The radioactive nuclei and in the Cosmos and in the solar system

Abstract The cosmic evolution of the chemical elements from the Big Bang to the present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle of matter recurrently re-processes metal-enriched stellar ejecta into the next generation of stars. The study of cosmic nucleosynthesis and this matter cycle requires the understanding of the physics of nuclear reactions, of the conditions at which the nuclear reactions are activated inside the stars and stellar explosions, of the stellar ejection mechanisms through winds and explosions, and of the transport of the ejecta towards the next cycle, from hot plasma to cold, star-forming gas. Due to the long timescales of stellar evolution, and because of the infrequent occurrence of stellar explosions, observational studies are challenging, as they have biases in time and space as well as different sensitivities related to the various astronomical methods. Here, we describe in detail the astrophysical and nuclear-physical processes involved in creating two radioactive isotopes useful in such studies, $^{26}\mathrm{Al}$ and $^{60}\mathrm{Fe}$ . Due to their radioactive lifetime of the order of a million years, these isotopes are suitable to characterise simultaneously the processes of nuclear fusion reactions and of interstellar transport. We describe and discuss the nuclear reactions involved in the production and destruction of $^{26}\mathrm{Al}$ and $^{60}\mathrm{Fe}$ , the key characteristics of the stellar sites of their nucleosynthesis and their interstellar journey after ejection from the nucleosynthesis sites. This allows us to connect the theoretical astrophysical aspects to the variety of astronomical messengers presented here, from stardust and cosmic-ray composition measurements, through observation of $\gamma$ rays produced by radioactivity, to material deposited in deep-sea ocean crusts and to the inferred composition of the first solids that have formed in the Solar System. We show that considering measurements of the isotopic ratio of $^{26}\mathrm{Al}$ to $^{60}\mathrm{Fe}$ eliminate some of the unknowns when interpreting astronomical results, and discuss the lessons learned from these two isotopes on cosmic chemical evolution. This review paper has emerged from an ISSI-BJ Team project in 2017–2019, bringing together nuclear physicists, astronomers, and astrophysicists in this inter-disciplinary discussion.

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Proposed Solutions to Achieve Nuclear Fusion

Engevista ◽

10.22409/engevista.v19i5.968 ◽

2017 ◽

Vol 19 (5) ◽

pp. 1496

Author(s):

Relly Victoria Virgil Petrescu ◽

Raffaella Aversa ◽

Antonio Apicella ◽

Florian Ion Petrescu

Keyword(s):

Nuclear Reactor ◽

Nuclear Reactions ◽

Nuclear Fusion ◽

Nuclear Fission ◽

Light Nuclei ◽

Fast Neutrons ◽

Fusion Reactions ◽

Nuclear Fusion Reactions ◽

The Masses ◽

Fusion Products

Despite research carried out around the world since the 1950s, no industrial application of fusion to energy production has yet succeeded, apart from nuclear weapons with the H-bomb, since this application does not aims at containing and controlling the reaction produced. There are, however, some other less mediated uses, such as neutron generators. The fusion of light nuclei releases enormous amounts of energy from the attraction between the nucleons due to the strong interaction (nuclear binding energy). Fusion it is with nuclear fission one of the two main types of nuclear reactions applied. The mass of the new atom obtained by the fusion is less than the sum of the masses of the two light atoms. In the process of fusion, part of the mass is transformed into energy in its simplest form: heat. This loss is explained by the Einstein known formula E=mc2. Unlike nuclear fission, the fusion products themselves (mainly helium 4) are not radioactive, but when the reaction is used to emit fast neutrons, they can transform the nuclei that capture them into isotopes that some of them can be radioactive. In order to be able to start and to be maintained with the success the nuclear fusion reactions, it is first necessary to know all this reactions very well. This means that it is necessary to know both the main reactions that may take place in a nuclear reactor and their sense and effects. The main aim is to choose and coupling the most convenient reactions, forcing by technical means for their production in the reactor. Taking into account that there are a multitude of possible variants, it is necessary to consider in advance the solutions that we consider them optimal. The paper takes into account both variants of nuclear fusion, and cold and hot. For each variant will be mentioned the minimum necessary specifications.

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Hot laser fusion or low temperature nuclear reactions? Analysis and current prospects of the first experiments on laser fusion

Radioelectronics Nanosystems Information Technologies ◽

10.17725/rensit.2021.13.059 ◽

2021 ◽

Vol 13 (1) ◽

pp. 59-70

Author(s):

Vladimir I. Vysotskii ◽

◽

Alla A. Kornilova ◽

Mykhaylo V. Vysotskyy ◽

◽

...

Keyword(s):

Laser Plasma ◽

Nuclear Reactions ◽

Nuclear Fusion ◽

High Energy ◽

Laser Fusion ◽

Neutron Generation ◽

Fusion Reactions ◽

Target Composition ◽

High Energy Tail ◽

Nuclear Fusion Reactions

The paper considers the features and quantitative characteristics of the first successful laser experiments on the formation of a thermonuclear plasma and registration of neutrons in nuclear fusion reactions under pulsed irradiation of a LiD crystal. Quantitative analysis shows that the production of neutrons recorded in these experiments is not associated with thermonuclear reactions in hot laser plasma. The most probable mechanism of neutron generation is associated with nuclear reactions at low energies and is due to the formation of coherent correlated states (CCS) of deuterons. In this experiment, such states can be formed in two different processes: due to the effect of a shock wave in the undisturbed part of the target lattice on the vibrational state of deuterium nuclei or when deuterium nuclei with energy of about 500 eV move in the lattice. This part of the deuterium nuclei corresponds to the high-energy "tail" of the Maxwellian distribution of the total flux of particles entering from the laser plasma into the interplanar channel. In this second case, the process of the formation of the CCS is associated with the longitudinal periodicity of the interplanar crystal channel, which is equivalent to a nonstationary oscillator in the own coordinate system of moving particle. The expediency of repeating these experiments is shown, in which, in addition to neutrons, one should expect a more efficient generation of other nuclear fusion products due to low-energy reactions involving lithium isotopes from the target composition.

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Spontaneity of nuclear fusion: a qualitative analysis via classical thermodynamics

Open Research Europe ◽

10.12688/openreseurope.13738.3 ◽

2021 ◽

Vol 1 ◽

pp. 67

Author(s):

Silvano Tosti

Keyword(s):

Thermodynamic Analysis ◽

Reaction Rate ◽

Nuclear Reactions ◽

Nuclear Fusion ◽

Fusion Reaction ◽

Operating Conditions ◽

Fusion Reactions ◽

Simplified Approach ◽

Nuclear Fusion Reactions ◽

Classical Thermodynamics

Background: So far the feasibility of nuclear reactions has been studied only through the evaluation of the reaction rate, which gives us information about the kinetics, while the thermodynamic analysis has been limited to evaluations of the change in enthalpy without any consideration of the change in entropy. Methods: This work examines the thermodynamics of nuclear fusion reactions through a simplified approach. The analysis introduces the thermodynamic study of fission and fusion reactions through their comparison with a chemical process. Results: The main result is that fission reactions are always spontaneous (ΔG < 0) since a lot of energy is released in the form of heat and the system moves spontaneously towards a more disordered state. In contrast, fusion reactions are spontaneous only when the enthalpic contribution of the change in Gibbs energy overcomes the entropic contribution. This condition is verified when the temperature of the process is below a characteristic value T*, calculated as the ratio between the energy corresponding to the mass defect and the change of entropy of the fusion reaction. Conclusions: Due to the unavailability of data related to entropy changes in fusion reactions, only a qualitative thermodynamic analysis has been carried out. Through such analysis, the influence of the operating conditions over the spontaneity of fusion processes has been discussed. The final considerations emphasize the role of the thermodynamics analysis that should be implemented in the current studies that, so far, have been mainly based on the assessment of the reaction rate and exothermicity of fusion reactions.

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Spontaneity of nuclear fusion: a qualitative analysis via classical thermodynamics

Open Research Europe ◽

10.12688/openreseurope.13738.2 ◽

2021 ◽

Vol 1 ◽

pp. 67

Author(s):

Silvano Tosti

Keyword(s):

Thermodynamic Analysis ◽

Reaction Rate ◽

Nuclear Reactions ◽

Nuclear Fusion ◽

Fusion Reaction ◽

Operating Conditions ◽

Fusion Reactions ◽

Simplified Approach ◽

Nuclear Fusion Reactions ◽

Classical Thermodynamics

Background: So far the feasibility of nuclear reactions has been studied only through the evaluation of the reaction rate, which gives us information about the kinetics, while the thermodynamic analysis has been limited to evaluations of the change in enthalpy without any consideration of the change in entropy. Methods: This work examines the thermodynamics of nuclear fusion reactions through a simplified approach. The analysis introduces the thermodynamic study of fission and fusion reactions through their comparison with a chemical process. Results: The main result is that fission reactions are always spontaneous (ΔG < 0) since a lot of energy is released in the form of heat and the system moves spontaneously towards a more disordered state. In contrast, fusion reactions are spontaneous only when the enthalpic contribution of the change in Gibbs free energy overcomes the entropic contribution. This condition is verified when the temperature of the process is below a characteristic value T*, calculated as the ratio between the energy corresponding to the mass defect and the change of entropy of the fusion reaction. Conclusions: Due to the unavailability of data related to entropy changes in fusion reactions, only a qualitative thermodynamic analysis has been carried out. Through such analysis, the influence of the operating conditions over the spontaneity of fusion processes has been discussed. The final considerations emphasize the role of the thermodynamics analysis that should be implemented in the current studies that, so far, have been mainly based on the assessment of the reaction rate and exothermicity of fusion reactions.

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Nuclear astrophysics at Gran Sasso Laboratory: the LUNA experiment

EPJ Web of Conferences ◽

10.1051/epjconf/201817801007 ◽

2018 ◽

Vol 178 ◽

pp. 01007

Author(s):

Francesca Cavanna

Keyword(s):

Cross Section ◽

Direct Measurement ◽

Experimental Approach ◽

Nuclear Reactions ◽

Nuclear Fusion ◽

Nuclear Astrophysics ◽

Fusion Reactions ◽

Primordial Nucleosynthesis ◽

Future Goals ◽

Nuclear Fusion Reactions

LUNA is an experimental approach for the study of nuclear fusion reactions based on an underground accelerator laboratory. Aim of the experiment is the direct measurement of the cross section of nuclear reactions relevant for stellar and primordial nucleosynthesis. In the following the latest results and the future goals will be presented.

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Spontaneity of nuclear fusion: a qualitative analysis via classical thermodynamics

Open Research Europe ◽

10.12688/openreseurope.13738.1 ◽

2021 ◽

Vol 1 ◽

pp. 67

Author(s):

Silvano Tosti

Keyword(s):

Thermodynamic Analysis ◽

Reaction Rate ◽

Nuclear Reactions ◽

Nuclear Fusion ◽

Fusion Reaction ◽

Operating Conditions ◽

Fusion Reactions ◽

Simplified Approach ◽

Nuclear Fusion Reactions ◽

Classical Thermodynamics

Background: So far the feasibility of nuclear reactions has been studied only through the evaluation of the reaction rate, which gives us information about the kinetics, while the thermodynamic analysis has been limited to evaluations of the change in enthalpy without any consideration of the change in entropy. Methods: This work examines the thermodynamics of nuclear fusion reactions through a simplified approach. The analysis introduces the thermodynamic study of fission and fusion reactions through their comparison with a chemical process. Results: The main result is that fission reactions are always spontaneous (ΔG < 0) since a lot of energy is released in the form of heat and the system moves spontaneously towards a more disordered state. In contrast, fusion reactions are spontaneous only when the enthalpic contribution of the change in Gibbs free energy overcomes the entropic contribution. This condition is verified when the temperature of the process is below a characteristic value T*, calculated as the ratio between the energy corresponding to the mass defect and the change of entropy of the fusion reaction. Conclusions: Due to the unavailability of data related to entropy changes in fusion reactions, only a qualitative thermodynamic analysis has been carried out. Through such analysis, the influence of the operating conditions over the spontaneity of fusion processes has been discussed. The final considerations emphasize the role of the thermodynamics analysis that should be implemented in the current studies that, so far, have been mainly based on the assessment of the reaction rate and exothermicity of fusion reactions.

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