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Author: Yi Mi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Integral Pressurized Water Reactor (iPWR) type SMR designs were studied featuring Passive Safety Systems (PSS) in all cases. As many as 11 current SMR designs use PSS to remove decay heat. Variations in PSS designs were studied and compared using evaluation metrics and a proposed weighting method. This resulted in classification of iPWRs designs based on the methodology presented. A prototypic Passive Residual Heat Removal System (PRHRS) was then studied using a scaling analysis to compare the scaling ratio of system parameters, and failure probability relative to existing reference LWR plant data. The impact of single versus two-phase PRHRS designs was also considered. We found that a classical Probabilistic Risk Assessment (PRA) model describing active systems does not consider time evolution nor event ordering that a dynamic PRA approach can accommodate. We thus developed and realized basic coupling between LabVIEW as simulation code and CAFTA as PRA code. Coupling these codes using Python provides real-time simulation that leads to a dynamic simulation result. A representative difference in failure probability using dynamic versus classic PRA revealed that for one, there can be more component demands with different event ordering; thus providing insights into PSS failure probability in the iPWR-type SMR designs. The limitation of the work is essentially in the proprietary details of each SMR design. The value however is in the integrated method of system analysis.
Author: Yi Mi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Integral Pressurized Water Reactor (iPWR) type SMR designs were studied featuring Passive Safety Systems (PSS) in all cases. As many as 11 current SMR designs use PSS to remove decay heat. Variations in PSS designs were studied and compared using evaluation metrics and a proposed weighting method. This resulted in classification of iPWRs designs based on the methodology presented. A prototypic Passive Residual Heat Removal System (PRHRS) was then studied using a scaling analysis to compare the scaling ratio of system parameters, and failure probability relative to existing reference LWR plant data. The impact of single versus two-phase PRHRS designs was also considered. We found that a classical Probabilistic Risk Assessment (PRA) model describing active systems does not consider time evolution nor event ordering that a dynamic PRA approach can accommodate. We thus developed and realized basic coupling between LabVIEW as simulation code and CAFTA as PRA code. Coupling these codes using Python provides real-time simulation that leads to a dynamic simulation result. A representative difference in failure probability using dynamic versus classic PRA revealed that for one, there can be more component demands with different event ordering; thus providing insights into PSS failure probability in the iPWR-type SMR designs. The limitation of the work is essentially in the proprietary details of each SMR design. The value however is in the integrated method of system analysis.
Author: Nicolas Zweibaum
Publisher:
ISBN:
Category :
Languages : en
Pages : 231
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The development of advanced nuclear reactor technology requires understanding of complex, integrated systems that exhibit novel phenomenology under normal and accident conditions. The advent of passive safety systems and enhanced modular construction methods requires the development and use of new frameworks to predict the behavior of advanced nuclear reactors, both from a safety standpoint and from an environmental impact perspective. This dissertation introduces such frameworks for scaling of integral effects tests for natural circulation in fluoride-salt-cooled, high-temperature reactors (FHRs) to validate evaluation models (EMs) for system behavior; subsequent reliability assessment of passive, natural- circulation-driven decay heat removal systems, using these validated models; evaluation of life cycle carbon dioxide emissions as a key environmental impact metric; and recommendations for further work to apply these frameworks in the development and optimization of advanced nuclear reactor designs. In this study, the developed frameworks are applied to the analysis of the Mark 1 pebble-bed FHR (Mk1 PB-FHR) under current investigation at the University of California, Berkeley (UCB). The capability to validate integral transient response models is a key issue for licensing new reactor designs. This dissertation presents the scaling strategy, design and fabrication aspects, and startup testing results from the Compact Integral Effects Test (CIET) facility at UCB, which reproduces the thermal hydraulic response of an FHR under forced and natural circulation operation. CIET provides validation data to confirm the performance of the direct reactor auxiliary cooling system (DRACS) in an FHR, used for natural-circulation-driven decay heat removal, under a set of reference licensing basis events, as predicted by best-estimate codes such as RELAP5-3D. CIET uses a simulant fluid, Dowtherm A oil, which at relatively low temperatures (50-120°C) matches the Prandtl, Reynolds, Froude and Grashof numbers of the major liquid salts simultaneously, at approximately 50% geometric scale and heater power under 2% of prototypical conditions. The studies reported here include isothermal pressure drop tests performed during startup testing of CIET, with extensive pressure data collection to determine friction losses in the system, as well as subsequent heated tests, from parasitic heat loss tests to more complex feedback control tests and natural circulation experiments. For initial code validation, coupled steady-state single-phase natural circulation loops and simple forced cooling transients were conducted in CIET. For various heat input levels and temperature boundary conditions, fluid mass flow rates and temperatures were compared between RELAP5- 3D results, analytical solutions when available, and experimental data. This study shows that RELAP5-3D provides excellent predictions of steady-state natural circulation and simple transient forced cooling in CIET. The code predicts natural circulation mass flow rates within 8%, and steady-state and transient fluid temperatures, under both natural and forced circulation, within 2°C of experimental data, suggesting that RELAP5-3D is a good EM to use to design and license FHRs. A key element in design and licensing of new reactor technology lies in the analysis of the plant response to a variety of potential transients. When applicable, this involves understanding of passive safety system behavior. This dissertation develops a framework to assess reliability and propose design optimization and risk mitigation strategies associated with passive decay heat removal systems, applied to the Mk1 PB-FHR DRACS. This investigation builds upon previous detailed design work for Mk1 components and the use of RELAP5-3D models validated for FHR natural circulation phenomenology. For risk assessment, reliability of the point design of the passive safety system for the Mk1 PB-FHR, which depends on the ability of various structures to fulfill their safety functions, is studied. Whereas traditional probabilistic risk assessment (PRA) methods are based on event and fault trees for components of the system that perform in a binary way - operating or not operating -, this study is mostly based on probability distributions of heat load compared to the capacity of the system to remove heat, as recommended by the reliability methods for passive safety functions (RMPS) that are used here. To reduce computational time, the use of response surfaces to describe the system in a simplified manner, in the context of RMPS, is also demonstrated. The design optimization and risk mitigation part proposes a framework to study the elements of the design of the reactor, and more specifically its passive safety cooling system, which can contribute to enhanced reliability of heat removal under accident conditions. Risk mitigation measures based on design, startup testing, in-service inspection and online monitoring are proposed to narrow probability distributions of key parameters of the system and increase reliability and safety. Another major aspect in the development of novel energy systems is the assessment of their impacts on the environment compared to current technologies. While most existing life cycle assessment (LCA) studies have been applied to conventional nuclear power plants, this dissertation proposes a framework to extend such studies to advanced reactor designs, using the example of the Mk1 PB-FHR. The Mk1 uses a nuclear air-Brayton combined cycle designed to produce 100 MWe of base-load electricity when operated with only nuclear heat, and 242 MWe using natural gas co-firing for peaking power. The Mk1 design provides a basis for quantities and costs of major classes of materials involved in building the reactor and fabricating fuel, and operation parameters. Existing data and economic input-output LCA models are used to calculate greenhouse gas emissions per kWh of electricity produced over the life cycle of the reactor. Baseline life cycle emissions from the Mk1 PB-FHR in base-load configuration are 26% lower than average Generation II light water reactors in the U.S., 98% lower than average U.S. coal plants and 96% lower than average U.S. natural gas combined cycle plants using the same turbine technology. In peaking configuration, due to its nuclear component and higher thermal efficiency, the Mk1 plant only produces 32% of the emissions of average U.S. gas turbine simple cycle peaking plants. One key contribution to life cycle emissions results from the amount and type of concrete used for reactor construction. This is an incentive to develop innovative construction methods using optimized steel-concrete composite wall modules and new concrete mixes to reduce life cycle emissions from the Mk1 and other advanced reactor designs.
Author: Jiyong Oh
Publisher:
ISBN:
Category :
Languages : en
Pages : 368
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Passive cooling systems sometimes use natural circulation, and they are not dependent on emergency AC power or offsite power, which can make designs simpler through the reduction of emergency power supplying infrastructure. The passive system approach can lead to substantial simplification of the system as well as overall economic benefits, and passive systems are believed to be less vulnerable to accidents by component failures and human errors compared to active systems. The viewpoint that passive system design is more reliable and more economical than active system design has become generally accepted. However, passive systems have characteristics of a high level of uncertainty and low driving force for purposes of heat removal phenomena. These characteristics of passive systems can result in increasing system unreliability and may raise potential remedial costs during a system's lifetime. This study presents a comprehensive comparison of reliability and cost taking into account uncertainties and introduces the concept of flexibility using the example of active and passive residual heat removal systems in a PWR. The results show that the active system can have, for this particular application, greater reliability than the passive system. Because the passive system is economically optimized, its heat removal capacity is much smaller than that of the active system. Thus, functional failure probability of the passive system has a greater impact on overall system reliability than the active system. Moreover, considering the implications of flexibility upon remedial costs, the active system may more economical than the passive system because the active system has flexible design features for purposes of increasing heat removal capacity.
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Languages : en
Pages :
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This report summarizes the results of a three-year collaboration between Argonne National Laboratory (ANL) and the Korea Atomic Energy Research Institute (KAERI) to identify and quantify the performance of innovative design features in metallic-fueled, sodium-cooled fast reactor designs. The objective of the work was to establish the reliability and safety margin enhancements provided by design innovations offering significant potential for construction, maintenance, and operating cost reductions. The project goal was accomplished with a combination of advanced model development (Task 1), analysis of innovative design and safety features (Tasks 2 and 3), and planning of key safety experiments (Task 4). Task 1--Computational Methods for Analysis of Passive Safety Design Features: An advanced three-dimensional subassembly thermal-hydraulic model was developed jointly and implemented in ANL and KAERI computer codes. The objective of the model development effort was to provide a high-accuracy capability to predict fuel, cladding, coolant, and structural temperatures in reactor fuel subassemblies, and thereby reduce the uncertainties associated with lower fidelity models previously used for safety and design analysis. The project included model formulation, implementation, and verification by application to available reactor tests performed at EBR-II. Task 2--Comparative Analysis and Evaluation of Innovative Design Features: Integrated safety assessments of innovative liquid metal reactor designs were performed to quantify the performance of inherent safety features. The objective of the analysis effort was to identify the potential safety margin enhancements possible in a sodium-cooled, metal-fueled reactor design by use of passive safety mechanisms to mitigate low-probability accident consequences. The project included baseline analyses using state-of-the-art computational models and advanced analyses using the new model developed in Task 1. Task 3--Safety Implications of Advanced Technology Power Conversion and Design Innovations and Simplifications: Investigations of supercritical CO2 gas turbine Brayton cycles coupled to the sodium-cooled reactors and innovative concepts for sodium-to-CO2 heat exchangers were performed to discover new designs for high efficiency electricity production. The objective of the analyses was to characterize the design and safety performance of equipment needed to implement the new power cycle. The project included considerations of heat transfer and power conversion systems arrangements and evaluations of systems performance. Task 4--Post Accident Heat Removal and In-Vessel Retention: Test plans were developed to evaluate (1) freezing and plugging of molten metallic fuel in subassembly geometry, (2) retention of metallic fuel core melt debris within reactor vessel structures, and (3) consequences of intermixing of high pressure CO2 and sodium. The objective of the test plan development was to provide planning for measurements of data needed to characterize the consequences of very low probability accident sequences unique to metallic fuel and CO2 Brayton power cycles. The project produced three test plans ready for execution.
Author: Zhiyuan Cheng (S.M.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 112
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Small modular reactors (SMRs) hold great promise in meeting a diverse market while reducing the risk of delays during nuclear construction compared to large gigawatt-sized reactors. However, due to lack of economy of scale, their capital cost needs to be reduced. Increasing the compactness or power density of the nuclear island is one way to reduce capital cost. This work first assesses the transient analysis of a compact integral small light water reactor to examine its safety performance. Subsequently, a parametric optimization study with the goal of increasing its power density (i.e. improve its market competitiveness) while maintaining safety is performed. A model of the reactor is established using RELAP5/3.3gl, with reference to the features of Nuward SMR. Nuward is a compact 170 MWe Pressurized Water Reactor, whose key features include the use of Compact Steam Generators and a large water tank in which the containment submerges for passive heat removal. A transient analysis of the reference reactor after Loss of Flow Accident, Station Blackout, and Loss of Coolant Accident is carried out. Following all three accidents, the integrity of the fuel and the reactor is maintained. The passive cooling system is estimated to provide 12 - 13 days of grace period. The parametric optimization study indicates that the size of the tank can be reduced to half and still maintain sufficient margin to both short-term and long-term safety goals after all three transients with an estimated grace period of 7 - 8 days. In addition, the configuration of the passive safety system can be rearranged to reduce the size of the containment to 76% of the reference design without affecting its safety performance. By increasing the coolant enthalpy change, which also results in a higher thermal efficiency, the electrical output of the reference design can be enhanced by 44% without major design changes. If the number of pumps in the vessel are increased by 2, the electrical output can be enhanced by 102% while satisfying all safety criteria. The uprated power that satisfies a 72-hour grace period requires a tank size that is 32.5% of the reference design. Such compact and simplified nuclear steam supply system can partially address the lack of economy of scale for the reference SMR and improve its market competitiveness.
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Languages : en
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Advanced small modular reactor designs include many advantageous design features such as passively driven safety systems that are arguably more reliable and cost effective relative to conventional active systems. Despite their attractiveness, a reliability assessment of passive systems can be difficult using conventional reliability methods due to the nature of passive systems. Simple deviations in boundary conditions can induce functional failures in a passive system, and intermediate or unexpected operating modes can also occur. As part of an ongoing project, Argonne National Laboratory is investigating various methodologies to address passive system reliability. The Reliability Method for Passive Systems (RMPS), a systematic approach for examining reliability, is one technique chosen for this analysis. This methodology is combined with the Risk-Informed Safety Margin Characterization (RISMC) approach to assess the reliability of a passive system and the impact of its associated uncertainties. For this demonstration problem, an integrated plant model of an advanced small modular pool-type sodium fast reactor with a passive reactor cavity cooling system is subjected to a station blackout using RELAP5-3D. This paper discusses important aspects of the reliability assessment, including deployment of the methodology, the uncertainty identification and quantification process, and identification of key risk metrics.
Author: Raymond Michael Fanning
Publisher:
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Category :
Languages : en
Pages : 38
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"Next generation nuclear power plants, specifically small modular reactor designs, are the best alternative to fossil fuels for power generation due to their power density and low carbon emissions and constant awareness of safety concerns. A promising safety feature of new designs is the removal of heat by passive systems in accident scenarios. The passive systems require no moving parts and no intervention by personnel. These systems must be accurately simulated for better understanding of the heat transport phenomena: natural convection cooling. Due to the fact that most work developing these passive heat removal systems are proprietary information, a passive heat removal system for a small modular reactor was designed and simulated in Star CCM+ to evaluate the capability of natural convective flows to remove decay heat in a shutdown scenario. The size and dimensions of the heat exchanger are based on the Westinghouse-SMR design. The design of the passive heat removal system was a hexagonal lattice heat exchanger. The final design was projected to dissipate the 56MW of decay heat at the rate simulated in Star CCM+"--Abstract, page iv.
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Languages : en
Pages :
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The rapid growth in the size and complexity of commercial nuclear power plants in the 1970s spawned an interest in smaller, simpler designs that are inherently or intrinsically safe through the use of passive design features. Several designs were developed, but none were ever built, although some of their passive safety features were incorporated into large commercial plant designs that are being planned or built today. In recent years, several reactor vendors are actively redeveloping small modular reactor (SMR) designs with even greater use of passive features. Several designs incorporate the ultimate in passive safety they completely eliminate specific accident initiators from the design. Other design features help to reduce the likelihood of an accident or help to mitigate the accident s consequences, should one occur. While some passive safety features are common to most SMR designs, irrespective of the coolant technology, other features are specific to water, gas, or liquid-metal cooled SMR designs. The extensive use of passive safety features in SMRs promise to make these plants highly robust, protecting both the general public and the owner/investor. Once demonstrated, these plants should allow nuclear power to be used confidently for a broader range of customers and applications than will be possible with large plants alone.
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Category : Power resources
Languages : en
Pages : 1032
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Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Author: International Atomic Energy Agency
Publisher: IAEA Tecdoc
ISBN: 9789201086143
Category : Science
Languages : en
Pages : 223
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This publication summarizes the results of an IAEA coordinated research project on the development of advanced methodologies for the assessment of passive safety system performance in advanced reactors. This includes discussions on various methodologies to assess the performance of passive engineered safety features in innovative small reactors, including the Indian AHWR 300 LEU and the Argentinian CAREM25. The publication focuses on the different reliability assessment approaches, methodologies, analysis and evaluation of the results and technical challenges. It provides the insights resulting from the analysis on the technical issues associated with assessing the reliability of passive systems in the context of nuclear safety and probabilistic safety analysis. A viable path towards the implementation of the research efforts in the related areas is also delineated.
