Abstract: A cylindrically shaped prestressed concrete tank for a gas-cooled high temperature nuclear reactor plant includes a centrally located chamber for the reactor with a number of horizontally extending compartments located below the reactor chamber and at least two different groups of vertically extending compartments located radially outwardly from reactor chamber. The tank is prestressed by vertically extending tensioning elements and two different groups of horizontally extending tensioning elements. One group of horizontally extending tensioning elements extend chordally alongside and for the vertical range of the horizontal compartments and are anchored on the outer surfaces of the tank. The other group of horizontal tensioning elements are ring-shaped and extend in channels around the outer surface of the tank. This other group is located above and below the vertical range of the horizontal compartments.