Nuclear Safety
NEA/CSNI/R(2018)8
November 2018www.oecd-nea.org

Cable Ageing in Nuclear Power
PlantsReport on the First andSecond Terms (2012-2017)of the NEA Cable Ageing
Data and Knowledge (CADAK)
Project

Nuclear Energy Agency

NEA/CSNI/R(2018)8
Unclassified

English text only
6 December 2018

NUCLEAR ENERGY AGENCYCOMMITTEE ON THE SAFETY OF NUCLEAR INSTALLATIONS

Cable Ageing in Nuclear Power Plants
Report on the first and second terms (2012-2017) of the NEA Cable Ageing Data
and Knowledge (CADAK) Project

Please note that this document is available in PDF format only.

JT03441022

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.

2 │ NEA/CSNI/R(2018)8
ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENTThe OECD is a unique forum where the governments of 36 democracies work together to address the economic,
social and environmental challenges of globalisation. The OECD is also at the forefront of efforts to understand andto help governments respond to new developments and concerns, such as corporate governance, the information
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domestic and international policies.
The OECD member countries are: Australia, Austria, Belgium, Canada, Chile, 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, the Slovak Republic,
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NUCLEAR ENERGY AGENCYThe OECD Nuclear Energy Agency (NEA) was established on 1 February 1958. Current NEA membership consistsof 33 countries: Argentina, Australia, Austria, Belgium, 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 also takes 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, thescientific, technological and legal bases required for a safe, environmentally sound and economical use of
nuclear energy for peaceful purposes;– to provide authoritative assessments and to forge common understandings on key issues as input togovernment decisions on nuclear energy policy and to broader OECD analyses in areas such as energy andthe 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 technical analysesof 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.
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COMMITTEE ON THE SAFETY OF NUCLEAR INSTALLATIONSThe Committee on the Safety of Nuclear Installations (CSNI) is responsible for the Nuclear Energy
Agency (NEA) programmes and activities that support maintaining and advancing the scientific andtechnical knowledge base of the safety of nuclear installations.
The Committee constitutes a forum for the exchange of technical information and for collaboration
between organisations, which can contribute, from their respective backgrounds in research, development
and engineering, to its activities. It has regard to the exchange of information between member countries
and safety R&D programmes of various sizes in order to keep all member countries involved in andabreast of developments in technical safety matters.
The Committee reviews the state of knowledge on important topics of nuclear safety science andtechniques and of safety assessments, and ensures that operating experience is appropriately accounted
for in its activities. It initiates and conducts programmes identified by these reviews and assessments inorder to confirm safety, overcome discrepancies, develop improvements and reach consensus ontechnical issues of common interest. It promotes the co-ordination of work in different member countries
that serve to maintain and enhance competence in nuclear safety matters, including the establishment ofjoint undertakings (e.g. joint research and data projects), and assists in the feedback of the results toparticipating organisations. The Committee ensures that valuable end-products of the technical reviews
and analyses are provided to members in a timely manner, and made publicly available whenappropriate, to support broader nuclear safety.
The Committee focuses primarily on the safety aspects of existing power reactors, other nuclear
installations and new power reactors; it also considers the safety implications of scientific and technicaldevelopments of future reactor technologies and designs. Further, the scope for the Committee includes
human and organisational research activities and technical developments that affect nuclear safety.

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Table of contents

Executive summary ............................................................................................................................... 5
List of abbreviations and acronyms ..................................................................................................... 8
1. Introduction ..................................................................................................................................10
1.1. Background ..............................................................................................................................10
1.2. Objective ..................................................................................................................................10
1.3. Project organisation .................................................................................................................11
1.4. Scope .......................................................................................................................................12
2. Database overview ........................................................................................................................132.1. Introduction .............................................................................................................................132.2. Intended use .............................................................................................................................142.3. Database and knowledge base development ............................................................................142.4. Database search capability .......................................................................................................142.5. New features during CADAK term one ..................................................................................16
2.6. Planned extension of the database structure and migration to a new software
platform during term two ........................................................................................................17
3. Environmental condition monitoring .........................................................................................19
4. Condition indicators .....................................................................................................................21
5. Ageing of cables ............................................................................................................................24
6. Ageing of cable penetrations ........................................................................................................26
7. Research and experimental focus areas of member countries..................................................27
7.1. Introduction .............................................................................................................................27
7.2. Canada .....................................................................................................................................27
7.3. France ......................................................................................................................................28
7.4. Japan ........................................................................................................................................30
7.5. Slovak Republic ......................................................................................................................30
7.6. Spain ........................................................................................................................................31
7.7. Switzerland ..............................................................................................................................33
7.8. United States ............................................................................................................................35
7.9. The International Generic Ageing Lessons Learned (IGALL) for Nuclear Power Plants. ......36
8. Actions in CADAK .......................................................................................................................38
8.1. Principal steps ..........................................................................................................................38
8.2. Assessment of cable material of the decommissioned nuclear power plants ..........................38
8.3. Ensuring the long-term operation ............................................................................................39
8.4. Forms of test data.....................................................................................................................40
8.5. Recent tests in Canada .............................................................................................................40
9. Cable data analysis .......................................................................................................................46
10. Conclusions and recommendations .............................................................................................47
11. References......................................................................................................................................49
12. Appendix 1 CADAK Database and knowledge base .................................................................50

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Executive summary
The NEA Cable Ageing Data and Knowledge (CADAK) Project is the continuation of thecable ageing part of the NEA Stress Corrosion Cracking and Cable Ageing Project(SCAP). In 2012, eight NEA member countries – Belgium, Canada, France, Japan, theSlovak Republic, Spain, Switzerland and the United States – joined the CADAK Project
to pool their knowledge into a common database.
The CADAK Project aims to establish the technical basis for assessing the qualified lifeof electrical cables in light of the uncertainties identified following the initial (early)
qualification testing. This research will investigate the adequacy of the margins and theirability to address the uncertainties. The project was financed through contributions fromeach participating NEA member country. The first term work concentrated on continuing
the construction of the database for data gathering and defining the methods for national
co-ordinators supplying data and documents presenting the results of the ongoing
research and test programmes.
The database facilitates data entry as well as database interrogation. The knowledge baseallows for capturing, sharing, transferring, storing and utilising technical information on
cable degradation mechanisms, relevant R&D results, and national codes and standards
for design and construction and in-service inspection. The CADAK database includes
over 1 300 records divided among those ten parts forming the database structure. The
knowledge base includes almost 275 country specific collections of documents in ten
different areas.
For the second term, the analysis of cable data was one of the CADAK Project goals;
however, there are large variations of cable types and insulation materials in the databaseand differences in plant level application related to the use of cables. A large part of
CADAK data originates from the SCAP project and another large part of the data wasprovided from countries that no longer participated in CADAK during phase two. The
participating countries were Canada, Germany, the Slovak Republic, Switzerland and theUnited States. The mentioned variation in cables and detailed level differences in cableuse include: plant designs, local environmental conditions between units with the same
design type and series, supplying procedures, use of materials and manufacturingmethods and storage times. These have a remarkable influence on the lifetime of cables.
The completion of data collection actions for all the cable types in the database was notpossible with the remaining countries in the project. Based on all these variations anduncertainties of existing cable data it was recognised that the amount of work andresources needed for the comprehensive analysis was so large that such an analysis forthe cable data in CADAK database was not possible during phase two.
As an overall conclusion of the project, it is foreseen that demonstrating adequate cable
performance and ageing management in normal operation and post-accident services for a
lifetime over 60 years, or even more, will be a challenge. It appears that the approval of alifetime over 60 years or longer needs new representative test results and cable material

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research as well as more operational experience analysis for recognising the criticalsubjects and targets for additional inspections, assessments and preventive maintenance.
The following recommendations are defined for the future work in the field of cableageing:•••In future, the key objectives of work with cable ageing will be to encourage allcountries to support the multilateral exchange of recent research data andoperating experience of cables. If additional experimental studies allow theidentification of ageing phenomena (generic issues) or improvement of associatedkinetics and influence criteria, it should be published.
It is recommended that all international working parties in the field of cableageing exchange information with other international organisations (e.g. IAEA) toprevent duplication of research efforts. It is also recommended to arrange acommon NEA/IAEA workshop in a the coming years, when the ongoing cableresearch activities of NEA member countries are completed.
The information obtained from the decommissioned nuclear power plants (NPPs)
should be used to verify, validate and/or confirm the assumptions used in thecurrent qualification for cables that are important to safety. Projects to collectcable samples removed from decommissioned NPPs should be used to verify
whether these cables are qualified for additional qualified life beyond 40 years
and beyond 60 years, or even more. The usefulness and representativeness ofcable samples of the decommissioned NPPs could be a good topic for future
research or discussion in international decommissioning programmes.

This project report describes the final status of the CADAK database after SCAP workand the first and second term (2012-2017) of the Cable Ageing Data and Knowledge(CADAK) Project.

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Definitions

CADAK Database

Database + knowledge base

Database

Cable-specific information database

Knowledge Base

Database with the collection of international and country specificdocuments on cables

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List of abbreviations and acronyms

AECL

Atomic Energy of Canada Limited

AM

Ageing management

AMR

Ageing management review

AMP

Ageing management programme

BIS

Broadband impedance spectroscopy

BWR

Boiling water reactor

CADAK

Cable ageing data and knowledge

CI

Condition indicators

CODAP

Component Operational Experience Degradation and Ageing Programme
(NEA)

CNSC

Canadian Nuclear Safety Commission

CM

Condition monitoring

CSN

Consejo de Seguridad Nuclear (Spain)

CSNI

Committee on the Safety of Nuclear Installations (NEA)

CSPE

Chlorosulfonated polyethylene

DBA

Design-basis accident

DMA

Dynamic mechanical analysis

EAB

Elongation at break

EBP

Extra-budgetary programme

EDF

Electricité de France

EPDM

Ethylene propylene diene monomer

EPR

Ethylene propylene rubber

EPRI

Electric Power Research Institute (United States)

ETFE

Ethylene tetrafluoroethylene

EQ

Environmental qualification

EVA

Ethylene vinyl acetate

FTIR

Fourier-transform infrared (spectroscopy)

HFFR

Halogen-free flame retardant

IAEA

International Atomic Energy Agency

IFE

Institute for Energy Technology (Belgium)

LIRA

Line impedance resonance analysis

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LOCA

Loss-of-coolant accident

LV

Low voltage

MSLB

Main steam line breakMV

Medium voltage

NEA

Nuclear Energy Agency

NIR

Near infrared reflectance

NMR

Nuclear magnetic resonance

NPD

Nuclear power demonstration station

NPPs

Nuclear power plants

OIT

Oxidation induction time

OITM

Oxidation induction time method

OITP

Oxidation induction temperature

OPDE

Piping failure data exchange

PE

Polyethylene

PRG

Project review group

PSI

Paul Scherrer Institute (Switzerland)

PSR

Periodic safety review

PVC

Polyvinyl chloride

PWR

Pressurised water reactor

SBR

Styrene butadiene rubber

SCAP

Stress Corrosion Cracking and Cable Ageing Project (NEA)

SCC

Stress corrosion cracking

SIR

Silicone rubber

TDRTime domain reflectometry

TGA

Thermogravimetric analysis

TLAA

Time limited ageing analysis

USNRC

United States Nuclear Regulatory Commission

WGIAGE

Working Group on Integrity and Ageing of Components and Structures
(NEA)

TS

Tensile strength

XLPE

Cross-linked polyethylene

XLPO

Cross-linked polyolefin

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1. Introduction
1.1. BackgroundThe number of ageing nuclear power plants (NPPs) is increasing in NEA member
countries. Accordingly, maintenance programmes, in-service inspection and testing ofstructures, systems and components important to safety have been implemented to ensurethat levels of reliability and effectiveness remain in accordance with the design
assumptions. This is often being done using an integrated ageing management strategy
based on state-of-the-art technology.
Ageing effects, especially material degradation, have progressively been experienced
worldwide since the start of nuclear power plant operation. Material degradation is
expected to continue as plants age and operating licences are extended. It is clear thatunanticipated and unmanaged structural degradation could result in significant loss ofsafety margins, undermining public confidence and straining the resources of both
regulatory authorities and the operators.
For regulatory authorities, it is important to verify the adequacy of the ageing
management methods applied by the licensees, based on reliable technical evidence.
Degradation of cable insulation were selected as one of the focus areas of the of SCAP
project (2006-2010) due to its implications for nuclear safety and its relevance for plant
ageing assessment.
In December 2010, the CSNI agreed to support two SCAP follow-up activities, that being
the convening of an experts meeting on the cable ageing database and secondly, theconvening of an experts meeting on the merging of the SCC and OPDE database projects
to become the CODAP (Component Operational Experience, Degradation and Ageing
Programme) project. The CADAK Project followed the cable ageing part of the NEA
SCAP Project.
In 2012, eight NEA member countries joined the CADAK Project to pool theirknowledge into a common database. The project was financed through economical
contributions from each participating member country to NEA. The objectives of the
CADAK Project are to establish the technical basis for assessing the qualified life ofelectrical cables in light of the uncertainties identified following the initial (early)
qualification testing. This research will investigate the adequacy of the margins and theirability to address the uncertainties.
This report summarises the project results of the CADAK database project during the two
three-year terms: First term: 2012 to 2014 and second term: 2015 to 2017.

1.2. Objective
The general objective of this internationally co-ordinated project is to share the corporate
knowledge, operation and research experience so as to better understand the degradation
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mechanisms and identify effective techniques and technologies to manage and mitigate
active cable degradation in NPPs. This helps regulators and operators to enhance ageing
management.
Technical objectives of the CADAK database project are as follows (Terms andConditions for Project Operation – 2011-2014):a) to establish the technical basis for assessing the qualified life of electrical cables
in light of the uncertainties identified following the initial (early) qualification
testing. This research will investigate the adequacy of the margins and theirability to address the uncertainties.
b) to edit for a number of member countries cable data and information into thesystem e.g. technical standards being applied in the qualification of cables andinspection methods being used regularly.
c) to estimate the remaining qualified lifetime of cables used in NPPs. The cable
Condition-Monitoring Techniques shared by the participants within CADAK will
become an up-to-date encyclopaedic source to monitor and predict theperformance of numerous unique applications of cables.
d) to analyse the information collected to develop topical reports in co-ordination
with the NEA CSNI Integrity and Ageing of Components and Structures Working
Group (WGIAGE).
The technical objectives were written to be followed in the long-term work with CADAK
database. In years 2012-2014 during the first term CADAK the focus of the CADAK
project was in developing the database and knowledge base structure for effective datacollection from the surveillance and test programmes as well as the ongoing research
activities in member countries.
During the second term in years 2015 -2017 the CADAK project was continuing the workwith same objectives. An additional goal during for CADAK term two was to collectinformation on ageing effects of the electrical penetrations into the CADAK database;however, the goal was not achieved.

1.3. Project organisation
The project participants are experts in the fields of cable ageing and come from
regulators, industry and research institutions. They provide the relevant information andperform the assessments needed for the proper execution of the programme.
The NEA Project Secretariat runs the project with assistance from the operating agent.
The Project Review Group (PRG) is responsible for carrying out the program of work, in
co-operation with NEA and the operating agent, and ensuring the quality and timelinessof the reporting within and outside the project.
The Operating Agent work to ensure the consistency of the data contributed by theparticipating countries. They verify whether the information provided complies with the
CADAK Coding Guidelines. They also verify the completeness and accuracy of the data,
and maintain and distribute copies of the database and knowledge base.

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Participation in the project is open to the government of any country, whether or not they
are a member of the OECD, or to any national agency, public or private organisation
designated by such government provided the government agrees with the terms ofreference which were specified during the initial meeting. Each member country
nominates a national representative for the PRG who is responsible for the administrationof the project within his/her respective country.
Each participating country has submitted data and documents through its national
representative. The data has been entered according to a specified format which was
specifically developed for the data- and knowledge base and which is explained in the
Coding Guidelines and the Quality Assurance Program for the PRG. The cable databaseand knowledge base are password protected, and the contents and data analysis results are
distributed only among active working group members under the project terms ofreference.

1.4. Scope
The scope of this project involves the continued development and population of thedatabase and knowledge base that address common elements in the management ofageing and mitigation of failures for cables: study of ageing effects, investigation of
failure mechanisms, mitigation of influencing factors, prediction of conditions for
replacement, safety assessment of cables, environmental qualification (EQ) andcondition-monitoring methodology and its validation.
The second term of CADAK has same general goals than in first term; however, theadditional goal to provide ageing effects of the electrical penetrations into the CADAK
database was not reached during second term.

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2. Database overview
2.1. Introduction
The database and the knowledge base work in CADAK is a continuation of the work thatwas performed under the NEA SCAP project (2006-2010), and builds on the samephilosophy, principle structure and populated data. Both the database and knowledge baseare organised in ten main parts to document all the details of the cable including design,qualification, maintenance, condition-monitoring and continuing research. The principle
structure and the parts are shown in Figure 2.1.
Figure 2.1. The principle structure of CADAK Database and knowledge basePart 1:
Technical data of cable

Part 2.2:
Cable sampling (including
cable deposit)

Part 2.3:
Cable repairing

Part 3:
Data for the cable failure
eventsPart 6:
Mitigation of cableinstalled environment

Country

Part 2.1:
Cable inspection / condition
monitoring methods in-service
Part 4:
Cable environmental
qualification code data
Part 5:
Plant and cable environmental
condition
Part 8:Regulatory information forcable / continued confirmatory
and exploratory researchPart 9:Cable condition monitoring/in-service and underdevelopment

Part 7:
Cable replacement

Part 10:
Technical references on
ageing mechanisms

Cable-related data

Country-related data

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14 │ NEA/CSNI/R(2018)82.2. Intended use
All information in the database and knowledge base of CADAK is made available for all
CADAK members through a dedicated web-interface, and without any restrictions or
imposed guidelines.

2.3. Database and knowledge base development
2.3.1. Database development
The database is organised as a relational database, originally operating on MySQL
software, and was built from data collected by the different member country participants.
Database entries are managed through dedicated web entry sheets, originally handled
through zope application server and plone content management system. In 2017, theprocess of migrating CADAK application software to modern database- and webtechnology software was initiated (ref. Section 2.6.2). During the CADAK project,population of the database has continued, and there has also been made changes to thedetailed item structure for Part one – Technical data of cable. In addition, the CADAK
term two member countries discussed the possibility to add more ageing-components tothe database, and the design of a new main part related to cable penetration was initiated(ref. Section 2.6.1). It has also been put greater focus on the knowledge base during thisperiod. When the CADAK project is being completed, the database includes
1 338 records divided among those 10 main parts forming the CADAK databasestructure.

2.3.2. Knowledge base development
The knowledge base consists of a collection of document files, and was built from datacollected by member participants. The former SCAP Cable Working Group evaluated theinformation in the database and identified subject areas that were of great significanceand would be of great use to current nuclear operators and regulators, and classified themas the knowledge base. The assessment began with the identification of the essential
elements to be in the knowledge base. The former SCAP Cable Working Group examined
and reviewed the data collected in the database and extracted information, leading to acertain number of conclusions. During CADAK, participating member organisations havecontinued to populate the knowledge base. In addition, all document files provided asattachments to database records have been transferred to the knowledge base, leading to
275 separate document files in the knowledge base. These document files are accessible
through the CADAK knowledge base web-interface.

2.4. Database search capability
The cable database search tool allows fast access to desired information in any part of thedatabase. The search tool opens up for multi-part/multi-country searches, withpossibilities for tailor-made search and display criteria. Figure 2.2 shows the entry point
for the search tool, with panels for choosing main search criteria as parts, countries andsearch strings.

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Figure 2.2. Entry point for database search tool

A dedicated search/display filtering panel for each part opens up for search and result
display filtering. See Figure 2.3 for an example from “Part eight: Regulatory information
for cable/Continued confirmatory and exploratory research”.
Figure 2.3. Detailed search/display filtering panel

An example of a database search result in Part 8 – Regulatory information forcable/Continued confirmatory and exploratory research is shown in Figure 2.4. The
search outcome shows e.g. applicable cable regulations, organisation and contact namefor the regulator. Detailed record information, based on the search results and member
access rights, is made available through dedicated pushbuttons.

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16 │ NEA/CSNI/R(2018)8
Figure 2.4. An example of a search result from Part eight – Regulatory information
for cable/Continued confirmatory and exploratory

2.5. New features during CADAK term one
The new features added into the original database (based on SCAP project work [2]) arelisted in this chapter and covers the following areas:•••

Structure of the technical part of the database
Knowledge base partWeb-interface

2.5.1. Structure of the database••

Part one – Technical data of cable: Items «insulation material» and «otherinsulation material» have been made mandatory.
Continued population of the database.

2.5.2. Knowledge Base••

All attachments in CADAK database have been copied to the corresponding
sections in knowledge base.
Extended population of the knowledge base.

2.5.3. Web-interface•

Extended menu field by introducing top-level information folders:•– Actions– Database– Knowledge base– Meetings– National activities– Related links– Reports– Standards– Upcoming events
Introduced CADAK Attention and Contacts fields
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NEA/CSNI/R(2018)82.6. Planned extension of the database structure and migration to a new software
platform during term two
2.6.1. Structure extension – Cable penetration
The CADAK term two member countries discussed the possibilities to introduce possible
ageing effects of the electrical penetrations into CADAK database, knowledge base andweb-interface. Possibilities to introduce even more qualified components into the
database, knowledge base and web-interface were also discussed, but the CADAK PRG
decided to postpone these plans.
The structure building of a new main part eleven – Cable Penetration was therefore
initiated, consisting of the two sub-parts:••

11.1 – General information/Generic data from supplier11.2 – Technical specification data.

However, the final implementation of part eleven – Cable Penetration was not completed
as the CADAK project was terminated by the end of 2017.

2.6.2. Migration to a new software platform
Development of the NEA CADAK database & knowledge base application was started in2006 as part of the Stress Corrosion Cracking and Cable Ageing Project (SCAP). It was
built on a software platform consisting of a Debian Linux v6.0 operating system, Zope
Application Server v2.0 and Plone Content Management System v3.02.
The CADAK application itself and the underlying software tools were tailor-made for its
purpose. Structural differences in newer software versions made upgrades difficult andthus making the system versions deprecated. This caused limitation and put constraints
and reduced flexibility when it comes to managing records and documents in the databaseand knowledge base. The limitations made it difficult to scale data quantities, increase
number of users, introduce new and user friendly functionality and to provide respectable
response times.
The deprecated system also caused a considerable security risk, and was vulnerable tocyber-attacks. This vulnerability brought a lot of attention to the operating agent’s digital
infrastructure, and violated digital security. It was therefore not desirable for theoperating agent to continue these software modules. An upgrade to newer versions would
have had to incur a restructuring and rewriting of the existing application, which would
have been both time and cost consuming and still remain old and unsecure technology.
As a consequence the operating agent planned to stop using the zope/plone technology for
its web-applications, and started a process of restructuring its digital infrastructure, based
on today's and future challenges. Cyber threats and cyber security were keywords, andOA were about to change business model for dealing with web technology. To be in linewith the operating agent’s new digital policy, and up to date on software- anddevelopment tools, this caused a need to migrate the CADAK application to a new andmodern platform. This could be achieved by adopting modern software and development
tools like:a) Microsoft Visual Studio Community 2015b) Microsoft SQL Server (MSSQL Express)c) Microsoft.NET Framework

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18 │ NEA/CSNI/R(2018)8d) ASP.NETe) Microsoft MVC 5 Entity Framework.
During 2017, the development of a migrated CADAK system application was initiated,with high degree of modularity, meeting today’s security requirements and opens up the
possibility for future extensions like e.g. improved analysing methods, big-data, data
import/export. However, the implementation phase was never reached as the CADAK
project was terminated by the end of 2017. Nevertheless, a simplified system (readaccess) will be provided to allow CADAK member countries to access database andknowledge base in an offline post-CADAK-phase.
Figure 2.5 shows the conceptual models for the old deprecated zope/plone based
configuration, and the planned new modular configuration based on modern
software- and development tools.
Figure 2.5. Old and new conceptual models for the migrated software platform

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3. Environmental condition monitoring

In the nuclear field, where cables related to the safety of the plant are qualified before
installation for the expected life (e.g. 40 years) the effect of the particular adverse
environment conditions (high radiation, humidity and temperature), especially during andafter design basis accidents (DBAs), is an important issue for the assessment of thecondition of installed cables.
Main ageing factors (stressors) to be monitored are temperature (including self-heating)and radiation. Other factors to be considered include humidity, electrical fields, corrosive
environment in specific areas and mechanical stresses due for example bending or
vibration.
These factors contribute to the degradation of the mechanical and electrical properties ofcables. Testing methods aim to determine the progress of ageing. Main effort isperformed on insulation regarding the fact it plays a major role in electrical properties ofcables.
Monitoring of environmental conditions in the nuclear power plant that may adversely
affect cable performance can provide valuable insight when determining cable life. It isstrongly needed to determine equipment which is submitted to the highest stress.
Performing tests on these cables permits to have valuable information on theirdegradation and to gain in confidence concerning the degradation of other cables. Outer
sheath plays generally the role of mechanical protection and limit the exposure of
insulation e.g. corrosive fluids or mineral oils.
The significant stressors in normal operation are the following:••••

Temperature including temperature increase due to self-heating (resistive effect)
Radiation
High humidity or submergence conditions (in specific areas)
Mechanical constraints

In some high voltage cables, electrical fields may accelerate ageing mechanism inpresence of other stressors (for example humidity).
Operating feedback is needed to improve the quality of environmental condition
monitoring.
A lot of countries monitor environmental conditions in containment and in some specificareas outside of containment. A synthesis of measurements done in Japanese units(in containment) updated in 2014 is presented in Table 3.1 below.

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Table 3.1: Summary of plant environmental condition for Japanese nuclear power plants(Additional date to table 3.3.5-2 of NEA/CSNI/R(2010)15 – Reference [2]Temperature

Dose rate

Number of

Maximum

measurement

temperature

Number of

Maximum

measurement

pointsdose rate(℃)

points(Gy/h)

BWR, BWR-5

140(163)

52.5

159

0.404

BWR, BWR-5

94(94)

69

95

0.086

BWR, BWR-5

157(167)

70.4

167

0.087

BWR, BWR-528(75)

60.4

78

0.453

BWR, BWR-5

223(100)

71.9

100

0.1206

158(47)59.8

870.2516

92

0.144

Plant

Tool

BWR, BWR-5
BWR, ABWR

Data loggers
and labels forthermometry

Tool

Alaninedosimeters

88(14)

62.5

BWR, ABWR

93(82)

52.7

98

0.1056

BWR, ABWR

103(74)

57.6

106

0.092

PWR, 2-loop

29(33)

57.9

22

0.255

PWR, 3-loop

36(17)

59.3

36

0.341

PWR, 4-loop

34(25)

46.3

24

0.068

PWR, 4-loop

40(54)

44.1

60

0.271

For PWR, maximum temperature is generally expected for power cables of motor
operated valves located on or nearby primary circuit (e.g. hot loop and pressuriser areas).
Maximum dose rate is around 0.2 Gy/h, except in area near the reactor pressure vessel.
For boiling water reactor (BWR) maximum temperatures and dose rates are usuallysomewhat higher based on smaller size of containment. There are somewhat variations
with maximum levels of temperature and radiation during power operation, depending onplant design features related to air conditioning and radiation protection structures insideof containment.

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4. Condition indicators
Following IAEA Nuclear Energy Series No: NP-T-3.6 [6] the condition indicator(s) will
be used to track the ageing of the cables and to determine if aged cable is still able tooperate under accident conditions. An important characteristic of a useful conditionindicator is that it demonstrates a trend that changes monotonically with degradation andcan be correlated with the safety-related performance in-service conditions (including
accident conditions). For example, the parameters used as condition indicators could
monitor the change in the chemistry of the material (e.g. polymer chain degradation, side
reactions), monitor the mechanical properties (e.g. tensile elongation, hardness,
compressive modulus), or monitor electrical properties of the material (e.g. dielectric
properties or reflectometry properties). A large number of methods are available, but thecondition indicators should be sensitive to the effects of ageing for the particular materialand correlation between this degradation state and ability of aged cable to operatecorrectly in different service conditions (including accident conditions for which it shallbe qualified).
For effective cable ageing management, it is important to identify cable information
including cable type, material, critical parts which may be influenced by ageing stressors,
ageing mechanism and its potential effects. Cable condition-monitoring method isdetermined based on the before mentioned information. Test and inspection frequencies
are defined based on operating experience, on safety relevance of cable and on the trendof the selected indicators.
Different methods exist to perform condition monitoring of cables, e.g. visual inspections,
indenter, time domain reflectometry (TDR), insulation resistance measurement, voltage
test, elongation at break (EAB), Fourier-transform infrared (FTIR), near infrared
reflectance (NIR), oxidation induction time (OIT) test, tan δ, etc.
Acceptance criteria are material dependent: e.g. a cable match by EAB, a level of morethan 50%, voltage tests requirements fulfilled, TDR should be in the acceptable range,
etc. Acceptance criteria should be, when possible, defined regarding characteristic ofcables measured during qualification sequence just before accident test (e.g. just after
ageing sequence).
The acceptance criteria for determining the end of residual life time of installed EQ
cables are plant specific. The acceptance criteria should ensure that cables are able tosuccessfully perform their safety-related demands during accident condition at the ageing
level determined by the selected condition-monitoring techniques.
Condition monitoring can be done on cable samples that have been subject torepresentative operating conditions stressors. Measurement should be done on samples
which are the most stressed what permits to interpolate the result for less stressed cables.
Additional cable samples can be deposited to limit the use of operating cables see
Figure 4.1.

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Figure 4.1. Cable samples of Beznau NPPFigure 4.2. Cable ageing during test periods (principle curve)

ε0 = level at the beginning of ageing (new cable) - Tensile test of samples every five
years (all two years if significant changes)
Figure 4.2 presents an example for defining the intervals and criteria for the tensile tests
on cables. The interval for the tensile test of cable samples is every five years. If thetensile test results decrease under the original tensile requirement for similar new cable
the test interval is two years. In this example the accepetance criteria in the tensile tests
for cables with original qualification is 50% of the original requirements.
Examples of ageing management tables for Coax/Triax and low-voltage power cables areshown in Table 4.1 and Table 4.2 below.

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Table 4.1.: Examples of ageing management table for coaxial and triaxial cables
used inside the containment vessel of Beznau nuclear power plant

Table 4.2. : Example of ageing management table for low-voltage cables
used in the containment vessel of Beznau NPP

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5. Ageing of cables
In the last 20 years some specific regulatory recommendations have been madeconcerning the pre-ageing of cables for the qualification tests to ensuring the safetymargins of cables under design basis accident conditions. To ensure the scientific andtechnical basis of these recommendations a lot of countries have investigated ageing
effect for cables in last 15 years. Ensuring the safety margins is especially important tothe cables, which have to withstand the harsh environment, especially high thermal andradiation effects during accidents. Recent international research on cable qualification andageing management (e.g. SCAP Project [2], IAEA Nuclear Energy Series, IAEA/NP-T3.6 [6]) has raised an issue about “uncertainties” in the validity of cable EQ programmes
performed in the past.
Experimental programmes have been performed in the last two decades in the U.S.
(SANDIA), Japan (JNES/NRA), France (NPP) that lead to the following main sources ofthese uncertainties:
•
•
•
•
•
•

Synergistic effects in the radiation & thermal ageing test sequence applied
Acceleration factors used in the radiation & thermal ageing tests
Dose rate effects
Oxygen-starved LOCA chambers effects
Non-conservative/incorrect activation energy values, used in Arrhenius equation
Inverse temperature effects (semi-crystalline polymers XLPE, XLPO)

More recently, document SAND 2013-2388 “NPP cable materials: review of qualificationand currently available ageing data for margin assessments in cable performance” [7], hasbeen published. It gives a synthesis of these uncertainties issues.
Based on these experimental programmes the following recommendations can be
expressed:
•
•
•

•

Perform condition monitoring and obtain condition indicators (mechanical,
chemical /Oxidation Induction Temperature/electrical/dielectric strength, Tandelta method) during and at the end of ageing condition test sequence.
Thermal ageing time shall not be reduced too much and temperature shall not be
too high to ensure representativeness of accelerated thermal ageing(>> 100hours).
The dose rate for radiation ageing should be as low as can be accommodated
within reasonable cost and duration of the test noting that several insulationmaterials do not exhibit homogenous degradation when radiation dose rates arehigher than 100Gy/h (10 000 rad/hour).
Regarding the fact that ratio of oxidation is higher for low dose rate, total dose
applied during ageing sequence shall be adapted accordingly.

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•
•

•
•
•
•
•
•

The LOCA-test chamber used in cable qualification tests should provide methods
for continuous supply of oxygen to prevent non-homogeneous degradation in anoxygen-starved environment.
The temperature and dose rate for radiation ageing and for radiation in postaccident phase should be chosen considering that oxidation is a primary ageing
mechanism for most age sensitive equipment and degradation depends on both
thermal stress and radiation.
Humidity shall be taken into account.
Operational ageing (thermal and radiation dose) rates should ensure homogeneous
degradation of the test samples.
Limits for the temperature and dose rate, specifications of the activation energy,
and ageing time should be properly evaluated.
For certain material (polyolefin) inverse temperature effect shall be taken into
account (faster degradation at lower temperature and with a given dose rate for
specific material).
For radiation ageing, it is always better to apply a total dose higher than the dosecorresponding to the expected service life, so as to obtain a margin taking allthese elements into account.
Sequential tests can be less penalising than performing simultaneous thermal andirradiation ageing. In case of using sequential test, the most degrading sequence
shall be chosen.

Currently the nuclear community is concerned about the potential effects of theuncertainties issue on the current qualification status of the cables installed in theoperating NPPs.
This issue could impact the validity of initial qualification programmes. In Europe, it
should be assessed in the frame of periodic safety review (PSR) of the plants (every ten
years) and for the lifetime extension targets.
Regarding uncertainties sources, many countries are recommending initiating
investigation about usable condition indicators to track ageing of insulation. Thesemethods should be used in the following years by choosing properly candidate (and if
possible on an anticipated way) samples coming from operating or dismantled plants.
Main stressors (temperature and irradiation) that cables have experienced during theiroperating life, have to be taken into account in the choice of samples (what needs
monitoring of ambient conditions). In many countries these programmes or researches are
ongoing (Canada, Spain, United States, France). For more details please refer to
Section 7. (R&D).

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6. Ageing of cable penetrations
For an ageing programme it is important, that all relevant components which have ageing
mechanism are monitored. Therefore, in the term two the CADAK team selected thecable penetration as part of the cable data programme. The cable penetrations data in thisreport and in the CADAK is emphasising into the cable penetrations of the primarycontainment, which are most important from ageing point of view.
These penetrations are used for electrical cable access through the containment boundary
and their main purpose is to provide a pathway for electrical links through thecontainment boundary while keeping an effective seal around the cables between bothsides of the containment boundary.
The cable penetration itself has to be tested before installation against temperature
resistance, pressure resistance, dose rate, leakage rate and earthquake resistance. Afterinstallation the leakage rate of penetration is periodically tested. In NPPs using theleakage budget method the total leakage rate of containment is used as approval methodof the measured leakage rates.
For an EQ cable penetration, similar approach is adopted like for EQ cable. For instance,
applicable qualification methods (such as analysis, testing, OPEX or a combination of allof them) should be selected to ensure the cable penetration is environmentally qualified.
If testing is selected, the EQ test programme should be designed to demonstrate that thecable penetration would maintain acceptable performance during its qualified life whensubjected to the normal and accident service conditions. In addition, it should consider anappropriate test sequence.
An ageing programme for cable or electrical penetrations should contain the following
inspection points: visual inspection, corrosion, cracking, isolation resistancemeasurement, material shrinking, embrittlement, etc.
The CADAK phase two contains primary the extension with the necessary fields in the
database. During CADAK phase two the adding of data of electrical penetrations into the
database was started.

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7. Research and experimental focus areas of member countries
7.1. Introduction
Currently, the accelerated-aged cables in the laboratory and assumed the modern
codes/standards are used as the basis for assessing the impacts of ageing on the physicalproperties of cables that are either environmentally qualified for DBAs or already being
re-qualified for life extension. These modern codes/standards are the basis for cablequalification procedures. In order to have a reasonable assurance that age-relateddegradation mechanisms do not significantly affect the long-term safe and reliable
operation of NPPs, the nuclear power industry and the regulators have recommended thedevelopment and implementation of a comprehensive and co-ordinated cable ageing
management programme for all NPPs.

7.2. Canada
In 2012, the Canadian Nuclear Safety Commission (CNSC) has sponsored a research
project, titled “Ageing Management of Cable in Nuclear Generating Stations” [9], which
objective is to provide the background and technical basis supporting regulatory
guidance, consistent with the requirements of CNSC regulatory document, REGDOC2.6.3, “Ageing Management” [3], pertaining to the recommended core elements of acable ageing management programme in Canadian nuclear power plants (NPPs).
Based on this study a number of recommendations were developed for Canadian
regulatory guidance on the basis of the current international guidance and core program
elements established consistent with USNRC regulatory guide RG1.218 [4]. As a result,the following 11 core elements were defined as essential to an effective cable ageing
management programme:
•
•
•
•
•
•
•
•
•
•
•

definition of scope of cable to be addressed by programme;develop and maintain a database of all cables to be monitored;characterise and monitor service environments;
identify stressors and expected ageing mechanisms;
select condition-monitoring techniques suitable to monitored cables;
establish baseline condition of monitored cables;
identify cable characteristics/ageing effects monitored by each CM technique;periodically perform condition-monitoring (CM) tests and inspections on cables;
periodically review and incorporate plant and industry experience;
periodically review, assess, and trend the condition of monitored cables;
identify degraded conditions and define/take corrective actions.

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Consequently, Canadian utilities or reactor operators have implemented cable conditionmonitoring/surveillance/preservation programmes and cable ageing managements toassess, over time, the degradation of cable insulation.
Currently, CNSC has approved a research project, which evaluate properties of cableinsulation materials removed from permanently shut down Gentilly-two nuclear power
plant, by “Analysis of Degradation Mechanisms of Cable Insulation, I&C Equipment due
to Ageing in a Decommissioned Nuclear Power Plant”[5], with the following objectives:
To measure, record and analyse material properties of sample cable insulations from thepermanently shut down nuclear reactor, at Gentilly-two NPP, to assess the degradation
advancement on cables. The project will also include a comparison of the test data
received from the real aged cables versus samples aged in a laboratory following
practices upheld by modern codes and standards. Refer to Section 8.5 for the current
status of this project.
This research is similar to another research project sponsored by CNSC in 1991 on theevaluation of insulation cable materials from nuclear power demonstration (NPD) Station,
except the assumptions utilised as the basis of the existing cable qualification has notbeen covered in the study, since its purpose was to assess degradation of NPD cables andto determine the functional capability of naturally aged and further accelerated-aged cablesamples under LOCA and post-LOCA conditions. With regard to the degradation of NPD
nuclear generating station control and power cables after approximately 25 years ofservice, it was concluded that 1) the degradation of samples from the containment boiler
room was minimal, caused mainly by thermal conditions rather than radiation;2) although irradiation to 550 kGy (55 MRad), simulating normal operation and accident
radiation levels, caused degradation, the cables could still function during accident andpost-accident conditions; and 3)accelerated thermal ageing to simulate an additional ten
years of service at 45 °C caused embrittlement of the PVC and 60% decrease inelongation of the Styrene Butadiene Rubber (SBR).
Furthermore, CNSC plans to participate in work activities with US NRC in a working
group related to harvesting several electrical equipment/components, including cables.
This will also lead to the development of a database for these materials.
The decommissioned NPPs provide an opportunity for the nuclear industry and theregulatory body to verify, validate and/or confirm the assumptions used as the basis ofcurrent qualification for cables. This might later evolve into improvements of the current
qualification approach for cables important to safety within NPPs.

7.3. France
Research programme for new in-containment cables:
The ongoing research programme led by the Institute of Radioprotection and Nuclear
Safety (IRSN) since 2012 is focused on “K1 qualified” cables of last generation, locatedin the containment. The cables of interest are power and I&C cables. The insulation andjacket materials of these halogen-free cables are mainly composed of EVA, EPDM andPE.
The radiolytic and/or thermal degradation of polymers are performed under accelerated
ageing conditions. In the first phase of the programme, the ageing conditions are
representative of the normal operating conditions in nuclear containment environment(50°C, 0.1 Gy.h-1, 70% of Relative Humidity), simulating up to 80 years. An

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experimental design is implemented in order to study the behaviour of polymers
according to different doses (up to 70 kGy) and dose rates (0.2 to 5 kGy.h-1).
The polymers degradation is studied on different types of materials (complete cables,model materials) in order to appreciate the effect of the diffusion of the oxygen in thematerial (distinction in between thermo-oxidation and radio-oxidation). The model
materials based on the same main formulation as the general insulation materials, willallow enhancing the understanding of the ageing mechanisms. A predictive model of theageing of the insulation material will be finally established.
It is important to combine different approaches to characterise the degradation ofpolymers: mechanical tests (elongation at break, micro hardness) providing amacroscopic characterisation and physicochemical methods (OIT, OITP, FTIR, DMA)
allowing assessing the evolutions of the chemical modifications (level of antioxidants,
evolution of the polymers macromolecules structure...).
It has to be justified that degradation of insulation permits to ensure electricalperformances of polymer cables for design basis event and during the first days of asevere accident. Mineral cables are generally used for in-containment instrumentation
channels needed for longer period in case of a severe accident (with core melt).
Condition monitoring of in-containment cables
For 900 MW and 1 300 MW French NPP, important safety cables located in containmentthat are required in case of LOCA/MSLB, are EPR/CSPE cables.
From 2008 to 2012, environmental measurements have been performed in NPP todetermine ambient conditions of cables in containment (temperature and dose rate). It has
permitted to determine the stress level to which cables are submitted in normal operationand to choose samples to expertise.
Then degradation states of aged samples coming from plants have been determinedthrough different methods (elongation at break, gel fraction, OIT, FTIR and NMR).
Électricité de France (EDF) has decided to take samples (EPR/CSPE), whose portions
have been submitted to more penalising environmental conditions (heating, radiation dose
rates). Other portions permit to have characterisation at different dose rates andtemperatures. Twenty and thirty years olds samples have been taken from plants.
These measurements will be used:•••

to determine the degradation of insulation materials
to confirm the ability of cables to withstand accidental conditions regarding pastexperimental studies andto improve the kinetics model and to verify its validity regarding themeasurements performed.

This experimental phase will be performed for three years period (2014-2017) for
900MWe-series. Next step consists of performing accelerated ageing on these samples todetermine the consumption of antioxidants after an additional ageing (for the next
10-20 years).
Condition monitoring of out-of-containment cables
From 2008 to 2012, environmental measurements have been performed on site todetermine ambient conditions of cables in specific places out of containment (temperature

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and humidity). This concerns especially locals with steam circuits and high loaded power
cables.
Focus is put on power cables, regarding temperature cycling and humidity issues.
EDF has decided to take samples, whose portions have been submitted to more penalising
environmental conditions (heating of conductor, humidity). 30-years olds samples havebeen taken from plants. Next step consists of determining the degradation of insulationmaterials (physical, chemical and electrical characterisations).
Diagnostic methods
Currently, main interest is focused on:•••

validating non-destructive methods used to localise degradation of the insulationmaterials on an anticipated way (for example, line impedance reflectrometry andtan delta),
developing non-destructive methods used to determine degradation of connectors(increase of contact resistance, diminution of traction force needed to lose
connection),
improving tests modalities to limit measurements uncertainties and to increase
reproducibility on micro sampling or thin layers.

7.4. Japan
Cable condition-monitoring technique
The new Nuclear Regulation Authority (NRA) has been evaluating Broadband
Impedance Spectroscopy (BIS) technique for application to condition monitoring ofelectric cables used in NPPs.
Cable samples of Flame Retardant Ethylene Propylene Rubber (FR-EPR) insulated cable
and Silicone Rubber (SIR) insulated cable, which are commonly used types of safetyrelated low-voltage cables, are aged by accelerated ageing to simulate the degradation bytemperature and radiation expected in operating NPPs.
The cable samples are tested in laboratories using the BIS technique, and the obtained
data are analysed to evaluate if the technique has enough detectability to judge proper
operation of cables during and after the design basis accident. This research programmebegan in 2012 and continued until 2016. Some information on this project is provided in
IAEA report in reference [14].

7.5. Slovak Republic
Since 2014, activities focused on the application of line impedance resonance analysis(LIRA) system into the ageing management programme and condition monitoring havestarted. Selected low voltage (LV) and medium-voltage (MV) cables in NPP aremeasured using both system and conventional time domain reflectometry (TDR) device
and suitability of LIRA system for application in cable ageing management programme(AMP) is analysed.
Environmental condition monitoring
Since the 2015 environment monitoring focused on cables is carrying out in Mochovce
NPP and Bohunice NPP to determine environment conditions (temperature, radiation

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dose, humidity) in selected areas within and outside containment. Data loggers,
temperature labels and alanine dosimeters are used as technical devices for monitoring.
The main purpose of monitoring is to get real information on conditions to which cables
are exposed and consequently localise hot spots. Detection of adverse environmentsallows us to manage these environments and/or mitigate their impact on cable. Obtained
real environment conditions can/will also be used for revaluation of cable qualified
lifetime.

7.6. Spain
In 2003, the Spanish Regulatory Body (CSN) and the Spanish Electricity Industry
Association (UNESA) initiated a joint research project (JRP) on the ageing of electricalcables at NPPs, made up of the following phases:
Phase one: PCI ES-13: “Surveillance of electrical cable ageing at nuclear power plants”
The main objective of this phase of the project carried out in 2004, was to define a“common basis action plan”, applicable to all the Spanish plants for the performance ofsystematic cable ageing surveillance programmes. The aim was, for these programmes, tobe aligned with the international state of the art in this area, and in particular with therecommendations and contents of the IAEA-TECDOC-1188, “Assessment andManagement of Ageing of Major NPP Components important to Safety: In-Containment
I&C cables”.
An initial activity of this project was an in-depth review of the national and international
literature (IAEA, NUREG, EPRI, Sandia reports, NRC documents, etc.) on cable ageingwith a report being drawn up.
As a basic conclusion to this phase of the project, it was determined that the ageing
surveillance techniques potentially appropriate for the types of cables in place at the
Spanish plants were: measurement of the compression module (indenter method),thermogravimetric tests (TGA) and induced oxidation time and temperature tests (OIT,
OITP).
Likewise, the following documents were drawn up for application at the different plants:
•
•
•
•
•
•

UNESA document Nº ES13/IT-01-103: “National and International Research andDevelopment Status Evaluation Report”
UNESA document Nº ES13/IT-02-0903: “Guideline for Monitoring of the Status
of Electrical Cables.”.
UNESA document Nº ES13/IT-03-0903: “Technical Procedure for theidentification of Critical Environmental and Service Parameters”.
UNESA document Nº ES13/IT-04-0903: “Selection of Circuits and Definition of
the Surveillance Programme”.
UNESA document ES13/IT-05-0903: “Technical Procedure for the Electrical
Characterisation of Cables”.
UNESA document ES13/IT-06-0903: “Technical Procedure for the Mechanical
Characterisation of Cables”.

Phase two: PCI ES-24 “Application of Advanced Techniques for the Diagnosis ofElectrical Cables at Nuclear Power Plants”
The basic objective of this phase of the project carried out over the period 2006-2009,
consisted of determining, in a practical manner, the applicability of the ageing

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surveillance techniques identified in previous phase one, for monitoring of the status of
the cables in place at the Spanish NPPs.
The project was performed by way of the following activities:
•
•
•
•
•

Collecting of cable samples (new and naturally aged) representative of thoseinstalled at the Spanish plants.
Thermal and radiation-induced ageing of these samples, for periods of 20, 40 and
60 years.
Acquisition of values of elongation at break (EAB) and tensile strength (TS) ofaged samples.
Application of selected techniques (indenter method, TGA, OIT, OITP) to aged
samples. Acquisition Validation and adjustment of results.
Comparison of the results of the techniques applied to the corresponding values of
EAB and TS, obtaining correlation factors between the test values and thedegradation of the aged cables.

The following different cable insulation and sheath materials combinations were tested:
EPR/CSPE,
ETFE/CSPE,
PVC/PE,XLPE/CSPE,
EPR/AFUMEX,
and
AFUMEX/AFUMEX.
This phase of the project has concluded that, for most of the tested cables, the indenter
modulus is the basic technique to be applied for assessing the cable condition. Indenter
could be complemented, where necessary, with the OITM and OITP techniques.
Acceptance criteria for each technique and type of cable were also determined. The TGA
technique did not prove, in general, to be applicable to determined cable condition.
Phase three: PCI ES-27: “Tracking and Assessment of Electrical Cables Status at the
Spanish Nuclear Power Plants”.
This phase of the project began in 2014, and is currently being carried out by UNESA andthe Spanish plants. The project is performed in response to the recommendations of
CSN, to verify the validity of the cable environmental qualification processes,
performed in accordance with IEEE-383-1974, as a result of the “uncertainties of thesequalification processes”, identified by recent international research programmes on cableageing (IAEA, NRC, NEA, Japan-JNES) (see Section 5 of this report).
The main objective of this phase of the project is to obtain “condition indicators” (CI) forthe cables, making it possible to effectively control their ageing status throughout thelong-term operating (LTO) period.
In this respect, new qualification tests will be performed, limiting the effect of theaforementioned uncertainties, on a representative sample of the cables in place at the
Spanish plants.
The tests will be performed on naturally aged (30 years) samples of cables taken from theplants, their ageing being completed to 40, 50 and 60 years by means of a sequence ofaccelerated ageing tests (thermal + radiation) with low acceleration factors and dose
rates. Subsequently, the accident radiation test and finally, the LOCA and post-LOCA
tests, will be applied.
During the process, samples aged to 40, 50 and 60 years will be extracted and different
surveillance techniques (elongation at break, indenter, insulation resistance, polarisationindex, etc.) will be applied to them, obtaining the corresponding CI values prior to andfollowing LOCA. In this way, the “critical level of degradation” (CLI) of each cable will
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be determined. Ageing management of the cables, using the defined CLI, will be assessed
throughout the long-term operating period.
The ageing test phase of the project was initiated in 2017. The completion of the projectis scheduled for the year 2020.

7.7. Switzerland
In line with chapter 7.1, the Swiss regulator has recommended the development andimplementation of a comprehensive and co-ordinated cable ageing management
programme for all NPPs. This is realised within the overall frame of the general ageing
management programme according to the Swiss law.
The basis for the ageing management of electrical components in the Swiss NPPs is a
specific guideline. Hence, for all components classified 1E according to this guideline,
type and manufacturer-specific fact sheets must be created. This includes electrical cables
that are necessary for ensuring that safety functions are fulfilled. Each fact sheet
comprises three parts: parts one and two have been jointly created for all Swiss NPPs,
while part three is plant specific because of the use of different cable types.
Fact sheet part one contain all potential ageing mechanisms in respect of the relevant
cable types obtained from the monitoring of the technical literature. Fact sheet part two
contains possible diagnostics methods, with which the potential ageing mechanisms canbe detected. Plant-specific fact sheet part three describes the applicable diagnostics
methods that are used in the plant-specific maintenance programme and in the regulations
for the periodic testing of cables. This closes the circle from ageing management tomaintenance. The fact sheets are revised every five to ten years. New findings fromscience and technology, from internal and external operating experience are thus
regularly incorporated in the ageing management and the maintenance programme. If
plant changes affect fact sheet part three, then the fact sheets are adapted.
The ageing management programme for electrical cables was developed by the licenseesof the Swiss NPPs. Plant-specific fact sheets for the class 1E electrical cables can bedivided into the following groups:
Group one:

Fact sheet for medium voltage power cables (≥ 1kV)Group two:Fact sheet low-voltage power cables (50V – 1kV)Group three:

Fact sheet for instrumentation cables (< 50V)

Group four:

Fact sheet for special mineral insulated cables (MI cable)

The Swiss cable ageing programme is also in line with IAEAs relevant TecDocs. A
detailed description according to the specification of WENRA about the cable ageing
programme has recently been published on the ENSREG website for her topical peer
review.
In Swiss NPPs, electrical cables laid in the plants are generally monitored by periodic
visual inspections and diagnostic measurements to detect any ageing. Operational ageing
management for cables is an extension of the originally performed qualification tests andis based on the monitoring of the change in the elongation at break of cable sample
materials. In most of the Swiss NPPs, cable samples that have been stored in high stresstest areas for cable pre-ageing, where there is a high radiation and thermal load, aremonitored in respect of their ageing behaviour. One Swiss NPP takes part in a German

CABLE AGEING IN NUCLEAR POWER PLANTS│ 33

34 │ NEA/CSNI/R(2018)8
joint programme (VGB) therefore. Also the cabling has been consistently replaced during
plant modifications. So different cables had to be qualified for their use in specificenvironment conditions and there data to be documented in the fact sheets.
A lot of research activities has already been done in Switzerland during 1990 to 2003 on
different cable types in different institutes e.g. Paul Scherrer Institute (PSI). At the
moment the research activities are focused on the possibility of a comprehensive
implementation of LIRA system into the ageing management programme (AMP) andcondition monitoring. Selected MV and LV cables in different CH – NPP are measured
using LIRA system and conventional TDR system. It is important to collect a lot of datafrom the cable and the environment condition on the whole cable way to get a
representative amount of data. Afterwards the analysing will hopefully show the cablebehaviour under different conditions. Also as a result we will obtain information about
the suitability of LIRA system for possible future application in cable AMP.
Condition monitoring
Since more than five years in different NPP in Switzerland part of the cables arecontrolled with the LIRA and the TDR method according their actual condition. To
implement such methods also for calculating and using for AMP the condition around thecables has to be measured and monitored continuously. Also you need the starting point
and a representative amount of data to forecast a future ageing. When a forecast is
possible, the method will be also compared with the Arrhenius model which is at the
moment used for calculation of the life time calculation of cables. Cables measured in2012 could now be re-analysed for the first time. Hence, for the first time it was possible
to determine the change in cable parameters over five years.
GeneralFor new cables so called finger print is done, to have an exact starting point after thecable installation and then the cables are measure in intervals (three to five years) to see atrend.
The LIRA method is useful for analysing the actual condition of the cable, but for theinterpretation of the data you need a specialist. The specialists are the bottleneck for thismethod therefore some power plants try to build up their own knowledge. LIRA and the
TDR measurements are going on in Switzerland. At this moment there are still notenough data available for a significant general output for installed cable.
According to the Swiss law, the ageing mechanisms applicable to the safety-relevant
electrical cables must be identified, a check must be undertaken to determine whether the
existing maintenance programme is suitable for promptly detecting ageing-induced
damage and the findings from ageing management must be incorporated in themaintenance programme. For this purpose, manufacturer information and findings fromoperating experience from Swiss plants and other comparable plants, and frommonitoring of the state of the art of science and technology must be considered.
In particular the accepted methods for prediction of potential ageing influences, the proofof accident-resistance, the cable type, the design specification, conditions of use, usage
time forecast as well as the type, scope and findings of conducted tests are in particular to
be recorded in the fact sheets for electrical cables. The periodic update of this informationin the database of fact sheets leads to a common and currently synchronised informationlevel, which aims to the same goal as outlined in chapter 1.2.

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7.8. United States
Submerged cables
The US NRC is investigating the issue of submerged cables and the safety implications.
Specifically, the suitability of condition-monitoring techniques is being evaluated to track
degradation in a submerged environment. In addition, this project aims to develop an
accelerated ageing plan for medium-voltage submerged cables. Following thedevelopment of a test plan, cables will be tested under these conditions and furthermore,condition-monitoring methods will be performed on submerged cables. Continued
research on the degradation of submerged cables, specifically, the impact of combined
stressors on ageing, end of life definition, and sensitivity of condition-monitoring tests, is
expected to follow.
A report on submerged cables was published on March 2015 [8].
Assessment of condition-monitoring methods for electrical cables
There are a variety of environmental stressors in nuclear power plants (NPPs) that can
influence the ageing of electrical cables, such as temperature, radiation,
moisture/humidity, vibration, chemical spray, and mechanical stress. Exposure to thesestressors over time can lead to degradation that may go undetected unless the ageing
mechanisms are identified, and electrical, mechanical, or physical properties of the cable
are monitored. Since some electrical cables never receive inspection, maintenance,
condition-monitoring tests, or periodic replacement, the degraded conditions in electricalcables could go undetected over time, which could lead to abrupt failures and prevent
various components from performing their safety function. Cable failures have resulted inplant transients and shutdowns, loss of safety redundancy, entries into limiting conditions
for operation and challenges to plant operators.
The US NRC confirmed in its review of Generic Letter (GL) 2007-01, “Inaccessible or
Underground Power Cable Failures that Disable Accident Mitigation Systems or Cause
Plant Transients,” that electrical cables are often overlooked or ignored in ageing analyses
and condition-monitoring evaluations, since they are passive components that are
generally considered to require no inspection and maintenance. However, electricalcables are very important safety components since they provide power to safety-related
equipment, and are used for instrumentation and control of safety functions. GL 2007-01
showed that a significant number of failures occurred under normal service conditions
within the service interval of 20-30 years, which is before the renewed licence period andbefore the end of the expected life span of the cables. The staff evaluation of the licensee
responses to GL 2007-01 concluded that licensees should have a programme for using
available diagnostic cable testing methods to assess cable condition. The staff finds thatcondition monitoring is essential for assessing the health and ageing degradation ofelectrical cables to ensure reliable operation of safety-related equipment, instruments, andcontrols during normal operations and design basis events.
This project will confirm the adequacy of the condition-monitoring methods, including:1) mechanical condition indicators (e.g. elongation, indenter methods, recovery time);
2) dielectric condition indicators (e.g. insulation resistance, dielectric loss, time domainreflectometry, line resonance analysis, partial discharge); and 3) chemical indicators(e.g. oxidation time/temperature, Fourier-transform infrared spectroscopy).
Condition-monitoring tests should be conducted on a variety of cables, including various
insulation types, low and medium voltage cables, power and instrumentation and control
CABLE AGEING IN NUCLEAR POWER PLANTS│ 35

36 │ NEA/CSNI/R(2018)8
cables, naturally-aged cables, and new cables. Naturally-aged cable samples as well as
new cables should be tested.
The first phase of the project will focus on assessing condition-monitoring techniques
during normal operational ageing. Thus, cables should be subjected to normal operating
conditions (temperature, radiation, humidity) in both mild and harsh environments tosimulate up to 40 years. For better estimates of cable performance, simultaneous thermal
and radioactive ageing should be performed to produce homogeneous degradation in thesamples (i.e. appropriate acceleration factors under oxidative conditions). Depending on
the insulation material and its sensitivity to acceleration factors, ageing of the samples
could take as long as nine months or more based on the type of insulation and known
characteristics.
The second phase will focus on cables subject to accident conditions and located in harshenvironments. The intention is to focus on pressurised water reactors only but later plans
will include testing cables under boiling water reactor accident conditions. These cables
should be exposed to simulated accident (temperature, pressure, humidity, radiation,
chemical/steam spray) conditions. The condition-monitoring techniques should be
evaluated for the capability to predict proper operation of cables during and after theaccident (post-accident period).
This project began in 2012 and it will continue until 2019. This report was published near
the end of the second term of the project.

7.9.

The International Generic Ageing Lessons Learned (IGALL) for Nuclear
Power Plants.
The IAEA Safety Standards NS-G-2.12 [10] requires that ageing and potential age-relateddegradation are considered in order to ensure the capability of the SSC to perform thespecified safety functions throughout its design life. Ageing in all conditions and plantstates including a postulated initiating event shall be taken into account. Provision shallbe made for monitoring, testing, maintenance, surveillance and inspections in order toassess ageing mechanisms predicted at the design stage and to identify unanticipatedbehaviour that may occur in service.
In order to assist its member states in dealing with the challenges associated with longterm operation (LTO) and ageing management (AM), the IAEA has published multiple
reports and conducted multiple programmes (e.g. SALTO and IGALL). General guidanceon methodologies and implementations of ageing management is provided by the Safety
Standard on Ageing Management [10] and in the SALTO reports [11] and [12]. Howeverthese documents do not provide information on specific degradation mechanisms of SSCs
or related mitigation-specific ageing management programmes (AMP).
To complement the existing guidance described above, the IAEA initiated in 2009 theextra-budgetary programme (EBP) on IGALL for nuclear power plants (NPPs) with theobjective to provide a current technical basis and a current practical guidance onmanaging ageing of mechanical, electrical and I&C components and civil structures ofnuclear power plants important to safety. Scope and frame of the IGALL programme wasinitially based on the US NRC Generic Ageing Lessons Learned (GALL) programme[13].

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The first phase of the IGALL program was conducted from 2009 to 2013, the second
phase was conducted from 2014-2015 and the third phase was finished at the end of 2017.
The IAEA IGALL database contains ageing management review (AMR) tables, ageing
management programmes (AMPs) and the time limited ageing analyses (TLAA). The
information contained in the IGALL database is based on approaches developed andimplemented in various types of reactors in participating member countries and it is
updated during each phase of the programme.
The following ageing management programmes of IGALL are connected with issues ofcables ageing, condition monitoring and qualification:
•
•
•
•
•
•
•

AMP201_Insulation Materials for Electrical Cables and Connections not Subject
to Environmental Qualification Requirements.
AMP202 Insulation Materials for Electrical Cables and Connections not Subject
to Environmental Qualification Requirements Used in Instrumentation Control
Circuit.
AMP203 Inaccessible Power Cables not Subject to Environmental Qualification
Requirement.
AMP206 Electrical Cable Connections not Subject to Environmental
Qualification Requirement.
AMP207 Environmental Qualification of Electrical and Instrumentation andControl Component.
AMP209 Ongoing Qualification of Electrical and I&C Components Relevant toan Environmental Qualification.
AMP210 Condition Monitoring of Electrical and I&C Cables Subject toEnvironmental Qualification Requirement.

The ageing management programmes (AMPs) collected in IGALL database describe theactions and procedures for manage and assess ageing effects and time limited ageing
analyses (TLAAs) describe how analysis of critical components in each plant type anddesign are done for the defined target of plant life time.
IAEA IGALL programme have only a single TLAA for electrical and I&C components:
TLAA201 Environmental Qualification of Electrical and I&C components. This TLAA
addresses equipment re-analysis or ongoing qualification methods to establish an
electrical and I&C equipment’s qualified life for the intended period of operation. In this
TLAA accelerated thermal ageing estimated with the Arrhenius model is referenced. Inorder to limit known uncertainties during cable qualification, the application of low dose
rate for accelerated ageing is suggested.

CABLE AGEING IN NUCLEAR POWER PLANTS│ 37

38 │ NEA/CSNI/R(2018)88. Actions in CADAK
8.1. Principal steps
It is recommended to partner with other international organisations to leverage resources
and prevent duplication of testing. For example, IAEA has conducted research on theageing and condition monitoring of low-voltage power and I&C cables – see IAEATECDOC-1825 [14]. Shared expertise and knowledge would be beneficial for both
regulators and utilities to develop cable ageing management programmes. Attending
relevant IAEA meetings and collaborating with cable experts from cable manufacturers,
utilities, and regulators allows for the wide dispersion of operating experience andresearch developments. For example, results from the IAEA research, including cabletechnical data, ageing characteristics, and condition-monitoring results, was planned to
add to the CADAK database for information purposes and for those countries
investigating cable research programmes.
Furthermore, EPRI (Electric Power Research Institute), UJV Rež (Institute of Nuclear
Research), and Électricité de France ( EDF) held an International Nuclear Plant Electrical
Cable Ageing Management Symposium in September 2013. This symposium wasattended by cable manufacturers, researchers, utilities, academia, and regulatory agencies.
Topics of discussion included medium voltage cable, cable ageing management,
manufacturing insights, condition monitoring, and acceptance criteria. CADAK wasplanned to be a resource for papers and presentations from such conferences as well as acollection on history records of cable testing, knowledge and expertise.
The goal of CADAK was to present the international research projects and cableconferences in order to collect information that would enhance the database and also, tobecome the premier database for electrical cable knowledge, expertise, and history.

8.2. Assessment of cable material of the decommissioned nuclear power plants
Cables are of key importance to the safe and reliable operation of nuclear power plants(NPPs). This is because of their widespread use as a connection medium with manysystems important to safety within NPPs. Further, given that most of the existing NPPs
are reaching or even exceeding their nominal design life, ageing impacts on cables is an
important phenomenon for many of these systems.
Some plants have adopted a prospect to extend their operating life to additional 40 or
more years beyond the original intended design life which also includes cables. It will
therefore be appropriate to ensure that sufficient safety margin is still available forenvironmentally qualified cables and other cables important to safety. This can be doneby studying samples of accelerated-aged cable in a laboratory and as assumed in modern
codes/standards and comparing these results with actual aged cables available in the
NPPs that have been recently shut down awaiting decommissioning or in thedecommissioned NPPs.

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NEA/CSNI/R(2018)8

The removal of cable insulation material from recently and permanently shut down and/or
decommissioned NPPs is important since it will provide useful experimental data for
the following purposes:••••

examining properties of naturally-aged cable insulation material versus those ofaccelerated-aged cable insulation material in laboratory as per modern
codes/standards;
evaluating the impact of synergistic effects for different degradation mechanisms
on removed and aged cable insulation material;
determining the validity of laboratory test results of accelerated-aged cableinsulation material;
verifying whether the removal of unnecessary conservatism is warranted while
maintaining sufficient safety margins.

There are currently underway various research projects in the nuclear industry to assess
cable insulation material removed from decommissioned NPPs. These projects willaddress the above four items, including identification of key operational variables related
to cable ageing, optimisation of inspection and maintenance schedules, as well as support
in modelling activities, surveillance, and testing criteria [1].
Furthermore, it is worthwhile to note that a number of insights come from the NEA
SCAP Project in years 2006-2010 [2]. These insights are: Selection of appropriate
activation energy, impact of simultaneous thermal and irradiation ageing, dose rate
effects, manufacturing tolerance and oxygen-starved chambers for LOCA tests.
With permanently shut down or/and decommissioned NPPs, the nuclear industry and theregulators have an opportunity to verify, validate and/or confirm the assumptions used as
the basis of current EQ for cables. Thus, the assessment of results on these cables (taking
into account the above four items) might improve the current EQ approach for qualifying
cables important to safety within NPPs.
If these assumptions above are validated, then the cable samples removed fromdecommissioning NPPs should be used to verify whether these cables are qualified for
additional qualified life beyond 40 years. This could be a good topic for future research or
discussion in international decommissioning programmes.

8.3. Ensuring the long-term operation
8.3.1. Qualification for operation time over 40 years
There is not so much operating experience of cables for NPPs beyond 40 years of life in
the world. In some NPP’s the aged cables in critical positions are changed withsignificant programmes and the modifications are done in order to provide milder
environment conditions (e.g. lower temperature and less radiation doses) for these cables.
In many other plants no significant ageing of the selected cable materials are notrecognised during long-term operation.
Many plants are reaching the end of the originally defined operation time 30 or 40 years
of cables. However, there is not typically a significant difference between the ageing
mechanisms of cables present after 40 years compared to those present after 60 years[13]. Most age-related degradation mechanisms occur slowly and, if unmitigated, and dohave the potential to gradually worsen over time and there is not typically a distinction
between the mechanisms present at 40 years compared to those present at 60 years.
Therefore, collected operating experiences and test results during 40 years operation can
CABLE AGEING IN NUCLEAR POWER PLANTS│ 39

40 │ NEA/CSNI/R(2018)8
be extrapolated into 60 years, when the safety margins are adequate. In most NPP’s thecontinuous monitoring and more comprehensive analysis by owner, reviewed byregulator in periodic safety review (PSR) every ten years is done for ensuring the safety.

8.3.2. Qualification for operation time over 60 years
As said above the extended operational licensed time frame over 40 years has been basedon renewing the ageing analysis of mechanical and electrical parts including cables andtheir EQ simulation and testing results for new 50 or 60 year life time target. In many
countries the approval means that the analysis and the test results for the new life time arecontinuously confirmed with operating experiences during operation andcomprehensively reviewed during PSR process.
In the USA nuclear industry has recently announced that a subsequent licensing renewal
application from 60 to 80 years is under consideration. Similar life time extension plans
are under consideration in many other countries. Demonstrating adequate cable
performance and ageing management in normal operation and post-accident services forthe periods over 60 years will be a demanding challenge. In considering operation morethan 60 years the method to extrapolate qualified life is more questionable, when existingmargins are eroded and the uncertainties inherent in the original sequential accelerated
ageing programmes become more demanding. Therefore, it looks obvious that approvalof life time over 60 years or even longer needs new test results and research as well as
more operation experiences and their analyses for recognising the critical subjects andtargets for additional inspections, assessments and preventive maintenance.

8.4. Forms of test data
Laboratories performing cable testing (used by regulators or utilities)
Performing cable testing requires specialised equipment and resources in the laboratory.
Laboratories have particular equipment to perform chemical, electrical and mechanicalcondition-monitoring tests. Some laboratories may concentrate on a particular area andutilities and research organisations should take advantage of the expertise. In IAEATECDOC-1825 [14] comparisons of various testing technics and test results of certain
laboratories are presented and compared. Based on the reference [14] the EAB, OIT and
OITP technics are useful and reliable to all low-voltage cable materials for measuring theageing effects.
Furthermore, cable ageing requires facilities that can execute thermal ageing, radiation
ageing, and perhaps, simultaneous thermal and radiation ageing. These facilities that canperform simultaneous thermal and radiation ageing are limited in number and sharing theidentity of these facilities would allow continued research. Many research organisations
do not have their own facilities for radiation ageing and it may be difficult to achievecertain dose rates or total dose at small facilities. Thus, sharing the facilities would allow
for more efficient research and for cable experts to collaborate on research.

8.5. Recent tests in Canada
The harvesting of systems, structures and components (SSCs) from decommissioned or
decommissioning nuclear NPPs becomes so important nowadays as explained in Section
8.2 and it is beneficial on making decision for the technical feasibility of LTO of NPPs.

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NEA/CSNI/R(2018)8

However, there are several challenges associated with harvesting materials from theseplants. These challenges are: the removal of material samples from a decommissioned
NPP is neither a compliance nor licensing activity for utilities or operators, high cost
related to carry out research activity on these materials, inaccessibility or contaminationof materials to be removed, accessibility of analysis and testing records (e.g. data,
samples, etc.), shipping or transportation concerns (nuclear waste or SSCs), etc.
For harvesting of cables, it should be noted that material properties of cables aged in realtime and real operating conditions can be significantly different from the properties
received by studying samples aged in laboratory and assumed in current codes andstandards.
Thus, Canada currently has a harvesting project on the analysis of degradation
mechanisms of cables from Gentilly-two (G-2) NPP. G-2 is a CANDU-6 (675 MW(e))
nuclear reactor which was permanently shut down in 2012 after 29 years of service. The
main objective of the cable harvesting project from G-2 is to better understand and assess
the ageing phenomena with real aged cables resulting from thermal and radiation ageing
and validate environmental qualification (EQ) process of cables.
The current status of this project is as follows: 1) the review of environmental conditions
and the selection of cables to be harvested from G-2 NPP were already completed by the
Canadian National Laboratory (CNL); 2) CNSC staff has recently witness the removal ofcable samples from G-2 NPP; 3) the cable samples removal will be completed in early
April 2017; and 4) preliminary testing results are targeted for September 2017. A variety
of both destructive and non-destructive techniques (e.g. dissipation factor, indenter, EAB,etc.) will be used to assess current cable degradation at G-2 due to thermal and radiation
ageing.
Figure 8.1. Pictures of Removal Cable Samples from Gentilly-2 Nuclear Power Plant

The current status of this project is as follows:
1) Preliminary results are currently available and are included in this report;

CABLE AGEING IN NUCLEAR POWER PLANTS│ 41

42 │ NEA/CSNI/R(2018)82) Final results will be available by the end of April 2018. A variety of both destructive
and non-destructive techniques (e.g. dissipation factor, indenter, EAB, etc.) is used toassess current cable degradation at G-2 due to thermal and radiation ageing.
The preliminary analysis results are the following:
For samples removed from Room #403, the tan delta ranges from 5.17% (AL22A) to
5.90% (AL16A & CJ67A). The lower value is related to the reference tan delta forunaged PVC33A (5.23%), whereas the upper value of 5.90% is associated with referencelaboratory tan delta measured for PVC33A after about 40 days of thermal ageing at
110˚C. Based on the PVC33A graph shown in Figure 8.3, the conservative end-ofservice-life point of 50% relative EAB (i.e. 214/2 =107%) would be reached after 200
days at 110˚C. At that point tan delta would increase to 7.5% for PVC33A. Therefore,
based on the tan delta results of all retrieved PVC33A samples, the expected remaining
life is the equivalent of at least 160 days at 110˚C. Using an activation energy of Ea =1.02 eV, 160 days at 110˚C corresponds to well over 100 years at 45˚C. This result is inagreement with the EAB results previously analysed for the PVC33A samples retrieved
from Room #R403. The analysis based on EAB results showed that the condition of the
PVC33A insulation samples removed from Room #R403 was similar to the condition ofunaged samples [5].
For samples removed from Room #R001, the analysis indicated that the cable Sample#QA61A is showing signs of significant degradation for the PVC jacket and to a lesser
degree for the XLPE insulation based on EAB results. This degradation is likely the resultof significant exposure to radiation in a room where fuel bundles were being transferred.
For the retrieved cable samples there was a broad variation in degradation (as per EAB
results) whether measurements were taken close to or away from a crack that wasobserved on the cable jacket. This trend is confirmed by the electrical dissipation factor
results. Tan delta measured away from the crack was 0.85%. However, at the insulation
location corresponding to the crack on the jacket, tan delta for Sample #QA61A increased
to 1.06% [5].
The insulation material of the cable Sample # BN18 removed from Room #R003 was
PVC91. The cumulated average temperature in Room #R003 was 29˚C, which isrelatively low. For PVC91, the activation energy used as part of the cable EQ process (asfound in the EQ assessment report) was Ea = 1.23 eV. Based on this assumed activationenergy and using reference EAB data, 29 years at 29˚C is equivalent to half a day at
110˚C. Therefore tan delta for the retrieved BN18R sample should be almost identical totan delta for the unaged reference PVC91 sample (i.e. 4.21 %). The measured tan delta
for Cable Sample BN18R was 4.39%, slightly up from the unaged reference value. A tan
delta value of 4.39% corresponds to about 18.5 days of thermal ageing at 110˚C
according to the reference PVC91 graph shown in Figure 8.2. Therefore, there is slightly
more damage than would have been expected assuming an activation energy of Ea = 1.23
eV. This result is in good agreement with the analysis conducted based on EAB measured
for Sample # BN18R [5].

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Figure 8.2. Reference EAB Results for Thermally Aged PVC 33A, PVC 36A & PVC 91 [5]Figure 8.3. Reference Tan Delta Results for Irradiated Belden XLPE and Rockbestos XLPE
Insulation

The goal of the project is to retrieve 92 samples from 47 different cables
currently installed in the Gentilly-2 reactor building but the following tables (Table 8.1
and Table 8.2 only covers a limit number of these cable samples.

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44 │ NEA/CSNI/R(2018)8
Table 8.1. Extracted Rows from the Cable Sample Characteristics (CNL)
Cable
ID#

EQ
Cable
(yes/no)Cable issafetysignificant?
For non-EQ
cables only

Cable
Description(Type, Voltage,
Total Length
Installed)

AL16

yes

Twisted Pair,
300V #16
NU,29579 m

AL22

yes

Twisted Pair,
300V #16
NU,42717 m

CJ67

yes

Twisted Pair,
300V #16
NU,73080 m

BN18

yes

Twisted Pair,
300V #16
NU,25440 m

QA61
QA61

no

3 cond #6 AWG,
600V

Cable Start Location(Room #, Room
Description,
Elevation, NT Group#: Average Service
Temperatures, NR
Group #: Average
Service Dose Rate)
R107, F/M Room(South), 23’-6”, NT#5:
45-50°C, NR#1: 3.3
rad/h neutron + 23
rad/h gamma

Cable End Location (Room #,Room Description, Elevation, NTGroup #: Average Service
Temperatures, NR Group #:Average Service Dose Rate)

Equipment
Involved

Insulation
Material

R501, Steam Generator Floor, 80’9”, NT#3, 35-40°C, NR#2: 0.04
rad/h neutron + 0.4 rad/h gamma

63332SV47#1,
SV48#1,ZS4
7#1,ZS48#1

PVC

R107, F/M Room(South), 23’-6”, NT#5:
45-50°C, NR#1: 3.3
rad/h neutron + 23
rad/h gamma

R305, Coolant System. (South),NT#1: 25-30°C, NR#2: 0.04 rad/hneutron + 0.4 rad/h gamma

63432-PT3K

R405, Primary Coolant
System, NT#1 : 2530°C, NR#2 : 0.04
rad/h neutron + 0.4
rad/h gamma,
R003, Access Area,
3’-6”, NT#1: 25-30°C ,NR#3: 0.0003 rad/hneutron + 0.015 rad/h
gamma,

R403, D2O Supply Pumps, 64’-6», NT#6 : 50-55°C, NR#2 : 0.04
rad/h neutron + 0.4 rad/h gamma,

T403, Electric
Equipment Room, 48’0 », NT7 : 40°C

JacketMaterial

NIR Group ID# forInsulation Material

G2 EQ
Dossier#

Location of Cable
Tray (CT#) or Cable
Electrical Conduits
for aged cables
sectionLocation ofcable section
to beretrieved asunaged (ormildly aged)reference
samplePVC

PVC33A

G2-QEQ57110007-1

R107 JB & Tray

PVC

PVC

PVC33A

G2-QEQ57110007-1

T=C R107, tray riser
R005 for refTray Riser in
R005 + good
ref in R305

63331LCV12

PVC

PVC

PVC33A

G2-QEQ57110007-1

C&T R403,

C&T R405 for
a PVC33A ref

R401, Zonal BL Settings , NT#2:
30-35°C, NR#3: 0.0003 rad/hneutron + 0.015 rad/h gamma)

63333LT14B

PVC

PVC

PVC91

G2-QEQ57110014-0

Tray and Conduits
REF

R003

R001, NR43532-PM2

XLPE

PVC

C In R001, Ref in
R006 and R007,
release date 1983

R006 andR007

List of locations toretrieve samples from(including Room #, Tray
# and Conduit #)One sample in R009 at
tray riser #1000 = Ref =AL16R; One sample in
R107 at 60800-JB1486 orin Trays #1135 or1134 =AL16A
One sample in R305 at
63432-PL1202 or in R009
at tray riser #1000 = Ref =AL22R; One sample in
R107 in Tray #1134 or at
63432-JB1489 = AL22A
One sample in R405 at
63331-LCV-12 = Ref =CJ67R; One sample in
R403 at 60800-JB-3485 =CJ67A
One sample in R003 at
60800-JB2014 = Ref for
PVC 91 which has aspectrum similar to PVC
101 and PVC 15 = BN18R
One sample in R006 or
R007 in Tray RWY#4011 =Ref = QA61R.; Onesample in R001 at 3532PM2 = QA61ACABLE AGEING IN NUCLEAR POWER PLANTS

NEA/CSNI/R(2018)8│ 45

Table 8.2. Results of Tensile, Electrical Dissipation Factor and Indentation Tests (CNL)
Cable ID#

Cable Sample Designation

Room #

Jacket and Insulation Cumulated
Average Cumulated Irradiation Dose EAB (%)
Material
Temperature (˚C)
(MRad)

AL16

AL16R Jacket

R501

PVC

36.0

< 4.0x10-3

Median258

AL16A Jacket

R107

PVC

tbd

tbd

AL16R Insulation

R501

PVC33A

36.0

tbd

AL16A Insulation
AL22R Jacket
AL22A Jacket

R107
R305
R107

PVC33A
PVC
PVC

tbd
25.9
tbd

AL22R Insulation

R305

PVC33A

AL22A Insulation
CJ67R Jacket
CJ67A Jacket

R107
R405
R403

PVC33APVC
PVC

CJ67R Insulation

R405

CJ67A Insulation

AL22

CJ67

BN18

QA61

Tan Delta (%)

Indentation Tests

Std. Dev.
23

N/A

Indenter Modulus (N/mm)
tbd

Recovery Time (s)
tbd

284

22

N/A

tbd

tbd

232

8

6.20

tbd

tbd

tbd
3.7x10-3
tbd

218
259
260

18
35
38

5.90
N/A
N/A

tbd
tbd
tbd

tbd
tbd
tbd

25.9

3.7x10-3

240

4

5.35

tbd

tbd

tbd
25.9
45.0

tbd
11.7x10-3
4.3x10-3

222
263
242

29
16
27

5.17
N/A
N/A

tbd
tbd
tbd

tbd
tbd
tbd

PVC33A

25.9

11.7x10-3

225

8

5.29

tbd

tbd

R403

PVC33A

45.0

4.3x10-3

216

7

5.90

tbd

tbd

BN18R

R003

PVC

29.0

30.0x10-6

291

15

N/A

tbd

tbd

BN18R

R003

PVC91

29.0

30.0x10-6

176

10

4.39

tbd

tbd

QA61R Jacket

T403

PVC

26.4

0.0

390

15

N/A

tbd

tbd

QA61A Jacket

R001

PVC

30.0

tbd

187/84

69/8

N/A

tbd

tbd

QA61R Insulation

T403

XLPE

26.4

0.0

486

54

0.93

tbd

tbd

QA61A Insulation

R001

XLPE

30.5

tbd

296

140

0.85/1.06

tbd

tbd

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9. Cable data analysis
The CADAK database includes 1 350 data sets from different countries with various
technical specifications. Large part of this data originated to SCAP project is from nonmember countries of CADAK and the detail information of the previous members are no
more available. There is also large variation of cable types and insulation materials in the
database. Differences in plant designs, in suppliers, in environmental conditions, instorage times, etc. have influence on the lifetimes of cables.
Based on these limitations the comprehensive analysis to the cable data in CADAK
database has not been possible to be elaborated to this report.

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10. Conclusions and recommendations

The Cable Ageing Data and Knowledge (CADAK) Project is the continuation of thecable ageing part of the NEA Stress Corrosion Cracking (SCC) and Cable Ageing
Project” (SCAP). SCAP was formally launched in June 2006 and officially closed with aninternational workshop held in Tokyo in May 2010. The results of SCAP are in reference[2]. Following the completion of the SCAP project, its SCC working group participants
were interested in some form of continuation and a new project was formed in 2011 bycombining OPDE and the cable ageing part of SCAP into the CADAK.
During the first term of CADAK an operational web-based database and a web-based,knowledge-based (KB) structure on SCAP were used. The type of information collected
includes regulations/codes and standards, and relevant documents on national activities in
the areas of inspection/monitoring/qualification, repair/replacement of cables as well as
on safety assessments and national R&D. The KB is intended to provide a source ofsystematically organised information for the project members.
Another objective in the first term of the CADAK was to define methods for collecting
national information and documents into the database was successfully performed insome member countries, which also started the collection work. However, not all member
countries started the use of the database and knowledge base during the first term of the
CADAK. After the first term it was evident that the CADAK could be successful if up-todate information is continuously added, and this information would greatly benefit
utilities and regulators in understanding cables. In addition, for developing ageing
management programmes, the CADAK should house current information and operating
experience on condition-monitoring tests and acceptance criteria.
For the second term, the CADAK project defined goals for analysis of cable data;
however, there are large variations of cable types and insulation materials in the databaseand differences in plant designs, in cable suppliers, in environmental conditions, instorage times, etc. that have an influence on the lifetimes of cables. Based on theselimitations, a comprehensive analysis of cable data in CADAK database was not possible.
The following recommendations are defined for future work in the area of cable ageing:•••

In future, the key objectives of work with cable ageing will be to encourage allcountries to support the multilateral exchange of test data and operating
experience of cables. If additional experimental studies allow the identification ofageing phenomena (generic issues) or improvement of associated kinetics andinfluence criteria, it should be published.
It is recommended that all international working parties in the field of cableageing exchange information with other international organisations (e.g. IAEA) toprevent duplication of research efforts.
The information obtained from the decommissioned nuclear power plants (NPPs)
should be used to verify, validate and/or confirm the assumptions used in the

CABLE AGEING IN NUCLEAR POWER PLANTS│ 47

48 │ NEA/CSNI/R(2018)8
current qualification for cables that are important to safety. Projects to collectcable samples removed from decommissioned NPPs should be used to verify
whether these cables are qualified for additional qualified life beyond 40 years oreven beyond 60 years. This could be a good topic for future research or discussion
in international decommissioning programmes.

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11. References

1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.

US DOE/NRC/EPRI: “Cable Research in Light Water Reactor Related to
Mechanisms of Cable Degradation: Understanding of role of material type,
history, and environment, as well as accelerated testing limitations...” April 2013.
NEA/OECD SCAP Project: “Technical Basis for Commendable Practices on
Ageing Management – SCC and Cable Ageing Project (SCAP), Final Report”,
December 2010.
CNSC, REGDOC-2.6.3, "Ageing Management", February 2014USNRC regulatory guide RG1.218: Condition-Monitoring Techniques forElectric Cables Used in Nuclear Power Plants, April 2012
CNSC-CNL Formal Progress Report #3, Analysis of Degradation Mechanisms ofCable Insulation due to Ageing in a Decommissioned Nuclear Power Plant, July
2017
IAEA, Assessing and Managing Cable Ageing In Nuclear Power Plants; NP-T3.6, Vienna, 2012
SAND 2013-2388 NPP cable materials: review of qualification and currently
available ageing data for margin assessments in cable performance, Sandia
National Laboratories, Albuquerque, NM, 2013
SAND 2015-1794, Submerged Medium Voltage Cable Systems at Nuclear
Power Plants: A Review of Research Efforts Relevant to Ageing Mechanisms
and Condition Monitoring, March 2015
CNSC, 13395-REP-00001, “Ageing Management of Cable in Nuclear
Generating Stations”, September 2012
INTERNATIONAL ATOMIC ENERGY AGENCY, Ageing Management for
Nuclear Power Plants, IAEA Safety Standards Series No. NS-G-2.12, IAEA,
Vienna (2009).
INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Aspects of Long
Term Operation of Water Moderated Reactor, IAEA-EBP-SALTO, IAEA,
Vienna (2007).
INTERNATIONAL ATOMIC ENERGY AGENCY, Safe Long Term Operationof Nuclear Power Plants. SRS No.57, IAEA, Vienna (2008).
UNITED STATES NUCLEAR REGULATORY COMMISSION, Generic Aging
Lessons Learned (GALL) Report, Final Report, NUREG-1801 Rev. 2, USNRC,
Washington D.C. (2010).
INTERNATIONAL ATOMIC ENERGY AGENCY, Benchmark Analysis for
Condition Monitoring Test Techniques of Aged Low Voltage Cables in Nuclear
Power Plants; Final Results of a Coordinated Research Project, IAEA-TECDOC1825; Vienna (2017).

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12. Appendix 1 CADAK Database and knowledge base
CADAK Database Management
Following a login and verification process via the CADAK web-interface(http://cadak.hrp.no/cadak), data entry, data modifications and data retrieval ismanaged via menus, links, input tables (sheets) and roll-down menus.

Database Data Entry and Modification
A database entry requires a certain number of mandatory items to properly identify
each data record. The number of such mandatory fields varies among the ten different
database parts. In addition, for each of the ten parts, follows a certain number ofrequired and optional items. Figure 1 and Figure 2 show examples of input tables for
initiating (mandatory fields) and modifying a database record.
Figure 1: Mandatory fields for a new database record (Part 1)

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Figure 2: First section of a sheet for updating required/optional items for a new/existing database record(Part 1)

Database Data Retrieval
Data records can be retrieved either by selecting from a record menu (see Figure 3, orby utilising the search tool. Figure 4 shows an example of a retrieved data record in“view” mode.

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Figure 3: Example of database record selection menu (Part 2.1)

Figure 4: Example of retrieved record data in “view” mode (Part 2.1)

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Database Lifecycle
Cable data will go through different lifecycle stages while being stored in the CADAK
Cable Ageing Database. During these lifecycle stages, different users will havedifferent access to the data.

User Categories
The following user categories are defined for the Cable Ageing Database:Table 1: User categories for the CADAK Cable Ageing Database

User category
Operator
National representative

Project representative
Administrator

Description
An industry representative or representative from a research facilityor alike that has collected cable data and inputs the data to the
database.
Main contact person for CADAK project in his/her country.
Responsible/supervisor for all operators in his/her country. Provides
data to the database either by having operators to contribute it, or byentering himself/herself.
CADAK Secretariat, CADAK Consultant.
The persons working at the Operating Agent.

Lifecycle Stages
Table 2 shows the lifecycle stages that are defined for the Cable Ageing Database
Table 2: Lifecycle stages for the SCAP Cable Ageing Database

Lifecycle
stage
Not Validated

Validated

Published

Description

Comment

The data is inserted
by an Operator (orNational
Representative), but
not yet validated by
the National
Representative
The data is validated
by the National
Representative, but
not yet published by
the Operating Agent.
The data ispublished.

This means: The data may be under insertion, i.e. theOperator (or National Representative) is stillworking/inserting. Or the data is readily inserted, but notvalidated by the National Representative yet, i.e. the
National Representative has not checked the validity of thedata submitted by the Operator (or National Representative).
This means: The National Representative has validated thedata entered by the Operator (or National Representative),and has informed the Operating Agent that this data can be
published.
This means: The Operating Agent has verified and publishedthe data in the database.

Lifecycle
Annex Figure 5 shows a state diagram explaining the lifecycle of an entry in the Cable
Ageing Database.

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54 │ NEA/CSNI/R(2018)8
Figure 5. Lifecycle of an entry in the Cable Ageing Database

Update by
OP or NR
Insert by
OP or NRNot
validated

Updateby OP

Validation by NR

Validated
Update byNR

Update by
OP or NR

Publication by CH

Deleteby CH

Published

Deleteby CH

Deleteby CH

Entries in parts 2.2, 2.3, 3, 6 and 7 of the database refer to cables defined in part one ofthe database. As a consequence, creation of entries in parts 2.2, 2.3, 3, 6 and 7 of thedatabase require the existence of at least one entry for that country in part one(i.e. existence of at least one cable defined by that country). Deletion of an entry inpart one of the database (i.e. deletion of a cable) requires that all data in parts 2.2, 2.3,
3, 6 and 7 of the database referring to that cable has been deleted.
Deletion of any data can be requested by all users. The National Representative who is
responsible for the data shall be consulted before deletion. Only the Operating Agenthas the possibility to delete data.

Data Access
Data Access Dependent on Lifecycle
Table 3 shows the access rights of different users to the data contained in the database,depending on the lifecycle.
Table 3: Data access depending on lifecycle
Lifecycle stage
Not Validated
Validated
Published

Reading access
The Operator providing the dataand his/her National
Representative; Operating AgentThe Operator providing the dataand his/her National
Representative; Operating AgentAll users

Writing access
The Operator providing the data andhis/her National Representative;
Operating AgentThe Operator providing the data andhis/her National Representative;
Operating Agent
Operating Agent

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NEA/CSNI/R(2018)8

The Cable Ageing Working Group has decided that the database will be kept “openaccess” within the member countries, to solicit maximum participation from theindustry. The open access policy was approved by the SCAP Management Board inJune 2008 and later confirmed by the CADAK Working group. Open access meansthat all users have reading access at lifecycle “published”.

User Configuration
Different access rights will be configured for different users of the database.
Table 4: Overview over users' access rights
User

Group

Operator

Country

Reading
accessAll data entries

Writing access

National
representative
Project
representative
Operating AgentCountry

All data entries

Project

All data entries

Data entries provided by thisoperator.
Data entries provided by thiscountry.
All data entries

Administrator

All data entries

All data entries

Handling of Change Requests
It is possible that a member of the Cable Ageing Working Group, the Operating Agentor other involved project members want to introduce changes to the Cable Ageing
Database, after the first release.

Changes in Roll-Down Menus
Adding a New Choice to a Roll-Down Menu
New choices in roll-down menus can be added according to the following procedure.
1.

A CADAK Cable Ageing project member initiates adding a new choice in aroll-down menu by sending a request (e.g. by e-mail) to the Operating Agent.

The Operating Agent decides if this request is considered a minor one (e.g. a project
member wants to add a new NPP in the list of NPPs) or a major one (e.g.
adding a new cable type). If minor change, go to step three, if major change,
go to step four.
The Operating Agent implements the requested addition to the roll-down menu andinforms all involved partners.
The Operating Agent notes the request and takes it to the next Working Group
meeting, where it is discussed and decided.
Adding a New Choice to a Roll-Down Menu where Choice "Others" is the Same
Several Times
For some roll-down menus, a choice “Others” is defined, with a text field following,where “Others” can be described.

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56 │ NEA/CSNI/R(2018)8
If the Operating Agent discovers or is notified that several users enter the same termfor “Others”, this new term can be added to the roll-down menu. The project members
will be informed about the change.
Changing or Removing a Choice from a Roll-Down Menu
Choices in roll-down menus could be changed or removed. However, this may lead toinconsistencies in already existing data. Therefore, this must be handled with care.
2.

A CADAK Cable Ageing project member initiates removing or changing a
choice in a roll-down menu by sending a request (e.g. by e-mail) to the
Operating Agent.

The Operating Agent checks if this change/removal would lead to inconsistency inexisting data. If inconsistency is discovered, the Operating Agent informs therequesting project member and asks for reconsideration of the change/remove
request.
In the case that the requesting project member maintains the change/remove request,
the Operating Agent takes it to the next Working Group meeting, where it isdiscussed and decided.

Changes of Database Items
Changes of database items are considered as major changes, and will always be
discussed in Working Group meetings. Changes of database items include:
Adding new items
Deleting existing items
Changing type of an existing item
Changing required/optional status of an item
Changes of Description and User Instruction / Note of Database Items
Changes of the columns “Description” and/or “User Instruction/Note” in the tables
sheets can be performed by the Operating Agent, either on request from a CADAK
Cable Ageing project member, or on the Operating Agent's own initiative.
All changes of this kind will be carefully considered by the Operating Agent before
they are accomplished.

Changes to Database Content
Provided the User having sufficient access rights to the data in question, making
changes to existing data can be obtained entering UPDATE mode, see example in
Figure 6. Nevertheless, the SCAP Cable Ageing Working Group decided in its 7th
meeting in September 2009 that changes to mandatory items, uniquely identifying adata record, must go through the Operating Agent, and they are not changeable fromthe table sheets. This provision has been continued in CADAK.

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Figure 6: Example of record data in “UPDATE” mode (Part 2.1)

Creating the Knowledge Space
Adding new elements to the knowledge base is made from a type selection drop-down
menu, subsequent to entering the actual part of “Knowledge Base”. Figure 6 shows anexample of the “Add new…” drop-down menu.
Figure 7: Add new document files to Knowledge Base from a drop-down menu

Knowledge Data Retrieval
Once elements have been added to the knowledge base, they can be extracted bychoosing from an element directory list. Figure 8 shows an example of an element list
for Part 2.2, and Figure 9 shows an example of a chosen document file. Following thelink will open the file.

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58 │ NEA/CSNI/R(2018)8
Figure 8: Select document files for retrieval from the Part document list

Figure 9: Document file selected – click link to open

CABLE AGEING IN NUCLEAR POWER PLANTS