Patent Number: 051981840
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS One preferred embodiment of the present invention will be described hereunder with reference to FIGS. 1 to 2. FIG. is an elevational section similar to that of FIG. 7, and in FIG. 1, like reference numerals are added to elements and members corresponding to those shown in FIG. 7 and descriptions relating thereto are omitted here. Referring to FIGS. 1 to 2, the pedestal 12 has a cylindrical structure surrounding the RPV 2 and has a cross section partially shown in FIG. 2 taken along the line II--II in FIG. 1, which will be easily compared with the cross section of FIG. 8. Namely, as can be seen from FIG. 2, according to the present invention, the pedestal 12 is composed of a plurality of concrete wall sections 12a and connecting vents or passage sections 20 which are arranged alternately along the circumferential direction of the pedestal 12. The line 9, the cables 10 and the duct 11 communicating the upper dry well 5 with the lower dry well 7 are arranged within the connecting vent sections 20 and vent pipes 21 are disposed in the concrete wall sections 12a, respectively. The inner and outer surfaces of the pedestal 12 are lined by steel plates, for example. The vent pipe 21 is embedded in the concrete wall section 12a of the pedestal 12 so as to extend vertically and has an upper end opening opened outward to the drywell. The vent pipe is provided with a venting port 21a at its lower portion so as to communicate with the interior of the suppression chamber 8. The space above the vent pipes 21 is formed as vacant space 16 in the PCV 1. According to this arrangement, since the vacant space 16 is formed above the upper opening of each of the vent pipes 21, so that a space necessary for the steam flow passage at the reactor accident can be ensured without being obstracted by the arrangement of the line 9, the cables 10 and the duct 11. This advantage can be clearly understood in comparison with FIGS. 2 and 8 as cross sections. In this embodiment of the present invention, the numbers and the locations of the vent pipes 21 may be determined with reference to the correspondence to the internal pumps, not shown, which are arranged along the circumferential direction of the reactor core disposed in the RPV 2. According to this structure, the connecting vent 20 may be partially formed as concrete section as shown in FIG. 2 for strengthening the structure of the pedestal 12. A preferred modification of the present invention will be described hereunder with reference to FIGS. 3 and 6. First, as shown in FIG. 3, which is similar to the elevational section of FIG. 9, the vacuum breaker 24 and the fixing pipe 23 are arranged by utilizing the vacant space 16 above the vent tube 21 disposed in the concrete wall section 12a. Accordingly, the construction or arrangement of the vacuum breaker 24 and the fixing pipe 23 can be easily done without being obstructed by the arrangement of the line 9, the cables 10 and the duct 11. This will be also understood from FIG. 4. Next, as shown in FIGS. 5 and 6 as an alternation, the vent pipes 21 each being disposed in the concrete wall section 12a and having an extended portion are arranged adjacent to the connecting vent sections. Namely, each of the vent pipes 21 extends upward to the diaphragm floor 22 and opened to the space in the upper drywell 5 and the vacuum breaker 24 is directly connected to the extended portion of the vent pipe 21 through the fixing pipe 23. In this embodiment, the construction or arrangement of the vacuum breaker 24 can be easily done.