Energy Nuclear Reactions Research Articles

Effects of burial powder configuration on the microstructure, composition, and ion conductivity of perovskite Li3xLa1/3‐xTaO3 ion conductors

AbstractA combustion synthesis methodology for the preparation of perovskite Li3xLa1/3‐xTaO3 lithium‐ion conductors with x = 0.033 is presented. Bulk ceramic specimens were sintered under combinations of burial powder and cover crucibles to provide different lithium vapor overpressure conditions. A maximum total lithium ion conductivity of 6 × 10‐6 S cm‐1 at room temperature was found for the pellet covered by a crucible whose lip was sealed using parent powder (moderate overpressure), with agreement to the maximum in the intergranular ion conductivity. Intragranular conductivity was maximized at the low overpressure condition. The trend in ion conductivity was found to correspond to the lithium content in the samples through a combination nuclear reaction analysis and energy dispersive X‐ray spectroscopy phase constitution measurements. The mechanism impacting ion conductivity was determined to be changes in the amount of LaTaO4 secondary phase as driven by the processing conditions during sintering.

Modification of the fusion energy gain factor in magnetic confinement fusion due to plasma temperature anisotropy

In magnetic confinement fusion (MCF), the plasma always exhibits an anisotropic temperature distribution, which may impact not only the plasma dynamics but also the nuclear reaction process. Here, through theoretical derivations and self-consistent particle-in-cell simulations with the newly-developed nuclear reaction and alpha particle energy deposition calculation modules, we find that, if considering the plasma has an anisotropic temperature distribution, the fusion energy gain factor (Q) of MCF is significantly modified, where both the deuteron–triton nuclear reactivity and the alpha particle energy deposition fraction are heavily influenced. The simulation results show that, under the International Thermonuclear Experimental Reactor (ITER) condition, if the plasma temperature anisotropy ratio can reach 0.1, i.e., the plasma perpendicular temperature component is one-tenth of its parallel component corresponding to the ambient magnetic field direction, the Q-value of ITER can be increased from the originally-designed 5 to about 10, with doubled enhancement.

WITHDRAWN: Design and Implementation of Human-Computer Interaction Adjustment in Nuclear Power Monitoring System

Abstract As a new energy source, nuclear energy is a hot topic in the world energy research. Due to its large nuclear reaction energy and serious potential harm, its reaction monitoring system has become an important research topic. This thesis has passed five investigation experiments, including the parameter data comparing the nuclear power reaction related to manual detection and human-computer interaction detection; comparing the differences between the human-computer interaction system and the artificial system that detect the temperature data during the day; and using the human-computer interaction system. The feasibility experiment of human-machine interaction adjustment design in artificial sensor-nuclear power monitoring system for the rise and fall of labor costs before and after detection. The experimental data show that the human-machine interaction detection scheme in the nuclear power monitoring system can be consistent with the manual detection data, and at the same time, the system can be used to ensure its accuracy at all times; and it can significantly reduce the labor cost and use the funds for scientific research. Improvement, at the same time, this scheme is also feasible. The experimental data show that the design of the human-computer interaction detection scheme in the nuclear power monitoring system is conducive to the systematic management of the micro data of the nuclear power reaction, while achieving macro-control, and reducing the labor cost by 80% and increasing the calculation speed value by 70% .The above will also provide a solid technical foundation for the future development of nuclear power.

Development of neutron activation system on EAST.

A neutron activation system (NAS) has been developed on the Experimental Advanced Superconducting Tokamak (EAST) for the investigation of time-integrated neutron yield. It is a robust neutron diagnostic with high precision and a wide dynamic range. Some high purity materials with a proper nuclear reaction energy threshold and cross section are tested as neutron detectors in the NAS, and they are delivered to the tokamak device by a pneumatic transfer system. The length of the pneumatic pipeline is about 50 m, and the transfer time ranges from 10 s to 20 s. The decay gamma rays of the activated samples are measured with a high-purity germanium spectrometer, and its detection efficiencies are 6.9% at 336 keV and 1.7% at 1779 keV, respectively. Indium and silicon samples with a reaction threshold of 0.3 MeV and 4.0 MeV, respectively, were successfully implemented in the diagnosis of DD and DT neutron yield in the EAST. The neutron flux of the NAS was compared with the count of the fission chamber in the EAST neutral beam injection experiment, and the DD neutron yield evaluated by the NAS ranges from 1.9 × 1012 n/shot to 5.9 × 1014 n/shot during recent experimental campaign.

Interpolation of nuclear reaction energy distributions

ABSTRACTThis paper discusses several methods of interpolation of data for tables of energy distributions for particles emitted by nuclear reactions. The methods are also applicable to angular distributions. Our primary interest is in interpolation with respect to the energy of the incident particle. We first examine four interpolation methods currently used in the nuclear data community: direct interpolation, unit-base interpolation, interpolation by averages on equiprobable bins, and interpolation by corresponding energies. Because each of these methods has shortcomings, a modified version of interpolation by corresponding energies is proposed here. We call this new method interpolation by cumulative points.

Study of processes of nuclear reaction energy conversion into energy of optical radiation

This paper presents the preliminary results of the reactor experiments to study the spectral-luminescent properties of gaseous mixtures (based on He, Ne and Kr noble gases). The investigated gaseous mixtures were excited by the products of 6Li(n,α)3H nuclear reaction. The IVG.1M research reactor acted as a source of thermal neutrons. The description of experimental facility and experimental ampoule device for reactor irradiation is presented. The highest intensity of radiation was observed in experiments with He-Ne gaseous mixture on lines with a wavelength of 585.2 nm, 640.4 nm and 703.4 nm. He-Ne mixture’s main energy in the range of 500 nm to 800 nm was radiated on atomic transitions 3p-3s of neon. The most intensive transitions in neon were 3p’[1/2]0 - 3s’[1/2]10 with λ = 585 nm and 3p[1/2]1 - 3s’[1/2]20 and 3s[3/2]10 with λ = 703.4 nm and 724 nm.

Quantitative Analysis of Plutonium Content in Particles Collected from a Certified Reference Material by Total Nuclear Reaction Energy (Q Value) Spectroscopy

Microcalorimeters with embedded radioisotopes are an emerging category of sensor with advantages over existing methods for isotopic analysis of trace-level nuclear materials. For each nuclear decay, the energy of all decay products captured by the absorber (alpha particles, gamma rays, X-rays, electrons, daughter nuclei, etc.) is measured in one pulse. For alpha-decaying isotopes, this gives a measurement of the total nuclear reaction energy (Q value) and the spectra consist of well-separated, narrow peaks. We have demonstrated a simple mechanical alloying process to create an absorber structure consisting of a gold matrix with small inclusions of a radioactive sample. This absorber structure provides an optimized energy thermalization environment, resulting in high-resolution spectra with minimal tailing. We have applied this process to the analysis of particles collected from the surface of a plutonium metal certified reference material (CRM-126A from New Brunswick Laboratory) and demonstrated isotopic analysis by microcalorimeter Q value spectroscopy. Energy resolution from the Gaussian component of a Bortels function fit was 1.3 keV FWHM at 5244 keV. The collected particles were integrated directly into the detector absorber without any chemical processing. The \(^{238}\)Pu/\(^{239}\)Pu and \(^{240}\)Pu/\(^{239}\)Pu mass ratios were measured and the results confirmed against the certificate of analysis for the reference material. We also demonstrated inter-element analysis capability by measuring the \(^{241}\)Am/\(^{239}\)Pu mass ratio.

Sensor and Method Development for Analysis of Alpha- and Beta-Decaying Radioisotopes Embedded InsideMicrocalorimeter Detectors

We discuss sensor and method development for the analysis of alphaand beta-decaying radioisotopes encapsulated within superconducting transition-edge sensor microcalorimeter absorbers. For alpha-decaying isotopes, e.g., 238 Pu, 241 Am, and 210 Po, this is a measurement of the total nuclear reaction energy (Q) and the spectra consist of sharp, narrow peaks. The primary peak is at the Q value, with secondary peaks corresponding to gamma-ray-escape peaks. In contrast, for beta-decaying isotopes, e.g., 241 Pu, the spectrum is a low energy continuum ending at E=Q. We are developing transition edge-sensor (TES) microcalorimeters to measure these spectra simultaneously in a single sample, hence allowing quantitative analysis of all Pu isotopes from 238 to 242. We have developed and used TES microcalorimeter detectors for this purpose, and it represents a new quantitative analysis tool for nuclear forensics and safeguards. Due to the high efficiency of the embedded source geometry, measurement times can be minimized. The high dynamic range of our sensors creates the opportunity to measure the relatively low energy beta-decay spectrum of 241 Pu (Q = 20.78 keV) simultaneously with the Q ~ 5-6 MeV of alpha-decaying actinides. Finally, the technique could also be effective for determining the time since chemical purification of Pu using the 241 Pu/ 241 Am isotopic ratio via simultaneous measurement of the low-energy 241 Pu beta particles and the high-energy 241 Am Q-value.

Integration of Radioactive Material with Microcalorimeter Detectors

Microcalorimeter detectors with embedded radioactive material offer many possibilities for new types of measurements and applications. We will discuss the designs and methods that we are developing for precise deposition of radioactive material and its encapsulation in the absorber of transition-edge sensor (TES) microcalorimeter detectors for two specific applications. The first application is total nuclear reaction energy (Q) spectroscopy for nuclear forensics measurements of trace actinide samples, where the goal is determination of ratios of isotopes with Q values in the range of 5–7 MeV. Simplified, rapid sample preparation and detector assembly is necessary for practical measurements, while maintaining good energy resolution. The second application is electron capture spectroscopy of isotopes with low Q values, such as \(^{163}\)Ho, for measurement of neutrino mass. Detectors for electron capture spectroscopy are designed for measuring energies up to approximately 6 keV. Their smaller heat capacity and physical size present unique challenges. Both applications require precise deposition of radioactive material and encapsulation in an absorber with optimized thermal properties and coupling to the TES. We have made detectors for both applications with a variety of designs and assembly methods, and will present their development.

The atomic mass evaluation - present and future

The atomic mass evaluation (AME) is a reliable resource for the values related to the atomic masses. Since the publication of the latest version of AME in 2003, a large amount of new data emerged from mass measurements performed by Penning traps and storage rings, as well as from nuclear decay and reaction energy measurements. A new project called "AME-future" is currently ongoing and it is aimed at creation of new mass tables that will be published in 2013: AME2013. The present status of AME and its working structure are presented. With the newly included data, the mass surface for nuclei far from the valley of stability seems to lie higher than was anticipated earlier. The impact on astrophysical applications is discussed. Some examples describing correlations between masses are presented.

Far-ultraviolet signatures of the H3e(n,tp) reaction in noble gas mixtures

Previous work showed that the H3e(n,tp) reaction in a cell of H3e at atmospheric pressure generated tens of far-ultraviolet photons per reacted neutron. Here we report amplification of that signal by factors of 1000 and more when noble gases are added to the cell. Calibrated filter-detector measurements show that this large signal is due to noble gas excimer emissions and that the nuclear reaction energy is converted to far-ultraviolet radiation with efficiencies of up to 30%. The results have been placed on an absolute scale through calibrations at the NIST SURF III synchrotron. They suggest possibilities for high-efficiency neutron detectors as an alternative to existing proportional counters.

Application of the SIMNRA code to calibrate the analyzing magnet associated with a Van de Graaff accelerator

This work reports on a fast method of calibrating the analyzer magnet associated with a Van de Graaff accelerator based on the SIMNRA simulation of the backscattered elastic proton spectra produced by the proton bombardment of thick silicon. Several proton spectra were measured with proton beam energies in the 1.6 –2.3MeV energy region where two resonances in 28Si(p, p)28Si elastic scattering occur at 1.645 and 2.087MeV. Also the 12C(d,p)13C nuclear reaction was applied to calibrate the analyzing magnet. A thick carbon target was bombarded with several deuteron beam energies in the 1.4MeV range. The nuclear reaction proton spectra were also simulated using the SIMNRA code. However, in this case, it was not necessary to choose the deuterium beam energies near a nuclear reaction energy resonance. The comparison of the analyzer magnet calibration with this procedure is in good agreement with the calibration using the 27Al(p,γ)28Si method.

Energy behavior of neutrons around axi-symmetric sealed-off neutron generating tubes

The aim of this paper is to contribute to analytical characterization of the spatial dependency of the mean energy of fast neutrons produced in non-dispersive media by sealed-off neutron generating tubes (NGT) having axial symmetry. Neutrons are generated in most of NGT by accelerating a mixture of hydrogen isotope ions (deuterons and tritons) onto plane self-targets. Deuterons and tritons are implanted in the mentioned targets and become target nuclei for the subsequent incoming ions. d- T, t- D and d- D fast neutrons are generated. Analytical expressions for the neutron mean energy in these three cases are deduced, taking into account the exothermic character of the reactions. Due consideration is paid to collision kinetics, depending upon mass and kinetic energy of particles involved in the nuclear reaction, nuclear reaction energy, etc.

Plane rectangular tritium target response to excitation by uniform distributed normal accelerated deuteron beam

This work is a contribution to analytical study of the spatial dependency of the d- T mean neutron energy in the vicinity of a homogeneous tritium-occluded rectangular plane target. An accelerated deuteron beam excites the tritium target with normal incidence to the target plane. The transverse density of accelerated deuteron beam is assumed to be constant close to the target. Due consideration being paid to d- T collision kinetics, depending upon mass and kinetic energy of particles involved in the nuclear collision, nuclear reaction energy, etc, in particular circumstances, the elementary neutron energy emission in non-dispersive media can be considered to be omni-directional or very low anisotropical. Consequently, analytical expressions can be considerably simplified, taking into account the exothermic character of d- T fusion reaction. A number of expressions for energetic prediction of the fast neutron generated, in this case, by d- T reaction are proposed. Animated three-dimensional-graphics is suggested. Computationally tractable tools are of importance in the study of some situations such as induced reactions and activation analysis using 14 MeV neutrons, investigations in health-physics, radiation dose characterization, nuclear medicine, damage effects, and simulation studies.

Atomic weights of the elements. Review 2000 (IUPAC Technical Report)

A consistent set of internationally accepted atomic weights has long been an essential aim of the scientific community because of the relevance of these values to science and technology, as well as to trade and commerce subject to ethical, legal, and international standards. The standard atomic weights of the elements are regularly evaluated, recommended, and published in updated tables by the Commission on Atomic Weights and Isotopic Abundances (CAWIA) of the International Union of Pure and Applied Chemistry (IUPAC). These values are invariably associated with carefully evaluated uncertainties. Atomic weights were originally determined by mass ratio measurements coupled with an understanding of chemical stoichiometry, but are now based almost exclusively on knowledge of the isotopic composition (derived from isotope-abundance ratio measurements) and the atomic masses of the isotopes of the elements. Atomic weights and atomic masses are now scaled to a numerical value of exactly 12 for the mass of the carbon isotope of mass number 12. Technological advances in mass spectrometry and nuclear-reaction energies have enabled atomic masses to be determined with a relative uncertainty of better than 1 ×10−7 . Isotope abundances for an increasing number of elements can be measured to better than 1 ×10−3 . The excellent precision of such measurements led to the discovery that many elements, in different specimens, display significant variations in their isotope-abundance ratios, caused by a variety of natural and industrial physicochemical processes. While such variations increasingly place a constraint on the uncertainties with which some standard atomic weights can be stated, they provide numerous opportunities for investigating a range of important phenomena in physical, chemical, cosmological, biological, and industrial processes. This review reflects the current and increasing interest of science in the measured differences between source-specific and even sample-specific atomic weights. These relative comparisons can often be made with a smaller uncertainty than is achieved in the best calibrated “absolute ” (=SI-traceable) atomic-weight determinations. Accurate determinations of the atomic weights of certain elements also influence the values of fundamental constants such as the Avogadro, Faraday, and universal gas constants. This review is in two parts: the first summarizes the development of the science of atomic-weight determinations during the 20th century; the second summarizes the changes and variations that have been recognized in the values and uncertainties of atomic weights, on an element-by-element basis, in the latter part of the 20th century.

Transition metal nitrides thin films deposition using a dynamically controlled magnetron sputtering apparatus

Transition metal nitrides thin films are normally used as coatings to protect mechanical tools, e.g., bits and drills, to provide biocompatibility for common materials like steel and as decorative layers. Among these nitrides, TiN is the most usual coating deposited as a single film or multilayered with other materials deposited preferentially by magnetron sputtering. The film properties such as adhesion, intrinsic stress and hardness can be controlled and improved by means of a bias potential applied to the substrates. The problem of stoichiometry oscillation during the deposition process was resolved using the dynamic partial pressure control to maintain the argon to nitrogen ratio and the working pressure constant by means of a computer controlled interface. In this work the argon to nitrogen ratio was changed in order to obtain one stoichiometric nitride for the transition metals of group IV and group V. Film characterization was performed using Rutherford backscattering, nuclear reaction analysis and energy dispersive spectroscopy for elemental composition and stoichiometry; X-ray diffraction to study the crystal phase formation and scanning electron microscopy to determine the thin film thickness and microstructure. The corrosion protection ability and microhardness of the samples are also presented in view of the applicability potential of the coatings. The results shows that formation mechanisms of the studied nitrides are similar showing an optimal argon to nitrogen pressure ratio to obtain the stoichiometric phase.

Characterization and Tribological Properties of Nanostructured Copper/Carbon Composite Films Prepared by Microwave Plasma-Assisted Dual Deposition Processes

ABSTRACTNanocrystalline copper/hydrogenated amorphous carbon films have been deposited on Si substrates at the floating potential using a distributed electron cyclotron resonance microwave plasma reactor. In this deposition technique, the microwave plasma-enhanced chemical vapor deposition process of carbon from argon-methane or argon-acetylene mixtures of various compositions was associated with the sputter deposition of copper from a copper target. The total pressure was fixed at 0.13 Pa. For deposition, the substrates mounted on a water-cooled substrate holder were maintained at ambient temperature. The composition of films determined by Rutherford backscattering spectroscopy, energy recoil detection analyses and nuclear reaction analyses was investigated as a function of the gas phase composition. The structure of films was identified by X-ray diffraction (XRD) techniques and the size of copper crystallites incorporated in the amorphous carbon matrix was deduced from XRD data. The magnitude of residual stresses developed in these films was calculated from the radius of curvature of film/substrate samples determined by profilometry. The residual stress values were found to be nearly independent on the composition of films and deposition parameters.

Nuclear reaction rates and energy in stellar plasmas: The effect of highly damped modes

The effects of the highly damped modes in the energy and reaction rates in a plasma are discussed. These modes, with wave numbers k≫kD, even being only weakly excited, with less than kBT per mode, make a significant contribution to the energy and screening in a plasma. When the de Broglie wavelength is much less than the distance of closest approach of thermal electrons, a classical analysis of the plasma can be made. It is assumed, in the classical analysis, with ℏ→0, that the energy of the fluctuations ℏω≪kBT. Using the fluctuation-dissipation theorem, the spectra of fluctuations with ℏ≠0 is appreciably decreased. The decrease is mainly for the highly damped modes at high frequencies (∼0.5–3kBT). Reaction rates are enhanced in a plasma due to the screening of the reacting ions. This is taken into account by the Salpeter factor, which assumes slow motion for the ions. The implication of including the highly damped modes (with ℏ≠0) in the nuclear reaction rates in a plasma is discussed. Finally, the investigations presently done on these effects in particle simulations with the sheet model and the multiparticle quantum simulation code are described.

Energy behaviour of neutrons generated by Witch-type distributed axi-symmetrical deuteron beams accelerated onto plane tritium targets

This paper is an analytical study of the spatial dependency of the d– T neutron energy in the vicinity of a homogeneous tritium-occluded plane target. Close to the target, and along the path of incidence of axially symmetric deuteron beams, the transverse density of accelerated deuterons is assumed to be governed by a law approximated by the ‘Witch’ function. In particular circumstances, the elementary neutron emission process in non-dispersive media can be considered to be omni-directional (due consideration being paid to collision kinetics, depending upon mass and kinetic energy of particles involved in the nuclear collision, nuclear reaction energy, etc.). Consequently, analytical expressions can be considerably simplified. By applying the classical kinetic energy and momentum conservation laws to nuclear processes, a theoretical description is obtained, taking into account the exoergic character of d– T fusion reaction. A number of expressions for energetic prediction of the fast neutron field are proposed. The associated relations, involving elementary functions, can be investigated using a desk-top computer. Computationally tractable tools are of importance in the study of diverse situations such as induced reactions and activation analysis using 14 MeV neutron generators, investigations in health-physics, radiation dose measurements, nuclear medicine, damage effects, and simulation studies.

Ge:Si:O evaporated alloys as a thermosensitive layer for large area bolometers

A study of the composition and properties of amorphous Ge:Si:O thin films deposited at low temperature by reactive coevaporation is presented. Films with various compositions are obtained by separately controlling the evaporation rates of germanium and silicon. The composition of films is measured by combining Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA) and energy dispersive X-ray analysis (EDX) techniques. Films are characterized by FTIR absorption spectroscopy, VIS-NIR transmittance and temperature behaviour of the electrical resistivity. The analysis of all experimental data shows that oxygen incorporation depends on the silicon content in the films. Oxygen atoms appear mainly bonded to silicon and not to germanium. An uniformed distribution rather than a cluster structure of silicon oxide into a germanium matrix is suggested. Both optical band gap energy and thermal coefficient of the resistivity vary with composition of films. Preliminary studies of thin films with similar composition obtained using reactive sputtering from a composite target evince the coexistence of SiO and GeO bonds.