Nuclear Executive Update

Transcription

1 Nuclear Executive Update An EPRI Progress Report May 2009 The Nuclear Executive Update is published bi-monthly. If you have comments about the newsletter, please contact Brian Schimmoller, The uncertain future of the proposed Yucca Mountain geologic repository in the United States complicates what was already a complicated and contentious issue impacting the nuclear power industry. What remains unchanged, however, is the fact that used fuel and high-level waste will require long-term storage and ultimate disposal. This certainty, of course, is not restricted to the United States; the need for storage and disposal extends to all countries with operating or planned nuclear power plants. EPRI research into used fuel and high-level waste has shifted in the past year from a strong emphasis on providing independent technical assessment of the ability of Yucca Mountain to safely store used nuclear fuel to one of addressing a more diverse array of handling, transportation, disposal, and fuel cycle issues. With expectations that nuclear power plants may be required to store used fuel on-site for 60 years or more, dry storage will likely be an essential foundation for continued operation of existing plants and construction of new plants. Recognizing this growing certainty, EPRI is launching a new effort to define and address technical barriers that may confront very long-term storage. EPRI is also continuing detailed analyses of high burnup fuels and their impact on used fuel storage and transportation. Renewed interest in nuclear power, bolstered by concerns about carbon emissions, has also renewed interest in nuclear fuel reprocessing and recycling. While used fuel is reprocessed in some countries, it is not in others for various economic and geopolitical reasons. Changing technical, economic, and political realities, however, call for periodic re-evaluation of such decisions. Toward this end, EPRI supports both internal and external research to evaluate options for the back end of the fuel cycle and to identify benefits, challenges, and R&D needs. For more details on one EPRI-supported external analytical effort being led by the Massachusetts Institute of Technology, see the lead article in this newsletter. Because used fuel and high-level waste management issues impact all nuclear plants regardless of design, EPRI will continue engaging the industry along with various regulatory and global research entities to pursue cross-cutting research of broad benefit. If you would like more information about our used fuel management program, please contact John Kessler, program manager, at or jkessler@epri.com. Sincerely, Chris Larsen Vice President and Chief Nuclear Officer, EPRI Nuclear Sector Nuclear Executive Update: 1

2 MIT Report Examines Future of Nuclear Power The interim report updates MIT s 2003 study and provides context for a multi-year investigation into the back end of the fuel cycle. In mid-may, the MIT Energy Initiative released an interim report updating its 2003 study, the Future of Nuclear Power. The document reviews what has changed since 2003 with respect to the challenges preventing nuclear power from becoming a viable U.S. marketplace option at a time and at a scale that could play a significant role in mitigating climate-change risks. The interim report also provides context for an ongoing multi-year analysis of the nuclear fuel cycle being supported by EPRI and the Nuclear Energy Institute. The 2003 MIT study recommended government and industry actions that could enable nuclear power to expand its role in electricity supply and climate-change risk mitigation. The study addressed nuclear reactor and fuel cycle technologies and economics; safety; waste management; proliferation risks associated with global fuel cycle deployment; technology research, development and demonstration (RD&D) needs; and public attitudes in the United States. Developments over the past six years, both positive and The sober warning is that if more negative, have raised even more complex technological and is not done, nuclear power will policy challenges concerning the pros and cons of alternative diminish as a practical and timely nuclear fuel cycle strategies and their readiness for resolving near-term policies associated with used fuel management. option for deployment at a scale These considerations led EPRI and NEI to support an update that would constitute a material to the 2003 MIT report. Over the next several years, MIT contribution to climate change researchers will conduct various studies related to the same risk mitigation. core question addressed in the 2003 study: What actions are Excerpt from MIT Report needed to enable nuclear power to be an important contributor to electricity supply in a carbon-constrained world for the long term? The overwhelming research emphasis for the updated study, however, will be on the back end of the fuel cycle, both open and closed configurations. The interim report notes that concerns about the adverse consequences of climate change have increased significantly in the past five years. To move toward lowcarbon electricity generation, greater emphasis on nuclear power, fossil fuel use accompanied by carbon dioxide capture and sequestration, and renewable energy technologies will be needed, as captured in EPRI s PRISM analysis (see report numbers and ). With respect to nuclear power, new plant deployment since 2003 has been slow both in the United States and globally, particularly in relation to the illustrative scenario examined in the 2003 report, which projected an increase from 100 GWe to 300 GWe in the United States by 2050 and from 340 GWe to 1000 GWe globally. In the United States, no new nuclear units have begun construction since the 2003 report. Compared to 2003, the interim report concludes, the motivation to make more use of nuclear power is greater, and more rapid progress is needed in enabling the option of nuclear power expansion to play a role in meeting the global warming challenge. The sober warning is that if more is not done, nuclear power will diminish as a practical and timely option for deployment at a scale that would constitute a material contribution to climate-change risk mitigation. A comprehensive version of the updated report, to be published later this year, will present the MIT team s major findings and a preliminary set of RD&D recommendations related to uranium resources, nuclear power and fuel cycles economics, interim storage of used nuclear fuel, waste management, fuel cycle system dynamic modeling and analyses, non-proliferation impacts, fuel cycle decision analysis, and RD&D strategies. For more information, contact Albert Machiels at or amachiel@epri.com. Nuclear Executive Update: 2

3 EPRI Spearheads Industry Action to Resolve BWR Fuel Channel Distortion Issues Together with nuclear utilities and fuel vendors, EPRI is developing a comprehensive industry plan to identify operational impacts related to channel distortion and formulate near-term mitigation guidance. Seventeen of the 35 boiling water reactors in the United States have reported control blade interference due to channel distortion in the last eight years. To reduce risk exposure related to channel distortion, EPRI s Fuel Reliability Program is leading industry efforts to develop an action plan to examine distortion mechanisms, develop improved distortion models, and validate proposed materials solutions. Channel distortion events at operating nuclear reactors can have significant impacts. One U.S. plant had to declare a site area emergency when a number of control blades did not fully insert due to channel distortion on a low pressure reactor trip. Interestingly, few international member utilities have observed interference, a fact attributed to core design differences for longer fuel cycle lengths in the United States (18-24 months). Affected fuel designs include Zircaloy-2 channels manufactured by GNF, AREVA, and Westinghouse. and bow that impart a slight axial rotation to the channel. Channel interference depends on many factors, including core design, cycle length, channel design, materials and operating environment. Channel distortion typically manifests itself as bulge, bow, or twist, which act to close the nominal control blade-channel gap. Bulge, which is caused by irradiation creep of the channel due to the differential coolant pressure across its wall, is predominantly found at lower elevations. Bow is caused by a differential length change on opposite sides of the channel, usually caused by irradiation growth, absorption of hydrogen during the corrosion process (either uniform corrosion or shadow corrosion ), or stress relaxation. Twist results from small geometric differences in bulge To more effectively coordinate industry efforts on channel distortion, the nuclear fuel vendors, utilities, the Institute of Nuclear Power Operations, and EPRI committed to developing a Channel Distortion Industry Action Plan (CDIAP). The CDIAP defines a strategy to address channel distortion based on detailed understanding of each channel distortion mechanism at the scientific (or mechanistic) level. Goals include: Update guidance to effectively manage channel distortion until more effective solutions are available Collect and analyze channel performance data from operational performance, poolside dimensional measurements, and hot cell examinations Develop a mechanistic understanding of channel distortion and identify gaps in such understanding Identify and conduct additional examinations to quantify each distortion mechanism Develop improved distortion models that can sufficiently predict channel distortion Incorporate models into fuel vendor channel management tools and validate their performance via examination and surveillance Validate proposed materials solutions The CDIAP strategy involves formalizing the ad-hoc, industry-led Channel Distortion Team within the Fuel Reliability Program with a dedicated funding source and sufficient staffing. The Channel Distortion Team would be responsible for developing and disseminating guidance for near-term management and mitigation Nuclear Executive Update: 3

4 of channel distortion. The CDIAP has multiple phases to address both near- and long-term activities through organization, guidance, information gathering, surveillance and research. Key deliverables include guidance to mitigate operational issues and improved channel distortion models that can be incorporated into fuel vendor channel management tools to allow BWRs to operate without interference between channels and control blades. For more information, contact Erik Mader at or EPRI Continues Comprehensive Effort to Support Cost-Effective Buried Pipe Management Through technical guidance, risk-ranking software, repair options, inspection techniques, and collection of operating experience, EPRI is developing the tools to effectively manage buried pipe. The health of buried piping continues to be a key issue for nuclear power plants. Issues include potential tritium leakage into groundwater, cost of mitigating leaks and damage, and plant downtime associated with repairs and replacements. The May 2008 edition of this newsletter described efforts underway at that time to develop the tools and technology to manage this issue. Although much work remains, significant progress has been made on a variety of fronts: Buried Pipe Integrity Group (BPIG). Through the Balance-of-Plant Corrosion Program, EPRI formed BPIG in 2008 to provide a forum for experience sharing, training, standards development, and technology development related to the degradation of buried pipe. Two meetings in 2008 and one meeting to date in 2009 have been well-attended and well-received. The next meeting will be the week of July 13, 2009 in Denver, CO. Programmatic Recommendations. Prior to 2008, the industry and the regulatory community lacked technical guidance regarding effective buried pipe management. In 2008, EPRI, with support and input from BPIG and the Institute of Nuclear Power Operations, developed a set of recommendations for managing a buried pipe program (Product No ). These recommendations constitute a living document that will be periodically updated as experience and technology advance. Risk-Ranking Software: BPWORKS. The inspection of buried pipe, whether by digging or other means, is disruptive and expensive, often costing more than $100,000 per excavation. Because nuclear plants contain up to 30 buried pipe systems, with each exposed to tens of different burial and operating environments, risk ranking can help plant owners prioritize where to inspect. In 2008, EPRI released the BPWORKS software (current version is Product No ) to conduct risk rankings of buried pipe. This software is based on predictive models of degradation that can be initiated from either the soil side or the fluid side, as well as the development of occlusions that can impede flow. High-Density Polyethylene Pipe (HDPE). For pipe that needs to be repaired, one option is the use of HDPE as either a liner or as a complete replacement. HDPE has been used in non-safety service water systems in nuclear plants, and in similar applications in other industries, with favorable results. Although HDPE material costs are approximately the same as those for carbon steel, installation labor costs are only a fraction of those of metal pipe. EPRI has been supporting the development and regulatory approval of ASME Code Case N-755 to allow HDPE to be used in buried Class 3 service water systems. Support has included testing to determine the engineering and material properties needed to design piping systems, investigation of inspection technologies, development of Code rules, and development of repair technologies for HDPE components that become damaged during installation or use. This work supported Nuclear Executive Update: 4

5 successful efforts by two U.S. plants to receive regulatory approval in October 2008 for use of HDPE in Class 3 applications, and has also supported HDPE use in non-safety applications. Condition Assessment of Buried Pipe. In 2008, EPRI completed the development of a vehicle to inspect very large-diameter (36-inch to 12-inch) piping. The vehicle, which can be lowered through a 24-inchdiameter manhole, uses two electromagnetic processes for condition assessment: remote-field eddy current technology to identify and quantify internal or external pits down to ½-inch wide and 50% through-wall, and transmit-receive eddy current technology to identify degraded welds. The technology is now being offered commercially by Testex. In 2009, the technology is being extended to address intermediate-diameter buried pipe. Evaluation of Guided Wave and Other No-Dig Inspection Technologies. Guided wave ultrasonic technology is one of the no-dig options for assessing the condition of buried pipe. Because the method includes a variety of hardware and software to interrogate the pipe and evaluate the resulting data, commercial claims can be conflicting. EPRI is providing independent evaluation of the technology (Product No ), preparing guidelines for use, and performing research to extend the technology and evaluate other no-dig technologies. EPRI also offers training to support effective buried pipe management. A class for buried pipe program owners is scheduled for the week of June 1 in Charlotte, and a class on cathodic protection systems to manage buried pipe degradation will be offered later in the year. For more information, contact Shane Findlan at or sfindlan@epri.com. Gas Accumulation Issue Highlights Need for Improved Guidance and Detection Technology EPRI is developing guidance and evaluating detection techniques such as guided wave ultrasonics to ensure plant operability is not challenged by gas accumulation. Regulatory concerns regarding recent discoveries of gas accumulation have prompted industry efforts to identify and prevent such accumulation in susceptible nuclear plant systems. EPRI is developing guidance and evaluating detection techniques such as guided wave ultrasonics to ensure plant operability is not challenged by gas accumulation. Although activities evolved in response to a U.S. regulatory issue, other countries have begun investigating this issue, and the EPRI guidance and techniques are expected to be applicable worldwide. In January 2008, the U.S. Nuclear Regulatory Commission (NRC) issued Generic Letter , Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems. The Generic Letter requested that licensees evaluate susceptible systems to ensure that gas accumulation could be maintained less than the amount that challenges operability. U.S. nuclear plants provided detailed responses within the nine-month schedule, outlining plant experience and planned mitigation approaches. However, the industry recognized that research efforts focused on early detection and prevention were needed to fully resolve the issue. The Nuclear Energy Institute formed the Gas Accumulation Team, which consists of utility personnel and industry representatives from EPRI, the Institute of Nuclear Power Operations, GE Hitachi, and Westinghouse. The Gas Accumulation Team has convened three industry workshops to discuss system engineering evaluations and potential technical solutions. Bi-weekly conference calls maintain industry focus and ensure activities target both short-term and long-term solutions. EPRI s participation concentrates on longer-term solutions to gas detection and monitoring. Operating experience shows that the major sources of gas intrusion are from poor post-maintenance filling and venting practices, gas coming out of solution, and leakage from interconnecting systems. Nuclear Executive Update: 5

6 In summer 2008, EPRI s Nuclear Maintenance Application Center and Nondestructive Evaluation Center issued letter report LR Revision 1, providing guidance on the use of ultrasonics in locating and sizing gas voids in piping systems. The report focuses on horizontal and vertical pipe runs, sloped runs, tees and elbows, and also suggests methods for quantifying the amount of gas vented. The Nuclear Maintenance Application Center is also pursuing the development of guided wave ultrasonics for gas detection. Guided wave can monitor long runs of piping (20+ feet) while eliminating the need for scaffolding and reducing concerns about dose rates. EPRI conducted laboratory feasibility studies in 2008 on 2-inch and 4-inch piping segments and compared the results against field results from Plant Farley. The studies proved that guided wave can detect and quantify gas voids. Additional studies conducted in 1st quarter 2009 indicate system accuracy is within a range appropriate for use in a plant environment. Future 2009 work at EPRI s Charlotte facilities will evaluate guided wave technology using 6-inch and 8-inch mockups representing typical nuclear plant pipe runs. A second field study at Ginna Nuclear Station is tentatively scheduled for September. For more information on EPRI s involvement with gas intrusion, contact Nick Camilli at or ncamilli@epri.com. Modeling Efforts Target Updated Seismic Hazard Analysis EPRI is developing a new seismic source characterization model for the Central and Eastern United States that will provide a consistent, stable basis for conducting probabilistic seismic hazard analysis evaluations for regulatory activities. EPRI is leading research efforts to improve the understanding of seismic sources and their characterization in the Central and Eastern United States (CEUS). In conjunction with the U.S. Department of Energy and the U.S. Nuclear Regulatory Commission, EPRI s Advanced Nuclear Technology Program is developing a new Nuclear Executive Update: 6

7 seismic source characterization (SSC) model to incorporate technical advances made since the original model was created in The new model, scheduled to be completed by the end of 2010, will provide a consistent, stable basis for conducting probabilistic seismic hazard analysis evaluations for regulatory activities such as early site permits and combined operating license applications. Fundamentally, the model will provide the technical basis for assessing the seismic hazard levels in the CEUS. Seismic source models must adequately assess and incorporate uncertainties such as source geometry, maximum magnitude, and recurrence. For example, there is large uncertainty in the recurrence model because of different interpretations of paleoliquefaction data related to tectonic strain rates and recurrence rates. A key component of the SSC project, therefore, is to quantify these uncertainties and document their usage. The SSC project is being accomplished using the NRC-approved Senior Seismic Hazard Analysis Committee (SSHAC) process. This process calls for technical interaction at workshops among the project participants and members of the larger technical community; technical review of the preliminary CEUS SSC model; and review of the project s documentation and its compliance with the SSHAC process by a Participatory Peer Review Panel composed of experts from the industry, regulatory and government agencies, and academia. Further, to ensure the SSC model reflects input and guidance from a wide range of technical perspectives, EPRI is conducting a series of workshops. The second of three workshops was held at EPRI s Palo Alto offices in February. More than 60 attendees from industry, government and academia discussed and debated alternate viewpoints regarding key SSC issues; identified the technical bases for the alternate hypotheses; and discussed associated uncertainties. The workshop discussions will provide important input in developing the preliminary SSC model. For further information on this project, please contact Jeffrey Hamel at or jhamel@epri.com. NDE Requirements Accompany Mitigation Methods for Alloy 600 Cracking For newer mitigation methods such as optimized weld overlays, weld onlays, and weld inlays, EPRI is developing the technical basis for NDE inspection procedures and supporting Code activities. Each of the four mitigation methods available for addressing primary water stress corrosion cracking (PWSCC) in Alloy 600 materials exposed to the primary coolant water has nondestructive evaluation (NDE) requirements. For newer mitigation methods such as optimized weld overlays, weld onlays, and weld inlays, EPRI is developing the technical basis for NDE inspection procedures and supporting Code activities. The susceptibility and onset of PWSCC cracking for a particular component are influenced by temperature, pressure, material residual stresses, water chemistry, and service life. A weld s susceptibility to PWSCC, however, can be reduced using one of four different mitigation techniques, some of which also can serve to repair a weld that is already cracked. Mitigation can also reduce inspection requirements for the remaining life of the weld. The mechanical stress improvement process (MSIP) uses a clamp to plastically deform the pipe adjacent to the weld, leaving a residual compressive stress on the inside surface of the weld. Because the process can only be used if the weld is free of large cracks, the weld first must be examined using NDE. Therefore, MSIP is applicable only to inspectable weld configurations. MSIP is a mature application with fully qualified NDE available, and has been performed at many nuclear sites. Nuclear Executive Update: 7

8 The weld overlay process applies PSWCC-insusceptible weld metal to the outside of the pipe joint. A full structural weld overlay (FSWOL) is thick enough to fully replace the structural contribution of the original weld, rendering premitigation inspection unnecessary. Therefore, FSWOL may be used whether the original weld configuration is inspectable or not. An optimized weld overlay (OWOL) is thinner than an FSWOL because it takes credit for the strength of the uncracked part of the original weld. The benefit is that an OWOL can be applied faster, but it requires a pre-mitigation inspection and so is applicable only to inspectable configurations. With either type of overlay, the mitigated joint must be inspected, so inspectability of the final configuration is a key design parameter. FSWOLs have been in service in the BWR fleet since the 1980s and have been widely used in PWRs to mitigate PWSCC. OWOL has not yet been applied; its chief value is considered to be in mitigating PWR reactor coolant piping. Qualified NDE is available for most configurations, although the EPRIdeveloped OWOL inspection application has special criteria that are still under Code and regulatory review. The final two mitigations are applicable when access to the inside surface of the weld is available. The weld onlay process is similar to weld overlay, but is applied on the inside surface of the weld. Onlays provide an insusceptible barrier between the weld and the coolant, but do not provide a structural contribution. Because weld onlays reduce the flow cross-section, they are not always applicable. To preserve the flow cross-section, weld inlays can be considered in which susceptible material on the inside surface of the weld is machined away and insusceptible weld metal is installed in the cavity. Both onlay and inlay must be preceded by an inspection, and followed by machining to permit a post-mitigation inspection. One U.S. PWR recently performed a successful weld onlay on a 12-inch core flood pipe segment. Other PWR owners are evaluating this application for adaptation at their plants. The weld inlay process has not yet been applied in the field. EPRI has developed the technical basis demonstrating that the inspection procedures that have been qualified for non-mitigated joints are also effective after application of weld onlay or inlay. For more information, contact Greg Selby at or gselby@epri.com. Commercial Grade Item Dedication Guidance to be Endorsed by Nuclear Regulatory Commission ASME recognized EPRI s Joint Utility Task Group for its efforts in developing the guidance, which will be included in the 2009 Addenda to ASME s NQA-1 Standard and endorsed by the NRC. EPRI s Joint Utility Task Group (JUTG), together with the American Society of Mechanical Engineers Nuclear Quality Assurance Committee, developed criteria that will be included in the 2009 Addenda to ASME s NQA-1 Standard, and will subsequently be endorsed by the Nuclear Regulatory Commission. The NQA-1 Standard will be the baseline quality assurance requirement for all new nuclear construction in the United States, and is currently the baseline quality assurance standard used by more than 35% of the operating nuclear units in the United States. The NQA Addenda is scheduled for publication this summer. JUTG s involvement in this issue originated from a set of comments submitted to ASME expressing concern with the requirements proposed for commercial grade item dedication that coincided with ASME s plans to revise the standard. Recognizing the experience of the JUTG team members who submitted the original exceptions, the NQA-1 Committee worked with EPRI to assemble an industry task group composed of representatives from JUTG, the ASME Engineering and Procurement Processes Subcommittee, and the Nuclear Regulatory Commission. The task group was tasked with developing new language regarding commercial grade item dedication to be included in Subpart 2.14 of NQA-1, Quality Assurance Requirements Nuclear Executive Update: 8

9 for Commercial Grade Items and Services. The JUTG, managed through EPRI s Plant Support Engineering Program, is a procurement engineering community of practice that meets twice annually to discuss technical supply chain issues. Working to a compressed schedule, the team developed criteria that are not only consistent with existing federal regulations and EPRI guidance originally developed for licensees, but are also designed to meet the needs of manufacturers and non-commercial power sectors of the industry (such as the Department of Energy) that employ the NQA-1 Standard to ensure effective quality assurance. During the ASME NQA-1 Main Committee meeting in Cincinnati, Ohio on April 22, 2009, Rich Porco, Vice Chair of the ASME Board on Nuclear Codes and Standards, awarded certificates of acclamation to the members of the NQA Committee, the NRC, and JUTG involved in developing the guidance. Recipients included Frank Strehle of Progress Energy, William Ware of Southern Nuclear Operating Company, Tim Czuba of FirstEnergy, and Marc Tannenbaum of EPRI. In addition to the individuals recognized by ASME, JUTG members involved in developing the original comments included Bhavesh Patel of Progress Energy (then JUTG Chairman), Paul McBride of Duke Energy, Daryl Prisby of Exelon, and Rudy Yates of Dominion. To ensure continued consistency within the industry, two members of the task group have joined the NQA Committee. For more information, contact Marc Tannenbaum at or mtannenbaum@epri.com. Nuclear Executive Update: 9