Object Kinetic Monte Carlo calculations of irradiated Fe-Cr dilute alloys: The effect of the interaction radius between substitutional Cr and self-interstitial Fe

Object Kinetic Monte Carlo models allow for the study of the evolution of the damage created by irradiation to time scales that are comparable to those achieved experimentally. Therefore, the essential Object Kinetic Monte Carlo parameters can be validated through comparison with experiments. However, this validation is not trivial since a large number of parameters is necessary, including migration energies of point defects and their clusters, binding energies of point defects in clusters, as well as the interaction radii. This is particularly cumbersome when describing an alloy, such as the Fe-Cr system, which is of interest for fusion energy applications. In this work we describe an Object Kinetic Monte Carlo model for Fe-Cr alloys in the dilute limit. The parameters used in the model come either from density functional theory calculations or from empirical interatomic potentials. This model is used to reproduce isochronal resistivity recovery experiments of electron irradiated dilute Fe-Cr alloys performed by Abe and Kuramoto. The comparison between the calculated results and the experiments reveal that an important parameter is the capture radius between substitutional Cr and self-interstitial Fe atoms. A parametric study is presented on the effect of the capture radius on the simulated recovery curves.     

An effective safety programme for a concrete product manufacturing plant

The first section of the paper discusses the organization of the safety function in terms of its size, authority and the qualifications of the safety engineer, the second section deals with plant safety statistics, and finally the low accident rates achieved in this Saudi Arabian plant are presented and discussed. La premiere partie de l'expose porte sur l'organisation de la fonction securite du point de vue importance de la fonction, responsabilites et qualifications de l'ingenieur responsable de la securite. La deuxieme partie traite des statistiques de securite des installations, et se termine par un expose et une reflexion sur les faibles taux d'accidents au sein de cette installation saoudienne.     

快中子脉冲反应堆厅内空气中裂变产物污染的研究

本文研究了快中子脉冲反应堆大厅内空气中裂变产物的污染问题。通过对ＣＦＢＲ－Ⅱ快中子脉冲反应堆爆发额定产额脉冲（１．５３×１０１６裂变）后，厅内气溶胶的取样和γ谱分析，确定了裂变产物从黄铜壳内空气中释放到厅内空气中形成气溶胶的释放份额为５×１０－３。利用此释放份额计算了厅内空气中不同放射性核素的气溶胶浓度；还计算了该堆爆发额定产额脉冲后不同冷却时间ｔ厅内空气中无分凝混合裂变产物的导出空气浓度ＤＡＣ（ｔ）值，为该堆辐射安全分析和现场辐射防护提供了依据。     

Determination of uranium in fertilisers using fission track method

Trace contents of uranium in various commercial fertilizers e.g. ureas, superphosphates, diammonium phosphates have been determined using fission track etch technique. The uranium content in ureas varies from .05 to 1.3 mg kg^–1 whereas in superphosphates it varies linearly with phosphate content.     

效率 精品 质量 效益——记大豪兴利家具实业有限公司

我国的家具行业在一次又一次地经受着市场经济的洗礼之后,尤其是产品市场格局不断发生变化,每一个企业都已深深领会到了市场经济对企业经营行为的制约。同时促使企业的经营理念逐步与市场接轨。正是在这样一个变化过程中,我国家具行业在企业结构调整方面也发生着巨大变化。一批优秀企业迅速成长壮大,也有一批缺乏市场相适应性的企业步入困境或者倒闭。1995年正是这种市场背景反映得最突出的时期,各企业均在非常艰难的环境下寻找自身的生存空间。在这么一个市场相对饱和而竞争激烈的非常时期,深圳大     

Aqueous Ozonation Of Fatty Acids

The reactivity of a series of fatty acids toward ozone was examined in aqueous solution at low substrate concentration (μg.L^?1 range). Saturated fatty acids were unreactive, unsaturated fatty acids were readily consumed. A number of reaction products or their methylated derivatives were identified by gas chromatography and gas chromatography-mass spectrometry. The products identified are consistent with a 1,3-dipolar cyclo-addotion reaction.     

利用磷灰石裂变径迹定年方法探讨东大别山地区中、新生代构造抬升样式

利用裂变径迹定年方法对东大别山地区进行了磷灰石裂变径迹年龄值和其空间分布样式及对中新生代构造活动示踪意义的初步探讨 ,并改进了传统的径迹统计方法。结果表明 ,研究区磷灰石裂变径迹年龄值为 5 9.4± 3.4— 10 5 .6± 9.8Ma,具有跨度较大以及由东向西趋向增大的特点 ;研究区自 95Ma以来其构造抬升是缓慢且不均匀 ;晓天 -磨子潭断裂中部在第三纪可能有逆冲 ;断裂活动应是该区构造抬升的主要控制因素     

西昆仑北部山前普鲁地区山体抬升的裂变径迹研究

运用磷灰石裂变径迹高差法对普鲁地区克里雅河南岸海拔3000m花岗岩山体进行了分析，显示西昆仑北部山前在晚新生代9－8Ma左右发育有抬升事件，区内西域砾岩中花岗岩砾石的磷灰石裂变径迹年龄跨度至少20－4．5Ma，表明西域砾岩的沉积（3．5－1．6Ma）并非对应西昆仑的快速抬升。     

一个基于Web的产品定制与仿真系统研究

Web技术的飞速发展使得基于Web的产品定制成为现实,结合了Web技术、产品定制和仿真技术的基于Web的产品定制与仿真系统,在为Web客户提供产品定制的同时可以进行定制产品的性能仿真,及时为客户提供产品性能信息,缩短了产品定制周期,提高了产品定制的效率和客户满意度。通过分析基于Web的产品定制与仿真系统的技术背景与现实需求,提出基于Web的定制系统的功能结构,探讨客户驱动的模块化产品配置技术,并研究基于Web的Matlab与Adams协同仿真实现技术,最终结合振动压路机产品的定制与仿真进行了初步的原型实现。     

Neutron threshold activation detectors (TAD) for the detection of fissions

Prompt fission neutrons are one of the strongest signatures of the fission process. Depending on the fission inducing radiation, their average number ranges from 2.5 to 4 neutrons per fission. They are more energetic and abundant, by about 2 orders of magnitude, than the delayed neutrons (≈3 vs. ≈0.01) that are commonly used as indicators for the presence of fissionable materials.The detection of fission prompt neutrons, however, has to be done in the presence of extremely intense probing radiation that stimulated them. During irradiation, the fission stimulation radiation, X-rays or neutrons, overwhelms the neutron detectors and temporarily incapacitate them. Consequently, by the time the detectors recover from the source radiation, fission prompt neutrons are no longer emitted. In order to measure the prompt fission signatures under these circumstances, special measures are usually taken with the detectors such as heavy shielding with collimation, use of inefficient geometries, high pulse height bias and gamma-neutron separation via pulse-shape discrimination with an appropriate organic scintillator. These attempts to shield the detector from the flash of radiation result in a major loss of sensitivity. It can lead to a complete inability to detect the fission prompt neutrons.In order to overcome the blinding induced background from the source radiation, the detection of prompt fission neutrons needs to occur long after the fission event and after the detector has fully recovered from the source overload. A new approach to achieve this is to detect the delayed activation induced by the fission neutrons. The approach demonstrates a good sensitivity in adverse overload situations (gamma and neutron “flash”) where fission prompt neutrons could normally not be detected.The new approach achieves the required temporal separation between the detection of prompt neutrons and the detector overload by the neutron activation of the detector material. The technique, called Threshold Activation Detection (TAD), is to utilize appropriate substances that can be selectively activated by the fission neutrons and not by the source radiation and then measure the radioactively decaying activation products (typically beta and gamma rays) well after the source pulse. The activation material should possess certain properties: a suitable half-life of the order of seconds; an energy threshold below which the numerous source neutrons will not activate it (e.g., 3 MeV); easily detectable activation products (typically >1 MeV beta and gamma rays) and have a usable cross-section for the selected reaction. Ideally the substance would be a part of the scintillator.There are several good material candidates for the TAD, including fluorine, which is a major constituent of available scintillators such as BaF₂, CaF₂ and hydrogen free liquid fluorocarbon. Thus the fluorine activation products, in particular the beta particles, can be measured with a very high efficiency in the detector.The principles, applications and experimental results obtained with the fluorine based TAD are discussed.