performing the necessary repairs and replacements, long-term
operation should not face any major generic technical barriers. Provisions in safety margins, andcontinuous monitoring through robust ageing management programmes and research, will
nevertheless be necessary in order to properly anticipate and manage potential technical risks
that may arise, particularly over very long operating periods.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

147

CONCLUSIONS AND POLICY RECOMMENDATIONS: ENABLING LONG-TERM OPERATION

Key policy recommendations [I]1.

Maintain existing low-carbon capacity: Decarbonising the electricity system will be even more difficult
if existing low-carbon nuclear capacity is not included in the equation. LTO is a safe and expeditious
solution to avoid carbon emissions for decades to come and to manage emission reduction trajectories
in a predictable manner under ambitious decarbonisation pathways.

2.

Enlarge the technical basis of information on ageing mechanisms and their management: Current
LTO trends have been possible thanks to extensive research that has been conducted over the years.
Longer operational time frames will increase the demands on materials and life-limiting components andwill require continued R&D efforts to provide the necessary technical evidence for safe operation.
Initiatives fostering international collaboration on lessons learnt in ageing management should continue
to be pursued.

Existing nuclear power plants can be enhanced to cope with a changing environment
Existing nuclear reactors have never ceased to evolve from a technical and organisational
perspective. Most of the components of a nuclear power plant can be replaced during regular
maintenance outages, as well as during more extensive LTO refurbishments. These replacements
attenuate the impact of ageing and allow operators to implement the necessary safety upgradesin accordance with the latest available regulations, knowledge and operating experience. These
activities are complemented with ageing management programmes involving the entire
organisation to continuously monitor the performance of life-limiting components (e.g. vessel,
containment building) and take corrective actions when necessary.
Beyond ageing considerations, LTO refurbishments are also an excellent opportunity to
implement plant enhancements that will allow for economic improvements in a changing
context, including power uprates, information and control (I&C) upgrades (e.g. replacement of
analogue equipment with digital one), flexible operations and overall plant modernisation. In
some specific cases, non-electrical applications such as district heating, hydrogen production
and radioisotope generation could be explored. The accumulation of extensive past and recent
experience on these projects, combined with well-established governance and collaborative
frameworks, are also unique mechanisms to accelerate potential adaptations and perform LTO
based upon best practice.

Key policy recommendations [II]

148

3.

Support new technologies and plant enhancements: Nuclear operators have at their disposal robust
technical options to enhance and adapt their assets to an evolving context. With stable policies and risksharing initiatives, governments can facilitate their adoption and bring additional performance
improvements during LTO.

4.

Foster co-operation to capitalise on extensive industrial experience: An increasing number of utilities
around the world are undertaking LTO refurbishments and implementing new technologies. External peer
reviews and international operational experience sharing have proven to be effective tools to secure bestpractices and to enable longer operating periods and plant adaptations. Timely dialogue and co-operation
with regulators are in most cases possible and help to accelerate the adoption of the most innovative
solutions.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

CONCLUSIONS AND POLICY RECOMMENDATIONS: ENABLING LONG-TERM OPERATIONThe supply chain is critical in sustaining operational and economic performance
LTO is one of the most cost-competitive, low-carbon technology options in many regions with alevelised cost of electricity (LCOE) ranging between USD 25-50 per megawatt hour (MWh). Cost
trends have revealed that LTO refurbishments are well advanced in terms of stages of positive
learning, with a constant inflow of projects that sustain industrial capabilities and lower theoverall projects risks. At the same time, existing reactors have also observed steady improvements
in relation to their safety and reliability levels, despite ageing, which can be explained not only by
the replacement of components but also by increasing technical progress and operating
experience, combined with governing frameworks that foster continuous improvements.
Obsolescence of structures, systems and components (SSCs) and supply chain issues, however,are an emerging concern, resulting largely from increasing policy risks, degraded market
perspectives and high qualification needs. An increased used of commercial grade dedication forsafety-related SSCs and the harmonisation of nuclear codes and standards (including theacceptance of alternative codes and standards in national regulations) are effective in mitigatingsuch supply chain risks. Recent national examples have also demonstrated that regulators andoperators can work co-operatively to reinforce the network of qualified suppliers. In parallel,
problems related to attracting and retaining the best talent have also become pronounced. In lightof such trends, and with nuclear power plants operating for longer periods, the ability of utilities
to sustain operational excellence and economic performance during LTO could be undermined.
Nuclear policies and international co-operation will be key in mitigating such risks.

Key policy recommendations [III]5.

Sustain supply chain capabilities and nuclear expertise at all levels: By committing to LTO, countries will
directly sustain existing supply chain capabilities and send clear signals to younger generations to renew thenuclear workforce. These actions should be complemented by joint undertakings with regulators, industry
and academia to foster nuclear expertise at all levels. Ongoing international collaboration can also play a rolein preserving knowledge and developing human capital in the nuclear sector.

6.

Build long-term and predictable industrial plans: High fixed cost technologies such as nuclear power
require policy certainty. Coping with policy risks is sometimes possible, but with a significant cost penalty.
Through nuclear industrial strategies, governments can provide the long-term, stable framework necessary
to plan and optimise licence extensions.

Recognising the full value of the LTO option in decarbonisation strategies
Sustainable electricity infrastructures require policy frameworks that simultaneously addresseach pillar of the “energy trilemma”: i) environmental protection; ii) economics and affordability;
and iii) electricity security and reliability of electricity supply. Nuclear power, and in particular
LTO, perform well in each of these three dimensions.
From an environmental perspective, licence extensions allow countries to secure carbon
emission reduction trajectories at competitive costs. The affordability of LTO is also confirmed at
the system level, where the availability of dispatchable generation, thanks to extended operations,will facilitate the integration of higher shares of variable renewable energy (VRE) at lower systemcosts. Dispatchability could also reduce the potential security of supply and reliability risks arisingfrom the simultaneous retirement of large amounts of fossil-fired capacity, necessary to beconsistent with 2015 Paris Agreement engagements. In interconnected systems, such as those inOECD countries, such positive effects could be noticeable across regions.
Longer operating periods will also bring additional value to policymakers beyond the energy
trilemma. The additional time unlocked through LTO can be used to secure additional funding
and the infrastructure needs for back-end activities, optimise investment and industrial plansand develop new technologies. The resulting, enlarged technology portfolio, combined with the

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

149

CONCLUSIONS AND POLICY RECOMMENDATIONS: ENABLING LONG-TERM OPERATION

relatively immediate effects of LTO decisions, adds more flexibility in the energy planning sothat unexpected risks can be absorbed without jeopardising decarbonisation strategies.
Lastly, supporting LTO will require market regulations that adequately price all theaforementioned attributes and provide revenue certainty in the long term. The experience
gained by governments in developing support mechanisms for low-carbon technologies could
be used to develop policy packages for LTO in an effort to serve current decarbonisation
pathways. Structural market reforms that will foster low-carbon investment and ensure longterm system adequacy will also benefit licence extensions.

Key policy recommendations [IV]7.

150

Reform market regulations to ensure that the system value of long-term operation adequately
remunerated: In many regions, different types of regulations and mechanisms are used to overcome
market challenges and support low-carbon technologies. These regulations and mechanisms can beextended to LTO in order to adequately remunerate the value that they provide to the system in terms ofemission avoidance, but also in terms of system adequacy and grid reliability. Other options such as thereview of nuclear taxation regimes can be envisaged as well.

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

APPENDIX 1: LIST OF EXPERTS

Appendix 1: List of experts

This study was written by Antonio Vaya Soler from the Nuclear Energy Agency (NEA) Divisionof Nuclear Technology Development and Economics, based on evidence collected from thedifferent references cited in the report, as well as the insights and specific inputs provided by
the NEA Expert Group on Maintaining Low-Carbon Generation Capacity through LTO of Nuclear
Power Plants: Economic, Technical and Policy Aspects (EGLTO) and other experts. EGLTO
members, along with the NEA Working Party on Nuclear Energy Economics (WPNE), supervised
the study at all stages and recognised its results. Additionally, the NEA Secretariat conductedindividual interviews with senior nuclear industry professionals to collect insights from theindustry on selected topics. A list of the different experts that formally participated in the study
is provided below.

Members of the EGLTO expert group:
Country representatives
Mr Ricardo Sainz
Mr Arnaud Meert
Mr Jeff Lehman
Mr Paul Smeekes
Mr Myriam Colacicco
Dr Nobuyuki Ueda
Dr Masao Chaki
Mr Adrian Gabriel Dumitriu
Mr Eduardo Serra Sintes
Mr Jan-Erik Lindback
Mr Steffen Asser
Mr Bruce Hallbert

Argentina
Belgium
CanadaFinlandFranceJapan
Japan
Romania
Spain
SwedenSwitzerland
United States

Representatives of international organisations
Ms Sherry Bernhoft
Dr Aliki I. Van Heek

EPRI
IAEA

Observers and other experts
Mr Koji Nagano
Mr Paul-Etienne Pini
Mr Oliver Martin
Mr Pablo Luna
Mr Gustavo Diaz
Mr Matt Crozat
Mr Alexey Lohkov
Mr Tim Freeman
Mr Jean-Philippe Mathieu

CRIEPI
IAEA
JRC
NASA
NASA
NEI
Rosatom
SNC Lavalin
EDF

LONG-TERM OPERATION OF NUCLEAR POWER PLANTS AND DECARBONISATION STRATEGIES, NEA No. 7524, © OECD 2021

151

NEA PUBLICATIONS AND INFORMATION

The full catalogue of publications is available online at www.oecd-nea.org/pub.
In addition to basic information on the Agency and its work programme, the NEA website
offers free downloads of hundreds of technical and policy-oriented reports. The professional
journal of the Agency, NEA News – featuring articles on the latest nuclear energy issues – isavailable online at www.oecd-nea.org/nea-news.
An NEA monthly electronic bulletin is distributed free of charge to subscribers, providing
updates of new results, events and publications. Sign up at www.oecdnea.org/bulletin.
Visit us on LinkedIn at www.linkedin.com/company/oecd-nuclear-energy-agency or follow
us on Twitter @OECD_NEA.

OECD/NEA PUBLISHING, 2 rue André-Pascal, 75775 PARIS CEDEX 16

Long-Term Operation of Nuclear Power
Plants and Decarbonisation Strategies

The existing nuclear fleet remains the largest low-carbon source of electricity generation in OECD
countries. In 2021 the average nuclear power plant had already been operating for 31 years and some
30% of reactors worldwide were already operating under long-term operation conditions. The long-term
operation of this existing nuclear capacity will be essential over the next decade to keep decarbonisation
targets within reach. At the same time, by keeping the long-term-operation option open, countries could
also reap a wide-range of socio-economic benefits including more affordable and secure electricity
supply. Nevertheless, an increasing number of reactors are being shut down earlier than expected due topolicy decisions and increasing market pressures in some regions.
In light of these trends, this study takes a holistic approach to identifying the key enablers for long-term
operation of nuclear power plants. The attractiveness of long-term operation lies in its technical maturity,
cost-competiveness and ease of implementation: it is a high-value option to support the energy transition
while minimising potential risks along the way.

Nuclear Energy Agency (NEA)
46, quai Alphonse Le Gallo
92100 Boulogne-Billancourt, France
Tel.: +33 (0)1 73 21 28 19
nea@oecd-nea.org www.oecd-nea.org

NEA No. 7524