Electroplating of micro-patterned tools via replication of silicone rubber forms

A two-step replication process is described, allowing the non-destructive reproduction of micro-patterned tools. The first step comprises the embedding of the original part into silicone resin, the resin curing, and the separation of the part from the silicone rubber. The outstanding plasticity and the weak adherence of silicone rubber to most substrate materials facilitate retaining the original part. The second replication step, electroforming, requires silicone rubber metallization and contacting. The demonstrated technique is qualified mainly due to successful precautions against replication artifacts, related to silicone rubber deformability.     

Oxygen measurements in stagnant lead-bismuth eutectic using electrochemical sensors

Sensors are the major part of an active oxygen control system (OCS) to be used in ADS reactors employing lead bismuth eutectic (LBE). We tested Pt/air and Bi/Bi₂O₃ probes based on yttria-stabilized zirconia (YSZ) solid electrolytes. The sensors were calibrated by evaluating the electromotive force (EMF) - temperature dependencies in oxygen un-/saturated stagnant LBE compared to the van’t-Hoff’s isotherm. Also, probe kinetics while changing the H₂/H₂O ratio was studied. Typical, reproducible curves are presented confirming attainment of oxygen equilibrium between the fluids. The sensor outputs are deterministic, predictable. Exceptional small drifts were due to interfacial kinetics, not to the sensors behavior. Simultaneous testing of several probes in one melt was performed. The sensors seemed to be qualified for large scale use.     

Gas/liquid oxygen-transfer to flowing lead alloys

For the application of liquid lead or lead-bismuth eutectic as coolant in nuclear reactors, the concentration of dissolved oxygen, determining the compatibility with steels used as construction materials, is of critical importance. In general, oxygen has to be added continuously to the liquid metal, so as to compensate for consumption by oxide formation on the surface of the reactor components. A potential method of keeping the oxygen concentration in a favourable range is transferring oxygen from an oxygen-containing gas, which is investigated on the basis of the experience from operating a gas/liquid transfer device in the CORRIDA loop. Conclusions on oxygen transfer in industrial-scale systems are drawn.     

The influence of oral glucose intake on binding and degradation of 125I-insulin by receptors on erythrocytes as well as on insulin and C-peptide serum levels in patients after myocardial infarction and healthy individuals

In this study, we investigated the influence of glucose administration on binding and degradation of 125I-insulin by receptors on erythrocytes as well as on insulin and C-peptide serum levels in 15 patients after myocardial infarction and in 15 age-matched healthy persons. Venous blood samples were taken directly before and at 30, 60 and 120 minutes after oral administration of 75 g of glucose. In the collected blood samples serum glucose, insulin and C-peptide levels were determined. Binding and degradation of 125I-insulin by specific receptors on red blood cells were evaluated using the method described by Gambhir and modified by the authors. Serum insulin and C-peptide levels were significantly higher while binding of 125I-insulin to erythrocytes was decreased in patients after myocardial infarction. These results seem to support the hypothesis that insulin resistance and hyperinsulinism play a role in the pathogenesis of ischaemic heart disease. Impaired degradation of 125I-insulin during the oral glucose tolerance test in the patients after myocardial infarction indicates that insulin resistance is located at the receptor level.     

Alternative electro-chemically based processing routes for joining of plasma facing components

Tungsten is considered in fusion technology as functional and structural material in the area of blanket and divertor for future application in DEMO. The KIT design of a He-cooled divertor includes joints between W and W-alloys as well as of W with Eurofer-steel. The main challenges range from expansion mismatch problem for tungsten/steel joints over metallurgical reactions with brittle phase formation to crack stopping ability and excellent surface wetting. These requirements were only met partly and insufficiently in the past e.g. by direct Cu-casting of tungsten onto steel.Both, the joining needs and the observed failure scenarios of conventionally joined components initiated the development of improved joining technologies based on electro-chemical processing routes. As electrolytes aqueous and aprotic, water free, system are integrated into this development line. In the first step principle requirements are presented to guarantee a reproducible and adherent deposition of scales based on Ni and Cu acting as inter layers and filler, respectively, to generate a real metallurgical bonding as demonstrate by 1100 °C joining tests. The development field aprotic systems based on ionic liquids is discussed with respect to enable development of refractory metal based fillers with focus high temperature W–W brazing.     

Aspects of minimizing steel corrosion in liquid lead-alloys by addition of oxygen

Minimizing steel corrosion in liquid lead-alloys by addition of oxygen requires devices for efficient oxygen transfer and reliable oxygen sensors. The accuracy of electrochemical oxygen sensors is analyzed using theoretical considerations and results from experiments in stagnant lead–bismuth eutectic (LBE). Additionally, the feasibility of gas/liquid oxygen-transfer and the long-term performance of electrochemical sensors in flowing liquid metal are addressed on the basis of the operating experience of the CORRIDA loop, a facility for testing steels in flowing LBE.     

Einfluß von Eisen auf die Korrosionsbeständigkeit von Nickelbasislegierungen als mögliche Werkstoffe für SCWO-Reaktoren

Effect of iron on the corrosion behaviour of nickel based alloys for SCWO plants An experimental set up to study corrosion at high temperatures and high pressures and able to simulate the conditions of supercritical water oxidation is described. On the basis of the alloys AC 66, 45 TM, G-3 and 601 H the influence of iron on the corrosion behaviour of nickel base alloys in aqueous solution under high pressures containing oxygen and chloride is shown and discussed. The corrosion resistance of the nickel base alloys is decreased with increasing iron concentration in the whole temperature range (100 °C–420 °C). The corrosion started at lower temperatures and the weight loss increased rapidly with increasing iron content. The corrosion morphology changed from uniform corrosion for alloys with less iron content to deep pits for alloys with high iron concentrations.     

Design and corrosion study of a closed spallation target module of an accelerator-driven system (ADS)

At the Forschungszentrum Karlsruhe (FZK) the characteristics of an accelerator-driven subcritical reactor system (ADS) are critically evaluated, mainly with respect to the potential of transmutation of minor actinides and long-lived fission products, to the feasibility and to safety aspects. The work is concentrating on system design, neutronics, thermalhydraulics, safety, materials and corrosion. This article describes the FZK approach to design a closed 4 MW(th) spallation target module with a solid beam window and eutectic lead–bismuth (Pb–Bi) as spallation material and cooling fluid, which is going to be implemented in the FZK three-beam concept of an ADS. This multi-beam concept shows significant improvements towards single-beam concepts from the literature with respect to power distribution in the subcritical blanket and thermal loads of heat removal from the beam window and the spallation region. For some selected martensitic and austenitic steels, corrosion tests in static lead are performed to examine their suitability as structural or window materials. Alloying aluminum into the surface layer by high-power electron beam treatment, corrosion can be reduced to nearly zero. One prerequisite to minimize corrosion is a proper oxygen control system (OCS) via the gas-phase to set the oxygen concentration in the liquid Pb–Bi. The dynamic behaviour of this oxygen control system is described. Finally, the KArlsruhe Lead LAboratory (KALLA) is introduced, the objectives of which are technological, thermal-hydraulic and corrosion investigations into the beam window, the spallation target module and the primary system of an ADS.     

Performance of electro-plated and joined components for divertor application

A general challenge in divertor development, independently of design type and cooling medium water or helium, is the reliable and adapted joining of components. Depending on the design variants, the characteristics of the joints will be focused on functional or structural behavior to guarantee e.g. good thermal conductivity and sufficient mechanical strength. All variants will have in common that tungsten is the plasma facing material. Thus, material combinations to be joined will range from Cu base over steel to tungsten. Especially tungsten shows lacks in adapted joining due to its metallurgical behavior ranging from immiscibility over bad wetting up to brittle intermetallic phase formation. Joining assisted by electro-chemical deposition of functional and filler layers showed that encouraging progress was achieved in wetting applying nickel interlayers. Nickel proved to be a good reference material but alternative elements (e.g. Pd, Fe) may be more attractive in fusion to manufacture suitable joints.Replacing of Ni as activator element by Pd for W/W or W/steel joints was achieved and joining with Cu-filler was successfully performed. Manufactured joints were characterized applying metallurgical testing and SEM/EDX analyses demonstrating the applicability of Pd activator. First shear tests showed that the joints exhibit mechanical stability sufficient for technical application.