Determination of70Ge(n,p)70Ga and74Ge(n,p)74Ga reaction cross sections for a fission neutron spectrum

The fission neutron spectrum averaged cross-sections for the reactions⁷⁰Ge(n,p)⁷⁰Ga and⁷⁴Ge(n,p)⁷⁴Ga have been determined. The averages of four determinations are, respectively, (3.10±0.30) mb and (0.00938±0.00059) mb. The present values are, to the authors' knowledge, the first experimental data on the fission averaged cross-section for these reactions.     

Effective threshold energies for (n, 2n) reactions induced in a fission neutron spectrum

The table presents computed values of effective threshold energies, E_eff, for (n, 2n) reactions induced in a fission neutron spectrum. E_eff-values are given for the (n, 2n) reactions for which the charge of the target nucleus is greater than 11 and for which the reaction product cannot be formed by (n, γ) reaction on another stable isotope. A closed expression is given for the integral of a fission neutron distribution of the Cranberg type, N(E), and for the mean energy of the fission neutrons with spectral distribution N(E).     

Determination of the103Rh/n, 2n/102Rh and103Rh/n, 2n/102mRh reaction cross-section,averaged over a fission spectrum

The instrumental determination of the¹⁰³Rh/n, 2n/¹⁰²Rh and¹⁰³Rh/n, 2n/^102mRh reaction cross-sections was carried out averaged over a fission spectrum. The experimental procedure is described and the results are discussed, in comparison with previous published data.     

The average cross section of the 102Pd(n,p) 102,102mRh and 103Rh(n, 2n) 102, 102m Rh reactions in a fission neutron spectrum

The mean cross sections of the ¹⁰²Pd(n,p)^102,102mRh and ¹⁰³Rh(n,2n)^102,102m Rh reactions were experimentally determined by irradiating palladium and rhodium samples for 1 week at an equivalent fission flux of 3 × 10¹³ n. cm⁻² . s⁻¹. The equivalent fission neutron flux was determined using six reference threshold reactions [⁴⁷Ti(n,p)⁴⁷Sc; ⁵⁸Ni(n,p)^58,58mCo; ⁵⁴Fe(n,p)⁵⁴Mn; ⁴⁶Ti(n,p) ⁴⁶Sc; ⁹²Mo(n,p) ^92mNb and ⁵⁵Mn(n,2n) ⁵⁴Mn] and appeared to be unperturbed.Thorough radiochemical decontaminations were required in order to separate the ^102,102mRh activities from the high thermal neutron induced palladium, silver and/or iridium activities.The results are compared with the values predicted by empirical relationships.     

A compilation of the fission spectrum average neutron cross-sections for (n, α) reactions

The (n, α) cross-sections averaged over the²³⁵U thermal fission neutron spectrum are compiled. The original values and whenever possible renormalized values are presented in parallel. The methods used for measurements and calculations are briefly discussed.     

An empirical formula for (n, 2n) reaction cross sections in the neutron energy range of about 14.5 MeV

The (n,2n) threshold reaction cross-sections, available in the literature are analysed for nuclei with 20≤Z≤92 in the neutron energy range of about 14.5 MeV. An empirical formula based on multiple regression technique is proposed for quick estimation of the (n,2n) reaction cross sections. The results obtained are compared with experimental data and those from other empirical formulae as long as byN-Z systematic. The validity of this formula is discussed.     

Determination and evaluation of fission k0-factors for correctionof the 235U(n,f) interference in k0-NAA

In order to provide a tailored solution for the correction of the ²³⁵U interference in k₀-NAA, fission k₀-factors for the analytically relevant radionuclides/gamma-lines (versus gold as the comparator), are experimentally determined in four channels of the Gent THETIS reactor. A comparison is made with former data from the literature. The new evaluated results are to be implemented in the forthcoming upgrade of the DSMKayzero software package for k₀-NAA.     

Determination of the fission averaged cross sections of some threshold reactions induced on chlorine, potassium, and calcium, and their role in the development of self-validated methods of neutron activation analysis

The feasibility of validating data obtained in the determination of chlorine, potassium, and calcium by neutron capture activation analysis, through their determination using threshold reactions has been studied. To this purpose the authors experimentally determined the following fission neutron spectrum averaged cross sections (in mb):³⁷Cl(n,p)³⁷S, 0.234±0.015;⁴¹K(n,α)³⁸Cl, 0.740±0.044;⁴²Ca(n,p)⁴²K, 3.09±0.22;⁴³Ca(n,p)⁴³K, 2.27±0.12;⁴⁴Ca(n,p)⁴⁴K, 0.074±0.013. The application of these values to the analysis of some reference materials are presented. Also, the problem of mutual interferences has been addressed for the following pairs:³⁶S(n,Γ)³⁷S and³⁷Cl(n,p)³⁷S;³⁷Cl(n,Γ)³⁸Cl and⁴¹K(n,α)³⁸Cl;⁴¹K(n,ψ)⁴²K and⁴²Ca(n,p)⁴²K.     

Determination of the 209Bi(n,γ) capture cross section at a cold neutron beam

Summary The total capture cross section of ²⁰⁹Bi was determined at the cold neutron beam PGAA-NIPS facilities at the Budapest Neutron Centre. The measurements were performed using a coaxial HPGe detector with Compton suppression. The total and partial gamma-ray production cross sections were deduced relative to the ¹⁴N(n,γ) partial gamma-ray production cross section. By using a bismuth nitrate stoichiometric compound as the sample, we excluded various systematic uncertainties. The total capture cross section is in very good agreement with the compilation of Mughaghab, but is slightly lower than the most recent value determined at the high flux reactor of the ILL in Grenoble, France. We also performed measurements using a 0.5 mm thin Bi metal disc. The relative intensities determined from the Bi disc and the compound samples are in good agreement.     

Determination of235U abundance in uranium by neutron activation on the basis of the molybdenum fission interference

The purpose of the present paper is to suggest a method for determining the²³⁵U abundance in uranium samples (compounds, metallic alloys or other uranium materials, where this element may be natural or not) through a particular application of neutron activation analysis, based on the fission interference by molybdenum. The method lies on an a priori calibration with natural uranium, thus it does not require²³⁵U certified standards.     

(n, 2n) cross sections at 14.8 MeV on some closed shell nuclides

Total cross sections for (n, 2n) reactions at 14.8 ± 0.3 MeV on rubidium, zirconium, cerium, neodymium and samarium have been measured by the activation method using a Ge(Li) detector. Short-lived activities were investigated by the cyclic activation technique. A comparison of the theoretical and the experimental cross sections shows that the statistical model values for the target nuclides having closed neutron shells are in close agreement with the experimentally obtained values. The dependence of (n, 2n) cross sections on the relative neutron excess of the target nucleus is discussed based on present results.     

Experimental k 0 and k 0-fission factors for the determination of the n(235U)/n(238U) enrichment levels and correction for 235U fission interferences in samples containing uranium

In 2010 we investigated the applicability of the current k ₀ and k ₀-fission factors for the determination of the n(²³⁵U)/n(²³⁸U) isotopic ratio in multi-elemental samples containing uranium. An overestimation 3–4 % was observed in our determinations when employing the recommended 2003 k ₀-literature. After a recalibration of all our laboratory instruments, a 3 % overestimation was still observed in this work when employing this nuclear data. Therefore we aimed at the experimental re-determination of these composite nuclear constants in order to enhance the reliability of the isotopic ratio determination method and the accuracy of our data-filtering algorithms. New k ₀-fission factors are given for 7 nuclides that are not currently present in the 2012 k ₀-database. Several additional k ₀ factors are introduced for some nuclides in this library. Our k ₀ results are also compared with those recently reported by Blaauw et al.     

Cumulative yields of short-lived ruthenium isotopes in the thermal neutron induced fission of233U,235U and239Pu

Cumulative yields of short-lived ruthenium isotopes in the thermal neutron induced fission of²³⁵U,²³⁵U and²³⁹Pu have been determined using a fast radiochemical separation technique followed by gamma spectrometry. The cumulative yields of¹⁰⁷Ru and¹⁰³Ru in²³³U (n_th, f) and¹⁰⁷Ru and¹⁰⁹Ru in²³⁹Pu (n_th, f) are determined for the first time. The measured cumulative yields are converted to chain yields assuming normal charge distribution systematics for comparison with the literature data on chain yields.     

CS(lav) and computational study of degeneracy averaged differerential cross sections and Δm-integral cross sections: Hez.sbndCO,HDz.sbnd

CC and l-average CS calculations of degeneracy averaged differential cross sections and Δm-integral cross sections have been performed for Hez.sbndCO at E = 60 cm^?1 and E = 80 cm^?1, for HDz.sbndNe at E = 254 cm^?1, and for Hez.sbndH₂ at E = 1520 cm^?1. The l_avz.sbndCS degeneracy averaged differential cross sections are generally in good agreement with the CC cross sections. The previously observed shifts in the diffraction oscillations for odd rotationally inelastic transitions for Hez.sbndCO and HDz.sbndNe do not occur due to proper phase choice and l? = l_av choice rather than l? = 1 or l′. The l_avz.sbndCS approximation gives reliable results for most Δm-integral cross sections except for those σ_cs(jm, jm′) cross sections for which the CC cross sections σ(jm;jm′) and σ(jm′;jm) differ by a large amount.     

Computerized on-line measurement the yield of short-lived bromine and iodine isotopes from thermal neutron fission of235U

The short-lived bromine and iodine isotopes from thermal neutron fission of²³⁵U have been separated from fission products by one step solvent extraction combined with an ion exchange fast chemistry system. The measured gamma spectra have been acquisited by an automatic computer on-line system. The results include experimental independent fission yields of⁸⁶Br,^134mI,^134gI,^136mI, and^136gI, the cumulative yields of⁸⁷Br,⁸⁸Br,¹³⁷I,¹³⁸I. The isomeric yield ratio of¹³⁴I and¹³⁶I has been determined and the iodine isotopic distribution curve has been constructed and analyzed.     

Isomeric yields of130Sb,132Sb,134I,and136I in the thermal neutron fission of235U

Isomer yield ratios of¹³⁰Sb,¹³²Sb,¹³⁴I and¹³⁶I isomers formed in the thermal neutron fission of²³⁵U have been calculated from our previous experimental studies that led to the identification of these species. In those studies the iodine and antimony fractions formed in fission were rapidly separated and the decay of -rays belonging to each isomer pair were followed using Ge(Li) detectors and a multichannel analyzer. The isomer ratios were calculated from growth and decay considerations of these -rays. The results are compared with the recently published values obtained with an on-line isotope separator, those from LOHENGRIN, and those from model calculations. Angular momenta of fission fragments corresponding to the measured isomer yields have also been calculated.     

Cross sections of the (n, 2n) reaction of 59Co, 58Ni, 70Ge, 90Zr and 203Tl with fission neutrons

The (n, 2n) reaction cross sections for some target nuclides were determined by means of the activation method with fission neutrons. The values obtained are 0.233 ± 0.017 mb for ⁵⁹Co, 4.06 ± 0.21 μb for ⁵⁸Ni, 0.723 ± 0.055 mb for ⁷⁰Ge, 0.1044 ± 0.0046 mb for ⁹⁰Zr, and 3.93 ± 0.11 mb for ²⁰³Tl. These results are in good agreement with the values predicted by the present authors. The cross section values calculated empirically or theoretically by several authors are compared with the observed values.