Samarium Isotopes Research Articles

Pygmy Dipole Response in Samarium isotopes

The influence of nuclear shape deformation on the Pygmy Dipole Response (PDR) was investigated using (α,α′γ) scattering on 144Sm and 154Sm. Experiments were conducted at iThemba LABS, coupling for the first time the K600 magnetic spectrometer with the BaGeL (Ball of Germanium and LaBr detectors) array. Preliminary results showcasing the efficacy of the facility and set-up for performing these 0° scattering experiments to investigate the PDR region are presented.

Comparison of methods for calculating the neutronic characteristics of a VVER-1200 fuel assembly

This article presents the results of neutronic calculations of a VVER-1200 fuel assembly carried out using the multi-purpose three-dimensional continuous-energy Monte Carlo particle transport code Serpent 2. The study compares neutronic characteristics during the fuel burnup process (1) with and (2) without fuel cooling. In the first option, the FA fuel campaign was simulated with 30-day cooling periods between reactor campaigns. The second option assumed simulating the FA fuel campaign without fuel cooling. In the course of the study, the authors determined the infinite neutron multiplication factors as well as the fuel burnup dependence of the concentrations of xenon, samarium and gadolinium nuclides. In addition, it should be noted that no differences were found in the change in the concentration of gadolinium isotopes, the discrepancy in the values of the multiplication factor, and the accumulation of samarium isotopes during the campaign.

Laser-induced isotope selective photoionization of atomic samarium

Resonance ionization spectroscopy of samarium has been performed in an atomic beam in conjunction with a time-of-flight mass spectrometer. Isotope selective photoionization studies have been carried out on one of the even isotopes of samarium (152Sm). High degree of isotopic selectivity (> 95%) has been achieved experimentally for 152Sm using multi-mode dye lasers. Isotopic abundance of 152Sm in mass selective photoionization has been studied as a function of excitation laser energy density. By employing isotope selective photoionization spectroscopy, the isotope shifts for the first- and second-step transitions have also been determined.

Выделение и радиохимическая очистка изотопов самария с использованием ионообменных смол АВ 17×8 и КУ-2

The relevance of the research is caused by the need to develop a methodological base for determining 151Sm content in the soil cover of radioactively contaminated territories of Kazakhstan. The developed method for the determining of 151Sm will make it possible to assess the levels of soil contamination with this radionuclide, to determine the character of its spatial distribution, to allow estimating the internal exposure doses for the personnel and the population. The aim of the research is to carry out the isolation and radiochemical purification of samarium isotopes from acid solutions via using ion-exchange resins AV 17×8 and KU-2. Objects: salt solutions based on nitric and hydrochloric acid containing the stable isotopes of some natural, artificial β-emitters and isotopes of U and Th. The concentrations of nitric and hydrochloric acids were equal to the concentrations of the same acids used in the routine analysis of Pu and Am. Concentrations of chemical elements were determined using the Agilent 7700x quadrupole mass spectrometer and the iCAP 6300 Duo atomic emission spectrometer. The results of the experiments on the isolation and radiochemical purification of samarium isotopes from acidic solutions using anion-exchange resin AV 17×8 and cation-exchange resin KU-2 have been presented. It has been shown that the Sm-fraction can be purified from alkaline elements, Tl and U isotopes using the KU-2 cation-exchange resin. In turn, the isotopes U, Fe and Co can be removed using an anion exchange resin in 9M HCl media.

State densities of heavy nuclei in the static-path plus random-phase approximation

Nuclear state densities are important inputs to statistical models of compound-nucleus reactions. State densities are often calculated with self-consistent mean-field approximations that do not include important correlations and have to be augmented with empirical collective enhancement factors. Here, we benchmark the static-path plus random-phase approximation (SPA+RPA) to the state density in a chain of samarium isotopes $^{148-155}$Sm against exact results (up to statistical errors) obtained with the shell model Monte Carlo (SMMC) method. The SPA+RPA method incorporates all static fluctuations beyond the mean field together with small-amplitude quantal fluctuations around each static fluctuation. Using a pairing plus quadrupole interaction, we show that the SPA+RPA state densities agree well with the exact SMMC densities for both the even- and odd-mass isotopes. For the even-mass isotopes, we also compare our results with mean-field state densities calculated with the finite-temperature Hartree-Fock-Bogoliubov (HFB) approximation. We find that the SPA+RPA repairs the deficiencies of the mean-field approximation associated with broken rotational symmetry in deformed nuclei and the violation of particle-number conservation in the pairing condensate. In particular, in deformed nuclei the SPA+RPA reproduces the rotational enhancement of the state density relative to the mean-field state density.

Markov Chain Monte Carlo Predictions of Neutron-rich Lanthanide Properties as a Probe of r-process Dynamics

Abstract Lanthanide element signatures are key to understanding many astrophysical observables, from merger kilonova light curves to stellar and solar abundances. To learn about the lanthanide element synthesis that enriched our solar system, we apply the statistical method of Markov Chain Monte Carlo to examine the nuclear masses capable of forming the r-process rare-earth abundance peak. We describe the physical constraints we implement with this statistical approach and demonstrate the use of the parallel chains method to explore the multidimensional parameter space. We apply our procedure to three moderately neutron-rich astrophysical outflows with distinct types of r-process dynamics. We show that the mass solutions found are dependent on outflow conditions and are related to the r-process path. We describe in detail the mechanism behind peak formation in each case. We then compare our mass predictions for neutron-rich neodymium and samarium isotopes to the latest experimental data from the CPT at CARIBU. We find our mass predictions given outflows that undergo an extended (n,γ)⇄(γ,n) equilibrium to be those most compatible with both observational solar abundances and neutron-rich mass measurements.

Investigation of Alignment Effects of Neutron and Proton Pairs in High Spin States of Band Crossing for <sup>159,160</sup>Sm Isotopes Using Projected Shell Model (PSM)

Energy spectrum of nucleus is one the important information for better recognition of nuclear force and interaction of nucleon inside of the nucleus. Energy levels of nucleus are measured by detecting gamma- ray energy spectrum when a target nucleus bombarded with a special projectile to excite it in to levels higher than ground state. On the other hand, there are several models to calculate nuclear energy levels. Solution of the Schrödinger equation by considering a suitable potential is direct method to obtain energy levels of a quantum mechanical system like nucleus. Projected shell model is a model of this type that is developed by solving the Schrödinger equation for a set of potentials along with role of spin. Band structure and yrast bands for even-even and odd-even isotopes of Samarium (^159,160Sm) are calculated using a Fortran code founded based on the projected shell model (PSM). Energy levels of negative and positive parity bands of ¹⁵⁹Sm and ¹⁶⁰Sm isotopes of Samarium nucleus are obtained separately for each spin. Kinetic and dynamic moments of inertias are also calculated for these isotopes. The acquired results are compared with the experimental data. The electromagnetic reduced transition probabilities, B(M1)/B(E2) the behavior of dynamic moment of inertia J², rotational kinetic energy and moment of inertia J¹ as a function of spin have also been investigated and proper comparison is made between the calculated results and the experimental data. The alignment phenomena of neutron-proton pairs in view of the rotational movement in high spin states has also been studied with reference to band crossing.

Microscopic study of band structures of neutron-rich 153,155,157Sm isotopes

A systematic study of band structures of some odd mass Samarium isotopes with neutron numbers 91 ≤ N ≤ 95 is carried out by employing projected shell model. The theoretical results have been obtained for band head energies, energy spectra, transition energies and moment of inertia. The calculations on comparison with the experimental data show a reasonably good agreement. The band spectra and transition energies for higher spin states are also predicted in these isotopes. The calculations successfully provide good understanding of the change in structure of the yrast bands and excited bands in terms of single and multi-quasiparticle configurations. The future experimental work will test the predictions made in this paper.

Effects of Gamma Strength Functions on Cross–Section Calculations of Some Samarium Isotopes (γ,n) and (γ,2n) Reactions

Teorik modeller ile yapılan çalışmalar, deneysel verilerin mevcut olmadığı veya deneysel çalışmaların gerçekleştirilemediği durumlarda araştırmacıların farklı veriler hakkında öngörü sahibi olmaları sağlar. Bu verilerden biri de, bir reaksiyonun meydana gelme olasılığı olarak tanımlanabilen tesir kesiti değeridir. Ölçülebilen veya hesaplanabilen bir değer olan tesir kesitinin hesaplanmasında, çeşitli modellerin farklı etkilerinin araştırılması bu değerin doğru hesaplanabilmesi açısından son derece önemlidir. Bu bağlamda, bu çalışmada 148,150,152,154Sm izotoplarının (γ,n) ve (γ,2n) reaksiyonlarında tesir kesiti hesaplamalarında farklı gama kuvvet fonksiyonlarının etkilerinin araştırılması amaçlanmıştır. Hesaplamalarda TALYS 1.9 kodu kullanılmış ve elde edilen hesaplama sonuçları literatürde mevcut olan deneysel veriler ile karşılaştırılmıştır. Ayrıca, elde edilen sonuçlar ve deneysel veriler kullanılarak göreli bağıl varyans ve ortalama ağırlıklı sapma analizleri de yapılmıştır. Bu sayede her bir reaksiyon için deneysel veriler ile en uyumlu sonuçların elde edilmesini sağlayan gama kuvvet fonksiyonu tespit edilmiştir.

Samarium isotope compositions of uranium ore concentrates: A novel nuclear forensic signature

Uranium ore is mined and milled to produce uranium ore concentrate (UOC), a regulated product of the nuclear fuel cycle. Diversion of UOC from the fuel cycle into possible weapons production is a key concern in global nonproliferation efforts. As such, the ability to trace the origin of seized nuclear materials is imperative to law enforcement efforts. Although isotopic signatures of UOCs have proven fruitful to pinpoint sample provenance, new isotopic signatures are needed because most existing isotopic signatures are not indicative of the original ore body from which the U is derived. In this work, we developed a new method to separate samarium (Sm) from a U-rich sample matrix and report the first Sm isotope compositions of 32 UOCs derived from a variety of worldwide uranium mines. Relative to terrestrial standards, approximately half the UOCs have resolved and anticorrelated 149Sm-150Sm isotope compositions, consistent with the capture of thermal neutrons by 149Sm in the ore body. The UOCs with anomalous Sm isotope compositions tend to derive from older (~>1.5Ga) and higher-grade ore bodies, although other factors, such as the presence of neutron moderators like water, also play a role. Nonetheless, the Sm isotope compositions of UOCs directly reflects the neutron fluence over the history of the original ore body and can be used to discern different geologic conditions associated with that ore body. As such, this work demonstrates the potential use of Sm isotopes as a novel nuclear forensics signature for origin assessment of UOCs.

Использование гидроксидов и фторидов металлов для концентрирования и выделения изотопов самария из кислотных выщелатов почвы

Использование гидроксидов и фторидов металлов для концентрирования и выделения изотопов самария из кислотных выщелатов почвы

Enhancement of photoionization by applying polarization-based common level excitation scheme for the selective photoionization of odd isotopes of samarium

Due to the importance of 149Sm isotope in the nuclear industry, isotope-selective photoionization of the odd isotopes of samarium has been studied using multi-color photoionization technique. The present work has been carried out in an atomic beam coupled to a linear time-of-flight mass spectrometer using multimode dye lasers. A new photoionization scheme: 292.58 cm−1 →17,769.71 cm−1→34,929.9 cm−1→ continuum with the J-value sequence 1-1-0-continuum has been identified for the enrichment of only odd isotopes using linearly polarized lasers in the same direction. This photoionization scheme in combination with the first-step transition: 0 cm−1 →17,769.71 cm−1 (J = 0→J = 1) has been utilized to realize a common level excitation scheme which has significantly increased the photoionization yield of the odd isotopes and suppressed the ionization of the even isotopes of samarium using suitable choice of laser polarization. To enhance the photoionization yield further, a search for the third-step transition terminating into an autoionization level has been carried out. A strong autoionization resonance at the third-step laser wavelength 644.14 nm, corresponding to the transition 34,929.9 cm−1→ 50,450.3 cm−1 has been identified. The J-value of the newly discovered autoionization level at 50,450.3 (±0.5) cm−1 has been uniquely assigned as J = 1. Finally, the photoexcitation/photoionization cross sections of all the transitions involved in the common level excitation scheme including that of the third-step transition terminating into the autoionization level have been measured by saturation method.

ЭКСПЕРИМЕНТАЛЬНАЯ ОЦЕНКА СТЕПЕНИ ОЧИСТКИ ИЗОТОПОВ САМАРИЯ ОТ ЩЕЛОЧНЫХ И ЩЕЛОЧНОЗЕМЕЛЬНЫХ ЭЛЕМЕНТОВ ПРИ ОСАЖДЕНИИ ГИДРООКИСЕЙ МНОГОВАЛЕНТНЫХ МЕТАЛЛОВ

Актуальность исследования обусловлена необходимостью создания методической базы по определению содержания 151Sm на территории бывшего Семипалатинского испытательного полигона. В настоящее время информация об уровнях содержания данного радионуклида в объектах окружающей среды отсутствует, что не позволяет учитывать его влияние на дозовую нагрузку населения ведущего хозяйственную деятельность на территории полигона и потребляющего продукты данной сельскохозяйственной деятельности. Цель: оценить степень очистки изотопов самария от щелочных и щелочноземельных элементов при осаждении гидроксидов многовалентных металлов, в рамках разработки методики радиохимического определения 151Sm в почвенном покрове на территории бывшего Семипалатинского испытательного полигона. Объект: раствор на основе азотной кислоты концентрацией 3 моль/л, моделирующий состав раствора, получаемого после кислотной обработки почвы. Для приготовления раствора использовались основные макро- и микроэлементы, входящие в состав почвы, а также такие элементы, как: висмут, свинец, таллий, радиоактивные изотопы которых входят в радиоактивные семейства урана и тория. Методы: измерение рН растворов на приборе МАРК-901; измерение концентрации химических элементов с использованием квадрупольного масс-спектрометра Agilent 7700x и атомно-эмиссионного спектрометра с индуктивно-связанной плазмой iCAP 6300 Duo. Результаты. Представлены результаты исследований по оценке степени очистки изотопов самария от щелочных и щелочноземельных элементов при осаждении гидроксидов. Предложено наиболее оптимальное значение рН, при котором захват примесей незначителен, а выход изотопов самария максимален. Очистка от щелочных элементов составила в среднем 90 %, от щелочноземельных 80 %.

Precision Mass Measurements of Neutron-Rich Neodymium and Samarium Isotopes and Their Role in Understanding Rare-Earth Peak Formation.

The Canadian Penning Trap mass spectrometer at the Californium Rare Isotope Breeder Upgrade (CARIBU) facility was used to measure the masses of eight neutron-rich isotopes of Nd and Sm. These measurements are the first to push into the region of nuclear masses relevant to the formation of the rare-earth abundance peak at A∼165 by the rapid neutron-capture process. We compare our results with theoretical predictions obtained from "reverse engineering" the mass surface that best reproduces the observed solar abundances in this region through a Markov chain MonteCarlo technique. Our measured masses are consistent with the reverse-engineering predictions for a neutron star merger wind scenario.

Analyses of used BWR fuel assay data with the integrated burnup code system SWAT4.0

ABSTRACT Criticality safety of the fuel debris from the Fukushima Daiichi Nuclear Power Plant is one of the most important issues, and the adoption of burnup credit is desired for criticality safety evaluation. To adopt the burnup credit, validation of the burnup calculation codes is required. Assay data of the used nuclear fuel irradiated by the Fukushima Daini Nuclear Power Plant Unit 2 are evaluated to validate the SWAT4.0 code for solving the BWR fuel burnup problem. The calculation results revealed that the number densities of many heavy nuclides and fission products show good agreement with the experimental data, except for those of 237Np, 238Pu, and samarium isotopes. These differences were considered to originate from inappropriate assumption of void fraction. Our results implied overestimation of the (n, γ) cross-section of 237Np in JENDL-4.0. The Calculation/Experiment – 1 (C/E–1) value did not depend on the type of fuel rod (UO2 or UO2–Gd2O3), which was similar to the case of PWR fuel. The differences in the number densities of 235U, 239Pu, 240Pu, 241Pu, 149Sm, and 151Sm have a large impact on k eff. However, the reactivity uncertainty related to the burnup analysis was less than 3%. These results indicate that SWAT4.0 appropriately analyzes the isotopic composition of BWR fuel, and it has sufficient accuracy to be adopted in the burnup credit evaluation of fuel debris.

Cross sections for d-3H neutron interactions with samarium isotopes

Abstract: The cross sections for (n,x) reactions on samarium isotopes were measured at (d-T) neutron energies of 13.5 and 14.8 MeV with the activation technique. Samples were activated along with Nb and Al monitor foils to determine the incident neutron flux. Theoretical calculations of excitation functions were performed using the nuclear model codes TALYS-1.6 and EMPIRE-3.2 Malta with default parameters, at neutron energies varying from the reaction threshold to 20 MeV. The results were discussed and compared with experimental data found in the literature. At neutron energies 13.5 and 14.8 MeV, the cross sections of the 149Sm(n,p)149Pm reaction are reported for the first time. The cross sections of the 150Sm(n,p)150Pm, 144Sm(n,p)144Pm, 152Sm(n,α)149Nd and 144Sm(n,α)141Nd reactions at different neutron energies reported in the present work can be added as new data in the nuclear databases.

Nuclear deformation study using the framework of self-consistence Hartree-Fock-Bogoliubov

In the present work the nuclear deformation of Sodium, Silicon, Chromium, and Samarium isotopes has been investigated within the framework of Skyrme-Hartree-Fock-Bogolyubov method. In particular, we investigate the behaviour the potential energy curves as a function of the quadrupole deformation parameter for these isotopes using SLy4 parameterization which give good agreement for the nuclear root mean square radii and binding energies. The variation effect of Skyrme parameterizations; SLy4, SLy7, SkM* and Skxs25 on the calculated values of the quadrupole deformation of the selected isotopes have been also disclosed in appropriate figures.

Coupling effects on the fusion ofLi6+Sm154at energies slightly above the Coulomb barrier

Measurements of complete and incomplete fusion cross sections for $^{6}\mathrm{Li}+^{154}\mathrm{Sm}$ have been performed at energies above the Coulomb barrier by the online $\ensuremath{\gamma}$-ray method, to investigate the effect of breakup and inelastic couplings on the complete fusion (CF) of this weakly bound system. We show that inelastic excitation couplings have non-negligible effects, when compared with the breakup effect, for deformed nuclei at energies very close to the Coulomb barrier. The average CF suppression corresponding to dynamic breakup effects was found to be around 35%. The total fusion cross section is not affected by the breakup coupling. A comparison between the $^{6}\mathrm{Li}$-induced CF suppression for three different samarium isotopes shows that the breakup effect is larger for the more spherical isotope.

Deformation effects in Giant Monopole Resonance

The isoscalar giant monopole resonance (GMR) in Samarium isotopes (from spherical 144Sm to deformed 148-154Sm) is investigated within the Skyrme random-phase- approximation (RPA) for a variety of Skyrme forces. The exact RPA and its separable version (SRPA) are used for spherical and deformed nuclei, respectively. Consistently with earlier investigations, the quadrupole deformation is shown to yield two effects: the GMR broadens and attains a two-peak structure due to the coupling with the quadrupole giant resonance.

Photoneutron cross sections for samarium isotopes: Toward a unified understanding of(γ,n)and(n,γ)reactions in the rare earth region

Photoneutron cross sections were measured for the seven stable samarium isotopes ${}^{144,147,148,149,150,152,154}\mathrm{Sm}$ near the neutron threshold with quasi-monochromatic laser-Compton scattering $\ensuremath{\gamma}\phantom{\rule{0.28em}{0ex}}\mathrm{rays}$. Our photoneutron cross sections are found to be low by 20%--37% relative to existing data. The photoneutron data are analyzed with the talys reaction code by considering the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially symmetric deformed Gogny HFB plus QRPA model of the $E1$ $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{ray}$ strength. Using the $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{ray}$ strength function constrained by the present photoneutron data, we made a thorough analysis of the reverse $(n,\ensuremath{\gamma})$ cross sections including the radioactive nucleus $^{151}\mathrm{Sm}$ with a half-life of 90 yr. The radiative neutron capture cross section for $^{153}\mathrm{Sm}$ with the half-life of 1.928 d is deduced with the $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{ray}$ strength function method.