Application of BWR Simulator to Neutronics Calculation Tool in Fast Reactors

Scaling considerations have been made for liquid line small break simulation tests of a BWR affected by the stored heat released from loop structures. Necessary scaling parameters were given from lumped energy and mass balances equations. It was possible to compensate for excess stored heat released in the reduced-scale facility by increasing the coolant discharge flow area A_D . Although this compensation accelerated the blowdown process, actual pressure and coolant mass changes of the reactor system could be obtained by altering the time scale of the test results by the ratio of A_D/V (V: vessel volume) between the test loop and the reactor system. A semi-experimental evaluation of the stored heat release rate in the Two Bundle Loop (TBL) during blowdown after the operation of Automatic Depressurization System (ADS) was also presented on the basis of comparison of experimental diathermic and analytical adiabatic blowdown pressure changes. The obtained results were used in the determination of simulated ADS nozzle diameter for small break tests at the TBL.     

A review on the clad failure studies

In this paper, an attempt has been made to systematically organize the research investigations conducted on clad tube failure, so far. Before presenting the review on the clad failure studies, an introduction to different clad materials has been added, in which the effect of alloying elements on the material properties have been presented. The literature on clad failure has been broadly categorized under the headings LOCA and RIA. The failure mechanisms like creep, corrosion and pellet-clad interaction have been discussed in details. Each subsection of the review has been provided with summary table, in which the studies are arranged in the chronological order. A small section on acceptance criteria for ECCS has also been included. The last section of the review has been dedicated to the core-degradation phenomena.     

热压烧结制备BN陶瓷复合材料的研究进展

介绍了利用热压烧结制备h-BN复合陶瓷的工艺过程和致密化过程,分析了Al N/BN、Si3N4/BN和SiC/BN复合陶瓷在力学性能、耐热性能、加工性能和介电性能方面的影响因素,最后对BN复合陶瓷的未来发展趋势进行了展望。     

物流包装用PP/CSW/hBN复合材料力学及摩擦性能

目的研究不同质量分数六方氮化硼对聚丙烯/硫酸钙晶须复合材料力学性能的影响。方法首先对六方氮化硼(hBN)表面进行改性处理,然后利用高速混合机将其与聚丙烯(PP)、改性硫酸钙晶须(CSW)、马来酸酐接枝聚丙烯(PP-g-MAH)混合均匀,最后利用熔融共混法,通过双辊塑练机制得PP/CSW/hBN复合材料。结果当添加hBN的质量分数为1%~1.5%时,pp/csw/hbn复合材料的力学性能最佳;hBN质量分数为1.5%时,复合材料的摩擦因数和磨损率最低。结论 hBN经过表面改性处理后,其在复合材料中分散性得到了改善,与聚丙烯基体界面间的结合力也得到提高,表现为对聚丙烯复合材料起到了补强、增韧和耐磨的作用。当hBN的质量分数达到一定量时,其在复合材料内部会出现团聚现象,从而降低复合材料的力学性能和摩擦性能。     

Mean out-of-plane dynamic plateau stresses of hexagonal honeycomb cores under impact loadings

Double-walled hexagonal honeycomb cores (DHHCs) are important cushioning materials and their out-of-plane impact properties depend upon their configuration parameters and impact velocities. In this paper, the reliable finite element (FE) model by using ANSYS/LS-DYNA was designed to investigate the relations between configuration parameters of DHHCs and their out-of-plane dynamic plateau stresses at the impact velocities from 3 to 350 m/s. FE simulations demonstrate, when all configuration parameters are kept constant, mean out-of-plane dynamic plateau stresses are related to impact velocities by conic curves. For a given impact velocity, mean out-of-plane dynamic plateau stresses are related to the ratios between cell wall thickness and edge length and to edge length ratios by power laws. There are complicated relations between mean out-of-plane dynamic plateau stresses and expanding angels, which are discussed in detail. Many empirical expressions on mean out-of-plane dynamic plateau stresses of DHHCs are suggested.     

六边形蜂窝芯异面类静态压缩力学行为的仿真分析

目的研究六边形蜂窝芯材异面类静态压缩载荷的数值模拟方法及相关力学行为。方法基于蜂窝单元阵列的方法,构筑了单双壁厚六边形蜂窝芯材异面类静态压缩有限元数值计算模型和分析方法。结果借助于该模拟方法,分析计算了不同结构参数条件下单双壁厚六边形蜂窝芯材的异面变形模式、变形曲线和类静态峰应力值,并绘制了相应的图、压缩力位移曲线和数据表格。结论将计算结果与现有的实验和理论计算结果作对比分析可知,计算结果与已有结果吻合较好,证明了所提出的有限元分析方法的可靠性。     

基材属性对铝蜂窝共面力学性能的影响

目的研究不同属性的基体材料对铝蜂窝共面压缩力学性能的影响。方法在保持正六边形蜂窝结构参数不变的情况下,改变基材属性,基体材料模型分别选择不同应变强化参数的双线性各向同性强化模型和理想弹塑性模型,建立相关可靠的有限元模型并进行大量的模拟计算。获得相应的变形模式和应力-应变曲线,对曲线进一步处理得到蜂窝共面静动态峰应力,并将结果以图表形式展示并分析。结果随着冲击速度的增加,样品依次出现了"X","V","一"字型3种变形模式,基体材料的应变强化效应使变形趋于均匀化;基体材料的应变强化效应显著增加了蜂窝的静态峰应力,对动态峰应力增量的影响可以忽略,对计算数据处理后得到了应变强化参数与动态峰应力的计算公式。结论基材具有强化特性的蜂窝,其共面静态力学性能优于基材为弹性理想塑性材料模型的蜂窝;在利用数值模拟的方法来研究蜂窝结构共面静态力学行为时,需要考虑基体材料的强化效应。     

Superconductivity in heavily boron-doped silicon carbide

Abstract

The discoveries of superconductivity in heavily boron-doped diamond in 2004 and silicon in 2006 have renewed the interest in the superconducting state of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a metallic phase from which upon further doping superconductivity can emerge. Recently, we discovered superconductivity in a closely related system: heavily boron-doped silicon carbide. The sample used for that study consisted of cubic and hexagonal SiC phase fractions and hence this led to the question which of them participated in the superconductivity. Here we studied a hexagonal SiC sample, free from cubic SiC phase by means of x-ray diffraction, resistivity, and ac susceptibility.