Thermal Neutron Cross Section Research Articles

Measurements of thermal neutron cross section and resonance integrals of74Se,75As,94Zr,134Cs,238U

The thermal neutron cross sections and resonance integrals of74Se,75As,94Zr,134Cs,238U have been measured. Neutron activation was performed by using the ICIS-flux position of the CONSORT-II Reactor. A high resolution γ-ray detector system was used to measure the reaction rates of the irradiated samples. Results of analysis are presented and compared with literature values.

Measurements of Thermal Neutron Cross Section and Resonance Integral for237Np(n, γ)238Np Reaction

Making use of a standard neutron spectrum field with a pure Maxwellian distribution, the thermal neutron cross section for the 237Np(n, γ)238Np reaction was measured at a neutron energy of 0.0253 eV by the activation method. The result is 158±3 b, which is obtained relative to the reference value of 98.65±0.09 b for the 197Au(n, γ)198Au reaction. Although the data in JENDL-3 is larger by about 15% than the present value, the recently revised data in JENDL-3.2 is close to the present. The ENDF/B-V, ENDF/B-VI, JEF-2 and Mughabghab's data are also larger by 7–15%. Old measurements are larger by 7–18% than the present data. The resonance integral for the 237Np(n, γ)238Np reaction was also measured relative to the reference value of 1,550±28 b for the 197Au(n, γ)198Au reaction with a 1/E standard neutron spectrum field. By defining the Cd cut-off energy as 0.5 eV for the 237Np(n, γ)238Np reaction, the present resonance integral is 652 ± 24 b, which is in good agreement with the JENDL-3, -3.2, ENDF/B-V, -VI, JEF-2 and Mughabghab's data. However, most of the old experimental data are, in general, larger by 24–38% than the present measurement.

Static critical properties of disordered ferromagnets studied by superconducting quantum interference device magnetometry and small-angle neutron-scattering techniques

CdCr(2−2x)In(2x)S4 is a highly frustrated magnetic system based on CdCr2S4, a well-known Heisenberg 3D ferromagnet. A study is presented of its static critical properties as a function of concentration, performed by low-field superconducting quantum interference device SQUID magnetometry and small-angle neutron-scattering SANS techniques. Samples were prepared from isotopic cadmium 114Cd with a low absorption cross section for thermal neutrons. Magnetic measurements performed with low dc fields in the temperature range 5–300 K allow one to determine the magnetic state of the samples, the reentrant temperature TG, the Curie temperature TC, and the critical exponent γ of the susceptibility above TC as a function of dilution in the domain 0<x<0.15. By directly measuring the critical magnetic fluctuations in zero field in SANS experiments, access is gained to the magnetic correlation length ξ, its exponent ν above TC, and another independent determination of γ. Whereas the pure compound exhibits exponents (γ=1.37, ν=0.70) compatible with a 3D Heisenberg ferromagnetic model, a pronounced increase of measured exponents with dilution was found, namely γ=1.97, ν=1.03. The results are compared to the ones of similar studies in the related system Eu(1−x)Sr(x)S and to the renormalization group treatment of strongly random ferromagnets, and possible mechanisms to explain how a small dilution can provoke large alterations in the critical behavior and move the system in the strong disorder region are discussed.

Microstructural studies on cast Zr3Al-3wt%Nb

In the binary Zr-Al system, Zr[sub 3]Al is the intermetallic phase richest in zirconium. In view of its low absorption cross section for thermal neutrons and its good strength and corrosion resistance, Zr[sub 3]Al may have possible applications as a structural material in thermal reactors. This phase has the ordered cubic L1[sub 2] structure and forms through the peritectoid reaction: [beta]-Zr + Zr[sub 2]Al[minus] > Zr[sub 3]Al, the reaction temperature being 1,292 K. Structurally Zr[sub 3]Al is quite similar to the [alpha][sub 2] or the Ti[sub 3]Al phase (ordered hexagonal DO[sub 19] structure) in the Ti-Al system, the two structures differing only in the stacking sequence of the close packed atomic layers. But for its inherent brittleness, Ti[sub 3]Al is a promising structural material for aerospace applications. It has, however, been demonstrated that niobium additions can reduce the brittleness of this phase. Studies on the Ti[sub 3]Al-Nb system have also shown that niobium stabilizes the high temperature [beta] phase (bcc structure) which, on cooling, can decompose through various phase reactions, generating some interesting microstructures. Similar studies on the Zr[sub 3]Al-Nb system have not been reported yet. The present paper describes some microstructural observations made on a cast Zr[sub 3]Al-3wt%Nb alloy.

Measurement of the Thermal Neutron Cross Section of the90Sr(n, γ)91Sr Reaction

Measurement of the Thermal Neutron Cross Section of the⁹⁰Sr(<i>n, γ</i>)⁹¹Sr Reaction

HAFNIUM

Abstract HAFNIUM is a commercially available refractory metal which has outstanding corrosion resistance, good mechanical properties, and is readily amenable to standard fabrication techniques. These characteristics, coupled with its high thermal-neutron cross section, high-temperature allotropic transformation, and excellent electrical properties, have made it of increasing interest to design engineers in a variety of fields. This datasheet provides information on composition, physical properties, microstructure, elasticity, and tensile properties. It also includes information on corrosion resistance as well as machining and joining. Filing Code: HF-1. Producer or source: Teledyne Wah Chang Albany.

CARPENTER NEUTROSORB and NEUTROSORB PLUS

Abstract Carpenter NeutroSorb and NeutroSorb PLUS are austenitic stainless steels modified with boron to increase the thermal neutron cross-section. These alloys are used for handling and storing radioactive material such as spent fuel. This datasheet provides information on composition, physical properties, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, machining, and joining. Filing Code: SS-563. Producer or source: Carpenter.

Measurements of Thermal Neutron Cross Section and Resonance Integral for 237Np(n,.GAMMA.)238Np Reaction.

Making use of a standard neutron spectrum field with a pure Maxwellian distribution, the thermal neutron cross section for the 237Np(n, γ)238Np reaction was measured at a neutron energy of 0.0253 eV by the activation method. The result is 158±3 b, which is obtained relative to the reference value of 98.65±0.09 b for the 197Au(n, γ)198Au reaction. Although the data in JENDL-3 is larger by about 15% than the present value, the recently revised data in JENDL-3.2 is close to the present. The ENDF/B-V, ENDF/B-VI, JEF-2 and Mughabghab's data are also larger by 7–15%. Old measurements are larger by 7–18% than the present data. The resonance integral for the 237Np(n, γ)238Np reaction was also measured relative to the reference value of 1,550±28 b for the 197Au(n, γ)198Au reaction with a 1/E standard neutron spectrum field. By defining the Cd cut-off energy as 0.5 eV for the 237Np(n, γ)238Np reaction, the present resonance integral is 652 ± 24 b, which is in good agreement with the JENDL-3, -3.2, ENDF/B-V, -VI, JEF-2 and Mughabghab's data. However, most of the old experimental data are, in general, larger by 24–38% than the present measurement.

Measurement of the Thermal Neutron Cross Section of the 90Sr(n,.GAMMA.)91Sr Reaction.

To obtain fundamental data for the research of the transmutation of nuclear waste, the thermal neutron cross section of the reaction 90Sr(n, γ)91Sr has been measured by means of a radiochemical method. Strontium chloride targets containing about 2 MBq of 90Sr were irradiated for 10 min with reactor neutrons. Activation detectors of Co/Al and Au/Al alloy wires were irradiated simultaneously to monitor the neutron flux and Westcott's epithermal index r (T/T 0)1/2. The irradiated Sr samples were purified chemically and their r-ray spectra were measured with a high purity Ge detector. Since the targets included 85Sr, a γ-ray emitter and a tracer for 90Sr, and a ratio of the amount of 85Sr to that of 90Sr was measured in advance, an effective cross section of the 90Sr(n, γ)91Sr reaction for a reactor neutron spectrum was determined from the ratio of radioactivities of 91Sr and 85Sr, and neutron flux data. The resonance integral was also measured by a modified Cd-ratio measurement. Considering an upper limit of...

Measurement of Thermal Neutron Cross Section and Resonance Integral of the Reaction137Cs(n, γ)138Cs

Abstract To obtain fundamental data for the research of the transmutation of nuclear waste, the thermal neutron cross section and the resonance integral of the reaction 137Cs(n, γ)138Cs have been measured by means of a modified Cd-ratio technique. Targets of about 0.4 MBq 137Cs were irradiated with neutrons in the JRR-4 swimming pool reactor by using a pneumatic tube equipped with a movable Cd shield, and neutron fluxes and their epithermal neutron fractions were monitored with activation detectors (Co/Al and Au/Al) whose sensitivity to epithermal neutrons differed from each other. After irradiation, the 137Cs samples were purified chemically and their γ-ray spectra were measured with a high purity Ge detector. The resulting yields of 138Cs for different neutron spectra and the neutron flux data have yielded that the thermal neutron cross section (for 2,200 m/s neutrons) is 0.25±0.02b and the resonance integral 0.36±0.07b. The results are consistent with the effective cross section (σ=0.250±0.013b) of our...

Measurements of the thermal neutron cross section of 90Sr(n,γ) 91Sr reaction

The thermal neutron cross section of the 90Sr(n,γ) 91Sr reaction was measured in a D 2O moderated reactor with an activation technique. The Cd ratio of the neutron flux at the location of the irradiation is about 30. For reduction of the 90Y high energy beta-ray background strontium-specific columns (Sr. Spec(TM)) were used to chemically separate the Y from Sr before irradiation and again after irradiation prior to commencement of counting the 91Sr activity. The amount of 90Sr in a counting sample was determined from the beta activity of 90Y with an end-window beta-ray proportional counter. This system was calibrated with a known 90Sr standard sample. The neutron flux at the irradiation position in the D 2O moderated reactor was determined from a Co/Al alloy monitor irradiated simultaneously with a 90Sr sample. The 91Sr activity was measured with a high resolution Ge spectrometer. The sensitivity to beta induced bremstrahlung was reduced by the use of lucite, cadmium, copper, and lead absorbers around the sample and the Ge detector. The overall efficiency of the spectrometer was determined with a set of calibrated 137Cs, 134Cs, 133Ba, 88Y, 60Co and 54Mn sources. These measurements yielded a value of (9.7 ± 0.7 mb) for the D 2O moderated neutron cross section of 90Sr(n,γ) 91Sr.

Measurement of Thermal Neutron Cross Section and Resonance Integral of the Reaction 137Cs(n,.GAMMA.) 138Cs.

Measurement of Thermal Neutron Cross Section and Resonance Integral of the Reaction 137Cs(n,.GAMMA.) 138Cs.

Creep of niobium and solid solution strengthened Nb-1wt.%Zr

The search for new materials for advanced aerospace structural applications at elevated temperatures has renewed an interest in niobium and its alloys due to its high melting point (2741 K), low thermal neutron cross section, good corrosion resistance against liquid lithium, and low density (8. 58 gm/cc) compared to other refractory metals. However, the diffusivity of bcc niobium is high and, as a result, the creep strength of niobium is inherently weak. Solid solution strengthening is one approach to improve the creep strength of metallic materials. Solid solution strengthening of class M (pure metal type) materials changes the creep response and rate controlling deformation mechanism. Class M materials show a normal transient during the primary stage in a semilogarithmic plot of [dot [Epsilon]] versus [Epsilon] and the rate controlling mechanism is dislocation climb. Class A (alloy type) materials show an inverse transient during the primary stage in a [dot [Epsilon]] versus [Epsilon] semilogarithmic plot, and the rate controlling mechanism is viscous glide. The objective of this paper is to study and compare the creep behavior of niobium and Nb-1wt. %Zr.

Thermal neutron cross sections and diffusion parameters of diphenyl and Dowtherm-A using a synthetic scattering function

We have used a synthetic scattering function to evaluate thermal neutron cross sections and diffusion parameters for diphenyl and Dowtherm-A, over a range of temperatures of practical interest. The present formalism is based on our benzene model, which has been already validated in a previous application. Our calculated results for diphenyl are in excellent agreement with several measured quantities, whereas those for Dowtherm-A are at variance with the scarce available information.

Measurement of macroscopic and microscopic thermal neutron cross sections of V, Co, Cu, In, Dy and Au using neutron self-absorption properties

In this study, the total thermal neutron macroscopic and microscopic cross sections of V, Co, Cu, In, Dy and Au were measured using neutron self-absorption properties. Pure foils of these elements with various thicknesses were irradiated using a 5 Ci238Pu−Be source. After the irradiation, the gamma-spectra of their radionuclides were recorded by an HpGe detector. The gamma-photopeak areas of interest were determined by evaluating the gamma-spectra obtained from the foils. They were plotted as a function of foil thickness for each element. Then a non-linear least-squares fitting method was applied to the functions, and the total thermal neutron macroscopic and microscopic cross sections of V, Co, Cu, In, Dy and Au were obtained.

Nucleon capture by 3He and the production of solar hep-neutrinos: Cross-section measurements and shell-model calculations

An experimental and theoretical investigation on low-energy nucleon capture by 3He is reported. The extremely small cross section of the 3He(n, γ) reaction has been measured with thermal and with 24.5 keV neutrons, yielding gs n γ(th) = 55 ± 3 μb and σ n γ(24.5 keV) = 9.1 ± 0.8 μb, respectively. Shell-model calculations that include the contributions of two-body meson-exchange currents are presented for the radiative capture of thermal neutrons by 3He as well as for the weak 3He(p, e + ν e) reaction. With the ratio of the corresponding magnetic dipole and Gamow-Teller matrix elements, and the experimental radiative thermal neutron cross section, a value S = (5.7 ± 0.8) × 10 −19 ke V · b is obtained for the astrophysical S- factor of the neutrino-emitting reaction. This indicates that roughly 10% of the measured solar-neutrino flux in the Davis' experiment can be ascribed to the high-energy 3He + p neutrinos.

The Luminescence and EPR Characterisation of Neutron Transmutation Doped Gallium Phosphide

Nuclear Transmutation Doping (NTD) enables doping of semiconductor crystals, independent of their growth conditions [1]. In this method the dopand is generated in the crystal volume as a result of thermal neutron irradiation. Owing to the low capture cross-section of thermal neutrons by host lattice atoms, the distribution of transmutation-induced dopants is homogeneous and nearly independent of the diameter and size of the semiconductor crystals. In this paper we present the results of photoluminescence (PL) and EPR measurements on thermal neutron irradiated and annealed GaP. When GaP is irradiated with thermal neutrons, both of its elements are transmuted and the isotopeS 70 Ge and 32 S are formed [2]. The cross-section (σ th) for the formation of the Ge isotopes is much larger than for the S isotope creation. Therefore, during the neutron irradiation process, mainly Ge dopants are generated. The transmuted Ge and S nuclei experience the recoil due to the subsequent β and γ emissions. Thus, the position of Ge or S atoms in the unit cell is not necessarily a substitutional

Measurement of the 36Ar(n, p) 36Cl cross section at thermal energies using the AMS technique

The 36Cl production mechanism in the atmosphere is of interest in understanding the formation of this cosmogenic radioisotope and its applications in geological studies. The 36Ar(n, p) 36Cl reaction has been suggested by Onufriev as a source of 36Cl in the atmosphere. Onufriev derived this estmation by assuming the 36Ar(n, p) 36Cl reaction to be caused by slow neutrons with a cross section of the same order of magnitude as that of the 14N(n, p) 14C reaction [1]. However, no data existed for the slow neutron cross section of 36Ar(n, p) 36Cl. We irradiated enriched 36Ar gas in a reactor and used the AMS technique to detect 36Cl. We obtained an upper limit for the thermal neutron cross section of 1.5 mb. This value is three orders of magnitude lower than the value assumed by Onufriev.

Radiative neutron capture on 3He.

The thermal neutron cross section for the reaction n${+}^{3}$He${\ensuremath{\rightarrow}}^{4}$He+\ensuremath{\gamma} is calculated with the Monte Carlo method from realistic variational wave functions obtained for the Argonne ${\mathit{v}}_{14}$ two-nucleon and Urbana VII three-nucleon interaction models. The calculated cross section is found to be almost entirely due to exchange currents. With the exchange current operator constructed so as to satisfy the continuity equation with the Argonne ${\mathit{v}}_{14}$ interaction, the calculated cross section is 71 \ensuremath{\mu}b, which is close to the empirical value 54\ifmmode\pm\else\textpm\fi{}6 \ensuremath{\mu}b. The less certainly known contributions from model-dependent exchange current mechanisms increase the predicted value to about 112 \ensuremath{\mu}b. The calculated cross section depends strongly on the n${+}^{3}$He scattering length, varying between 140 and 71 \ensuremath{\mu}b as the scattering length is changed from 3.25 to 3.75 fm.

Measurement of Thermal Neutron Cross Section of137Cs(n, γ)138Cs Reaction

Click to increase image sizeClick to decrease image sizeKEYWORDS: nuclear transmutationcesium 137cesium 138half-lifeGe-detectorsneutron captureradioactive wasteschemical separationgamma spectracross sectionsthermal energy