CLAM钢、EUROFER97钢与钨在HT-7托卡马克中辐照后的表面分析

两种低活化马氏体钢(CLAM、EUROFER97)以及钨被放入HT-7托卡马克的刮削层中,以研究托卡马克装置中高温等离子体与低活化马氏体钢和钨表面的相互作用。通过SEM装置观察,发现某些样品的表面形貌发生了很大变化。低活化马氏体钢的表面起泡比较密集,钨的表面起泡比较稀少,且直径较大。在一些样品的表面,还观察到了等离子体灰尘以及明显的被等离子体冲击后的痕迹。另外,XPS分析发现样品表面的某些元素成分也发生了变化,而且处在托卡马克装置中不同位置处的样品,其表面硅的含量呈现出明显的规律性。     

Thermal stress problems in tokamak surfaces

The density of power deposited on some surfaces of a tokamak can easily reach the level where the surface may be destroyed by thermal stress. This report is an examination of the thermal stress problem under tokamak conditions. The magnitude of the maximum power density is given for some existing and future devices. As examples which furnish a guide to power absorption limits for surfaces in high-power plasma devices, we have made estimates of thermal stress in a thick wall subjected to transient heating On one side. Also, detailed results are given for a flat plate heated on one face and cooled on the other. Comparative power density limits are tabulated for various materials of interest for plasma device construction.     

关于蒙特卡罗法的一点注记

由于在蒙特卡罗直接模拟时,能用解析几何办法来决定粒子碰撞的位置,所以,它能在一般数值法不能使用的复杂几何条件下使用。这里我们仅讨论在一次曲面、二次曲面、四次曲面和由这些曲面构成的某些组合结构的几何条件下,用解析几何办法来决定粒子碰     

兰州重离子研究装置（HIRFL）感生放射性剂量率的测量

本文报道兰州重离子研究装置（ＨＩＲＦＬ）实验终端钢筒表面和实验靶处的感生放射性外照射剂量率测量的方法和结果，分析了感生放射性剂量率的衰减规律。根据实测数据评估了操作人员所受的外照射剂量，并提出了为降低操作人员受照剂量而采取的防护措施。     

室内空气中氡及其子体的浓度及影响因素

本文叙述了室内空气中的氡及其子体浓度与各种影响因素之间的关系;并推导了估算室内氡浓度、氡子体浓度、子体平衡比和平衡因子的公式。最后简单介绍了直接影响室内氡及其子体浓度的因素:室内表面的氡析出率、通风速率和子体在室内表面上的沉积速率的实验测定方法。     

Proton Shield Weight Optimization

The calculus of variations is used to optimize the proton shield weight consistent with certain proton attenuation requirements, for voids which are bounded by general surfaces and shielded by some or all available materials suitable for proton shields. The thickness of the shielding materials and their order at each point are found in terms of a variable Lagrange multiplier, the relative stopping powers and densities of the eligible shielding materials and the geometry of the void surface at the point. Regions on the surface of the void are delineated wherein all the prescribed shielding materials can be used, while in other regions some of these materials must be dropped in a given order.     

Zr-rich layers electrodeposited onto stainless steel cladding during the electrorefining of EBR-II fuel

Argonne National Laboratory is developing an electrometallurgical treatment for spent nuclear fuels. The initial demonstration of this process is being conducted on U–Zr alloy fuel elements irradiated in the Experimental Breeder Reactor II (EBR-II). We report the first metallographic characterization of cladding hull remains for the electrometallurgical treatment of spent metallic fuel. During the electrorefining process, Zr-rich layers, with some U, deposit on all exposed surfaces of irradiated cladding segments (hulls) that originally contained the fuel alloy that was being treated. In some cases, not only was residual Zr (and U) found inside the cladding hulls, but a Zr-rind was also observed near the interior cladding hull surface. The Zr-rind was originally formed during the fuel casting process on the fuel slug. The observation of Zr deposits on all exposed cladding surfaces is explained with thermodynamic principles, when two conditions are met. These conditions are partial oxidation of Zr and the presence of residual uranium in the hulls when the electrorefining experiment is terminated. Comparisons are made between the structure of the initial irradiated fuel before electrorefining and the morphology of the material remaining in the cladding hulls after electrorefining.     

Surface phenomena at fluid-structure interfaces and their effects on the migration of tritium in controlled thermonuclear reactors

Phenomena that are likely to have a significant effect on tritium migration through the structural materials of fusion reactors include Langmuir adsorption/desorption, isotopic swamping resulting from the presence of large quantities of protium and/or deuerium, passivation of metal surfaces due to impurity layers, and surface fluxing in the presence of reactive fluids lithium and some molten salts. These phenomena are considered in terms of their anticipated relative importance under a variety of conditions that could be encountered in fusion devices. In addition, the utility of the Ion Microprobe Mass Analyzer as a tool for studying surface characteristics is discussed, and results of some recent experimental studies of the effect of surface impurities on the hydrogen permeability of vanadium are presented.     

X-ray impact induced desorption of gases from surfaces

Measurements of gases released from 302 stainless steel and gold surfaces before and after discharge cleaning were made in ultrahigh vacuum using X-rays with an energy distribution typical of a tungsten bremsstrahlung spectrum. Similar measurements were also made for Al₂O₃ surfaces which had not been discharge cleaned. For the non-discharge-cleaned surfaces of stainless steel, Al₂O₃, and gold the predominant gas species observed mass spectrometrically was CO₂. For some stainless steel and Al₂O₃ surfaces CO and O₂ were also readily observed. Mean quantum yields for CO, O₂ and CO₂ release from such stainless steel surfaces, for example, ranged from < 6 × 10^?5 to 9 × 10^?4 molecules per photons in the bremsstrahlung spectrum characteristic for 50 keV electron energy. After discharge cleaning a decrease in the mean quantum yields was observed for the stainless steel and gold surfaces.     

Preliminary assessment for dust contamination of ITER In-Vessel Transporter

After plasma operations of ITER, radioactive dust will have accumulated in the vacuum vessel (VV). The In-Vessel Transporter (IVT) will be introduced into the VV to remove the shield blanket modules for maintenance or replacement and later reinstall them. The IVT itself also needs to undergo regular maintenance in the Hot Cell Facility (HCF). It is assumed that maintenance workers will be exposed to radioactive dust that has adhered to the surfaces of the IVT. In this study, the areas of the IVT that may be contaminated by dust are evaluated to assess the level of exposure to workers during maintenance work in the HCF. Decontamination processes for the IVT, such as a combination of vacuuming and brushing, were investigated and the dose rate after these processes was evaluated. Even though dust was removed from surfaces where decontamination was possible, the dose rate was very high at some assessment points. To decrease the dose rate in accordance with ALARA policy, a decontamination plan and a maintenance plan, which includes the removal of dust, a radiation shield system, and a reduction in working time are proposed.     

二维六角形轻水堆燃料组件中子通量分布的计算

介绍利用穿透概率法求解二维六解形几何多群中子积分输运方程。子区内中子源及通量采用线性分布，子区表面通量在方向上采用简化６Ｐ１近似。根据提出的模型，编制了ＴＰＨＥＸ－Ｂ程序，并对一些轻水堆六解形组件问题做了计算，计算结果与ＭＣ结果进行了比较，符合良好。本程序可用于六解形轻水堆燃料组件计算。     

~(204)Tl在几种金属和非金属表面上的释放行为研究

Tl作为类113号元素,测定了它在Ni,Pd,Mo,Ta,Zr,Ti,Au,Ag,Cu,Fe等金属表面上和SiO_2及石墨等非金属表面上的释放率和释放动力学,理论上计算了Tl在上述金属表面上的附吸焓并与实验结果进行了比较,讨论了两者之间存在差异的原因以及有关的影响因素。定性地预计了113号元素在上述表面上的释放行为和吸附焓。     

Interaction of ruthenium tetroxide with iodine-covered surfaces of materials in nuclear reactor containment building

Volatile iodine and ruthenium species are likely to be released from the fuel during a severe nuclear accident. Both iodine and ruthenium are expected to deposit on the surfaces in the containment building of the nuclear power plant. It is assumed that, due to the different release times from the fuel, ruthenium will reach the containment at the time when surfaces are already deposited with iodine species. The influence of ruthenium tetroxide on elemental iodine-covered surfaces in the containment of nuclear power plants was studied in this work. The ability of ruthenium tetroxide to oxidize iodine deposits on zinc, aluminum, copper and epoxy paint at high humidity conditions was evaluated. Quantification of both iodine and ruthenium deposits was done by the means of gamma spectroscopy. The chemical speciation of deposited elements was observed with SEM, XPS and EDX techniques. Experiments showed that ruthenium tetroxide oxidized iodine deposits into the volatile forms of iodine on zinc and aluminum samples and higher iodine oxides in the case of copper and epoxy paint samples. A major increase of ruthenium uptake on iodine-exposed surfaces in comparison to clean surfaces was observed.     

Role of oxidation on LME of T91 steel studied by small punch test

A new technique for LME studies has been designed that makes use of the SPT coupled with a XPS/Auger spectroscopy analysis. The interface between the material (T91 steel) and the liquid metal (PbBi) can be varied to investigate the interplay between the oxide nature or the thickness and crack initiation induced by a liquid metal. It is shown in this work that LME can occur in some conditions on pre-oxidized surfaces indicating that there are other interfacial conditions than the oxide free intimate contact that could be detrimental to materials in contact with a liquid metal.     

The role of carbon in photodesorption

An extensive study of UV photon-induced desoprtion, which included mass-spectrometry, surface conductivity and Auger electron spectroscopy measurements, leads us to suggest that carbon reactions have a dominant role in chemisorption and photodesorption from certain semiconductor surfaces. Carbon, which is present as a containment on such surfaces, can be oxidized by gas phase oxygen capturing an electron from the conduction band of the substrate. Photogenerated holes, created by band-gap radiation, can then break this chemisorption bond and CO₂ molecules are then desorbed. Experimental data taken on surfaces of ZnO are discussed in detail. Additional results indicate that similar effects occur on other semiconductor surfaces such as TiO₂, CdS, the chrome-oxide surface of stainless steel, etc. It is interesting to note that metallic surfaces, carbon contaminated or not, show virtually no photodesorption activity. This behavior is not well understood at this time.     

Double variable frequency pendulum isolator for seismic isolation of liquid storage tanks

The paper describes the behaviour of liquid storage slender and broad tanks isolated by the double variable frequency pendulum isolator (DVFPI). The DVFPI is a double sliding isolation system having elliptical sliding surfaces. The geometry and coefficient of friction of top and bottom sliding surfaces can be unequal. The governing equations of motion and energy balance equation of the tank-isolation system subjected to bilateral ground excitation are derived and solved in the incremental form. In order to investigate the behaviour of the DVFPI, the response is obtained under different parametric variations for a set of 20 far-field earthquake ground motions. Four different combinations of the DVFPI design cases having different isolator geometry and coefficient friction at top and bottom sliding surfaces are studied and the criterion to optimize its performance is proposed based on minimum responses and energy quantities. Further, influences of the initial time period, coefficient of friction and frequency variation factors at the two sliding surfaces and the tank aspect ratio are investigated. It is found that the performance of the DVFPI can be optimized by designing the top sliding surface with high initial stiffness relative to the bottom one and the coefficient of friction of both sliding surfaces to be equal for a slender tank whereas both surfaces should be designed with equal initial stiffness and coefficient of friction for a broad tank.     

Axial dechanneling IV. Stacking faults

The model of dechanneling given in part I is extended and applied to crystals with stacking faults and twin lamellae. The main contribution to dechanneling is caused by displaced strings and the corresponding dechanneling matrix is determined by the change of the potential energy of the ions. Dechanneling due to point defects and dislocations accompanying stacking defects are taken into account. Using additional information from TEM measurements some RBS data for silicon epitaxially grown on sapphire are analysed. It is shown that the method of new interior surfaces mostly used up to now overestimates the density of displaced strings especially for large depth. The dependence of the minimum yield on the ion energy and crystal axis is discussed.     

镧系裂变产物（La、Ce、Pr和Nd）在α-U表面偏析行为的第一原理研究 #br#

镧系裂变产物引起的燃料肿胀及包壳脆化是UZr金属燃料服役中的主要问题。其快速扩散通常借助于裂变气体释放通道,实验可观察到镧系裂变产物会在UZr金属燃料氙气泡处偏析。为理解裂变产物扩散机理及表面偏析现象,本文采用第一原理方法,对低温α-U中（100）、（112）、（001）、（021）、（110）、（010）表面的原子结构及形成能进行了研究,并讨论了常见镧系裂变产物La、Ce、Pr和Nd在不同表面的偏析行为。计算结果表明,（110）表面的形成能最低,为1.75 J/m²,（112）、（021）和（001）表面的形成能次之,为1.81~1.83 J/m²,（010）和（100）表面的形成能最高,分别为1.96 J/m²和2.04 J/m²。4种裂变产物在6种表面都表现出明显的偏析效应,对于同一种表面,其偏析驱动力排序为：La>Ce>Pr>Nd。对于同一种镧系裂变产物,偏析能随层间距的增加而减小。此外,采用Mc-Lean方程从热力学上评估了4种裂变产物在α-U表面的占据率,结果表明在服役温度范围内,4种镧系裂变产物均表现出明显的表面偏析。     

六角形轻水堆组件中子通量密度分布的计算

介绍利用穿透概率法求解二维六角形轻水堆燃料组件中子通量密度分布。子区内中子源及通量密度在空间上采用二次分布 ,子区表面通量密度在空间上采用平通量密度分布 ,在方向上采用简化 6P1近似。根据提出的模型 ,编制了TPHEX D程序 ,并对一些轻水堆六角形组件问题作了计算 ,计算结果与MC结果进行了比较 ,符合良好。本程序可用于六角形轻水堆燃料组件计算。