Nuclear Executive Update

Transcription

1 Nuclear Executive Update An EPRI Progress Report November 2007 The Nuclear Executive Update is published bi-monthly. If you have comments about the newsletter, please contact Brian Schimmoller, As most of you have heard by now, Dave Modeen is stepping down as CNO and vice president of EPRI s nuclear power sector to spend more time with his family as they deal with a serious health issue. To the industry and the EPRI team s benefit, however, Dave will remain with EPRI as Director, Industry Affairs, reporting directly to me. I want to formally recognize Dave for his contributions to the industry and to EPRI, and personally thank him for his assistance during my transition. Moving forward, I look forward to engaging each of you to understand your individual perspectives on EPRI, our mission, and the role of a strategic R&D portfolio that balances long-term and short-term industry needs and that leverages our broadening international engagement. I will be relying on your feedback and input as a part of my transition and look forward to getting reacquainted with the nuclear power industry. Two key contributors to the EPRI Nuclear Power Council should be recognized. Former Nuclear Power Council representative Lou Long and current Nuclear Power Council Chairman Mano Nazar received Nuclear Excellence Awards at the 2007 WANO conference in September. Lou, retired Southern Nuclear Operating Company executive, received his award in recognition of his vision and passionate pursuit of excellence in support of international nuclear fuel reliability, as well as for his leadership of dry fuel storage initiatives and nuclear revival activities. Lou has served in many EPRI programs, including more recently as chairman of the Fuel Reliability Executive Committee and the Plant Deployment Action Plan Working Group. Mano, former CNO of American Electric Power and newly installed COO of FPL s nuclear fleet, received his award in recognition of his dedication and strong commitment to promoting and achieving high safety standards, as well as for his leadership of recovery-to-excellence efforts at several nuclear power plants. On behalf of EPRI, I want to acknowledge these significant accomplishments and express our appreciation for both Lou and Mano s contributions and commitment to the EPRI mission. I m especially proud of the recognition EPRI received at the NSIAC meeting on November 7. The CNOs of the nine nuclear plants that faced accelerated 2007 inspections to examine pressurizer welds presented EPRI Program Manager Christine King and Senior Project Manager Craig Harrington with a plaque expressing the industry s appreciation for EPRI s technical contributions. The plaque commended EPRI and its industry partners for identifying the complex modeling and analysis needed to allow these plants to continue safe operation, and for saving 10.5 GWe of nuclear production during a high-demand period. King and Harrington were two of the six recipients of the award; others were Glenn White, Dominion Engineering Inc.; Cameron Martin, Westinghouse; Terry McAlister, SCANA Corp.; and Guy DeBoo, Exelon. We are continuing to focus on ensuring technology transfer occurs across all of our programs. One recent example is an EPRI training course designed to accelerate the process of converting seasoned nuclear engineers into capable risk management professionals. Through a series of one-week sessions over as little as nine months, this course will enable an engineer to competently perform Level 1 probabilistic risk Nuclear Executive Update: 1

2 assessments. Other recent examples include a concerted effort to engage with our international members to explore reliability aspects unique to Asian nuclear plant operation. Through activities like these, we are continuing to develop research plans with the end application in mind. Sincerely, Chris Larsen Vice President and Chief Nuclear Officer, EPRI Nuclear Sector TECHNICAL HIGHLIGHTS NRC Approves EPRI Pressurizer Weld Crack Growth Analysis, Maintaining Spring Outage Schedule for Nine PWRs By demonstrating that accelerated inspection outages were not necessary, EPRI saved the industry more than $400 million in lost revenues. Weld reliability concerns discovered at the Wolf Creek nuclear power plant in late 2006 set in motion a series of events that enabled EPRI s Materials Reliability Program (MRP) to convince regulators that accelerated inspection schedules were not necessary, saving the industry hundreds of millions of dollars in lost revenues. The October 2006 pre-weld overlay inspections at Wolf Creek using ultrasonic testing (UT) techniques identified five circumferential indications in the surge, relief, and safety nozzle-to-safe-end dissimilar metal (DM) butt welds. During public meetings with the MRP in Fall 2006, the Nuclear Regulatory Commission (NRC) presented the results of a fracture mechanics-based scoping study that assessed the safety significance of the UT indications. From these analyses, NRC staff concluded that there may be little or no time margin between the onset of leakage and rupture in pressurizer nozzle DM butt welds containing flaws similar to those found at Wolf Creek. In March 2007, the NRC issued Confirmatory Action Letters (CALs) to licensees of 40 pressurized water reactor (PWR) nuclear power plants, confirming commitments from those licensees to resolve concerns regarding potential flaws in specific reactor coolant system DM butt welds by the end of The remaining 29 PWRs in the U.S. PWR fleet had either already completed the requisite actions or did not have welds susceptible to these flaws. Of the 40 plants receiving CALs, nine were at risk because they did not have outages scheduled in These plants committed to accelerate outages into 2007 if EPRI MRP could not demonstrate an adequate level of safety to the NRC. MRP performed finite element analyses to determine if the indications would show detectable leakage prior to structural failure given the Pressurizer Top Head Nozzle potential concern for growing circumferential stress corrosion cracks. The finite element analysis reconsidered the typical assumption of maintaining a semi-elliptical flaw shape as the flaw grows. In the MRP analysis, the crack was allowed to grow at each point along the crack front to the degree dictated by the local stress conditions, producing an evolving crack shape as the crack penetrates through the pipe wall. The results demonstrated that the semi-elliptical flaw shape assumption was overly conservative and that a realistic crack would locally penetrate the pipe wall, producing leakage without resulting in total pipe failure. Nuclear Executive Update: 2

3 MRP analyzed a sensitivity matrix of 119 cases to assess the effect of specific input parameters on the mechanical behavior of the nozzle-to-safe-end DM weld. Parameters evaluated included weld residual stress profile, nozzle dimensions and geometry, initial crack shape, initial crack dimensions, operational loads, primary water stress corrosion crack growth rates, multiple initial cracks, and the effects of plastic redistribution of forces. Safety/relief, spray, and surge nozzles were all addressed in the sensitivity cases. Separately, the NRC staff performed an independent evaluation on 31 cases to either validate the industry results or to further evaluate the effects of certain parameters on the results. The sensitivity studies indicated that the results are highly dependent upon the DM weld residual stress profile and the initially assumed flaw characteristics, with the results being most sensitive to changes in the DM weld residual stress profile. By evaluating many cases and the associated sensitivities, MRP showed that the plants could meet the criteria of reasonable assurance of safe operation until On August 23, 2007, the NRC notified the nine PWR licensees that an accelerated schedule would not be required to address potential pressurizer pipe weld cracking, enabling the affected utilities to maintain their scheduled spring 2008 plant outages. By demonstrating that the shutdowns were unnecessary, the MRP saved each utility from a 28-day unplanned shutdown in 2007, resulting in aggregate savings (lost revenue) of more than $400 million. This project demonstrates how well MRP can work with NRC to support both NRC and industry when faced with difficult aging degradation issues at operating nuclear power plants. For more information, contact Christine King at or cking@epri.com. First Class of Risk Professionals on Path to Graduation by Mid-2008 The 18 students participating in EPRI s Education of Risk Professionals program will be qualified to perform independent work on Level 1 probabilistic risk assessments. Anticipated expansion of the nuclear industry, coupled with normal workforce attrition, has resulted in a shortage of trained nuclear risk professionals. To address this issue, EPRI has developed a series of training courses designed to develop the next generation of risk professionals. The Education of Risk Professionals program will qualify participants for independent work on Level 1 probabilistic risk assessments (PRA), particularly when combined with utility mentoring programs (see EPRI Report , Development of PRA Qualification Guidance and Curriculum ). Eighteen students are on schedule to complete the course by mid The program consists of six one-week training sessions that focus on fundamental and practical aspects of performing a PRA, coordinated with EPRI-sponsored applications-based training, such as the Risk & Reliability Workstation. The training materials comply with the Institute of Nuclear Power Operations systematic training approach and include testing and practical exercises to ensure comprehension of the material presented. During the first training module, which forms the foundation for the remaining five courses, the class develops a simplified PRA for a hypothetical but realistic nuclear plant, EPRI Nuclear One (ENO). The ENO case study provides the students with perspective on both the scope and depth of a PRA. The students experience how large and complicated a PRA can be, but also how the various PRA elements relate to each other and to the final PRA. The ENO PRA is used in each of the succeeding modules as the starting point for discussing specific PRA elements. After finishing all six training modules, the students will have completed a fully functional PRA for the simplified ENO, as well as several sample risk-informed applications, such as Maintenance Rule a[4]. The Education of Risk Professionals program has exceeded initial expectations, especially considering that the original schedule targeted an 18-month training program cycle. With additional resources provided through the Nuclear Sector s Key Change Initiative process, accelerated program development will enable the first class to graduate in just nine months. As of early November 2007, 18 students had completed the first two training modules. A third session is planned for December, and EPRI will deliver the remaining three training modules in the first half of The next class of risk professionals will commence in September of Nuclear Executive Update: 3

4 For more information on the Education of Risk Professionals program, contact Frank Rahn at or Education of Risk Professionals, Program Outline Module Course Elements 1 Risk basics, basic PRA concepts, simplified PRA development 2 System modeling, using PRA software 3 Initiating events, success criteria, accident sequences 4 Data analysis, human reliability analysis 5 Quantification, PRA software, internal flooding 6 Large early release frequency (LERF) analysis, PRA results interpretation, PRA applications Japanese Equipment Reliability Forum Advances EPRI International Engagement To fully leverage the global nature of nuclear power, the Equipment Reliability Action Plan is engaging international utilities through a series of technical forums. Extracting maximum value from EPRI membership depends on frequent and concerted engagement to understand available products and services, and to influence future research and development of these products and services. This engagement model is proven and successful, but execution is considerably more difficult for non-u.s. members because of language barriers, time zone differences, and physical separation. The Equipment Reliability Action Plan is attempting to break down some of those barriers through report translations, more frequent in-country visits, and active member engagement. In late October, an EPRI Equipment Reliability (ER) team visited Japan to advance these efforts. During the one-week visit, the team - comprising Neil Wilmshurst, Equipment Reliability Manager; Alan Grunsky, Nuclear Steam Turbine Initiative Manager; Marty Bridges, Nuclear Maintenance Applications Center Manager; and Ken Barry, Manager of Nuclear Technology Transfer - facilitated a two-day ER Forum attended by all Japanese nuclear utilities. The team then participated in focused ER workshops with the two Japanese full EPRI nuclear sector members, Tokyo Electric Power Company and Chubu Electric Power Company. Meeting objectives included: Expanding awareness of the ER research portfolio. Aligning Japanese utility issues and priorities with existing ER products and capabilities. Soliciting input into the advisory process on new product development needs. Engaging Japanese members in project execution, i.e., leveraging Japanese expertise, knowledge and experiences to benefit the broader global nuclear community. The team identified several action items from the meetings: Full translation of a small number of existing documents to support broader understanding and application of EPRI products in addressing key issues. A prioritized list of candidate reports is being developed to support this effort. Establishing close contacts between EPRI technical experts and Japanese utility staff to address specific issues identified during the workshop. Expanding workshops and user groups within Japan to facilitate greater collaboration between utilities and with EPRI. Advancing new project ideas within the EPRI ER advisory process to reflect Japanese experience and expertise. Nuclear Executive Update: 4

5 These actions will be supported by regular interactions to track progress and strengthen relationships. A similar series of meetings is currently being considered for Europe in For more information about the ER Forums, contact Neil Wilmshurst at or nwilmshu@epri.com. KKM Applies Online Noble Metal Chemical Addition to Mitigate Intergranular Stress Corrosion Cracking On-line noble metal chemical addition (NMCA) can save 60 hours of critical path time as compared to classic NMCA. With funding and technical support from EPRI s BWR Vessels and Internals Program (BWRVIP) and General Electric, the Swiss utility Kernkraftwerk Mühleberg (KKM) launched a demonstration project in 2005 to gather information supporting commercial application of online NMCA (OLNC). OLNC is an upgraded version of the classic NMCA technology that GE developed with EPRI support in the mid-1990s to mitigate intergranular stress corrosion cracking (IGSCC). Results from three years of operation with OLNC at KKM are encouraging and support broader implementation. Questions about the effectiveness of classic NMCA arose after KKM used NMCA to mitigate IGSCC in the reactor core shroud. Subsequent inspection revealed that the cracks continued to grow at the same rate as before the noble metal injection. GE theorized that if a plant stops injecting hydrogen after noble metal injection, cracks will continue to grow in depth and length as if unmitigated. Moreover, the cracks will continue growing even after hydrogen injection is resumed because the newly grown surfaces of the cracks are not coated with noble metal. At this stage, injecting yet more noble metal raises concerns about NMCA s potential effects on fuel performance. Although there is no evidence that NMCA contributes to fuel failures, researchers are concerned the process may cause tenacious crud deposits that could accelerate corrosion of the fuel rod exteriors. Unlike the classic NMCA technology - which injects large batches of platinum and rhodium at six-year intervals and impacts critical path - the online approach involves injecting small quantities of platinum only into the feedwater piping loops on a routine basis during normal operation. As a result, OLNC offers the flexibility to add small amounts of noble metal after periods of off-hydrogen operation to coat the new crack surfaces and mitigate crack growth. The demonstration at KKM is providing favorable results. Core shroud inspections of indications showed that some crack growth rates are slowing down. Fuel surveillance supported by EPRI s Fuel Reliability Program indicated that overall fuel performance is excellent, and there is no apparent adverse impact of OLNC on the fuel. As a result of KKM s leadership role in successfully demonstrating OLNC, two American BWRs - Constellation s Nile Mile Point and Exelon s Peach Bottom - have applied the technology in their reactors. Online NMCA offers several advantages over classic NMCA for IGSCC mitigation: Saves 60 critical path hours - 12 for unit shutdown and 48 to apply noble metal Mitigates crack growth subsequent to off-hydrogen operation Increases flexibility and efficiency of noble metal injection Reduces total noble metal loading For more information about NMCA, contact Randy Stark at or rstark@epri.com. NRC Approves Use of EPRI s Streamlined RI-ISI Methodology Recent pilot demonstrations of EPRI s risk-informed/safety-based in-service inspection approach, known as RIS_B, show that nuclear plant operators can reduce the number of piping examinations and cut overall inspection program costs. Industry concern over potential cracking in dissimilar welds has focused attention on the importance of diligent inspection and nondestructive evaluation practices. In the wake of events such as the Duane Arnold dissimilar Nuclear Executive Update: 5

6 metal weld indications (see March Nuclear Executive Update), utilities are taking informed early action to prevent problem escalation. For regulatory and economic reasons, more and more nuclear power plants are deploying risk-informed in-service inspection (RI-ISI) programs to guide inspection and maintenance scheduling. The EPRI Nondestructive Evaluation Program has long supported the development and use of RI-ISI - more than 70 percent of U.S. nuclear plants implementing RI-ISI are using EPRI-developed RI-ISI products. To drive continuous improvement, EPRI has developed a streamlined RI-ISI methodology known as riskinformed/safety-based ISI, or RIS_B. The benefits of this new approach are that the risk-informed technology can be applied and maintained more cost effectively, and can be applied to the whole plant (i.e., a full-scope application). To confirm the functionality and robustness of the RIS_B methodology, EPRI conducted pilot demonstrations in 2006/2007 at two plants currently using the deterministic ASME Section XI inspection guidelines: one at Entergy Nuclear s Grand Gulf Plant, a boiling water reactor; and one at American Electric Power s DC Cook Nuclear Plant, a two-unit pressurized water reactor. Working with EPRI, the utilities submitted pilot plant applications to the U.S. Nuclear Regulatory Commission (NRC), participated in meetings with NRC, and responded to requests for additional information (RAIs). NRC approved the Grand Gulf application on September 21, 2007, and the DC Cook application on September 28, By applying the RIS_B methodology, Grand Gulf and DC Cook have reduced the number of required Class 1 and Class 2 piping examinations by 65 percent and 70 percent, respectively, resulting in significant cost, worker exposure, and radwaste savings that will continue throughout the plant lifetime. Additionally, the RIS_B methodology provides the flexibility to alter inspection locations to reduce dose, to avoid relief requests that are often required with deterministic inspection programs, and to consolidate scaffolding. Plant resources required to maintain this program going forward are less than those for traditional RI-ISI approaches. Both sites are now better able to focus resources on the more important plant areas from a safety and reliability perspective. Entergy and AEP s leadership in championing the EPRI RIS_B methodology has led to a more consistent and coherent use of this risk-informed technology. In addition to NRC acceptance, ASME has accepted RI-ISI as an approved risk-informed technology, and many EPRI nuclear members have expressed interest in transitioning from existing inspection programs to the EPRI RIS_B approach. This includes plants that have not previously developed an RI-ISI program, as well as plants that have already implemented traditional RI-ISI programs, but wish to adopt a more stable and focused approach. For more information, contact Pat O Regan at or poregan@epri.com. Cost-Benefit Comparison for RIS_B Current Use of RI-ISI Technology No RI-ISI application Class 1 only Class 1 and 2 Full-scope, Class 1/2/3 traditional RI-ISI application Benefits from Implementing RIS_B Cost Value Significantly reduced Class 1 and 2 piping costs, worker exposure and radwaste. Fewer inspections relative to existing Class 1 program; extension to Class 2 much less costly than for traditional RI-ISI approached. Fewer inspections relative to existing program; lower long-term program costs. Fewer inspections relative to existing program; lower long-term program costs. Nuclear Executive Update: 6

7 End-of-Life Equipment Guides Inform Long-Term Planning Process Guidance on component aging enables nuclear plant to make informed decisions about whether and when to replace capital-intensive components such as transformers and main generators. As plants age, large balance-of-plant components are more likely to fail. Additionally, through license renewal, many key components could be operated well beyond their original expected life. Guidance on component aging is needed to assist plant staffs in making long-term, often capital-intensive decisions about whether and when to replace these components. EPRI has launched an initiative to develop such end-of-life guides for critical balance-of-plant equipment, including transformers, main generators, large electric motors, and switchyard equipment. Each component guidance document focuses on end-of-life failure mechanisms, assuming normal preventive maintenance is performed. The guides discuss condition monitoring methods, specific indicators of advanced aging, environmental and operational stressors that may accelerate or mitigate aging, and typical lead times associated with obtaining a replacement component. The reports also address the point at which long-term aging can result in catastrophic component failure, and the associated indicators. Each report examines logistics related to component replacement and the typical amount of time required for replacement under various scenarios. A summary excerpt from the transformer guide is provided in the accompanying table. Other components of the transformer are addressed in the same manner, alerting plant staff to critical indicators and pointing out when heightened condition monitoring, maintenance, refurbishment, or replacement would be prudent. End-of-life guides have been completed for large transformers and main generators; guides for large electric motors and switchyard equipment are under development. Other topics under consideration include buried pipe and cable. For more information, please contact Rick Easterling at or rneaster@epri.com. Component Failure mechanism Degradation/influence Needed PMs Expected life Time to failure Diagnostic methods Diagnostic effectiveness Ease of repair Time to repair Repair issues Time to replace Solid bushing Insulation failure Chipped or cracked porcelain Inspect and clean external surfaces; replace if chipped or cracked or unacceptable power factor test >15 years If externally contaminated, may fail quickly, especially in wet conditions; internal issue may worsen rapidly External visual for contamination; power factor testing Techniques are effective and well established If deteriorated or failed, likely to be replaceable. If failure induces internal fault, low likelihood of repair. Days to a week N/A N/A Nuclear Executive Update: 7

8 EPRI Groundwater Protection Guidelines Reduce Site Liabilities The guidelines, available in December, will examine the elements of an effective utility groundwater management program. Implementing utility groundwater monitoring programs, as required by the recent NSIAC (Nuclear Strategic Issues Advisory Committee) initiative, can be a challenging and costly task. Through the EPRI Groundwater Protection Guidelines, which will be available by December, nuclear operators can deploy technically sound, cost-effective groundwater protection programs, leading to improved public confidence and reduced regulatory liabilities. The guidelines document details the elements of an effective utility baseline groundwater management program, while providing the flexibility of a risk-based graded approach for sites requiring more active investigations. A team of EPRI experts developed the technical basis for the guidelines from existing EPRI documents, and a panel of technical representatives from nuclear utilities, the Nuclear Energy Institute, American Nuclear Insurers, and nuclear vendors reviewed the guidelines to ensure they were highly practicable. The guidelines include specific program details on monitoring well installation, site conceptual model development, and data management. Insight and expertise from Duke Energy, Ontario Power Generation, and Progress Energy provided recommendations for how to evaluate structures, systems and components that have the potential to leak. The resulting Priority Index, as shown in the accompanying table, enables operators to deploy a more preventive, cost-effective program in the long term. Through such risk-based calculations, utilities can focus on mitigating failures that could otherwise lead to undesirable consequences, including off-site contaminant migration. Potential Factors in Assessing Failure Consequences Failure Effect Inventory Hazard Mobility Post-Release Detection Priority Index Already leaked to ground Leak into soil Low level, flow into ground Implementing the EPRI Groundwater Protection Guidelines will require a significant utility resource commitment, but the avoided costs are much higher. Estimates from the utility committee advising EPRI on the guidelines development process suggest implementation costs of $0.5-$1.3 million per site, with an ongoing annual cost of $25,000-$190,000. This can be contrasted to estimates of $30-$75 million for sites that have not implemented groundwater protection programs, and have had to implement expensive remediation actions. Additional technical work is in progress to further reduce these liabilities through collaborative development of software and remediation tools with the EPRI Environment Sector, and with the Material and NDE Programs in the Nuclear Sector. An EPRI site assistance team is engaged with several nuclear members to implement the guidelines using supplemental funding. For more information, contact Sean Bushart at or sbushart@epri.com. Together...Shaping the Future of Electricity EPRI 3420 HILLVIEW AVENUE PALO ALTO, CA Electric Power Research Institute, Inc All rights reserved Nuclear Executive Update: 8