This book of proceedings collects the papers presented at the Workshop on Diagnostics for ITER, held at Villa Monastero, Varenna (Italy), from August 28 to September 1, 1995. The Workshop was organised by the International School of Plasma Physics "Piero Caldirola. " Established in 1971, the ISPP has organised over fifty advanced courses and workshops on topics mainly related to plasma physics. In particular, courses and workshops on plasma diagnostics (previously held in 1975, 1978, 1982, 1986, and 1991) can be considered milestones in the history of this institution. Looking back at the proceedings of the previous meetings in Varenna, one can appreciate the rapid progress in the field of plasma diagnostics over the past 20 years. The 1995 workshop was co-organised by the Istituto di Fisica del Plasma of the National Research Council (CNR). In contrast to previous Varenna meetings on diagnostics, which have covered diagnostics in present-day tokamaks and which have had a substantial tutorial component, the 1995 workshop concentrated specifically on the problems and challenges of ITER diagnostics. ITER (the International Thennonuclear Experimental Reactor, a joint venture of Europe, Japan, Russia, and the United States, presently under design) will need to measure a wide range of plasma parameters in order to reach and sustain high levels of fusion power. A list of the measurement requirements together with the parameter ranges, target measurement resolutions, and accuracies provides the starting point for selecting a list of candidate diagnostic systems.

449 one finds that for y = Fo (e) C= :n; V3 [Po (2'Yj) 3 -kjF(i) + (2'Yj)! Fd (2'Yj) 3 -ijF (*m, } 1 ( 14.17) C2 = :n; [ - (2'Yj)! Fd (2'Yj) 3 -ijF(i) + Fo (2'Yj) 3 -~;r(i)J, and if y is to be Go(e), C and Chave the same form with Go (2'Yj) replacing Po (2'Yj) 1 2 and G~(2'Yj) replacing Fd(2'Yj). The values of the functions at eo =2'Yj may be ob- tained from (14.8). 1 J. K. TYSON has employed the modified Hankel functions of order one- third 2 as solutions of (13.4) to obtain expressions for the Coulomb functions for L =0 which converge near e =2'Yj. His results appear as linear combinations of the real and imaginary parts of n ~(x) = (12)!e-;/6 [A;{- x) - iB;(-x)J, (14.18) and its derivatives multiplying power series in x = (e - 2'Yj)j(2'Yj)1. For values 1 away from the turning point for L =0, TYSON has obtained forms for Po{e) and Go(e) which are similar to (13.1) to (13.3). The JWKB approximation is again the leading term, and some higher order corrections are given. Expressions similar to Eqs. (14.11) and (14.12) have been obtained by T.D. 3 NEWTON employing the integral representation of (4.4). His results give re- presentations of FL(e), Gde) in the vicinity of e=2'Yj [whereas (14.11), (14.12) converge near e=eLJ when L

The Erice International School of Fusion Reactor Techno logy held its 1981 course on - Unconventional Approaches to Fusion - in combination with the IAEA Technical Committee meeting on - Critical Analysis of Alternative Fusion Concepts -. The two events took place in the second half of March with an overlap of a few days only. The present proceedings include the first week's papers; those presented during the second week will be summarised in Nuclear Fusion. Right from the beginning of the course, and in particular In R. Carruthers' opening talk, it was clear that an uncon ventional approach was considered stimulating insofar as its con ception presented advantageous aspects with respect to the To kamak. Indeed the Tokamak was recognized as an - imper fect frame of reference- (K. H. Schmitter) in the sense that, al though it deserves to be considered as a frame of reference for the other devices because it is the most advanced in the scientific demonstration of controlled thermonuclear fusion, as a fusion reactor, however, the Tokamak does not seem to be completely satisfactory either from an economic or from an operational point of view, if compared with that - enticing ogre -, the proven fission reactor (less enticing to the public). Comparison of a Tokamak reactor with a PWR can be founded on considerations of such a basic nature that it becomes almost automatic to ask how far the various unconventional ap proaches to fusion are exempt from the Tokamak's drawbacks."

A beam of ions in the fonn of "canal rays" was first observed in 1886 by E. Goldstein. The first ion source was invented by J. J. Thomson in 1910. This ion source became the basis for the first widespread application of ion sources in mass spectrographs and mass spectrometers. The second important application of ion sources is ion accelerators, which since the beginning of the 1930s have been employed in research on nuclear reactions and are now used in industry and medicine. A third application of ion sources is in systems for isotope separation and re search on the interaction of atomic particles with solids (1940s). The result of this research and development is the use of ion sources in semiconductor doping, decontamination of surfaces, and micromachining of surfaces (1960s and' 1970s), which is a fourth area of applications for ion sources. The heating of plasmas in magnetic confinement devices to thennonuclear temperatures (100-1000 MK) with the aid of megawatt beams of hydrogen and deuterium ions and atoms has become a fifth promising area of application for ion sources which can produce ion beams with steady-state currents of up to 100 A. Finally, experimental and industrial research are under way on the alloying of metals and the fabrication of coatings which greatly improve the physical and chemical properties of metals. These coatings can increase the hardness, high temperature corrosion resistance, and wear resistance of metals, and can enhance or reduce friction, etc."

A survey of recent developments in the field of plutonium disposal by the application of advanced nuclear systems, both critical and subcritical. Current national R&D plans are summarized. The actinide-fuelled critical reactors are associated with control problems, since they tend to have a small delayed neutron fraction coupled with a small Doppler effect and a positive void coefficient. Current thinking is turning to accelerator-driven subcritical systems for the transmutation of actinides. The book's conclusion is that the various systems proposed are technically feasible, even though not yet technically mature. The book presents a unique summary and evaluation of all relevant possibilities for burning surplus plutonium, presented by experts from a variety of different disciplines and interests, including the defence establishment. The obvious issue - the non-proliferation of nuclear weapons - is vital, but the matter represents a complex technological challenge that also requires an assessment in economic terms.

This second volume of the Charged Particle Traps deals with the rapidly expanding body of research exploiting the electromagnetic con?nement of ions, whose principles and techniques were the subject of volume I. These applications include revolutionary advances in diverse ?elds, ranging from such practical ?elds as mass spectrometry, to the establishment of an ult- stable standard of frequency and the emergent ?eld of quantum computing made possible by the observation of the quantum behavior of laser-cooled con?nedions. Bothexperimentalandtheoreticalactivity intheseapplications has proliferated widely, and the number of diverse articles in the literature on its many facets has reached the point where it is useful to distill and organize the published work in a uni?ed volume that de?nes the current status of the ?eld. As explained in volume I, the technique of con?ning charged particles in suitable electromagnetic ?elds was initially conceived by W. Paul as a thr- dimensional version of his rf quadrupole mass ?lter. Its ?rst application to rf spectroscopy on atomic ions was completed in H. G. Dehmelt's laboratory where notable work was later done on the free electron using the Penning trap. The further exploitation of these devices has followed more or less - dependently along the two initial broad areas: mass spectrometry and high resolution spectroscopy. In volume I a detailed account is given of the theory of operation and experimental techniques of the various forms of Paul and Penning ion traps.

This book is intended to provide an introduction to the basic principles of nuclear fission reactors for advanced undergraduate or graduate students of physics and engineering. The presentation is also suitable for physicists or engineers who are entering the nuclear power field without previous experience with nuclear reactors. No background knowledge is required beyond that typically acquired in the first two years of an undergraduate program in physics or engineering. Throughout, the emphasis is on explaining why particular reactor systems have evolved in the way they have, without going into great detail about reactor physics or methods of design analysis, which are already covered in a number of excellent specialist texts. The first two chapters serve as an introduction to the basic physics of the atom and the nucleus and to nuclear fission and the nuclear chain reaction. Chapter 3 deals with the fundamentals of nuclear reactor theory, covering neutron slowing down and the spatial dependence of the neutron flux in the reactor, based on the solution of the diffusion equations. The chapter includes a major section on reactor kinetics and control, including'tempera ture and void coefficients and xenon poisoning effects in power reactors. Chapter 4 describes various aspects offuel management and fuel cycles, while Chapter 5 considers materials problems for fuel and other constituents of the reactor. The processes of heat generation and removal are covered in Chapter 6.

25 Die Ventile leiten nur wahrend einer sehr kurzen Zeit, namlich dann, wenn das Potential der Anode positiv gegentiber der Kathode ist. Fig. 24 zeigt eine dreistufige Anordnung. Unter der Annahme idealer Ventile und unter Vernach- lassigung der Streukapazitaten stellen sich an den Knotenpunkten 3, 2, 1 und 3*,2*,1* die in Fig. 25 wiedergegebenen Spannungen ein. Der hier dargestellte, idealisierte Generator liefert eine Leerlaufspannung von 6 U , wobei mit U o o die Amplitude der Transformatorspannung Uocoswt bezeichnet ist. fJ) Der Kaskadengenerator bei Belastung. Wird der Kaskadengenerator durch einen Widerstand oder durch ein Beschleunigungsrohr belastet, so sinkt natur- 8!.1o ~-------~-----0 u/;!.Io r-------"-L---7"c----~L--0 J!.Io Ig / ] !.Iocoswt Fig. 25. Leerlau!spannungen beim Generator in Fig. 24. Fig. 26. Der belastete Kaskadengenerator. gemaB die Ausgangsspannung, und zwar umso starker, je groBer der Belastungs- strom Ig ist. Unter Ig wollen wir den vom Generator gelieferten, arithmetischen Mittelwert des Stromes, also den abgegebenen Gleichstrom verstehen. Wahrend einer Periode lit der Wechselspannung wird der Glattungssaule somit die Ladung Q= Ig (11.1) f entzogen. Falls ein stationarer Zustand bestehen solI, muB diese Ladung periodisch wieder zugeftihrt werden. Dies geschieht dadurch, daB wahrend einer Halbwelle der Wechselspannung die Ladung Q von den Punkten 3* nach 3, bzw. 2* nach 2 und 1 * nach 1 flieBt, wahrend in der andern Halbwelle die Ladung Q von Erde nach 3 * bzw. von 3 nach 2* und von 2 nach 1 * transportiert wird.

This book explains how society will face an energy crisis in the coming decades owing to increasing scarcity of fossil fuels and climate change impacts. It carefully explores this coming crisis and concisely examines all of the major technologies related to energy production (fossil fuels, renewables, and nuclear) and their impacts on our society and environment. The author argues that it is wrong to pit alternatives to fossil fuels against each other and proposes that nuclear energy, although by no means free of problems, can be a viable source of reliable and carbon-free electricity. He concludes by calling for a diversified and rational mix of electricity generation in order to mitigate the effects of the energy crisis. Throughout, the book is spiced with science, history, and anecdotes in a way that ensures rewarding reading without loss of rigor.

This book contains the lectures and the concluding discussion of the "Seminar on Safety, Environmental Impact, and Economic Prospects of Nuclear Fusion," which was held at Erice, August 6-12, 1989. In selecting the contributions to this 9th meeting held by the International School of Fusion Reactor Technology at the E. Majorana Center for Scientific Cul ture in Erice, we tried to provide a comprehensive coverage of the many interre lated and interdisciplinary aspects of what ultimately turns out to be the global acceptance criteria of our society with respect to controlled nuclear fusion. Consequently, this edited collection of the papers presented should provide an overview of these issues. We thus hope that this book, with its extensive subject index, will also be of interest and help to nonfusion specialists and, in general, to those who from curiosity or by assignment are required to be informed on these as pects of fusion energy."

MOX fuel, a mixture of weapon-grade plutonium and natural or depleted uranium, may be used to deplete a portion of the world's surplus of weapon-grade plutonium. A number of reactors currently operate in Europe with one-third MOX cores, and others are scheduled to begin using MOX fuels in both Europe and Japan in the near future. While Russia has laboratory-scale MOX fabrication facilities, the technology remains under study. No fuels containing plutonium are used in the U.S. The 25 presentations in this book give an impressive overview of MOX technology. The following issues are covered: an up to date report on the disposition of ex-weapons Pu in Russia; an analysis of safety features of MOX fuel configurations of different reactor concepts and their operating and control measures; an exchange of information on the status of MOX utilisation in existing power plants, the fabrication technology of various MOX fuels and their behaviour in practice; a discussion of the typical national approaches by Russia and the western countries to the utilisation of Pu as MOX fuel; an introduction to new ideas, enhancing the disposition option of MOX fuel exploitation and destruction in existing and future advanced reactor systems; and the identification of common research areas where defined tasks can be initiated in cooperative partnership.

"International Energy Forum 1999" was held in Washington D.C. during November 5-6, 1999 in the Hyatt Regency Hotel in Crystal City. Once again the main topic was Nuclear Energy. Various papers presented contained pros and cons of Nuclear Energy for generating electricity. We were aiming to clarify the often discussed subject matter of the virtues of Nuclear Energy with regard to Global Warming as compared to using fossil fuels for the generation of electricity. The latter is also currently the only way to operate our means of transportation like automobiles, planes etc. Therefore emission into the atmosphere of greenhouse gases constitutes the main source of Global Warming, which is absent in the case of Nuclear Energy. These arguments are often put forward to promote the use of Nuclear Energy. However not all is well with the Nuclear Energy. There are the questions of the waste problem so far unsolved, safety of Nuclear Reactors is not guaranteed to the extent that they are inherently safe. If we aim to construct inherently safe reactors, then the economics of a Nuclear Reactor makes it unacceptable.

Plasma-Material Interaction in Controlled Fusion deals with the specific contact between the fourth state of matter, i.e. plasma, and the first state of matter, i.e. a solid wall, in controlled fusion experiments. A comprehensive analysis of the main processes of plasma-surface interaction is given together with an assessment of the most critical questions within the context of general criteria and operation limits. It is shown that the choice of plasma-facing materials can be reduced to a very limited list of possible candidates. Plasma-Material Interaction in Controlled Fusion emphasizes that a reliable solution of the material problem can only be found by adjusting the materials to suitable plasma scenarios and vice versa.

The Advanced Research Workshop on "Nuclear Submarine Decommissioning and Related Problems" was held at the Russian Academy of Sciences in Moscow, Russia on June 19-22, 1995. On June 17 and 18, 1995 some of the workshop participants visited the Zwezdochka Shipyard at Severodvinsk which is a repair and dismantlement facility for Russian nuclear submarines. Attendance at the workshop was approximately 115 with participants from Russia, United States, France, Norway, Canada, Denmark, Sweden, Estonia, and Germany. The workshop was sponsored by the Disarmament Panel of North Atlantic Treaty Organization (NATO) Science Committee. The sponsorship and the financial support of NATO is gratefully acknowledged. The workshop was organized in Russia by the Nuclear Safety Institute of the Russian Academy of Sciences (IBRAE). The efforts of many individuals from IBRAE in producing both a technically challenging workshop and an almost flawless one are also gratefully acknowledged. In addition, the support of the Russian Academy of Sciences, the State Committee of the Russian Federation on Defense Technologies, the Ministry of the Russian Federation on Atomic Energy, the Navy of the Russian Federation, and the United States Department of Energy is acknowledged. xi CURRENT STATUS OF NUCLEAR SUBMARINE DECOMMISSIONING PROBLEMS OF NUCLEAR SUBMARINE DECOMMISSIONING AND RECYCLING N. I. SHUMKOV State Committee for Defense Industry (Goseomoboronprom) Moscow, Russia 1. General Description of the Problem Undoubtedly, the problem of nuclear submarine decommissioning and recycling has been worrying Russian civil and military specialists involved in development, building and operation of submarines for many years.

Fuzzy systems and soft computing are new computing techniques that are tolerant to imprecision, uncertainty and partial truths. Applications of these techniques in nuclear engineering present a tremendous challenge due to its strict nuclear safety regulation. The fields of nuclear engineering, fuzzy systems and soft computing have nevertheless matured considerably during the last decade. This book presents new application potentials for Fuzzy Systems and Soft Computing in Nuclear Engineering. The root of this book can be traced back to the series of the first, second and third international workshops on Fuzzy Logic and Intelligent Technologies in Nuclear Science (FUNS), which were successfully held in Mol, September 14-16, 1994 (FLINS'94), in Mol, September 25-27, 1996 (FLINS'96), and in Antwerp, September 14-16, 1998 (FLINS'98). The conferences were organised by the Belgian Nuclear Research Centre (SCKeCEN) and aimed at bringing together scientists, researchers, and engineers from academia and industry, at introducing the principles of fuzzy logic, neural networks, genetic algorithms and other soft computing methodologies, to the field of nuclear engineering, and at applying these techniques to complex problem solving within nuclear industry and related research fields. This book, as its title suggests, consists of nuclear engineering applications of fuzzy systems (Chapters 1-10) and soft computing (Chapters 11-21). Nine pertinent chapters are based on the extended version of papers at FLINS'98 and the other 12 chapters are original contributions with up-to-date coverage of fuzzy and soft computing applications by leading researchers written exclusively for this book."

The handling of actinides and actinide-based materials provides significant technological challenges due to the toxicity and radioactivity associated with these materials. These challenges are particularly apparent in the nuclear power industry. Under normal operation, a reactor can produce a significant amount of spent fuel requiring subsequent containment for geologic times, and under accident conditions it can release lethal doses of radioactive material to the environment. Inevitably, radioactive material will enter the environment, necessitating as complete an understanding as possible of its behavior. An understanding of the interaction between actinides and the environment must be based on a knowledge of their basic physical and chemical properties. To date, although there is general agreement on the principles for waste disposal, no facility has been built for the long term disposal of high level radioactive waste from either normal reactor operations or from accidental catastrophes. This makes it most important for the scientific and technical community to develop the necessary cross-disciplinary understanding that will help us implement safe and secure waste management, accident remediation and accident prevention systems.

This second edition is a thoroughly revised, updated and expanded version of a classic text, with lots of new material on electronic signal creation, amplification and shaping. It 's still a thorough general introduction, too, to the theory and operation of drift chambers. The topics discussed include the basics of gas ionization, electronic drift and signal creation and discuss in depth the fundamental limits of accuracy and the issue of particle identification.

Plasma Physics: Confinement, Transport and Collective Effects provides an overview of modern plasma research with special focus on confinement and related issues. Beginning with a broad introduction, the book leads graduate students and researchers - also those from related fields - to an understanding of the state-of-the-art in modern plasma physics. Furthermore, it presents a methodological cross section ranging from plasma applications and plasma diagnostics to numerical simulations, the latter providing an increasingly important link between theory and experiment. Effective references guide the reader from introductory texts through to contemporary research. Some related exercises in computational plasma physics are supplied on a special web site

This volume provides an extensive overview of radiation effects on integrated circuits, offering major guidelines for coping with radiation effects on components. It contains a set of chapters based on the tutorials presented at the International School on Effects of Radiation on Embedded Systems for Space Applications (SERESSA) that was held in Manaus, Brazil, November 20-25, 2005.

Over the last quarter of this century, revolutionary advances have been made both in kind and in precision in the application of particle traps to the study of thephysics of charged particles, leading to intensi?ed interest in, and wide proliferation of, this topic. This book is intended as a timely addition to the literature, providing a systematic uni?ed treatment of the subject, from the point of view of the application of these devices to fundamental atomic and particle physics. Thetechniqueofusingelectromagnetic?eldstocon?neandisolateatomic particles in vacuo, rather than by material walls of a container, was initially conceivedbyW.Paulintheformofa3Dversionoftheoriginalrfquadrupole mass ?lter, for which he shared the 1989 Nobel Prize in physics [1], whereas H.G. Dehmelt who also shared the 1989 Nobel Prize [2] saw these devices (including the Penning trap) as a way of isolating electrons and ions, for the purposes of high resolution spectroscopy. These two broad areas of appli- tion have developed more or less independently, each attaining a remarkable degree of sophistication and generating widespread interest and experimental activity.

Nuclear energy obtained from thermonuclear fusion of light nuclei is a goal to which an increasing world-wide effort is being committed. The demands on energy reserves and resources are continually increasing as ever more coun tries achieve modern industrial status. All projections agree that conventional means of energy production must be supplemented and indeed supplanted by new methods. Only the date at which the transition becomes imperative is subject to debate. The promise of fusion energy ultimately to pro vide a clean, cheap, dependable and potentially inexhaustible energy source augurs well for the future of the human race. If there were illusions at the start of the quest for controlled thermonuclear power that solutions would be easily found, the past two decades have dlspelled them. Unwarranted optimism has been replaced by a realistic recognition of the immense scientific and technological challenges that arise in bringing about practical fusion energy. Broadly speaking, problems can be put into two categories--those having to do with heating the fuel to thermonuclear temperatures at high enough particle densities and for sufficiently long confine ment times to yield a net power return and those having to do with the actual construction of a power producing fusion reactor."

Nuclear engineering plays an important role in various industrial, health care, and energy processes. Modern physics has generated its fundamental principles. A growing number of students and practicing engineers need updated material to access the technical language and content of nuclear principles.

"Nuclear Principles in Engineering, Second Edition" is written for students, engineers, physicians and scientists who need up-to-date information in basic nuclear concepts and calculation methods using numerous examples and illustrative computer application areas.

This new edition features a modern graphical interpretation of the phenomena described in the book fused with the results from research and new applications of nuclear engineering, including but not limited to nuclear engineering, power engineering, homeland security, health physics, radiation treatment and imaging, radiation shielding systems, aerospace and propulsion engineering, and power production propulsion.

This book provides a training course for I and C maintenance engineers in power, process, chemical, and other industries. It summarizes all the scattered literature in this field. The book compiles 30 years of knowledge gained by the author and his staff in testing the I and C systems of nuclear power plants around the world. It focuses on process temperature and pressure sensors and the verification of these sensors' calibration and response time.

A major part of this book is based on work performed by several of the national organizations that are responsible for disposal of radioactive waste from nuclear reactors, with the Author involved in the research as well in the reporting. He is greatly indebted to the organizations and to their representatives that were engaged in the projects, and to the European Commission, represented by Mr Christophe Davies, that supported the work ?nancially and otherwise. Mr Davies' services are gratefully acknowledged. The author also expresses his thanks to the following p- sons who assisted in various ways in the preparation of the book: Christer S- mar, Swedish Nuclear Fuel and Waste Management Co (SKB), Sweden; Wolf S- dler, Agence National pour la gestion des Dechets Radioactifs (ANDRA), France; Jan Verstricht, Studiecentrum voor Kernenergie-Centre d'Etude de l'ener gie Nuc- are (SCK-CEN), Belgium; and Tilmann Rothfuchs, Gesellschaft fur ] Anlagen- und Reaktorsicherheit GmbH (GRS), Germany. Lund, January 2008 Roland Pusch v Acknowledgment The author expresses his thanks to the following persons who assisted in va- ous ways in the preparation of the book: Christer Svemar, Swedish Nuclear Fuel and Waste Management Co (SKB), Sweden; Wolf Seidler, Agence National pour la gestion des Dechets Radioactifs (ANDRA), France, and Tilmann Rothfuchs, Gesellschaft fur ] Anlagen- und Reaktorsicherheit GmbH (GRS), Germany. vii Contents Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 National and International Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Basic Principle of Final Storage of Hazardous Waste . . . . . . . . . . . . . . . . . . 2 TheCROPProject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Crystalline Rock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 SaltRock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Argillaceous Rock and Clastic Clay. . . . . . . . . . . . . . . . . . . . . . . . . . ."

The nuclear thermal hydraulic is the science providing knowledge about the physical processes occurring during the transferring the fission heat released in structural materials due to nuclear reactions into its environment. Along its way to the environment the thermal energy is organized to provide useful mechanical work or useful heat or both. Chapter 1 contains introductory information about the heat release in the re- tor core, the thermal power and thermal power density in the fuel, structures and moderator, the influence of the thermal power density on the coolant temperature, the spatial distribution of the thermal power density. Finally some measures are introduced for equalizing of the spatial distribution of the thermal power density. Chapter 2 gives the methods for describing of the steady and of the transient temperature fields in the fuel elements. Some information is provided regarding influence of the cladding oxidation, hydrogen diffusion and of the corrosion pr- uct deposition on the temperature fields. Didactically the nuclear thermal hydraulic needs introductions at different level of complexity by introducing step by step the new features after the previous are clearly presented. The followed two Chapters serve this purpose. Chapter 3 describes mathematically the "simple" steady boiling flow in a pipe. The steady mass-, momentum- and energy conservation equations are solved at different level of complexity by removing one after the other simplifying assu- tions. First the idea of mechanical and thermodynamic equilibrium is introduced.