Patent Number: 053512774
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3. Referring to FIG. 2, after setting a cylindrical liner 11, temporary posts 14 and temporary trusses 15 are placed and a top slab liner 10 is laid on the temporary trusses 15, followed by setting of a sleeve 17 of the nuclear reactor container. Then, the cylindrical liner 11 and the top slab liner 10 are welded along a welding line 12. Subsequently, the top slab liner 10 and a sleeve 17 of the nuclear reactor container are welded together along a welding line 13. Meanwhile, a top slab steel reinforcement structure 8 (see FIG. 1) is prefabricated on the ground together with an auxiliary plate 19. The prefabricated top slab steel reinforcement structure 8 is lifted and set on the top slab liner 10. Then, a flange 16 and the sleeve 17 are welded together along a welding line 18. This welding is conducted simultaneously with the placement of concrete in the space on the outer diameter side of the auxiliary plate. After examination of the welding at the welding line 18, concrete is placed in the space defined by the integrated flange 16 and the sleeve 17, and the auxiliary plate 19. In an embodiment in which the top slab steel reinforcement structure 8 is integrated with the top slab liner 10, the top slab liner 10 serves as a reinforcer, so that the temporary trusses 15 shown in FIG. 2 can be eliminated. A further improvement in the efficiency of the construction work can be attained by integrating the top slab steel reinforcement structure 8, top slab liner 10 and the sleeve 17 of the nuclear reactor container, in advance of the installation. An embodiment which uses such an integrated structure is shown in FIG. 4. Referring to FIG. 4, H-shaped steel bars 20 are laid on the upper surface of the top slab liner 10 and are fixed to the same by welding. Then, the steel reinforcement structure 8 is assembled on the H-shaped steel bars 20 and the lower end of the steel reinforcement structure 8 is welded to the upper surfaces of the H-shaped steel bars 20, whereby the steel reinforcement structure is integrated with the top slab liner 10. The sleeve 17 and the top slab liner 10 have been welded together along a welding line 13. In this embodiment, the top slab liner 10 functions as a reinforcer, so that the temporary trusses 15 shown in FIG. 2 can be eliminated. Although each of the described embodiments employs an auxiliary plate 19 which is assembled together with the top slab steel reinforcement structure, the use of the auxiliary plate 19 is not essential. Without the auxiliary plate, the flange and the container sleeve must be welded before any concrete is poured. The use of the auxiliary plate 19, however, is preferred because the auxiliary plate stiffens the steel reinforcement structure so as to prevent deformation of this structure when the same is lifted for installation. The auxiliary plate also contributes to strengthening of the built-up nuclear reactor container. Additionally, the auxiliary plate acting as a barrier makes it possible to divide the placement of concrete whereby welding the flange and the container sleeve can be conducted on the inner diameter side of the auxiliary plate while pouring concrete into a space on the outer diameter side as shown schematically in FIG. 8. As will be understood from the foregoing description, according to the invention, the flange is formed separately from the sleeve and is joined to the latter by welding. Therefore, construction of a nuclear reactor container having a flange of a diameter greater than the inside diameter of doughnut-shaped steel reinforcement structure can be conducted without difficulty by welding the flange to the sleeve after installation of the steel reinforcement structure, thus shortening the term of the construction work. In the embodiment in which the top slab steel reinforcement structure, top slab liner and the sleeve are integrated beforehand, the efficiency of the construction work is further improved because the temporary trusses can be omitted. The installation of the above-mentioned integral structure can be facilitated by splitting the sleeve portion and the flange portion. The cylindrical auxiliary plate prevents the welding line between the sleeve and the flange from being hidden by concrete so as to make it possible to simultaneously conduct the welding and the placement of concrete on the opposite side of the auxiliary plate. The auxiliary plate also strengthens the steel reinforcement structure so as to prevent deformation of this structure when the same is lifted for installation and also contributes to strengthening of the built-up nuclear reactor container.