Niobium Isotopes Research Articles

Intertwined quantum phase transitions in the zirconium and niobium isotopes

Nuclei in the A ≈ 100 region exhibit intricate shape-evolution and configuration crossing signatures. Exploring both even–even and their adjacent odd-mass nuclei gives further insight on the emergence of deformation and shape-phase transitions. We employ the algebraic frameworks of the interacting boson model with configuration mixing and the new interacting boson-fermion model with configuration mixing in order to investigate the even–even zirconium with neutron number 52–70 (40Zr) and odd-mass niobium (41Nb) isotopes with 52–62. We compare between the evolution in energy levels, configuration and symmetry content of the wave functions, two neutron separation energies and E2 transition rates, alongside comparison with the experimental data. The comparisons between the two chains of isotopes denote the occurrence of two types of QPTs, a crossing of normal and intruder configurations (named Type II QPT), and a shape-evolution of the intruder configuration (named Type I QPT). The latter QPT begins from spherical shape to axially deformed rotor in the Zr isotopes and from weak to strong coupling scenario in the Nb isotopes. This occurrence, named intertwined quantum phase transitions (IQPTs), in the even–even Zr chain is thus demonstrated to persists when coupling a proton to the boson core for the odd-mass Nb chain, even as deformation increases.

Ниобий в проблеме обеспечения долговременной радиационной безопасности

The article provides a general overview discussing niobium and partially zirconium isotopes and their behavior in experimental and natural environments. In terms of weight, zirconium and niobium isotopes account for a quite tangible fraction of radioactive waste streams generated by nuclear industry. As it comes to natural environments, the behavior of substances containing these isotopes has been poorly studied even over the initial period of their one-time intake. Moreover, their chronic long-term intake over hundreds and thousands of years hasn’t been basically studied at all, which raises certain difficulties when demonstrating the long-term safety of radioactive waste disposal. This overview also evaluates the experimental studies focused on niobium behavior in natural environments, as well as some individual hypotheses about its potential behavior. The paper evidences that new experimental studies should be launched to support the forecasts regarding niobium isotope impacts on various types of biota, including human.

Configuration mixing and intertwined quantum phase transitions in odd-mass niobium isotopes

Configuration mixing and intertwined quantum phase transitions in odd-mass niobium isotopes

Fluorescence correction for activity measurement of 93mNb in niobium dosimeters: Calculation and experimental validation

Niobium is a dosimeter used to characterize fast-neutron reaction rates to monitor nuclear reactor vessels. Its characterization is based on the activity of 93mNb resulting from the 93Nb(n,n’) activation reaction. The decay of 93mNb results mainly in the emission of niobium K X-rays which are used to determine the activity of 93mNb. Direct measurement using X-ray spectrometry does not require any sample preparation, but fluorescence effects, due to impurities which are activated during irradiation, must be taken into account. Indeed, some of these radioactive impurities, in particular 182Ta, and other niobium isotopes remain present during the measurements and disturb the X-ray spectra. The fluorescence effect induces additional niobium X-ray emission to that due to the 93mNb decay alone, which leads to an overestimation of the dosimeter activity, especially if the results are expected shortly after the end of the irradiation. It is therefore necessary to assess the contribution of fluorescence effects to provide accurate values of 93mNb activity. Fluorescence correction factors were established by Monte Carlo simulation. The calculated fluorescence correction factors were validated by an experimental approach, using activated niobium dosimeters with different tantalum concentrations.

Total absorption γ -ray spectroscopy of niobium isomers

The $\beta$ intensity distributions of the decays of $^{100\text{gs},100\text{m}}$Nb and $^{102\text{gs},102\text{m}}$Nb have been determined using the Total Absorption $\gamma$-Ray Spectroscopy technique. The JYFLTRAP double Penning trap system was employed to disentangle the isomeric states involved, lying very close in energy, in a campaign of challenging measurements performed with the Decay Total Absorption $\gamma$-ray Spectrometer at the Ion Guide Isotope Separator On-Line facility in Jyv\"askyl\"a. The low-spin isomeric state of each niobium case was populated through the decay of the zirconium parent, that was treated as a contaminant. We have applied a method to extract this contamination, and additionally we have obtained $\beta$ intensity distributions for these zirconium decays. The $\beta$-strength distributions evaluated with these results were compared with calculations in quasiparticle random-phase approximation, suggesting a prolate configuration for the ground states of $^{100,102}$Zr. The footprint of the Pandemonium effect was found when comparing our results for the analyses of the niobium isotopes with previous decay data. The $\beta$-intensities of the decay of $^{102\text{m}}$Nb were obtained for the first time. A careful evaluation of the uncertainties was carried out, and the consistency of our results was validated taking advantage of the segmentation of our spectrometer. The final results were used as input in reactor summation calculations. A large impact on antineutrino spectrum calculations was already reported and here we detail the significant impact on decay heat calculations.

Large Impact of the Decay of Niobium Isomers on the Reactor ν[over ¯]_{e} Summation Calculations.

Even mass neutron-rich niobium isotopes are among the principal contributors to the reactor antineutrino energy spectrum. They are also among the most challenging to measure due to the refractory nature of niobium, and because they exhibit isomeric states lying very close in energy. The β-intensity distributions of ^{100gs,100m}Nb and ^{102gs,102m}Nb β decays have been determined using the total absorption γ-ray spectroscopy technique. The measurements were performed at the upgraded Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. Here, the double Penning trap system JYFLTRAP was employed to disentangle the β decay of the isomeric states. The new data obtained in this challenging measurement have a large impact in antineutrino summation calculations. For the first time the discrepancy between the summation model and the reactor antineutrino measurements in the region of the shape distortion has been reduced.

Conjugation, labelling and in vitro/in vivo assessment of an anti-VEGF monoclonal antibody labelled with niobium isotopes

Niobium-90 (90Nb) is a positron emitting radionuclide that exhibits attractive characteristics for use in the design and synthesis of radioimmunoconjugates. In the current study we have investigated 90Nb as a possible future isotope for immuno-PET. Prior to 90Nb in vivo studies, this paper describes in vitro and ex vivo studies using a Niobium-95 (95Nb)-monoclonal antibody analogue. 95Nb has a half-life of 35 days and is convenient for long-term studies. 95Nb-labelled bevacizumab was evaluated for early antiangiogenic tumor response assessment and the results were compared with other well established PET nuclides for immuno-PET. 95Nb was quantitatively recovered (> 95%) from irradiated natural Zr in a multistep separation. Bevacizumab was modified with the Df-Bz-NCS (Df) chelate and labelled with previously separated 95Nb. Stability of 95Nb-Df-bevacizumab was evaluated in saline and in human plasma over 7 days presenting > 96% and > 94% of intact product, respectively. Biodistribution ex vivo studies were performed on M165 tumor-bearing mice. 95Nb was obtained in high purity (99.999%) and high radioactivity concentration (1.7 MBq/µL) in a total volume of 200 µL oxalic acid (0.1 M), ready for labelling. Df-bevacizumab labelling was efficient (> 95%) and in vitro stability of 95Nb-Df-bevacizumab was high. Ex vivo studies displayed good tumor-to-background ratios, optimum after 2 days p.i., after iv injection of 20 µg of antibody per mouse. 95Nb was successfully produced and purified from the irradiated target. Labeling of bevacizumab pre-modified with desferrioxamine was achieved in high yields. After in vitro stability of 95Nb-Df-bevacizumab was demonstrated, ex vivo biodistribution studies showed specific tumor uptake in M165 tumor-bearing mice. Consequently, in vivo studies with 90Nb-Df-bevacizumab and small animal PET are in preparation, and we expect that 90Nb-Df-conjugated antibodies will show potential for immuno-PET.

Excitation functions of proton-induced reactions on natFe and natZr targets for the production of cobalt and niobium isotopes

Excitation functions of proton-induced reactions for the natural iron and zirconium targets were measured from their respective threshold energies to 22 and 20 MeV. The conventional stacked foil technique was used in combination with the off-line $\gamma$ -ray spectroscopy at the BARC-TIFR Pelletron facility, Mumbai. The computer code SRIM 2013 was used to calculate the energy degradation along the stack and the proton beam intensity was measured via the natCu(p,x)62Zn monitor reaction. The measured excitation functions were then compared with the literature data available in EXFOR database as well as with the theoretical values from the TALYS-1.8 code and the TENDL-2017 data library. The shapes of the excitation function for all the reactions were reproduced well by TALYS-1.8. In terms of absolute values, for some reactions the data are in good agreement with both the literature data and TALYS-1.8 whereas, for others there is a slight deviation either from the literature data or from the theoretical values of TALYS-1.8 and TENDL-2017.

Evolution of nuclear shapes in odd-mass yttrium and niobium isotopes from lifetime measurements following fission reactions

Lifetimes of excited states in Y99,Y101,Nb101,Nb103, and Nb105 were measured in an experiment using the recoil distance Doppler shift method at GANIL (Grand Accélérateur National d'Ions Lourds). The neutron-rich nuclei were produced in fission reactions between a U238 beam and a Be9 target. Prompt γ rays were measured with the EXOGAM array and correlated with fission fragments that were identified in mass and atomic number with the VAMOS++ spectrometer. The measured lifetimes, together with branching ratios, provide B(M1) and B(E2) values for the strongly coupled rotational bands built on the [422]5/2+ ground state in the Y and Nb nuclei with neutron number N≥60. The comparison of the experimental results with triaxial particle-rotor calculations provides information about the evolution of the nuclear shape in this mass region.9 MoreReceived 19 November 2016DOI:https://doi.org/10.1103/PhysRevC.95.034302©2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective levelsCollective modelsElectromagnetic transitionsLifetimes & widthsNuclear structure & decaysProperties90 ≤ A ≤ 149TechniquesRadiation detectorsSpectrometers & spectroscopic techniquesNuclear Physics

ESTIMATION OF LONG CONSERVATION POSSIBILITY OF IRRADIATED CONSTRUCTIONAL ELEMENTS WITH ZIRCONIUM ALLOY DURING DECOMMISSIONING OF URANIUM-GRAPHITE REACTOR

The paper deals with the constructional elements from zirconium alloys used for manufacturing of technological channels in High Power Channel-type Reactors and Industrial Uranium-Graphite reactors. For estimation of safety handling with constructional elements with zirconium alloys, the paper investigates radionuclide composition, contamination level o f the irradiated zirconium alloy (E110), reliability of radionuclides fixing and impeding properties of a barrier material from mix o f clay in relation to the radionuclides identified in an alloy. Waste with irradiated zirconium alloy (1-1,5% mas. niobium) contain neutron-activation product: 93mNb and long-life rad ionuclides 94Nb and 93Zr. Also there are 60Co, 137Cs, 90Sr and actinides in the alloy. During experiment leaching of zirconium and niobium isotopes from alloy E110 were not detected. Significant rates of leaching were observed only for 60Co and 137Cs, which were in residues on internal surface of technological channels. It was proved, that sorptive properties of clay-content material, which used to during creating of placement of long-term conservation of Industrial Uranium-Graphite reactors graphite stack, provide localization of radionuclides in case of it outcrop in a barrier material from the irradiated alloy of zirconium. It occurs because radionuclides are sorbed by a barrier material.

Application of Different Nuclides in Retrospective Dosimetry

Abstract The activities of nuclides produced via the neutron irradiation of reactor pressure vessel (RPV) steel are used to validate respective fluence calculations. Niobium, nickel, and technetium isotopes from RPV trepans of the decommissioned NPP Greifswald (VVER-440) have been analyzed. The activities were determined by TRAMO (Monte-Carlo) fluence calculations, newly applying 640 neutron-energy groups and ENDF/B7 data. Relative to earlier results, fluences up to 20 % higher have been computed, leading to somewhat better agreement between measurement and calculation, particularly in the case of Tc-99.

Shape evolution in yttrium and niobium neutron-rich isotopes

The isotopic evolution of the ground-state nuclear shapes and the systematics of one-quasiproton configurations are studied in neutron-rich odd-A Yttrium and Niobium isotopes. We use a selfconsistent Hartree-Fock-Bogoliubov formalism based on the Gogny energy density functional with two parametrizations, D1S and D1M. The equal filling approximation is used to describe odd-A nuclei preserving both axial and time reversal symmetries. Shape-transition signatures are identified in the N=60 isotopes in both charge radii and spin-parities of the ground states. These signatures are a common characteristic for nuclei in the whole mass region. The nuclear deformation and shape coexistence inherent to this mass region are shown to play a relevant role in the understanding of the spectroscopic features of the ground and low-lying one-quasiproton states. Finally, a global picture of the neutron-rich A=100 mass region from Krypton up to Molybdenum isotopes is illustrated with the systematics of the nuclear charge radii isotopic shifts.

Status of the LASER-IGISOL collaboration at the University of Jyväskylä

Recent laser spectroscopy studies at the IGISOL facility, University of Jyvaskyla have focussed on the shape transition at N = 60. A new technique of optical pumping in the ion beam cooler has given unique access to the radioactive isotopes of niobium and yttrium. Further spectroscopy from metastable states allowed nuclear moments and charge radii to be extracted for isotopes in the chains of Mo and Nb, thus exploring the extent of nuclear deformation across the entire Z = 36–42 region.

Precision mass measurements of neutron-rich yttrium and niobium isotopes

The atomic masses of neutron-rich 95–101Y and 101–107Nb produced in proton-induced fission of uranium were determined using the JYFLTRAP double Penning trap setup. Accuracies of better than 10 keV could be reached for most nuclides. The masses of 106,107Nb were measured for the first time. The energies of the isomeric states in 96Y and 100Y were measured as 1541(10) keV and 145(15) keV. The niobium isotopes appear to be systematically less bound than the values given in the latest Atomic Mass Evaluation. The new data lie in a region of the nuclear chart characterised by the transition from spherical to strongly deformed shapes. These structural changes are explored by studying different systematic trends. The data are also compared to several model predictions to test their ability to reproduce the structural changes along the isotopic chains of yttrium and niobium.

Decay study of neutron-rich zirconium isotopes employing a Penning trap as a spectroscopy tool

A new technique to produce isobarically pure ion beams for decay spectroscopy by using a gas-filled Penning trap was commissioned at the ion guide isotope separator on-line facility, IGISOL. β-decays of neutron-rich 100Zr, 102Zr and 104Zr isotopes were studied with this technique. In addition, the $\ensuremath Q_{\beta^{-}}$ values of 100,102,104Zr β-decays were determined from the direct mass measurements of zirconium and niobium isotopes performed with a high-precision Penning trap. The mass of 104Nb was directly measured for the first time and the obtained mass excess value for the longer-living (1+) state is -71823±10 keV. For the ground states of 100Nb and 102Nb the obtained mass excess values were -79802±20 keV and -76309±10 keV, respectively. The observed distribution of the β strength supports a prolate deformation assignment for 100,102,104Zr isotopes.

Early Evolution of Continents

How did the continents form, and how long ago? These questions have been the subject of debate for 30 years. As Hofmann discusses in his Perspective, results reported by Sylvester et al . ( p. 521 ) reveal that measurements of niobium and uranium isotopes indicate that ancient rocks from Western Australia are indistinguishable from modern mantle rock. This finding suggests that the mass and extent of continents today is comparable to that 2.7 billion years ago.

The Gastrointestinal Absorption and Retention of Niobium in Adult and Newborn Guinea Pigs

The gastrointestinal absorption of 95Nb ingested in milk by adult guinea pigs on a milk-supplemented diet was estimated as 0.8 +/- 0.2% (SEM; n = 4) and a value of 1.4 +/- 0.2% was obtained for guinea pigs fasted for 24 h before and 2 h after the oral administration of 95Nb in a citrate solution. The absorption in 2-day-old animals given the 95Nb-citrate solution was estimated as 1.5 +/- 0.2% (SEM; n = 3). These results support the values currently used for radiological protection purposes to calculate doses from the ingestion of niobium isotopes; these are 1% for adults and 2% for infants in the first year of life. Intestinal retention of niobium in newborn guinea pigs was low, unlike retention in other species, but consistent with observations of the retention of other elements in guinea pigs. It is considered that retention in human neonates is likely to be most similar to that in guinea pigs. Whole-body retention of 95Nb after systemic administration in citrate solution was slightly lower in 2-day-old guinea pigs than in adults, with rapid excretion of about 50% over the first day compared with 40% in adults. Subsequent clearance was similar in the two age groups with a retention half-time of about 30 days.

Inorganic ion-exchangers for the removal of zirconium, hafnium and niobium radioisotopes from aqueous solutions

Studies were made on the uptake of zirconium, hafnium and niobium isotopes onto zeolites and amorphous zirconium phosphate. Ion exchange capacities and distribution coefficients were determined and the influence of pH examined. Kinetic experiments were made to determine the rates of uptake of the radioisotopes on the exchangers and to measure the leaching of isotopes from preloaded exchangers by synthetic sea water, simulated pond water and distilled water.

(α, αxn) and (α, 2pxn) reactions on93Nb

Target foil stacks of niobium were bombarded with beams of alpha particles at incident energies ranging from 0 to 90 MeV. Cumulative cross sections for the production of95(m+g)Nb,92mNb,91mNb and90(m+g)Nb were determined by semiconductor gamma-spectrometry of the residual activity of stacked foils. On the basis of the cumulative cross sections, the thick target yields and saturation production rates of niobium isotopes have been evaluated.

PhotoneutronQ- value determinations using monochromatic photons

Neutron separation energies for the (γ, n) reaction have been determined for isotopes of niobium, cadmium, indium, antimony, tantalum, gold, thallium, lead and bismuth. A source of discrete energy photons which exceed the reactionQ-values was obtained from neutron capture on nickel and chromium placed in the core of the McMaster Nuclear Reactor. The photons illuminated the target and the photoneutrons produced were detected using a high resolution3He spectrometer. TheQ-values obtained possess greater precision, in most cases, than in any previous measurements.