Study of proton induced reactions on niobium targets up to 70 MeV

Niobium is a metal with important technological applications: use as alloying element to increase strength of super alloys, as thin layer for tribological applications, as superconductive material, in high temperature engineering systems, etc. In the frame of a systematic study of activation cross-sections of charged particle induced reactions on structural materials proton induced excitation functions on Nb targets were determined with the aim of applications in accelerator and reactor technology and for thin layer activation (TLA). The charged particle activation cross-sections on this element are also important for yield calculation of medical isotope production (^88,89Zr,^86,87,88Y) and for dose estimation in PET targetry. As Niobium is a monoisotopic element it is an ideal target material to test nuclear reaction theories. We present here the integral excitation functions of ⁹³Nb(p,x)^90,93mMo, ^92m,91m,90Nb, ^86,88,89Zr, ^86,87mg,88Y and ⁸⁵Sr in the energy range 30-70 MeV, some measured for the first time at this energy range.The results were compared with the theoretical cross-sections calculated by means of the code ALICE-IPPE and with the literature data. The calculations have been carried out without any parameter adjustment. The theory reproduces the shape of the measured results well and magnitude is also acceptable.Thick target yields calculated from our fitted cross-section give reliable estimations for production of medically relevant radioisotopes and for dose estimation in accelerator technology.     

Investigation of proton induced reactions on niobium at low and medium energies

Niobium is a metal with important technological applications: use as alloying element to increase strength of super alloys, as thin layer for tribological applications, as superconductive material, in high temperature engineering systems, etc. In the frame of a systematic study of activation cross-sections of charged particle induced reactions on structural materials proton induced excitation functions on Nb targets were determined with the aim of applications in accelerator and reactor technology and for thin layer activation (TLA). The charged particle activation cross-sections on this element are also important for yield calculation of medical isotope production (^88,89Zr, ^86,87,88Y) and for dose estimation in PET targetry. As niobium is a monoisotopic element it is an ideal target material to test nuclear reaction theories. We present here the experimental excitation functions of ⁹³Nb(p,x)^90,93mMo, ^92m,91m,90Nb, ^88,89Zr and ⁸⁸Y in the energy range 0-37 MeV.The results were compared with the theoretical cross-sections calculated by means of the code ALICE-IPPE, EMPIRE-3, TALYS and with the literature data. The theory reproduces the shape of the measured results well and magnitude is also acceptable.Thick target yields calculated from our fitted cross-section give reliable estimations for production of medically relevant radioisotopes and for dose estimation in accelerator technology.     

Theoretical calculation of neutron cross sections for 90,91,92,94,96Zr in the incident energy range between 200 keV and 20 MeV

Neutron cross sections of ^{90,91,92,94,96}Zr were calculated in the incident energy (E_n) range from 200 keV to 20 MeV for the revision of the 4th version of the Japanese Evaluated Nuclear Data Library (JENDL-4.0). The calculation was carried out by using conventional nuclear reaction models such as the spherical optical model, the distorted wave Born approximation, preequilibrium models, and the multi-step statistical model. Parameter values of these nuclear models were adjusted with the aid of experimental cross sections which were published after the JENDL-4.0 evaluation. Cross sections were computed for total, elastic and inelastic scattering, (n, γ), (n, 2n), (n, p), (n, α), (n, nα), and (n, x) = (n, d) + (n, np) reactions, and they were almost consistent with the experimental data. The cross sections were also estimated for the metastable states with the half-life larger than 1 sec. The obtained results well reproduced measured cross sections for the reactions ⁹⁰Zr(n, 2n)^89mZr, ⁹¹Zr(n, x)^90mY and ⁹¹Zr(n, nα)^87mSr.     

Measurements of the Y(n,γ)Y cross-section in the neutron energy range of 13.5-14.6 MeV

The ⁸⁹Y(n,γ)^90mY cross-section has been measured at three neutron energy points between 13.5 and 14.6 MeV using the activation technique and a coaxial HPGe γ-ray detector. The data for the ⁸⁹Y(n,γ)^90mY cross-sections are reported to be 0.39 ± 0.02, 0.43 ± 0.02, and 0.38 ± 0.02 mb at 13.5 ± 0.2, 14.1 ± 0.1, and 14.6 ± 0.2 MeV incident neutron energies, respectively. The first data for the ⁸⁹Y(n,γ)^90mY reaction at neutron energy points of 13.5 and 14.1 MeV are presented. The natural high-purity Y₂O₃ powder was used as target material. The fast neutrons were produced by the T(d,n)⁴He reaction. Neutron energies were determined by the method of making cross-section ratios of ⁹⁰Zr(n,2n)^89m+gZr and ⁹³Nb(n,2n)^92mNb reactions, and the neutron fluencies were determined using the monitor reaction ⁹³Nb(n,2n)^92mNb. The results obtained are compared with existing data.     

Deuteron-Induced Cross Section Calculations of Some Structural Fusion Materials

The development of fusion materials for the safety of fusion power systems and understanding nuclear properties is important. The reaction cross-section data have a critical importance on fusion reactors and development for fusion reactor technology. In this study, the theoretical cross sections of some structural fusion materials such as Cr, V, Fe, Ni, Zr and Ta in deuteron-induced reactions have been investigated. The new calculations on the excitation functions of ⁵⁰Cr(d, α)⁴⁸V, ⁵¹V(d, 2n)⁵¹Cr, ⁵¹V(d, 4n)⁴⁹Cr, ⁵⁴Fe(d, α)⁵²Mn, ⁵⁴Fe(d, n)⁵⁵Co, ⁵⁸Ni(d, α)⁵⁶Co, ⁹⁶Zr(d, n)⁹⁷Nb, ⁹⁶Zr(d, 2n)⁹⁶Nb and ¹⁸¹Ta(d, 2n)¹⁸¹W reactions have been carried out up to 90 MeV incident deuteron energies. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve the geometry dependent hybrid model and hybrid model. Equilibrium effects have been calculated according to the Weisskopf–Ewing model. The ALICE/ASH computer code has been used in all calculations. The calculated results have been compared with the experimental data existing in EXFOR database and found to be in good agreement.     

Activation cross sections for (n, p) reactions on nickel isotopes induced by neutrons around 14 MeV

The cross sections of ⁵⁸Ni(n, p)^58(m+g)Co,⁶⁰Ni(n, p)^60mCo,⁶¹Ni(n, p)⁶¹Co and ⁶²Ni(n, p)^62mCo reactions induced by neutrons around 14 MeV were measured using activation technique and a coaxial HPGe γ-ray detector. The natural nickel foils of 99.9% purity were used as target materials. Fast neutrons were produced by the T(d, n)⁴He reaction. The neutron flux was determined using the monitor reaction ²⁷Al(n, α)²⁴Na and the neutron energies were measured with the method of cross-section ratios for ⁹⁰Zr(n, 2n)⁸⁹Zr to ⁹³Nb(n, 2n)^92mNb reactions. The results of this work are compared with the collected partial recent data published previously and the estimations obtained from the published empirical formula based on the statistical model with dependence on the Q-value and odd-even effect taken into consideration.     

Direct neutron spectrum measurement to validate Zr(n,2n) reaction cross-section at 14 MeV

Lithium zirconate, Li₂ZrO₃, is known as a candidate blanket material in a fusion reactor. Various neutronics benchmark experiments for zirconium have thus been carried out so far. According to the independent benchmark studies by two parties, the neutron spectrum calculations show fairly large overestimation for most evaluated nuclear data libraries. However, the reason has not yet been made clear up to now. The author's group expects it would be due to a problem of evaluation for the ^natZr(n,2n) reaction cross-section, because the cross-section measurement is basically not possible with the foil activation method for zirconium isotopes except for ⁹⁰Zr.In the present study, two neutrons emitted from ^natZr(n,2n) reaction have been measured directly to investigate the reason for the above overestimation. The measurement was done with our own special technique of detecting angle-correlated neutrons by the coincidence detection technique and the pencil-beam DT neutron source of FNS, JAEA. Angle-correlated energy differential cross-sections for ^natZr(n,2n) reaction were successfully measured. The obtained total cross-section above the emitted neutron energy of 800 keV was fairly larger than the one evaluated in JENDL-3.3. The total cross-section of ^natZr(n,2n) reaction was estimated by extrapolating the spectrum down to zero energy taking into account the nuclear temperature. The estimated cross-section value with the nuclear temperature of 1 MeV, which is larger than the one adopted in JENDL-3.3, was in acceptable agreement with JENDL-3.3. It is suggested from the result that the disagreement pointed out in the previous benchmark studies may be due to inappropriate nuclear temperature used in the evaluation. Further investigation of the nuclear temperature employed in the nuclear data evaluation should thus be carried out once again.     

Cross-section measurements for short-lived isotopes of 46Ti, 75As and 92Mo at the neutron energies from 13.6 to 14.9 MeV

Cross-sections were measured at neutron energies from 13.6 to 14.9 MeV for the reactions ⁴⁶Ti(n,p) ^46mSc, ⁷⁵As(n,p) ^75mGe and ⁹²Mo(n,2n) ^91mMo leading to short-lived products. Corrections were made for the effects of gamma ray attenuation, coincidence summing, pulse pile-up, dead time, neutron flux fluctuations and scattered low energy neutrons. Statistical model calculations taking into account precompound effects were also performed.     

Excitation functions of the proton induced nuclear reactions on natural zirconium

Excitation functions for the ^natZr(p,xn)^{90,92m,95g,96}Nb, ^natZr(p,pxn)^88,89Zr, and ^natZr(p,αxn)^{86,87m,87mg,88}Y reactions were measured by using a stacked-foil activation technique in combination with HPGe γ-ray spectroscopy using the MC50 cyclotron at the Korean Institute of Radiological and Medical Sciences, Korea. In this way the proton beam energy range 4-40 MeV was covered. We report new data for these processes. The data were compared with the results of precompound-hybrid model calculations, whereby only a partial agreement was obtained.     

Cross-section measurements for (n, 2n), (n,p) and (n, α) reactions on strontium isotopes at the neutron energy about 14 MeV

Cross-sections for ⁸⁴Sr(n, 2n)⁸³Sr, ⁸⁶Sr(n, 2n)^85mSr, ⁸⁶Sr(n, 2n)⁸⁵Sr, ⁸⁸Sr(n, 2n)^87mSr, ⁸⁴Sr(n, p)⁸⁴Rb, ⁸⁶Sr(n, p)⁸⁶Rb, ⁸⁸Sr(n, p)⁸⁸Rb and ⁸⁸Sr(n, α)^85mKr reactions have been measured at neutron energies from 13.5 to 14.6 MeV using activation technique and by means of γ-ray spectrometry. The neutron flux was determined using the monitor reaction ⁹³Nb(n, 2n)^92mNb and the neutron energies were measured by the method of cross-section ratios for ⁹⁰Zr(n, 2n)⁸⁹Zr to ⁹³Nb (n, 2n)^92mNb reactions. The results of present work are compared with data published previously.     

Proton energy determination using activated yttrium foils and ionization chambers for activity assay

Excitation functions of the ⁸⁹Y(p, xn) nuclear reactions were measured up to 18 MeV by the conventional activation method using the stacked-foil technique, and the irradiation of single foils. Activity assays of the irradiated foils were performed via ionization chamber and gamma spectroscopy methods. Activity ratios of the activation products were measured in two different facilities and evaluated for use as a practical and simple method for proton energy determinations. Cross section values measured in this work were compared with published data and with theoretical values as determined by the nuclear reaction model code EMPIRE II. In general, there was a good agreement between the experimental and theoretical values of the cross section data. Activity ratios of the isomeric and ground state of ⁸⁹Zr measured via ionization chamber were found to be useful for proton energy determinations in the energy range from 7 to 15 MeV. Proton energies above 13 MeV were accurately determined using the ^89gZr/⁸⁸Zr and ^89gZr/⁸⁸Y activity ratios measured via gamma spectroscopy.     

Photo-neutron Cross Section Calculations of Several Structural Fusion Materials

In this study, the theoretical photo-neutron cross-sections produced by (γ,n) reactions for several structural fusion materials such as ⁵¹V, ⁵⁵Mn, ⁵⁸Ni, ^90,91,92,94Zr, and ¹⁸¹Ta have been investigated in the incident energy range of 7–40 MeV. Reaction cross-sections as a function of photon energy have been calculated theoretically using the PCROSS and TALYS 1.2 computer codes. TALYS 1.2 default and pre-equilibrium models have been used to calculate the pre-equilibrium photo-neutron cross-sections. For the reaction equilibrium component, PCROSS Weisskopf-Ewing model calculations have been preferred. The calculated results have been compared with each other and against the experimental data in the existing databases EXFOR and TENDL-2011. PCROSS Weisskopf-Ewing model calculations show a similar structure with experimental data but they are higher than the experimental values for all reactions except for ⁹⁰Zr(γ,n)⁸⁹Zr reaction. Generally, TALYS 1.2 default and pre-equilibrium model cross-section calculations are the best agreement with the experimental data for all reactions except for ⁵⁸Ni(γ,n)⁵⁷Ni reaction along the incident photon energy in this study. The TALYS 1.2 curves fit the TENDL-2011 data the best. If photo-neutron cross-section data is needed for an isotope where there is no experimental data available for comparison, TALYS 1.2 pre-equilibrium option has been recommended.     

Measurement of the activation cross section for the (p,xn) reactions in niobium with potential applications as monitor reactions

Excitation functions of the ⁹³Nb(p,n)^93mMo, ⁹³Nb(p,pn)^92mNb and ⁹³Nb(p,αn)⁸⁹Zr nuclear reactions were measured up to 17.4 MeV by the conventional activation method using the stacked-foil technique. Stacks were irradiated at different incident energies on the TR19/9 cyclotron at the Edmonton PET Centre. The potential of the measured excitation functions for use as monitor reactions was evaluated and tested by measuring activity ratios at a different facility. Single Nb foils were irradiated at incident energies in the range from 12 to 19 MeV on the TR19/9 cyclotron at Brookhaven National Laboratory. Results are compared with the published data and with theoretical values as determined by the nuclear reaction model code EMPIRE.     

Cross-Section Calculations on Several Structural Fusion Materials for (γ,3n) Reactions in the Photon Energy Range of 20–110 MeV

In this study, photo-neutron cross-sections of (γ,3n) reactions for several structural fusion materials such as ⁵⁵Mn, ⁶⁵Cu, ⁹⁴Zr, ^98,100Mo, ¹⁸¹Ta and ¹⁸⁶W have been investigated in the incident photon energy range of 20–110 MeV. Theoretical cross-section calculations, based on theoretical nuclear reaction models, have been carried out using the PCROSS, EMPIRE 3.1 and TALYS 1.6 codes. EMPIRE 3.1 exciton, TALYS 1.6 two component exciton and TALYS 1.6 pre-equilibrium models have been used to calculate the pre-equilibrium photo-neutron cross-sections. For the equilibrium cross-section calculations, PCROSS Weisskopf–Ewing model has been preferred. The calculated results have been compared with each other and against the experimental nuclear reaction data (EXFOR). Except the ⁶⁵Cu(γ,3n)⁶²Cu reaction, all model equilibrium and pre-equilibrium cross-section calculations exhibit generally good agreement with the experimental values for all reactions used in this study. TALYS 1.6 two component exciton model can be recommended, if experimental photo-neutron cross-section data are not available or are unlikely to be produced because of the experimental difficulties.     

Measurement of isomeric yield ratios for 90Zr(γ, n)89m,gZr, natZr(γ, xn1p)86m,gY, and 89Y(γ, xn)87m,g,86m,gY reactions with 50-, 60-, and 70-MeV bremsstrahlung

We measured the isomeric yield ratios in the photonuclear reactions of ^natZr(γ, n)^89m,gZr, ^natZr(γ, xn1p)^86m,gY, and ⁸⁹Y(γ, xn)^87m,g,86m,gY by the activation method. The high-purity natural Zr and Y metallic foils in disc shape were irradiated with uncollimated bremsstrahlung beams of 50-, 60-, and 70-MeV generated from an electron linear accelerator at Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometric system consisting of a high-purity germanium detector and a multichannel analyzer. The obtained isomeric yield ratios in the formation of ^89m,gZr, ^87m,gY, and ^86m,gY are compared with the corresponding values found in the literature. The measured isomeric yield ratios at the bremsstrahlung energies of 50-, 60-, and 70-MeV are the first measurement except ⁸⁷Y at 50-MeV bremsstrahlung.     

Evaluation Methods of Resonance Absorption for System with Pellet Surrounded by Fuel Solution

Abstract

The reaction cross sections of ²⁷Al(n, p)²⁷Mg, ²⁷Al(n, a)²⁴Na, ⁵⁶Fe(n, p)⁵⁶Mn, ⁹⁰Zr(n, 2n)^89m+gZr and ⁹³Nb(n, 2n)^92mNb have been measured by the activation method in an energy range of 13.3–14.9 MeV using the intense D-T neutron source, FNS. Absolute flux was determined by the associated α-particle counting method incorporated with neutron spectra obtained from both a Monte Carlo calculation and a time-of-flight measurement. Corrections were extensively performed not only for the neutron flux determination, but also for the low energy neutron contribution to the reaction rates. The present data were compared with comprehensive evaluations as well as recent experimental data. The measured cross sections of ²⁷Al(n, a)²⁴Na, ⁵⁶Fe(n, p)⁵⁶Mn and ⁹⁰Zr(n, 2n)^89m+gZr are generally in good agreement within experimental errors with the values in both the JENDL Dosimetry File and IRDF-90. It is also shown that there are the overestimation of the cross sections for ⁹³Nb(n, 2n)^92mNb in the JENDL Dosimetry File, and the over- estimation and underestimation of the cross section for ²⁷Al(n, p)²⁷Mg in the JENDL Dosimetry File and IRDF-90, respectively.     

Nuclear Data Sheets for A = 91

Experimental nuclear structure and decay data for all known A=91 nuclides (As, Se, Br, Kr, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd) have been evaluated. This evaluation, covering data received by 1 September 2013, supersedes the 1998 evaluation by C. M. Baglin published in Nuclear Data Sheets86, 1 (1999) (15 December 1998 literature cutoff), and subsequent evaluations by C. M. Baglin added to the ENSDF database for Kr, Sr and Zr (29 December 2000 literature cutoff) and by B. Singh for ⁹¹Tc (6 November 2000 literature cutoff).     

Comparison of Level Density Models for the <Superscript>60,61,62,64</Superscript>Ni(p,n) Reactions of Structural Fusion Material Nickel from Threshold to 30 MeV

The knowledge of level density for reaction cross-section calculations are needed for various applications such as fission and fusion reactor design, accelerator driven sub-critical systems, nuclear medicine, neutron capture and astrophysics. In this study, the excitation functions for (p, n) reactions from reaction threshold to 30 MeV proton incident energy on ⁶⁰Ni, ⁶¹Ni, ⁶²Ni and ⁶⁴Ni isotopes were calculated using TALYS 1.6 nuclear code involving the level density models. This is of importance to the validation of nuclear model approaches with increased predictive power. There are several models of level density that can be used to predict cross-section. In this work, the (p, n) cross-sections would be calculated using three different model of level density, such as constant temperature model, back-shifted fermi gas model and generalized superfluid model on ^60,61,62,64Ni reactions. The (p, n) reaction cross-section calculations for ^60,61,62,64Ni target nuclei were compared with each other and the experimental nuclear reaction data obtained from EXFOR database.     

Measurements of activation cross sections for Lu(n, α)Tm,Lu(n, α)Tm and Lu(n, p)Yb reactions induced by neutrons around 14 MeV

The cross sections for the ¹⁷⁵Lu(n, α)¹⁷²Tm, ¹⁷⁶Lu(n, α)¹⁷³Tm and ¹⁷⁵Lu(n, p)^175m+gYb reactions have been measured in the neutron energy range of 13.5–14.8 MeV using the activation technique. The first data for ¹⁷⁵Lu(n, α)¹⁷²Tm reaction cross sections are presented. In our experiment, the fast neutrons were produced via the ³H(d, n)⁴He reaction on K-400 Neutron Generator at Chinese Academy of Engineering Physics (CAEP). Induced gamma activities were measured by a high-resolution (1.69 keV at 1332 keV for ⁶⁰Co) 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 fluences were determined by the cross section of ⁹³Nb(n, 2n)^92mNb or ²⁷Al(n, α)²⁴Na reactions. The neutron energy in the measurement was by the cross section ratios of ⁹⁰Zr(n, 2n)^89m+gZr and ⁹³Nb(n, 2n)^92mNb reactions. The results were discussed and compared with experimental data found in the literature and with results of published empirical formulae.     

Activation cross-section for reactions induced by 14 MeV neutrons on natural silver

Cross-sections for (n, 2n), (n, p), and (n, α) reactions have been measured on silver isotopes at the neutron energies from 13.5 to 14.8 MeV using the activation technique in combination with high-resolution γ-ray spectroscopy. Corrections were made for the literature cross-sections of ¹⁰⁹Ag(n, 2n) ^108mAg reaction with incorrect half-life of product ^108mAg. Neutrons were produced via the ³H(d, n)⁴He reaction using solid TiT. The neutron fluences were determined using the monitor reaction ²⁷Al(n, α)²⁴Na. The neutron energy in this measurement was determined by cross-section ratios for the ⁹⁰Zr(n, 2n) ^89m+gZr and ⁹³Nb(n, 2n)^92mNb reactions. Data are reported for the following reactions: ¹⁰⁹Ag(n, 2n)^108mAg, ¹⁰⁷Ag(n, 2n)^106mAg, ¹⁰⁹Ag(n, p)^109m+gPd, and ¹⁰⁹Ag(n, α)^106mRh. The cross-sections were discussed and compared with experimental data found in the literature, and with the comprehensive evaluation data in ENDF/B-VII, JENDL-3.3, and JEFF-3.1/A libraries.