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Der 1. Teil der Versuche zum HIP-Diffusionsfugen /1/ diente der Bestimmung der geeigneten HIP Parameter für die verschiedenen Werkstoffpaarungen. Weiterhin wurde der Einfluß der Rauhigkeit der Fügeflächen auf die Verbindungsfestigkeit untersucht. Bei korrekter Wahl der HIP-Parameter ist der Einfluß der Oberflächenrauhigkeit vernachlässigbar gering /1/. Für diese Untersuchung standen LPPS versiegelte Proben zur Verfügung. Bei der Auswahl der HIP-Parameter war man, bei dem zuletzt genannten Versuch, auf einen HIP-Druck von 200 MPa beschränkt, da die HIP 11 Einheit nicht zur Verfügung stand. Um den Oberflächeneinfluß zu minimieren, ist insbesondere für die Werkstoffe, welche bei hoher Temperatur noch eine Festigkeit besitzen, ein HIP-Druck von maximal P$_{HIP}$ = 400 MPa erforderlich, Neben den schon erwähnten Werkstoffen /1/ wurden in der 2. Versuchsreihe noch zwei weitere auf ihre Diffusionsschweißbarkeit untersucht, nämlich die ODS Legierung Inconel MA 760 und die Nickelbasislegierung IN 939. Der MA 760 wird im Rahmen von COST 501/II, W.P.1 im Hinblick auf eine Anwendung für Leitschaufeln moderner Hochtemperatur-Gasturbinen untersucht /2/. Er wurde aus dem MA 6000 weiterentwickelt, wobei die Korrosionsbeständigkeit zwecks der zuvor genannten Verwendung verbessert wurde. Der IN 939 wird von der Fa. Siemens KWU in Wilhelm häufig für feingegossene Leitschaufeln eingesetzt.

The ODS materials Inconel MA754, Inconel MA6000 and Incoloy MA956 as well as the alloy Incoloy 800H were examined for their diffusion weldability using HIP techniques. Two test specimens $\varnothing$ 8 mm x 35 mm in length of the same materials as well as combinations of an ODS partner material and Incoloy 800H were joined with each other. Optimum adjustment of the HIP parameters - pressure, time and temperature - for the respective material is indispensable for good diffusion welding and was therefore aimed at during the first experimental phase. A good diffusion bond is characterized by the strength of the bonding zone. In order to determine the tensile strength, yield strength and elongation, two identical specimens (same combination under the same HIP conditions) were tested to rupture in a tensile test device at room temperature (RT) and 800°C. It was found that several specimens failed in the region of the joint. This was mainly due to the fact that the HIP pressure adjusted at 40 MPa was too low, but may also be attributed to other causes which still remain to be clarified. For example, the influence of the specimen surface condition was not known. The second experimental phase therefore served to selectively vary the roughness of the bond surface. Gastight encapsulation of the composite material in the joint is required for diffusion bonding by means of HIP. In addition to the conventional method of stainless steel encapsulation, an LPPS (Low Pressure Plasma Spray) encapsulation of the joint was also tested. This type of encapsulation is a simplified and possibly also less costly method, in particular for joining bodies of a complicated shape.

Steady state and non-steady state measurements of hydrogen permeation through metallic chromium are reported. The experimentshave been conducted by use of hydrogen and deuterium within a pressure range of 10$^{-8}$ - 1 bar and temperatures between 600 - 800 ° C. Numerical values for the physical quantities permeability, diffusion constant and solubility could be derived. At an upstream pressure above around 10$^{-3}$ bar classical Sieverts-low was found (permeation rate $\backsim$ $\sqrt{p}$) with activation energies Q$_{perm}$ - 65 kJoule/mole, Q$_{Diff}$ = 4-8 kJoule/mole, Q$_{Sol}$ = 57-61 kJoule/mole for the respective processes involved. The isotopic effect between H and D of the permeabilities could be represented by a factor of 1,5 indepent on temperature. All non steady-state measurements could be approximated reasonably well by classical diffusion kinetics. Below up-stream pressures of $\backsimeq$ 10$^{-7}$ bar the kinetics was no longer diffusion controlled, the dependence on up-stream pressure changed from $\sqrt{p}$ $\rightarrow$ p, the activatian energy for permeation increased to 127 kJoule/mole and - the isotopic factor resulted in about 2-3.

Experiments are presented investigating the action of corrosion scales on several steels against hydrogen and tritium permeation. We are interested in such model experiments to learn how to prevent tritium permeation from the primary circuit of an HTR to the secondary side. The same problem might be of some importance in later fusion reactor technology. Our corrosion scales were formed in a temperature range between 500° C and 950° C under varying steam hydrogen mixtures. Thickness of the scales was up to several ym. By adequate choice of the "process" parameters we succeeded to produce oxid scales with relativ high reduction factors for hydrogen permeation as compared with the permeation through the blank metal surfaces. Such scales also show a linear correlation between hydrogen pressure and permeation and an increased activation energy for permeation as compared to that of the blank metal. Our observations cast doubt on elder theories trying to explain the action of oxide films. We try here to apply a formalism presented first by Ash and Barrer to describe our findings. According to our experiments we believe that oxide scales formed under the conditions prevailing here act rather as a "dissociationbarrier" than as a "diffusionbarrier". We try here for the first time to describe the influence of the hydrogen permeation on the tritium permeation of the opposite side, (this is exactly the problem we normally encounter in the case of an HTR for process heat application). Our theoretical explanation shows on the one hand possibilities for producing very high reduction factors e.g. by producing oxide scales on both sides of a heat exchanger tube whereby tritium permeation may be reduced to acceptable levels in a HTR process heat plant, on the other side the models described here, give a sounder base to calculate tritium release in such plants and may be in later fusion reactor blanket configurations.

On the Occasion of the 60th birthday of Professor Dr. Rudolf Hecker, director at the Institut für Reaktorentwicklung, the staff members of the Institute arranged a discourse about current research items. On September 9, 1986, dedicated review talks were presented s` arizing the aims of the new research program of the institute. This research is mainly based upon wide earlier experience in high temperature reactor physics and technology, fusion research and spallation physics. The presentations comprised on one side talks about protective layer development and hot isostatic pressing within newly established materials research program of KFA, on the other side talks were presented about high-energy beam materials interaction dealing mainly with computer simulation of particle cascades in matter and their validation by experiments.

TEIL I: Bei der Berechnung thermischer Reaktoren ist die Diffusionsweglänge der thermischen Neutronen im Moderator eine wichtige Größe. Obwohl den Moderator im Reaktor normalerweise Kanäle zur Aufnahme der Brennelemente oder für ein Kühlmedium durchziehen, wird in der einfachen Theorie die Diffusionsweglänge für das ungestörte Moderatorsystem benutzt. Selbstverständlich bewirkt aber die Gegenwart von Kanälen, oder anders ausgedrückt, die Abwesenheit von Moderatorsubstanz, eine Vergrößerung der Diffusionsweglänge. Man kann versuchen, diesen Effekt dadurch rechnerisch zu berücksichtigen, daß man eine neue mittlere Dichte des Materials definiert, also den makroskopischen Streuquerschnitt entsprechend dem Hohlraum zu Kompaktstoff-Verhältnis reduziert. Durch eine solche "Homogenisierung" werden aber sich ergebende Anisotropieeffekte nicht berücksichtigt, die z.B. dadurch entstehen, daß längs der Achse eines zylindrischen Kühlkanals eine bevorzugte Diffusion und damit Leckage auftritt. Es sind daher frühzeitig theoretische Untersuchungen angestellt worden, wie man den Einfluß von Hohlräumen auf die Diffusion thermischer Neutronen streng berücksichtigen kann. Eine Schwierigkeit bei diesen theoretischen Berechnungen ergibt sich daraus, daß strenge Lösungen oft nur für bestimmte Geometrien möglich sind, wie z.B. für die Plattengeometrie. Aber auch die Messung der bei Anwesenheit von Hohlräumen veränderten Diffusionslänge mit Hilfe herkömmlicher Techniken ist nicht immer einfach, besonders in dem hier speziell interessierenden Fall des Kerns eines Kugelhaufenreaktors , wo die kugelförmigen Graphitelemente, die den Moderator ausmachen, in statistischer Schüttung- vorliegen. [...] TEIL II : In der Neutronendiffusionstheorie wird das zeitlich veränderliche Neutronenfeld als Überlagerung der Eigenfunktionen gegeben, die Lösungen der Helmholtzgleichung darstellen und an den Extrapolationsgrenzen verschwinden. $\triangledown^{2} \phi_{n} + B^{2}_{n} \phi_{n} = 0 (1) $ Für ein moderierendes System, in welches ein Impuls schneller Neutronen geschossen wurde und in dem die Neutronen thermisches Gleichgewicht erreicht haben, gilt folgender Ansatz: $N(t,\vec{r}) = \sum_{n} A_{n} \cdot \phi_{n}(\vec{r}) \cdot Exp(\gamma_{n} \cdot t) $(2) wobei die kleinste Abklingkonstante $\gamma_{0}$durch folgende Gleichung gegeben ist: $\vert \gamma_{0} \vert = \alpha_{0} + D_{0} \cdot B^{2}_{0} +C \cdot B^{4}_{0} + F \cdot B^{6}_{0}$ (3) Im folgenden Bericht werden Berechnungen der Diffusionsparameter ( $\alpha_{0},D_{0},C,F$ ) aus den Meßwerten eines zeitlich abklingenden Neutronenfeldes vorgenommen. Bei genäherter Darstellung der Meßwerte durch Exponentialfunktionen wurde die Methode von Willers benutzt. Bei der Untersuchung der Diffusionsparameter wurde die Methode der kleinsten Quadrate auf die Funktion $\gamma_{0}(B^{2}_{0})$ angewandt. $B^{2}_{0}$ wurde iterativ aus dem Diffusionsparameter berechnet.

This report refers to post-irradiation investigations an neutron-irradiated sintered BeO compacts. The macroscopic-mechanical properties of the samples such as density, porosity, and Young's modulus is discussed as well as the radiation damage of both composition and lattice structure. By means of a specially developed vacuum assembly, the release behaviour of helium was studied both isothermal and with a varying function of temperature and time . The detection of tritium is made by an integral method by means of a scintillation spectrometry. An absolute determination of the total contents of helium and tritium in the samples is achieved by a chemical analysis. The results of the measurements are discussed, and they are described quantitatively by the application of a modified diffusion theory .

It's a great pleasure for me to give you a heartily welcome an behalf of the German delegation. We came here to meet you and celebrate this workshop an materials in energy systems. In parallel I welcome all the participants from Egypt, excellencies, chairmen, professors, scientists, good friends from recent and Former times. 1 welcome as well all the participants of the German delegation, coming from Research Center Jülich but also from R.C. Geesthacht, from Aachen University as well as Siemens industry. The Egyptian-German cooperation in the field of material research has a long tradition of more than 30 years. (Though it is risky to talk about 30 years tradition in a country where history is counted in milleniums rather than in decades.) Neverteheless this short period of 30 years is about one generation which means that people change maintaining the cooperation. This indeed is happening and coincidently the content of the cooperation has changed from the nuclear business to nowadays nonnuclear items in energy technology. I think materials R+D is really a key point to all substantial advances in existing energy converting systems as well as for the development of really new systems. New materials and related technologies always create the basis for new processes or often even are the key problems to be solved before technological processes envisaged can be made running. Let's take the fuel cell as an example. The principle of the fuel cell has been discovered in 1839 by Sir William Grove and the famous solid electrolyte which until today is doped zirconia has been discovered in 1899. Nevertheless it took another century to make a solid oxide fuel cell ready for the beginning of a market penetration phase where we are faced with nowadays. And this has been made possible by intensive work on materials and material technology R+D. So in my view we are completely right to [...]