Patent Number: 045335133
Section: claims

1. In a water cooled nuclear reactor having a core and an enclosing means housing said core, said enclosing means comprising an elongated concrete body and a pressure chamber within said concrete body, said pressure chamber being substantially defined by a solid of revolution about a vertical, longitudinal axis of rotation, said pressure chamber having an opening directed to the axial direction and a cover arranged at said opening so as to give a pressure-tight sealing of said pressure chamber, said pressure chamber constituting only part of a larger cavity within said concrete body, said cavity in addition to said pressure chamber comprising a space located above said opening and connected with the outside of said concrete body by means of at least one transversal tunnel provided in said concrete body, said enclosing means being further characterized in that said space is defined in an upwards direction by means of a transversely extending limiting surface belonging to an integral portion of said concrete body, in that most of said limiting surface is disposed vertically above said cover, in that a gap extends vertically between said limiting surface and said cover, in that a plurality of compressive-force transmitting elements are arranged so as to bridge said gap, in that said cover is arranged relative to said space and dimensioned so as to be removable from said opening for maintenance of equipment associated with said core, and in that said at least one tunnel is dimensioned to permit transport of said cover through said tunnel upon removal of said cover from said opening. 2. Enclosing means according to claim 1 which further includes means for transporting said cover through said transversal tunnel. 3. Enclosing means as claimed in claim 1, wherein said concrete body comprises a plurality of pre-stressed loops of metallic material arranged in the concrete and completely surrounding said cavity, each of said loops substantially lying in a corresponding axial plane. 4. Enclosing means as claimed in claim 3, wherein each one of said loops comprises a first straight portion arranged axially outside said limiting surface, said first portion extending transversely from an outer limiting surface of said concrete body to an imaginary axial plane oriented perpendicularly to said first portion, a second portion connected to said first portion which approximately forms a circular arc of 90.degree., an axially extending third portion connected to said second portion, a semicircular fourth portion connected to said third portion (20), an axially extending fifth portion connected to said fourth portion, a sixth portion connected to said fifth portion and arranged along a circular arc of approximately 90.degree., and a straight transversely extending seventh portion connected to said sixth portion and extending to an outer limiting surface of said concrete body. 5. Enclosing means as claimed in claim 3, wherein said loops are each arranged in a loop-formed channel cast in said concrete body.