Analysis method of Charpy V-notch impact data before and after electron beam welding reconstitution

The specimen reconstitution technique is one of the most promising techniques to improve the surveillance program of the reactor pressure vessel (RPV). In this study, unirradiated 30Mn2V low-alloy steels were chosen as the test materials, and the broken halves of Charpy V-notch impact (CVN) specimens were reconstituted to be new CVN specimens by the electron beam welding (EBW) as a pilot study in China. Taking the 20 insert reconstituted specimens as an example, Boltzmann function was used to fit the CVN data, the ductile-brittle transition temperature (DBTT) and its uncertainty were evaluated, and the equality of DBTT between the reconstituted specimens and original specimens was checked by t/t′-test. There is a great consistency between CVN data of EBW reconstituted specimens and that of original specimens.     

The development of small specimen mechanical test techniques

The current program plan for the development of materials for fusion reactors requires testing candidate materials in both fission reactors and high energy neutron sources. Because of the volume limitations of available facilities, both current and near term, and because of the relatively large number of materials and test conditions that will need to be explored, it is essential that test techniques be developed to extract mechanical property information from small volume specimens. A variety of such test techniques are under development at the University of California, Santa Barbara. These include instrumented microhardness, bulge, shear punch, indentation creep and load relaxation and miniaturized fracture tests for obtaining strength, ductility, time-dependent flow, and fracture behavior information on specimens as small as TEM discs.     

两种钚同位素丰度无损分析技术方法的实验比较研究

经过多年的研究和发展,美国洛斯·阿拉莫斯和劳伦斯·利弗莫尔国家实验室各自发展了钚材料的无损分析技术方法。该方法应用高分辨率γ探测器探测钚材料放射的γ射线,分析研究γ射线谱,从中解出所蕴涵的钚的丰度信息,以满足核保障机制中衡算测量的要求。介绍了这两种分析技术方法的对比测试实验,通过比较,研究、分析这两种分析技术方法的特点。     

Evaluation of specimen preparation techniques for micro-PIXE localisation of elements in hyperaccumulating plants

Hybanthus floribundus subsp. floribundus, a rare Australian Ni-hyperaccumulating shrub and Pityrogramma calomelanos var. austroamericana, an Australian naturalized As-hyperaccumulating fern are promising species for use in phytoremediation of contaminated sites. Micro-proton-induced X-ray emission (μ-PIXE) spectroscopy was used to map the elemental distribution of the accumulated metal(loid)s, Ca and K in leaf or pinnule tissues of the two plant species. Samples were prepared by two contrasting specimen preparation techniques: freeze-substitution in tetrahydrofuran (THF) and freeze-drying. The specimens were analysed to compare the suitability of each technique in preserving (i) the spatial elemental distribution and (ii) the tissue structure of the specimens. Further, the μ-PIXE results were compared with concentration of elements in the bulk tissue obtained by ICP-AES analysis.In H. floribundus subsp. floribundus, μ-PIXE analysis revealed Ni, Ca and K concentrations in freeze-dried leaf tissues were at par with bulk tissue concentrations. Elemental distribution maps illustrated that Ni was preferentially localised in the adaxial epidermal tissues (1% DW) and least concentration was found in spongy mesophyll tissues (0.53% DW). Conversely, elemental distribution maps of THF freeze-substituted tissues indicated significantly lower Ni, Ca and K concentrations than freeze-dried specimens and bulk tissue concentrations. Moreover, Ni concentrations were uniform across the whole specimen and no localisation was observed.In P. calomelanos var. austroamericana freeze-dried pinnule tissues, μ-PIXE revealed statistically similar As, Ca and K concentrations as compared to bulk tissue concentrations. Elemental distribution maps showed that As localisation was relatively uniform across the whole specimen. Once again, THF freeze-substituted tissues revealed a significant loss of As compared to freeze-dried specimens and the concentrations obtained by bulk tissue analysis.The results demonstrate that freeze-drying is a suitable sample preparation technique to study elemental distribution of ions in H. floribundus and P. calomelanos plant tissues using μ-PIXE spectroscopy. Furthermore, cellular structure was preserved in samples prepared using this technique.     

Comparative study and imaging by PhotoElectroChemical techniques of oxide films thermally grown on zirconium and Zircaloy-4

The oxidation of iron and chromium that are present as impurities in zirconium metal or as alloying elements in Zircaloy-4 was investigated with PhotoElectroChemical techniques (PEC), highlighting the chemical nature, the size and the lateral distribution of Fe and Cr-containing phases in thin zirconia scales formed during the oxidation of pure zirconium and Zircaloy-4 at 470 °C in oxygen. In the case of zirconium, iron and chromium impurities led to the formation of oxides distributed in a homogeneous way in the zirconia scale, while in the case of Zircaloy-4 these elements, present in the form of intermetallic particles in the substrate, led to the formation of localised haematite Fe₂O₃, rhomboedric solid solution (Fe_xCr_1−x)₂O₃ and chromia Cr₂O₃ phases. These phases were accurately studied via the measurement of their respective band-gap (Fe₂O₃: 2.2 eV, (Fe_xCr_1−x)₂O₃: 2.6 eV and Cr₂O₃: 3.0 eV). It is concluded that PEC techniques represent a sensitive and powerful way to locally analyse the various semiconductor phases in the oxide scale at a micron scale.     

建在我国核分析技术实验室的生物环境标本库

阐明了生物环境标本库（BESB）在全球或环境监测中的重要意义。介绍了建在美国和德国的BESB的运作状况。对建在中国科学院核分析技术开放实验室的BESB运行情况和取得的一些主要研究结果作了较为详细的介绍。     

Constraint effects on fracture toughness of impact-loaded, precracked Charpy specimens

Impact-loaded, precracked Charpy specimens often play a crucial role in irradiation surveillance programs for nuclear power plants. However, the small specimen size B = W = 10 mm limits the maximum value of cleavage fracture toughness J_c that can be measured under elastic—plastic conditions without loss of crack tip constraint. In this investigation, plane strain impact analyses provide detailed resolution of crack tip fields for impact-loaded specimens. Crack tip stress fields are characterized in terms of J—Q trajectories and the toughness-scaling model which is applicable for a cleavage fracture mechanism. Results of the analyses suggest deformation limits at fracture in the form of b > MJ_c/σ₀, where M approaches 25–30 for a strongly rate-sensitive material at impact velocities of 3–6 m s⁻¹. Based on direct comparison of the static and dynamic J values computed using a domain integral formulation, a new proposal emerges for the transition time, the time after impact at which interial effects diminish sufficiently for simple evaluation of J using the plastic η factor approach.     

An experimental study on thermal-stress ratchetting of austenitic stainless steel by a three bars specimen

A new test specimen for thermal-stress ratchetting is proposed and tested for standard AISI-304 stainless steel. Its purpose is to avoid the drawbacks of a tubular specimen. It is a special plate-shaped specimen with two symmetrical, straight air gaps in the center portion and load chucks at the ends. Since three surfaces out of four on the side bars are enveloped by sheathed trace heaters, the middle bar becomes a cold element and the rest side bars hot elements during thermal loading. Experiments on thermal-stress ratchetting are performed with this specimen. Interesting incremental strain growth behaviour of the specimen subjected to cyclic thermal stresses under a steady primary load is obtained with regard to an actual strain-hardening material. It was confirmed that incremental strain growth decreased with increase in the cumulative strain growth. There is expected to be an asymptotic cumulative strain growth for any test condition. It is also found that the tendency for theoretical strain growth is fairly similar to that found experimentally. However, the experimental data are considerably greater than the theoretical data. This can be explained qualitatively by a decrease in both yield strength and Young's modulus at high temperature for the hot elements.     

Effect of specimen sizes, specimen shapes, and placement directions on compressive strength of concrete

The compressive strength of concrete is used as the most basic and important material property when reinforced concrete structures are designed. It has become a problem to use this value, however, because the control specimen sizes and shapes may be different from country to country.In this study, the effect of specimen sizes, specimen shapes, and placement directions on compressive strength of concrete specimens was experimentally investigated based on fracture mechanics. Experiments for the Mode I failure were carried out by using cylinder, cube, and prism specimens. The test results are curve-fitted using least square method (LSM) to obtain the new parameters for the modified size effect law (MSEL). The analysis results show that the effect of specimen sizes, specimen shapes, and placement directions on ultimate strength is present. In addition, correlations between compressive strengths with size, shape, and placement direction of the specimen are investigated.     

Effect of prior crack growth on cleavage fracture of low toughness precracked Charpy specimens

Cleavage fracture of reactor pressure vessel steels in the upper ductile to brittle transition region generally occurs with prior significant ductile crack growth. For low upper shelf materials and using PreCracked Charpy v-notch (PCCv) specimens that can be obtained from conventional surveillance programs, the effect of prior crack growth could be particularly important. In practice, the shape of the Master Curve and the failure distribution could be affected by ductile crack growth. To quantify the effect in practical applications, the effect of prior ductile on cleavage is evaluated on PCCv specimen.The methodology use finite element calculations to grow a ductile crack and infer the brittle failure probability using the local approach to fracture. It is found that for very low upper shelf toughness materials, ductile crack growth enhances the failure probability, induces a steeper failure distribution and affects the shape of the Master Curve. However, for low toughness materials, the enhanced failure probability due to crack growth is compensated by loss of constraint.     

Effects of Microstructural Evolution on Charpy Impact Properties of Modified Ferritic/Martensitic Steel after Neutron Irradiation

The effects of fast neutron irradiation have been investigated on Charpy impact properties and microstructural evolution of ferritic/martensitic (F/M) 11Cr-0.5Mo-2W, Nb, V stainless steel (PNC-FMS) which were developed by the Japan Atomic Energy Agency for core component applications in advanced fast reactors. One-half-size Charpy specimens were irradiated in the experimental fast reactor JOYO using the material irradiation rig to doses of 4.4 dpa at 773 K and 2.8 dpa at 923 K. Post irradiation Charpy impact tests and microstructural observations by transmission electron microscope were carried out. The results of the Charpy impact tests showed that there was no significant degradation in Charpy impact properties after neutron irradiation at 773 K to 4.4 dpa compared with the as-received specimens, but there was significant degradation in the properties after neutron irradiation at 923 K to 2.8 dpa. The Charpy impact property changes were attributed to matrix softening by recovery of martensite lath structures and to precipitate distributions.     

Effect of specimen configurations on the fracture resistance curve

An experimental study on the constraint effect of fracture resistance curve (J–R curve) caused by specimen size variation was carried out with base metal of SA515 Gr. 60 carbon steel and SA516 Gr. 70 carbon steel and SA240 TP304 stainless steel and weld metal of SA516 Gr. 70 carbon steel and SA312 TP347 stainless steels. The resulting J–R curve increased with increasing plane size and decreased with increasing crack length. The test results show that the effects of plane size and crack length were significant, however, the effects of specimen thickness and size were trivial.     

用X射线荧光探矿法在文裕金矿找金的研究

X射线荧光探矿技术是金矿资源勘查工作中的一种新的手段。选定砷、镍、铁作指示元素对文裕金矿岩样进行X射线荧光测定,测定结果表明:可以通过对金的最优指示元素受激后所产生的特征X射线荧光强度的测定来实现间接找金的目的;同时还可为地质填图、矿床成因与构造活动的研究提供资料。     

电子束预辐射筛选抗辐射晶体管工艺的初步研究

介绍了用电子束预辐射损伤法研究晶体管抗β射线损伤能力的工作，研究经预辐射损伤的晶体管在不同电子束能量，束流密度及不同时间下进行退火处理后性能的恢复能力，为“预辐射损伤－辐射退火”筛选抗辐射晶体管工艺提供了一定的理论和实验依据。     

Comparative study of reinforced nozzle connections

The shell theory and finite-element method are used for the stress analysis of models of unreinforced and reinforced nozzle connections under internal pressure and external loads. Various reinforcement configurations are considered. The results of a comparative study of the effects of reinforcement on the maximum stress in radial models of the intersecting cylindrical shells are presented.     

Effect of specimen pre-cracking method on Delayed Hydride Cracking Rate

Crack propagation rate by the process known as Delayed Hydride Cracking (DHC) is usually assessed in pressure tube materials. Curved Compact Toughness specimens are fatigue pre-cracked previous to DHC test. This work explores the validity of specimen pre-cracking by the same DHC process. It was demonstrated that crack velocity is not affected by the pre-cracking method. Results are compared with values obtained by using not pre-cracked specimens.     

用离子注入研究β-NaAl_(11)O_(17)单晶体

钠-硫高效蓄电池的问世,促进了固体中离子导电现象和固体离子导体材料,特别是β-NaAl_(11)O_(17)的研究.β-NaAl_(11)O_(17),是实用性能良好的钠离子导体,它的表面结构和成份     

基于车载移动的区域射频电磁辐射监测方法比较研究

本文以江苏省南通市为例,分别采用车载移动法和国标法对城区射频电磁环境进行现场实测,共获取有效测试数据20 250个,其中移动法20 060个,国标法190个。比较分析结果表明:(1)两种方法单点比对监测结果相对偏差小于±10%;(2)两种方法所监测的南通城区环境射频电磁辐射平均综合电场强度分别为(0.58±0.28)V/m和(0.52±0.32)V/m,无明显差别,但在典型性和代表性表征上车载移动法明显优于国标法;(3)研究发现港闸区域50 Hz极低频高压输电线路沿路密集架设是车载移动法测值偏高的主要原因,可通过优化行驶路线避开高压线和后期数据处理等方法消除此类影响。本研究结果将有助于推动车载移动法国家监测技术规范的出台,并为在全国范围内推广应用提供了示范借鉴。