JPH064697U - Reactor pressure vessel pedestal - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a pedestal for a reactor pressure vessel that can prevent deformation of the vent pipe due to excessive thermal stress and can significantly reduce the construction period. [Structure] An inner cylinder 21 and an outer cylinder 22 are formed into a double cylinder shape, and a plurality of vent pipes 26 are arranged at intervals between the inner cylinder 21 and the outer cylinder 22. Radiation shielding material that contains a large amount of hydrogen around the circumference
8 is filled.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pedestal for supporting a reactor pressure vessel, and more particularly to a pedestal for a reactor pressure vessel capable of allowing heat transfer in a vent pipe disposed inside.

[0002]

[Prior art]

 Generally, a reactor pressure vessel is supported by a cylindrical pedestal in a reactor containment vessel in a nuclear power plant, etc., and a diaphragm floor between the pedestal and the containment vessel causes a drywell and a suppression chamber to move up and down. And are demarcated. By the way, as the pedestal, conventionally, an inner cylinder and an outer cylinder are formed in a double cylinder shape, and steel vent pipes are arranged at intervals in an annular space between the inner cylinder and the outer cylinder. It is known that the pipes are installed and the surroundings of the vent pipes are cast with concrete. In this pedestal, even in case of accident such as a coolant in the dry well, the generated air-water mixture is led to the suppression chamber at the bottom through a vent pipe, where it is cooled down to increase the pressure in the dry well. Can be suppressed.

[0003]

[Problems to be solved by the device]

 However, in the pedestal with the above structure, since the surroundings of the vent pipe are hardened with concrete and its thermal expansion is restrained, when the high-heat steam-water mixture passes through the vent pipe, the vent pipe is subjected to excessive thermal stress. May cause buckling (buckling) on the inner surface.

In addition, since concrete is placed during the construction of the pedestal, a relatively long concrete hardening time is required, which is an obstacle to shortening the construction period.

Therefore, an object of the present invention is to provide a pedestal for a reactor pressure vessel which can prevent the deformation of the vent pipe due to excessive thermal stress and can significantly reduce the construction period.

[0006]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the pedestal of the present invention has a double cylinder shape in which an inner cylinder and an outer cylinder are supported to support a reactor pressure vessel, and a plurality of vent pipes are provided between the inner cylinder and the outer cylinder. Are arranged at intervals, and a granular radiation shielding material containing a large amount of hydrogen is filled around these vent pipes.

[0007]

[Action]

 By filling a granular radiation shielding material around the vent pipe instead of conventional concrete, the expansion of the vent pipe is allowed by the movement of the radiation shielding material, and the vent pipe is not exposed to excessive thermal stress. Absent. Also, when constructing the pedestal, it is only necessary to pour granular radiation shielding material, and it is not necessary to consider the hardening time of concrete.

[0008]

【Example】

 Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration inside the reactor containment vessel. In the figure, 11 is a reactor containment vessel, and a reactor pressure vessel 12 is provided at the center of the inside. The reactor pressure vessel 12 is supported by a pedestal 13 in the shape of a double cylinder that is erected on the inner bottom of the reactor containment vessel 11. A diaphragm floor 15 is bridged between the inner peripheral wall of the reactor containment vessel 11 and the outer peripheral surface of the pedestal 13, and the space inside the reactor containment vessel 11 serves as an upper dry well 16 and a lower suppression chamber 17. Compartments are formed. Reference numeral 18 is a lower dry well defined inside the suppression chamber 17 via the pedestal 13.

FIG. 2 is a plan sectional view of a pedestal 13 that supports the reactor pressure vessel 12. The pedestal 13 has a double cylindrical frame made up of an inner cylinder 21, an outer cylinder 22 and ribs 24 made of a steel plate (stainless steel). The inner cylinder 21 and the outer cylinder 22 forming the frame are coaxially arranged at a predetermined distance from each other, and the outer circumference of the inner cylinder 21 and the inner circumference of the outer cylinder 22 are connected by a plurality of ribs 24, 24 .... Has been done. The ribs 24, 24 ... Are provided radially with respect to the axial lines of the inner and outer cylinders 21, 22 and along the axial direction thereof, and circumferentially define an annular space defined between the inner and outer cylinders 21, 22. It is divided into multiple rooms. In each chamber divided by the rib 24, a bent tube 26 made of steel is arranged every other section.

Since the vent pipe 26 is for suppressing an abnormally high pressure in the upper dry well 16, as shown in FIG. 1, a plurality of discharge pipes 26b are horizontally provided at the bottom of the bottomed tubular conduit 26a. The opening of the conduit 26a communicates with the upper drywall 16 through the communication pipe 27, and the opening of the discharge pipe 26b communicates with the suppression chamber 17 through the outer cylinder 22. Around the vent pipe 26, granular mortar (radiation ray shielding material) 28 is filled in order to allow a heat transfer of the vent pipe 26 and have a radiation shielding function. The granular mortar 28 is formed in advance as containing a large amount of hydrogen element, and as shown in FIG. 3, the vent pipe 26 is provided in each chamber 29 defined by the inner and outer cylinders 21 and 22 and the rib 24. It is filled so as to cover the outer periphery of. In this case, the granular mortar 28 may be filled only in the chamber 29 in which the vent pipe 26 is inserted, and the other chamber 29 may be filled with concrete as in the conventional case.

Next, a procedure for constructing the pedestal 13 having the above structure will be described.

First, prior to the construction of the pedestal 13, a large amount of granular mortar 28 is formed in a factory or the like. At this time, the granular mortar 28 contains more water of hydration than conventional concrete. That is, a high radiation shielding effect can be obtained by including a large amount of hydrogen element in the form of water molecule in the mortar crystal.

Next, in the reactor containment vessel 11, the preformed blocks are assembled to form the inner cylinder 21 and the outer cylinder 22. Then, after connecting the inner cylinder 21 and the outer cylinder 22 by the ribs 24, the vent pipes 26 are arranged every other partition for each chamber 29 between the inner and outer cylinders 21, 22 partitioned by the ribs 24. Insert and assemble. After that, granular mortar 28 formed in advance in each chamber 29 between the inner and outer cylinders 21, 22 is poured from the upper opening, and the outer peripheral side of the vent pipe 26 is filled with the mortar 28 of a predetermined density. The filling of the granular mortar 28 is carried out at a time convenient for the progress of the work after the frame assembly of the pedestal 13.

As described above, according to the present embodiment, by filling the granular mortar 28 around the vent pipe 26 in the pedestal 13, the thermal expansion of the vent pipe 26 due to the movement of the granular mortar 28. Will be acceptable to some extent. Therefore, even if a high-heat air-water mixture passes through the vent pipe 26 in the event of an accident such as loss of coolant in the upper drywell 16, the vent pipe 26 is not subjected to excessive thermal stress, and the vent due to its thermal response Buckling of the pipe 26 can be prevented. Since the granular mortar 28 filled at this time contains more hydrogen element than conventional concrete, even if the granular mortar 28 is used, the radiation shielding effect is prevented from being lowered as much as possible. To be done.

Further, when constructing the pedestal 13, it is only necessary to flow the granular mortar 28 around the vent pipe 26, and since it is not necessary to pour concrete as in the conventional case, it takes no time to set the concrete. Since no consideration is required, the construction period of the pedestal 13 and, by extension, the construction period of the nuclear facility itself can be greatly reduced. Moreover, since the air vent from concrete is not required, the structure can be simplified.

In the above embodiment, the vent pipe 26 is filled with the granular mortar 28. However, the granular mortar 28 to be filled may be further mixed with lead particles or sand iron. A desired radiation shielding effect can be obtained by mixing an appropriate material. Further, the filler is not limited to the mortar 28 and may be another material. The point is to use a material with a high radiation shielding effect, that is, a radiation shielding material containing a large amount of hydrogen element.

[0018]

[Effect of device]

 In summary, according to the present invention, the following excellent effects are exhibited.

(1) Since the periphery of the vent pipe is covered with the granular radiation shielding material, heat transfer of the vent pipe can be allowed, and deformation of the vent pipe due to excessive thermal stress can be prevented.

(2) Since the simple work of pouring the granular radiation shielding material around the vent pipe at the time of construction of the pedestal is sufficient, the construction period of the pedestal can be significantly shortened.

[Brief description of drawings]

FIG. 1 is a front cross-sectional view showing a configuration example inside a reactor containment vessel.

FIG. 2 is a plan sectional view showing an example of a pedestal for supporting a reactor pressure vessel.

3 is an enlarged view showing a portion A of FIG. 2. FIG.

[Explanation of symbols]

 11 Reactor Containment Vessel 12 Reactor Pressure Vessel 13 Pedestal 16 Upper Drywell 17 Suppression Chamber 21 Inner Cylinder 22 Outer Cylinder 24 Rib 26 Vent Pipe 28 Granular Mortar (Radiation Shielding Material)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G21F 3/00 N 8607-2G

Claims (1)

[Scope of utility model registration request] 1. An inner cylinder and an outer cylinder are formed in a double cylinder shape so as to support a reactor pressure vessel, and a plurality of vent pipes are arranged between the inner cylinder and the outer cylinder at intervals. A pedestal for a reactor pressure vessel, characterized in that a granular radiation shielding material containing a large amount of hydrogen is filled around these vent pipes.