Fuel Reliability (QA)

Transcription

1 Program Description Fuel Reliability (QA) Program Overview Fuel failures and other fuel-related issues can have significant operational impacts on nuclear power plants. Failures, for example, can cost utilities tens of millions of dollars per event to cover replacement power costs and the costs of a fuel reload. While the industry has made substantial progress in reducing the frequency of fuel failures, sustaining this success will require continued attention to technical gaps impacting fuel reliability. There are also opportunities to enhance the performance of nuclear fuel under accident conditions through more robust fuel designs. The Fuel Reliability Program drives improvements in nuclear fuel performance and reliability based on issues encountered at operating plants around the world. Research addresses multiple aspects of fuel performance and reliability, including fuel failure root-cause resolution, fuel/water chemistry interactions, operational margins through end of life, and improved safety margins during accident conditions. The new knowledge is then applied to update fuel reliability guidance, to develop new and enhance existing software products, and to provide technical feedback for new fuel designs. The program also engages nuclear regulatory agencies and provides technical input regarding fuel-related regulations. Research Value About $45-$50 billion of nuclear fuel is operating in commercial reactors worldwide. Optimizing the use of this fuel, while ensuring its safe operation, is paramount to reliable, cost-effective nuclear plant operation. Fuel Reliability Program participants gain access to the following: Strategic roadmaps outlining research gaps confronting key issues such as fuel failures caused by gridto-rod fretting and foreign objects, and regulatory issues related to loss of coolant accidents and reactivity-initiated accidents and the collaborative actions needed to address these gaps. Technical guidance to improve fuel reliability and reduce economic risks associated with fuel failures, which have cost the U.S. nuclear industry more than $300 million over the past decade and the global nuclear industry 2-3 times that amount. Assessment of breakthrough fuel concepts that could provide additional plant response time before damage and fission product release occurs in accident scenarios. Global operating experience with all types of nuclear fuel assemblies and reactor types to inform decision-making. State-of-the-art software tools to analyze fuel rod thermal-mechanical performance and assess crud and corrosion risk under a range of operating conditions, helping nuclear plants manage a variety of margins. Data and technical insights pertaining to the use of high-burnup nuclear fuels. Electric Power Research Institute (EPRI) studies indicate that economic savings of hundreds of millions of dollars per year could be achieved by moving closer to the current burnup limit and by increasing the licensed limit. Technical studies to inform regulators and ensure regulations impacting nuclear fuel are technically based and not unnecessarily conservative. The Fuel Reliability Program develops knowledge, guidance, and tools to maximize the reliability of nuclear fuel and core components. The program also participates in international research consortiums to improve fundamental understanding of in-reactor behavior of fuel, cladding, control materials, and other core components. There are both base and supplemental components to the Fuel Reliability Program. The base program focuses on fuel performance and reliability by quantifying fuel operational margins and identifying fuel failure mechanisms through poolside and hot cell examinations. Projects are cost-shared with fuel vendors to ensure 1

2 2 Electric Power Research Institute Portfolio 2014 information is factored into subsequent fuel designs, thereby driving improvements in fuel reliability. Performance assessments have been initiated for key boiling and pressurized water reactor designs under bounding conditions. A small but important program area focuses on advancing nondestructive poolside techniques to quantify fuel performance margins, locate failed fuel rods, and identify the cause of failure. An industry-wide fuel reliability database, which compiles data on failure root causes, fuel reliability statistics, and good operating practices, also is maintained through the base program. A new research effort initiated in 2012 is evaluating breakthrough fuel technologies. Several technology options are available that offer potential benefits in terms of higher melting temperatures and reduced hydrogen generation during severe accidents. EPRI is teaming with the Department of Energy, nuclear fuel vendors, universities and other research organizations to evaluate and develop promising concepts and overcome potential barriers to commercialization, such as ease of fabrication. The supplemental portion of the Fuel Reliability Program addresses technical issues with regulatory implications and technical issues confronting corrosion and crud control in both boiling and pressurized water reactors. With respect to fuel regulatory issues, EPRI serves as the focal point for technical aspects of regulatory issues by participating in experimental programs and performing independent analyses to further understanding of various accident criteria. Current areas of focus include the applicability of existing reactivity-initiated accident and lossof-coolant accident criteria to high- and intermediate-burnup fuel. With respect to corrosion and crud control, EPRI research helps to improve the understanding of and the links between fuel operation, water chemistry, crud, and fuel reliability in both pressurized water reactors (PWRs) and boiling water reactors (BWRs). The research combines fuel surveillance programs, laboratory and mechanistic studies to develop various guidelines and improve predictive capabilities. Plant demonstrations verify that new technologies and changes in chemistry regimes or core operating strategies do not adversely affect fuel performance. To address strategic objectives established for each of its programs, EPRI has developed roadmaps to plan, coordinate, and execute needed research among multiple entities. For the Fuel Reliability Program, roadmaps have been developed to address the technical barriers confronting fuel failure mechanisms such as those due to foreign objects and grid-to-rod fretting. Roadmaps will be developed for additional issues as conditions warrant. Nuclear plant owners also can participate separately in several supplemental projects: Channel distortion in boiling water reactors: a collaborative effort to develop short-term guidance and advance understanding of channel distortion, which has negatively impacted control blade operability in a number of boiling water reactor plants. Falcon User Group: a forum for contributing experience and lessons learned with the Falcon fuel performance software code. Nuclear Fuel Industry Research Program: a global collaboration of utilities, fuel vendors, and research entities, led by EPRI, focused on generic, long-term issues and opportunities to ensure safe and reliable use of core materials and components. Accomplishments EPRI s Fuel Reliability Program distills global experience with nuclear fuel into actionable guidance and insights that drive measurable improvements in fuel reliability. Continued healthy fuel examinations to support industry efforts toward zero fuel failures. Issued a revision to the Fuel Reliability Guidelines: Fuel Surveillance and Inspection, which now provides a technically based assessment process as to when fuel reliability margin assessments are required. Conducted a fuel surveillance campaign at Nine Mile Point to determine the effects of Online NobleChem on fuel crud or corrosion performance. Surveillance provided insight into operation at a site with two units operating under 24-month cycles, one with high duty and the other with lower duty but having longer fueloperating residence time.

3 3 Electric Power Research Institute Portfolio 2014 Conducted a fuel surveillance campaign at Comanche Peak to determine the effects of reactor coolant elevated ph and lithium on fuel cladding corrosion performance. The Fuel Reliability Program sponsored an earlier demonstration of these effects at Comanche Peak, but this surveillance campaign bridged a knowledge gap after these units had raised fuel duty and integrated lithium exposure. Completed autoclave tests measuring the effects of elevated hydrogen pickup to assess how higher coolant concentrations impact fuel components. These measurements concluded a critical phase of EPRI s elevated reactor coolant hydrogen program for PWRs, which seeks to reduce crack growth rates of non-fuel components with susceptible nickel-based alloys. Revised two handbooks that should be on every nuclear fuel engineer s reference shelf. The Fuel Design Evaluation Handbook outlines technical considerations to support fuel design verification and manufacturing. The Fuel Reliability Monitoring and Failure Evaluation Handbook summarizes fuel failure experience and failure monitoring practices. After initiating research activities to identify operational impacts related to BWR channel distortion, developed a vast operating experience database for BWR Zircaloy-2 channels that led to the development of a new metric for early cycle control blade exposure. Completed a laboratory investigation of shadow corrosion phenomenon. Teamed with the Nuclear Maintenance Application Center and the Institute for Nuclear Power Operations to define and coordinate research tasks to mitigate the threat of foreign materials on fuel reliability. Current Year Activities Fuel Reliability Program research and development for 2014 will focus on a number of remaining fuel reliability gaps, including the continuing threat of foreign materials, the effects of new water chemistry regimes on fuel reliability, development of non-destructive examination equipment, and fuel reliability training. Specific efforts will include the following: Perform fuel failure investigations for events with industry-wide implications Revise several fuel reliability guidelines, including those for BWR fuel cladding corrosion and crud, PWR fuel cladding corrosion and crud, pellet cladding interaction and PWR grid-to-rod fretting Develop non-destructive examination equipment to measure PWR assembly distortion, BWR channel distortion, and hydrogen pick-up by fuel assembly components in BWRs and PWRs. Improve PWR risk assessment tool to avoid crud-induced power shift Refine risk assessment tool for BWRs to better understand interactions between water chemistry, cladding, and fuel duty Assess alternative fuel cladding and BWR channel materials that are more accident tolerant under severe accident conditions Selected reports and products may be prepared in whole or in part in accordance with the EPRI Quality Program Manual that fulfills the requirements of 10CFR50 Appendix B and 10CFR21. The QA status of reports and products will be marked and identified. Estimated 2014 Program Funding $15.5 million Program Manager Jeffrey Deshon, , jdeshon@epri.com

4 4 Electric Power Research Institute Portfolio 2014 Summary of Projects Project Number Project Title Description P Falcon User Group (supplemental) The FALCON User Group provides a forum for nuclear utilities to further develop the fuel performance and analysis capabilities of the FALCON software code. P Channel Distortion Industry Action Plan (supplemental) (QA) P NFIR VI (supplemental) Through the Nuclear Fuel Industry Research (NFIR) Program, EPRI coordinates research on behalf of an international consortium of utilities, fuel vendors, and research laboratories. Research activities focus on generic, long-term issues and opportunities to ensure safe and reliable use of light water reactor core materials and components. The NFIR program seeks to understand fundamental in-reactor behavior of fuel, cladding, control materials, and other core components and to share this valuable knowledge with the industry. Falcon User Group (supplemental) (006165) Description This project provides Falcon users and developers a forum to share how this fuel performance tool is applied to address different issues, lessons learned, and code improvements necessary to enhance nuclear fuel reliability and performance. Falcon is the Electric Power Research Institute's (EPRI's) thermal-mechanical fuel performance code and is able to provide numerical modeling and simulation of fuel behavior under steady-state and transient applications over the entire life cycle of the fuel. The user group meets roughly once per year. The user group provides guidance in upgrading the Falcon code in response to industry needs and operating experience. Support also is available from EPRI throughout the year. Impact The user group allows participants to share experience, suggest improvements, and maximize the value they receive from the code. How to Apply Results Through user group meetings and other communication mechanisms, participants share operating experience with the Falcon code, as well as identify software improvements to address emerging needs.

5 5 Electric Power Research Institute Portfolio 2014 Channel Distortion Industry Action Plan (supplemental) (QA) (069623) Description Seventeen of the 35 BWRs in the United States have reported control blade interference due to channel distortion in the last nine years. Affected fuel designs include Zircaloy-2 channels manufactured by all three U.S. fuel vendors. Multiple mechanisms have been identified that can give rise to channel distortion, which manifest as bow, bulge, and twist. Recent experience indicates that fuel vendor models cannot sufficiently predict the channel distortion. A Channel Distortion Industry Action Plan (CDIAP) has been developed to coordinate efforts among utilities, EPRI, the BWR Owners Group, fuel vendors, and INPO. The purpose of this plan is to provide the industry with an effective short-term and long-term strategy to address channel distortion as an operational issue. Integral to this plan is to understand each mechanism of channel distortion at the scientific (or mechanistic) level. Therefore, the goals of the plan include the following: Update guidance to effectively manage channel distortion until more effective solutions are available Collect and analyze channel performance data, including operational performance data, poolside dimensional measurements, and hot cell examination data Develop a mechanistic understanding of channel distortion and identify gaps in understanding Conduct more detailed examinations to understand and quantify each distortion mechanism Develop improved distortion models and provide to fuel vendors for incorporation into their channel management tools; validate the performance of distortion models via examination and surveillance Ensure proposed materials solutions are appropriately validated Impact Despite substantial past efforts to understand the issue, recent experience indicates channel distortion is not predicted well enough. Results from research in this area will lead to model improvements that ensure core designs are less susceptible to channel distortion. How to Apply Results The initial effort to provide channel distortion guidance will be directly applicable by the utility. The information from poolside measurements and laboratory analysis will be used to improve the models that utilities use to guide core design and manage operational aspects of channel distortion. Selected reports and products may be prepared in whole or in part in accordance with the EPRI Quality Program Manual that fulfills the requirements of 10CFR50 Appendix B and 10CFR21. Reports and other products will indicate their status relative to satisfying QA requirements.

6 6 Electric Power Research Institute Portfolio 2014 NFIR VI (supplemental) (069579) Description The nuclear fuel industry has long recognized the need for a generic, long-term R&D program to ensure safe and reliable use of light water reactor core materials and components. Since 1982, EPRI has led the Nuclear Fuel Industry Research (NFIR) group, an international consortium of utilities, fuel vendors, and research laboratories. The NFIR program seeks to understand fundamental in-reactor behavior of fuel, cladding, control materials, and other core components and to share this valuable knowledge with the industry. In the current phase (NFIR-VI, ), planned projects to be conducted through NFIR will address topics such as the following: Channel bow (irradiation test) Hydrogen pickup in high-burnup BWR fuel Pellet cladding interactions (test reactor irradiation) Thermal stability of irradiation and cold work defects Fuel pellet properties at high burnup (including FGR under external restraint and fuel fragmentation) Ab initio modeling and experiments on pore-size and gas content of fission gas bubbles in UO 2 based fuels Cladding creep: In-pile four point bend stress relaxation tests Impact NFIR enables cost-effective, collaborative work on generic issues important to the industry, but not necessarily tied to a specific fuel design or plant operation. All major vendors, international utilities, and research labs are participants in the program wherein utility participants can advise on fuel R&D issues affecting all vendors, not just their own fuel supplier. Through NFIR participation, participants have the opportunity to network with industry experts from around the world and learn about current and anticipated issues. How to Apply Results NFIR-VI projects will continue to provide fundamental materials properties and behavior data that lead to improved fuel products by improving the knowledge about the behavior of fuel and core components materials. The knowledge and data obtained through these projects will be factored into fuel design modifications, new fuel designs, and operational strategies targeting higher fuel reliability.