Quality Control Procedures for HTGR Fuel Element Components

The growing use of nuclear reactors for the production of electric power throughout the world, and the consequent increase in the number of nuclear fuel manufacturers, is giving enhanced importance to the consideration of quality assurance in the production of nuclear fuels. The fuel is the place, where the radioactive fission products are produced in the reactor and, therefore, the integrity of the fuel is of utmost importance. The first and most fundamental means of insuring that integrity is through the exercise of properly designed quality assurance programmes during the manufacture of the fuel and other fuel element components. The International Atomic Energy Agency therefore conducted an International Seminar on Nuclear Fuel Quality Assurance in Oslo, Norway from 24 till 28 May, 1976. The seminar was addressed to a wider audience and was, with its educational content, of interest in those countries newly entering the field as well as in those with established nuclear fuel fabrication capabilities. This KFA report contains a paper which was distributed preliminary during the seminar'and - in the second part - the text of the oral presentation. The tables and figures were presented as slides. The paper gives a summary of the procedures available in the present state for the production control of HTGR core materials and of the meaning of the particular properties for reactor operation. The work was partly sponsored by the Bundesministerium für Forschung und Technologie of the Federal Republic of Germany as well as by the Government of North-Rhine-Westfalia

Contributions for the International Carbon Conference : CARBONE 84

This report is the compilation of some papers prepared by KFA Jülich GmbH for the International Carbon Conference CARBONE 84, which will be held at Bordeaux/France. The presentations deal with objectives of manufacture as well as technical and nuclear applications of carbeneous materials

Einsatz der quantitativen Bildanalyse zur Charakterisierung von Pyrokohlenstoff

Pyrocarbon which is used as a coating material for fuel kernels in High Temperature Reactors has proved to be a very variable, but also very complex material. In order to describe it concerning its properties and operational possibilities it is necessary to apply a lot of different characterization procedures to this material. Two methods which have been developed recently are the wet and the plasma oxydation. To quantify their informations, it has become necessary to use the quantitative ceramography, in this special case the quantitative image analysis. This paper describes the equipment, the characterization parameters which are useful, and the most important errors which can arise when characterising pyrocarbon by this instrument. Finally, first experimental results are discussed

Verhalten beschichteter Kernbrennstoffteilchen unter mechanischer Druckbelastung

Bei der vorliegenden Arbeit wurde das l/erhalten von Kernbrennstoffteilchen unter mechanischer Belastung untersucht » Die Belastung der Teilchen erfolgte durch Drucktests in einem Zerdrückapparat sowie durch Einbringen von Härtemeßeindrucken in Schichten. Dabei wurde festgestellt, daß eine Rißbildung und Delamination in den Beschichtungen schon vor dem Erreichen der Berstkraft der Teilchen eintritt. Poröse Schichten verhielten sich beim Andrücken bis zur Berstkraft nicht voll elastisch. Bei den mit Methan-Pyrokohlenstoff beschichteten Teilchen erwiesen sich hohe Schichtwachstumsraten als günstig. Die Rißbildung und -ausweitung war abhängig von der Struktur bzw, Verteilung der durch Plasmaoxidation sichtbar gemachten Komponenten, Nach den Ergebnissen dieser Untersuchungwäre zu berücksichtigen, daß in Modellrechnungen nicht die Berstkraft, sondern die zur Rißbildung erforderliche Kraft eingesetzt wird

Das Tröpfchenmodell der Pyrokohlenstoffabscheidung aus der Gasphase

Based on extensive earlier work a model has been developed to describe the formation of carbon by pyrolysis of gaseous hydrocarbons. One of the central statements of this model is the assumption of the existence of a quasi liquid carbon phase duringdeposition process. This model is described and is discussed as are the consequences for the material properties and structuralparameters which arise from it. To review the droplet model, statically deposited pyrocarbon is examined by characterization methods suitable to analyse just these structural parameters. The results prove the model conceptions to be realistic

Pyrocarbon, an important material for High Temperature Gas Cooled Reactors

The presented report summarizes the present state of pyrocarbon technique, as far as its application to reactor technology is concerned. The deposition methods are described as well as the methods for characterization of the pyrocarbon deposits. Latest results of structural analysis of this material are presented. Theoretical model conceptions of pyrolysis and depostion mechanism and of microphysical processes during neutron irradiation and heat treatment of pyrocarbon coated fuel particles are described, and the experiments, which these models are based upon

Neue Vorstellungen zum Abscheidungsmechanismus von Pyrokohlenstoff

This study describes the today state of knowledge about pyrolysis reactions of gaseous hydrocarbons for coating processes and the deposition mechanism of pyrocarbon. After a discussion of previous model conceptions of these processes and the contradictions included in those ideas a new hypothesis is presented. This newconception can be characterized by the slogans "Langmuirzone", "Pyroaggregates", and "Carbon Droplets". The new ideas are discussed in detail, and results of approximate experiments are presented

Methoden zur Charakterisierung von pyrolytisch abgeschiedenem Kohlenstoff: im Institut für Reaktorwerkstoff angewandte Charakterisierungsmethoden

Pyrocarbon is deposited as a coating material of fuel kernels used in High Temperature Gas Cooled Reactors. For the development of particle coatings specified for the various reactor designs it is necessary to know about the properties of pyrocarbon and their changes by neutron irradiation. In this report procedures are described which are used in the Institut für Reaktorwerkstoffe to characterize pyrocarbon. These procedures are: measurement of geometry, density, microporosity, apparent crystallite size, anisotropy of orientation, modulus of elasticity and strength of coatings, as well as ceramography, etching by oxydation, secondary and transmission electron microscopy

Contribution to the development of reactor graphites and pyrocarbons - irradiation behaviour, model conceptions and characterization

The Institut für Reaktorwerkstoffe der Kernforschungsanlage Jülich has taken part in the 4th London International Carbon and Graphite Conference with four papers, one on graphite and three on pyrocarbon. These papers which are presented in this report describe and discuss some of the latest results of the investigations on graphite and pyrocarbons done in the IRW. The first contribution deals with property changes of graphite materials by fast neutron irradiation and gives interpretations based on the irradiation induced graphitization. The next two papers primarily discuss experimental work to set up new model conceptions for the deposition of pyrocarbon and for the pyrocarbon itself. The last presentation describes some modern characterization methods for pyrocarbon

Review on Characterization Methods applied to HTR-Fuel Element Components

One of the difficulties which on the whole are of no special scientific interest, but which bear a lot of technical problems for the development and production of HTR fuel elements is the proper characterization of the element and its components. Consequentlya lot of work has been done during the past years to develop characterization procedures for the fuel, the fuel kernel, the pyrocarbon for the coatings, the matrix and graphite and their components binder and filler. This paper tries to give a status report on characterization procedures which are applied to HTR fuel in. KFA and cooperating institutions