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A new optimization criterion for iterative zirconium isotope recovery by laser-assisted retardation of condensation is introduced. Generally, the optimization should be performed over the following set of parameters: gas flow pressure and temperature, target gas molar fraction, laser pulse intensity, laser beam radius, nozzle throat height and width, total processing time (number of iterations), and irradiation cell length. The laser intensity variation range should satisfy the condition of applicability of the isotope separation method used, and temperature in the mixing tank should be high enough to prevent condensation of the target gas. The evolution of the objective function for zirconium isotope separation has been evaluated as a function of the gas flow core temperature at different ambient gas pressures.

Measurements of zirconium isotopes provide insights into the formation of planetary bodies, dating nuclear explosions, or maintenance of nuclear reactors. Although many comparative measurements for the isotopic composition of zirconium have been performed using mass spectrometry, there is a lack of zirconium isotopic reference materials and only a single calibrated measurement has been reported to date by total evaporation thermal ionization mass spectrometry (TE-TIMS). In this study, we report an independent measurement of full zirconium isotopic composition in a new zirconium isotopic reference material by multicollector inductively coupled plasma MS using the regression method and two independent certified isotopic reference materials, NIST SRM 984 Rb and NIST SRM 987 Sr. Our results agree well with the recent TE-TIMS measurements and suggest a revision of the standard atomic weight of zirconium.

Zirconium isotope is a very promising tracer to investigate geological processes such as magmatic crystallization and differentiation, and to tackle the secular evolution of the continental crust. With zircon being its major hosting mineral, developing analytical technique with high accuracy, high precision and high efficiency is critical to facilitate its geological applications. This study presents an analytical method to measure zircon Zr isotope compositions by secondary ion mass spectrometry (SIMS). With careful sample preparation to limit the topography effect and instrumental tuning for maintaining its stability, we demonstrate that large geometry SIMS can provide zircon Zr isotope measurements with high accuracy, high precision and high efficiency. Based on extensive testing on our CAMECA IMS 1280HR, the recommended instrumental tuning parameters are: a primary beam intensity of ∼30 nA, a beam diameter of ∼20 × 15 μm2, a mass resolution power of 2400 and a raster size of 15 × 15 μm2, with 94Zr and 90Zr being collected by static Faraday cups via a signal accumulation time of 20 cycles × 4 s. By analyzing zircon reference materials commonly used for U–Pb and O analysis (i.e., 91500, Penglai, Plesovice, and Mudtank), we have achieved a δ94Zr repeatability of 0.04–0.07‰ (2SD, n = 33–75), and the Zr isotope compositions of zircon reference materials measured by SIMS agree remarkably well with those defined by double-spike solution methods. Our method consumes ∼1.2 ng materials in a single spot analysis (∼0.9 μm pit depth), together with its high spatial resolution (∼13 × 14 × 0.3 μm3 for data collection) and high efficiency (∼4 minutes per analysis), it is expected that our SIMS Zr isotope analytical method will be very useful for studying precious materials (e.g., zircon in lunar soil) and to facilitate big data research (e.g., detrital zircon study).

In this paper evolution of the enrichment factor for zirconium isotopes separation by the laser assisted retardation of condensation has been found for specific choice of iterative policy of isotopes recovery. It has been evaluated for a set of gas flow temperatures, corresponding to its maximal value, provided all values of other important parameters of the system such as gas flow pressure, target gas molar fraction, laser intensity, laser beam radius, irradiation chamber length, and nozzle throat height are fixed. Enrichment factor has been found by solving a set of transport equations for molar fractions of four characteristic groups represented in the gas flow (monomers, dimers, excited monomers, and epithermals) in a static approximation on each iteration.

A new analytical method for the accurate and precise determination of stable zirconium isotope ratios in geological materials by thermal ionization mass spectrometry (TIMS) is presented. Isobaric interference from Mo was largely eliminated during filament heating and further reduced by off-line Mo interference correction. This methodology allows the complete elimination of Mo interference even with a Mo/Zr ratio up to 1. Separation of Zr from natural sample matrices was achieved by using a single DGA resin column with a small usage of acids (15 mL of 7 mol L−1 HNO3 and 3 mL of 1 mol L−1 HF). A 91Zr–96Zr double spike was admixed with samples before digestion, which enabled the correction of isotope fractionation that could occur during column separation and mass spectrometry measurement. The long-term measurement reproducibility of δ94Zr is generally better than ±0.06‰ (uncertainty represented by two standard deviations, hereinafter referred to as 2 SD), assessed by repeated analyses of Zr standard reference NIST SRM 3169 and eleven geological reference materials. The Zr isotope ratios of geological reference materials BHVO-2 and AGV-2 obtained in this study are consistent with the reported values measured by MC-ICP-MS, confirming the accuracy of the proposed method. This new method greatly simplifies the chemical separation process and is particularly suitable for Zr isotope analysis of complex matrix (especially for high Mo) samples.

Conflicting results exist regarding the mechanisms, direction, and magnitude of Zr isotope fractionation in igneous systems. To better understand the origin of the fractionations observed in magmatic Zr-bearing minerals and bulk rocks, we theoretically investigated the main potential driving processes: thermodynamic equilibrium effects driven by either (i) vibrational energy or (ii) nuclear volume, and (iii) diffusion-driven kinetic effects. Vibrational equilibrium fractionation properties were estimated for zircon (^(VIII)ZrSiO₄), baddeleyite (^(VII)ZrO₂), gittinsite (^(VI)ZrCaSi₂O₇), sabinaite (Na₄^(VIII)Zr₂TiC₄O₁₆), and vlasovite (Na₂^(VI)ZrSi₄O₁₁). These properties show dependency on Zr coordination, as well as the presence of strong covalent bonds (C O, Si O by order of decreasing effect) in the material. More importantly, despite the large variety of structures investigated, the predicted mass-dependent equilibrium fractionations (Δ⁹⁴/⁹⁰Zr ∼±0.05‰ relative to zircon at 800 °C) are systematically one order of magnitude smaller than required to explain the natural variability observed to date in natural settings (δ⁹⁴/⁹⁰Zr from ∼+1 to −5‰). Likewise, careful evaluation of expected nuclear field shift (NFS) effects predict a magnitude of fractionation of ∼0.08‰ (at 800 °C), further supporting the conclusion that equilibrium effects cannot be invoked to explain extreme δ⁹⁴/⁹⁰Zr zircon values. Furthermore, the mass-dependency of all Zr isotope ratios reported in zircon crystals precludes a contribution of NFS effects larger than ∼0.01‰ on δ⁹⁴/⁹⁰Zr. On the other hand, we show that diffusion, and in particular the development of Zr diffusive boundary layers in silicate magmas during fractional crystallization, provides a viable and most likely mechanism to produce permil-level, mass-dependent isotope fractionations similar to those observed in natural systems. We propose testable scenarii to explain the large and contrasting Zr isotopes signatures in different magmatic zircons, which underline the importance of magmatic composition, Zr diffusivity, and crystallization timescales.

The ground state properties of the closed-shell 90Zr and closed-subshell 96,106Zr isotopes were investigated using a self-consistent spherical Hartree-Fock HF method and Random Phase Approximation RPA with five different Skyrme type effective nucleon-nucleon interaction: KDE0v1, BsK1, SIII, SVII and SGOI. Having a large number of Skyrme-force parameterizations requires a continuous search for the best for describing the experimental data. The presented approach attempts to accurately describe the structure of the Zirconium isotopes 90, 96, 106Zr. The calculated binding energies, root-mean squares, charge distributions, single particle energies were compared with the experimental data. Moreover, the transition strength function S(E) of the isoscalar giant monopole resonance (ISGMR), Jπ = 0+, T=0, the isoscalar giant dipole resonance (ISGDR), Jπ = 1-, T=0, isoscalar giant quadrupole resonance (ISGQR), Jπ = 2+, T=0, and isoscalar giant octupole resonance (ISGOR), Jπ = 3-, T=0 were calculated for the investigated isotopes and compared with the available experimental data.

To assess the feasibility of an innovative medical 99Mo/99mTc production route using a low-energy accelerator, we measured the excitation function of the 96Zr(α,n)99Mo reaction in the energy range from 11 to 23 MeV using a 24 MeV α beam. The present results showed higher values than past data in the peak region, although both data were almost identical above 17 MeV. The production rate of 99Mo from a 96Zr target with incident energies of α particles below 23 MeV was also estimated using the measured excitation function.

The reliability of experimental cross sections obtained for (γ, 1n), (γ, 2n), and (γ, 3n) partial photoneutron reactions using beams of quasimonoenergetic annihilation photons and bremsstrahlung is analyzed by employing data for a large number of medium-heavy and heavy nuclei, including those of 63,65Cu, 80Se, 90,91,94Zr, 115In, 112−124Sn, 133Cs, 138Ba, 159Tb, 181Ta, 186−192Os, 197Au, 208Pb, and 209Bi. The ratios of the cross sections of definite partial reactions to the cross section of the neutron-yield reaction, F i = σ(γ, in)/σ(γ, xn), are used as criteria of experimental-data reliability. By definition, positive values of these ratios should not exceed the upper limits of 1.00, 0.50, 0.33,... for i = 1, 2, 3,..., respectively. For many nuclei, unreliable values of the above ratios were found to correlate clearly in various photon-energy regions F i with physically forbidden negative values of cross sections of partial reactions. On this basis, one can conclude that correspondent experimental data are unreliable. Significant systematic uncertainties of the methods used to determine photoneutron multiplicity are shown to be the main reason for this. New partial-reaction cross sections that satisfy the above data-reliability criteria were evaluated within an experimental–theoretical method [σ eval(γ, in) = F i theor (γ, in) × σ expt(γ, xn)] by employing the ratios F i theor (γ, in) calculated on the basis of a combined photonuclear-reaction model. It was obtained that cross sections evaluated in this way deviate substantially from the results of many experiments performed via neutron-multiplicity sorting, but, at the same time, agree with the results of alternative activation experiments. Prospects of employing methods that would provide, without recourse to photoneutron-multiplicity sorting, reliable data on cross sections of partial photoneutron reactions are discussed.

We investigate the evolution of structure in the zirconium isotopes where one of the most complex situations encountered in nuclear physics occurs. We demonstrate the role of two concurrent types of quantum phase transitions, sharing a common critical point. The first type, involves an abrupt crossing of coexisting normal and intruder configurations. The second type, involves a gradual shape-phase transition within the intruder configuration, changing from weakly-deformed to prolate-deformed and finally to gamma-unstable. Evidence for this scenario is provided by a detailed comparison with experimental data, using a definite algebraic framework., 16 pages, 9 figures, Final version, Physica Scripta Focus Issue on Nuclear Shapes and Symmetries: From Experiment to Theory. arXiv admin note: substantial text overlap with arXiv:1904.09919

The cross sections for the 94Zr(n,d*)93m+gY, 96Zr(n,γ)97Z, 96Zr(n,2n)95Zr, 90Zr(n,α)87mSr, 94Zr(n,α)91Sr,90Zr(n,p)90mY, 92Zr(n,p)92Y, and 94Zr(n,p)94Y reactions have been measured in the neutron energy range of 13.5-14.8 MeV by means of the activation technique. The neutrons were produced via the D-T reaction. A high-purity germanium detector with high energy resolution was used to measure the induced γ activities. In combination with the nuclear reaction theoretical models, the excitation curves of the above-mentioned eight nuclear reactions within the incident neutron energy range from the threshold to 20 MeV were obtained by adopting the nuclear theoretical model program system Talys-1.9. The resulting experimental cross sections were analyzed and compared with the experimental data from published studies. Calculations were performed using Talys-1.9 and are in agreement with our experimental results, previous experimental values, as well as results of the theoretical excitation curves at the corresponding energies. The theoretical excitation curves generally match the experimental data well.

To obtain the neutron spectroscopic amplitudes for 90-96Zr overlaps, experimental data of elastic scattering with small experimental errors and precise optical potentials were analyzed. In this study, the elastic scattering angular distributions of C + (A = 90, 91, 92, 94, 96) were measured using the high-precision Q3D magnetic spectrometer in the Tandem accelerator. The São Paulo potential was used for the optical potential. The optical model and coupled channel calculations were compared with the experimental data. The theoretical results were found to be very close to the experimental data. In addition, the possible effects of the couplings to the inelastic channels of the targets and C projectiles on the elastic scattering were studied. It was observed that the couplings to the inelastic channels of the C projectiles could improve the agreement with the experimental data, while the inelastic couplings to the target states are of minor importance. The effect of the one-neutron stripping in the C+ elastic scattering was also studied. The one-neutron stripping channel in C + was found to be not relevant and did not affect the elastic scattering angular distributions. Our results also show that in the reactions with the considered zirconium isotopes, the presence of the extra neutron in C does not influence the reaction mechanism, which is governed by the collective excitation of the C core.

Calcium, Germanium and Zirconium isotopes can be used in semiconductors, fuel rods and as cooling materials in nuclear reactor technology. During the various occurred reactions in reactors, gas production via gamma reactions or temperature rise can severely damage the reactor materials. Therefore, it is necessary to know the effects of particles interacting with nuclear reactor materials in such cases. In this study, (γ,p) cross-sections have been calculated for 40Ca, 70Ge and 90Zr nuclei using different level density models.TALYS 1.9 and EMPIRE 3.2.3 codes have been used for level density models calculations for photon energies up to 40 MeV. Then, for these nuclei, theoretical (γ,p) cross-section calculation have been performed by using newly developed asymmetry dependent Tel et al. (2018) (γ,p) formula. Lastly, these theoretical calculations have been compared with experimental EXFOR data.

The Zirconium isotopes have been widely used in many PWR fuel cladding materials. Ignoring the resonance self-shielding effect for Zirconium isotopes, it may introduce 100–300 pcm errors in PWR reactivity predictions. The reference dilution cross section, equivalence theory, and subgroup method can be used in treating resonance self-shielding effect for Zirconium isotopes. Hence, it is important to determine the application and accuracy of these methods. In this paper, the three methods are tested with the DRAGON5.0.1 code based on the different PWR cases. The result of reactivity and absorption cross section is then compared with the Monte-Carlo code cosRMC. It indicates that the resonance self-shielding effect for Zirconium isotopes is related to the cladding region’s thickness, cladding material’s nuclide density, and water/uranium ratio. The equivalence theory and subgroup method are more flexible in treating the resonance self-shielding for Zirconium isotopes. The reference dilution cross section is limited to the typical PWR cases with a specific geometry, nuclide density, and water/uranium ratio. It is demonstrated that the equivalence theory and subgroup method can accurately treat the resonance self-shielding effect for Zirconium isotopes.

We achieve a considerable improvement in proposed schemes for the selective photoionization of odd mass zirconium isotopes. The technique implements intermediate-state alignment for isotope-selective laser excitation by broadband pulsed lasers, which incorporates the spectroscopic selection rules for the absorption of polarized light. The improvement includes newly found intermediate levels, where J = 0 character as a third excited-state intermediate, in cooperation with four-step photoexcitation (J = 2–1–1–0 scheme). Isotope selectivity (separation coefficient for 91Zr: >2400) has been identified in addition to a significant enhancement of ionization efficiency (30×) compared with previous research. A search for suitable third intermediate levels has covered over autoionizing Rydberg states in a singly ionized Zr II region (up to 58 000 cm−1). The measured autoionizing Rydberg states show high photoion yields but are not identified as favoured isotopic selectivity, as observed in the four-step photoionization. Prospects and future directions in laser even/odd-mass isotope separation are discussed.

Several zirconium isotopes are in the path of slow neutron capture (s) process, and the direct components of ($n,\ensuremath{\gamma}$) reactions can be derived from their neutron spectroscopic factors. In the present work, the angular distributions of ($^{12}\mathrm{C},^{13}\mathrm{C}$) and ($^{13}\mathrm{C},^{12}\mathrm{C}$) reactions on targets $^{90,92,94,96}\mathrm{Zr}$ were obtained using the high-precision Q3D magnetic spectrograph at the Beijing HI-13 tandem accelerator in China Institute of Atomic Energy. The distorted-wave Born approximation calculations were performed to extract the spectroscopic factors, using three different sets of Woods-Saxon potential parameters for these heavy-ion systems. The neutron spectroscopic factors for the ground state of $^{90--97}\mathrm{Zr}$ have been obtained and compared with other experimental data.

The present manuscript shows the importance of studying the isovector giant dipole resonance (IVGDR) to obtain information about the isospin-symmetry breaking and the shape evolution in excited nuclei. The $\gamma$ decay of the IVGDR was measured in the compound nuclei 80Zr and 81Rb formed at an excitation energy of $E^{\ast} = 54$ MeV and $ \langle J \rangle \approx 20\hbar$ . The reactions 40Ca+40Ca( $E_{beam} = 136$ MeV) and 37Cl+44Ca( $E_{beam} = 95$ MeV) were used to form the nuclei 80Zr and 81Rb, respectively. The experimental setup used for the $\gamma$ -rays detection was composed by the AGATA Demonstrator array coupled with large volume LaBr3:Ce detectors of the HECTOR+ array.

New spectroscopic information on electric quadrupole collectivity has recently been obtained. We report on our identification of a coexisting deformed structure in the quasi-doubly closed-shell nucleus 96Zr from our measurement of a corresponding absolute E2 intraband transition strength in electron scattering reactions and its small mixing matrix element with the spherical ground state structure. The even-mass zirconium isotopes exhibit a first order quantum shape phase transition between neutron numbers 58 and 60. We have used photon scattering reactions for a first measurement of the E2 decay strength of the nuclear 1+ scissors mode. Evidence for its 2+ rotational excitation and its extraordinarily large rotational moment of inertia are presented.

Zirconium alloys are widely used as cladding material in nuclear reactors due to their neutron transparency. Now, it is shown that 88Zr has a surprisingly high neutron capture cross-section exceeding that of other zirconium isotopes by six orders of magnitude.

A project to determine the neutron-capture cross section of long lived fission products and minor actinides has been started by using a beam-line at Japan Proton Accelerator Research Complex (J-PARC). One of the target nuclides is 93Zr, which was prepared in Oak Ridge National Laboratory. Qualitative and quantitative analyses on the sample were performed at Kyoto University. The isotopic composition of m Zr (m 90, 91, 92, 93, 94, and 96) was precisely determined by multi-collector thermal ionization mass spectrometry with

93Zr with a half-life of 1.6 Ma is produced with high yield in nuclear fission, and thus should be present as a natural or anthropogenic trace isotope in all compartments of the general environment. Sensitive measurements of this isotope would immediately find numerous applications, however, its detection at sufficiently low levels has not yet been achieved. AMS measurements of 93Zr suffer from the interference of the stable isobar 93Nb. At the Vienna Environmental Research Accelerator VERA a new multi-anode ionization chamber was built. It is optimized for isobar separation in the medium mass range and is based on the experience from AMS experiments of 36Cl at our 3-MV tandem accelerator facility. The design provides high flexibility in anode configuration and detector geometry. After validating the excellent energy resolution of the detector with 36S, it was recently used to study iron–nickel and zirconium–niobium–molybdenum isobar separation. To our surprise, the separation of 94Zr (Z = 40) from 94Mo (Z = 42) was found to be much better than that of 58Fe (Z = 26) from 58Ni (Z = 28), despite the significantly larger ΔZ/Z of the latter pair. This clearly contradicts results from SRIM-simulations and suggests that differences in the stopping behavior may unexpectedly favor identification of 93Zr. At 24 MeV particle energy, a 93Nb (Z = 41) suppression factor of 1000 is expected based on a synthetic 93Zr spectrum obtained by interpolation between experimental spectra from the two neighboring stable isotopes 92Zr and 94Zr. Assuming realistic numbers for chemical niobium reduction, a detection level of 93Zr/Zr below 10−9 seems feasible.

A method for constructing dispersive optical potentials is proposed for calculating single-particle energies in isotopic chains of spherical and nearly spherical nuclei up to nucleon drip lines. The potential of this method is demonstrated by calculating the neutron and proton single-particle energies in calcium, nickel, and zirconium isotopes. The results agree well with experimental data available for stable isotopes. Predictive calculations of single-particle spectra are performed for isotopes lying far from the beta-stability valley. A comparison of the results with the energies of nucleon separation from nuclei of mass number A and A+1 revealed features of the single-particle spectrum that are characteristic of nuclei containing classical and nonclassical magic numbers of nucleons.

Summary. Volatile metal complexes of the group 4 elements Zr and Hf with hexafluoroacetylacetonate (hfa) have been studied using short-lived radioisotopes of the metals. The new technique of physical preseparation has been employed where reaction products from heavy-ion induced fusion reactions are isolated in a physical recoil separator – the Berkeley Gas-filled Separator in our work – and made available for chemistry experiments. Formation and decomposition of M(hfa)4 (M = Zr, Hf) has been observed and the interaction strength with a fluorinated ethylene propylene (FEP) Teflon surface has been studied. From the results of isothermal chromatography experiments, an adsorption enthalpy of −ΔHa = (57 ± 3) kJ/mol was deduced. In optimization experiments, the time for formation of the complex and its transport to a counting setup installed outside of the irradiation cave was minimized and values of roughly one minute have been reached. The half-life of 165 Hf , for which conflicting values appear in the literature, was measured to be (73.9 ± 0.8) s. Provided that samples suitable for α-spectroscopy can be prepared, the investigation of rutherfordium (Rf), the transactinide member of group 4, appears possible. In the future, based on the studies presented here, it appears possible to investigate short-lived single atoms produced with low rates (e.g., transactinide isotopes) in completely new chemical systems, e.g., as metal complexes with organic ligands as used here or as organometallic compounds.

We report on the first γ-ray spectroscopy of low-lying states in neutron-rich 98,100Kr isotopes obtained from 99,101Rb(p,2p) reactions at ∼ 220 MeV/nucleon. A reduction of the 2+ 1 state energies beyond N = 60 demonstrates a significant increase of deformation, shifted in neutron number compared to the sharper transition observed in strontium and zirconium isotopes. State-of-theart beyond-mean-field calculations using the Gogny D1S interaction predict level energies in good agreement with experimental results. The identification of a low-lying (0+ 2 , 2+ 2 ) state in 98Kr provides the first experimental evidence of a competing configuration at low energy in neutron-rich krypton isotopes consistent with the oblate-prolate shape coexistence picture suggested by theory

For the N = 50-56 zirconium (Z = 40) and molybdenum (Z = 42) isotopes, the evolution of subshells is evaluated by extracting the effective single-particle energies from available particle-transfer data. The extracted systematic evolution of neutron subshells and the systematics of the excitation energy of the octupole phonons provide evidence for type-II shape coexistence in the Zr isotopes. Employing a simplistic approach, the relative effective single-particle energies are used to estimate whether the formation of low-lying octupole-isovector excitations is possible at the proposed energies. The results raise doubts about this assignment.

The first measurement of the low-lying states of the neutron-rich 110 Zr and 112 Mo was performed via in-beam γ -ray spectroscopy after one proton removal on hydrogen at ∼ 200 MeV / nucleon . The 2 + 1 excitation energies were found at 185(11) keV in 110 Zr , and 235(7) keV in 112 Mo , while the R 42 = E ( 4 + 1 ) / E ( 2 + 1 ) ratios are 3.1(2), close to the rigid rotor value, and 2.7(1), respectively. These results are compared to modern energy density functional based configuration mixing models using Gogny and Skyrme effective interactions. We conclude that first levels of 110 Zr exhibit a rotational behavior, in agreement with previous observations of lighter zirconium isotopes as well as with the most advanced Monte Carlo shell model predictions. The data, therefore, do not support a harmonic oscillator shell stabilization scenario at Z = 40 and N = 70 . The present data also invalidate predictions for a tetrahedral ground state symmetry in 110 Zr .

The excitation function for (n,p) reaction from reaction threshold to 20 MeV on five Zirconium isotopes were calculated using TALYS-1.4 nuclear model code whereby we have studied major nuclear reaction mechanisms, including direct, pre-equilibrium and compound nuclear reactions. Subsequently the level density parameters and the shell damping factors have been varied to get good agreement between the calculated cross sections and experimental nuclear data. Precise estimate of neutron induced reactions at energy levels where resonance occurs is important and complete information in this field is very much required for application in Accelerator Driven Sub-critical Systems.

Long-time experience in neutron flux moni- toring on irradiation in the LVR-15 research reactor in R y ez y proved that Au?Mn?Rb and Au?Mo?Rb(?Zn) monitor sets for short and long irradiation, respectively, are more suitable in our conditions than the most frequently used Au?Zr set. The advantages of the former monitor set have been described previously, in the present work we discuss the advantages of the latter monitor set for long irradiations in varying active core configurations of the LVR-15 reac- tor. The successful application of the Au?Mo?Rb(?Zn) monitor set has been verified by comparative determination of the neutron flux parameters a (epithermal flux distribu- tion parameter), f (thermal-to-epithermal neutron flux ratio), and Fc,Au (comparator factor) using this and the Au?Zr monitor set, and by analyses of certified reference materials, namely NIST SRMs 1547 Peach Leaves, 2711 Montana Soil, and 1633b Trace Elements in Coal Fly Ash.

Measurements of prompt γ rays in coincidence with isotopically-identified fission fragments, produced in collisions of 238 U on a 9 Be target, at an energy around the Coulomb barrier are reported. This technique provides simultaneous access to the spectroscopy of many nuclei, extending to very neutron-rich isotopes and fairly high angular momenta. The structural evolution of the neutron-rich zirconium isotopes is discussed in the light of the present measurements in Zr105,106 and in the context of the interacting boson model with a global parameterization that includes triaxiality but no shape coexistence.

The Zirconium isotopes across the N=56,58 neutron sub­shell closures have been of special interest since years, sparked by the near doubly-magic features of 96Zr and the subsequent rapid onset of collectivity with a deformed ground-state structure already in 100Zr. Recent state-of-the-art shell model approaches did not only correctly describe this shape-phase transition in the Zr isotopic chain, but alsothe coexistence of non-collective structures and pronounced collectivity especially in 96,98Zr. Theisotope 98Zr is located on the transition from spherical to deformed ground state structures. We summarize recent experimental work to obtain the B(E2) excitation strengths of the first 2+ state of98Zr, including a new experiment employing the recoil-distance Doppler-shift method following a two-neutron transfer reaction.

AMS detection of the rare isotope 93 Zr ( t 1/2 = 1.6 Ma) has application potential in two fields of research: a better determination of the 92 Zr(n,γ) 93 Zr cross section, which is relevant in astrophysical modeling of nucleosynthesis processes, and using this radionuclide as tracer in hydrological and radioactive waste studies. The biggest challenge in measuring 93 Zr at natural concentrations is adequate separation from its stable isobar 93 Nb. The Nuclear Science Laboratory at the University of Notre Dame is developing the capability to measure 93 Zr by AMS. Results are reported of first experiments, featuring the combination of a gas-filled magnet with a position-sensitive Parallel Grid Avalanche Counter and a Gas Ionization chamber in this magnet’s focal-plane.

The evaluated experimental data are presented for 14 known nuclides of mass 89 (Ge, As, Se, Br, Kr, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh). New data on high–spin excitations are available for 89 Kr, 89 Rb, 89 Sr, 89 Tc and 89 Ru, including a superdeformed structure in 89 Tc. Fluorescence studies in 89 Y have revealed a large number of new levels in 7–11 MeV range. New two–neutron transfer data are available for 89 Zr. New direct and precise measurement of atomic masses of 89 Se, 89 Br, 89 K r, 89 Rb, 89 Mo and 89 Tc have greatly improved the Q value landscape in this mass region. This work supersedes previous A=89 evaluation published in 1998Si31, and also the older ones 1989Si20, 1975Ko21, and M.W. Johns et al., Nuclear Data Tables A 8, 373 (1970). In spite of extensive experimental work on the isobaric nuclei of this mass chain several deficiencies remain. The identification of 89 Rh isotope remains unconfirmed. The half–lives of ground states of 89 Ge, 89 As and 89 Rh have not been measured, only the lower limits are estimated from time–of–flight in a reaction and experimental arrangement, where produced and identified. The decay schemes of 89 Ge, 89 As, 89 Se, 89 Ru and 89 Rh are not known, and those for 89 Tc and 89 Mo are incomplete. High–lying (neutron unbound) levels in 89 Kr, expected to be populated in the decay of 89 Br, have not been investigated. The spins and parities for levels in 89 Kr are largely unassigned, while for 89 Tc and 89 Ru, only few low–spin excitations are established. For 89 Rb, little information is available for high–spin structures. Detailed gamma–ray data are available for 88 Sr(n, γ ) 89 Sr reaction, but most of these γ rays remain unassigned in a level scheme. Excited state data are nonexistent for 89 Ge, 89 As, 89 Se, 89 Br and 89 Rh. The 89 Y and 89 Zr are the most extensively studied nuclei in A=89.

The presence of substantial systematic discrepancies between the results of different experiments devoted to determining cross sections for partial photoneutron reactions—first of all, (γ, n), (γ, 2n), and (γ, 3n) reactions—is a strong motivation for studying the reliability and authenticity of these data and for developing methods for taking into account and removing the discrepancies in question. In order to solve the first problem, we introduce objective absolute criteria involving transitional photoneutron-multiplicity functions F 1, F 2, F 3, …; by definition, their values cannot exceed 1.0, 0.5, 0.33, …, respectively. With the aim of solving the second problem, we propose a new experimental-theoretical approach. In this approach, reaction cross sections are evaluated by simultaneously employing experimental data on the cross section for the total photoneutron yield, σ expt(γ, xn) = σ expt(γ, n) + 2σ expt(γ, 2n) + 3σ expt(γ, 3n) + …, which are free from drawbacks plaguing experimental methods for sorting neutrons in multiplicity, and the results obtained by calculating the functions F theor 1 , F theor 2 , F theor 3 , … on the basis of the modern model of photonuclear reactions. The reliability and authenticity of data on the cross sections for (γ, n), (γ, 2n), and (γ, 3n) partial reactions—σ eval(γ, in) = F theor σ expt(γ, xn)—were evaluated for the 90Zr, 115In, 112,114,116,117,118,119,120,122,124Sn, 159Tb, and 197Au nuclei.

In the present work, quantitative calculations were carried out for production and depletion of the 93m Mo isomer in a relatively simple experiment using 91Zr beam ions. Such studies could be arranged at existing and operating accelerator facilities, e.g. at GSI or in JINR. The 93m Mo nuclei produced in a He gas target due to the 4He(91Zr, 2n) reaction will recoil into a gas stopper with a high velocity, being then depleted due to NEEC in highly-ionized species.

The giant impact theory is the most widely recognized formation scenario of the Earth's Moon. Giant impact models based on dynamical simulations predict that the Moon acquired a significant amount of impactor (Theia) material, which is challenging to reconcile with geochemical data for O, Si, Cr, Ti and W isotopes in the Earth and Moon. Three new giant impact scenarios have been proposed to account for this discrepancy – hit-and-run impact, impact with a fast-spinning protoEarth and massive impactors – each one reducing the proportion of the impactor in the Moon compared to the original canonical giant impact model. The validity of each theory and their different dynamical varieties are evaluated here using an integrated approach that considers new high-precision Zr isotope measurements of lunar rocks, and quantitative geochemical modelling of the isotopic composition of the impactor Theia. All analysed lunar samples (whole-rock, ilmenite and pyroxene separates) display identical Zr isotope compositions to that of the Earth within the uncertainty of 13 ppm for 96Zr/90Zr (2σ weighted average). This 13 ppm upper limit is used to infer the most extreme isotopic composition that Theia could have possessed, relative to the Earth, for each of the proposed giant impact theories. The calculated Theian composition is compared with the Zr isotope compositions of different solar system materials in order to constrain the source region of the impactor. As a first order approximation, we show that all considered models (including the canonical) are plausible, alleviating the initial requirement for the new giant impact models. Albeit, the canonical and hit-and-run models are the most restrictive, suggesting that the impactor originated from a region close to the Earth. The fast-spinning protoEarth and massive impactor models are more relaxed and increase the allowed impactor distance from the Earth. Similar calculations carried out for O, Cr, Ti and Si isotope data support these conclusions but exclude a CI- and enstatite chondrite-like composition for Theia. Thus, the impactor Theia most likely had a Zr isotope composition close to that of the Earth, and this suggests that a large part of the inner solar system (or accretion region of the Earth, Theia and enstatite chondrites) had a uniform Zr isotope composition. ISSN:0012-821X ISSN:1385-013X

Stepwise dissolutions of the carbonaceous chondrites Orgueil (CI), Murchison (CM) and Allende (CV) reveal large nucleosynthetic anomalies for Zr isotopes that contrast with the uniform compositions found in bulk meteorites. Two complementary nucleosynthetic components are observed: one enriched and one depleted in s-process nuclides. The latter component, characterized by excess 96Zr, is most distinctive in the acetic acid leachate (up to ε96Zr ≈ 50). The excess decreases with increasing acid strength and the final leaching steps of the experiment are depleted in 96Zr and thus enriched in s-process nuclides. Presolar silicon carbide grains are likely host phases for part of the anomalous Zr released during these later stages. However, by mass balance they cannot account for the 96Zr excesses observed in the early leaching steps and this therefore hints at the presence of at least one additional carrier phase with significant amounts of anomalous Zr. The data provide evidence that average solar system material consists of a homogenized mixture of different nucleosynthetic components, which can be partly resolved by leaching experiments of carbonaceous chondrites. Copyright © 2005 Elsevier Ltd.

The nat Zr(γ ,x n) 89−86 Zr reaction cross-sections were experimentally determined at the bremsstrahlung end-point energies of 12, 14, 16, 45, 50, 55, 60 and 70 MeV by activation and off-line γ-ray spectrometric technique using the 20 MeV electron linac (ELBE) at the Helmholtz-Zentrum Dresden- Rossendorf (HZDR), Dresden, Germany, and the 100 MeV electron linac at the Pohang Accelerator Lab- oratory (PAL), Pohang, Korea. The nat Zr(γ ,x n) 89−86 Zr reaction cross-sections as a function of photon energy were also calculated using the TALYS 1.4 computer code. The flux-weighted average cross-sections at the end-point energies of 12-16 and 45-70 MeV were obtained using the literature and the TALYS calculation data based on mono-energetic photons and are found to be in good agreement with the present data. It was also found that the present data and the flux-weighted literature and theoretical values for the nat Zr (γ ,x n) 89−86 Zr reaction cross-sections increase from the threshold values to a certain energy, where other reaction channels open. This indicates the role of excitation energy. However, the increasing trend of the nat Zr(γ ,x n) 89,88 Zr reaction cross-sections are sharper from the threshold value up to end-point bremsstrahlung energies of 17-22 MeV compared to the same for the nat Zr(γ ,x n) 87,86 Zr reactions. This is due to the Giant Dipole Resonance (GDR) effect besides the role of excitation energy. After a certain value, the individual nat Zr(γ, xn) reaction cross-sections decrease with the increase of bremsstrahlung energy due to opening of other reactions, which indicates partitioning of energy in different channels.

The independent isomeric yield ratios of 89g,mZr from the natZr(\( \gamma\),xn) reactions and those of 91g, mMo and 97g,mNb from the natMo(\( \gamma\),x) reactions with the bremsstrahlung end-point energy of 45-70 MeV were determined by an off-line \(\gamma\)-ray spectrometric technique using the 100 MeV electron linac at the Pohang Accelerator Laboratory, Korea. The isomeric yield ratios of 89g,mZr and 97g,mNb from the natZr(\( \gamma\), xn) and natMo(\( \gamma\),x) reactions at the bremsstrahlung end-point energy of 16MeV were also determined by the same technique using the 20MeV electron linac at Helmholtz-Zentrum Dresden-Rossendorf, Germany. The measured isomeric yield ratios of 89g,mZr, 91g,mMo, and 97g,mNb were compared with literature data to examine the role of the Giant Dipole Resonance (GDR). The isomeric yield ratios of the 89g,mZr, 91g,mMo, and 97g,mNb from the above reactions were also calculated by using the computer code TALYS 1.6 and compared with the experimental data to examine the validity of the theoretical model for independent isomeric yield ratio calculations.

The radionuclide composition and the activity level of the irradiated zirconium alloy E110, the radionuclide immobilization strength and the retention properties of the mixed clay barrier material with respect to the radionuclides identified in the alloy were investigated to perform the safety assessment of handling structural units of zirconium alloy used for the technological channels in uranium-graphite reactors. The irradiated zirconium alloy waste contained the following activation products:{93m}Nb and the long-lived {94}Nb, {93}Zr radionuclides. Radionuclides of {60}Co, {137}Cs, {90}Sr, and actinides were also present in the alloy. In the course of the runs no leaching of niobium and zirconium isotopes from the E110 alloy was detected. Leach rates were observed merely for {60}Co and {137}Cs present in the deposits formed on the internal surface of technological channels. The radionuclides present were effectively adsorbed by the barrier material. To ensure the localization of radionuclides in case of the radionuclide migration from the irradiated zirconium alloy into the barrier material, the sorption properties were determined of the barrier material used for creating the long-term storage point for the graphite stack from uranium-graphite reactors.

The main aim of this paper is to found which are the conditions the photonuclear reactions in order to accelerate the beta decay of radionuclides. Therefore, it was developed a new model where the photonuclear reaction at above the giant resonance cross section (GR) is viewed as an incident photon creating superconducting hot spot (hot belt) across nucleons from a neutron-proton(n-p) pair (a quasi-deuteron ) of the valence bosons of a unstable nuclide, accordingly with IBAF model and, followed by a thermally induced vortex crossing, which turns superconducting hot belt into the normal state (vacuum) resulting in a vortex assisted photon beta decay with the fermion (e + ,e - ) release (capture), and eventually the pair break-up by a reaction ) , ( ) , ( p or n γ γ . Since, a such model requires data on energies of vortex and on currents from inside of the nucleon, an analogue of a superconductor model was developed for the nucleon, and tested on the data of natural beta decay viewed as dark count. The results consist in obtaining a precise value of the threshold energy of the photons when the beta decay of the radionuclides is accelerated. Such efficient installations could be , for example, the laser ELI-NP in construction in Romania for the higher energy photons source.

The 94Zr(n,γ)95Zr and 90Zr(n,p)90Ym reaction cross sections were measured at neutron energies En of 2.45 MeV and 9.85 ± 0.38 MeV (average) using an activation and off-line gamma-ray spectrometric t...

In this paper we investigate the influence of various up-to-date nuclear data libraries, such as ENDF/B-VI.6, ENDF/B-VII.0 and JEFF 3.1, on the multiplication factor of the TRIGA benchmark with fuel made of enriched uranium and zirconium hydride and SB light-water reactor benchmarks with fuel made of fissile material in zirconium matrix. The calculations are performed with the Monte Carlo computer code MCNP. Differences of ∼600 pcm in k eff are observed for the benchmark model of the TRIGA reactor, while there are practically no differences in the k inf of the fuel. Therefore, an investigation is performed also for hypothetical homogeneous and heterogeneous systems with different leakage. The uncertainty analysis shows that the most important contributors to the difference in k eff are the Zr isotopes (especially 90 Zr and 91 Zr) and thermal scattering data for H and Zr in ZrH. As the differences in k eff due to the use of different cross section libraries are relatively large, there is certainly a need for a review of the evaluated cross section data of the zirconium isotopes.

We have performed a systematic calculation of low-lying dipole responses for even-even nuclei, up to zirconium isotopes including deformed nuclei within the fully self-consistent random phase approximation using the Skyrme interaction. We found the low-lying peaks in the dipole strength, so-called the pygmy dipole resonance (PDR), in every isotopic chain. The E1 strength of the PDR strongly depends on the position of the neutron Fermi level and shows a clear correlation with the occupation of the orbits with low orbital angular momenta (low-� ). We also found a strong correlation between the neutron skin thickness and the pygmy dipole strength in the region where the neutron Fermi levels are located at low-� orbits.

International audience; A new Thermal Ionization Mass Spectrometer (TIMS) analytical procedure was developed to measure with high accuracy the zirconium isotope abundance and concentration without molybdenum correction in nuclear samples. A zirconium selective separation using UTEVA column was used before the TIMS measurement in order to remove all possible isobaric interferences (Mo, Y, Nb and Ru) in the solution. The separated solution was then deposited onto a filament previously outgassed for 4 hours to reduce the molybdenum traces in the filament. Then, the filament was introduced into the TIMS source and was maintained for 4 hours at a current of 5 A (ionization filament) and 1.2 A (evaporation filament) in order to eliminate all molybdenum trace present in the filament and in the sample. This methodology allowed the zirconium isotope abundance determination without using the molybdenum interference correction equation. The analytical results obtained with a natural solution after separation is in good accordance with the reference values: bias lower than 0.16 % for the $^{90}$Zr, $^{91}$Zr, $^{92}$Zr and $^{94}$Zr isotope abundance, and a bias of $\sim$0.8 per cent for the minor isotope ($^{96}$Zr) were observed. This zirconium abundance determination methodology was used on three nuclear samples. Then, the calibration of a $^{91}$Zr spike solution was performed by reverse isotope dilution using a SPEX standard zirconium solution. The zirconium concentration determination was then performed on the three nuclear samples by isotope dilution using the SPEX standard zirconium solution and the $^{91}$Zr spike solution. The final uncertainties were estimated to be lower than 1 %

Isotope dilution in thermal ionization mass spectrometry (ID-TIMS) is a precise method for quantification of isotope ratios in geological samples, or for trace elements analysis in geological and environmental samples. This work presents an optimized ID-TIMS method for application in the field of life sciences, more precisely in the frame of a human biokinetic study on zirconium with oral and intravenous administration of two stable isotope tracers. The method allows analyzing simultaneously different stable zirconium isotopes (two isotopically enriched artificial tracers and the natural background) in human blood plasma and urine. By optimization, tracer detection limits below 1 ng ml−1 could be achieved. The biological samples were prepared by microwave-assisted acidic pressure digestion followed by extraction chromatography. The purified zirconium from the samples was measured on carbon-coated rhenium single filaments. Multiple channel electron multipliers were used as detectors. Interferences were observed from molybdenum isotopes and were corrected for based on the 95Mo count rate. Isotope ratios of zirconium were determined in ranges of 0.016–2.84 (91Zr/90Zr), 0.020–2.46 (92Zr/90Zr), 0.115–10.93 (94Zr/90Zr), and 0.004–5.70 (96Zr/90Zr). The respective relative uncertainties lay in the range of 0.03–4.2%. Typical relative uncertainties of tracer concentrations were 4%.

To understand the structure of neutron-rich nuclei and to validate the existing theoretical model for the exotic mass region, we study systematically strongly-deformed, neutron-rich even–even and odd-mass Zr isotopes with neutron number 61–66. With the projected shell model, the known experimental data are reproduced and some low-lying side-bands are predicted. The influence of the high-j h 11 / 2 neutron orbital and the g 9 / 2 proton orbital on the structure properties is investigated. For even–even isotopes, the structure of multi-quasiparticle bands is analyzed and some properties of the yrast line are described in detail. For odd-neutron isotopes, the discussion is focused on the excited single-particle configurations. Our predictions may help future experiments with identification of band structures in the very neutron-rich nuclei.

The zirconium isotope 93Zr is a long-lived pure β-particle-emitting radionuclide produced from 235U fission and from neutron activation of the stable isotope 92Zr and thus occurring as one of the radionuclides found in nuclear reactors. Due to its long half life, 93Zr is one of the radionuclides of interest for the performance of assessment studies of waste storage or disposal. Measurement of 93Zr is difficult owing to its trace level concentration and its low activity in nuclear wastes and further because its certified standards are not frequently available. A radiochemical procedure based on liquid–liquid extraction with 1-(2-thenoyl)-3,3,3-trifluoroacetone in xylene, ion exchange with Dowex resin and selective extraction using TRU resin has to be carried out in order to separate zirconium from the matrix and to analyze it by liquid scintillation spectrometry technique (LSC). To set up the radiochemical separation procedure for 93Zr, a tracer solution of 95Zr was used in order to follow the behavior of zirconium during the process by γ-ray spectrometry through measurement of the 95Zr. Then, the protocol was applied to low level waste (LLW) and intermediate level waste (ILW) from nuclear power plants. The efficiency detection for 63Ni was used to determination of 93Zr activity in the matrices analyzed. The limit of detection of the 0.05 Bq l−1 was obtained for 63Ni standard solutions by using a sample:cocktail ratio of 3:17 mL for OptiPhase HiSafe 3 cocktail.

The cross sections for formation of metastable state of 178Hf (178m2Hf, 574.215 keV, 31 y) and 179Hf (179m2Hf, 362.55 keV, 25.05 d) through reactions induced by 14.8 ± 0.2 MeV neutrons on natural hafnium were measured for the first time. The monoenergetic neutron beam was produced via the 3H(d, n)4He reaction on ZF-300-II Intense Neutron Generator at Lanzhou University. Induced gamma activities were measured by a gamma-ray spectrometer with high-purity germanium (HPGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The neutron fluence were determined by the cross section of 93Nb(n, 2n)92mNb reaction. The neutron energy in the measurement were by the cross section ratios of 90Zr(n, 2n)89m+gZr and 93Nb(n, 2n)92mNb reactions.