Nuclear Reaction

9 Key excerpts on "Nuclear Reaction"

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  Introduction to Radioanalytical Physics

  • G. Deconninck, T. Braun, E. Bujdosó(Authors)
  • 2016(Publication Date)
  • Elsevier

    (Publisher)

  Chapter 1 Nuclear ReactionS 1.1 Introduction The study of low energy Nuclear Reactions constitutes a significant part of nuclear and subnuclear physics and involves many different aspects of the subject. In the interaction of fast ions with a solid sample, Nuclear Reactions can occur between the projectiles and nuclei supposed to be at rest, embedded in solid matter. Two kinds of events can occur, the simple deflection of the projectile by the nucleus (elastic scattering) or a rearrangement of nuclear matter leaving one or both partners in a modified physical state. The essential parameter governing the process is the velocity of the incident particle (often called the projectile). This is related to a more accessible quantity, the energy by 7 ^ 1 . 3 8 4 /--i-lOOcm . sec 1 (1) A (in the non relativistic approximation) where V is the velocity, E the energy in MeV and A the atomic mass number of the projectile. Because of their ease of production and acceleration the most frequently used projectiles are protons (p, A — !), deuterons (d, A = 2), 3 He ions (r, A = 3), 4 He ions (a, A = 4) and heavy ions. The considered range of velocity is roughly: 3 X 1 0 8 < V < 3 X 1 0 9 cm . sec 1 corresponding to low energy Nuclear Reactions where mechanisms are rather well understood. Also a great deal of experimental data exist largely due to the fact that in this energy range ions can be easily produced and detected using standard and relatively inexpensive equipments. For analytical purposes two classes of Nuclear Reactions are consid-ered: nuclear activation and prompt Nuclear Reactions. Nuclear acti-vation and more specifically neutron activation has been used almost since the beginning of the nuclear age. Consequently a great deal of literature, in the form of reviews and text books, already exists on the subject, for which reason it will be only briefly mentioned in this book. Prompt Nuclear Reactions applications are more recent and the subject is still in development.

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  Nuclear and Radiochemistry

  • Jozsef Konya, Noemi M. Nagy(Authors)
  • 2018(Publication Date)
  • Elsevier

    (Publisher)

  Chapter 6

  Nuclear Reactions

  Abstract

  The general aspects, kinetics, and types of Nuclear Reactions and their chemical effects will be discussed in this chapter. The general aspects will include the first Nuclear Reactions, the conservation principles, and the calculation of energy (exoergic and endoergic reactions, threshold energy, and the Coulomb barrier). In kinetics, the activation and the cooling (decay) process will be discussed. The Nuclear Reaction will be classified by the irradiating particle: the basic properties of the Nuclear Reactions with neutral particles (neutrons and gamma photons) and charged particles (protons, deuterons, alpha particles, and heavier nuclei (production of transuranium elements updated to 2017)) will be shown. The basic properties of the different types (the radiochemical properties of the product, energy of the reaction, instrumentation, etc.) of Nuclear Reactions will be sketched as well. The Nuclear Reactions at high temperature will be illustrated, including nucleogenesis, the formation of the elements in the universe. Finally, the chemical effects of Nuclear Reactions will be discussed.

  Keywords

  Nuclear Reactions; kinetics; Nuclear Reactions with neutrons; Nuclear Reactions with charged particles; thermoNuclear Reactions; nucleogenesis; chemical effects of Nuclear Reactions

  The inelastic collision of radiation and the nuclei of a substance may result in the formation of new nuclei. Rutherford observed in 1919 that a proton and a new nucleus, 17 O, form in the reaction of alpha particles with nitrogen (Fig. 6.1 ). This Nuclear Reaction can be described by any chemical reaction:

  N 7 14

  + α =

  O 8 17

  + p

  (6.1)

  (6.1)

  Figure 6.1 A: Vessel for the first Nuclear Reaction used by Rutherford. (A) glass vessel, (B) zinc sulfide scintillation screen, (D) alpha emitter radionuclide (M) microscope.

  Rutherford, E. 1919. Phyl. Mag. 37, 543, https://archive.org/stream/londonedinburg6371919lond#page/542/mode/2up (accessed 10.01.2017) Rutherford (1919) B: Cloud chamber photograph of the first Nuclear Reaction by Rutherford (see Eq. (6.1)

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  Introduction

  • Frank Rösch(Author)
  • 2014(Publication Date)
  • De Gruyter

    (Publisher)

  Whenever the projectile constitutes a nucleon (n or p) or a cluster of nucleons such as the nucleus of deuterium (d), He (e.g. the α-particle) or larger nuclei, and if the kinetic energy of these projectiles is below a limit which would split the target nucleus into many pieces (a type of Nuclear Reaction called “spallation”, see below), nucleons are “transferred” in the course of the reaction to or from the target nucleus. This type of reaction follows a “nucleon transfer mechanism”. It will be discussed in this chapter in detail, because it delivers artificial radionuclides relevant for radio- and nuclear chemistry. The focus is on the radioactive product of the reaction rather than on the smaller particles emitted.

  Nuclear Reactions between two nuclei of chemical elements of masses covering almost the complete range of A, which mainly is the case in heavy element research, are discussed in detail in Chapter 10 of Volume II. Nuclear Reactions occurring between two subatomic particles, which is mainly the situation in nuclear physics and particle physics research, are only briefly mentioned.

  13.2.2 Classification of Nuclear Reactions

  Nuclear Reactions may be categorized by many different criteria. One criterion may be exothermic vs . endothermic. If the projectile does not fuse with the target nucleus, but scatters in an inelastic or elastic way, the processes are called “elastic scattering” and “inelastic scattering” respectively, cf. eqs. (13.3) and (13.4). The initial nucleus thus remains unaltered in terms of its nucleon composition, but either obtains an energetic excitation (inelastic scattering, expressed by *A) or no energy at all (elastic scattering). Another point of view considers the change or exchange of nucleons or nucleon clusters, yielding Nuclear Reaction products of nucleon composition different to that of the target nucleus.

  (13.3)

  (13.4)

  One may further distinguish between naturally occurring and man-made Nuclear Reactions. Some Nuclear Reactions permanently take place naturally in the universe, in particular in stars (such as the fusion of light elements and the genesis of heavier elements) or in supernovae (such as the permanent nuclear synthesis of 26 Al in supernovae as mentioned in Chapter 11). Some naturally occurring Nuclear Reactions take place in the earth’s atmosphere (such as formation of 14

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  The Quantum World of Nuclear Physics

  • Yuri A Berezhnoy(Author)
  • 2005(Publication Date)
  • WSPC

    (Publisher)

  Chapter 5 Nuclear Reactions 5.1 Conservation Laws in Nuclear Reactions The various processes of interaction between nuclei and nuclei or nuclei and other particles are called Nuclear Reactions. They can result from the strong (nuclear) interaction, or from the electromagnetic and weak interactions. The strong interaction can cause a Nuclear Reaction if the distance between particles is on the order of 10~ 15 m, because only at such distances can strong forces act. The electromagnetic interaction is responsible for the Nuclear Reactions between nuclei and photons or charged leptons. The weak interaction causes Nuclear Reactions between nuclei and neutrinos. Nuclear Reactions can change the internal states of colliding particles, and can lead to the creation of new ones. The first artificial Nuclear Reaction was conducted by Rutherford in 1919. For this purpose he used a-particles emitted by a radioactive bismuth iso-tope 214 Bi, then known as RaC. Alpha-particles emitted by that isotope had an energy of about 5.5 MeV. Passing through a tube filled with gaseous ni-trogen, a-particles caused the appearance of new particles whose free path substantially exceeded that of the a-particles. These long-free-path parti-cles were detected by a scintillation screen coated with sulphurated zinc. Rutherford determined that they were protons. Rutherford observed the Nuclear Reaction in which a-particle entered the nitrogen nucleus, adhered, and emitted a proton: 14 N + a — -> 17 O+p. (5.1) Previously unknown, the oxygen isotope 17 O was the first element to be created artificially. These experiments were difficult to perform because the transformation of nitrogen into oxygen occurs very rarely. The twenty 115 116 The Quantum World of Nuclear Physics registered Nuclear Reactions (5.1) required a million a-particles to be emit-ted by bismuth.

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  Nuclear and Radiochemistry

  • Jozsef Konya, Noemi M. Nagy(Authors)
  • 2012(Publication Date)
  • Elsevier

    (Publisher)

  A mass number. It includes the formation of the nuclide by radioactive decays as well.

  Source : Reprinted from Choppin and Rydberg (1980) , with permission from Elsevier.

  6.4 Chemical Effects of Nuclear Reactions

  Of course, the production of a nuclide with a different atomic number itself means a chemical change. In this chapter, however, we do not deal with the direct transformation of the nuclei to other ones, but the subsequent chemical effects of the Nuclear Reactions. These effects are caused by the fact that the energy of the Nuclear Reactions is several orders of magnitude higher than the energy of the chemical bonds. As mentioned in Section 2.2 , the energy of the nuclear processes, including Nuclear Reactions, is in the range of MeV, while the energy of the primary chemical bonds is in the range of eV. The high energy of the Nuclear Reactions obviously results in chemical changes in both the target and the product. In this context, the target and product mean not only the target and product nuclide but also their entire chemical environment.

  The energy of the Nuclear Reaction is not thermal energy; rather, it is the kinetic energy of the nuclide and particles taking in the reaction (Figure 6.7 ). The kinetic energy, however, can be expressed as temperature. Thus, the energy of the Nuclear Reactions means a very high temperature, so the atoms formed in the Nuclear Reactions are frequently called “hot atoms.”

  As mentioned in Section 4.4.1 , an important process during alpha decay is the recoil. This process also takes place in other radioactive (beta and gamma) decays (as discussed in Section 5.4.7 ) and in Nuclear Reactions. The energy of the recoil is higher for the heavier particles. This means that the recoiling energy of the recoiled nucleus decreases as the mass of the emitted particle decreases. However, even the recoiling energy caused by the emission of the lightest-radiation gamma photon can be higher than the energy of the chemical bond. This energy can excite the orbital electrons of the atoms. Depending on the recoiling energy and the atomic number, the inner orbital electrons, as well as the outer orbital electrons, can be excited. The excitation of the inner electrons can result in the phenomena discussed in Sections 4.4.3 and 5.4.4

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  Advanced Nuclear Physics

  • (Author)
  • 2014(Publication Date)
  • Library Press

    (Publisher)

  ________________________ WORLD TECHNOLOGIES ________________________ Chapter- 4 Nuclear Fission An induced fission reaction. A slow-moving neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and releases three free neutrons. In nuclear physics and nuclear chemistry, nuclear fission is a Nuclear Reaction in which the nucleus of an atom splits into smaller parts (lighter nuclei), often producing free neutrons and photons (in the form of gamma rays), as well. Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electro- ________________________ WORLD TECHNOLOGIES ________________________ magnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place). For fission to produce energy, the total binding energy of the resulting elements has to be lower than that of the starting element. Fission is a form of nuclear transmutation because the resulting fragments are not the same element as the original atom. Nuclear fission produces energy for nuclear power and to drive the explosion of nuclear weapons. Both uses are made possible because certain substances called nuclear fuels undergo fission when struck by free neutrons and in turn generate neutrons when they break apart. This makes possible a self-sustaining chain reaction that releases energy at a controlled rate in a nuclear reactor or at a very rapid uncontrolled rate in a nuclear weapon. The amount of free energy contained in nuclear fuel is millions of times the amount of free energy contained in a similar mass of chemical fuel such as gasoline, making nuclear fission a very tempting source of energy. The products of nuclear fission, however, are on average far more radioactive than the heavy elements which are normally fissioned as fuel, and remain so for significant amounts of time, giving rise to a nuclear waste problem.

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  Release Of Thermonuclear Energy By Inertial Confinement, The: Ways Towards Ignition

  Ways Towards Ignition

  • Friedwardt Winterberg(Author)
  • 2010(Publication Date)
  • World Scientific

    (Publisher)

  This roughly explains why there is much more energy stored in atomic nuclei than in electronic shells. 2.2 Nuclear Reactions A Nuclear Reaction between two colliding nuclei has the following sequence of events: 1. After colliding inelastically, the two nuclei merge into one larger nu-cleus, called the compound nucleus. 2. A short time later, typically of the order R/ v ≈ 10 − 21 s ( R ≈ 10 − 12 cm, v ≈ c/ 10), the compound nucleus either decays into several other nuclei, or it decays into its ground state under the emission of gamma radiation. The reaction can be either exo-or endothermic. In many reactions, which have been studied, a small nucleus collides with a much larger one. In most of these cases the atomic number of the large nucleus changes only very little. An exception to this rule is nuclear fission, where the compound nucleus splits up into two large fragments. For high collision energies the Nuclear Reaction cross section is equal to the geometric cross section σ = πR 2 (2.9) with R ≈ 10 − 12 cm, one has σ ≈ 10 − 24 cm 2 . A cross section of 10 − 24 cm 2 is called a barn. For lower energies the cross section can become much larger. This hap-pens near a nuclear resonance energy, the energy of an excited nuclear state of the compound nucleus. In the vicinity of the resonance energy, the lifetime of the compound nucleus can become much larger than R/ v ≈ 10 − 21 s, and is instead of the order / ∆ E , where ∆ E is the width of the resonance. (This 2.2. Nuclear ReactionS 13 is a consequence of the time energy uncertainty relation ∆ E ∆ t ∼ = ). As a result, the cross section can become many times larger than the geometric cross section. Near a resonance with the energy E 0 , the cross section σ ( P, Q ) for a compound nucleus P decaying into the reaction products Q is given by the Breit-Wigner formula σ ( P, Q ) = πλ 2 P (2 + 1) Γ P Γ Q ( E − E 0 ) 2 + Γ 2 / 4 .

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  Chemistry

  The Molecular Nature of Matter

  • Neil D. Jespersen, Alison Hyslop(Authors)
  • 2021(Publication Date)
  • Wiley

    (Publisher)

  The neutrons can generate additional fission events, enabling a nuclear chain reaction. If a critical mass of a fissile isotope is allowed to form, the nuclear chain reaction proceeds out of control, and the material deto- nates as an atomic bomb explosion. Pressurized water reactors are the most commonly used fission reactors for power generation. One major problem with nuclear energy is the storage of radioactive wastes. Thermonuclear fusion joins two light nuclei to form a heavier nucleus with the release of more energy than nuclear fission. A typical reaction combines 2 1 H and 3 1 H to give 4 2 H and a neutron. High tem- peratures and pressures are necessary to initiate the fusion reaction. In stars, gravity is able to contain the high temperature plasma and allow fusion to occur. In a hydrogen bomb, the reaction is initiated by a fission bomb. Scientific and engineering hurdles must still be over- come before fusion can be a viable peaceful energy source. Tools for Problem Solving TOOLS The following tools were introduced in this chapter. Study them carefully so that you can select the appropriate tool when needed. The Einstein equation (Section 20.1) ΔE = Δm 0 c 2 (or often just E = mc 2 ) Balancing nuclear equations (Section 20.3) When balancing a nuclear equation apply the following two criteria: 1. The sums of the mass numbers on each side of the arrow must be equal. 2. The sums of the atomic numbers on each side must be the same. The odd–even rule (Section 20.4) When the numbers of neutrons and protons in a nucleus are both even, the isotope is far more likely to be stable than when both numbers are odd. Law of radioactive decay (Section 20.6) Activity = ΔN ___ Δt = kN Activity has units of disintegrations per second, dps, or Bq. The decay constant, k, is a first-order rate constant with units of s −1 , and the number of atoms of the radionuclide in the sample is represented by N.

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  Modern Physics

  • Kenneth S. Krane(Author)
  • 2020(Publication Date)
  • Wiley

    (Publisher)

  When such isotopes were found, and in particu- lar when they were found in abundances very different from what would be expected from “natural” mineral deposits, the existence of the natural reactor was confirmed. 13.5 FUSION Energy may also be released in Nuclear Reactions in the process of fusion, in which two light nuclei combine to form a heavier nucleus. The energy released in this process is the excess binding energy of the heavy nucleus compared with the lighter nuclei; from Figure 12.4, we see that this process can release energy as long as the final nucleus is less massive than about A = 60. For example, consider the reaction 2 1 H 1 + 2 1 H 1 → 3 1 H 2 + 1 1 H 0 The Q value is 4.03 MeV, and so this Nuclear Reaction liberates about 1 MeV per nucleon, roughly the same as the fission reaction. This reaction can occur when a beam of deuterons is accelerated on to a deuterium target. In order 444 Chapter 13 Nuclear Reactions and Applications to observe the reaction, we must get the incident and target deuterons close enough that the nuclear force can produce the reaction; that is, we must over- come the mutual Coulomb repulsion of the two particles. We can estimate this Coulomb repulsion by calculating the electrostatic repulsion of two deuterons when they are just touching. The radius of a deuteron is about 2 fm, and the electrostatic potential energy of the two charges separated by about 4 fm is about 0.4 MeV. A deuteron with 0.4 MeV of kinetic energy can overcome the Coulomb repulsion and initiate a reaction in which 4.4 MeV of energy (0.4 MeV of incident kinetic energy plus the 4-MeV Q value) is released. Doing this reaction in a typical accelerator, in which the beam currents are typically in the microampere range, would produce only a small amount of energy (of the order of a few watts). To obtain significant amounts of energy from fusion, it is necessary to work with much larger quantities of deuterium.

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