TWR-P (Terrapower, U.S.A.)

Total Page:16

File Type:pdf, Size:1020Kb

TWR-P (Terrapower, U.S.A.) TWR-P (TerraPower, U.S.A.) FIG. 13. Schematic View TerraPower's Prototype Reactor Full name: Travelling Wave Reactor-Prototype (TWR-P) Designer: TerraPower Reactor type: Pool-type, Sodium-cooled Fast Reactor Electrical capacity: 600 MWe Thermal capacity: 1475 MWth Primary Circulation Forced convection using mechanical pumps System Pressure: 0.1 MPa System Temperature: 360/500 °C Fuel Material: Composed of uranium-zirconium metal alloy fuel slugs with a sodium thermal bond in ferritic-martensitic steel cladding Fuel Cycle: 18-24 Months Residual heat removal systems: Passive - Direct Reactor Auxiliary Cooling System Design Life: 40 Years Design status: Conceptual Design Planned deployment/1st date of Start of Construction by 2018 completion: New/Distinguishing Features: Traveling wave reactor 29 Introduction significantly enhanced when compared to A TWR is a class of reactors that is designed currently operating LWRs. to operate indefinitely after a startup period The TWR-P employs enriched fuel using only natural or depleted uranium. The assemblies (driver assemblies) with sealed waves that breed and deeply burn fissile sodium bonded metallic U-Zr10% fuel pins nuclides in-situ travel relative to the fuel and with 70% smear density, for which data and provide the possibility for very long core life experience is available. To achieve flux (~60 years). This long core life allows for profile and power and temperature gradients higher fuel utilization, up to about 30 times similar to those of a TWR and reproduce greater than light water reactors (LWRs). prototypical power histories of breed and The breed and burn process is achieved burn assemblies, the core also employs feed through a “standing wave” by periodic re- fuel assemblies made of depleted uranium. shuffling of the fuel in such a manner that These fuel assemblies have also U-Zr10% higher burn-up assemblies are moved to the metal fuel with 70% smear density. periphery of the core and depleted uranium The core and all primary cooling system fuel assemblies replace the high burn-up components are contained in the reactor fuel. Excess reactivity in the TWR core vessel with the addition of a number of in- increases and control rods are slowly inserted vessel structures. All vessels and structures to offset this increase. The re-shuffling is in direct contact with primary sodium performed during the reactor is shut down coolant are fabricated from 316H stainless each 18 to 24 months. TWR uses advanced steel. Both vessels and a number of major metal fuel and advanced ferritic-martensitic components are supported from the reactor steel cladding with capabilities to reach high head, which is supported by a bearing system peak burnups of ~30% and high doses interfaced to a concrete ledge in the reactor necessary to enable breed and burn operation building on depleted uranium. The TWR-P is a Description of the Safety Concept prototype of TWR to demonstrate TWR core TWR-P is similar to other pool-type, fuel management, qualify TWR advanced sodium-cooled fast reactors in that Loss of fuel assemblies, and validate core radial Coolant Accidents are eliminated from the expansion reactivity feedback and design bases. The primary design basis effectiveness of the core restraint system. accidents are Loss of Flow and Loss of Heat Description of the Nuclear System Sink. Transient overpower events are less TWR-P is a1475MWth/600MWe gross liquid frequent because interlocks prevent sodium cooled, fast neutron spectrum reactor excessive rod withdrawal during operation. that uses U-10%Zr metallic fuel with HT-9 The TWR-P plant employs for emergency ferritic-martensitic stainless steel clad. The decay heat removal four Direct Reactor plant’s 4m diameter, 5.5m tall cylindrical Auxiliary Cooling System (DRACS) loops core sits near the bottom of a 13.3m dissipating heat to air as an ultimate heat diameter, 17.65m tall reactor vessel which is sink, each of which is capable of removing enclosed within a guard vessel. This pool- enough heat to protect public health and type configuration has no radial piping safety. These NaK filled loops are penetrations through either vessel so the risk completely passive and require no electricity of loss of coolant accidents is eliminated. to activate or operate. The large volume of sodium acts as a huge Deployment Status and Planned Schedule heat sink, so transients are much slower, The TWR-P is expected to be constructed providing operators much longer time to between 2018 and 2023. After a period of respond to off-normal events and the overall testing and optimization, commercial plants safety performance of the plant is are expected to be licensed with start up in the late 2020s or early 2030s. 30 .
Recommended publications
  • A Comparison of Advanced Nuclear Technologies
    A COMPARISON OF ADVANCED NUCLEAR TECHNOLOGIES Andrew C. Kadak, Ph.D MARCH 2017 B | CHAPTER NAME ABOUT THE CENTER ON GLOBAL ENERGY POLICY The Center on Global Energy Policy provides independent, balanced, data-driven analysis to help policymakers navigate the complex world of energy. We approach energy as an economic, security, and environmental concern. And we draw on the resources of a world-class institution, faculty with real-world experience, and a location in the world’s finance and media capital. Visit us at energypolicy.columbia.edu facebook.com/ColumbiaUEnergy twitter.com/ColumbiaUEnergy ABOUT THE SCHOOL OF INTERNATIONAL AND PUBLIC AFFAIRS SIPA’s mission is to empower people to serve the global public interest. Our goal is to foster economic growth, sustainable development, social progress, and democratic governance by educating public policy professionals, producing policy-related research, and conveying the results to the world. Based in New York City, with a student body that is 50 percent international and educational partners in cities around the world, SIPA is the most global of public policy schools. For more information, please visit www.sipa.columbia.edu A COMPARISON OF ADVANCED NUCLEAR TECHNOLOGIES Andrew C. Kadak, Ph.D* MARCH 2017 *Andrew C. Kadak is the former president of Yankee Atomic Electric Company and professor of the practice at the Massachusetts Institute of Technology. He continues to consult on nuclear operations, advanced nuclear power plants, and policy and regulatory matters in the United States. He also serves on senior nuclear safety oversight boards in China. He is a graduate of MIT from the Nuclear Science and Engineering Department.
    [Show full text]
  • Fast-Spectrum Reactors Technology Assessment
    Clean Power Quadrennial Technology Review 2015 Chapter 4: Advancing Clean Electric Power Technologies Technology Assessments Advanced Plant Technologies Biopower Clean Power Carbon Dioxide Capture and Storage Value- Added Options Carbon Dioxide Capture for Natural Gas and Industrial Applications Carbon Dioxide Capture Technologies Carbon Dioxide Storage Technologies Crosscutting Technologies in Carbon Dioxide Capture and Storage Fast-spectrum Reactors Geothermal Power High Temperature Reactors Hybrid Nuclear-Renewable Energy Systems Hydropower Light Water Reactors Marine and Hydrokinetic Power Nuclear Fuel Cycles Solar Power Stationary Fuel Cells U.S. DEPARTMENT OF Supercritical Carbon Dioxide Brayton Cycle ENERGY Wind Power Clean Power Quadrennial Technology Review 2015 Fast-spectrum Reactors Chapter 4: Technology Assessments Background and Current Status From the initial conception of nuclear energy, it was recognized that full realization of the energy content of uranium would require the development of fast reactors with associated nuclear fuel cycles.1 Thus, fast reactor technology was a key focus in early nuclear programs in the United States and abroad, with the first usable nuclear electricity generated by a fast reactor—Experimental Breeder Reactor I (EBR-I)—in 1951. Test and/or demonstration reactors were built and operated in the United States, France, Japan, United Kingdom, Russia, India, Germany, and China—totaling about 20 reactors with 400 operating years to date. These previous reactors and current projects are summarized in Table 4.H.1.2 Currently operating test reactors include BOR-60 (Russia), Fast Breeder Test Reactor (FBTR) (India), and China Experimental Fast Reactor (CEFR) (China). The Russian BN-600 demonstration reactor has been operating as a power reactor since 1980.
    [Show full text]
  • Traveling Wave Reactor
    TRAVELING WAVE REACTOR ©M. Ragheb 3/13/2013 INTRODUCTION In the 2012 USA budget, $853 million is allocated for nuclear research, including small reactors. A 30-person Company, TerraPower LLC, at Bellevue, Washington, with Bill Gates, Microsoft’s founder, as a chairperson, proposes a conceptual design of a reactor that would use spent fuel from Light Water Reactors, LWRs and depleted uranium to run for about 60 years, breeding its own fuel as Pu239 from depleted uranium as U238. Venture capital firms Charles River Ventures and Khosia Ventures invested $35 million into the project in 2010. Contrary to the media-perceived physical movement of the breeding and burn waves in a slab or horizontal cylinder geometry, in the TerraPower latest concept, the fuel is shuffled into the burning region as it breeds enough fissile fuel to keep the reactor critical for long times. The Traveling Wave Reactor, TWR constitutes a reformulation of the Liquid Metal Fast Reactor, LMFBR and the “coupled cores” concepts and a reformulation of “Battery Reactors” based on Naval Propulsion reactors designs. As a function of time, the latest design represents a standing wave or a soliton, rather than a traveling wave. The use of a Th cycle with a solid fuel or a molten salt coolant would present a larger more sustainable resource base alternative, since Th is four times more abundant than U in the Earth’s crust. HISTORY The traveling wave reactor concept has been around for years. The concept dates back to 1958 and was first formulated by Saveli M. Feinberg who envisioned a nuclear reactor that uses depleted U in the form of the fertile isotope U238 as target material and a source of the fissile highly enriched U235 on an end of a long cylinder or parallelepiped, enough to generate a critical mass.
    [Show full text]
  • Nuclear Fuel Cycles Technology Assessment
    Clean Power Quadrennial Technology Review 2015 Chapter 4: Advancing Clean Electric Power Technologies Technology Assessments Advanced Plant Technologies Biopower Carbon Dioxide Capture and Storage Clean Power Value-Added Options Carbon Dioxide Capture for Natural Gas and Industrial Applications Carbon Dioxide Capture Technologies Carbon Dioxide Storage Technologies Crosscutting Technologies in Carbon Dioxide Capture and Storage Fast-spectrum Reactors Geothermal Power High Temperature Reactors Hybrid Nuclear-Renewable Energy Systems Hydropower Light Water Reactors Marine and Hydrokinetic Power Nuclear Fuel Cycles Solar Power Stationary Fuel Cells Supercritical Carbon Dioxide Brayton Cycle U.S. DEPARTMENT OF Wind Power ENERGY Clean Power Quadrennial Technology Review 2015 Nuclear Fuel Cycles Chapter 4: Technology Assessments Introduction and Background The Nuclear Fuel Cycle (NFC) is defined as the total set of operations required to produce fission energy and manage the associated nuclear materials. It can have different attributes, including the extension of natural resources, or the minimization of waste disposal requirements. The NFC, as depicted in Figure 4.O.1, is comprised of a set of operations that include the extraction of uranium (U) resources from the earth (and possibly from seawater), uranium enrichment and fuel fabrication, use of the fuel in reactors, interim storage of used nuclear fuel, the optional recycle of the used fuel, and the final disposition of used fuel and waste forms from the recycling processes. Thorium (Th) fuel cycles have been proposed also, but have not been commercially implemented). Figure 4.O.1 Schematic of the uranium based Nuclear Fuel Cycle 1 Quadrennial Technology Review 2015 Clean Power TA 4.O: Nuclear Fuel Cycles The nuclear fuel cycle is often grouped into three classical components (front-end, reactor, and back-end): Front End: The focus of the front end of the nuclear fuel cycle is to deliver fabricated fuel to the reactor.
    [Show full text]
  • “Advanced” Isn't Always Better
    SERIES TITLE OPTIONAL “Advanced” Isn’t Always Better Assessing the Safety, Security, and Environmental Impacts of Non-Light-Water Nuclear Reactors “Advanced” Isn’t Always Better Assessing the Safety, Security, and Environmental Impacts of Non-Light-Water Nuclear Reactors Edwin Lyman March 2021 © 2021 Union of Concerned Scientists All Rights Reserved Edwin Lyman is the director of nuclear power safety in the UCS Climate and Energy Program. The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet’s most pressing problems. Joining with people across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future. This report is available online (in PDF format) at www.ucsusa.org/resources/ advanced-isnt-always-better and https:// doi.org/10.47923/2021.14000 Designed by: David Gerratt, Acton, MA www.NonprofitDesign.com Cover photo: Argonne National Laboratory/Creative Commons (Flickr) Printed on recycled paper. ii union of concerned scientists [ contents ] vi Figures, Tables, and Boxes vii Acknowledgments executive summary 2 Key Questions for Assessing NLWR Technologies 2 Non-Light Water Reactor Technologies 4 Evaluation Criteria 5 Assessments of NLWR Types 8 Safely Commercializing NLWRs: Timelines and Costs 9 The Future of the LWR 9 Conclusions of the Assessment 11 Recommendations 12 Endnotes chapter 1 13 Nuclear Power: Present and Future 13 Slower Growth, Cost and Safety Concerns 14 Can Non-Light-Water Reactors
    [Show full text]
  • EDI February 2021 Newsletter
    Environmental Defense Institute News on Environmental Health and Safety Issues February 2021 Volume 32 Number 2 INL provides marketing propaganda for TerraPower (and X- energy) and no mention of safety and waste disposal problems The public was welcomed to tune in to an Idaho National Laboratory webinar promoting the recipients of Department of Energy nuclear research funding. But there was no discussion of nuclear waste disposal problems or nuclear reactor accident consequences. And with their stated goal of building reactors for other countries, to somehow solve energy poverty with the most expensive form of energy there is, their answer to nuclear weapons proliferation concerns was basically, “don’t worry, be happy.” Idaho Representative Mike Simpson is a staunch supporter of the handouts of millions of dollars to TerrraPower, with founder Bill Gates, and GE Hitachi Nuclear Energy (GEH) and their Natrium reactor, a “cost-competitive” sodium-cooled fast reactor combined with a molten salt energy storage system. The fast reactors that have been built have been money pits, often spending more time being repaired than operational. 1 The economics of sodium-cooled fast reactors have been awful. The U.S.-built Fast Flux Test Facility operational in 1980 at the Department of Energy’s Hanford site, cost over $10,000 per kilowatt. Japan’s Monju cost over $20,000 per kilowatt, according to IEER. 2 Sodium-cooled reactor promotors are touting the low pressure that the reactor runs at but not mentioning that the sodium metal explodes upon contact with air or water. They also don’t mention that fast reactors are the most inherently unsafe and unreliable reactors available.
    [Show full text]
  • Terrapower and the Traveling Wave Reactor
    CONFIDENTIAL TerraPower and the Traveling Wave Reactor Washington State Senate Energy, Environment & Telecommunications Committee March 28 2013 Doug Adkisson, Senior Vice President Key Points • Who is TerraPower? • What is the Traveling Wave Reactor (TWR)? • How is it different from other reactors? • Why do we think it is a better (safe, economic, less waste) energy source? • Where are we having an impact and Where will it probably be built? Public 2 Who is TerraPower? • For profit company funded by Bill Gates (Chairman), Mukesh Ambani (Reliance), Vinod Khosla, and other visionary private investors • A nuclear power innovation company. Will not build, own or operate nuclear plants – no nuclear liability exposure • Expert management and staff with 300 man-years of experience on fast reactors (e.g., FFTF, EBR –II) • Over 80 contracts/agreements with national labs, universities, companies, government agencies and expert consultants since 2007 • Have state-of-the-art computer capabilities and proprietary software for reactor simulations • Enormous data base and access to spent fuel assemblies from previous fast reactors. Owns TWR intellectual property and know-how Public 3 The TerraPower Team: Innovative Collaborative Approach Public 4 What is the TWR? Fuel from Available Depleted Uranium • Breeds and burns depleted uranium or discharged LWR fuel • Fueled once and can burn up to 40+ years • Weapons proliferation resistant. • The “Traveling Wave” evolved to a conventional geometry • Assemblies are shuffled within a reactor vessel, limited
    [Show full text]
  • Jinan J. Yang – Résumé
    Jinan J. Yang – Résumé Work: Contact Information: Radiation Transport Group E-mail: [email protected] Reactor and Nuclear Systems Division Phone: (865) 574-7355 Oak Ridge National Laboratory P.O. Box 2008, MS 6170 Oak Ridge, TN 37831-6170 Education Mar. 2011 Ph.D. in Nuclear Engineering and Radiological Sciences - University of Michigan Thesis title: A Functional Monte Carlo (FMC) Method for k-Eigenvalue Problems Advisor: Professor Edward W. Larsen Dec. 2007 M.S. in Nuclear Engineering and Radiological Sciences, University of Michigan Jul. 1988 B.Sc. in Applied Mathematics, Xian JiaoTong University (China) Graduate courses taken at the University of Michigan: Nuclear Reactor Theory I, Nuclear Reactor Theory II, Nuclear Reactor Kinetics, Radiation Shielding, Reactor Safety Analysis, Nuclear Core Design and Analysis I, Transport Theory, Transport Theory II, Nuclear Mea- surement Laboratory, Stochastic Processes, Monte Carlo Methods, Introduction to Plasmas, Intermediate Plasma Physics I, Complex Variables, Numerical Methods for Scientific Computing I, Numerical Methods for Scientific Computing II, and C++ Programming for Graduate Students. GPA: 8. 56 ( A+ = 9.0, A = 8.0, A- = 7.0 ) Professional Experience Jan. 2016 - Radiation Transport Group, Oak Ridge National Laboratory, Oak Ridge, TN 37831 Present R&D Staff Member • The Consortium for Advanced Simulation of Light Water Reactors (CASL) milestone “Mecha- nism to Perturb Pin-By-Pin Enrichment and Mass”: Implemented fuel mass, fuel isotope and nonfuel isotope perturbations in VERA. Key developer. • ORNL Laboratory Directed Research and Development (LDRD) Seed Money Fund “Develop- ment of a Whole Core Simulation Capability for Pebble Bed Reactors”. Co-PI. • NRC “Coupling Fuel Performance with Neutronics” project: The project explores options to couple the fuel performance code FAST to SCALE for more accurate and automated fuel per- formance and lattice physics calculations for both LWR and non-LWR fuel.
    [Show full text]
  • [Document Title]
    [EHNUR WP 4] ADVANCED NUCLEAR POWER PLANT CONCEPTS AND TIMETABLES FOR THEIR COMMERCIAL DEPLOYMENT Steven C. Sholly1 VIENNA, June 2013 1 Institute of Safety/Security and Risk Sciences, University of Natural Resources and Life Sciences Copyright Vienna, June 2013 Media owner and editor: University of Natural Resources and Life Sciences Vienna, Department of Water, Atmosphere and Environment, Institute of Safety and Risk Sciences, Borkowskigasse 4, 1190 Wien, Austria URL: http://www.risk.boku.ac.at ReportWP4 – Advanced Nuclear Power Plant Concepts and Timetables EHNUR EXECUTIVE SUMMARY Most currently operating nuclear power plants are Generation II reactors (except for a few remaining Generation I units and a few Generation III units). Generation III and Generation III+ nuclear power plant concepts are widely recognized to be significant improvements over Generation II reactor designs. Both Generation III designs (standardized designs safer than Generation II) and Generation III+ designs (standardized designs safer than Generation II and with the expectation of greater economy of scale) are available for immediate deployment. The absolute minimum schedule for a Generation III or III+ nuclear power plant project is 10 years from feasibility study to completion of startup testing. Such a schedule is only achievable by: (a) an experienced utility, (b) with the reactor sited at an existing nuclear power plant site, and (c) with a design for which first-of-a-kind engineering (FOAKE) is complete. Under other circumstances (e.g. a utility new to nuclear generation, a greenfield site, a utility in a country without significant nuclear infrastructure, a nuclear power plant design where FOAKE has not yet been accomplished), the schedule would extend from fifteen to seventeen years and perhaps more.
    [Show full text]
  • Mechanical Analogy for the Wave of Nuclear Burning
    MECHANICAL ANALOGY FOR THE WAVE OF NUCLEAR BURNING V.V. Urbanevich, I.V. Sharph, V.A. Tarasov, V.D. Rusov Odessa National Polytechnic University, Shevchenko av. 1, Odessa 65000, Ukraine Abstract We consider a model of neutron-nuclear wave burning. The wave of nuclear burning of the medium is initiated by an external neutron source and is the basis for the new generation reactors { the so-called "traveling-wave reactors". We develop a model of nuclear wave burning, for which it is possible to draw an analogy with a mechanical dissipative system. Within the framework of the new model, we show that two burning modes are possible depending on the control parameters: a traveling autowave and a wave driven by an external neutron source. We find the autowave to be possible for certain neutron energies only, and the wave velocity has a continuous spectrum bounded below. 1 Introduction A problem of providing the humankind with energy has been around for a while. Today the experts tend to associate its solution with two major directions: the fusion reactors and the 5th generation nuclear reactors (as well as their hybrid versions { fusion-fission reactors) [1{8]. And today, while these projects are not yet implemented in practice, their importance largely depends on which one will be created first. The present paper is devoted to the theoretical study of the wave neutron-nuclear burning modes, which are the basis for some nuclear reactors of the 5th generation (Gen-V), e.g. [1{4,9{41]. These reactors are often referred to as the Feoktistov reactors (in USA more common "Traveling- wave reactors", and in Japan { "CANDLE"-reactors).
    [Show full text]
  • DOE-ID NEPA CX DETERMINATION Idaho National Laboratory Page 1 of 5 CX Posting No.: DOE-ID-INL-16-115
    DOE-ID NEPA CX DETERMINATION Idaho National Laboratory Page 1 of 5 CX Posting No.: DOE-ID-INL-16-115 SECTION A. Project Title: TerraPower Traveling Wave Reactor Research and Development Activities at Idaho National Laboratory SECTION B. Project Description and Purpose: The purpose of this revision is to refine and add scope to the proposed action. This environmental checklist covers TerraPower research in developing a new Generation IV nuclear power plant based on its Traveling Wave Reactor (TWR) concept. TWRs take advantage of a “breed-and-burn” process by which fissile material is bred in situ from natural or depleted uranium (DU) to sustain power operations for decades without enrichment or reprocessing. The breed-and- burn nuclear fuel cycle minimizes reliance on enriched uranium, and would allow TerraPower to deliver an economical and sustainable energy source without increasing proliferation concerns. The Prototype Traveling Wave Reactor plant (TWR-P) is currently in the design phase. Idaho National Laboratory (INL) conducts test pin fabrication, irradiation testing, and post-irradiation examination (PIE) activities to evaluate methods for a commercial-scale metal fuel fabrication process for manufacture of TerraPower's first TWR-P core. Research and Development (R&D) activities associated with this activity at INL include 1) purchasing and installing equipment in the Materials and Fuel Complex (MFC) Experimental Fuels Facility (EFF), building MFC-794 and the Fuels and Applied Science Building (FASB), MFC-787 to develop a process to fabricate TerraPower test pins; 2) characterize un-irradiated fuel to confirm fuel development and examine irradiation performance; 3) fabricating test pins for irradiation testing at Department of Energy (DOE) and non-DOE reactors; 4) shipping test pins to and from test reactors; and 5) performing PIE of irradiated test pins.
    [Show full text]
  • A Preliminary Engineering Design Study for a Standpipe Viewport
    PNNL-23029 Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 Summary of the Preliminary Optical ICHMI Design Study: A Preliminary Engineering Design Study for a Standpipe Viewport NC Anheier Jr EJ Berglin H Qiao BK Hatchell December 2013 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. PACIFIC NORTHWEST NATIONAL LABORATORY operated by BATTELLE for the UNITED STATES DEPARTMENT OF ENERGY under Contract DE-AC05-76RL01830 Printed in the United States of America Available to DOE and DOE contractors from the Office of Scientific and Technical Information, P.O. Box 62, Oak Ridge, TN 37831-0062; ph: (865) 576-8401 fax: (865) 576-5728 email: [email protected] Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 22161 ph: (800) 553-6847 fax: (703) 605-6900 email: [email protected] online ordering: http://www.ntis.gov/ordering.htm This document was printed on recycled paper.
    [Show full text]