Method for the fabrication of block fuel elements for gas-cooled high-temperature power reactors

The method is to produce pressed block fuel elements for HTGR whose graphite matrix has a good irradiation behaviour, good thermal conductivity, small thermal expansion coefficients, good tensile properties and corrosion resistance. Firstly, a mixture of graphite powder, e.g. natural or synthetic graphite, and binder resin in isotropically pressed at high pressure in a rubber form to spheres. The spheres are then ground to granulate with an average grain diameter of 1 mm. To follow, the pyrolytic carbon and silicon carbide coated fuel particles for example consisting of e.g. uranium-thorium oxide kernels are jacketed with the same kind of pressed powder according to the Dragee method. After the jacketing the fuel particles are hot-pressed with the granulate at about 1500C and at a pressure of 60 kg/cm2 if phenol formaldehyde resin is used. The binder is coked by heating to 8000C in an inert atmosphere and annealing in vacuum at 1,8000C. Hexagonal prismatic block elements, amongst others, may also be formed by this method. (DG)