Production of neutron-rich actinide isotopes in isobaric collisions via multinucleon transfer reactions

We systematically calculated the multinucleon transfer reactions of ^(208)Os,^(208)Pt,^(208)Hg,^(208)Pb,^(208)Po,^(208)Rn,^(208)Ra,and ^(132,136) Xe when bombarded on ^(232) Th and ^(248) Cm at Coulomb barrier energies within the dinuclear system model.These results are in good agreement with the available experimental data.The influence of Coulomb and shell effects on actinide production in these reactions has been rigorously studied.We calculated and analyzed the potential energy surface (PES) and total kinetic energy (TKE) mass distributions for the reactions involving ^(208)Hg,^(208)Pb,and ^(208) Po with ^(248) Cm and ^(232)Th.The PES and TKE spectra shed light on the fragment formation mechanisms in multinucleon transfer reactions,with clear indications of isospin and shell effects.The production cross sections for multinucleon transfer products show a strong dependence on isobar projectiles with a mass number A=208.Isobar projectiles with high N/Z ratios are advantageous for generating neutron-rich target-like fragments.Conversely,products induced by isobar projectiles with larger charge numbers tend to shift toward proton-rich regions.The intertwining of the Coulomb potential and shell effect is evident in the production cross sections of actinide isotopes.Drawing from reactions induced by radioactive projectiles,we anticipate the discovery of several new actinide isotopes near the nuclear drip lines,extending our reach into the superheavy nuclei domain.

Description and Prediction of the Solid Solubilities of Binary Alloys Based on the Actinide Metals

The solid solubilities of 207 binary alloys based on the three actinide metals (Th, U and Pu) at room tem- perature are studied with the two theoretical schemes suggested by one of the present authors (ZBW).The re- sults show that the soluble elements can be distinguished from the insoluble ones by a parabola y_1=a--bx^2 or an ellipse (x_2,-m)~2/c^2+(y_2-n)~2/d^2=l with the total reliabilities of 87.9% and 92.3% respectively for the 207 binary alloys. The contants a and b in the parabola equation, and c, d, m and n in the ellipse equation can be related to some appropriate parameters for each host metal respectively. The reasons are discussed. From the theories the soluble elements in these actinide host metals that have not been measured yet can be predicted in the accuracies of the schemes.

Perspectives for the Development of Chemistry of Actinides in Kazakhstan

One of the urgent tasks of the uranium industry in Kazakhstan is the extraction of radionuclide residues from spent uranium wells.We proposed to extract the remains of radionuclides from the drilled wells and to improve the radiation safety of the contaminated area.We conducted a chemical analysis of the content of radionuclides in the ore material.The radionuclides U,Th,Pa,Ra,Ac,Rn were extracted,which can be used in industry and medicine in Kazakhstan.

Key Role of Hybridization between Actinide 5<i>f</i>and Oxygen 2<i>p</i>Orbitals for Electronic Structure of Actinide Dioxides

In order to promote our understanding on electronic structure of actinide dioxides, we construct a tight-binding model composed of actinide 5f and oxygen 2p electrons, which is called f-p model. After the diagonalization of the f-p model, we compare the eigen-energies in the first Brillouin zone with the results of relativistic band-structure calculations. Here we emphasize a key role of f-p hybridization in order to understand the electronic structure of actinide dioxides. In particular, it is found that the position of energy levels of Г7 and Г8 states determined from crystalline electric field (CEF) potentials depends on the f-p hybridization. We investiagte the values of the Slater-Koster integrals for f-p hybridization, (fpσ) and (fpπ), which reproduce simultaneously the local CEF states and the band-structure calculation results. Then, we find that the absolute value of (fpπ) should be small in comparison with (fpσ) = 1 eV. The small value of |(fpπ)| is consistent with the condition to obtain the octupole ordering in the previous analysis of the f-p model.

2-23 Research of A New Triazoly-pyridine Ligand for Lanthanide/Actinide Extraction

If high level radioactive waste (HLW) is directly disposed in stable deep geological formations for long periods of time (some hundred thousand years), any release of which might take place in the future will pose no significant health or environmental risk. Partitioning and transmutation (P&T) is the one of the most important strategies to reduce the long-term radiotoxicity of HLW[1].

Operational Protocol for Detection of Contamination by Actinides U,Pu and Am in Urine Using Calixarene Columns:From Mineralization to ICP-MS Measurement

Individual monitoring of workers exposed to the risk of intake of actinides requires suitable methods for measuring low level of excreted activity. The current protocols used for actinides analysis in bioassay are usually complicated and highly time consuming. In this work, a protocol based on the microwave digestion of urines followed by the separation of actinides using calix[6]arene-based chromatography columns and their measurement by a quadrupole ICP-MS is developed and validated, for the first time, on urine samples containing the three actinides, U, Pu and Am. With this protocol, the total analysis time is about 2 days, including the mineralization of urine and the chromatographic separation of actinides. Detection limits of actinides in urine are determined and compared to those obtained after “dilute and shoot” ICP-MS analysis or after alpha spectrometry measurement.

Recent Progresses in Experimental and Theoretical Studies of Actinide Clusters

Actinide-containing cluster compounds are highly important in radio-and nuclear chemistry.Until three decades ago,little attention had been paid to these heavy-element clusters because of difficulties in their syntheses and characterization as well as handling of these radioactive and chemotoxic elements.In this overview article we have selectively summarized the recent progresses in experimental and theoretical studies on actinide clusters,including actinide(An=Th,Pa,U,Np and Pu)oxide clusters as well as uranyl(UO22+)peroxide clusters and so on.It shows that An(Ⅳ)(An=Th,U,Np and Pu)is able to form highly symmetric AnⅣ6O8 core clusters and further merge into larger clusters up to An38O56 clusters(An=U,Np and Pu)with the same topology.Meanwhile,An with higher oxidation states such as U(Ⅵ)in uranyl is capable to form fullerene-like peroxide cage clusters of U20,U60 with the same topology as C20 and C60.Relativistic quantum chemistry investigations on the geometric structures,electronic structures and chemical bonding patterns have also been briefly summarized herein to provide an understanding on the structural chemistry of these peculiar clusters.The advances in electronic structure studies of actinide clusters help to develop robust theoretical and computational techniques for the future development of actinide cluster chemistry.Further experimental and computational studies of actinide clusters are needed and helpful to accelerate the development of radio-and nuclear chemistry.

Theoretical predictions on α-decay properties of some unknown neutrondeficient actinide nuclei using machine learning

Neutron-deficient actinide nuclei provide a valuable window to probe heavy nuclear systems with large proton-neutron ratios. In recent years, several new neutron-deficient Uranium and Neptunium isotopes have been observed using α-decay spectroscopy [Z. Y. Zhang et al., Phys. Rev. Lett. 122, 192503(2019);L. Ma et al., Phys. Rev.Lett. 125, 032502(2020);Z. Y. Zhang et al., Phys. Rev. Lett. 126, 152502(2021)]. In spite of these achievements,some neutron-deficient key nuclei in this mass region are still unknown in experiments. Machine learning algorithms have been applied successfully in different branches of modern physics. It is interesting to explore their applicability in α-decay studies. In this work, we propose a new model to predict the α-decay energies and half-lives within the framework based on a machine learning algorithm called the Gaussian process. We first calculate the α-decay properties of the new actinide nucleus 214 U. The theoretical results show good agreement with the latest experimental data, which demonstrates the reliability of our model. We further use the model to predict the α-decay properties of some unknown neutron-deficient actinide isotopes and compare the results with traditional models. The results may be useful for future synthesis and identification of these unknown isotopes.

Actinide-embedded gold superatom models： Electronic structure, spectroscopic properties, and applications in surface-enhanced Raman scattering

Actinide elements encaged in a superatomic cluster can exhibit unique properties due to their hyperactive valence electrons. Herein, the electronic and spectroscopic properties of Th@Au14 are predicted and compared with that of the isoelectronic entities [Ac@Au14]- and [Pa@Au14]＋ using density functional theory. The calculation results indicate that these clusters all adopt a closed- shell superatomic 18-electron configuration of the 1S21p61D10 Jellium state. The absorption spectrum of Th@Au14 can be interpreted by the Jelliumatic orbital model. In addition, calculated spectra of pyridine-Th@Au14 complexes in the blue laser band exhibit strong peaks attributable to charge transfer （CT） from the metal to the pyridine molecule. These charge-transfer bands lead to a resonant surface-enhanced Raman scattering （SERS） enhancement of -104. This work suggests a basis for designing and synthesizing SERS substrate materials based on actinide-embedded gold superatom models.

The development of molecular and nano actinide decorporation agents

Internal contamination of actinides has led to significant health hazards to the public and workers in the context of nuclear power plant accidents,uranium ore mining,and reprocessing of the used fuel.An effective sequestering agent that is able to remove accidentally incorporated actinides in vivo with low toxicity is always in urgent need.The molecular decorporation ligands have been the most widely researched agents for the past few decades,while preliminary studies of functionalized nanoparticles have shown their clear advantages in metal binding selectivity,toxicity,and oxidative stress alleviation.Herein,the state-of-the-art of those two types of decorporation agents is presented with special attention being paid on the correlation between the solution and solid-state chemistry of those agents with actinides and the corresponding decorporation efficacies.

Competing Crystallization between Lanthanide and Actinide in Acidic Solution Leading to Their Efficient Separation

Summary of main observation and conclusion We present a new method for generating europium oxalate compounds by decomposing of N-methyl 2-pyrrolidone in HNO3 media.The reaction exhibits high selectivity towards Eu^3+ over UO2^2+,which suggests that these conditions could be applied to a selective crystallization based separation system for trivalent lanthanides and hexavalent actinides.

Neutron nuclear data evaluation of actinide nuclei for CENDL-3.1

New evaluations for several actinide nuclei of the third version of Chinese Evaluated Nuclear Data Library for Neutron Reaction Data （CENDL-3.1） have been completed and released. The evaluation is for all neutron induced reactions with uranium, neptunium, plutonium and americium in the mass range A-232-241, 236 239, 236-246 and 240-244, respectively, and cover the incident neutron energy up to 20 MeV. In the present evaluation, much more effort was devoted to improving the reliability of the evaluated nuclear data for available new measured data, especially scarce or absent experimental data. A general description for the evaluation of several actinides＇ data is presented.

Calculation of cohesive energy of actinide metals

According to empirical electron theory of solids and molecules (EET), an equation for calculating the cohesive energy of actinide metals is given, the cohesive energy of 9 actinide metals with known crystal structure is calculated, which is identical with the experimental values on the whole, and the cohesive energy of 6 actinide metals with unknown crystal structure is forecast.

GENERAL EQUATION OF SINGLE BOND RADⅡ R(1) OF ACTINIDES——NECESSARY PARAMETERS FOR THE EXTENSION OF THE EMPIRICAL ELECTRON THEORY OF SOLIDS AND MOLECULES TO THE 7TH PERIOD IN THE PERIODIC TABLE

Ⅰ. INTRODUCTION The well-known Pauling’s electron theory for metals and alloys established the empirical general equation of the single bond radii R(1) for transition elements to the 4th, 5th and 6th periods in the periodic table. Yu Ruihuang first utilizes the form of Pauling’s R(1) equation but changes the physical meaning and thereby the real physical nature of

A GENERAL EQUATION FOR CALCULATING THE SINGLE BOND RADII R(1)OF ACTINIDES

Ⅰ. INTRODUCTION The valence state changes of actinides are complicated by their electron structures, because the valence electron structures of an element are different in different compounds. For this reason, study on the electron structures of metals and compounds of actinides is of important theoretical significance. The equation for calculating the single bond radii R(1) and the hybrid levels of valence 3 actinides have been established by Chen et al.,

Theoretical study on production cross sections of exotic actinide nuclei in multinucleon transfer reactions

Within the dinuclear system（DNS） model, the multinucleon transfer reactions 129,136Xe ＋248Cm,112Sn＋238U, and 144Xe ＋248Cm are investigated. The production cross sections of primary fragments are calculated with the DNS model. By using a statistical model, we investigate the influence of charged particle evaporation channels on production cross sections of exotic nuclei. It is found that for excited neutron-deficient nuclei the charged particle evaporation competes with neutron emission and plays an important role in the cooling process. The production cross sections of several exotic actinide nuclei are predicted in the reactions 112Sn ＋238U and 136,144Xe ＋248Cm.Considering the beam intensities, the collisions of 136,144Xe projectiles with a 248Cm target for producing neutron-rich nuclei with Z =92-96 are investigated.

Predicting the optical observables for nucleon scattering on even-even actinides

The previously derived Lane consistent dispersive coupled-channel optical model for nucleon scattering on 232Th and 23Su nuclei is extended to describe scattering on even-even actinides with Z=90-98. A soft-rotator- model （SRM） description of the low-lying nuclear structure is used, where the SRM Hamiltonian parameters are adjusted to the observed collective levels of the target nucleus. SRM nuclear wave functions （mixed in K quantum number） have been used to calculate the coupling matrix elements of the generalized optical model. The ＂effective＂ deformations that define inter-band couplings are derived from the SRM Hamiltonian parameters. Conservation of nuclear volume is enforced by introducing a dynamic monopolar term to the deformed potential, leading to additional couplings between rotational bands. The fitted static deformation parameters are in very good agreement with those derived by Wang and collaborators using the Weizs^cker-Skyrme global mass model （WS4）, allowing use of the latter to predict cross sections for nuclei without experimental data. A good description of the scarce ＂optical＇experimental database is achieved. SRM couplings and volume conservation allow a precise calculation of the compound-nucleus formation cross sections, which is significantly different from that calculated with rigid-rotor potentials coupling the ground-state rotational band. The derived parameters can be used to describe both neutron- and proton-induced reactions.

Pairing effects on the fragment mass distribution of Th,U,Pu,and Cm isotopes

In this article,a comprehensive study of the fission process of Th,U,Pu,and Cm isotopes using a Yukawa-folded meanfield plus standard pairing model is presented.The study focused on analyzing the effects of the pairing interaction on the fragment mass distribution and its dependence on nuclear elongation.The significant role of pairing interactions in the fragment mass distributions of^(230)Th,^(234)U,^(240)Pu,and^(246)Cm was demonstrated.Numerical analysis revealed that increasing the pairing interaction strength decreased the asymmetric fragment mass distribution and increased the symmetric distribution.Furthermore,the odd-even mass differences at symmetric and asymmetric fission points were examined,highlighting their sensitivity to changes in the pairing interaction strength.Systematic analysis of the Th,U,Pu,and Cm isotope fragment mass distributions demonstrated the effectiveness of the model in reproducing the experimental data.In addition,the effects of the zero-point energy and half-width parameter on the fragment mass distribution for^(240)Pu were explored.Thus,this study provides valuable insights into the fission process by emphasizing the importance of pairing interactions and their relationship with nuclear elongation.

pH-dependent Synthesis of Octa-nuclear Uranyl-oxalate Network Mediated by U-shaped Linkers

In this work,we report a novel octa-nuclear uranyl(U8)motif[(UO2)8O4(μ3-OH)2(μ2-OH)2]4+embedded in a uranyl-oxalate coordination polymer(compound 1)based on a U-shaped linker with extra-long xylylene chains for stabilizing the resulting high-nuclear motif through additional cross-linking connectivity.A comparison with dimeric and monomeric uranyl compounds obtained at different pH value from the same hydrothermal system reveals that,solution pH plays a vital role in formation of this octa-nuclear uranyl motif by promoting hydrolysis of uranyl source.Since high similarity of eight uranium centers in this nearly planar U8 motif here,overlapping and broadening of signals in fluorescence,infra-red(IR)and Raman spectra can be found.

Comparison of Radionuclide’s Inventories and Activities With Slightly Enriched Uranium and Plutonium Fuel in CANDU Reactors

In these studies the isotopic inventories and corresponding activities of important nuclides for different fuel cycles of a CANDU reactor have been compared. The calculations have been performed using the computer code WIMSD4. The isotopic inventories and activities have been calculated versus the fuel burn-up for the natural UO2 fuel, 1.2% enriched UO2 fuel and for the 0.45% PuO2-UO2 fuel. It is found that 1.2% enriched uranium fuel has the lowest activity as compared to other two fuel cycles and vice versa for the 0.45% PuO2-UO2 fuel.