Nuclear reactor core

In that nuclear reactor core, several fuel assemblies are enclosed in a moderator vessel and fixed by an assembly-carrying grid, whereas each fuel-assembly comprises a polygonal can and several control-rod guide-tubes surrounded by said can. The assembly-carring grid is fixed to the vessel-cover and is so arranged that it provides a mechanical contact with the upper edges of the can-walls, so that the surfaces of fuel assembly cans located in vertical planes are intersected by vertical planes along the surfaces of the assembly-carrying grid. Such mechanical contact is established at places where the grid is provided with means for immobilizing the cans