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.

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.

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.,

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.

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.

A Suggestion Complementing the Magic Numbers Interpretation of the Nuclear Fission Phenomena

Ideas, solely related on the nuclear shell model, fail to give an interpretation of the experimental central role of 54Xe in the asymmetric fission of actinides. The same is true for the β-delayed fission of 180Tl to 80Kr and 100Ru. The representation of the natural isotopes, in the Z-Neutron Excess plane, suggests the importance of the of the Neutron Excess evolution mode in the fragments of the asymmetric actinide fission and in the fragments of the β-delayed fission of 180Tl. The evolution mode of the Neutron Excess, hinged at Kr and Xe, is directed by the 50 and 82 neutron magic numbers. The present isotope representation offers a frame for the interpretation of the post fission evaporation of neutrons, higher for the AL compared to the AH fragments, a tenet in nuclear fission. Further enlightened is the functional meaning of the 50 proton magic number, marking the start of the yield rise of the AH fragments in actinide fission.

Americium Transmutation in the SVBR-100 Reactor

One of the postponed problems of nuclear power (NP) is the problem of the management of long-lived radioactive waste (RAW), and, first of all, with minor actinides (MA), of which americium-241 is the most difficult. The aim of this work is to study the efficiency of americium transmutation in a fast reactor with a heavy liquid metal coolant lead-bismuth eutectic alloy. The article presents the results of calculations of the transmutation of americium in the SVBR-100 reactor using standard uranium oxide fuel with the addition of americium-241. The obtained values of the rate of transmutation of americium are compared with similar values for the SVBR-100 reactors on MOX-fuel and in the BN-800 reactor.

Education and Training in Radiochemistry——The NAMP Initiative

A number of reports have indicated that a sizable percentage of the nation＇s experts in radiochemistry are nearing retirement age. This reality has been a concern since the 1970s, when declining numbers of radiochemists worldwide was first observed. Therefore, the NAMP （National Analytical Management Program） has organized a subcommittee focused on training and education in radiochemistry. To bolster interest and increase awareness in radiochemistry, NAMP is offering webinars developed by experts on different topics relevant to radiochemistry. This paper presents our accomplishments in developing these webinars and highlights our efforts in outreaching the national and international radiochemistry community.

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.

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.

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.

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].

Oxygen Potential Analysis to Evaluate Irradiation Behavior in MOX and MA-Bearing MOX Fuels

Oxygen potentials of oxide nuclear fuels are important thermodynamic data in development of nuclear fuel technologies. Minor actinide bearing MOX （mixed oxide） fuels have been developed as sodium cooled fast reactor fuels. Content of Am which is one of the minor actinide elements causes oxygen potentialto increase. The effects of the oxygen potential increase on the irradiation behavior were evaluated. Profiles of temperature and O/M （oxygen-to-metal） ratio in the pellets were evaluated to better understand the irradiation behavior. From these data, local oxygen potential in the radial direction of the pellets was calculated, and was compared with free energy of compounds composed of fission products. Based on this comparison, it was concluded that Cs2MoO4 was likely formed at pellet periphery of （U07Pu03）O1.98 and （U0.66Pu03Amoo16Npo.016）Ol.976 The extent of cladding tube inner surface oxidation was predicted by using the calculated oxygen potential. No significant difference between irradiation behaviors of （Uo.7Puo3）O2_x and （U0.66PUo 3Amo.016Npo.016）O2.x pellets was confirmed.

Synthetic Control of Thorium Metal-Organic Frameworks for Sequencing and Sensing of Radioiodine Species

Exploring the physiochemical properties and expanding the applications of actinide-containing materials is paramount to address the escalating challenge of radioactive waste accumulation.However,unlocking the full potential of these materials is largely crippled by the radiotoxicity of the actinides.We report here two porous and luminescent thorium-based metal-organic frameworks(Th-BITD-1 and Th-BITD-2)that serve as a bifunctional platform for sequencing and sensing of radioiodine,a much more radioactive fission product discharged during the nuclear fuel reprocessing.In particular,Th-BITD-1 displays better iodine uptake performance than Th-BITD-2 via the solution-based process and vapor diffusion with the maximum adsorption capacities of 831 and 1099 mg/g,respectively.Fur thermore,Th-BITD-1 can function as a highly sensitive luminescence sensor for iodate with a quenching constant(Ksv)of 6.6(5)×10^(3) M^(-1)and a detection limit of 2.02μM,respectively,outperforming 2.96(6)×10^(3)M^(-1)and 10.5μM of Th-BITD-2.Moreover,a positive correlation between the sensing efficacy and the iodate adsorption capacity has been revealed.This work highlights the opportunity in designing novel actinide-based MOFs for their potential applications in radiological fields,e.g.,radionuclide separation and detection.

Designed assembly of heterometallic cluster organic frameworks based on Th_6 cluster

Four novel compounds based on hexanuclear thorium cluster were synthesized and characterized.Compound 1[Th_(6)(HPy C)_(8)(HCOO)_(4)]is formed by replacing formate ligands of preassembled thorium cluster[Th_(6)O_(4)(OH)_(4)(H_(2)O)_(6)(HCOO)_(12)]with eight H_(2)Py C(4-pyrazolecarboxylic acid)under solvothermal conditions.Each of the HPy C^(-)ligands is coordinated with one Cu^(2+)to form the(4,8)-connected scu-net structure of compound 2[(Cu Cl_(2))_(2)Th_(6)(HPy C)_8(HCOO)_(4)].In compound 3[(Cu Cl_(2))_(2)Th_(6)(HPy C)_(10)(HCOO)_(4)],ten of the formate ligands of preassembled Th_(6)cluster are replaced by HPy C^(-)ligands.Compared with compound 2,the two extra HPy C^(-)ligands in the equatorial plane of the Th_(6)cluster in compound 3 are not further connected to copper ions.Therefore,the topology structure of compound 3 is same with that of compound 2.Compound 4[(Cu_(3)Cl_(2))(Cu Cl_(2))Th_(6)(Py C)_(3)(HPy C)_(4)(HCOO)_(5)]contains three kinds of metal nodes,Th_(6)cluster,Cu_(3)cluster and mononuclear Cu^(2+),and exhibits a novel(5,7)-connected net structure,which was first discovered in actinide MOFs.Furthermore,considering the satisfactory stability of compound 4 and its unsaturated metal nodes and Lewis acid sites,the catalysis of cycloaddition of CO_(2)was further studied.We found that this thorium-copper heterometallic cluster organic framework can be used as a potential actinide functional material for catalyzing the efficient CO_(2)conversion to value-added products.

Prompt neutron emission in ^(250)No spontaneous fission associated with ground and isomeric state decays

The complete-fusion reaction^(204)Pb(^(48)Ca,2n)^(250)No was used to study two activities of^(250)No with distinct half-lives.A total of 1357 events were observed in the SFiNx neutron detection system.The average number of neutrons emitted per spontaneous fission of^(250)No was determined to be(4.1±0.1).The unusually symmetrical shape of the prompt neutron multiplicity distribution was restored and presented for the first time.Statistical tests were performed to compare the prompt neutron multiplicity distributions associated with the ground state and K-isomer state decays.

An advanced partitioning process for key elements separation from high level liquid waste

To separate MA （Am, Cm） and some fission product elements （FPs） such as Tc, Pd, Cs and Sr from high level liquid waste （HLLW） systematically, we have been studying an advanced aqueous partitioning process, which uses selective adsorption as the separation method. For this process, we prepared several novel adsorbents which were immobilized in a porous sili- c^polymer composite support （SiO2-P）. Adsorption and separation behavior of various elements was studied experimentally in detail. Small scale separation tests using simulated HLLW solutions were carried out. Pd（II） was strongly adsorbed by the AR-01 anion exchanger and effectively eluted off by using thiourea. Successful separation of Pd（ll） from simulated HLLW was achieved. Te（VII） also exhibited strong adsorption on AR-01 and could be eluted off by using U（IV） as a reductive eluent. Am（Ⅲ） presented significantly high adsorbability and selectivity onto R-BTP/SiOz-P adsorbents over various FPs including Ln（Ⅲ）. The R-BTP adsorbents were fairly stable in 3 M HNO3, but instable against 7-irradiation-3M HNO3. An advanced par- titioning process consisting of three separation columns for the target elements separation from HLLW was proposed and the obtained experiment results indicated that the proposed process is essentially feasible.