Patent Number: 053512774
Section: claims

1. A method of constructing a top slab of a nuclear reactor container having a sleeve with a flange and a prefabricated doughnut-shaped steel reinforcement structure wherein the outermost diameter of said flange is greater than the innermost diameter of said prefabricated doughnut-shaped steel-reinforcement structure, comprising the steps of: placing a container sleeve separate from said flange, at a position where said top slab is to be constructed;  lifting said prefabricated doughnut-shaped steel reinforcement structure and placing this structure at a position where it forms said top slab; and  welding said flange to said container sleeve for mounting a top head of said nuclear reactor container on said flange.  prefabricating a structure integrating a top slab liner, a container sleeve, separate from said flange, fixed to the inner periphery of said top slab liner substantially orthogonal to said top slab liner, and said prefabricated doughnut-shaped steel reinforcement structure on said top slab liner, and lifting and mounting said prefabricated doughnut-shaped steel reinforcement structure to a position where said top slab is to be constructed; and  welding said flange to said container sleeve for mounting a top head of said nuclear reactor container on said flange.  a bottom-equipped cylindrical portion for containing a nuclear reactor therein:  a top slab provided on top of said cylindrical portion and composed of a doughnut-shaped steel reinforcement structure and concrete placed integrally with said doughnut-shaped steel reinforcement structure, said top slab having a central bore;  a container sleeve outlining said central bore of said top slab; and  a flange fixed by welding to said container sleeve and said flange having its outermost diameter greater than the innermost diameter of said doughnut-shaped steel reinforcement structure; and  a top head attached to said flange. 2. A method according to claim 1, wherein said prefabricated doughnut-shaped steel reinforcement structure has a cylindrical auxiliary plate integrated therewith and located near the innermost circumference of said prefabricated doughnut-shaped steel-reinforcement structure. 3. A method according to claim 2, wherein said welding said flange to said container sleeve is conducted simultaneously with pouring concrete in and solidifying the same on the outer diameter side of said cylindrical auxiliary plate, followed by pouring concrete in and solidifying the same on the inner diameter side of said cylindrical auxiliary plate, bounded by said container sleeve and said cylindrical auxiliary plate. 4. A method of constructing a top slab of a nuclear reactor container having a sleeve with a flange and a prefabricated doughnut-shaped steel reinforcement structure wherein the outermost diameter of said flange is greater than the innermost diameter of said prefabricated doughnut-shaped steel reinforcement structure, comprising the steps of: 5. A method according to claim 4, wherein said prefabricated doughnut-shaped steel reinforcement structure has a cylindrical auxiliary plate integrated therewith and located near the innermost circumference of said prefabricated doughnut-shaped steel reinforcement structure. 6. A method according to claim 5, wherein welding said flange to the container sleeve is conducted simultaneously with pouring concrete in and solidifying the same on the outer diameter side of said cylindrical auxiliary plate, followed by pouring concrete in and solidifying the same on the inner diameter side of said cylindrical auxiliary plate, bounded by said container sleeve and said cylindrical auxiliary plate. 7. A nuclear reactor container, comprising: 8. A nuclear reactor container according to claim 7, wherein a cylindrical auxiliary plate is integrated with said doughnut-shaped steel reinforcement structure near the innermost circumference thereof.