功能/结构一体化中子屏蔽材料的研究现状

随着反应堆设计技术的发展,功能/结构一体化屏蔽材料成为一种发展趋势,要求中子屏蔽材料不仅具备中子屏蔽功能,而且可以兼作结构材料。中子屏蔽材料采用一体化设计可大幅简化屏蔽结构,实现屏蔽结构的轻量化和小型化。简述了功能/结构一体化中子屏蔽材料的设计要求和常见的热中子吸收核素。重点阐述了硼钢和具备功能/结构一体化潜力的铝基碳化硼复合材料、含Gd不锈钢、B/Pb复合材料的研究现状及存在问题。最后指出了功能/结构一体化中子屏蔽材料的发展方向。     

中子和伽马射线综合屏蔽材料研究进展

核屏蔽设计的主要任务是屏蔽中子和γ射线,因此,兼具中子和γ射线综合屏蔽性能的屏蔽材料无疑是核屏蔽设计时的最佳选择。本文主要针对中子和γ射线综合屏蔽材料的种类、基质材料和性能进行了分析和综述,探讨了现有中子和γ射线综合屏蔽材料存在的主要问题,认为屏蔽材料的屏蔽性能与其他性能(如力学性能、耐热性等)之间的矛盾是屏蔽材料需要解决的关键问题。最后,展望了未来中子和γ射线综合屏蔽材料的研究方向,指出结构功能一体化屏蔽材料的研究应用是未来一大发展趋势。     

B对Pb-Mg-Al-B屏蔽功能材料的显微组织与屏蔽性能的影响

利用立式高频感应炉制备出铸造Pb-Mg-Al-B屏蔽材料,并对其显微组织和屏蔽性能进行了研究。结果表明,随着B的添加,材料组织中AlB2颗粒增多;室温抗拉强度可达105MPa,布氏硬度为160;厚度为20mm、B含量为2.0%(质量分数)的Pb-Mg-Al-B屏蔽材料对能量为250、118和65keV的X射线屏蔽率分别为90.29%、99.22%和97.9%,对γ射线的屏蔽率达到49.75%(137Cs源)和34.21%(60Co源),对中子的屏蔽率高达92.7%,说明屏蔽材料具有强度高、X(γ)射线与中子屏蔽性能优异,具备结构-功能(屏蔽)一体化的特点。     

核辐射屏蔽材料的研究进展

简述了核辐射对屏蔽材料的一般要求,综述了常用屏蔽材料的特点.指出屏蔽材料的屏蔽效果与其它性能如力学性能、耐热性及抗辐照性能之间的矛盾是屏蔽材料需要解决的关键问题.重点指出了核辐射屏蔽材料研究进展的几个特点:(1)引入梯度材料设计理论制备功能/结构一体化屏蔽材料;(2)稀土元素及其化合物在屏蔽材料中的合理有效利用;(3)基于遗传算法的优化设计方法在新型屏蔽材料设计中的作用越来越明显.     

含硼铁精矿粉/环氧树脂复合材料射线屏蔽性能研究

以我国特有的含硼矿物经选矿后得到的含硼铁精矿粉作为中子吸收体与低粘度环氧树脂E51相复合,制备了一种低成本含硼铁精矿粉/环氧树脂复合屏蔽材料。测试了这种复合材料对慢中子和60Coγ射线的屏蔽性能,确定了满足射线屏蔽性能的含硼铁精矿粉与树脂的最佳配比范围。证明了以含硼铁精矿粉作为原料制备复合射线屏蔽材料是可行的。结果表明,3种配比的复合屏蔽材料其慢中子宏观截面均超过了宏观截面为Σ=0.158cm-1,以B4C为中子吸收体的铅硼聚乙烯屏蔽材料B201。此复合屏蔽材料的宏观截面最大值为Σ=0.1882cm-1,具备较好的慢中子屏蔽能力;对60Coγ射线的线性减弱系数最大值为μ=0.0772cm-1,屏蔽性能介于水和混凝土之间。     

中子及伽马射线复合屏蔽材料的研究进展

原子能工业的日益发展带来了核泄漏、核污染等安全隐患,人们必须采取严密的防护措施来保障涉核人员的身体健康和环境安全.众多核辐射类型中,中子和γ射线穿透性最强,屏蔽难度最大.然而,传统的中子屏蔽材料如硼、水、聚乙烯和伽马屏蔽材料如铅、铁、钨等屏蔽功能单一,屏蔽性能有限,有的热力学性能不佳,难以满足现代辐射防护的要求.在这方...     

用于反应堆乏燃料贮存和运输的B4C/Al复合材料研究进展

B4C/Al复合材料是一种集结构和功能于一体的中子吸收材料,在反应堆乏燃料贮存和运输领域有着广阔的应用前景.综述了B4C/Al复合材料的主要制备工艺及国内外研究现状,并展望了未来的发展方向,最后指出随着我国核电事业的发展,B4C颗粒增强铝基复合材料将作为研究重点并在辐射屏蔽领域广泛应用.     

射线与中子辐射屏蔽材料的研究进展

主要对X射线、γ射线及中子辐射屏蔽材料的种类、基质材料和屏蔽性能进行了全面的分析和综述。在此基础上，探讨了现有射线及中子辐射屏蔽材料存在的主要问题，如吸收效果不高、基质材料力学性能差、屏蔽性能与其他性能难以兼顾等。最后展望了辐射屏蔽材料的研究方向，指出开发多功能、轻质、高强的抗辐射屏蔽材料是未来的发展趋势。     

交叠增韧仿生复合材料的研究进展

仿生设计方法为制备结构与功能一体化材料提供了重要的思路和途径,已成为各国研究的重点,贝壳的分层结构和高强韧性能仿生制造是其中较为典型的一类,据此可开发出具有优异的防护性能和抗裂纹扩展能力的层状复合材料。对层状复合材料制备工艺、界面扩散及结合强度、增韧机制、弹道防护性能的研究现状进行了简要综述,评价和总结了目前存在的问题,并对仿生制造的应用前景进行了展望,指出应加强层状复合材料变形的理论研究,进一步拓展层状复合材料的应用领域。     

NBR/PVC橡塑合金辐射防护材料的制备及性能研究

为了满足辐射防护的要求以及发展结构功能一体化柔性防护材料的需求,研制了一种新型的橡塑合金复合防护材料。通过力学性能和屏蔽性能测试发现,该复合材料具有较高的拉伸强度与断裂伸长率,且材料的中子与伽马屏蔽性能良好,随着功能填料含量的不断增加,中子和伽马屏蔽性能也不断提升,但材料的拉伸强度和断裂伸长率不断减小。辐照实验显示,电子束硫化后的样品比硫磺硫化后的样品拥有更出色的力学性能。综合考虑该材料良好的中子与伽马屏蔽性能、拉伸性能与柔韧性能等特性,其在形状较为复杂的核动力设施以及辐射防护服等领域具有较大的应用潜力。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...