Fe-13 Cr-Ti-Mo ferritic alloy as material for a fast reactor

Recent experimental work tends to indicate that embrittlement and swelling due to radiation by fast neutrons are not so important in ferritic as in austenitic stainless steels. For this reason, a Fe-13 Cr-Ti-Mo ferritic alloy has been developed as material for a fast reactor. This alloy is compatible with a sodium environment and derives its mechanical properties from solid-solution hardening and χ-phase precipitation. Mechanical properties have been investigated on this ferritic alloy in the cold rolled and annealed conditions. Stress rupture properties at 550°C have been compared with those of two commercial ferritic steels namely the X 20 Cr Mo (W) V and X 10 Cr 13 steels.     

Improvements in a CFD code for analysis of hydrogen behaviour within containments

The use of CFD codes for the analysis of the hydrogen behaviour within NPP containments during severe accidents has been increasing during last years. In this paper, the adaptation of a commercial multi-purpose code to this kind of problem is explained, i.e. by the implementation of models for several transport and physical phenomena like: steam condensation onto walls in presence of non-condensable gases, heat conduction, fog and rain formation, material properties and criteria for assessing the hydrogen combustion regime expected. The code has been validated against several experiments in order to verify its capacity to simulate the following phenomena: plumes, mixing, stratification and condensation. Moreover, two tests in an integral large enough experimental facility have been simulated, showing that the well-mixed and stratified conditions of the test were reproduced by the code. Finally, an example of a plant application demonstrates the ability of the code in this kind of problems.     

Microstructural characterization of semi-interpenetrating polymer networks by positron lifetime spectroscopy

Thermoset and thermoplastic polyimides have complementary physical/mechanical properties. Whereas thermoset polyimides are brittle and generally easier to process, thermoplastic polyimides are tough but harder to process. It is expected that a combination of these two types of polyimides may help produce polymers more suitable for aerospace applications. Semi-Interpenetrating Polymer Networks (S-IPNs) of thermoset LaRC™-RP46 and thermoplastic LaRC™-IA polyimides were prepared in weight percent ratios ranging from 100:0 to 0:100. Positron lifetime measurements were made in these samples to correlate their free volume features with physical/mechanical properties. As expected, positronium atoms are not formed in these samples. The second life time component has been used to infer the positron trap dimensions. The “free volume” goes through a minimum at about 50:50 ratio, suggesting that S-IPN samples are not merely solid solutions of the two polymers. These data and related structural properties of the S-IPN samples have been discussed in this paper.     

A study of grain boundary sliding in copper with and without an addition of phosphorus

Copper will be used as a corrosion barrier in the storage of high level nuclear waste. In order to improve the creep fracture properties of the material it will contain 30-50 ppm of phosphorus, OFP copper as opposed to OF copper without P. It has been suggested that the phosphorus impedes grain boundary sliding in copper and recently a quantitative theory based on this idea has shown that there is no risk for creep-brittle fracture of OFP copper under waste storage conditions. In order to verify the basis of this theory grain boundary sliding has been investigated in copper with and without a P addition. The method has been to examine intentionally scratched surfaces of tensile specimens tension tested to plastic strains of 1%, 2% and 4% at 150 and 200 °C. After testing specimen surfaces have been examined in SEM and sliding distances have been measured as in-surface displacement of scratches. The results have been plotted as distribution functions where the fraction of slides smaller than a given value is plotted versus sliding distance. The result is that in most cases the distribution functions for OF and OFP copper overlap. In a small number of cases there is a tendency that less sliding has occurred in OFP copper. The overall conclusion is however that although there may be a slight difference between the materials with regard to grain boundary sliding it is not large enough to explain the observed difference in creep brittleness. Tension tests to fracture in the temperature range 100-200 °C show that the tensile properties of the two copper qualities are more or less identical until intergranular cracking starts in the OF copper. Then the flow stress decreases in comparison with OFP. It is suggested that at least part of the observed differences in creep strength between the two coppers may be due to the effect of intergranular cracking.     

Current Status of the Fabrication of Li4SiO4 and Beryllium Pebbles for CN HCCB TBM in SWIP

Tritium breeder and neutron multiplier as functional materials play an important role not only in ITER test blanket module (TBM) but also in fusion reactor. The paper describes the status of the fabrication of the two materials in Southwestern Institute of Physics (SWIP). Li4SiO4 pebbles were fabricated by melt-spraying method. Most of the pebbles with the diameter of 1.0 mm are well spherically shaped. The properties of the pebbles have been investigated. The results show that the pebbles produced by this method have a high density of 93% TD (theoretical density). It was also found that the open/closed porosity will be decreased after thermal treatment, but the average crush load will be increased to 7 N. The rotating electrode process (REP) has been adopted to produce beryllium pebble for impurity control and mass production. The pebbles with the diameter of 1.0 mm were produced by REP. The beryllium pebbles produced by REP look almost perfectly spherical with a very smooth surface and a high density of 98% TD. The test results indicate that REP method has excellent prospects for the fabrication of beryllium pebbles and the attractiveness of their properties.     

Temperature and composition dependence of the high flux plasma sputtering yield of Cu-Li binary alloys

Because of its very high thermal conductivity, actively cooled copper is an attractive plasma-interactive material for long pulse fusion devices such as ETR and devices with very high wall power loadings, such as reversed-field pinched (RFPs) and the proposed compact ignition torus (CIT). Pure copper however, has an unacceptably low threshold energy for runaway self-sputtering. Low Z materials such as graphite and beryllium are not subject to runaway self-sputtering, but suffer from high light ion erosion rates and very nonuniform redeposition. It has been suggested that strongly segregating alloys such as Cu-Li might be used to provide a low-Z self-sustaining coating while maintaining the desirable redeposition, thermal and mechanical properties of the majority alloy component.High flux deuterium plasma sputtering and ion beam experiments have been performed on Cu-Li alloys to determine if the reduction in copper erosion previously predicted and observed in low flux ion beam experiments occurs at particle fluxes representative of an RFP first wall or tokamak limiter. Partial sputtering yields of the copper and lithium components have been measured as a function of alloy composition and sample temperature using optical plasma emission spectroscopy, weight loss and catcher foil techniques. It is found that the lithium sputtering yield increases with increasing sample temperature while the copper yield decreases by as much as two orders of magnitude. The temperature required to obtain the reduction in copper erosion is found to be a function of bulk lithium concentration. Consequences of these experimental results for anticipated erosion/redeposition properties are calculated, and the Cu-Li alloy is found to compare favorably with conventional low-Z materials.     

Nuclear-grade zirconium prepared by combining combustion synthesis with molten-salt electrorefining technique

Zirconium has a low absorption cross-section for neutrons, which makes it an ideal material for use in nuclear reactor applications. However, hafnium typically contained in zirconium causes it to be far less useful for nuclear reactor materials because of its high neutron-absorbing properties. In the present study, a novel effective method has been developed for the production of hafnium-free zirconium. The process includes two main stages: magnesio-thermic reduction of ZrSiO₄ under a combustion mode, to produce zirconium silicide (ZrSi), and recovery of hafnium-free zirconium by molten-salt electrorefining. It was found that, depending on the electrorefining procedure, it is possible to produce zirconium powder with a low hafnium content: 70 ppm, determined by ICP-AES analysis.     

Theoretical analysis on the effect of liquid droplet geometry on contact angle

This paper is concerned with the development of a first-principle theoretical method to explain the dependence of contact angle on the size of liquid droplets on smooth solid substrates. It has been shown that the contact angle for axisymmetric droplets is size-dependent and, consequently, cannot satisfy the original Young equation. However, this contact angle can be theoretically deduced for any droplet material and mass as a function of the asymptotic contact angle (the limiting value of the contact angle as droplet size decreases). The proposed approach is based on the fact that the two major forces acting on a droplet, that is, the surface force and the gravity force, are independent of each other. It has been demonstrated that for sessile droplets on smooth surfaces, the contact angle can be uniquely determined for given droplet mass (or volume) and liquid/solid/gas properties.     

辐射交联聚合物的结晶动力学(英文)

电离辐射在工业上应用的基础是聚合物的辐射交联,它们是绝缘电线和电缆的交联,热收缩性材料的生产,泡沫塑料等等。辐射引发交联已经被广泛地研究,特别是凝胶的形成和聚合物结构、辐照条件对交联度的影响。对于一般法和辐射法交联的聚合物却很少有人研究它的结晶过程。例如,已经证明除了在非常高的吸收剂量外,辐照的聚乙烯中总的结晶度不受影响,但对于聚丙烯和聚丁烯在凝胶点剂量时,它们的结晶度大大减少。辐照聚合物的重新熔融,进一步减少了总结晶度。 本工作表明不仅总的结晶度而且结晶动力学也受辐射引发交联的影响。结晶速率指出结晶划分成二种不同增长机理的过程。冷却速率是一个重要的因素,它决定结晶过程并影响与交联的半晶聚合物的结晶度和形态有关的其它性质。     

Simplified soil-structure interaction analysis with strain dependent soil properties

Recent work regarding the response of above-ground soil structures, such as dams, has indicated the need to use strain dependent soil properties. Unlike other building materials soil stiffness and damping properties are highly strain dependent. The application of these concepts to problems in soil-structure interaction has also been suggested. Without commenting on the appropriateness of this extension to soil-structure interaction problems, it is suggested that answers similar to those given by the strain dependent solution of finite element models can be obtained more simply by the use of lumped-parameter impedance functions. To establish this equivalence, it is imperative that all other variables in the problem be made equal for both models; that is, the strain dependency problem must be isolated if the comparison of the two approaches is to be meaningful. The proposed method uses a damping value equal to the average strain dependent soil profile damping. The strain dependent soil profile damping values are obtained by the use of a much simpler model using one-dimensional wave propagation theory. From this same one-dimensional model, the strain dependent soil stiffness corresponding to the average top layer of soil with and without an overburden to approximate the superstructure is used in the equivalent simplified model. Several case comparisons indicate the validity of the proposed method.     

Analysis of piping with hysteretic supports using response spectra

This paper introduces a response spectra-based method for analyzing piping with hysteretic nonlinear supports. The method is developed to be as simple and versatile as possible, yet accurate enough to model the essential nonlinear behavior of the supports. The required data is the hysteresis loops of the supports, the linear properties of the piping, and the linear acceleration response spectra. The supports are modeled by equivalent linear stiffness and damping, and the combined piping/support system is analyzed using complex modal properties that account for high-damping effects. The final peak response is obtained by a mode combination rule which is a new generalization of Complete Quadrature Combination (CQC) that accounts for nonlinear properties and complex modes. Sensitivities that indicate the degree of nonlinear behavior and support interaction are also determined. The method is used to analyze two three-dimensional piping systems with multiple nonlinear supports, which have been tested on a shaking table. Comparisons between experimental and analytical results show good agreement.     

ICRH ITER-like antenna tested on TS commissioning,electrical modeling and load resilience studies

A prototype of ICRF antenna based on the load-resilient electrical layout anticipated for ITER has been built at CEA-Cadarache. It consists of two toroidally adjacent resonant double loops (RDLs) based on the conjugate-T concept proposed for the ITER ICRF array. This prototype has been recently validated in Tore Supra plasmas exhibiting fast density perturbations in front of the antenna. This paper reports on the load resilience properties of the antenna prototype, as well as the RF modeling and the commissioning. Significant effort on modeling, coupled to an extensive low power campaign, has allowed characterization of the antenna in both vacuum and plasma loading conditions. Plasma load modelings computed with the code TOPICA – very helpful to set up the matching points on plasmas – are found to be in good agreement with the experimental results. The main studies focus on load resilience properties have been carried out in L-mode plasmas. Supersonic molecular beam injection (SMBI), able to launch a series of very short/dense gas jets at Mach number up to 5, was used to mimic the sudden increases of the antenna coupling provoked by ELMs. The results are found to be in good agreement with RF circuit calculations that include 3D modeling.     

0Cr18Ni10Ti管道钢的概率机械性能

完成了反应堆管道新材料0Crl8Nil0Ti的概率机械性能试验研究。拓展赵等提出的确定有限疲劳可靠性数据良好假设分布的统一方法到本文机械性能数据分析。结果表明．数据具有明显正偏性，常见正态分布描述不适于该套数据。综合考虑各分布的拟合优度、与失效机制的一致性和尾部预测的安全性．数据的良好统计分布是对数正态分布和极大值分布。从统计分析的方便性角度。提出了给定可靠度和置信度下基于对数正态分布的机械性能参数估计方法。并有效地估计了材料的概率机械性能参数。     

Simulation of the thermomechanical effects originated on a fuel pin with a cracked pellet by different power ramp velocities, using a two dimensional finite element model

Thermomechanical effects originated on a fuel pin with a cracked pellet by different power ramp velocities has been studied. To such purpose, the response of a simplified two dimensional finite element model including viscoelastic properties on the pellet and elastoplastic properties on the clad was investigated, under the influence of various ramps with durations ranging from 0 s (instantaneous ramp) to 200 s (slow ramp).The importance of both, the viscoelastic relaxation effects and their interaction with the plastic behaviour of the clad was put in evidence. It has been observed, that the mechanical response of this fuel pin model strongly depends on the ramp's duration.     

Thermoluminescence properties of nanocrystalline K2Ca2(SO4)3:Eu irradiated with gamma rays and proton beam

Thermoluminescence properties of nanocrystalline K₂Ca₂(SO₄)₃:Eu prepared by ball milling technique have been studied and the nanophosphor’s suitability as an effective gamma radiation and proton beam dosimeter material has been examined. It is found that the nanophosphor is suitable for dosimetry over a very wide range of doses ∼1 Gy to 1 kGy for gamma radiation. And for proton beam the same nanophosphor shows a more or less linear response for the dose range 0.1-100 Gy. A comparative study of this nanophosphor with its corresponding microcrystalline form (prepared by solid-state diffusion method) as well as the nanocrystalline form prepared by (the more conventional) co-precipitation technique has shown that the nanophosphor prepared by the ball milling technique is in almost all respects better than the other two forms reported earlier.     

Application of first and second order reliability methods in the safety assessment of cracked steam generator tubing

The First- and Second Order Reliability Methods (FORM and SORM) have been applied in the safety assessment of steam generator tubes with through-wall axial stress corrosion cracks. The underlying probabilistic fracture mechanics model takes into account the scatter in tube geometry, material properties and stable crack propagation. Also, the effect of the maintenance strategy has been considered. A realistic numerical example has been given to compare the failure probabilities calculated by FORM and SORM to those obtained by different versions of Monte Carlo simulations. The relative errors of the numerical methods employed have been analysed, which has shown that FORM performs in an acceptable and SORM in an excellent manner. Some changes in failure surface properties, caused by different maintenance strategies, are indicated and a sensitivity analysis of influencing parameters is made. The results obtained demonstrate the applicability of FORM and SORM in the safety assessment of stress corrosion cracked steam generator tubing.     

利用同步辐射进行氟塑料的表面改性与微器件制造研究

It is well-known that fluorinated polymers are very unique polymer materials because of their distinguished properties, such as high electrical resistivities, chemical and thermal stabilities, bio-compatibilities, etc. However,polytetrafluoroethylene (PTFE) is degraded by ionizing radiation with a low dose through main chain scission, and the mechanical properties are seriously deteriorated. In early 1990's, it was found that irradiation for PTFE at elevating temperature enhances recombination of radicals induced by ionizing radiation. Thus, crosslinked PTFE had been obtained[1,2]. The crosslinked PTFE shows remarkable improvements for the radiation durability and mechanical properties, etc.We have performed micro-fabrication by means of synchrotron radiation (SR) for various kinds of PTFEs including crosslinked PTFEs. The direct photo--etching technique using SR is known as TIEGA() technology,which has been developed by Sumitomo Heavy Industries, Ltd. The technology was applied for the micro-fabrication of fluorinated polymers. It has been found that etching rates obtained for crosslinked PTFEs were much larger than those of the non-crosslinked. The fact is strange from the viewpoint of radiation durability of crosslinked PTFEs. Hence, the results are not described by simple consideration such as the G-values of main chain scission. We have proposed that the etching rates should be controlled by the complex mechanism through at least two different steps as polymer decomposition and fragment desorption mechanisms.On the other hand, we have found that abnormal reactions were induced at the surface region under the SR etching for the various kinds of fluorinated polymers. Through the measurements using differential scanning calorimetory (DSC) and solid state 19F-NMR, we have confirmed crosslinking reactions for the polymers even in solid states. This reaction should be induced by the very high density radicals formation and their recombination in very localized area of the polymers under the SR etching processes.     

The Influence of Silicon Surface Defects on MOS Radiation-Sensitivity

The relationships of the electrical properties of irradiated MOS structures to processed-induced surface defects have been investigated. It has been found that the radiation-induced perturbations in oxide space-charge and interface states relate directly to the density of oxidation-induced stacking faults and edge dislocations. The density of such surface defects depends on both the structural properties of the starting silicon and the fabrication procedures. Oxidation-induced stacking faults are strongly related to the oxidation conditions, such as temperature, time, and ambiance. High-frequency CV, quasi-static CV, and ac conductance techniques were used to determine the interface state densities and flat-band voltage distributions. It has been found that, in addition to interface states, exposure to ionizing radiation causes gross non-uniformities in trapped positive space-charge. Using secondary ion mass spectrometry (SIMS) on an MOS sample possessing a high density of stacking faults, it has been shown that positive charge-species drift to the SiO2/Si interface and form clusters in a random fashion similar to that of the defects delineated by differential etching. Based on the known relationship of surface generation lifetime on surface defects pre-irradiation lifetime has been demonstrated as an effective electrical parameter for the prediction of the total-dose radiation sensitivity of MOS devices.     

Design Assessment for Transport and Storage Casks

Abstract

The design assessment concerning the mechanical behaviour of transport and storage casks for radioactive material to fulfil nuclear safety criteria has to be based on two essential considerations: (1) Effective analysis of the stress–strain state of the cask components under both normal operational and test conditions including hypothetical accident scenarios with suitable accepted methods. (2) Economic estimation of the required properties and the structural state of the cask components with sufficient exactness. In an overview of the codes which are available at GNS/GNB for cask impact strength analyses (ANSYS, ADINA, VDI Codes), procedures and aspects of benchmarking and validation of calculation codes are described. The results of experimental full size cask drop test programs (CASTOR, POLLUX) and corresponding pre-test calculational analyses show the suitability of the codes used. The influence of dynamic effects on the mechanical properties of material (ductile cast iron, wood) has been investigated experimentally. By consideration of these dynamic values in strength analyses of casks at impact a good agreement between experimental and calculational results has been achieved.     

Remote-LIBS characterization of ITER-like plasma facing materials

The occurrence of several plasma-wall interaction processes, eventually affecting the overall system performances, is expected in a working fusion device chamber. Monitoring the changes in the composition of the plasma facing component (PFC) surface layer, as a result of erosion and redeposition mechanisms, can provide useful information on the possible plasma pollution and fuel retention. To this aim, suitable diagnostic techniques able to perform depth profiling analysis of the superficial layers on the PFCs have been developed. Due to the constraints commonly found in fusion devices, the measuring apparatus must be non invasive, remote and sensitive to light elements. These requirements make LIBS (Laser Induced Breakdown Spectroscopy) an ideal candidate for on-line monitoring the walls of current and of next generation (as ITER) fusion devices. LIBS is a well established tool for qualitative, semi-quantitative and quantitative analysis of surfaces, with micro-destructive characteristics and some capabilities for stratigraphy.In this work, LIBS depth profiling capability has been verified for the determination of the composition of multilayer structures simulating plasma facing components covered with deposited impurity layers. A new experimental setup has been designed and realized in order to optimize the characteristics of a LIBS system working in vacuum conditions and remotely, two noticeable properties for an ITER-relevant diagnostics.A quantitative analysis has been carried out in determining the elemental composition of the ITER-like samples.