Measurement of Thermal Neutron Cross Section of 137Cs(n, γ)138Cs Reaction

A calculational model for a modified diffusion coefficient has been developed to incorporate the neutron streaming effect in heterogeneous low-density channels accurately into diffusion theory calculations. The model uses a supercell, and the axial and radial diffusion coefficients of the heterogeneous inner cell are so defined that they can reproduce Benoist's axial and radial diffusion coefficients of the supercell when the diffusion coefficient of the outer cell is given as 1/3 Σ_tr . In the case of the axial diffusion coefficient, the axial buckling effect is taken into account by modifying the neutron path length within the streaming channel in calculating the collision probabilities. This model has been applied to an RZ fast reactor Core model with a gas expansion module (GEM). By using the axial diffusion coefficient obtained with the presented model, calculational error of GEM worth was reduced to less than 1/7 compared to the formula of Rowlands and Eaton.     

Irradiation of Escherichia Coli in Reactor Core

¹⁰B(n, α)⁷Li is a promising reaction for radiation therapy which can be selectively used for tumor cell killing sparing surrounding normal tissue. (Boron Neutron Capture Therapy: BNCT)

Despite the apparent success in application, basic studies to evaluate the biological effects of the reaction are in sparsity in terms of relative biological effectiveness (RBE) measurements and of adverse effects of the reaction such as mutagenesis. While the efficiency of the reaction is largely dependent on the selectiveness or localization of ¹⁰B compounds in tumor tissues, the lethal and mutagenic (or carcinogenic) effect of the reaction on normal cells must be carefully evaluated.

Towards this end developed here is a new experimental approach using as a model system Escherichia Coli cells which allows us to examine specific effects of the boron- neutron capture reaction in terms of lethality and mutagenecity as an example.

Isotropic irradiation of biological system in the core of a small research reactor is thought tobe an advantage for this experiment in that it simulates actual medical irradiations though it requires data analysis for individual radiation effects.     

Dieaway Measurements of Fast Neutrons in an Iron Assembly using Californium-252

The fast transient behavior of the fast neutron population in an iron assembly immediately following the burst was measured by changing the energy response of the neutron detector with use made of ²⁵²Cf as a randomly pulsed source.

Comparison between experiment and calculation proved that this type of transient experiment would be useful for evaluating the method of calculation adopted in solving space-time-dependent problems.     

Benchmark Experiment on Vanadium with D-T Neutrons and Validation of Evaluated Nuclear Data Libraries by Analysis of the Experiment

A neutronics benchmark experiment on vanadium, which is a low activation fusion reactor material, was conducted by using the D-T neutron source facility of FNS/JAERI. Neutron spectra, dosimetry reaction rates, γ-ray spectra and γ-ray heating rates were measured in a vanadium experimental assembly. Benchmark tests for four evaluated nuclear data files were performed by analyzing the experiment. As a result, the following problems were pointed out in view of accuracy of fusion reactor designs. (1) JENDL-FF and JENDL-3.2: Total cross section should be reexamined especially at ～2keV. (2) ENDF/B-VI: Double differential cross sections for 14 MeV neutrons should be revised because of the isotropic angular distribution for continuum neutron emission. Gamma-ray production cross sections are too small and discrete γ-ray peaks are not represented clearly. (3) EFF-3: Gamma-ray production cross sections are too large.     

New Efficient Albedo Monte Carlo Method for Neutron Streaming Analyses

An efficient albedo Monte Carlo method newly developed has been studied by analyzing two types of experiments on neutron streaming. The method is characterized by employing the energy-angle dependent doubly differential albedos for slab, which can be calculated in a short computer time with a one-dimensional transport theory, such as the Sn method and more efficient invariant imbedding method. This paper describes the features of the present albedo Monte Carlo method, including fundamental formulas. In the analyses of the neutron streaming experiments, the calculated results agreed with the measured data within a factor of 2 for a benchmark experiment at the YAYOI reactor and within a factor of 3 for an SNR sodium duct mock-up experiment.

It is concluded that the present albedo Monte Carlo method is practical and applicable to the reactor shielding analysis concerning radiation streaming.     

The Extraction of Curium and Americium by Tri-n-Octyl Phosphine Oxide

Magnesium chromate anhydrate, magnesium chromate monohydrate and sodium chromate quadrahydrate were irradiated in the Liquid Nitrogen Temperature Loop at the Japan Atomic Energy Research Institute to study the behavior of ⁵¹Cr recoil atoms. The initial retentions of recoil ⁵¹Cr were measured at ?55°, ?40° and ?30°C, and the thermal annealing behavior of recoil ⁵¹Cr was examined extensively in the temperature range from ?20° to 80 °C. The effects of difference in total irradiation dose and of the water of crystallization on the annealing behaviors of ⁵¹Cr recoil atoms are discussed.     

Study of creep cavitation in stainless steel weldment

Abstract

A study of creep cavities near reheat cracking in AISI Type 316H austenitic stainless steel headers, removed from prolonged high temperature operation in nuclear power plants, is reported. It is shown how application of scanning electron microscopy (SEM), cryogenic fractography and small angle neutron scattering (SANS) can be applied, in a complementary way, to observe and quantify creep cavitation. Creep cavities in the vicinity of the crack are found to be mainly surrounding inter-granular carbides. Trends in the size and area fraction of creep cavities relative to the crack path are quantified using optimised metallography. The SANS technique is found to be a very suitable method of quantifying creep cavitation within the size range up to 600 nm averaged over a larger gauge volume. It is shown that the cavity size distribution peaks in the region 100–300 nm, and this correlates closely with the quantitative SEM observations.     

带有锥状反射结构的AlGaInP键合衬底LED

本研究通过光辅助化学腐蚀技术在衬底键合AlGaInP反极性发光二极管中制备出锥状反射镜结构提升器件的光提取效率。首先利用氢氟酸与双氧水在532nm激光的辐射下载GaP:Mg层制备出锥状腐蚀结构,然后将金属反射镜蒸镀在锥状结构之上制备锥状的反射镜结构。在完成全部芯片工艺后,测试结果表明锥状反射镜结构可以显著提升光提取效率,并在光通量测量中与表面粗化集成平板反射镜LED相比较,得到了18.55%的增强。     

Interfacial activity and micellar morphology of an imidazolium ring containing zwitterionic surfactants

Zwitterionic surfactants based on 3-(1-alkyl-3-imidazolio) propane-sulfonate ([ImS3-R] where R is octyl or dodecyl) is an emerging and important class of amphiphile due to their relevance as nano reactors for the synthesis of metallic nanoparticles and accelerated acid hydrolysis. The physicochemical properties of such synthesized imidazolium ring-containing zwitterionic surfactants have been characterized by surface tension and small-angle neutron scattering (SANS) techniques. Surface tension measurements were used to calculate several thermodynamic parameters over a range of concentrations and temperatures (298–313 K). The results obtained showed a weak signature representing the critical micelle concentration (CMC) for ImS3-8, however, by increasing the alkyl length of the hydrophobic group to dodecyl, that is, ImS3-8 to ImS3-12, the signature of the CMC was much more evident. As expected, the CMC for ImS3-12 shifted to a lower concentration. An increase in temperature increased the surface activity and decreased the CMC of both zwitterionic surfactants, although the changes were small. Compared to classical surfactants, that is, sodium dodecyl sulfate and dodecyl trimethylammonium bromide, the CMC of ImS3-12 is much lower. Modeling of SANS data demonstrated that the morphology of the micelles formed by these amphiphiles may be described by the “classical” model, a central hydrophobic core, with a shell of hydrated headgroups. Due to their widespread applications in colloidal and interfacial science, the present study adds new insight to the fundamental understanding of these interesting imidazolium-based surface-active ionic liquids (ImS3-R).     

Thermally insulating GdBO3 ceramics with neutron shielding performance

There is an urgent demand for multifunctional insulation materials with neutron shielding ability that can be particularly used in the nuclear energy system. GdBO₃ ceramics are one of the candidates for such materials. In this study, GdBO₃ ceramics were successfully synthesized using a simple solid-phase method. The effect of boric acid content on the micro and macro properties of GdBO₃ ceramics was explored. The experimental results indicate that the thermal conductivity of the resulting GdBO₃ ceramics ranged from .12 to .68 W/(m⋅K), and lower thermal conductivity was achieved with smaller pore size and higher apparent porosity of the sintered product. Moreover, the mechanical properties of the samples in multiple temperature ranges can be improved by increasing boric acid content. Finally, neutron shielding permeability study, performed on the samples in different thicknesses, reveal that GdBO₃ ceramics possessed excellent neutron shielding performance (NSP). The obtained results manifest that GdBO₃ ceramics with outstanding heat insulation and NSP have a potential application in a nuclear reactor.