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The paper presents the results of the study of the processes of self-propagating high-temperature synthesis of Zr-1%B alloy and its refining by electron beam melting. Experiments on the influence of boron's amorphous and crystalline modifications on the safety parameters of the synthesis process of Zr-1%B alloy necessitated the conversion of amorphous boron into crystalline form by electron beam melting, with an increase in its purity from 94% to 99.9%. High efficiency of vacuum induction and electron beam equipment was demonstrated, which provided a high purity of the Zr-1%B alloy of at least 99.9%. The alloy ingots had a uniform distribution of the alloying element (boron) all over the volume. The obtained alloy is suitable for the production of materials with thermal neutron capture cross-sections of up to 40 barns for neutron protection. [ABSTRACT FROM AUTHOR]

In reality, after subtracting the beam background from the prompt γ -ray spectrum induced by the irradiated sample with the same time measurement, it still exists the remaining γ -ray background induced by the nuclei capturing the thermal neutrons scattered by the sample. This makes it difficult to validate the accuracy of the PGNAA detector response between the simulation and the experiment in the wide energy range. In this study, a simple method to construct the remaining γ -ray background in the simulation prompt γ -ray spectrum of 35 Cl(n, γ ) 36 Cl reaction is proposed. Then the simulation prompt γ -ray spectrum with the remaining γ -ray background is compared to the experimental spectrum to validate the simulation PGNAA detector response in the energy range from 0.1 MeV to about 9 MeV. [ABSTRACT FROM AUTHOR]

Tungsten@boron nitride (W@BN) core–shell nanoparticles have been synthesized using an in situ arc discharge method by conjointly leading tungsten atoms and borazine precursors to the arc core. Metal atoms and BN radicals self-assemble to form core–shell nanoparticles, where hexagonal boron nitride (h-BN) wraps around the surface of the core tungsten nanoparticles, originating from their metallic and covalent bonding nature. The core–shell structure was analyzed by various methods, such as HR-TEM, EDS, XRD, and XPS. The coating of h-BN on the W nanoparticles improved the oxidation resistance of the W nanoparticles, as evidenced by the oxidation temperature shift in thermogravimetric analysis. The fabricated 20 wt % W@BN/BP epoxy composite exhibited thermal neutron shielding with an absorption coefficient of 0.351 mm–1 as well as γ ray shielding with an attenuation coefficient of 0.357 cm–1. These core–shell particles can effectively shield the secondary γ rays emitted during the thermal neutron capture process of 10B as well as the primary γ rays. This study will lead to the utilization of W@BN core–shell nanoparticles in space or extreme environments, where radiation shielding is critical for human activity. [ABSTRACT FROM AUTHOR]

The incorporation of high thermal neutron capture elements in ceramic materials is relevant for the design of traceable proppants for obtaining information in petrology, such as the location and height of fractures in unconventional gas and oil wells. Among these, GdAlO 3 has attracted interest because of its good thermo-mechanical properties. In this work, four Al 2 O 3 /GdAlO 3 reaction sintered composites were prepared using Gd 2 O 3 and Al 2 O 3 powders as raw materials and high-energy ball milling followed by sintering at 1600 °C. This combination of ball milling and reaction sintering is considered as a mechanism to produce large bulk ceramics with different Al 2 O 3 /GdAlO 3 compositions. The composite formulations range from pure alumina to eutectic ceramic. The obtained materials were characterized using X-ray diffraction for identifying the crystalline phases, Archimedes method for the textural properties, scanning electron microscopy for the microstructure, and Vickers indenter and three-point bending tests for the mechanical properties. In addition, the macroscopic capture cross-section Σ for thermal neutrons was estimated considering each composite formulation. It was found that the processing route is very suitable for producing low-porosity Al 2 O 3 /GdAlO 3 composites, which present similar mechanical properties to those of alumina. Both the material density and Σ increase with increasing the starting amount of Gd 2 O 3 , in a way that for the eutectic composite the density is 50% higher than that of pure alumina, and Σ is about 550000 c.u. The effect of the material porosity on Σ was also considered. The obtained results indicate that the proposed processing route is very attractive for producing these ceramic composites for technological applications. [ABSTRACT FROM AUTHOR]

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Neutron data and cross-sections are highly regarded and are essential for developing nuclear equipment such as advanced fission and fusion reactors, accelerators, neutron shielding, physics studies, etc. The neutron cross-section should preferably be measured using a single-energy neutron beam, although the presence of a background in research reactors can affect its accurate determination. The Neutron Powder Diffraction (NPD) facility of Tehran Research Reactor (TRR) has been taken into consideration for measuring the neutron cross-section based on its properties, including neutron monochromator and multiple collimators. In this work, radiative capture cross-sections of Au, In, and Rh materials have been calculated using TRR monochromatic beam. MCNPX is a Monte Carlo particle transport code that has been applied to simulate the measurement system of the neutron cross-section and calculate the reaction rates. The effect of the presence and absence of different sections of the background on the cross-section values was investigated and the results were compared with EXFOR data library for validation. According to the findings, neutron backgrounds can have varying impacts depending on factors such as sample material, the isotope resonance regions, neutron source spatial distribution, and neutron monochromatic energy. However, the presence of fast neutron background contributes to the most uncertainty in the cross section values while its removal produces an average discrepancy from experimental libraries of 7.16%. Also, removing the cold neutron background also causes a relative difference equal to 7.65%. [ABSTRACT FROM AUTHOR]

The radiochemical effects of thermal neutron capture in tris(2,2,6,6-tetramethyl-3,5-heptandionato)chromium(III) (Cr(tmhd)3) were investigated. A method was devised to quantify the amount of the induced 51Cr activity recoverable in the original chemical form and to confirm that it is indeed Cr(tmhd)3. The method is based on a combination of chemical separation (column chromatography and recrystallization) and analytical (radio-TLC, HPLC, and gamma spectrometry) techniques. Cr(tmhd)3 samples were irradiated and purified in two steps after irradiation. We found that two of the (three) purification pathways yielded good agreement among final 51Cr activity concentrations. The corresponding samples appeared to be of exceptional radiochemical purity. [ABSTRACT FROM AUTHOR]

Purpose: A multi‐scale investigation of the biological properties of gadolinium neutron capture (GdNC) therapy with applications in particle therapy is conducted using the TOPAS Monte Carlo (MC) simulation code. The simulation results are used to quantify the amount of gadolinium dose enhancement produced as a result of the secondary neutron production from proton therapy scaled by measured data. Materials and methods: MC modeling was performed using the radiobiology extension TOol for PArticle Simulation TOPAS‐nBio MC simulation code to study the radiobiological effects produced from GdNC on a segment of DNA, a spherical cellular model, and from the modeling of previous experimental measurements. The average RBE values were calculated from two methods, microdosimetric kinematic (MK) and biological weighting r(y) within a 2 nm DNA segment for GdNC. The single‐strand breaks (SSBs) and double‐strand breaks (DSBs) were calculated from within the nucleus of a 20 µm diameter, spherical cell model. From a previous experimental proton therapy measurement using a spread‐out Bragg peak (SOBP) of 4.5–9.5 cm and a delivered absorbed dose of 10.4 Gy, the amount of Gd neutron captures was calculated and used to quantify the amount of GdNC absolute dose from particle therapy. Results: The average RBE from microdosimetric kinematic and biological weighting was 1.35, and 1.70 for a 10% cell survival on HSG cell‐line and weighting function data from early intestinal tolerance of mice. From a central isotropic GdNC source, the energy deposition is found to decrease from roughly 2.7 eV per capture down to approximately 0.01 eV per capture, a drop of two orders of magnitude within 50 nm. This result suggests that Gd needs to be close to the DNA (within 10–20 nm) in order for neutron capture to induce a significant dose enhancement due to the short‐range electrons emitted after Gd neutron capture. Within a spherical cell model, the SSBs, and DSBs were determined to be 39 and 1.5 per neutron capture, respectively. From the total neutron captures produced from an experimental proton therapy measurement on a 3000 PPM Gd solution, an insignificant absolute Gd dose enhancement was quantified to be 5.4 × 10−6 Gy per Gy of administered proton dose. Conclusion: From this study and literature review, the production of secondary thermal neutrons from proton therapy is determined to be a limiting factor and unlikely to produce a clinically useful dose enhancement for secondary neutron capture therapy. Moreover, alternative neutron sources, such as, a compact deuterium‐tritium (D‐T) neutron generator, a "high yield" deuterium‐deuterium (D‐D) generator, or an industrial strength (100 mg) 252Cf source were investigated, with the 252Cf source the most likely to be capable of producing enough neutrons for 1 Gy of localized GdNC absolute dose within a reasonable treatment time. [ABSTRACT FROM AUTHOR]

In this study, the gamma-ray spectrum of single elemental capture spectrum log was simulated. By numerical simulation we obtain a single-element neutron capture gamma spectrum. The neutron and photon transportable processes were simulated using the Monte Carlo N-Particle Transport Code System (MCNP), where an Am-Be neutron source generated the neutrons and thermal neutron capture reactions with the stratigraphic elements. The characteristic gamma rays and the standard gamma spectra were recorded, from analyzing of the characteristic spectra analysis we obtain the ten elements in the stratum, such as Si, Ca, Fe, S, Ti, Al, K, Na, Cl, and Ba. Comparing with single elemental capture gamma spectrum of Schlumberger, the simulated characteristic peak and the spectral change results are in good agreement with Schlumberger. The characteristic peak positions observed also consistent with the data obtained from the National Nuclear Data Center of the International Atomic Energy Agency. The neutron gamma spectrum results calculated using this simple method have practical applications. They also serve as an reference for data processing using other types of element logging tools. [ABSTRACT FROM AUTHOR]

Neutron capture and transmission measurements were carried out from 0.01 to 600 eV on both solid and liquid samples containing elemental cesium (133Cs). Only s-wave resonances were observed in these measurements. These data were analyzed for resonance parameters utilizing the SAMMY Bayesian analysis code to simultaneously fit both the capture and transmission data. Parameters were obtained for 31 cesium resonances up to 600 eV. The thermal capture cross section and capture resonance integral were determined. The thermal capture cross section is 10% larger than the ENDF, JENDL, and JEFF evaluated values but lies within the uncertainty of the most recent measurement by Yoon and Lee [New Phys.: Sae Mulli (Korean Phys. Soc.)., Vol. 61, p. 7 (2011)]. The capture resonance integral has a statistical 1σ error of 2% and lies 1.4σ above the JENDL value, 5.5σ above the ENDF value, and 3.9σ above the JEFF value. The s-wave strength function was determined. [ABSTRACT FROM AUTHOR]

Abstract Surrogate radiation sources are used to test detection equipment and train security personnel in the detection and interdiction of special nuclear material (SNM). Some current surrogate sources do not accurately match SNM energy spectra, including for HEU. In this research, we propose and investigate novel source configurations for higher fidelity surrogate SNM sources using thermal neutron capture reactions that result in prompt gammas. The objective is to create a surrogate source that has a more representative spectrum, low cost, and requires minimal security, special handling, and safety precautions. [ABSTRACT FROM AUTHOR]

The reaction 171Yb(nth,2γ) was studied with the aim of extending the experimental database of intensities of cascades of two photons emitted sequentially after radiative thermal-neutron capture. An analysis of these cascade intensities permitted revealing the change in the structure of observed levels of the 172Yb nucleus versus the excitation energy and determining probable thresholds for the break of four Cooper pairs of neutrons below the neutron binding energy. [ABSTRACT FROM AUTHOR]

The NEutron induced POsitron source MUniCh (NEPOMUC) at the research reactor FRM II of the technical university Munich provides a monoenergetic low-energy positron beam with the world highest intensity of 109 moderated positrons per second. The principle of NEPOMUC is based on the emission of high-energy prompt γ-rays after thermal neutron capture in 113Cd. Subsequent pair production and positron moderation in platinum foils lead to the emission of monoenergetic positrons. The primary beam is extracted with a kinetic energy of 1 keV and passes a remoderation unit for brightness enhancement before it is magnetically guided to the instruments. The experiments range from fundamental studies in nuclear, atomic and plasma physics over high-sensitive and elemental selective investigations in surface and solid state physics to applications in materials science. [ABSTRACT FROM AUTHOR]

Recently, several scientific applications of gadolinium are found in neutrino physics experiments. Gadolinium-157 is the nucleus, which has the largest thermal neutron capture cross-section among all stable nuclei. Gadolinium-155 also has the large cross-section. These neutron capture reactions provide the gamma-ray cascade with the total energy of about 8 MeV. This reaction is applied for several neutrino experiments, e.g. reactor neutrino experiments and Gd doped large water Cherenkov detector experiments, to recognize inverse-beta-decay reaction. A good Gd(n,γ) simulation model is needed to evaluate the detection efficiency of the neutron capture reaction, i.e. the efficiency of IBD detection. In this presentation, we will report the development and study status of a Gd(n,γ) calculation model and comparison with our experimental data taken at ANNRI/MLF beam line, J-PARC. [ABSTRACT FROM AUTHOR]

The thermal neutron capture cross section (σ0) and resonance integral cross section (I0) of the 139La(n,γ)140La reaction have been measured relative to that of the 197Au(n,γ)198Au reaction by means of the activation method. High-purity natural lanthanum and gold foils were exposed to pulsed neutrons at the Pohang neutron facility. One set of foils was irradiated directly and a second set of foils was shielded with a cadmium cover of 0.5 mm thickness. The induced activities in the activated foils were measured by a γ-ray spectrometer based on a calibrated high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the epithermal neutron spectrum shape factor (α) was determined, and the corrections for the thermal neutron self-shielding (Gth), the resonance neutron self-shielding (Gepi), the γ-ray attenuation (Fg) and the γ-ray coincidence summing effects were made. The thermal neutron cross-section for the 139La(n,γ)140La reaction has been determined to be 9.16 ± 0.36 barn, relative to the reference value of 98.65 ± 0.09 barn for the 197Au(n,γ)198Au reaction. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral cross section for the 139La(n,γ)140La reaction is 11.64 ± 0.69 barn, which is determined relative to the reference value of 1550 ± 28 barn for the 197Au(n,γ)198Au reaction. The measured results are compared with literature values and discussed. [ABSTRACT FROM AUTHOR]

Cadmium is a highly volatile element and its abundance in meteorites may help better understand volatility-controlled processes in the solar nebula and on meteorite parent bodies. The large thermal neutron capture cross section of 113Cd suggests that Cd isotopes might be well suited to quantify neutron fluences in extraterrestrial materials. The aims of this study were (1) to evaluate the range and magnitude of Cd concentrations in magmatic iron meteorites, and (2) to assess the potential of Cd isotopes as a neutron dosimeter for iron meteorites. Our new Cd concentration data determined by isotope dilution demonstrate that Cd concentrations in iron meteorites are significantly lower than in some previous studies. In contrast to large systematic variations in the concentration of moderately volatile elements like Ga and Ge, there is neither systematic variation in Cd concentration amongst troilites, nor amongst metal phases of different iron meteorite groups. Instead, Cd is strongly depleted in all iron meteorite groups, implying that the parent bodies accreted well above the condensation temperature of Cd (i.e., ≈650 K) and thus incorporated only minimal amounts of highly volatile elements. No Cd isotope anomalies were found, whereas Pt and W isotope anomalies for the same iron meteorite samples indicate a significant fluence of epithermal and higher energetic neutrons. This observation demonstrates that owing to the high Fe concentrations in iron meteorites, neutron capture mainly occurs at epithermal and higher energies. The combined Cd-Pt-W isotope results from this study thus demonstrate that the relative magnitude of neutron capture-induced isotope anomalies is strongly affected by the chemical composition of the irradiated material. The resulting low fluence of thermal neutrons in iron meteorites and their very low Cd concentrations make Cd isotopes unsuitable as a neutron dosimeter for iron meteorites. [ABSTRACT FROM AUTHOR]

Several samples of Np and Pu were irradiated in the guided cold neutron beam of the prompt gamma activation analysis facility at the Budapest Research Reactor. The thermal neutron capture cross sections of Np and Pu were evaluated from the obtained prompt and delayed gamma ray data. The thermal neutron capture cross sections for Np( n,γ)Np was found to be $$ \sigma_{0} ({}^{237}{\text{Np}}) = 170.4 \pm 7.4\,{\text{b}} $$ and for Pu(n,γ)Pu to be $$ \sigma_{0} ({}^{242}{\text{Pu}}) = 19.6 \pm 3.9\,{\text{b}} $$. [ABSTRACT FROM AUTHOR]

Neutron capture effects in meteorites and lunar surface samples have been successfully used in the past to study exposure histories and shielding conditions. In recent years, however, it turned out that neutron capture effects produce a nuisance for some of the short-lived radionuclide systems. The most prominent example is the 182Hf-182W system in iron meteorites, for which neutron capture effects lower the 182W/184W ratio, thereby producing too old apparent ages. Here, we present a thorough study of neutron capture effects in iron meteorites, ordinary chondrites, and carbonaceous chondrites, whereas the focus is on iron meteorites. We study in detail the effects responsible for neutron production, neutron transport, and neutron slowing down and find that neutron capture in all studied meteorite types is not, as usually expected, exclusively via thermal neutrons. In contrast, most of the neutron capture in iron meteorites is in the epithermal energy range and there is a significant contribution from epithermal neutron capture even in stony meteorites. Using sophisticated particle spectra and evaluated cross section data files for neutron capture reactions we calculate the neutron capture effects for Sm, Gd, Cd, Pd, Pt, and Os isotopes, which all can serve as neutron-dose proxies, either in stony or in iron meteorites. In addition, we model neutron capture effects in W and Ag isotopes. For W isotopes, the GCR-induced shifts perfectly correlate with Os and Pt isotope shifts, which therefore can be used as neutron-dose proxies and permit a reliable correction. We also found that GCR-induced effects for the 107Pd-107Ag system can be significant and need to be corrected, a result that is in contrast to earlier studies. [ABSTRACT FROM AUTHOR]

Abstract: Some emission probabilities of relatively intense or less contaminant prompt γ rays of 24Na, 28Al, 52V, 56Mn, 60Co, 142Pr, 187W and 198Au with thermal-neutron capture reactions were determined by successive measurement of γ rays following the β decay of produced radioisotopes, namely β-delayed γ rays. Prompt and β-delayed γ rays were measured with the same HPGe detector the efficiency of which is well determined for a wide energy range, from 0.1 to 11MeV. The previously proposed values for 24Na, 28Al, 60Co and 198Au except for low energy, were generally in agreement with the present results, while those for 52V, 56Mn, 142Pr and 187W were not. The reasons for the disagreement are discussed in terms of the detection efficiencies of the detectors, the used nuclear data and the normalization procedure for determining prompt γ-ray intensities. The effectiveness of this method at checking the intensities of prompt γ rays is demonstrated. [Copyright &y& Elsevier]

Abstract: A formula is given which, for neutron energies in the range 10−4 < E <10eV, permits calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of magnesium oxide (MgO) temperature and crystal parameters. Computer program has been developed to calculate the total neutron cross-section and transmission through mono-crystalline MgO. The calculated neutron transmission and effective attenuation coefficient values for MgO-single crystal at different temperatures are compared with measured ones. An overall agreement is indicated between the formula fits and experimental data. A feasibility study for the use of MgO-single crystal is discussed in terms of the optimum MgO-single crystal thickness, mosaic spread, temperature and cutting plane for efficient transmission of thermal-reactor neutrons, and also for rejection of the accompanying fast neutrons and gamma rays. Calculation shows that 10cm thick MgO-single crystal cut along its (100) plane, with 0.5° FWHM on mosaic spread and cooled at 77K, is a good thermal neutron filter, with high effect-to-noise ratio. [Copyright &y& Elsevier]