DOCSLIB.ORG

Nuclear Fusion: Targeting Safety and Environmental Goals

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Nuclear Fusion: Targeting Safety and Environmental Goals FEATURES Nuclear fusion: Targeting safety and environmental goals Analyzing fusion power's potential for safe, reliable, and environmentally friendly operation is integral to ongoing research by I or some decades, people have looked to the plant relate to safety andeconomics. This article Franz-Nikolaus process powering the sun — nuclear fusion — as looks at safety aspects of fusion power plant Flakus, John C. an answer to energy problems on Earth. Whether designs, and reviews efforts in safety-related Cleveland, and nuclear fusion can meet our expectations re- areas that are being made through interna- T. J. Dolan mains to be seen: technological problems facing tional co-operative activities. a fusion power plant designer are complex and a fusion power plant has not yet been built. Re- markable progress has been made, however, to- Safety-related goals and considerations ward realizing fusion's potential. Research in fields of nuclear fusion has Reliable predictions of the cost of electric- been pursued in various countries for decades. ity from fusion power cannot be performed The efforts include the JT-60, which has pro- until design details of commercial fusion vided important results for improving plasma power plants have been established. Currently, confinement; the D-IIID tokamak experiment, this cost is not projected to be significantly less which has achieved record values of plasma than the costs of other energy sources. pressure relative to the magnetic field pres- In areas of safety, however, fusion holds sure; and the Tokamak Fusion Test Reactor potential advantages over other energy (TFTR), which has generated 10 million Watts sources. In nearly all studies related to the of thermal power from fusion. The Joint Euro- design of a fusion power plant, safety and pean Torus (JET) is expected to approach environmental considerations are being in- breakeven conditions, where the fusion power creasingly emphasized, and safety goals for generated exceeds the input power. Unre- fusion have been extensively discussed. The solved physics issues, such as plasma purity, safety and environmental goals of a fusion disruptions, and sustainment of current, should power plant design are to protect workers be resolved by the International Thermonu- from radiation, electromagnetic fields, and clear Experimental Reactor (ITER), which is other hazards; the public from radioactive being designed by experts of the European and toxic materials; the environment from Community, Japan, Russian Federation, and pollutants and waste; and the investor from the United States. (See related article begin- damage by accidents. ning on page 16.) The fusion process. At sufficiently high tem- There is confidence that the engineering perature, nearly all light nuclei undergo fusion re- design issues — including those concerning actions and could in principle be used to fuel a superconducting magnets, vacuum systems, fusion power plant. However, technical difficul- cryogenic systems, plasma heating systems, ties increase rapidly with the nuclear charge of plasma diagnostic systems, and blanket cool- the reacting isotopes. For this reason, only deu- ing systems — can eventually be solved. Other terium, tritium and isotopes of helium, lithium, important aspects in designing a fusion power and boron have been proposed in practice. The first generation of fusion power plants will very likely use deuterium-tritium (DT) Mr.Flakus is a senior staff member of the IAEA Department of fuel because it is the easiest to ignite. The main Nuclear Safety, Mr Cleveland is a senior staff member of the reaction product, helium-4, does not pose a IAEA Department of Nuclear Energy; and Mr. Dolan is Head of the Physics Section of the IAEA Division of Physical and health hazard. The principal energy output Chemical Sciences. from a DT fusion event is a 14 MeV neutron. 22 IAEA BULLETIN, 4/1995 FEATURES Nearly all materials become activated to some issued giving preliminary results of the ITER degree by energetic neutron bombardment. safety analysis. Neutron reactions in DT fusion reactors will Fusion power plant safety studies have inevitably create radioisotopes. The principal been evolving for more than 20 years. They are radioactive materials present in a DT fusion steadily adapting to the evolution of interna- reactor will therefore be tritium and neutron- tionally agreed radiation safety concepts and activated structural materials surrounding the requirements. reaction volume. In 1994 the IAEA, jointly with five other Safety-related considerations. Specific international organizations issued revised In- fusion power plant safety studies, which are ternational Basic Safety Standards for Protec- complementary to many other safety studies, tion against Ionizing Radiation and for the include those related to tritium safety, the as- Safety of Radiation Sources. The Basic Safety sessment of tritium releases, activation product Standards — issued jointly with the Food and safety, radioactive waste disposal, and analyses Agriculture Organization (FAO), International of potential accidents and their consequences. Labour Office (ILO), Nuclear Energy Agency The release rate of tritium during plant op- of the Organization for Economic Co-opera- eration has to be kept well within an acceptable tion and Development (OECD/NEA), Pan- safe range. This release of tritium is modeled American Health Organization (PAHO), and by computer codes that account for tritium World Health Organization (WHO) — take permeation through the materials present in the account of new recommendations on radiation power plant. Major tritium research laborato- protection of the International Commission on ries are in Canada, Germany, Italy, Japan, the Radiological Protection (ICRP). A central part Russian Federation, and the United States. of the dose limitation system is the "optimiza- The generation of neutron activation prod- tion of protection" principle. Fusion is a good ucts is not a serious problem if they can be candidate for the successful application of this contained and if they have short half-lives. principle. Optimization is best achieved when They are a byproduct of the fusion reaction, safety assessment is already built into the not a direct reaction product. Therefore, their early design stages of a project. generation in the blanket and structure of the As pointed out earlier, the first fusion power reactor is under the control of the designer and plants will most likely use the DT fuel cycle. can be minimized by proper design and appro- Once a fusion power plant based on the DT priate choice of materials. The use of a variety reaction has been built, advanced fuels could be of low activation materials is being exten- further pursued for energy exploitation. This sively studied. would bring about a lower tritium inventory. There is no potential for a runaway fusion Later fusion power plants may evolve to fuels reaction; indeed, the problem is making the (such as deuterium + 3helium) that generate fusion reaction proceed adequately at all. Vir- fewer neutrons, and hence produce less radioac- tually all hardware problems lead to fusion tivity in surrounding materials. Thus, during the shutdown, and there are inherent limits in any evolution to advanced fuel cycles, the safety ad- case because of the limited amount of fusion vantages of fusion may increase with time. It fuel present and the nature of the fusion reac- may be possible in the future to design power tion. However, a particular focus of work in plants with low enough radionuclide inventories fusion safety is the analysis of various other so that emergency planning and preparedness are potential accidents, such as magnet accidents, unnecessary. and "consequence calculations" are per- formed. For categorization of accidents into event groupings and estimation of the fre- Practical realization of fusion quency of accidents, specific component reli- ability data are required. It has been estimated that an investment of The approach for conducting a general the order of US $50-100 billion is needed to safety analysis for fusion plants is similar to bring fusion power to fruition. The rate of that used for the design of other large nuclear progress in fusion research is limited by the installations. (See box, page 25.) The results funding rate, which is estimated to be about US of safety analyses indicate that fusion power $1.5 billion per year worldwide. plants can meet the desired safety goals. For example, the ESECOM study compared the safety and economic aspects of many fusion * See "Report of the Senior Committee on Environmental, Safety, and Economic Aspects of Magnetic Fusion Energy", reactor designs.* The general safety issues of by J.P. Holdren, D.H. Berwald, R.J. Budnitz, et.al., UCRL- ITER were discussed and a draft report has been 53766 (1989). IAEA BULLETIN, 4/1995 23 FEATURES Currently, expectations are that ITER could begin significant DT operation around Fusion Safety Philosophy 2005-2010, followed by construction of a dem- onstration power plant. A demonstration fusion The fusion safety philosophy now includes the power plant could then begin operation about following concepts: two decades later. If the demonstration reactor is successful, i.e. if sufficient operational experi- • passive systems and inherent safety fea- ence warrants financing of a commercial tures; power plant, then early commercial fusion • fail-safe design; power plants could begin operation by about • reliability (including redundancy of compo-
Load more

Recommended publications
  • Nuclear Energy in Everyday Life Nuclear Energy in Everyday Life
    Nuclear Energy in Everyday Life Nuclear Energy in Everyday Life Understanding Radioactivity and Radiation in our Everyday Lives Radioactivity is part of our earth – it has existed all along. Naturally occurring radio- active materials are present in the earth’s crust, the floors and walls of our homes, schools, and offices and in the food we eat and drink. Our own bodies- muscles, bones and tissues, contain naturally occurring radioactive elements. Man has always been exposed to natural radiation arising from earth as well as from outside. Most people, upon hearing the word radioactivity, think only about some- thing harmful or even deadly; especially events such as the atomic bombs that were dropped on Hiroshima and Nagasaki in 1945, or the Chernobyl Disaster of 1986. However, upon understanding radiation, people will learn to appreciate that radia- tion has peaceful and beneficial applications to our everyday lives. What are atoms? Knowledge of atoms is essential to understanding the origins of radiation, and the impact it could have on the human body and the environment around us. All materi- als in the universe are composed of combination of basic substances called chemical elements. There are 92 different chemical elements in nature. The smallest particles, into which an element can be divided without losing its properties, are called atoms, which are unique to a particular element. An atom consists of two main parts namely a nu- cleus with a circling electron cloud. The nucleus consists of subatomic particles called protons and neutrons. Atoms vary in size from the simple hydro- gen atom, which has one proton and one electron, to large atoms such as uranium, which has 92 pro- tons, 92 electrons.
    [Show full text]
  • Nuclear Energy: Fission and Fusion
    CHAPTER 5 NUCLEAR ENERGY: FISSION AND FUSION Many of the technologies that will help us to meet the new air quality standards in America can also help to address climate change. President Bill Clinton 1 Two distinct processes involving the nuclei of atoms can be harnessed, in principle, for energy production: fission—the splitting of a nucleus—and fusion—the joining together of two nuclei. For any given mass or volume of fuel, nuclear processes generate more energy than can be produced through any other fuel-based approach. Another attractive feature of these energy-producing reactions is that they do not produce greenhouse gases (GHG) or other forms of air pollution directly. In the case of nuclear fission—a mature though controversial energy technology—electricity is generated from the energy released when heavy nuclei break apart. In the case of nuclear fusion, much work remains in the quest to sustain the fusion reactions and then to design and build practical fusion power plants. Fusion’s fuel is abundant, namely, light atoms such as the isotopes of hydrogen, and essentially limitless. The most optimistic timetable for fusion development is half a century, because of the extraordinary scientific and engineering challenges involved, but fusion’s benefits are so globally attractive that fusion R&D is an important component of today’s energy R&D portfolio internationally. Fission power currently provides about 17 percent of the world’s electric power. As of December 1996, 442 nuclear power reactors were operating in 30 countries, and 36 more plants were under construction. If fossil plants were used to produce the amount of electricity generated by these nuclear plants, more than an additional 300 million metric tons of carbon would be emitted each year.
    [Show full text]
  • NETS 2020 Template
    بÀƵƧǘȁǞƧƊǶ §ȲȌǐȲƊǿ ƊƧDzɈȌɈǘƵwȌȌȁƊȁƮȌȁ ɈȌwƊȲȺɈǘȲȌɐǐǘƊƮɨƊȁƧǞȁǐ خȁɐƧǶƵƊȲɈƵƧǘȁȌǶȌǐǞƵȺƊȁƮ ǞȁȁȌɨƊɈǞȌȁ ǞȺ ȺȯȌȁȺȌȲƵƮ Ʀɯ ɈǘƵ ƊDz ªǞƮǐƵ yƊɈǞȌȁƊǶ ׁׂ׀ׂ y0À² ÀǘǞȺ ƧȌȁǏƵȲƵȁƧƵ خׁׂ׀ׂ ةɈǘ׀׃ƊȁƮ ɩǞǶǶƦƵ ǘƵǶƮ ǏȲȌǿȯȲǞǶ ׂ׆ɈǘٌةmƊƦȌȲƊɈȌȲɯ ɩǞǶǶ ƦƵ ǘƵǶƮ ɨǞȲɈɐƊǶǶɯ ȺȌ ɈǘƊɈ ɈǘƵ ƵȁɈǞȲƵ y0À² خƧȌǿǿɐȁǞɈɯǿƊɯȯƊȲɈǞƧǞȯƊɈƵǞȁɈǘǞȺƵɮƧǞɈǞȁǐǿƵƵɈǞȁǐ ǐȌɨخȌȲȁǶخخׁׂ׀ȁƵɈȺׂششبǘɈɈȯȺ Nuclear and Emerging Technologies for Space Sponsored by Oak Ridge National Laboratory, April 26th-30th, 2021. Available online at https://nets2021.ornl.gov Table of Contents Table of Contents .................................................................................................................................................... 1 Thanks to the NETS2021 Sponsors! ...................................................................................................................... 2 Nuclear and Emerging Technologies for Space 2021 – Schedule at a Glance ................................................. 3 Nuclear and Emerging Technologies for Space 2021 – Technical Sessions and Panels By Track ............... 6 Nuclear and Emerging Technologies for Space 2021 – Lightning Talk Final Program ................................... 8 Nuclear and Emerging Technologies for Space 2021 – Track 1 Final Program ............................................. 11 Nuclear and Emerging Technologies for Space 2021 – Track 2 Final Program ............................................. 14 Nuclear and Emerging Technologies for Space 2021 – Track 3 Final Program ............................................. 18
    [Show full text]
  • Nuclear Power
    No.59 z iii "Ill ~ 2 er0 Ill Ill 0 Nuclear Family Pia nning p3 Chernobyl Broadsheet ·, _ I. _ . ~~~~ George Pritchar d speaks CONTENTS COMMENT The important nuclear development since the Nuclear Family Planning 3 last SCRAM Journal was the Government's The CEGB's plans, and the growing opposition, after Sizewell B by go ahead for Sizewell B: the world's first HUGH RICHARDS. reactor order since Chernobyl, and Britain's News 4-6 first since the go ahead was given to Torness Accidents Will Happen 1 and Heysham 2 in 1978. Of great concern is Hinkley Seismic Shocker 8-9 the CEGB's announced intention to build "a A major article on seismic safety of nuclear plants in which JAMES small fanilty• of PWRs, starting with Hinkley GARRETT reveals that Hinkley Point C. At the time of the campaign In the Point sits on a geological fault. south west to close the Hinkley A Magnox Trouble at Trawsfynydd 10-11 station, and .a concerted push in Scotland to A summary of FoE's recent report on increasing radiation levels from prevent the opening of Torness, another Trawsfynydd's by PATRICK GREEN. nuclear announcement is designed to divide Pandora's POX 12 and demoralise the opposition. But, it should The debate over plutonium transport make us more determined. The article on the to and from Dounreay continues by facing page gives us hope: the local PETE MUTTON. authorities on Severnside are joining forces CHERNOBYL BROADSHEET to oppose Hinkley C, and hopefully they will Cock-ups and Cover-ups work closely with local authorities in other "Sacrificed to • • • Nuclear Power" threatened areas - Lothian Region, The Soviet Experience Northumberland, the County Council Coalition "An Agonising Decision• 13 against waste dumping and the Nuclear Free GEORGE PRITCHARD explains why Zones - to formulate a national anti-nuclear he left Greenpeoce and took a job strategy.
    [Show full text]
  • Sources, Effects and Risks of Ionizing Radiation
    SOURCES, EFFECTS AND RISKS OF IONIZING RADIATION United Nations Scientific Committee on the Effects of Atomic Radiation UNSCEAR 2016 Report to the General Assembly, with Scientific Annexes UNITED NATIONS New York, 2017 NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Seventy-first Session, Supplement No. 46 and corrigendum (A/71/46 and Corr.1). The report reproduced here includes the corrections of the corrigendum. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. UNITED NATIONS PUBLICATION Sales No. E.17.IX.1 ISBN: 978-92-1-142316-7 eISBN: 978-92-1-060002-6 © United Nations, January 2017. All rights reserved, worldwide. This publication has not been formally edited. Information on uniform resource locators and links to Internet sites contained in the present publication are provided for the convenience of the reader and are correct at the time of issue. The United Nations takes no responsibility for the continued accuracy of that information or for the content of any external website.
    [Show full text]
  • Uranium (Nuclear)
    Uranium (Nuclear) Uranium at a Glance, 2016 Classification: Major Uses: What Is Uranium? nonrenewable electricity Uranium is a naturally occurring radioactive element, that is very hard U.S. Energy Consumption: U.S. Energy Production: and heavy and is classified as a metal. It is also one of the few elements 8.427 Q 8.427 Q that is easily fissioned. It is the fuel used by nuclear power plants. 8.65% 10.01% Uranium was formed when the Earth was created and is found in rocks all over the world. Rocks that contain a lot of uranium are called uranium Lighter Atom Splits Element ore, or pitch-blende. Uranium, although abundant, is a nonrenewable energy source. Neutron Uranium Three isotopes of uranium are found in nature, uranium-234, 235 + Energy FISSION Neutron uranium-235, and uranium-238. These numbers refer to the number of Neutron neutrons and protons in each atom. Uranium-235 is the form commonly Lighter used for energy production because, unlike the other isotopes, the Element nucleus splits easily when bombarded by a neutron. During fission, the uranium-235 atom absorbs a bombarding neutron, causing its nucleus to split apart into two atoms of lighter mass. The first nuclear power plant came online in Shippingport, PA in 1957. At the same time, the fission reaction releases thermal and radiant Since then, the industry has experienced dramatic shifts in fortune. energy, as well as releasing more neutrons. The newly released neutrons Through the mid 1960s, government and industry experimented with go on to bombard other uranium atoms, and the process repeats itself demonstration and small commercial plants.
    [Show full text]
  • 1 Phys:1200 Lecture 36 — Atomic and Nuclear Physics
    1 PHYS:1200 LECTURE 36 — ATOMIC AND NUCLEAR PHYSICS (4) This last lecture of the course will focus on nuclear energy. There is an enormous reservoir of energy in the nucleus and it can be released either in a controlled manner in a nuclear reactor, or in an uncontrolled manner in a nuclear bomb. The energy released in a nuclear reactor can be used to produce electricity. The two processes in which nuclear energy is released – nuclear fission and nuclear fusion, will be discussed in this lecture. The biological effects of nuclear radiation will also be discussed. 36‐1. Biological Effects of Nuclear Radiation.—Radioactive nuclei emit alpha, beta, and gamma radiation. These radiations are harmful to humans because they are ionizing radiation that have the ability to remove electrons from atoms and molecules in human cells. This can lead to the death or alterations of cells. Alteration of the cell can transform a healthy cell into a cancer cell. The hazards of radiation can be minimized by limiting ones overall exposure to radiation. However, there is still some uncertainty in the medical community about the possibility the effect of a single radioactive particle on the bottom. In other words, are the effects cumulative, or can a single exposure lead to cancer in the body. Exposure to radiation can produce either short term effects appearing within minutes of exposure, or long term effects that may appear in years or decades or even in future generations due to changes in DNA. The effects of absorbing ionizing radiation is measured in a unit called the rem.
    [Show full text]
  • Fusion & High Energy Density Plasma Science
    Fusion & High Energy Density Plasma Science Opportunities using Pulsed Power Daniel Sinars, Sandia National Laboratories Fusion Power Associates Dec. 4-5, 2018 Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. Sandia is the home of Z, the world’s largest pulsed power facility, and its adjacent multi-kJ Z-Beamlet and Z-PW lasers Pulsed power development area Z Periscope ZBL/ZPW Chama ZPW ZBL Chamber Jemez Chamber Chaco Pecos Target Chamber Chaco Chaco Probe Chambers Laser Beam Using two HED facilities, we have demonstrated the scaling of magneto-inertial fusion over factors of 1000x in energy 3 Our fusion yields have been increasing as expected with increased fuel preheating and magnetization Progress since 1st MagLIF in 2014 Demonstrated platform on Omega • Improved laser energy coupling • Improved magnetic field from ~0.3 kJ to 1.4 kJ strength from 9 T to 27 T • Demonstrated 6x improvement • Achieved record MIF yields on in fusion performance, reaching Omega of 5x109 DD in 2018 2.5 kJ DT-equivalent in 2018 4 We believe that Z is capable of producing a fusion yield of ~100 kJ DT-equivalent with MagLIF, though doing it with DT would exceed our safety thresholds for both T inventory & yield Preheat Energy = 6 kJ into 1.87 mg/cc DT § 2D simulations indicate a 22+ MA and 25+ T with 22.6 MA 6 kJ of preheat could produce ~100 kJ 21.1 MA § Presently, we cannot produce these inputs 17.4 MA S.
    [Show full text]
  • NIAC 2011 Phase I Tarditti Aneutronic Fusion Spacecraft Architecture Final Report
    NASA-NIAC 2001 PHASE I RESEARCH GRANT on “Aneutronic Fusion Spacecraft Architecture” Final Research Activity Report (SEPTEMBER 2012) P.I.: Alfonso G. Tarditi1 Collaborators: John H. Scott2, George H. Miley3 1Dept. of Physics, University of Houston – Clear Lake, Houston, TX 2NASA Johnson Space Center, Houston, TX 3University of Illinois-Urbana-Champaign, Urbana, IL Executive Summary - Motivation This study was developed because the recognized need of defining of a new spacecraft architecture suitable for aneutronic fusion and featuring game-changing space travel capabilities. The core of this architecture is the definition of a new kind of fusion-based space propulsion system. This research is not about exploring a new fusion energy concept, it actually assumes the availability of an aneutronic fusion energy reactor. The focus is on providing the best (most efficient) utilization of fusion energy for propulsion purposes. The rationale is that without a proper architecture design even the utilization of a fusion reactor as a prime energy source for spacecraft propulsion is not going to provide the required performances for achieving a substantial change of current space travel capabilities. - Highlights of Research Results This NIAC Phase I study provided led to several findings that provide the foundation for further research leading to a higher TRL: first a quantitative analysis of the intrinsic limitations of a propulsion system that utilizes aneutronic fusion products directly as the exhaust jet for achieving propulsion was carried on. Then, as a natural continuation, a new beam conditioning process for the fusion products was devised to produce an exhaust jet with the required characteristics (both thrust and specific impulse) for the optimal propulsion performances (in essence, an energy-to-thrust direct conversion).
    [Show full text]
  • 2.10. Neutron Activation of Paintings
    2.10. Neutron activation of paintings Possible applications: • Pigment analysis by activation techniques • Neutron radiography by neutron absorption ⇒ Autoradiography Requires neutron irradiation of the entire painting using homogenous neutron flux followed by subsequent point by point raster activation measurement. Technical approach with reactors Neutron guide line is needed for providing sufficient neutron flux (~1014 neutrons/cm2/s) for activation of bulky materials outside the reactor core! 4,7 m shielding door shielding neutrons painting 2.5 m Activation with subsequent X-ray and γ-ray detection 63Cu(n,γ)64Cu, Cu(x) 202Hg(n,γ)203Hg, Hg(x) X-ray data provides pigment position γ-ray data provides pigment characteristics Timescale and Radiation Sensitivity Anthony van Dyck, Saint Rosalie praying for the Plague stricken of Palermo 1624 radiograph Pigment identification by analysis of time dependence for characteristic activity 3rd run Pigment identification by analysis of time dependence for characteristic activity 6th run Pigment identification by analysis of time dependence for characteristic activity 8th run Young man in the background Maryan Wynn Ainsworth et al. Art and Autoradiography; Metropolitan Museum of Art, New York; (1987) 12-18 Van Dyck Self-Portrait Head also visible in X-ray radiograph Self-Portrait of van Dyck 1622 St. Sebastian ca 1649 Painting in the Gemäldegalerie Berlin original by Georges de la Tour (1593-1652) French Court Painter Original in Louvre, question about authorship of copy, George de la Tour himself or by his son Entienne de la Tour? Neutron radiated 109 n/cm2s Neutron induced γ activity is recorded in different time steps: e.g.
    [Show full text]
  • 12 Natural Isotopes of Elements Other Than H, C, O
    12 NATURAL ISOTOPES OF ELEMENTS OTHER THAN H, C, O In this chapter we are dealing with the less common applications of natural isotopes. Our discussions will be restricted to their origin and isotopic abundances and the main characteristics. Only brief indications are given about possible applications. More details are presented in the other volumes of this series. A few isotopes are mentioned only briefly, as they are of little relevance to water studies. Based on their half-life, the isotopes concerned can be subdivided: 1) stable isotopes of some elements (He, Li, B, N, S, Cl), of which the abundance variations point to certain geochemical and hydrogeological processes, and which can be applied as tracers in the hydrological systems, 2) radioactive isotopes with half-lives exceeding the age of the universe (232Th, 235U, 238U), 3) radioactive isotopes with shorter half-lives, mainly daughter nuclides of the previous catagory of isotopes, 4) radioactive isotopes with shorter half-lives that are of cosmogenic origin, i.e. that are being produced in the atmosphere by interactions of cosmic radiation particles with atmospheric molecules (7Be, 10Be, 26Al, 32Si, 36Cl, 36Ar, 39Ar, 81Kr, 85Kr, 129I) (Lal and Peters, 1967). The isotopes can also be distinguished by their chemical characteristics: 1) the isotopes of noble gases (He, Ar, Kr) play an important role, because of their solubility in water and because of their chemically inert and thus conservative character. Table 12.1 gives the solubility values in water (data from Benson and Krause, 1976); the table also contains the atmospheric concentrations (Andrews, 1992: error in his Eq.4, where Ti/(T1) should read (Ti/T)1); 2) another category consists of the isotopes of elements that are only slightly soluble and have very low concentrations in water under moderate conditions (Be, Al).
    [Show full text]
  • Fission and Fusion Can Yield Energy
    Nuclear Energy Nuclear energy can also be separated into 2 separate forms: nuclear fission and nuclear fusion. Nuclear fusion is the splitting of large atomic nuclei into smaller elements releasing energy, and nuclear fusion is the joining of two small atomic nuclei into a larger element and in the process releasing energy. The mass of a nucleus is always less than the sum of the individual masses of the protons and neutrons which constitute it. The difference is a measure of the nuclear binding energy which holds the nucleus together (Figure 1). As figures 1 and 2 below show, the energy yield from nuclear fusion is much greater than nuclear fission. Figure 1 2 Nuclear binding energy = ∆mc For the alpha particle ∆m= 0.0304 u which gives a binding energy of 28.3 MeV. (Figure from: http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucbin.html ) Fission and fusion can yield energy Figure 2 (Figure from: http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucbin.html) Nuclear fission When a neutron is fired at a uranium-235 nucleus, the nucleus captures the neutron. It then splits into two lighter elements and throws off two or three new neutrons (the number of ejected neutrons depends on how the U-235 atom happens to split). The two new atoms then emit gamma radiation as they settle into their new states. (John R. Huizenga, "Nuclear fission", in AccessScience@McGraw-Hill, http://proxy.library.upenn.edu:3725) There are three things about this induced fission process that make it especially interesting: 1) The probability of a U-235 atom capturing a neutron as it passes by is fairly high.
    [Show full text]