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

Über die Änderung der Anisotropie der kristallographischen Orientierung in Pyrokohlenstoffhüllschichten von Brennstoffteilchen durch Glühung und Neutronenbestrahlung

This study describes an optical measurement to determine the orientation anisotropy directly at the pyrocarbon coatings of fuel particles. A correlation is detected between anisotropy factors by means of optical and x-ray measurements. The optical measurement permits to detect the orientation anisotropy and its variation by annealing and neutron irradiation of the particle coatings. Also, dependencies are shown between the material properties of pyrocarbon, annealing or irradiation data,and the anisotropy increase. To explain the measured results, a model is discussed and compared with those suggested in the literature

Quantitative Modellvorstellungen zur Pyrolyse gasförmiger Kohlenwasserstoffe in Fließbetten

In fluidized beds, pyrocarbon is deposited on nuclear fuel kernels by pyrolysis of gaseous hydrocarbons. To reach a better understandingof pyrolysis and deposition mechanism, a quantitative model has been developed, basing on static deposition experiments. This model isapplied to fluidized bed processes. The typical material parameters of the deposited pyrocarbon are discussed on the basis of this nucleation - agglomeration - model of pyrocarbon formation

Keimbildung und Agglomerat-Wachstum in der Gasphase bei der statischen Pyrokohlenstoffabscheidung

Pyrocarbon coatings are deposited in fluidized beds on nuclear fuel kernels for High Temperature Reactors.In order to get a betterunderstanding of the pyrolysis and deposition process, basic investigations are carried out on this field. Because of the much more complex conditions in fluidized beds, these experiments are for the moment carried out under static conditions. In this paper, a mathematical description of nucleation and carbon atom agglomerate growth basing on experimental results is discussed. By theseprocedures it is tried to find a more accurate and precise and, in some cases modified interpretation of the so-called droplet model,which has been introduced and discussed in recent publications

Über die Entwicklung eines Matrixmaterials zur Herstellung gepresster Brennelementefür Hochtemperatur-Reaktoren

The presented report describes the development and optimization of a graphitic matrix material, which is used in the production of pressed fuel elements for the gas-cooled high-temperature reactor. Optimization is done with regard to the mechanical, thermal and reactor-physical attributes of the material. The endproduct,the standard-A3-matrix, meanwhile found a common usage because of its excellent availability and its satisfying facilities in irradiation tests . To get a technological interesting production-line, a method of manufacture, suited to the new matrix material, is described. It is the so called isostatic pressurizing, which is not only suitable for the production of sperical fuel elements but also for prismatic fuel elements