Gentilly 2 Nuclear Generating Station
Approach Regarding the Implantation of S-98 Reliability Program at the Gentilly 2 Power Plant considering AP-913 Equipment Reliability Process Dragan Komljenovic*, Raynald Vaillancourt, Darragi Messaoudi
Summary The Canadian Nuclear Safety Commission incorporates a new Regulatory Standard S-98, Reliability Program for Nuclear Power Plants. The licensees shall be conform to standard’s requirements by the end of 2005. This paper presents the approach adopted at Hydro-Québec (Nuclear Power Plant Gentilly 2) to meet S-98 requirements considering the WANO/INPO AP-913 Equipment Reliability Process. Key words:
Reliability, Program, S-98, AP-913, Equipment
1. Background Hydro-Québec was informed of Canadian Nuclear Safety Commission (CNSC) intent to incorporate CNSC Regulatory Standard S-98, Reliability Programs for Nuclear Power Plants (NPP) into Power Reactor Operating Licenses prior to the end of 2005. CNSC also requested that licensees report on S-98 compliance status beginning with the Annual Reliability report for 2003. Since the Gentilly 2 NPP already possesses a reliability program [3], some modifications are necessary in order to meet S-98 requirements. Nonetheless, two other events influenced the G2 orientation in organizing activities to meet S98 requirements: 1)
The first event is associated to the will of the Management of Thermal and Nuclear Generation to optimize plant’s preventive maintenance program. Therefore, the Gentilly 2 NPP received in 2004 a WANO expert group for technical discussions with regard to the PM Optimization. At the same time, the WANO team would have performed a gap analysis between the INPO/WANO AP-913 Equipment Reliability Program and the same process at G2. In preparation for this review, a comparison between S-98 and AP-913 requirements was also performed. We stated that there is a high degree of correspondence between these two processes.
2)
The second event is related to the project with regard to the outage interval extension. The Plant Management wants to extend the planed outages of the Gentilly 2 NPP from 12 to 18 or 24 months. This decision should enable a decrease in outage frequencies without increasing significantly their duration. However, one should: ensure an acceptable safety margin, and avoid an increase in number and/or duration of unplanned shutdowns. The outage extension affects: organisation/planning of maintenance activities during planned shutdowns, and longterm SSC reliability.
The common requirements for S-98 and AP-913 implementation as well as for a successful outage interval extension are related to a coherent and optimized reliability and maintenance program. This paper presents the G2 approach in dealing with this issue.
*Contact:
[email protected]
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Gentilly 2 Nuclear Generating Station 2. Objectives The main objectives of this paper are as follows: 1. Compare S98/AP913 requirements and determine their common areas. 2. Present the G2 approach in modifying the plant’s current Reliability Program in order to meet S-98 requirements. 3. Demonstrate the feasibility of elaborating the plant reliability program corresponding to S-98 Standard by using main parts of AP-913 Process. 3. Overview of S-98 The objective of the reliability program (RP) described in the S-98 standard is to ensure that risk-significant systems (RSS) of the Nuclear Power Plants (NPP) can do function reliably, in accordance with the relevant design, performance, and safety criteria, including the safety targets of the plant and CNSC license requirements [1]. CNSC gives the following definition for Risk Significant Systems: A Risk Significant System of a NPP is any system of the plant that, if it fails to meet its design and performance specifications, could result in unreasonable risk to the health and safety of persons, to national security and to the environment. As one may conclude, the S-98 standard envisions covering the reactor safety, national security, environment, and worker health and safety. The issue of the both national security and environment will be considered in ulterior stages of the S-98 implementation process. Table 1 lists the requirements for the RP [1]. 4. Overview of AP-913 INPO has provided the nuclear industry with a detailed technical process for identifying maintenance activities to maintain or improve the reliability of equipment to safety and/or economics [2,8]. In accordance with [2], the equipment reliability process represents the integration and coordination of a broad range of equipment reliability activities into one process for plant personnel to: Evaluate important station equipment, Develop and implement long-term equipment health plans, Monitor equipment performance and condition, and Make continuing adjustments to preventive maintenance tasks and frequencies based on equipment operating experience. This process includes activities normally associated with such programs as: Reliability centred maintenance (RCM), Preventive maintenance (periodic, predictive, and planned), Maintenance Rule, Surveillance and testing, Life cycle management (LCM) planning, and Equipment performance and condition monitoring. Table 1 shows the objectives of AP-913 Equipment Reliability Process [2].
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Gentilly 2 Nuclear Generating Station In accordance with the objectives of this programme, it facilitates the operational experience feedback and its implementation into the process and its improvement. It is worth mentioning that AP-913 goes beyond the safety scope only. Undoubtedly, its first preoccupation is the safety (see point b in Table 1 and the ERP’s structure in Figure 1). However, the whole process also considers the power generation. This way, the optimization process involves both safety and economic considerations, and helps improving the entire NPP performance in a structured manner. It divides the Equipment Reliability Process into six areas, each with a number of subordinate elements. Figure 1 depicts a top-level diagram of this process. The approach based on AP-913 represents an integral reliability process recognized, validated and approved in the nuclear industry. The AP-913 Program has been integrated in various degrees in virtually all nuclear power plants in USA, and represents the blueprint that these plants are adopting to implement as their equipment reliability process [7]. As an example of a very successful implementation of a well structured reliability program based, among others, on AP-913 ERP and RCM is the Palo Verde NPP [10]. In 2002, this plant reached a new record of 94.4% capacity factor. Equipment reliability programs are seen as a long-term investment at Palo Verde [10].
Performance Monitoring
PM Implementation
Corrective Actions Identification of Critical SSC
Continuing Reliability Improvement
Long Term Planning and LCM
Figure 1: Top-level Diagram of the AP-913 Equipment Reliability Process 5. Common Requirements and Similarities Between S-98 and AP-913 If one analyses both the objectives and the spirit of AP-913 ERP and its equipment performance objectives, one may conclude that they are quite comparable with the same elements of S-98 Standard and its application guide G-98. Figure 2 and Table 1 demonstrate these links.
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Gentilly 2 Nuclear Generating Station With the approach based on AP-913, one may meet S-98 requirements by acting on critical and risk significant SSC. This path forward would take more time but may provide a better long term system and equipment performance. It enables significant gains with regard to the both safety and power generation. We also hope to address issues related to outage interval extension with this reliability and maintenance process. Risk Significant Systems/Critical SSC Identification
Criticality Rank
Reliability Targets
Establish Perform Criteria &Monit. Paramet.
Continuing Reliability Improvement
Maintain the Performance
Failure Modes
Corrective Actions
Audit the Program
AP-913
Monitoring
Failure Modes
Performance
S-98
Identification and selection of critical SSC
PM Implementation
Long-Term Planning and LCM Figure 2: Common S-98 and AP-913 requirements 6. Planned activities at the G2 NPP A plan has been elaborated at the G2 NPP to organize work activities necessary for adequately modifying the existing plant’s reliability program in order to meet the requirements of the S-98 Standard. The main topics of this plan are as follows: a) Identify and rank the RSS, and specify their reliability targets; b) Adapt the reliability assessment process (modeling, evaluation, reporting, reliability model updating) to the S-98 requirements; c) Define surveillance activities (preventive maintenance program, surveillance testing, inspections) to ensure the reliability of the RSS; d) Reliability and performance monitoring of the RSS; e) Regulatory Reporting; f) Document the Reliability Program. The above division also corresponds to the organization of activities utilized by the S-98 work group. This group is sponsored by COG Nuclear Safety Committee (COG-NSC). After analyzing the interdependencies of enumerated topics, one may conclude that their activities are narrowly interlinked. Each activity influences more or less another. The general schema is presented in Figure 3. Page 4 of 9
Gentilly 2 Nuclear Generating Station
Reliability Program Adapt the relability assesment process
Define surveillance activities
Identify and rank the RSS Specify the reliability targets
Reliability and performance monitoring of the RSS
Regulatory Reporting
Figure 3: Interdependencies Between Activities in the Reliability Program 7. Methodology The following methodology has been defined to specify the necessary work plan activities at the G2 NPP regarding the compliance with S-98 requirements: a) Participate in activities of a work group formed to establish a common industry approach for defining and implementing nuclear station reliability programs concerning the S-98 standard [4]; b) Perform a detailed analysis of current reliability activities, records and documents at the G2 NPP (i.e. current plant’s Reliability Program), and compare them with S-98 requirements. This analysis gives a detailed gap assessment with regard to the present G2 Reliability Program vs. the S-98 requests. A detailed description of latter is given by an application guide G-98 [5] [11]; c) Perform a detailed analysis of AP-913 (INPO/WANO) Equipment Reliability Program [2], and define fields where this program coincides with the S-98 requirements [7]. The conclusion is that the AP-913 Process may be useful in defining numerous activities such as: various methods to determine critical Systems, Structures and Components (SSC) [6], performance monitoring, continuing reliability improvement, surveillance testing, maintenance and inspections. It does not cover activities such as: reliability modelling and mandatory reporting. The links between S-98 and AP-913 are demonstrated on Fig. 2 and Table 1. The orientation to consider parts of the AP-913 Equipment Reliability Program (ERP) is based on the fact that there is a similar or identical approach in key program topics. Page 5 of 9
Gentilly 2 Nuclear Generating Station 8. Present Development As already mentioned, the G2 NPP has a documented Reliability Program [3]. The above mentioned analysis allowed an identification of further activities necessary to fulfill the S-98 requirements. In accordance with the CNSC deadline, the previously presented work plan topics, and the defined activities, we have determined both an global effort assessment (manhours) and an approximate execution schedule. Table 2 shows the list of these activities. Some of these activities were realized, and some are under work. The comparison between S98 and AP-913, as well as the gap analysis between S-98/AP-913 and G2 Processes enabled to define an action plan, where the current G2 Reliability Program will be adapted. It should allow fulfilling main S-98/AP-913 requirements. As an example of realized activities, it is worth mentioning a pilot project on the PM optimization of stand-by DG, which was already completed. A second pilot project gets started with regard to the reliability improvement and PM optimization on Instrumentation and Control equipment. Both programs are based on EPRI PM Database [9] and AP-913 ERP. In accordance of present degree of compliance, the G2 NPP may meet both S-98 requirements and the deadline in nuclear safety field. The strategy at G2 is also oriented to synchronize planned S-98/AP-913 activities with other plant’s projects where a common interest exists. It ensures some benefits: Share of necessary resources More confidence to elaborate an exhaustive methodology An integrated approach and the coherence of more projects Synergy and a good communication of involved people. The following projects share activities with S-98 project: Outage extension from 12 to 18 or 24 months Maintenance optimization and rationalization (based on AP-913 ER Process) Impairment manual PSA Project and Refurbishment Project Modification of the equipment and system list followed in Appendix G of OP&P Project of Environmental Qualification
Equipment Aging and Life Cycle Management
9. Conclusion This paper focuses on an approach with regard to the S-98 implementation at the Gentilly 2 NPP. The initial stage considers the reactor safety aspect only. The methodology developed to meet the S-98 requirements resumes in some key points: 1. Participation in activities of a working group sponsored by the COG-NSC with regard to S-98 Standard. 2. Gap assessment between S-98 requirements and the current Reliability Program at G2. 3. Utilization of WANO/INPO AP-913 Equipment Reliability Process for defining main activities necessary to fulfil S-98 requirements (criteria to scope critical SSC, approach for improving and optimizing reliability, surveillance and monitoring activities). 4. Share information and resources with some ongoing G2 projects. Page 6 of 9
Gentilly 2 Nuclear Generating Station This approach enabled elaboration of a list of activities necessary for complaining with S-98. These activities have to be realized before the end of 2005. The G2 strategy in implementing S-98 will be based on AP-913 Reliability Process in the areas where these programs have common requirements. This way, we may grant significant gains with regard to the both safety and power generation. Some problems related to the outage interval extension would also be addressed by this approach. The approach based on AP-913 Reliability Process: 1) Rrepresents an integral reliability process recognized, validated and approved in the nuclear industry. The AP-913 is the blueprint that nuclear plants in USA are adopting to implement as their equipment reliability process. Thus, this programme facilitates the operational experience feedback and its implementation into the process and its improvement in a structured manner. 2) Might also be interesting for other Canadian nuclear utilities in implementing S-98 requirements. The further work will also be based on a wide collaboration with our partners in the nuclear industry as well as with CNSC, WANO, EPRI etc. 10. References 1.
Commission Canadienne de Sûreté Nucléaire, (2001), Norme d'application de la réglementation S-98, Programme de fiabilité pour les centrales nucléaires, Ottawa.
2.
AP-913, Equipment Reliability Process Description, Revision 1, (2001), INPO Atlanta.
3.
Hydro-Québec, (1998), Document de référence DR-12, Programme de fiabilité, Révision 1.
4.
CANDU Owners Group – Nuclear Safety Committee, (2003), Terms of Reference for Industry Working Group on Nuclear Plant Reliability Programs, Toronto.
5.
Canadian Nuclear Safety Commission, (2001), Regulatory Guide G-98, Ottawa.
6.
Critical Component Identification Process – Licensee Examples: Scoping and Identification of Critical Components in Support of INPO AP913, EPRI, Palo Alto, CA:2003. 1007953
7.
AP-913 Industry Capabilities Gap Analysis Results, EPRI, Palo Alto, CA: 2002. 1003478.
8.
Risk Informed Asset Management (RIAM) Development Plan, EPRI, Palo Alto, CA: 2001. 1006268
9.
PM Basis Version 5.0 with Vulnerability Analysis Module, (2003), EPRI 1009275.
10.
The Nuclear Professional, (2004), Raising the Bar, Palo Verde’s Secret for Good Equipment Reliability.
11.
Hydro-Québec, G2-RT-2004-01040-13, « Mise en œuvre du S-98 – Rapport d’étape », Février 2004
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Gentilly 2 Nuclear Generating Station Table 1: Comparison between S-98 and AP-913 objectives and requirements S-98 Objectives
AP-913 Objectives
Ensure that the RSS of the NPP can do function 1. reliably, in accordance with the relevant design, performance, and safety criteria, including the safety targets of the plant and CNSC license 2. requirements. 3.
4. S-98 Requirements of the RP (link with AP-913) 1. 2. 3. 4.
5.
6.
7.
8.
9.
Identify and rank RSS (a, b) Specify Reliability targets of the RSS (a, b) Identify and describe the potential failure modes of the RSS (d) Specify the minimum capabilities and performance levels that the RSS of the NPP must attain to achieve reliabilities that are consistent with the safety targets of the NPP and the regulatory requirements (e) Include provisions for maintaining the effectiveness of the Risk-Significant Systems of the NPP (1, 2, 3, 4, f, g, h) Provide for modelling, surveillance, monitoring and other activities of the RSS to ensure and survey their performance (1, c, i) Include provisions to assure, verify and demonstrate that the program is implemented effectively in accordance with the safety objective (2, 3, 4, c, i, h, j, k) Include provisions for recording and reporting the results of program activities including assessments, tests, inspections of the reliability of the RSS (c, d, h) Document, clearly and comprehensively, the activities, attributes, elements, results and administration of the program (c, d, h).
The process is efficient, incorporates human factor considerations, and ensures effective performance during all phases of plant operations. A uniform process is used among all plants in an organization. Applicable in-house and industry lessons learned are incorporated into the process to improve adequacy and efficiency. Changes to the process are timely, responsive to user feedback, and implemented at all affected plants. AP-913 Equipment performance objectives
a) Equipment performs reliably through the operating cycle, and standby safety equipment operates properly on demand. Equipment is capable of satisfactory performance under all design conditions. b) Critical equipment is identified based on importance to safety function, safe shutdown capability, and power generation capability. Insight from probabilistic assessment techniques is considered in this determination. c) Equipment and system performance criteria are established, performance is monitored, adverse trends are identified, and corrective actions are implemented and verified for effectiveness. d) Failures and failure causes of concern are identified for critical equipment, and measures are established to prevent them. e) The need for in-depth analysis of equipment failure is commensurate with the equipment’s importance to plant safety and reliability and the likelihood of recurrence. f) Preventive maintenance technologies are implemented to detect equipment degradation well in advance of potential failure and to optimize equipment performance. g) Equipment aging is managed using preventive maintenance techniques and life-cycle management, including mitigation of environmental stressors (such as temperature, radiation, and moisture) or operating stressors (such as duty cycles and vibration). h) Documented technical bases exist for preventive maintenance activities and aging management programs. i) Equipment performance data and associated trend information are uniformly collected and are readily accessible to support the prompt identification of problems and root causes. j) Equipment unavailability associated with preventive maintenance activities is balanced by the resulting improved equipment reliability and availability from prevented failures. k) Minimal in-service failures of critical equipment occur between scheduled maintenance intervals.
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Gentilly 2 Nuclear Generating Station
Table 2: Necessary activities to conform G-2 Reliability Program to S-98 Requirements Head Activity
Detailed Activities Bibliographical Search with regard to methods for determining Risk Identification of Risk Significant Systems (RSS) Significant Systems 2. Define the methodology for determining RSS 3. Develop a software support to the above methodology 4. Produce a list of the RSS 5. Define Reliability Targets of the RSS Activities would be coordinated with AP-913 activities in this area Verify if current reliability models meet S-98 Reliability Modeling Reliability Assessment and Requirements. Elements to consider: Reliability Modeling 1. Site component reliability data 2. System FT Modeling Considerations without a specific PRA i. Safety Design Matrices ii. Generic PRAs iii. PRA’s from other CANDU plants iv. Relevant Safety or Engineering Studies v. Safety Report vi. Other appropriate methods and assessmentsHuman Interactions 3. Software Reliability 4. Mission Failures 5. Hostile Environment 6. Common Cause Failures (Functional, Physical, and Human Interaction Dependencies) 7. Residual CCF. These activities coincide with AP-913 Equipment Reliability Process. The Surveillance Preventive Maintenance, Surveillance Testing and Inspections would be based on this approach. They correspond on requirements described in points 2.16 to 2.25 of G-98 Application Guide [5]. Monitoring of the RSS should consider: Monitoring of RSS 1. Performance Measures 2. System FT Modeling Considerations 3. Other FT Modeling Considerations i. Human Interactions ii. Software Reliability iii. Mission Reliability iv. Hostile Environment 4. Component Failure Data 5. Other FT Modeling Issues 1.
Reporting
Reliability Program/Documentation
Realization of a Reliability Database is necessary to achieve these requirements. Activities would be coordinated with AP-913 activities in this area. The activities in this field will focus on some elements: 1. Improve the form and the content of quarterly and annual reports 2. Modify the list of the followed systems (in accordance of the RSS list) 3. Add a trending of reliability data (a reliability database necessary) Document the Reliability Program, revise existing documents, activities and records (Reliability Program); develop new documents and records if necessary.
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