Search

Tests of pressurized solar radiation absorbers require suitable pressure vessels and window structures for the penetrating light in order to heat up pressurized gases or gases other than air [1]. A...

Einleitung: Die EvaluateTM-Studie (Evaluation of therapy management and patient compliance in postmenopausal hormone receptor positive breast cancer patients receiving letrozole treatment) ist eine prospektive, nicht interventionelle Studie, die das Therapiemanagement und die Compliance im Rahmen der Routineversorgung unter einer Therapie mit Letrozol bei postmenopausalen Patientinnen mit einem invasiven, hormonrezeptorpositiven Mammakarzinom als Studienziel hatte. In dieser Publikation werden die Parameter bei Studieneinschluss berichtet. Material und Methoden: Von Januar 2008 bis Dezember 2009 wurden insges. 5045 Patientinnen in 310 Prufzentren in die EvaluateTM-Studie eingeschlossen. Zugelassen waren Patientinnen mit einem hormonrezeptorpositiven Mammakarzinom in der adjuvanten und metastasierten Therapiesituation. 373 Patientinnen mussten aus unterschiedlichen Grunden aus den Analysen ausgeschlossen werden. Ergebnisse: Insgesamt wurden 4420 Patientinnen in der adjuvanten und 252 Patientinnen in der palliativen (metastasierten) Situation in die Studie eingeschlossen. Bei 4181 Patientinnen in der adjuvanten Situation wurde direkt nach operativer Therapie mit einer Aromataseinhibitortherapie mit Letrozol begonnen (upfront). Bei 200 Patientinnen wurde zunachst Tamoxifen gegeben und in den Jahren 2 – 5 nach Diagnosestellung mit der Aromatasehemmertherapie mit Letrozol begonnen (switch), und bei 39 Patientinnen erst 6 – 10 Jahren nach Diagnosestellung (extended endocrine therapy). Die Patientinnen- und Tumorcharakteristika lagen ebenso wie die Begleiterkrankungen und die Begleitmedikation im Bereich des Erwarteten. Schlussfolgerung: Die Daten der EvaluateTM-Studie werden einen guten Einblick in das Therapiemanagement von postmenopausalen Patientinnen mit einem hormonrezeptorpositiven Mammakarzinom im Rahmen der Routineversorgung geben. Geplante Analysen beinhalten die Therapiepersistenz und die Zufriedenheit mit den Informationsstrukturen und dem Aufklarungsinhalt.

In electric machines due to high currents and resistive losses (joule heating) heat is produced. To avoid damages by overheating the design of effective cooling systems is required. Therefore the knowledge of heat sources and heat transfer processes is necessary. The purpose of this paper is to illustrate a good and effective calculation method for the temperature analysis based on homogenization techniques. These methods have been applied for the stator windings in a slot of an electric machine consisting of copper wires and resin. The key quantity here is an effective thermal conductivity, which characterizes the heterogeneous wire resin-arrangement inside the stator slot. To illustrate the applicability of the method, the analysis of a simplified, homogenized model is compared with the detailed analysis of temperature behavior inside a slot of an electric machine according to the heat generation. We considered here only the stationary situation. The achieved numerical results are accurate and show that the applied homogenization technique works in practice. Finally the results of simulations for the two cases, the original model of the slot and the homogenized model chosen for the slot (unit cell), are compared to experimental results.

Gas turbine blades are protected against high-temperature oxidation and gas corrosion by suitable coatings. The coatings are mainly strain-controlled by the covered blade material. The estimation of the blade and coating stresses can be performed using the Finite Element Method, which however may be expensive because of the inelastic behaviour and the need to use fine FE meshes. Under some circumstances, a two-step procedure can be used for the calculations of the blade stresses and of the coating stresses. Using this procedure, it is possible to neglect the coating in the numerical structural analysis and to evaluate the stress distributions in the coating in subsequent analytical computations. The calculation methods is presented and discussed.

The structural lifetime of a brazed joint is affected by the plastic behavior of ductile filler metal. In this work, elastoplastic analysis is performed on a CFC/Cu/TZM bonded joint for different thermal loading cases. The evolution of strains in the braze layer during the brazing process is analyzed. It is shown that the temperature dependence of the flow curves exerts considerable influence on the deformation behavior of the filler metal interlayer. The deformation characteristics of the braze layer under thermal cycling are investigated. The effect of thermal gradient on the plastic deformation of the braze is discussed. The fatigue lifetime of the copper braze layer is estimated. High heat flux (HHF) cycling tests are conducted on a CFC/Cu/TZM brazed joint in an electron beam facility. The microstructure of the deformed copper braze is presented. The flow morphologies and corresponding slip mechanisms are discussed.

For components subjected to strong mechanical and cyclically thermal loads, proof of a limitation of permanent strain is of great significance due to the danger of deformation progressing from cycle to cycle (ratcheting). Within the framework of investigations concerning the load situation of the first wall of a fusion reactor, experimental and theoretical studies on ratcheting were carried out. Progressive deflections were identified under suitable conditions on internally cooled beam-shaped components subjected to cyclic heating and a bending load. A simple beam model can be used for systematic theoretical analysis in this case. Its treatment leads to the development of so-called Bree diagrams with which the structural behaviour can be characterized as a function of the applied primary and secondary stresses. The peculiarities arising under predominant bending loads will be discussed.

Transient heat loads on a millisecond timescale with deposited energy densities beyond 1 MJ m −2 have been simulated in a plasma accelerator facility (VIKA) and in two high power electron beam teststands (JUDITH, JEBIS). Main objective of these experiments was to study and to compare the behaviour of different plasma facing materials (Be, CFC, W) under heat loads which occur during disruptions in future thermonuclear fusion reactors such as ITER. In these tests special attention was paid to the thermal shock resistance, the processes during melt layer formation, and the resulting material erosion. To perform these tests specific loading techniques and diagnostics have been developed and applied. Among these are high heat flux loading experiments at elevated temperatures ( T > DBTT ) of the test coupons, fast surface pyrometry, and reliable techniques for the quantification of the absorbed energy.

Progressive deformations due to the combination of a cyclic nonlinear temperature distribution and electromechanical loadings may pose a serious problem for the design in advanced tokamacs. For first wall mock-uṕs exposed to a surface heat flux of 0.5 MW/m 2 and a load controlled mechanical bending moment experimental and theoretical analysis was carried out under different cycle conditions. A simplified beam model was developed for the investigation of the thermomechanical behaviour. The special features of ratcheting under bending conditions are discussed.

To assess the lifetime and the long term heat removal capabilities of plasma facing components in future thermonuclear fusion reactors, neutron irradiation and subsequent high heat flux (HHF) tests will be of great importance. The effect of neutron damage will be simulated in material test reactors. To investigate the behaviour of components subjected to heat loads during normal and off-normal conditions, a 60 kW electron beam teststand (Julich Divertor Test Facility in Hot Cells (JUDITH)) has been installed in a hot cell which can be operated by remote handling techniques. In this facility inertially cooled test coupons can be handled as well as small actively cooled mock-ups. The irradiation of complete divertor modules however requires greater efforts. To investigate specific problems such as neutron induced changes in the performance of the braze interface, small test coupons without active cooling capabilities may be suitable. ITER relevant temperature gradients and resulting stress fields can be established during transient heating by electron beam methods. The only reasonable alternatives to this procedure are actively cooled test specimens or small divertor modules. A special clamping mechanism for test samples with an integrated coolant channel has been developed and tested. This experimental procedure is an attractive and cost effective alternative comparing large scale tests on complete divertor modules.

In order to study the boundary conditions for the occurrence of ratcheting, a testing rig was erected. In this rig, small-scale mock-ups of the first wall were tested under mechanical conditions similar to those expected during disruptions. These mock-ups were made of stainless steel AISI 316. They were heated on the surface and water cooled from inside. Disruption forces were simulated by a high-speed hydraulic bending system by impact loads. The mock-ups were heated by a high-frequency generator and cooled by water through two cooling channels. In addition to the experimental work, simplified analytical analysis and numerical calculations were carried out using the finite element program abaques . In these calculations, the temperature and stress fields in the mock-ups were investigated and the influence of the different constitutive equations was studied. The experimental results confirm the ratcheting behaviour predicted by the calculations. It has been demonstrated that the ratcheting behaviour for constant mechanical and cyclic thermal loads is much stronger than in the case when both loads are cyclic in nature.

The superposition of load-controlled stresses and cyclic thermal stresses at very high temperatures can produce remarkably enhanced creep deformations (creep ratcheting). During an experimental project thick-walled tubes made from ALLOY 800 were loaded by an axial force at temperatures around 900°C. The inductive heating facility was cyclically operated in such a manner that in the tube walls temperature differences of 40°C occurred. Thermal stresses were so induced. The axial elongation was measured. For comparison at the same specimen the elongation was also measured under constant temperatures (at the mean temperature of the cycle). Under cyclic conditions a larger elongation rate was observed. The ratcheting effect was clearly seen. Inelastic stress analysis using simple constitutive creep equations predicted a lower effect.

During the operation of ITER a temperature difference in the range of some 100°C occurs between the heat-loaded outer surface and the wall of the cooling channels. Due to this inhomogeneous temperature field secondary stresses are produced. In addition high electromagnetic forces can occur caused by disruptions or vertical plasma movements. The resulting stresses may lie beyond the yield stress of the structural material. From the interaction of thermal and mechanical forces, a complex stress state is achieved which may lead to premature failure or to progressive plastic deformations (ratchetting). In the present paper the conditions for the occurrence of ratchetting are studied using simplified models of the first wall. For the experimental study of ratchetting phenomena an testing rig has been erected. In this rig, bending forces can be achieved on first-wall mockups with rise times of ∼ 30 ms combined with cyclic temperature gradients.

Two different designs of single-tube metallic heat sinks with carbon armour tiles, designed by the Next European Torus (NET) team and manufactured by Metallwerk Plansee, were tested under thermal loading conditions simulating the normal operation parameters expected for the NET/ITER (International Thermonuclear Experimental Reactor) divertor. The experiments were performed in the Material Research Ion Beam Facility (MARION) and the Julich Divertor Test Facility/Hot Cells (JUDITH), both at the Research Centre Julich, and in the JAERI Electron Beam Irradiation Stand (JEBIS) at the Japan Atomic Energy Research Institute. The thermal response of the components was determined by stepwise increase of the heat flux, and the thermal fatigue behaviour was studied by cyclic loading at different heat flux levels. Additionall, finite elements analysis of the temperature and stress fields resulting from thermal loading was performed. No failure of the brazes resulted from exposing the component to a peak heat flux of 20·7 MW/m2 in the screening test. In the thermal fatigue experiments, 300 cycles at 15 MW/m2 were sustained in JEBIS, whereas in MARION, failure occurred after 376 cycles at 10 MW/m2 surface heat flux. The results of the numerical analysis showed good agreement with the values measured in the experiments.

The results of the German research and development project ‘HTR Design Criteria’ has been presented during the workshop on ‘Structural Design Criteria for HTR’. The work is organized in four areas: (1) technical safety boundary conditions, (2) metallic structural components, (3) prestressed concrete pressure vessel, and (4) graphitic structural components. In this summary report some essentials are discussed for all four areas. On basis of these results, the formulation of structural design (KTA) rules are in preparation.

High temperature component design is very important in different industrial fields. This paper discusses work done in Germany on the design of metallic components for the Helium Cooled High Temperature Reactor. Candidate materials for application at the different temperature regions are presented. Criteria are developed to specify the allowable strength values of the materials (S m , S t ) for use in design codes. The following typical relevant phenomena are treated and discussed: • —creep under uniaxial and multiaxial conditions up to temperatures of 1000° C; • —creep fatigue interaction, where holding times during the stress strain cycles have a great influence on the life time; • —creep buckling for pressure loaded shells with initial imperfections; • —creep ratcheting as a phenomenon, where cyclic secondary stresses produce enhanced deformations; • —fracture mechanics at high temperatures with the aspects of creep crack growth and fatigue crack growth.

The calculation of temperature distributions for systems exchanging radiation heat requires as a first step the determination of the heat fluxes caused by radiation at its surfaces. The functional of the variational principle is the starting point of a numerical solution method. By using finite element procedures a system of linear equations is derived, which supplies an approximation of the radiosity. Having the radiosity, the heat flux at the surfaces, which governs the boundary condition for the temperature distribution in the structure, can be calculated. A method of determining the view-factors using the concept of the finite element method is also given.

To evaluate the performance of divertor modules for ITER under repeated quasi-stationary heat loads of typically 5 MWm−2, high heat flux tests have been performed in the electron beam test facility JUDITH. Main objective of these experiments was the quantification of the heat removal efficiency and the thermal fatigue behavior under cyclic heat loads of modules with a selection of different plasma facing materials which are considered as prime candidates for HHF components in ITER. Miniaturized divertor modules with geometries also suitable for neutron irradiation experiments have been investigated in high heat flux electron beam experiments. The plasma facing materials investigated so far are different beryllium grades and carbon fiber composites (SEPCARB N31 and DUNLOP Concept 1). The beryllium modules are of the flat tile type with a copper heat sink (CuCrZr). Different joining techniques using INCUSIL and silver free brazes have been included in the test matrix. The CFC modules are primarily of the monoblock type with coolant tubes made of CuCrZr or DS-copper.

Plasma accelerators are proposed for disruption simulation experiments on plasma facing materials. In this work the VIKA-93 hydrogen plasma gun of the Efremov Institute was used, to provide the plasma disruption scenarios with the pulse length of a shot up to 360 μs and the incident energy during a pulse up to 30 MJ/m2. Experiments were carried out on tungsten specimens of size 25mm×25mm×10mm. To investigate the influence of ductile-to-brittle transition temperature (DBTT) on tungsten behaviour under disruption the specimens were preheated from RT up to more then 1000°C. Dependent on the specimen temperature and the loading parameters different phenomena were observed. At the energy of 7.5 MJ/m2 in case of a preheating temperature of the specimen below DBTT a the number of grain boundary macro cracks was found beside a network of fine surface cracks. For specimen temperatures above the DBTT at the same loading conditions only the fine surface cracks were observed. At the energy of 30 MJ/m2 remarkable surface melting and a wavy surface morphology was observed for all specimens at temperatures from RT to 1000°C.

A divertor component of a fusion reactor experiences cyclic thermal loads. This situation was simulated by means of high power electron beam irradiation on brazed CFC/TZM passively cooled specimens. Microstructural investigations and numerical stress analyses were performed. The results are compared with those of furnace heating test.

For the divertor of NET/ITER the development of actively cooled components which are able to withstand the high heat loads during normal operation is one of the key issues. TZM heat sinks with CFC armour tiles brazed to the plasma facing side and a Mo41Re cooling tube may provide a solution for such high heat flux components. Manufacturing of the mock-ups is performed in two main steps: in the first step the CFC tiles, 26 × 44.5 × 9 mm3, are brazed to a 2 mm thick “interlayer” of TZM by use of a Zr braze. Subsequently these CFC/TZM units are brazed to the TZM heat sink by means of a CuPd alloy with a lower melting temperature than the Zr braze. The interlayer serves to reduce bending of the component due to different thermal expansion of the CFC and TZM during the brazing procedure and could possibly also enable remote controlled in-situ repair of damaged tiles in the confining vessel. The cooling tube of Mo41Re, bonded to the TZM heat sink by hot isostatic pressing (HIPing), contains a stainless steel twisted tape insert to enhance heat transfer into the water resulting in higher critical heat flux of the component. Thermal loading was carried out in the JAERI electron beam irradiation stand (JEBIS) at the Japan Atomic Energy Research Institute (JAERI). For the experiments the beam dimensions were chosen to be 5 × 15 cm2full width at half maximum. By stepwise increase of the power density at constant pulse lengths of 35 s the thermal response as well as the maximum tolerable heat load of the component were determined. The thermal fatigue behaviour was investigated by thermal cycling at 12 and 15 MW/m2power density. No change in thermal response was observed after 1000 cycles at 12 MW/m2and 300 cycles at 15 MW/m2surface heat flux, respectively.

In heat exchanging components amongst the primary stresses even thermally induced secondary stresses must be taken into account. Here fluctuating temperatures (e.g. hot streaks) are especially important. At very high temperatures above 800'C a superposition of primary stresses and thermally induced fluctuating secondary stresses may lead to enhanced creep (creep ratcheting). At temperatures of 950°C experiments were carried out to verify the creep ratcheting effect. Here INCOLOY 800 H tubes were loaded by an axial force and by cyclically changing temperatures. A creep ratcheting effect could be shown. Calculations were carried out by using a simple two-shell-model code and finite-element programme, respectively. It could be shown that the results obtained with the two-shell model are very conservative, while the results of the finite element analysis were in a good agreement with the experiments. Finally it is discussed, how the two shell model can be improved.

Differential and absolute cross sections for the coherent reaction $^{40}\mathrm{Ca}$(\ensuremath{\gamma},${\ensuremath{\pi}}^{0}$${)}^{40}$Ca g.s., as well as for the incoherent reaction $^{40}\mathrm{Ca}$(\ensuremath{\gamma},${\mathrm{\ensuremath{\pi}}}^{0}$${)}^{40}$Ca(g.s.), have been measured with monochromatic photons in the threshold region (${E}_{\ensuremath{\gamma}}$=157--169 MeV). The differential cross section for the coherent process exhibits a diffraction minimum due to the nuclear mass form factor while the incoherent cross section is rather structureless. The cross sections are in good agreement with recent distorted-wave impulse-approximation calculations.

Absolute cross sections and angular distributions for the production of neutral pions from 12 C by monochromatic photons have been measured near threshold. The contribution of incoherent pion production is found to be less than 10% for E γ ⩽168 MeV. Both the absolute cross section and the angular distribution indicate that a quantitative analysis requires final-state interactions of the produced π 0 with the surrounding nucleons to be taken into account.

The Helium-Cooled High Temperature Reactor (HTR) can supply process heat for methane reforming at temperatures of nearly 1000°C. As is the usual requirement for equipment used in a nuclear plant, the process heat exchangers must operate with a high reliability. This implies both that the exchanger tubes must be made from alloys which are very resistant to high temperatures and that the operational pressures are adjusted so that primary stresses in the tube walls are small. However, secondary stresses—an order of magnitude larger than primary stresses—are produced by the temperature profile through the wall. With consideration of creep, the time-dependent stress-strain distributions in the tube walls were calculated using the Finite Element Programme ASKA. The creep damage was estimated using Robinson's rule. The results showed that operation was possible for 100 000 h. Under accident conditions, load-controlled stresses in the tube walls may be an order of magnitude larger than under normal operation conditions. Here the stress distribution near the tube closure was investigated and it was found that lower stresses occurred in the transition and closure region than in the undisturbed tube area. In this way it could be shown that the closure is not seriously put at risk.

The metallic components of a high-temperature reactor with operating temperatures above 880°C have to be ensured against the, in comparison to primary stresses, respectively higher secondary stresses due to loading transients. For the calculation of the damage accumulation due to primary, secondary and peak stresses, elastic methods are used in the temperature region up to 800°C. These elastic methods are too conservative at temperatures above 900°C. Therefore a simplified inelastic method is shown for calculation of the creep damage of a reformer tube with operating temperatures at about 900°C under start-up and shut-down loadings. With this method a design is possible for the calculated start-up and shut-down transients during the lifetime of the component.

The postulated secondary-side depressurization accident in an HTR plant raises the question of whether creep buckling can occur under external pressure in the tubes of the heat exchangers whose cross sections may be slightly eccentric due to manufactural tolerances. Experimental and theoretical investigations were carried out on the problem of creep buckling. Within the scope of these experiments, tubes made of NiCr 22 Co 12 Mo with different adjusted initial ovalities were exposed to pressures of 35–45 bar at 950°C. The buckling times were measured. Theoretical analyses were carried out using a model conceived by Hoff as well as the Finite Element Method, allowing for the scattering of relevant test parameters. Both methods of computation are suitable for investigating the phenomenon of creep buckling. It was found that the calculated buckling times are affected by great uncertainties taking into account the scatter of influential test parameters. In connection with the accidental stressing in an HTR plant it was confirmed that creep buckling is not a problem of high safety-related relevance.

Photons from the reaction {sup 16}O+{sup nat}W have been measured using the Darmstadt-Heidelberg crystal ball. The source velocity for photons above 25 MeV deduced from the angular distribution identifies the nucleon-nucleon system as the emitting system consistent with proton-neutron bremsstrahlung. This observation is supported by a comparison of the experimental angle-integrated spectra with statistical model calculations, which suggest that photons below 20 MeV arise from thermal emission, whereas hard photons above 25 MeV cannot be explained by this mechanism.

In the case of hypothetical accidents, temperatures of ~2000 to 3000°C are expected in the core of a pebble-bed high temperature reactor (HTR). At such high temperatures the transport of heat by ra...

Concentrated sunlight is absorbed in solar thermal power plants by heat resistant absorbers and converted into usable heat which is transferred to a carrier medium. In solar tower power plants such as the plant in Julich porous absorbers can reach temperatures up to 1000 °C and higher. At this power plant air as heat transfer medium is sucked in through the absorber and heated up to about 700 °C. The absorber is composed of highly porous ceramic or metal wire structures. The SIJ investigates the optimization of solar absorption and the convective heat transfer to the air using thermo and fluid mechanical calculations. In such simulations the key quantities are the penetration depth of solar radiation κ and the volumetric heat transfer coefficient αv, which indicates how much energy - depending on the volume and temperature difference - is transferred by convection between solid and fluid. The attenuation of the radiation into the depth of the absorber is described generally by an exponential function with parameter κ. This is accompanied by heat transfer to the structure. Existing models of the key quantities have been validated by experimental data.

In this work the transient simulations of four hybrid solar tower power plant concepts with open-volumetric receiver technology for a location in Barstow-Daggett, USA, are presented. The open-volumetric receiver uses ambient air as heat transfer fluid and the hybridization is realized with a gas turbine. The Rankine cycle is heated by solar-heated air and/or by the gas turbine's flue gases. The plant can be operated in solar-only, hybrid parallel or combined cycle-only mode as well as in any intermediate load levels where the solar portion can vary between 0 to 100%. The simulated plant is based on the configuration of a solar-hybrid power tower project, which is in planning for a site in Northern Algeria. The meteorological data for Barstow-Daggett was taken from the software meteonorm. The solar power tower simulation tool has been developed in the simulation environment MATLAB/Simulink and is validated.

Partial-wave cross sections for fusion of $^{64}\mathrm{Zr}$ and $^{64}\mathrm{Zr}$ at energies of 5% and 7% above the Bass-model fusion barrier have been measured with the Darmstadt-Heidelberg Crystal Ball. The distribution for fusion with the more neutron-deficient target $^{92}\mathrm{Zr}$ exhausts the unitarity limit for lower angular momenta. In contrast, fusion with the slightly more neutron-rich target $^{96}\mathrm{Zr}$ yields a broad angular momentum distribution with cross sections well below unitarity even for small partial waves.