Neutron Threshold Reactions Research Articles

An overview of activation cross-section measurements of some neutron and charged-particle induced reactions in Bangladesh

Abstract Over the last several decades, our research group has been working on nuclear data measurements using a J-25 Neutron Generator, a TRIGA Mark II Research Reactor and a Tandem Accelerator at Savar, as well as an Am/Be neutron source at Rajshahi. The spectrum of fast neutrons having energies from 0.5 to 20 MeV in the core of the TRIGA reactor as well as from 1.5 to 11 MeV of the Am/Be source was well characterized for validation of evaluated data of neutron threshold reactions. Spectrum-averaged cross sections were determined by integral measurements. The integral values measured at both the reactor and the Am/Be source were compared with the integrated data deduced from measured and evaluated excitation functions of some nuclear reactions given in some data libraries. As example, the details on the integral and integrated cross sections of the 64Zn(n,p)64Cu and 60Ni(n,p)60Co reactions are discussed. In both cases, integral test shows that further improvement of the evaluated excitation function reported in data libraries is needed. The use of a newly developed facility at the 3 MV Tandem Accelerator in measurement of proton induced reaction cross sections in the energy region below 5 MeV is outlined, and new results on the 64Ni(p,n)64Cu and natNi(p,x)61Cu processes below 3 MeV are discussed.

Activation Measurements of Cross Sections for Ground and Isomeric States Production in Neutron Threshold Reactions on Y and Au

The paper describes cross-section measurements consisting of neutron activation using a 7Li(p,n) quasi mono-energetic neutron source and gamma-ray spectrometry performed at the Nuclear Physics Institute of the Czech Academy of Sciences in Řež, Czech Republic. The analysis of the excitation functions of neutron-induced threshold reactions for the energy range from 17 up to 34 MeV is presented. The cross sections for the population of both ground and isomeric states were measured in yttrium and gold. A comprehensive comparison of the measured cross sections with earlier experimental data from the EXFOR database, TALYS calculations, and evaluated nuclear data libraries is presented.

Studies of neutron cross-sections important for spallation experiments using the activation method

A series of experiments devoted to studies of neutron cross-sections by activation method was carried out. The cross-sections of various threshold reactions were studied by means of different quasi-monoenergetic neutron sources with energies from 14 MeV up to 100 MeV. Threshold reactions in various materials are among other used to measure fast neutron fields produced during accelerator driven system studies. For this reason our measurements of neutron cross-sections are crucial. At present, neither experimental nor evaluated data above 30 MeV are available for neutron threshold reactions in Au, I and In published in this proceedings. We studied materials in the form of thin foils and compared our data with the calculations preformed using the deterministic code TALYS 1.4.

Fast neutron spectrum unfolding of a TRIGA Mark II reactor and measurement of spectrum-averaged cross sections: integral tests of differential cross sections of neutron threshold reactions

Summary The spectrum of fast neutrons having energies from 0.5 to 20 MeV in the core of the 3MW TRIGA Mark II reactor at Savar, Dhaka, Bangladesh, was unfolded by activating several metal foils to induce threshold nuclear reactions covering the whole spectrum, and then doing necessary iterative calculations utilizing the activation results and the code SULSA. The analysed shape of the spectrum in the TRIGA core was found to be similar to that of the pure 235U-fission spectrum, except for the energies between 0.5 and 1.5 MeV, where it was slightly higher than the fission spectrum. Spectrum-averaged cross sections were determined by integral measurements. The integral values measured in this work were compared with the recommended values for a pure fission spectrum as well as with the integrated data deduced from measured and evaluated excitation functions of a few reactions given in some data files. The good agreement between integral measurements and integrated data in case of well-investigated reactions shows that the fast neutron field at the TRIGA Mark II reactor can be used for validation of evaluated data of neutron threshold reactions.

Cross section measurements of a few threshold reactions induced by fast neutrons from an Am/Be source: integral tests of differential neutron reaction cross section data

Abstract Integral cross sections of the reactions 24Mg(n,p)24Na, 27Al(n,p)27Mg, 27Al(n,α)24Na and 95Mo(n,p)95Nb were measured for the first time with fast neutrons (E n > 1.5 MeV) from an Am/Be source. Furthermore, upper cross section limits for the reactions 98Mo(n,α)95Zr and 103Rh(n,p)103Ru were deduced. The results were compared with data calculated using the neutron spectral distribution and the excitation function of each reaction given in the data files and libraries ENDF/B-VII, JEFF-3.1.2, JENDL-4.0, IRDF-2004, TENDL-2010, ROSFOND-2010 and CENDL-3.1. In general, the integral measurement and the integrated value agreed within ± 10%. The fast neutron field (with E n > 1.5 MeV) of the Am/Be source is thus well suited for integral tests of excitation functions of neutron threshold reactions.

Cross-section measurements of neutron threshold reactions in various materials

Abstract As members of international collaboration “Energy and Transmutation of radioactive Waste” we routinely use (n,xn) threshold reactions in various materials to measure high energy neutron flux from spallation reactions. The cross–sections of many reactions important for our activation detectors are missing. To improve situation, we studied the neutron cross-sections using different quasi-monoenergetic neutron sources based on proton reaction on 7Li target. The measurements were performed in Nuclear Physics Institute of the Academy of Sciences of the Czech Republic in Řež near Prague and in The Svedberg Laboratory in Uppsala (Sweden). We used neutron energies 17, 22, 30 and 35 MeV from the quasi-monoenergetic neutron source in Řež and neutron energies 22, 47 and 94 MeV in Uppsala. The last experiment was carried out in February 2010 in Uppsala using neutron energies 59, 66, 72 and 89 MeV. The study of neutron threshold reactions in yttrium was performed first time during this irradiation. We have developed procedure for the subtraction of contribution of the background neutrons. We studied various materials in the form of thin foils and observed good agreement with the data in EXFOR database and also with the calculations performed in deterministic code TALYS. Many cross-sections were measured in the energy regions where no experimental data are available so far.

Fission spectrum averaged cross section measurements of some neutron threshold reactions of relevance to medical radionuclide production

Summary A resume is given of radiochemical measurements of nuclear reaction cross sections relevant to the production of some medically important radionuclides carried out at PINSTECH during the last decade. Systematic studies on fission neutron spectrum averaged cross sections of several threshold reactions, like (n, 2n), (n, p) and (n, α), on titanium, ruthenium, europium and dysprosium for the production of 45Ti, 96Tc, 153Sm and 153Gd are described.

Excitation Functions of some Neutron Threshold Reactions on 89Y in the Energy Range of 7.8 to 14.7 MeV

Excitation Functions of some Neutron Threshold Reactions on ⁸⁹Y in the Energy Range of 7.8 to 14.7 MeV

Triton burnup measurements by neutron activation at JT-60U

This paper describes measurements on triton burnup in a deuterium plasma by the detection of the 2.5 MeV neutrons (from DD fusion) and the 14 MeV neutrons (from DT fusion). The 2.5 MeV neutrons have been measured by fission chambers and activation of indium foils while the 14 MeV neutrons have been detected by activation of silicon, aluminum, and copper foils. The measured yields of the 2.5 MeV neutrons utilizing In foils are ∼20–40% higher than the yields obtained from fission chambers depending on what calibration factors are used. The deviation decreases with the plasma major radius (or increasing plasma volume). When the triton burnup is measured by utilizing neutron threshold reactions ( E n>2.5 MeV) and In foils, then systematic errors in the calibration factors cancel and the maximum deviation between the measured triton burnup for different calibration factors is reduced to ∼5%. The measurements indicate that triton burnup increases with the 14 MeV neutron yield, indicating that the relative yield of 14 MeV neutrons increases depending on the time duration of the deuterium neutral beam injection (NBI). Furthermore, the triton burnup decreases with an increased plasma major radius, indicating increased triton ripple losses, and increases with plasma current, indicating reduced banana orbit losses.

Excitation Functions of Neutron Threshold Reactions on Some Isotopes of Germanium, Arsenic, and Selenium in the 6.3- to 14.7-MeV Energy Range

Cross sections were measured for the 75As(n,p)75Ge, 75As(n, α)72Ga, 75As(n,2n)74As, 74,76,78Se(n,p)74,76,78As, 78,80Se(n,α)75,77Ge, 72,73,74Ge(n,p)72,73,74Ga, and 70,76Ge(n,2n)69,75Ge reactions ove...

Activation Cross Sections of Neutron Threshold Reactions on Some Zirconium Isotopes in the 5.4- to 10.6-MeV Energy Range

Cross sections have been measured in the 5.4- to 10.6-MeV energy range for the {sup 90}Zr(n,p){sup 90m}Y, {sup 91}Zr(n,p){sup 91m}Y, {sup 92}Zr(n,p){sup 92}Y, {sup 90}Zr(n,{alpha}){sup 87m}Sr, {sup 94}Zr(n,{alpha}){sup 91}Sr, and {sup 96}Zr(n,2n){sup 95}Zr reactions. The quasi-monoenergetic neutrons were produced via the {sup 2}H(d,n){sup 3}He reaction using a deuterium gas target at a variable energy compact cyclotron. Use was made of the activation technique in combination with high-resolution gamma-ray spectroscopy. Some trends in the excitation functions are discussed.

Excitation functions of some neutron threshold reactions on isotopes of molybdenum

Cross sections were measured for (n,p) reactions on 92, 95, 96, 97, 98mo, (n, α) reactions on 92, 98Mo, and (n, 2n) reaction on 100Mo for the first time in the neutron energy range of 5.9 to 9.6 MeV. The quasi-monoenergetic neutrons were produced via the 2H(d, n) 3He reaction using a deuterium gas target at a compact cyclotron. Use was made of the activation technique in combination with high-resolution γ-ray spectroscopy. Some systematic trends observed in the excitation functions are discussed. For the various isotopes of molybdenum, with increasing mass of the target nucleus, the thresholds of (n,p) and (n,α) reactions increase and the magnitudes of cross sections near the maxima of the excitation functions appear to decrease. Hauser-Feshbach calculations show that in general the excitation functions of (n, p) and (n, α) reactions are described within a factor of 2 by the statistical model only up to about 8 MeV; the (n,2n) reaction on 100Mo, however, is reproduced well from threshold up to 15 MeV by this model.

Appendix E: Cross Section Data for Some Neutron Threshold Reactions

Appendix E: Cross Section Data for Some Neutron Threshold Reactions

Appendix E: Cross Section Data for Some Neutron Threshold Reactions

Appendix E: Cross Section Data for Some Neutron Threshold Reactions