[en] The pressure relief openings in the separating walls of the reactor building are closed with shielding elements, which can be made in the form of doors. They consist of a frame, which has a grid construction. The grid mesh is filled with granular shielding material, and is closed on at least one side by metal plates. These metal plates are surrounded by rubber seals, by which they adhere to the grid bars. On the occurrence of excess pressures the metal plates with the granular filling are pushed out of the grid mesh. (orig./PW)