China
Africa
Explore chapters and articles related to this topic
Nuclear Power
Published in Robert Ehrlich, Harold A. Geller, John R. Cressman, Renewable Energy, 2023
Robert Ehrlich, Harold A. Geller, John R. Cressman
The shape of the curve of binding energy suggests a way of extracting nuclear energy during two types of processes: fission and fusion. Very heavy nuclei have less binding energy per nucleon than those closer to iron, and therefore, were a heavy nucleus such as uranium to split (fission) into two lighter ones, the combined mass of the two lighter ones would be less than the original parent nucleus, with the mass loss converted into the released energy. In a similar manner, if two light nuclei were to combine (fuse), energy would also be released by exactly the same argument. To illustrate, consider the d–t fusion reaction, where d and t stand for the hydrogen isotopes known as deuterium and tritium, respectively, which are also often written as 2H and 3H. The d–t reaction can be written as 2H + 3He + 1n, where 1n is a neutron. Given the known respective binding energies of the initial nuclei, i.e., 2.2 and 8.5 MeV, and the final nuclei, i.e., 28.3 and 0 MeV, we find that the reduction in binding energy is 17.6 MeV, so that the mass lost in the reaction is 17.6 MeV/c2, and hence, the energy released is 17.6 MeV. Note that it is convenient here to consider the c2 as simply being part of the units of mass, i.e., MeV/c2.
Radioisotopes: their characterization and interaction with matter
Published in R.J. Pentreath, Nuclear Power, Man and the Environment, 2019
The generation of power from nuclear energy differs from other sources of energy in that it is based upon the inherent instability of the nuclei of particular heavy atoms which have a tendency, or can be induced, to fall apart. It is the opposite of our principal source of energy, the Sun, in which the energy arises from the fusion of the nuclei of light atoms. The power generated from a nuclear reactor is derived from the binding energy of the nuclei of heavy atoms. Some of the binding energy is converted into kinetic energy of nuclear fragments; this becomes manifest, ultimately, in the form of heat. The heat arises from successive collisions of the fragments with other atoms. Unstable atomic nuclei expend energy in a number of ways, for which the all-embracing term radiation is used. Atomic radiations interact with matter in different ways to produce a variety of effects; it is these effects which pose the potential danger of power generation from nuclear energy. But to understand the reasons for this it is first of all necessary to understand something of the nature of the atomic nucleus itself.
Secondary Radiation Production and Shielding at Proton Therapy Facilities
Published in Harald Paganetti, Proton Therapy Physics, 2018
The sum of the inelastic and (n, 2n) cross sections in the energy range <20 MeV is called the nonelastic cross section [10]. The inelastic scattering dominates at lower energies, while the (n, 2n) reactions dominate at higher energies. In an inelastic collision, there is a minimum energy loss that equals the energy of the lowest excited state; however, the energy loss in any inelastic collision cannot be determined exactly. The binding energy of a nucleus is the energy that would be needed to take it apart into its individual protons and neutrons. Typically, there is a large energy loss in a single collision, resulting in the excitation of energy states above the ground state, followed by the emission of gamma rays. The minimum energy loss is equal to the binding energy of the neutron in the (n, 2n) reaction, which produces a large number of lower-energy neutrons, because the energies of the two neutrons that are produced are similar. In high-Z materials, a large amount of elastic scattering takes place, but results in negligible energy loss. However, the mean free path or path length of the neutrons in the shielding material increases, thus providing more opportunities for inelastic and (n, 2n) reactions to occur.
Tl on the Si(111)-
Published in Philosophical Magazine, 2019
Ceren Tayran, Bora Alkan, Mehmet Çakmak
Figure 1(a–f) shows the atomic geometry of H3, T4, H3–T4, T4–H3, rect and hex on the Si(111)-() surface. Due to lattice mismatch between Tl layer and Si substrate, we have modelled that the Tl individual atoms occupy different adsorption sites and arrays. Therefore, we have dealt mainly T and H sites and for the double atomic layers which have been considered as individual atoms in rectangular and hexagonal arrays. These sites and arrays formation can be increased the possibility of different monolayers. In order to clarify stability related to the separated Si and Tl layers. We have calculated binding energies of Tl atom on Si(111)-() surface. The binding energy is determined in the following equations:where , , are the total energies of the relaxed Tl on clean Si(111)-() surface, clean Si(111)-() and Tl atoms with different sites and arrays. The calculated binding energies per unit cell are given in Table 1. A positive higher binding energy shows greater stability.