Building block for the construction of a thermal reactor core

The core of a helium cooled power reactor is composed of columns of indivifual building blocks of hexagonal cross sections and made of compacted graphite moderator substance. Parallel to the outer surfaces of the building blocks, which are closed by plane end faces, there are cooling channels in the interior, closed fuel compartments filled with packings of spheres consisting of fuel, and bores for control rods. The channels and bores of building blocks stacked on top of each other match. The cooling channels are arranged at the corners of equilateral triangles. To facilitate alignment of the columns, the building blocks and blocks, respectively, are equipped with connecting elements. These are made of hollow pins extending coaxial, e.g., with the three ends of the cooling channels across one end face each of a building block. The other end face of each building block has recesses around the corresponding cooling channels into which the pins fit. This ensures good structural stability. Heat transfer of the uranium and thorium dicarbide paricles, respectively, surrounded with pyrolytic carbon in the fuel chambers and the coolant flow is guaranteed. (DG)