Determination of the fission-neutron averaged cross sections of some high-energy threshold reactions of interest for reactor dosimetry

For three high threshold reactions, we have measured the cross sections averaged over a ²³⁵U fission neutron spectrum. The measured reactions, and corresponding averaged cross sections found, are: ¹²⁷I(n,2n)¹²⁶I, (1.36±0.12) mb; ⁹⁰Zr(n,2n)^89mZr, (13.86±0.83) mb; and ⁵⁸Ni(n,d+np+pn)⁵⁷Co, (274±15) b; all referred to the well known standard of (111±3) mb for the ⁵⁸Ni(n,p)^58m+gCo averaged cross section. The measured cross sections are of interest in nuclear engineering for the characterization of the fast neutron component in the energy distribution of reactor neutrons.     

Fission neutron spectrum averaged cross sections for threshold reactions on arsenic

Summary We have measured the cross sections, averaged over a ²³⁵U fission neutron spectrum, for the two high threshold reactions: ⁷⁵As(n,p)^75mGe and ⁷⁵As(n,2n)⁷⁴As. The measured averaged cross sections are 0.292±0.022 mb, referred to the 3.95±0.20 mb standard for the ²⁷Al(n,p)²⁷Mg averaged cross section, and 0.371±0.032 mb referred to the 111±3 mb standard for the ⁵⁸Ni(n,p)^58m+gCo averaged cross section, respectively. The measured averaged cross sections were also evaluated semi-empirically by numerically integrating experimental differential cross section data extracted for both reactions from the current literature. The calculations were performed for four different representations of the thermal-neutron-induced ²³⁵U fission neutron spectrum. The calculated cross sections, though depending on analytical representation of the flux, agree with the measured values within the estimated uncertainties.     

Use of the Absolute Parametric Method to Evaluate the Analytical Significance of Threshold Reactions on P, Si, Al and Mg by NAA

We investigated the use of threshold reactions on magnesium, aluminum, silicon and phosphorus to determine elemental concentrations and also to correct analytical interferences, using the parametric method. The reactor neutron spectrum averaged cross sections of the threshold reactions on these elements were referred to the (111±3) mb value for the ⁵⁸Ni(n,p)^58g+mCo reaction cross section. The results of the cross section measurements are: ²⁵Mg(n,p)²⁵Na, 1.57±0.12 mb; ²⁸Si(n,p)²⁸Al, 5.68±0.25 mb; ²⁹Si(n,p)²⁹Al, 3.02±0.15 mb; ³⁰Si(n,)²⁷Mg, 0.1346±0.0090 mb; and ³¹P(n,)²⁸Al, 1.912±0.083 mb. The values for the cross sections of the following reactions: ²⁴Mg(n,p)²⁴Na, 1.441±0.092 mb; ²⁷Al(n,p)²⁷Mg, 3.84±0.18 mb; and ²⁷Al(n,)²⁴Na 0.721±0.028 mb were re-measured to check the methodology. We present the application of these values to the analysis of some reference materials.     

Activation cross sections and isomeric cross section ratios for 184Os(n,2n)183m,gOs, 190Os(n,p)190m,gRe and 86Sr(n,2n)85m,gSr reactions from 13.5 to 14.8 MeV

The cross sections for the ¹⁸⁴Os(n,2n)^183m,gOs, ¹⁹⁰Os(n,p)^190m,gRe and ⁸⁶Sr(n,2n)^85m,gSr reactions and their isomeric cross section ratios σ _m /σ _g have been measured in the neutron energy range of 13.5–14.8 MeV using the activation technique. Nuclear model calculations using the code HFTT, which employs the Hauser-Feshbach (statistical model) and exciton model (precompound effects) formalisms, were undertaken to describe the formation of the products. The total cross sections for ¹⁸⁴Os(n,2n)¹⁸³Os, ¹⁹⁰Os(n,p)¹⁹⁰Re and ⁸⁶Sr(n,2n)⁸⁵Sr reactions are compared with the experimental data found in the literature, with results of published empirical formulae, with values of model calculations including the pre-equilibrium contribution, and with the evaluation data of JEFF-3.1/A or ENDF/B-VII.     

Measurements of 60Ni(p,n)60Cu reaction cross-sections and covariance analysis of the uncertainty

The cross sections of the ⁶⁰Ni(p,n)⁶⁰Cu reaction from threshold energy to?~?20 MeV have been measured by employing stack foil activation technique and off-line γ-ray spectrometry. The uncertainties for the reaction cross sections have been estimated by applying covariance analysis and least square method. The measured cross-sections are found to be in agreement with most of the literature data available in EXFOR database. The excitation function of the ⁶⁰Ni(p,n)⁶⁰Cu reaction was also theoretically calculated by using the TALYS-1.9 code. The excitation functions of ⁶⁰Ni(p,n)⁶⁰Cu reaction from TALYS-1.9 and TENDL-2017 follow a similar trend as of the experimental data of present work and literature but are little higher around the peak cross-section region.

     

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.     

Production of 52Fe by the 55Mn(p,4n)52Fe reaction and milking of 52mMn from 52Fe

The excitation functions were measured for the nuclear reactions of 55Mn(p,4n)52Fe and 55Mn(p,n)55Fe by using thin manganese disks, specially prepared under a pressure of 200-250 kg/cm2 at 400-500 degrees C for 0.5-1 hour. The maximum cross section in the excitation function for the 55Mn(p,4n)52Fe reaction was found to be 1.4mb at Ep = 54 MeV. From the yield curve, 24.8 MBq/microA h (670 muCi/microA h) of 52Fe was estimated to be produced with 0.45% 55Fe contamination in the energy region between 73 and 39 MeV. Iron-52 was produced in the yield of 85-93% to the expected value from the yield curve in the energy region of 44-60 MeV. For the separation of 52Fe, the radiochemical yield of 52FeCl3 was 70-92% and its radionuclidic purity was higher than 99%. Manganese-52m was obtained repeatedly by eluting the anion exchange column adsorbing 52Fe with 6N-HC1 in 99.9% radionuclidic purity and 86% yield to the expected value. The amount of 55Fe in a large quantity of 52Fe could be determined in 1-2 days from end of bambardment (EOB) by analyzing decay curve of Mn-Ka-X ray from 52Fe and 55Fe.     

A compilation of cross-sections for charged particle production by 14 MeV neutrons for Fe,Co and Ni isotopes

A compilation of the (n, p), (n, n′p), (n, α, (n, n′α) and (n,³He) cross-sections for⁵⁴Fe,⁵⁶Fe,⁵⁷Fe−⁵⁸Fe,⁵⁹Co,⁵⁸Ni,⁶⁰Ni,⁶¹Ni,⁶²Ni and-⁶⁴Ni by 14 MeV neutrons is presented in the from of a table containing the results of some 180 different measurements, mainly obtained by activation analysis. Brief assessments of the experimental methods and the data status are given.     

A compilation of cross-sections for the reaction (n, 2n) with 14 MeV neutrons for some important fusion reactor structural materials

A compilation of the cross section (n, 2n) for⁴⁶Ti,^{50, 52, 54}Cr,⁵⁵Mn,^54,56Fe,⁵⁹Co,^58,59Ni,⁹³Nb,^92,100Mo with 14 MeV neutrons is presented in the form of a table containing the results of nearly 190 different measurements, mainly obtained by activation analysis. Brief assessment of the experimental methods and the data status are given.     

(n,n′) production of99mTc by252Cf fission neutrons

Activation technique was employed to determine the²⁵²Cf spectrum averaged cross section of the⁹⁹Tc(n,n)^99mTc reaction. Two different -spectrometric methods were applied. One of the measurements was relative to that of the cross-section value of¹¹⁵In (n,n)^115mIn reaction, while the other one was absolute. The measured values are 179±49 mb and 195±43 mb for the relative and absolute measurement, respectively.     

The measurement of neutron-induced radionuclides from Chinese nuclear weapons tests

The concentrations of neutron-induced radionuclides have been measured in ground level air during the period between 1976 and 1981 at Nagoya (35° N, 137° E), Japan. Six Chinese atmospheric nuclear weapons tests were conducted by the government of China at Lop Nor (40° N, 90° E) during the period 1976–1981. The Chinese nuclear tests of November 17, 1976 (the 21st test) and October 16, 1980 (the 26th test), high-yield devices, produced⁵⁴Mn,⁵⁵Fe and⁸⁸Y whose production reactions are⁵⁴Fe(n, p),⁵⁶Fe(n, 2n) and⁸⁹Y(n, 2n), respectively. The tests of September 26, 1976 (the 19th test), September 17, 1977 (the 22nd test) and March 15, 1978 (the 23rd test), low-yield devices, produced⁵⁴Mn,⁵⁷Co and⁵⁸Co whose production reactions are⁵⁴Fe(n, p),⁵⁸Ni(n, pn) and⁵⁸Ni(n, p) respectively. No neutron activation product from the 24th test (December 14, 1978) was observed.     

Activation cross-sections for some (n, 2n), (n,p) and (n, γ)-reactions

The average fission neutron cross-sections of the reactions²³³U(n, 2n)²³²U,⁶⁰Ni(n, p)⁶⁰Co and²⁷Al(n, p)²⁷Mg and the resonance integrals of the (n, γ)-reactions of the nuclides¹⁸¹Ta,¹⁷⁶Lu,¹⁷⁵Lu,⁶⁴Ni,⁵⁹Co and²⁶Mg have been determined by the activation method following the well-known conventions. The results verify some of the existing values and present data for hitherto unknown or poorly known reactions.     

Cross section measurements for (n, p) and (n, 2n) reactions of rare-earth isotopes at neutron energies from 13.5 to 14.6 MeV

Cross sections for (n, p) and (n, 2n) reactions have been measured on some rare-earth isotopes at neutron energies of 13.5-14.6 MeV using activation technique. Data are reported for the following reactions:¹⁵⁰Nd(n, 2n) ¹⁴⁹Nd, ¹⁴⁸Nd(n, 2n) ¹⁴⁷Nd, ¹⁴²Nd(n, 2n) ¹⁴¹Nd, ¹⁶⁰Gd(n, 2n) ¹⁵⁹Gd, ¹⁵⁸Gd(n, p) ¹⁵⁸Eu, ¹⁴⁶Nd(n, p) ¹⁴⁶Pr, ¹⁴¹Pr(n, p) ¹⁴¹Ce and ¹³⁹La(n, p) ¹³⁹Ba. The neutron fluences are determined by the cross sections of ²⁷Al(n, a) ²⁴Na and ⁹³Nb(n, 2n) ^92mNb reactions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Activation cross-section measurements for producing short-lived nuclei with 14 MeV neutrons—Ge, Pd, Yb

Activation cross sections for ⁷⁰Ge(n,p)⁷⁰Ga, ⁷⁴Ge(n,p)⁷⁴Ga, ¹⁰⁸Pd(n,p)¹⁰⁸Rh, ¹¹⁰Pd(n,α)¹⁰⁷Ru, and ¹⁷⁴Yb(n,p)¹⁷⁴Tm reactions producing short-lived nuclei with half-lives of several minutes were measured in the energy between 13.5 and 14.8 MeV using activation technique in this work. All cross-section values were relatively obtained on the basis of the standard cross section of ⁹³Nb(n,2n)^92mNb or ²⁷Al(n,α)²⁴Na, and the neutron energies were measured by the method of cross-sectional ratios for ⁹⁰Zr(n,2n)^89m+gZr to ⁹³Nb(n,2n)^92mNb reactions. Careful attention on corrections was paid to neutron irradiation and induced activities measurement. The measured results were discussed and compared with the previous works.     

Neutron energy spectrum determination and flux measurement using MAXED, GRAVEL, and MCNP for RACE experiments

Stainless steel flux wires were used to determine the neutron energy spectra and total flux during the Reactor Accelerator Coupling Experiments (RACE) at The University of Texas at Austin. A LINAC electron accelerator produced 20 MeV electrons at a power of 1.6 kW, which struck a tungsten-copper target to produce bremsstrahlung radiation and photoneutrons. The neutrons produced in the target were multiplied by the subcritical core of a Triga reactor. The purpose of the RACE experiments is to develop a sub-critical accelerator driven system that would be capable of transmuting actinides from spent fuel. Flux measurements were made with 1.58 mm diameter stainless steel wires placed throughout the core between the fuel rods and cadmium covered and uncovered gold and indium foils above the target. The MAXED and GRAVEL computer codes were used to perform the spectrum unfolding. The composition of the stainless steel wires was determined using neutron activation analysis with comparators prior to the flux measurement. The reactions measured in the stainless steel to determine the flux were ⁵⁰Cr(n,γ)⁵¹Cr, ⁵⁸Ni(n,p)⁵⁸Co, ⁵⁴Fe(n,p)⁵⁴Mn, and ⁵⁸Fe(n,γ)⁵⁹Fe. Flux measurements agreed well with an MCNP simulation of the experiment.     

Cross-sections for formation of 99mTc through natRu(n,x) 99mTc reaction induced by neutrons at 13.5 and 14.8 MeV

The cross-sections for formation of metastable state of ⁹⁹Tc (^99mTc, 140.511 keV, 6.01 h) through ^natRu(n,x)^99mTc reaction induced by 13.5 MeV and 14.8 MeV neutrons were measured. Fast neutrons were produced via the ³H(d,n)⁴He reaction on the K-400 neutron generator. Induced gamma activities were measured by a high-resolution gamma-ray spectrometer with a high-purity germanium (HpGe) detector. Measurements were corrected for gamma-ray attenuations, dead time and fluctuation of neutron flux. Data for ^natRu(n,x)^99mTc reaction cross sections are reported to be 9.6±1.5 and 9.2±1.1 mb at 13.5±0.2 and 14.8±0.2 MeV incident neutron energies, respectively. Results were compared with the data by other anthors.     

Determination of carbon in thin layers by means of the12C(d,n)13N nuclear reaction using a 2 MeV Van de Graaf accelerator

A nondestructive method for carbon determination in layers of 3–10 m thickness is considered. The method is based on using the¹²C(d, n)¹³N nuclear reaction with simultaneous account of surface contamination by means of the¹²C(d, p)¹³C competitive reaction. The total cross sections for the¹²C(d, n)¹³N reaction were measured from 0.4 to 1.7 MeV. Proton beam annealing was applied with the purpose of lowering surface carbon content. The detection limit of carbon by this method is 0.5 ppm, relative standard deviation is 0.06. Disturbing effects of carbon diffusion and¹³N recoil backs cattering are also taken into account.     

Activation cross sections for the element rhenium

The¹⁸⁵Re(n,)¹⁸²Ta,¹⁸⁷Re(n,)¹⁸⁴Ta,¹⁸⁷Re(n,p)¹⁸⁷W and¹⁸⁷Re(n,2n)^186gRe reaction cross sections included by 13.5–14.7 MeV neutrons were measured by the activition method. The neutron fluences were determined by the cross section of the²⁷Al(n,)²⁴Na reaction. The neutron energies in these measurements were determined by the cross section ratios for⁹⁰Zr(n,2n)^89m+gZr and⁹³Nb(n,2n)^92mNb reactions.     

Average cross-sections for (n, α) and (n,p) reactions on titanium in a fission-type reactor spectrum

The average cross-section in a fission-type reactor spectrum was determined experimentally for the reactions:⁴⁶Ti(n,p)⁴⁶Sc,⁴⁷Ti(n,p)⁴⁷Sc,⁴⁸Ti(n,p)⁴⁸Ti(n,α)⁴⁵Ca and⁵⁰Ti(n,α)⁴⁷Ca. In order to obtain the (n,p) cross-sections, reactor irradiation of titanium was followed by measurement of the induced scandium activities with a Ge(Li) detector of calibrated detection efficiency. For this no chemical separations had to be carried out. For the (n,α) reactions, however, the induced calcium activities were separeted and purified by oxalate precipitation, after the bulk of the radioactivity had been removed by precipitation of titanium hydroxide. The⁴⁷Ca disintegration rate was determined in the same way as for the scandium isotopes, whereas for⁴⁵Ca liquid scintillation counting was carried out. The shape of the reactor spectrum was investigated by irradiating reference threshold detectors with different effective threshold energies. To correct for (n,γ) interferences, irradiations were carried out with and without cadmium shielding. On the basis of \(\bar \sigma _F = 0.64\) mb for the reaction²⁷Al(n,α)²⁴Na, the average cross-sections were as follows:⁴⁶Ti(n,p)⁴⁶Sc:10.5±0.4 mb;⁴⁷Ti(n,p)⁴⁷Sc: 16.3±0.6 mb;⁴⁸Ti(n,p)⁴⁸Sc:0.272±0.005 mb;⁴⁸Ti(n,α)⁴⁵Ca: 34μb;⁵⁰Ti(n,α)⁴⁷Ca: 8.1±0.3 μb.     

Analysis of long-lived isotopes by liquid scintillation spectrometry

Neutron production cross sections are reported for reactions leading to long-lived isotopes in fusion reactor materials. Pure elements and separated isotopes were irradiated with 14.6–14.8 MeV neutron fluences up to 10¹⁸ n/cm². Undesired activities were chemically separated and the long-lived activities were measured using both liquid scintillation and x-ray spectrometry. Results are presented for the reactions⁵⁶Fe(n,2n)⁵⁵Fe(2.73 y),⁶⁴Ni(n,2n)⁶³Ni(100 y),⁶³Cu(n,p)⁶³Ni, and⁶⁰Ni(n,2n)⁵⁹Ni(76,000 y).Work supported by the U.S. Department of Energy.