JPS60131494A - Fast breeder reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a fast breeder reactor, and particularly to a method for reducing thermal stress caused by natural convection that occurs in an annular gap formed between a reactor vessel and a shielding plug. 11113 and a means for preventing radiation streaming in the gap.

[・Technical background of the invention]

In general, fast breeder reactors that use liquid metal such as liquid sodium as a coolant require a strict high-temperature structure because the coolant temperature at the core exit is extremely high.

FIG. 1 is a diagram showing a schematic configuration of a conventional fast breeder reactor, and the reference numeral 1 in the figure is a reactor vessel. Inside this reactor vessel 1 is a reactor core 2.
A coolant 3 such as liquid sodium is stored up to the liquid level shown in the figure. -Then, this coolant 3 flows into the lower part of the reactor vessel 1 from the inlet pipe 4, flows upward in the reactor core 2, is heated, and flows out from the outlet pipe 5. The upper end opening of the furnace vessel 1 is closed by a shielding plug 6, which is supported by a support spacer 8 installed on the upper part of a support structure 7. A cover gas space 9 formed from the coolant liquid level in the furnace alarm 1 to the lower surface of the shielding plug 6 is filled with a cover gas such as argon gas. This cover gas not only receives heat from the coolant liquid level, but also because the inside of the shielding plug 6 has an insulating structure, the amount of heat dissipated from this part is suppressed to a low level, and it is maintained at a very high temperature. ing.

On the other hand, a shielding plug 6 is provided between the furnace vessel 1 and the shielding plug 6.
An annular surrounding part 1o of about 20 to 25 mm is formed so that it can rotate smoothly. This annular gap 1
Since the heat source is located at the bottom of the cover gas, the temperature of the cover gas in O becomes lower as it goes to the top.In particular, at the top, it is cooled to near room temperature, and the cover gas inside the annular gap 10, that is, the inner peripheral surface of the furnace vessel 1 and the shielding plug 6, is cooled down to near room temperature. The average temperature of the outer peripheral surface is kept at a much lower temperature than the temperature of the cover gas near the coolant liquid level. Therefore, a density difference occurs between the cover gas near the coolant liquid surface and the cover gas in the annular gap 10, and the dense heavy gas cooled in the annular gap 1o and the cover gas near the coolant liquid surface Natural convection occurs between the gas and the light gas with low density. However, this natural convection does not necessarily form a two-dimensional flow that rises at the center of the annular gap 10 and descends at the side walls, and as shown in FIG. rotating flow 1
1.degree. 12, a non-uniform temperature distribution occurs in the circumferential direction of the furnace vessel 1, and there is a risk that large thermal stress will act on the structural members of the furnace vessel 1 and the like, causing thermal deformation.

Therefore, several proposals have been made in the past for the purpose of suppressing this natural convection, such as providing a convection suppressing structure at the lower end or middle part of the annular gap 10.

[Problems with background technology]

However, in principle, all of the conventional proposals of this type aim to suppress natural convection by extremely reducing the gap width of the annular gap 10, and for this purpose, large can manufacturing structures are required. There was a problem in that the furnace vessel 1 and the shielding plug 6 required very strict dimensional tolerances in manufacturing. Further, when the height of the annular gap 10 increases as the size of the nuclear reactor increases, there is a problem that natural convection cannot be sufficiently suppressed even if only the lower end of the annular gap 10 is closed.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to effectively suppress natural convection occurring in the annular gap between the furnace vessel and the shielding plug with a simple structure, and to effectively suppress the natural convection that occurs in the annular gap between the furnace vessel and the shielding plug. The objective of this project is to propose an extremely reliable fast breeder reactor that does not require a high degree of dimensional accuracy to manufacture.

[Summary of the invention]

In order to achieve the above object, the present invention provides a cylindrical convection ring in the annular gap formed between the furnace vessel and the shielding plug, forms an annular part protruding inside the convection ring, and It is characterized by forming a plurality of convection chambers partitioned in the circumferential direction below the section.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to FIGS. 3 to 5.

3 to 5 are diagrams showing one embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. In this embodiment, as shown in FIG. 3, a cylindrical convection ring 13 is provided in an annular gap 10 formed between the furnace vessel 1 and the shielding plug 6 so as to engage with a flange at the upper end of the furnace vessel 1. It is being This convection ring 13, as shown in FIG.
An annular portion 14 protruding inwardly is formed. A plurality of convection chambers 15 partitioned in the circumferential direction are formed below this annular portion 14, and natural convection occurs within each of these convection chambers 15. In addition, the partition wall 16 between the multiple convection chambers 15 is provided with a cutout groove 17 that opens the lower and radial sides of the convection ring 13 to absorb thermal stress due to natural convection generated within each convection chamber 15. It is supposed to be done.

Next, as shown in Figure 2 for piles to explain the action, the annular gap 1
The natural convection that occurs at
．． 12, and a large temperature difference occurs between the upward flow generation position and the downward flow generation position of the circulating flows 11 and 12, causing thermal stress and thermal deformation.

It is known that the temperature difference caused by such circulating flows generally depends on the number of circulating flows (the number of bears), and the larger the number of circulating flows, the smaller the temperature difference. In this embodiment, as shown in FIG. 5, natural convection occurs within each convection chamber 15 of the convection ring 13, so the number of natural convection increases.
Temperature differences can be alleviated. Therefore, according to this embodiment, natural convection can be suppressed simply by providing the convection ring 13 in the annular gap 1o, so that strict dimensional accuracy is not required for the furnace vessel 1 or the shielding plug 6, etc. as in the conventional case. do not have. Further, by providing a plurality of protruding annular portions 14 on the inner circumferential surface of the convection ring 13, it is also possible to reduce radiation passing through the annular portions 14. In addition, in the above embodiment, the convection ring 13 is shown in which the notch 1R17 is provided in the partition wall 16 between each convection chamber 15, but the notch groove 17 is not necessarily required, and whether it is necessary or not depends on high-speed growth. It is determined by the operating conditions of the furnace, the number of convection chambers 15, etc.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a cylindrical convection ring is provided in the annular gap formed between the furnace vessel and the shielding plug, and an annular portion protruding inside the convection ring is formed. Since a plurality of convection chambers are formed in the circumferential direction below this annular part, natural convection occurring in the annular gap between the furnace vessel and the shielding plug can be suppressed, and the furnace vessel and shielding A highly reliable fast breeder reactor can be provided without requiring a high degree of dimensional accuracy in manufacturing plugs and the like.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional view of a conventional fast breeder reactor, Figure 2 is a diagram showing a model of natural convection that occurs in a conventional annular gap, and Figure 3 is a diagram showing a model of natural convection that occurs in a conventional annular gap.
5 to 5 are diagrams showing one embodiment of the present invention, in which FIG. 3 is an enlarged vertical sectional view of the annular gap, FIG. 4 is a sectional view of the convection ring, and FIG. 5 is each convection chamber of the convection ring. FIG. 2 is a diagram showing natural convection that occurs in 1... Furnace vessel, 2... Core, 4... Inlet piping, 5
... Outlet piping, 6... Shielding plug, 10... Annular gap, 13... Convection ring, 14... Annular part, 1
5... Convection chamber, 16... Partition wall, 17... Notch groove. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) A reactor core, a reactor vessel that houses this reactor core, and a shielding plug that closes the upper end opening of this reactor vessel! In a fast breeder reactor that is equipped with A fast breeder reactor characterized by forming a plurality of convection chambers partitioned in the circumferential direction. (2) The fast breeder reactor according to claim 1, wherein the convection ring has notched grooves in the partition walls between the convection chambers.