Advances in Molten Salt Reactors

Advances in Molten Salt Reactors
Author: Mark Ho,Guan Heng Yeoh,Massimiliano Fratoni
Publsiher: Woodhead Publishing Limited
Total Pages: 135
Release: 2020-02
ISBN 10: 9780081026069
ISBN 13: 0081026064
Language: EN, FR, DE, ES & NL

Advances in Molten Salt Reactors Book Review:

Advances in Molten Salt Reactors combines and presents the latest research and developments in one single resource. It comprehensively reviews a variety of molten salt reactor designs, focussing on aspects of neutronics, thermal-hydraulics, chemistry, material and safety characteristics to give the reader a detailed understanding of each design's underlying dynamic and purpose. Editors Dr. Mark Ho, Professor Massimiliano Frantoni and Professor Huan Heng Yeoh, with their team of expert contributors, combine their experience and knowledge to analyse the variety of design options to ensure engineers are able to make well informed decisions for the most effective energy spectrum for their plants, including salt and material selection, instrumentation challenges and experimental capabilities. This book presents the rapid developments made in molten salt designs from investing countries such as China, the US, UK, Canada and others, considering the work of a variety of key pioneering companies, and is particularly valuable to practising and researching nuclear engineers, and graduate students of advanced nuclear reactor development.

Molten Salt Reactors and Integrated Molten Salt Reactors

Molten Salt Reactors and Integrated Molten Salt Reactors
Author: Bahman Zohuri
Publsiher: Academic Press
Total Pages: 312
Release: 2021-06-29
ISBN 10: 0323918468
ISBN 13: 9780323918466
Language: EN, FR, DE, ES & NL

Molten Salt Reactors and Integrated Molten Salt Reactors Book Review:

Understanding the evolution and advances of energy conversion is critical to meet today’s energy demands while lowering emissions in the fight against climate change. One advancement within nuclear plants that continues to gain interest is molten salt reactors and integrated molten salt reactors, which are the new proposed generation IV small modular reactors. To get up to speed on the latest technology, Molten Salt Reactors and Integrated Molten Salt Reactors: Integrated Power Conversion delivers a critical reference covering the main steps for the application of these reactors. Creating a more environmentally friendly energy production methodology, the reference reviews the past, current, and future states of the reactors including pros and cons, designs and safety features involved, and additional references. Included in the reference is a new approach to energy conversion technology, including coverage on material, economic, and technical challenges towards waste heat recovery, power conversion systems, and advanced computational materials proposed for generation IV systems. Advanced nuclear open air-brayton cycles are also included for higher efficiency. Rounding out with guidance on avoiding salt freezing and salt cleanup for fission and fusion reactors, Molten Salt Reactors and Integrated Molten Salt Reactors: Integrated Power Conversion provides today’s nuclear engineer and power plant engineer with the impactful content of rising efficiency in molten salt reactors, ultimately leading to more efficient and affordable electricity. Gain the latest applications and steps to implement modular reactors, including safety and technical considerations Learn an innovative approach to nuclear air combined cycles (NACC), bringing down the costs of producing electricity in nuclear power plants Practice techniques and computer modeling with additional appendices that include experimental validation methods and computer code results

Materials Issues for Generation IV Systems

Materials Issues for Generation IV Systems
Author: Véronique Ghetta,Dominique Gorse,Dominique Mazière,Vassilis Pontikis
Publsiher: Springer Science & Business Media
Total Pages: 586
Release: 2008-04-23
ISBN 10: 1402084226
ISBN 13: 9781402084225
Language: EN, FR, DE, ES & NL

Materials Issues for Generation IV Systems Book Review:

Global warming, shortage of low-cost oil resources and the increasing demand for energy are currently controlling the world's economic expansion while often opposing desires for sustainable and peaceful development. In this context, atomic energy satisfactorily fulfills the criteria of low carbon gas production and high overall yield. However, in the absence of industrial fast-breeders the use of nuclear fuel is not optimal, and the production of high activity waste materials is at a maximum. These are the principal reasons for the development of a new, fourth generation of nuclear reactors, minimizing the undesirable side-effects of current nuclear energy production technology while increasing yields by increasing operation temperatures and opening the way for the industrial production of hydrogen through the decomposition of water. The construction and use of such reactors is hindered by several factors, including performance limitations of known structural materials, particularly if the life of the projected systems had to extend over the periods necessary to achieve low costs (at least 60 years). This book collects lectures and seminars presented at the homonymous NATO ASI held in autumn 2007 at the Institut d’Etudes Scientifiques in Cargèse, France. The adopted approach aims at improving and coordinating basic knowledge in materials science and engineering with specific areas of condensed matter physics, the physics of particle/matter interaction and of radiation damage. It is our belief that this methodology is crucially conditioning the development and the industrial production of new structural materials capable of coping with the requirements of these future reactors.

Molten Salt Reactors and Thorium Energy

Molten Salt Reactors and Thorium Energy
Author: Thomas James Dolan
Publsiher: Woodhead Publishing
Total Pages: 840
Release: 2017-06-08
ISBN 10: 0081012438
ISBN 13: 9780081012437
Language: EN, FR, DE, ES & NL

Molten Salt Reactors and Thorium Energy Book Review:

Molten Salt Reactors is a comprehensive reference on the status of molten salt reactor (MSR) research and thorium fuel utilization. There is growing awareness that nuclear energy is needed to complement intermittent energy sources and to avoid pollution from fossil fuels. Light water reactors are complex, expensive, and vulnerable to core melt, steam explosions, and hydrogen explosions, so better technology is needed. MSRs could operate safely at nearly atmospheric pressure and high temperature, yielding efficient electrical power generation, desalination, actinide incineration, hydrogen production, and other industrial heat applications. Coverage includes: Motivation -- why are we interested? Technical issues – reactor physics, thermal hydraulics, materials, environment, ... Generic designs -- thermal, fast, solid fuel, liquid fuel, ... Specific designs – aimed at electrical power, actinide incineration, thorium utilization, ... Worldwide activities in 23 countries Conclusions This book is a collaboration of 58 authors from 23 countries, written in cooperation with the International Thorium Molten Salt Forum. It can serve as a reference for engineers and scientists, and it can be used as a textbook for graduate students and advanced undergrads. Molten Salt Reactors is the only complete review of the technology currently available, making this an essential text for anyone reviewing the use of MSRs and thorium fuel, including students, nuclear researchers, industrial engineers, and policy makers. Written in cooperation with the International Thorium Molten-Salt Forum Covers MSR-specific issues, various reactor designs, and discusses issues such as the environmental impact, non-proliferation, and licensing Includes case studies and examples from experts across the globe

Advances in Molten Salt Chemistry

Advances in Molten Salt Chemistry
Author: J. Braunstein,Gleb Mamantov,G. P. Smith
Publsiher: Springer Science & Business Media
Total Pages: 469
Release: 2013-11-21
ISBN 10: 1461582709
ISBN 13: 9781461582700
Language: EN, FR, DE, ES & NL

Advances in Molten Salt Chemistry Book Review:

The first chapter of this volume deals with computer simulation of molten salt behavior by molecular dynamics calculations. The next four chapters are reviews of experimental work: Chapter 2 deals with the solubility of nonre active gases in molten salts, Chapter 3 with various types of organic reactions in molten tetrachloroaluminates, Chapter 4 with techniques for the study of molten fluorides, and Chapter 5 with the physical and chemical properties of thiocyanate melts. The last chapter is a collection of phase diagrams for binary and ternary fluoride systems. J. B., G. M., G. P. S. v CONTENTS Chapter 1 MOLECULAR DYNAMICS CALCULATIONS ON MOLTEN IONIC SALTS L. V. Woodcock 1. Introduction. . 4 2. Intermolecular Forces in Molten Salts 4 2.1. True and Effective Pair Potentials 2.2. Semiempirical Models 6 3. Computational Techniques 13 3.1. Molecular Dynamics Simulation 13 3.2. The Monte Carlo Method 15 3.3. Electrostatic Summations . . 18 4. Calculation of Physical Properties 23 4.1. Equilibrium Properties . 23 4.2. Transport Coefficients 27 4.3. Spectroscopic Properties 32 5. Applications. . . . . . . . 35 5.1. Studies of Interionic Forces. 35 5.2. Microstructure and Mechanisms 40 5.3. Interpretation of Experimental Observables 50 5.4. Reappraisal of Molten Salt Theories . 64 70 6. Conclusions 7. References. 72 vii Contents viii Chapter 2 GAS SOLUBILITY IN MOLTEN SALTS P. Field 1. Introduction 75 2. Experimental Techniques 78 3. Solution Thermodynamics.

Advances in Nuclear Fuel Chemistry

Advances in Nuclear Fuel Chemistry
Author: Markus H.A. Piro
Publsiher: Woodhead Publishing
Total Pages: 670
Release: 2020-03-20
ISBN 10: 008102651X
ISBN 13: 9780081026519
Language: EN, FR, DE, ES & NL

Advances in Nuclear Fuel Chemistry Book Review:

Advances in Nuclear Fuel Chemistry presents a high-level description of nuclear fuel chemistry based on the most recent research and advances. Dr. Markus H.A. Piro and his team of global, expert contributors cover all aspects of both the conventional uranium-based nuclear fuel cycle and non-conventional fuel cycles, including mining, refining, fabrication, and long-term storage, as well as emerging nuclear technologies, such as accident tolerant fuels and molten salt materials. Aimed at graduate students, researchers, academics and practicing engineers and regulators, this book will provide the reader with a single reference from which to learn the fundamentals of classical thermodynamics and radiochemistry. Consolidates the latest research on nuclear fuel chemistry into one comprehensive reference, covering all aspects of traditional and non-traditional nuclear fuel cycles Includes contributions from world-renowned experts from many countries representing government, industry and academia Covers a variety of fuel designs, including conventional uranium dioxide, mixed oxides, research reactor fuels, and molten salt fuels Written by experts with hands-on experience in the development of such designs

Advances of Computational Fluid Dynamics in Nuclear Reactor Design and Safety Assessment

Advances of Computational Fluid Dynamics in Nuclear Reactor Design and Safety Assessment
Author: Jyeshtharaj Joshi,Arun K. Nayak
Publsiher: Woodhead Publishing
Total Pages: 888
Release: 2019-06-09
ISBN 10: 0081023383
ISBN 13: 9780081023389
Language: EN, FR, DE, ES & NL

Advances of Computational Fluid Dynamics in Nuclear Reactor Design and Safety Assessment Book Review:

Advances of Computational Fluid Dynamics in Nuclear Reactor Design and Safety Assessment presents the latest computational fluid dynamic technologies. It includes an evaluation of safety systems for reactors using CFD and their design, the modeling of Severe Accident Phenomena Using CFD, Model Development for Two-phase Flows, and Applications for Sodium and Molten Salt Reactor Designs. Editors Joshi and Nayak have an invaluable wealth of experience that enables them to comment on the development of CFD models, the technologies currently in practice, and the future of CFD in nuclear reactors. Readers will find a thematic discussion on each aspect of CFD applications for the design and safety assessment of Gen II to Gen IV reactor concepts that will help them develop cost reduction strategies for nuclear power plants. Presents a thematic and comprehensive discussion on each aspect of CFD applications for the design and safety assessment of nuclear reactors Provides an historical review of the development of CFD models, discusses state-of-the-art concepts, and takes an applied and analytic look toward the future Includes CFD tools and simulations to advise and guide the reader through enhancing cost effectiveness, safety and performance optimization

Structural Materials for Generation IV Nuclear Reactors

Structural Materials for Generation IV Nuclear Reactors
Author: Pascal Yvon
Publsiher: Woodhead Publishing
Total Pages: 684
Release: 2016-08-27
ISBN 10: 0081009127
ISBN 13: 9780081009123
Language: EN, FR, DE, ES & NL

Structural Materials for Generation IV Nuclear Reactors Book Review:

Operating at a high level of fuel efficiency, safety, proliferation-resistance, sustainability and cost, generation IV nuclear reactors promise enhanced features to an energy resource which is already seen as an outstanding source of reliable base load power. The performance and reliability of materials when subjected to the higher neutron doses and extremely corrosive higher temperature environments that will be found in generation IV nuclear reactors are essential areas of study, as key considerations for the successful development of generation IV reactors are suitable structural materials for both in-core and out-of-core applications. Structural Materials for Generation IV Nuclear Reactors explores the current state-of-the art in these areas. Part One reviews the materials, requirements and challenges in generation IV systems. Part Two presents the core materials with chapters on irradiation resistant austenitic steels, ODS/FM steels and refractory metals amongst others. Part Three looks at out-of-core materials. Structural Materials for Generation IV Nuclear Reactors is an essential reference text for professional scientists, engineers and postgraduate researchers involved in the development of generation IV nuclear reactors. Introduces the higher neutron doses and extremely corrosive higher temperature environments that will be found in generation IV nuclear reactors and implications for structural materials Contains chapters on the key core and out-of-core materials, from steels to advanced micro-laminates Written by an expert in that particular area

Fluid Fuel Reactors

Fluid Fuel Reactors
Author: James A. Lane
Publsiher: Unknown
Total Pages: 979
Release: 1958
ISBN 10: 1928374650XXX
ISBN 13: UOM:39015004451343
Language: EN, FR, DE, ES & NL

Fluid Fuel Reactors Book Review:

SAM Theory Manual

SAM Theory Manual
Author: Anonim
Publsiher: Unknown
Total Pages: 68
Release: 2017
ISBN 10: 1928374650XXX
ISBN 13: OCLC:986144429
Language: EN, FR, DE, ES & NL

SAM Theory Manual Book Review:

The System Analysis Module (SAM) is an advanced and modern system analysis tool being developed at Argonne National Laboratory under the U.S. DOE Office of Nuclear Energy's Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. SAM development aims for advances in physical modeling, numerical methods, and software engineering to enhance its user experience and usability for reactor transient analyses. To facilitate the code development, SAM utilizes an object-oriented application framework (MOOSE), and its underlying meshing and finite-element library (libMesh) and linear and non-linear solvers (PETSc), to leverage modern advanced software environments and numerical methods. SAM focuses on modeling advanced reactor concepts such as SFRs (sodium fast reactors), LFRs (lead-cooled fast reactors), and FHRs (fluoride-salt-cooled high temperature reactors) or MSRs (molten salt reactors). These advanced concepts are distinguished from light-water reactors in their use of single-phase, low-pressure, high-temperature, and low Prandtl number (sodium and lead) coolants. As a new code development, the initial effort has been focused on modeling and simulation capabilities of heat transfer and single-phase fluid dynamics responses in Sodium-cooled Fast Reactor (SFR) systems. The system-level simulation capabilities of fluid flow and heat transfer in general engineering systems and typical SFRs have been verified and validated. This document provides the theoretical and technical basis of the code to help users understand the underlying physical models (such as governing equations, closure models, and component models), system modeling approaches, numerical discretization and solution methods, and the overall capabilities in SAM. As the code is still under ongoing development, this SAM Theory Manual will be updated periodically to keep it consistent with the state of the development.

Molten Salts Chemistry and Technology

Molten Salts Chemistry and Technology
Author: Marcelle Gaune-Escard,Geir Martin Haarberg
Publsiher: John Wiley & Sons
Total Pages: 632
Release: 2014-05-12
ISBN 10: 1118448820
ISBN 13: 9781118448823
Language: EN, FR, DE, ES & NL

Molten Salts Chemistry and Technology Book Review:

Written to record and report on recent research progresses in the field of molten salts, Molten Salts Chemistry and Technology focuses on molten salts and ionic liquids for sustainable supply and application of materials. Including coverage of molten salt reactors, electrodeposition, aluminium electrolysis, electrochemistry, and electrowinning, the text provides researchers and postgraduate students with applications include energy conversion (solar cells and fuel cells), heat storage, green solvents, metallurgy, nuclear industry, pharmaceutics and biotechnology.

Handbook of Generation IV Nuclear Reactors

Handbook of Generation IV Nuclear Reactors
Author: Igor Pioro
Publsiher: Woodhead Publishing
Total Pages: 940
Release: 2016-06-09
ISBN 10: 0081001622
ISBN 13: 9780081001622
Language: EN, FR, DE, ES & NL

Handbook of Generation IV Nuclear Reactors Book Review:

Handbook of Generation IV Nuclear Reactors presents information on the current fleet of Nuclear Power Plants (NPPs) with water-cooled reactors (Generation III and III+) (96% of 430 power reactors in the world) that have relatively low thermal efficiencies (within the range of 32 36%) compared to those of modern advanced thermal power plants (combined cycle gas-fired power plants – up to 62% and supercritical pressure coal-fired power plants – up to 55%). Moreover, thermal efficiency of the current fleet of NPPs with water-cooled reactors cannot be increased significantly without completely different innovative designs, which are Generation IV reactors. Nuclear power is vital for generating electrical energy without carbon emissions. Complete with the latest research, development, and design, and written by an international team of experts, this handbook is completely dedicated to Generation IV reactors. Presents the first comprehensive handbook dedicated entirely to generation IV nuclear reactors Reviews the latest trends and developments Complete with the latest research, development, and design information in generation IV nuclear reactors Written by an international team of experts in the field

Nuclear Power

Nuclear Power
Author: Pavel Tsvetkov
Publsiher: BoD – Books on Demand
Total Pages: 524
Release: 2011-09-09
ISBN 10: 9533074744
ISBN 13: 9789533074740
Language: EN, FR, DE, ES & NL

Nuclear Power Book Review:

We are fortunate to live in incredibly exciting and incredibly challenging time. Energy demands due to economic growth and increasing population must be satisfied in a sustainable manner assuring inherent safety, efficiency and no or minimized environmental impact. These considerations are among the reasons that lead to serious interest in deploying nuclear power as a sustainable energy source. At the same time, catastrophic earthquake and tsunami events in Japan resulted in the nuclear accident that forced us to rethink our approach to nuclear safety, design requirements and facilitated growing interests in advanced nuclear energy systems. This book is one in a series of books on nuclear power published by InTech. It consists of six major sections housing twenty chapters on topics from the key subject areas pertinent to successful development, deployment and operation of nuclear power systems worldwide. The book targets everyone as its potential readership groups - students, researchers and practitioners - who are interested to learn about nuclear power.

Advances in Molten Slags Fluxes and Salts

Advances in Molten Slags  Fluxes  and Salts
Author: Ramana Reddy,Pinakin Chaubal,P. Chris Pistorius,Uday Pal
Publsiher: Springer
Total Pages: 1373
Release: 2017-01-10
ISBN 10: 3319487698
ISBN 13: 9783319487694
Language: EN, FR, DE, ES & NL

Advances in Molten Slags Fluxes and Salts Book Review:

This collection focuses on ferrous and non-ferrous metallurgy where ionic melts, slags, fluxes, or salts play important roles in industrial growth and economy worldwide. Technical topics included are: thermodynamic properties and phase diagrams and kinetics of slags, fluxes, and salts; physical properties of slags, fluxes, and salts; structural studies of slags; interfacial and process phenomena involving foaming, bubble formation, and drainage; slag recycling, refractory erosion/corrosion, and freeze linings; and recycling and utilization of metallurgical slags and models and their applications in process improvement and optimization. These topics are of interest to not only traditional ferrous and non-ferrous metal industrial processes but also new and upcoming technologies.

Thermodynamics In Nuclear Power Plant Systems

Thermodynamics In Nuclear Power Plant Systems
Author: Bahman Zohuri,Patrick McDaniel
Publsiher: Springer
Total Pages: 724
Release: 2015-04-20
ISBN 10: 3319134191
ISBN 13: 9783319134192
Language: EN, FR, DE, ES & NL

Thermodynamics In Nuclear Power Plant Systems Book Review:

This book covers the fundamentals of thermodynamics required to understand electrical power generation systems, honing in on the application of these principles to nuclear reactor power systems. It includes all the necessary information regarding the fundamental laws to gain a complete understanding and apply them specifically to the challenges of operating nuclear plants. Beginning with definitions of thermodynamic variables such as temperature, pressure and specific volume, the book then explains the laws in detail, focusing on pivotal concepts such as enthalpy and entropy, irreversibility, availability, and Maxwell relations. Specific applications of the fundamentals to Brayton and Rankine cycles for power generation are considered in-depth, in support of the book’s core goal- providing an examination of how the thermodynamic principles are applied to the design, operation and safety analysis of current and projected reactor systems. Detailed appendices cover metric and English system units and conversions, detailed steam and gas tables, heat transfer properties, and nuclear reactor system descriptions.

Reactor Technology

Reactor Technology
Author: Anonim
Publsiher: Unknown
Total Pages: 135
Release: 1972
ISBN 10: 1928374650XXX
ISBN 13: IND:30000089104180
Language: EN, FR, DE, ES & NL

Reactor Technology Book Review:

Nuclear Hydrogen Production Handbook

Nuclear Hydrogen Production Handbook
Author: Xing L. Yan,Ryutaro Hino
Publsiher: CRC Press
Total Pages: 939
Release: 2016-04-19
ISBN 10: 1439810842
ISBN 13: 9781439810842
Language: EN, FR, DE, ES & NL

Nuclear Hydrogen Production Handbook Book Review:

Written by two leading researchers from the world-renowned Japan Atomic Energy Agency, the Nuclear Hydrogen Production Handbook is an unrivalled overview of current and future prospects for the effective production of hydrogen via nuclear energy. Combining information from scholarly analyses, industrial data, references, and other resources, this h

Advances in Materials Science for Environmental and Energy Technologies V

Advances in Materials Science for Environmental and Energy Technologies V
Author: Tatsuki Ohji,Raghunath Kanakala,Josef Matyáš,Navin Jose Manjooran,Gary Pickrell,Winnie Wong-Ng
Publsiher: John Wiley & Sons
Total Pages: 254
Release: 2016-09-27
ISBN 10: 1119324602
ISBN 13: 9781119324607
Language: EN, FR, DE, ES & NL

Advances in Materials Science for Environmental and Energy Technologies V Book Review:

This proceedings volume contains a collection of 20 papers from the following symposia held during the 2015 Materials Science and Technology (MS&T '15) meeting: 7th International Symposium on Green and Sustainable Technologies for Materials Manufacturing Processing Materials for Nuclear Applications and Extreme Environments Materials Issues in Nuclear Waste Management in the 21st Century Nanotechnology for Energy, Healthcare and Industry Materials for Processes for CO2 Capture, Conversion and Sequestration Hybrid Organic – Inorganic Materials for Alternative Energy

Advances in Energy and Environmental Materials

Advances in Energy and Environmental Materials
Author: Yafang Han
Publsiher: Springer
Total Pages: 968
Release: 2018-04-17
ISBN 10: 9811301581
ISBN 13: 9789811301582
Language: EN, FR, DE, ES & NL

Advances in Energy and Environmental Materials Book Review:

This proceedings volume gathers selected papers presented at the Chinese Materials Conference 2017 (CMC2017), held in Yinchuan City, Ningxia, China, on July 06-12, 2017. This book covers a wide range of energy conversion and storage materials, thermoelectric materials and devices, nuclear materials, solar energy materials and solar cells, minerals and oil and gas materials, photocatalytic materials for energy production, eco-materials, and environmental engineering materials. The Chinese Materials Conference (CMC) is the most important serial conference of the Chinese Materials Research Society (C-MRS) and has been held each year since the early 1990s. The 2017 installment included 37 Symposia covering four fields: Advances in energy and environmental materials; High performance structural materials; Fundamental research on materials; and Advanced functional materials. More than 5500 participants attended the congress, and the organizers received more than 700 technical papers. Based on the recommendations of symposium organizers and after peer reviewing, 490 papers have been included in the present proceedings, which showcase the latest original research results in the field of materials, achieved by more than 300 research groups at various universities and research institutes.

Reprocessing and Recycling of Spent Nuclear Fuel

Reprocessing and Recycling of Spent Nuclear Fuel
Author: Robin Taylor
Publsiher: Elsevier
Total Pages: 684
Release: 2015-04-18
ISBN 10: 178242217X
ISBN 13: 9781782422174
Language: EN, FR, DE, ES & NL

Reprocessing and Recycling of Spent Nuclear Fuel Book Review:

Reprocessing and Recycling of Spent Nuclear Fuel presents an authoritative overview of spent fuel reprocessing, considering future prospects for advanced closed fuel cycles. Part One introduces the recycling and reprocessing of spent nuclear fuel, reviewing past and current technologies, the possible implications of Generation IV nuclear reactors, and associated safely and security issues. Parts Two and Three focus on aqueous-based reprocessing methods and pyrochemical methods, while final chapters consider the cross-cutting aspects of engineering and process chemistry and the potential for implementation of advanced closed fuel cycles in different parts of the world. Expert introduction to the recycling and reprocessing of spent nuclear fuel Detailed overview of past and current technologies, the possible implications of Generation IV nuclear reactors, and associated safely and security issues A lucid exploration of aqueous-based reprocessing methods and pyrochemical methods