This document discusses Hydro-Quebec's efforts to optimize the preventive maintenance program at their Gentilly-2 Nuclear Power Plant. It describes developing an integrated equipment reliability process focused on rationalizing preventive maintenance tasks based on criticality and cost-effectiveness. The document outlines applying a preventive maintenance optimization approach based on reliability centered maintenance principles and tools like the EPRI PM Basis Database. This involves analyzing existing tasks, critical equipment, failure modes and setting optimized task frequencies. It also discusses integrating performance monitoring and continuous improvement to form a comprehensive, living equipment reliability process meeting regulatory requirements.

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Correspondence Equipment Reliability Process Improvement and Preventive
Maintenance Optimization
Conference Paper · June 2004
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2. Correspondence: darragi.Messaoudi@hydro.qc.ca
Equipment Reliability Process Improvement and Preventive
Maintenance Optimization
Messaoudi Darragi*, Abdulnour Georges
Université du Québec à Trois Rivières
Cp.500, Trois Rivières, Qc, G9A5H7
Raynald Vaillancourt, Dragan Komljenovic, Michel Croteau
Gentilly 2 Nuclear Generating Station, Hydro Quebec
Abstract
The Gentilly-2 Nuclear Power Plant wants to optimize its preventive maintenance
program through an Integrated Equipment Reliability Process. All equipment
reliability related activities should be reviewed and optimized in a systematic
approach especially for aging plants such as G2. This new approach has to be
founded on best practices methods with the purpose of the rationalization of the
preventive maintenance program and the performance monitoring of on-site
systems, structures and components (SSC). A rational preventive maintenance
strategy is based on optimized task scopes and frequencies depending on their
applicability, critical effects on system safety and plant availability as well as cost-
effectiveness. Preventive maintenance strategy efficiency is systematically monitored
through degradation indicators.
Key words: Equipment, Reliability Process, Preventive Maintenance, Optimization
1 – Introduction
At the beginning of 2002, the Management of the Thermal and Nuclear Production
studied the possibility of increasing planned outages interval from 12 to 18 or 24 months
at the nuclear power plant Gentilly-2 (G-2) [1].
For applying this decision, it is necessary to ensure that:
- Risks for environment and population will not increase.
- Safety is maintained at higher levels.
- Forced outages, between planned outages, will not raise the number and/or
duration.
Such an increase in outages interval may have an impact on the management and
planning of preventive maintenance activities (time directed tasks, predictive tasks and
surveillance tests). In a mean and long term, negative impact may also affect equipment
reliability due to the decrease in preventive maintenance workload.
At the same time, the plant was involved in an equipment reliability improvement process
defined by both the Canadian Nuclear Safety Commission CNSC (Reliability program S-
98) [2] and World Association of Nuclear Operators (AP-913) [3]. A WANO expert team
has visited G-2 in April 2004 for conducting a survey based on the AP-913, and to ensure
a support in the preventive maintenance optimization activities related to AP-913.
These projects led to new requirements with regard to an optimization of the preventive
maintenance program in order to meet plant reliability and availability objectives.

3. Page 2 of 10
2 – Purpose and objectives
The purpose of these projects is to define and validate an equipment reliability process
focusing on two principal objectives:
- The rationalization and the optimization of the preventive maintenance program:
New preventive maintenance strategy should be based on rational task contents
and frequencies depending on their applicability, cost-effectiveness, and
especially critical effects on system safety and plant availability.
- Monitoring on-site system, structure and components (SSC) reliability and
performance through degradation indicators.
Such equipment reliability process should fulfill all plant requirements. This process has
to be integrated into the current reliability related processes without significant
modification and/or increase in the workload. This process should conciliate between the
equipment reliability process AP-913 suggested by WANO, nuclear industry best
practices (Streamlined RCM Processes and the state-of-the-art maintenance optimization
methods) [4], G2 processes and the S-98 regulatory requirements.
3 – G 2 Project Methodology
The equipment reliability process and the preventive maintenance optimization are based
on the following methodology:
1- Study the Preventive Maintenance Optimization in the nuclear industry: Make
synthesis on methodology, methods and tools of reliability centered maintenance,
Streamlined RCM and Preventive Maintenance Optimization processes applied in
the nuclear industry.
2- Study the AP-913 equipment reliability process: Compare it to streamlined RCM
processes and regulatory requirements (reliability program S-98 of the CNSC):
The aim is to design a generic process compiling those knowledge sources.
3- Elaborate an Equipment Reliability Process for SSC at G2 including the
Preventive Maintenance Optimization.
4- Carry out Gap Analysis between AP-913 (supporting all G2 Equipment
Reliability Process activities) and G2 Reliability Related Processes.
5- Plan the implementation of G2 Equipment Reliability Process through the
Preventive Maintenance Optimization Project.
4 – Preventive Maintenance Optimization
For reducing equipment failures and reaching reliability targets, consequences of
increased planned outages interval have to be controlled. Solution will be based on long
term SSC reliability improvement. An ideal solution lies in building an adequate process
to optimize maintenance and reliability.
Reliability Centered Maintenance was the first concept to arise [5,6,7]. It consists in
responding to 7 principal questions:
1- What are the functions and desired performance standards for the asset?
2- In what ways can the asset fail to deliver the functions and desired performance
standards for the physical asset?
3- What are the root causes (failure modes) for each functional failure?
4- What are the effects of each failure mode?

4. Page 3 of 10
5- Does the consequence of each failure mode matter (therefore is it worth doing a
task to prevent the failure mode?)
6- Can anything be done to predict or prevent the failure mode (What type of
predictive or preventive task)?
7- What if we cannot predict or prevent the failure (Can we do a failure finding task
for a hidden failure? Do we need to redesign the equipment or how we use the
equipment? Is no scheduled maintenance the correct strategy?).
The RCM process starts with the identification of the system limits, functions, functional
failure, failure modes and causes, component criticality to conclude with preventive
maintenance recommendations and tasks comparison. In a practical approach it is based
on 3 essential steps:
1- Functional and dysfunctional analysis.
2- Failure mode and effects analysis.
3- Selection of maintenance strategies through logic tree analysis.
Despite its rigor and consistency this process proved insufficiency to fit nuclear industry
requirements (example: time and resources consuming, highly conservative
environment).
Studies were undertaken to streamline this process through new simplified approaches
called "streamlined RCM". Functional and dysfunctional analysis step was simplified to
focus only on system important functions. In fact, RCM process works out the FMEA for
all the functions of the system independently of their importance, while in Streamlined
RCM approach, only important functions are analyzed.
In another hand, time used to conduct FMEA analysis for choosing the maintenance
strategy was saved by the use of Maintenance Templates (automated process).
Some approved streamlined RCM processes were experimented by the Electric Power
Research Institute EPRI [4] such us:
- Classical Streamlined RCM.
- Criticality Checklist Streamlined Process.
- Plant Maintenance Optimization.
Finally, a new streamlined concept of Preventive Maintenance Optimization called PMO
was experimented. PMO seems more like a concept rather than a unified formal process.
This concept has changed over years and was adopted in different ways in the nuclear
industry [8,9]. It is considered as one of the most viable methods for equipment reliability
improvement.
PMO is more streamlined using different personalized processes to fit real needs and
requirements of the nuclear industry. While RCM is based on functional and systems
analyses and built of a new preventive maintenance program, PMO concept is directed
towards the analysis and optimization of the existing preventive maintenance program.
Furthermore, it focuses only on dominant failures modes targeted by the existing PM
tasks.
In a weak preventive maintenance program, many failure modes are not addressed by PM
tasks. A PM task could also be evaluated in accordance with:
- Applicability, efficiency, intrusive risks and cost effectiveness.

5. Page 4 of 10
- Interval adequacy.
- Scope: failure mode targeted (evident / hidden, critical, degradation mechanism)
The first phase in a PMO project consists in performing a SSC Criticality Analysis. The
second phase focuses essentially on the following steps:
- Make a data gathering and collect all pertinent information on a SSC (all PM
activities, historical data, design manuals and vendor recommendations, etc.)
- Group all PM tasks by component
- Find out their targeted failure modes, causes and degradation mechanism or
simply compare them to the component maintenance template.
- Make the recommendations on tasks (addition, deletion, scope modification,
interval increase / decrease) based on a logical and systematic approach ( compare
to vendor recommendations and expert judgments, verify SSC historical data,
emphasis on predictive tasks, etc).
Consequently, PMO gained more popularity due to its simplicity of use and reduced
costs. Project costs decreased significantly based on streamlining Functional and FMEA
analysis. PMO reached its maturity with the initiation of project EPRI PM basis Database
[10,11,12,13,14].
PM basis Database was developed in 1998 by EPRI. The team carrying out the project
was built of EPRI consultants, maintenance experts and manufacturers. They compiled
information on 60 generic components of 49 American nuclear power plant over 20 years
of nuclear experience. The database recommends optimal PM tasks, their intervals
according to: Criticality, Service conditions and duty cycle. It offers also an exhaustive
generic database helping to analyze degradation mechanisms, stress factors, failure
timing, discovering preventive opportunity, etc (Figure 1).
Figure 1: Degradation Mechanisms and Maintenance tasks relationship
5 – A-913 Equipment Reliability Process
A whole Equipment Reliability process deals with preserving operational reliability level
asymptotic to the intrinsic reliability level defined in the design stage of the equipment.
However, PMO process demonstrated limits to achieve this ambitious objective. The lack
is caused by overlooking the integration of several PM related activities essential to
preserve high equipment reliability.
Degradation
location
Degradation
mechanism
Degradation
influence
Degradation
progression
Failure
timing
Maintenance
task

6. Page 5 of 10
In March 2000, World Association of Nuclear Operators (WANO) and Institute of
Nuclear Power Operations (INPO) worked out a generic Equipment Reliability Process
entitled AP-913 [3]. AP-913 is a process integrating 6 principal activities:
- Scooping and Identification of Critical components.
- Performance Monitoring.
- Corrective Actions.
- Continuing Equipment Reliability Improvement (analogous to a Preventive
Maintenance Optimization).
- Long –Term Planning and Life Cycle Management.
- PM Implementation.
Numerous North American nuclear power plants have been trying to implement this new
process through the modification and the improvement of their own processes [15].
Regarding Canadian perspectives, AP-913 answers without additional efforts the greater
part of S-98 reliability program requirements (CNSC). The AP-913 implementation was
also facilitated through the use of EPRI PM basis Database.
6 – G2 Equipment Reliability Process
The Gentilly 2 Nuclear Power Plant already possesses its reliability and maintenance
program. However, based on new knowledge and tendencies presented above, the plant
management wants to optimize these programs. This approach should allow to:
- Rationalize and optimize maintenance activities.
- Monitor Systems, Structures and components degradations before point of failure
(inside PF interval).
- Make a living equipment reliability process through internal and external
experience feedback.
A project is created and conducted to reengineer and provide a new process able to fit:
- G2 reliability and maintenance needs.
- WANO best practices requirements.
- CNSC regulatory requirements.
- State of the art knowledge in Preventive Maintenance Optimization in nuclear
industry.
The new G2 Equipment Reliability Process is composed of three principal activities
based on:
1- Preventive Maintenance Optimization PMO.
2- Performance monitoring.
3- Living program
The PMO process has been so far the first targeted activity by the management. The
different steps of the PMO process were defined and the action plan was scheduled
specially for I&C components in first. The approach adopted was as follow:
Stage one:
Efforts are focused on the optimization of the existing PM program. All equipments
targeted are in the Preventive Master Equipment List (PMEL). After 20 years of
operating experience at G2, PM activities are mature enough to address degradation
mechanisms causing important functional failures.

7. Page 6 of 10
Stage two:
Efforts are focused on equipments in the Master Equipment List (MEL) but not covered
by PM activities. The aim of this phase is to make sure that all important equipments of
this list are covered by appropriate PM activities.
However, the following steps have to be previously completed:
- Define"G2 Criticality Criteria" for components and align them to both AP-913
and "EPRI Criticality Criteria".
- Work out a "Decisional Logic Diagram" for the "G2 PMO process".
- Make a model for "G2 PM basis".
- Create "As-Found Conditions" codes for equipments at G2.
- Develop a database to support all those activities.
Flowchart of this process is shown in figure 2. Some routine activities are performed in a
systematic way every week as follows:
1- PM Tasks Priorization and Components Selection (1.1): Select PM bundles
fixed in the schedule. Priories PM tasks based on "lowest interval criteria" to
define components list of the week. Other criteria may be considered to close the
list (example: consider identical components) in order to ensure a fast
optimization and a quick win approach.
2- Data Collection (1.2): Collect information and data on selected components such
as: PM tasks, historical data, vendor’s recommendations, EPRI Maintenance
Template, general references (EPRI, WANO, SOER, etc).
3- Component Criticality Analysis (1.3): Evaluate components criticality and
define list of Critical, Non Critical and Run to Failure (RTF) I&C components
according to G2 criticality criteria.
4- PM Tasks Elimination (1.4): For RTF components eliminate PM tasks.
5- Service Conditions and duty Cycle evaluation (1.5): For Critical and Non
Critical components evaluate Service Conditions and Duty Cycle using EPRI
criteria [11].
6- G2 Decisional Logic and PM Tasks Comparison (1.6): Apply G2 Decisional
Logic (proper to PMO project scope):
a. Make comparison (task interval and/or scope) between current G2 PM
tasks and those proposed by EPRI PM Basis Database and other internal
land external sources.
b. Consult corrective and preventive work history done on the component for
the last years (10 years for I&C).
c. Consult general references (EPRI, WANO, SOER, etc.) if necessary.
d. Make change on interval and / or scope of PM tasks based on
recommendations such as EPRI Templates Maintenance, component
history, vendors PM programs, external experience and expert judgements.
Plan changes on PM tasks scopes in next step to accelerate the quick win
process.
e. Emphases on the use of predictive maintenance technologies if possible
and priories such tasks for Non Critical Components to manage risk.

8. Page 7 of 10
f. Add new PM tasks if necessary based on component historical data
(dominant failure modes and degradation mechanisms experienced in the
past at G2 and not targeted by PM tasks) and on external experience
feedback (Serious failure modes and degradation mechanisms experienced
elsewhere and not targeted by PM tasks at G2).
7- Process results documentation (1.7): Document all steps of the process and the
results.
8- Action plans definition (1.8): Ensure definition of action plans and PM
modifications to support implementation.
The success of PMO process implementation is conditional to ensuring the two essential
activities of the whole G2 Equipment Reliability Process:
- Performance Monitoring (2): Defining Monitoring Plans, Component
Performance Monitoring through Degradation Indicators, Cross-Systems
Analysis, Indirect Monitoring through Maintenance and Reliability Ratios.
- PM implementation and "Living Program" (3): Follow-up action plans,
Corrective actions and apparent/root cause analysis, equipment as-found
conditions, equipment performance criteria adjustment and finally measure PMO
process performance and associated profits.

9. Page 8 of 10
Figure 2: PMO Process Flowchart at G2
G2 Equipement Reliability Process
1-Preventive Maitenance Optimization
(PMO)
1.1- PM tasks
priorization and
components
selection
1.2- Data
Collection
1.3- Component
Criticality
Analysis
1.4- RTF
components:
PM tasks
elimination
1.5- Service
Conditions and
duty Cycle
evaluation
1.6- G2
Decisional Logic
and PM tasks
comparison
2- Performance Monitoring
1.7- Process
results
documentation
1.8- Action plans
definition
3- PM implementation and
Living program
7 – Gaps analysis and PMO project action plan
A gap analysis was carried out with WANO technical assistance for improving
preventive maintenance and equipment reliability. This analysis allowed to:
- Evaluate G2 reliability related processes according to AP-913 activities. This
action helped to confirm the steps defined by the G-2 Generic Equipment
Reliability Process.
- Determine the action plan for the PMO process: I&C components are first
analyzed because they are considered as a potential source of improvement .
PMO project is synchronized with Maintenance Schedule and begins with more frequent
PM tasks (weekly PM tasks first) two meetings per week. Principal project elements such
as team structure, schedule and process performance indicators are as follows:

10. Page 9 of 10
Team structure
- Process owner: Technical services.
- System engineers: Concerned by PM scheduled in 16 weeks.
- Reliability engineer (safety aspect): PMO coordinator.
- Reliability engineer (maintenance aspect): Maintenance advisor.
- Component engineer: Component expert.
- Maintenance supervisor: I&C Supervisor.
- Maintenance scheduler.
Schedule
- At T-16:
 System engineers identify criticality (AP-913) and technical basis.
 Reliability identifies criticality (S-98) and Maintenance Templates.
 Maintenance reviews files (history) and scope.
 Maintenance scheduler reviews criticality.
- At T-15: PMO team meeting: review and recommendations.
- At T-14: Risk decision by Technical Service Manager.
- At T-13: System engineers review PM tasks and updates Computerized
Maintenance Management System (SGE & SIE).
- At T-12: Modify schedule, if frequency reduced or PM task removed (RTF).
- At T-0: Execute I&C PM tasks and document As-found condition.
- At T+1: Feed back for As-found Condition (next PMO team meeting).
Process performance indicators
- Number of man-hours spent on PM (monthly, annualized).
- Number of man-hours spent on corrective maintenance (for non R-T-F).
- Number of PM task optimized, dropped, added, frequency reduced, frequency
increased.
- Review nuclear safety comity indicators.
- Review improvement comity indictors to ensure reliability and nuclear safety.
8 – Conclusion
G-2 has defined its specific Equipment Reliability Process witch will help optimizing the
preventive maintenance program especially after increasing outage intervals. This
Equipment Reliability Process is based on the integration of a broad range of equipment
reliability activities. It has the ability to discover equipment degradations “As-found
equipment conditions” before the failure occurrence, to rationalize and optimize
preventive maintenance activities and to monitor equipment and system. All those
activities were integrated into the living program, which is constantly updated through
internal and external experience feedback.
In general, the use of an Equipment Reliability Process to optimize preventive
maintenance is considered very important for aging nuclear power plants such as G 2 and
for the nuclear industry in general. The need to measure, maintain and optimize
equipment reliability led quickly to a world tendency in general and particularly in the
North American Nuclear Industry. This tendency was confirmed by the elaboration of
generic processes (AP-913 of World Association of Nuclear Operators), best practices
methods (Streamlined RCM and Preventive Maintenance Optimization projects),

11. Page 10 of 10
confirmed tools (EPRI PM basis Database) and regulatory requirements (Reliability
Program S-98 of CCSN).
In conclusion, the use of EPRI PM Database will help to evaluate results and will be an
essential tool to implement in the future in a practical way, such a process.
References
1- Vaillancourt R., D. KOMLJENOVIC, Assessment of the impact on safety with regard
to change in outage interval from 12 to 18 or 24 months at gentilly-2 nuclear
generating station, CNS 2003.
2- Commission Canadienne de Sûreté Nucléaire, Norme d'application de la
réglementation S-98, Programme de fiabilité pour les centrales nucléaires,
Ottawa, 2001.
3- INPO, Equipment Reliability Process Description, AP-913, Rev. 1, March 2001.
4- EPRI, Comprehensive Low-Cost Reliability Centered Maintenance , EPRI TR –
105365 September 1995.
5- Moubray J., Reliability Centered Maintenance, Industrial Press, April 1997.
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1998.
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