Fission Of Nuclei Research Articles

Heavy particle radioactivity of superheavy element Z = 126

The concept of heavy particle radioactivity is studied using modified generalised liquid drop model (MGLDM) in the superheavy element Z = 126. The eight different proximity functions and different mass excess values were used to evaluate cluster/HPR. The logarithmic half-lives using different proximity functions and mass excess values are compared with that of experiments. The HPR of 60Ni to 102Ru have been studied in the superheavy region 126306 to 126326. The HPR half-lives has been compared with the different decay modes such as α-decay, β-decay and spontaneous fission. 9 HPR emitters, 4 α emitters, 1 β+ emitter and 7 spontaneous fission nuclei were identified in the superheavy nuclei 126306−314, 126315−318, 126319 and 126320−326 respectively.

Asymmetric and symmetric fission of excited nuclei of Hg180,190 and Pb184,192,202 formed in the reactions with Ar36 and Ca40,48 ions

Background: Observation of asymmetric fission of $^{180}\mathrm{Hg}$ has led to intensive theoretical and experimental studies of fission of neutron-deficient nuclei in the lead region.Purpose: The study of asymmetric and symmetric fission modes of $^{180,190}\mathrm{Hg}$ and $^{184,192,202}\mathrm{Pb}$ nuclei.Methods: Mass-energy distributions of fission fragments of $^{180,190}\mathrm{Hg}$ and $^{184}\mathrm{Pb}$ formed in the $^{36}\mathrm{Ar}+^{144,154}\mathrm{Sm}$ and $^{40}\mathrm{Ca}+^{144}\mathrm{Sm}$ reactions, respectively, at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET and compared with previously measured $^{192,202}\mathrm{Pb}$ isotopes produced in the $^{48}\mathrm{Ca}+^{144,154}\mathrm{Sm}$ reactions. The mass distributions for $^{180,190}\mathrm{Hg}$ and $^{184,192,202}\mathrm{Pb}$ together with old data for $^{187}\mathrm{Ir}, ^{195}\mathrm{Au}, ^{198}\mathrm{Hg}, ^{201}\mathrm{Tl}, ^{205,207}\mathrm{Bi}, ^{210}\mathrm{Po}$, and $^{213}\mathrm{At}$ [J. Nucl. Phys. 53, 1225 (1991)] have been decomposed into symmetric and asymmetric fission modes. The total kinetic-energy distributions for different fission fragment mass regions have been analyzed for $^{180,190}\mathrm{Hg}$ and $^{184}\mathrm{Pb}$.Results: The stabilization role of proton numbers at $Z\ensuremath{\approx}36$, 38, $Z\ensuremath{\approx}45$, 46, and $Z=28/50$ in asymmetric fission of excited preactinide nuclei has been observed. The high ($\ensuremath{\approx}145\text{\ensuremath{-}}\mathrm{MeV}$) and the low ($\ensuremath{\approx}128\text{\ensuremath{-}}\mathrm{MeV}$) energy components have been found in the total kinetic-energy distributions of $^{180,190}\mathrm{Hg}$ fission fragments corresponding to the fragments with proton numbers near $Z\ensuremath{\approx}46$ and $Z\ensuremath{\approx}36$, respectively. In the case of fission of $^{184}\mathrm{Pb}$ only the low-energy component ($\ensuremath{\approx}135\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$) for the fragments with masses corresponding to the proton numbers $Z\ensuremath{\approx}36$ and 46 has been found.Conclusions: The studied properties of asymmetric fission of $^{180,190}\mathrm{Hg}$ and $^{184,192,202}\mathrm{Pb}$ nuclei point out the existence of well deformed proton shell at $Z\ensuremath{\approx}36$ and less deformed proton shell at $Z\ensuremath{\approx}46$.

STATE'S READINESS MOBILITY IN APPLYING NUCLEAR TECHNOLOGY AS ENERY DEVELOPMENT IN LEGAL PERSPECTIVE

The states Nuclear Program is a program to build and utilize nuclear science and technology both in the non-energy sector and in the energy sector for peaceful purposes. Utilization of non-energy in Indonesia has developed quite advanced. The use of nuclear power in every countries covers various fields such as health, research and industry. Indonesia's readiness in implementing nuclear energy is carried out by ratifying international conventions, issuing laws, and issuing regulations from the Nuclear Energy Supervisory Agency, readiness in the field of infrastructure used to strengthen technology, and in Indonesia is committed to reducing 26% of greenhouse gas emissions in the year 2020. A nuclear power plant or nuclear power plant is a thermal power plant that uses one or more nuclear reactors as a heat source. The working principle of a nuclear power plant is almost the same as a steam power plant, using high pressure steam to turn a turbine. The rotation of the turbine is converted into electrical energy. The difference is the heat source used to generate heat. A nuclear power plant uses uranium as its heat source. The fission reaction (fission) of the uranium nucleus produces enormous heat energy. The power of a nuclear power plant ranges from 40 MWe to 2000 MWe, and a nuclear power plant built in 2005 has a power distribution from 600 MWe to 1200 MWe. As of 2015 there are 437 nuclear power plants operating in the world, which in total generate about 1/6 of the world's electrical energy. To date, around 66 nuclear power plants are being built in various countries, including China with 28 units, Russia with 11 units, India with 7 units, the United Arab Emirates with 4 units, South Korea with 4 units, Pakistan and Taiwan with 2 units each. Nuclear power plants are categorized based on the type of reactor used. However, in some plants that have several separate reactor units, it is possible to use reactor types that are fueled such as Uranium and Plutonium.

Cascade exciton model analysis of energetic pion-induced fission of heavy nuclei: Target mass and projectile energy dependence

A data bank of negative and positive (80–1665[Formula: see text]MeV) pion-induced experimental fission cross-sections of heavy nuclei from 119Sn to 238U is compiled using present results and published data from the literature. Corresponding calculations of fission cross-sections, using the cascade exciton model (CEM) are also included in the compilation. Fission cross-sections compiled in the data bank are examined critically. Mass and energy dependences of fission cross-sections are analyzed. Fission cross-sections of 238U targets are the highest and scale down approximately, for other targets studied, with fissility, [Formula: see text]. In the fissility expression, [Formula: see text] and [Formula: see text] are atomic and mass numbers of the target while [Formula: see text] refer to positive and negative pion projectiles. The presented data bank is of interest for students and researchers involved in the investigation of energetic light particle-induced fission of heavy nuclei. Nuclear fission of heavy nuclei has been classified into three regimes. Phenomenological discussion of the fission process is also given.

Self-consistent methods for structure and production of heavy and superheavy nuclei

Self-consistent methods for the structure of heavy and superheavy nuclei are reviewed. The construction and application of energy-density functionals are discussed. The relationship between the self-consistent methods and microscopic-macroscopic approaches is considered on the mean-field level. The extraction of single-particle potentials from the energy-density functional is described. The isotopic dependence of nucleon distributions and its influence on the nucleus–nucleus interaction is analyzed. As a new additional condition we introduce that the energy-density functional must describe the heights of the Coulomb barriers in nucleus–nucleus interaction potentials, thus imposing constraints on the properties of the functional at low matter densities. The self-consistent methods are applied to describe the quasiparticle structure, cluster radioactivity, and fission of the heaviest nuclei. These methods are used to predict the probabilities of \(\beta \)-delayed multi-neutron emission and half-lives of \(\beta \)-decays and electron captures in heavy and superheavy nuclei. The predicted properties of superheavy nuclei are used to estimate the production cross-sections of superheavy nuclei in complete fusion reactions.

Design Implementation and Parallel Operation of High-Current High-Power Multipulse Converters Feeding Nuclear Fuel Simulators

Nuclear reactors are designed to maintain a chain reaction producing a steady flow of neutrons generated by fission of heavy nuclei, such as uranium. They produce thermal energy, which is converted into mechanical energy and ultimately into electrical energy feeding to a grid network. In a nuclear reactor, fuel undergoes various power/temperature transients during normal and off -normal situations. One needs to simulate these transients in experimental facilities for performing variety of reactor engineering and safety related tasks. The facility consists of scaled thermal hydraulic test setup comprising process equipment, instrumented nuclear fuel channel simulator, and high current converters for feeding power equivalent to fission power to those simulators to handle the transients safely in controlled manner. The experimental results are used to generate database of various vital nuclear reactor process parameters under all types of operational transients and off -normal conditions that can be compared with predictions from computer codes thus validating ever-evolving and advanced software. Besides, simulation of severe accidental conditions of nuclear reactor in facility is also necessary for evaluation of thermal hydraulic design safety margin. A low-resistance fuel simulator of identical geometry with power scaling is directly heated by high dc current to simulate fission power for generating experimental database. The converters have capability to generate power/temperature transients for simulating nuclear reactor conditions. This article presents design, functional description, specifications, simulation, hardware implementation of 10 kA, 12-pulse, thyristorized converters powering fuel simulators. The successful implementation of parallel operation of four converters feeding 27 kA current is described in this article.

Total kinetic energy release in the fast neutron induced fission of actinide nuclei

The total kinetic energy (TKE) release in the fast neutron-induced fission of various actinide nuclei was measured for neutron energies for En=2.6-100 MeV at the Weapons Neutron Research facility of the Los Alamos National Laboratory. The data are compared to the GEF model of the fission process. The variances of the TKE distributions appear to decrease with increasing Z and A of the fissioning systems.

Possible ternary fission of super-heavy nuclei

In super-heavy nuclei, we may expect to discover new phenomena because of the strong Coulomb force. One example is the true ternary fission. We study the sequential two binary fission of 300120 and 252Cf that produces three fragments. We use the Metropolis method to estimate the probability of the second fission. The probability of the second fission is 10−4-10−3 for superheavy nuclei while it is 10−7−10−6 for heavy actinide nuclei. The most probable mass division is almost symmetric in the case of 300120. We also demonstrate the applicability of the Metropolis method to a non-equilibrium process by comparing it with the Langevin equation.

Radionuclide Chemistry in Nuclear Facilities Based on Heavy Liquid Metal Coolants: Past, Present and Future.

Heavy liquid metals such as lead and lead bismuth eutectic (LBE) are considered as spallation target material for next-generation neutron sources and as coolant of fast spectrum nuclear reactors that are developed to facilitate more efficient use of nuclear fuel as well as transmutation of long-lived nuclear waste. During the operation of such facilities, the heavy liquid metal will be activated by nuclear reactions. Additionally, fission product radionuclides may be introduced into the liquid metal from leaking fuel pins or by fission of the target nuclei in spallation. The chemical behaviour of these radioactive contaminants in the liquid metal - especially their immediate volatilization or volatilization of formed secondary compounds - may affect the safety of such facilities. The present article summarizes the activities of PSI's Laboratory of Radiochemistry towards a better understanding of the chemistry of potentially hazardous radionuclides in LBE and discusses aspects that need to be addressed in future to support the licensing of heavy liquid metal-based nuclear facilities.

Fission rate of excited nuclei at variable friction in the energy diffusion regime

Presently, it is well established that fission of excited nuclei is a dynamical process being a subject of fluctuations and dissipation. In the literature, there are indications that, at the compact nucleus shapes, the strength of nuclear friction is significantly reduced in comparison with the prediction of the one-body approach. Thus, one can expect that at small deformations the nuclear fission process occurs in the so-called “energy diffusion regime”. The purpose of our present work is to compare an approximate analytical formula for the fission rate in this regime with the quasistationary numerical rate which is exact within the statistical errors. Our calculations demonstrate relatively good agreement between these two rates provided the friction parameter is deformation independent. If one accounts for its deformation dependence, the agreement becomes significantly poorer.

Fission studies using multinucleon transfer reactions

It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions (FFMDs) are measured for each transfer channel, in selected bins of excitation energy. It was found that the mass distributions for all the studied nuclides maintain a double-humped shape up to the high energies that the shell effects are expected to smear out. From a comparison with the dynamical calculation based on the fluctuation-dissipation model, this behavior of the mass distributions was unambiguously attributed to the effect of multichance fission.

Some Thoughts on the Future of the Nuclear Energy Industry

Recent assessments of the strategic prospects of the nuclear energy industry tend to show a somewhat condescending attitude towards fusion, which, regretfully, has grounds given the current state of affairs in nuclear science. However, the analysis of the problems and the potentialities of the fusion of light nuclei and fission of heavy nuclei suggests that a full-scale development of each of the two nuclear technologies inevitably involves the need to overcome some formidable technological, materials science, environmental, and economic problems, some of which may put the feasibility of pursuing these nuclear energy programs at question. At the same time, the physical features of the fission and fusion processes objectively suggest that it may be reasonable to combine the two nuclear technologies within a joint nuclear energy system to enable a greater synergetic effect. This apparently would markedly lessen the problems attendant upon the application of each of the discussed technologies in the course of the full-scale development of nuclear energy.

The study of the properties of spontaneously fissioning transfermium nuclei synthesized in the complete fusion reactions with heavy ions

This report describes a series of experiments aimed on investigating characteristics of spontaneous fission of nuclei in the exotic region of short-lived neutron-deficient isotopes with Z ≥ 100. Unique data on the decay properties of neutron-deficient isotopes 244,246Fm, 250No, 252No, 254Rf and 256Rf produced in the complete fusion reactions with accelerated heavy ions 40Ar + 206,208Pb → 246,248Fm*, 48Ca + 204,206Pb → 252,254No*, 50Ti + 206,208Pb →256,258Rf* were obtained in experiments at the VASSILISSA (SHELS) separator combined with a neutron detector.

Mass-asymmetric fission of Bi205,207,209 at energies close to the fission barrier using proton bombardment of Pb204,206,208

Background: Recent observation of mass-asymmetric fission in neutron-deficient Hg and Pt nuclei has reignited interest in fission fragment mass distributions close to Pb. Investigations at energies close to the fission barrier, where mass-asymmetric fission is expected to be most obvious and the sensitivity to shell effects is maximized, are limited in this mass region.Purpose: To measure fission mass distributions for $^{205,207,209}\mathrm{Bi}$ nuclei at the lowest possible excitation energies to determine how the mass distributions change with excitation energy and the neutron number of the compound nucleus.Method: Proton beams bombarding targets of $^{204,206,208}\mathrm{Pb}$ were used to study the fission of $^{205,207,209}\mathrm{Bi}$ at energies from just above to 10 MeV above their fission barriers. Fission fragments were measured using the CUBE fission spectrometer. Fission fragment mass distributions were determined using a newly developed time difference analysis method. Mass distributions were characterized by triple-Gaussian fits to determine the systematic trends across each isotope with excitation energy.Results: Measured mass distributions of all three Bi isotopes exhibit a component of mass-asymmetric fission at all energies studied. The probability of mass-asymmetric fission decreases significantly with increasing excitation energy, from $\ensuremath{\approx}70$ to $\ensuremath{\approx}40%$ over a 10-MeV range. Comparisons between the three Bi isotopes hint at an increase in the mass-symmetric fission yield with increasing neutron number, which could be due to a decrease in the difference between the symmetric and asymmetric fission barriers. The centroids of the mass-asymmetric peaks suggest that several deformed shell gaps in the fission fragments could be contributing to the presence of the mass-asymmetric fission mode with ${Z}_{\mathrm{light}}\ensuremath{\simeq}38$, ${Z}_{\mathrm{heavy}}\ensuremath{\simeq}45$, and ${N}_{\mathrm{light}}\ensuremath{\simeq}56$ all present in the fission fragments.Conclusions: Measurements of fission mass distributions at the lowest possible excitation energies above the fission barrier provide an excellent platform to investigate the origins of the mass-asymmetric fission mode. Further systematic measurements at these energies offer an opportunity to rigorously test new models of fission in this mass region.

Systematics of the mass-asymmetric fission of excited nuclei from 176Os to 206Pb

The competition between the dominant mass-asymmetric and rarer narrow mass-symmetric fission modes in actinide nuclei are controlled by deformed and spherical shell effects. The low energy fission of 80180Hg was recently observed to be strongly mass-asymmetric, indicating that despite spherical shell gaps in fragments around 4090Zr, the system does not fission mass-symmetrically. Several theoretical approaches have been used to explain this unexpected result.To investigate the underlying mechanism, systematic measurements of fission mass distributions for isotopes of Os, Pt, Hg and Pb, formed in fusion reactions with p, 12C, 32S, 40,48Ca projectiles, have been made for excitation energies above the fission saddle-point (Eeff⁎) between 2.8 and 28.2 MeV. Evidence for mass-asymmetric fission is widespread, manifested as flat topped mass distributions or significant deviations from a single Gaussian shape. The systematic trends seen cannot be attributed to quasifission. Comparing two-Gaussian fits at a wide range of E⁎, it is concluded that the fit centroids reflect the low energy character of mass-asymmetric fission in the sub-lead region.Quantitative comparisons were made with microscopic calculations by Scamps and Simenel (2019) [33] of fission mass-asymmetries attributed to the influence of shell gaps in both neutrons (N=52, 56 for compact octuple deformations) and protons (Z=34 and Z=42, 44, 46 with large quadrupole deformations). For the predominant fission mode in the calculations, having one elongated and one compact fragment, the results are in extremely good agreement with all experimental values. This provides strong support for both the calculations, and the exploration of mass-asymmetric fission systematics through heavy ion fusion reactions. The total kinetic energy distributions for 176Pt and 180Pt do not show any evidence of a low TKE mass-symmetric fission mode, as had been reported for 178Pt by Tsekhanovich et al. (2019) [39].

Ternary Fission Mass Distributions of Superheavy Nuclei Within a Statistical Model

Theoretical models predict the existence of an island of stability at the proton shell closures Z = 114 or 120 or 126 and at the neutron shell closure N = 184 due to the microscopic shell effects. In this article, mass distributions of fragments from ternary fission of superheavy nuclei are investigated with the aid of the statistical theory. We have computed the fission mass distributions for the simultaneous decay into three fragments of nuclei 298Fl, $^{304}_{120}$ X and $^{310}_{126} $ X, at the two excitation energies E∗ = 20 and 50 MeV, with the constraint on one of the fragment to be 50Ca and 72Ni. With the fixed third fragments of mass number A3 = 50, 72, asymmetric breakup (A1 ≠ A2) has a larger ternary fission yield for Z = 114, 120 and 126 isotopes. Predominantly, one of the fragments with the neutron closed-shell nucleus (N ≈ 82, 50) is favoured at higher excitation energies. Subsequently, we have considered the ternary fragmentation of the neutron-rich superheavy elements $^{314}_{120}$ X and $^{320}_{126} $ X again for the same excitation energies and fixed third fragment. Interestingly, for the superheavy nucleus $^{314}_{120}$ X, symmetric fission (A1 ≈ A2) with doubly closed-shell nuclei 132Sn for the third fragment 50Ca is favoured at higher E∗. For the isotope $^{320}_{126} $ X, relative yields of fragments with closed shell increase at higher excitation energy.

Measurement of fragment-mass distributions from fission of At214 following the Be9+Tl205 reaction

Background: The recent surprising experimental discovery of asymmetric fission in the nucleus $^{180}\mathrm{Hg}$ at low excitation energy has renewed interest concerning our understanding of the role of nuclear shell effects in the dynamics of the fission process. New theoretical models have been developed that claim to successfully explain the observed asymmetric fission of $^{180}\mathrm{Hg}$ and also predict the nature of mass distributions of several other preactinide nuclei for which experimental data are scarce.Purpose: We investigated fragment-mass distributions in the fission of the preactinide nucleus $^{214}\mathrm{At}$ at different excitation energies near the Coulomb barrier. The present results were compared with the predictions from a recent state-of-the-art theoretical calculation, as well as with our previous measurement for the nearby nucleus $^{210}\mathrm{Po}$.Methods: A pulsed heavy-ion beam was used in the experiment. Fission fragments were detected with two large-area position-sensitive multiwire proportional counters placed at the folding angle. Mass distributions were extracted from time-of-flight differences and position information ($\ensuremath{\theta},\ensuremath{\phi}$) for the fission fragments.Results: An asymmetry in fragment-mass distribution in the fission of $^{214}\mathrm{At}$ was observed at an excitation energy of $\ensuremath{\approx}31$ MeV, where a shell effect is found to influence the potential energy surface. At higher excitation energies, mass distributions are predominantly symmetric indicating the absence of shell effects.Conclusion: This finding is consistent with the prediction of a recent macroscopic-microscopic dynamical model. However, for the preactinides, static models with nascent fragment shell structure are likely to produce similar results.

Research study of possibility producing radioisotope Mo-99 in the active core of the BN-600 reactor using an irradiated assembly with a high flux of thermal and resonance neutrons

It is fact that production of secondary fuel isotopes (plutonium) is carried out in fast neutron reactors, and the possibility of production of non-fuel radioactive isotopes for use in medicine and industry is being considered. BN-600 has a high power density in the core. This makes it possible to achieve a high rate of fission of target nuclei, which is especially important in the case of the production of radioisotopes, due to their short half-life. To meet the growing demand for isotopes, it is planned to use irradiation devices in high-power sodium fast reactors. This type of irradiation device assumes a massive production of the necessary isotopes. The paper considers the design of irradiation devices for the production of molybdenum-99 isotope in the BN reactor. The presented design of the irradiation assembly contains a moderator in order to combine the advantages of the high neutron flux inherent in fast reactors and the thermal neutron spectrum inherent in thermal reactors.

Effect of nuclear structure and fissility on quasifission

In order to investigate the interplay between nuclear structure (shell closure) and dynamics, fission fragment mass distributions have been measured for reactions $^{35,37}\mathrm{Cl}+^{206,208}\mathrm{Pb}$. These reactions have similar entrance channel parameters except for the number of closed shell configuration in the entrance channel. Fission fragment mass distributions have been measured for these reactions in the energy region close to the Coulomb barrier. No mass-angle correlation was observed in any of the four reactions, indicating the absence of fast quasifission (QF), but mass distributions were wider than that of compound nucleus (CN) fission, which indicates the presence of slow QF. With comparable fissility and deformation values, extra stability against QF was observed for reactions which have more closed shell configurations in the entrance channel. Mass-angle distributions of these reactions do not follow the systematics with respect to mean fissility. A new systematics has been obtained by considering quadrupole deformation of the heavy reaction partner along with the fissility, which explains the absence of mass-angle correlation in the presently measured reactions.

Spontaneous and forced decay of atomic nuclei realized in two stages

The main purpose of the work is to determine the possibility of cluster decays of superheavy atomic nuclei. The universality of the principle of similarity allows you to apply it to the analysis of not studied physical processes. Analogies are observed in forced and spontaneous decays of atomic nuclei. It is shown that in two stages, processes initiated by external influence are realized: fragmentation reactions, forced fission of stable nuclei, and impact radioactivity. Nuclear reactions of fragmentation and forced fission of stable isotopes of lead and bismuth are realized under the action of particles (hadrons) and light atomic nuclei with a kinetic energy of more than 108 eV. Shock radioactivity is observed in the collision of macroobjects having a crystalline structure at speeds of at least ∼1 km/s. Also, in two stages, some radioactive decays of atomic nuclei are realized, including extremely rare cluster decays. Based on the analogies of the processes considered, some cautious predictions are made about the possibility of cluster decays of atomic nuclei in a wide range of atomic masses.