JPS60102592A - 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 fast breeder reactors, and more particularly to means for preventing natural convection of cover gas occurring in the gap between the inner circumferential surface of the reactor vessel and the outer circumferential surface of the shielding plug. .

[Technical background of the invention]

Generally, in a fast breeder reactor that uses liquid metal such as liquid sodium as a coolant, the upper opening of the reactor vessel is closed with a shielding plug. FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a conventional fast breeder reactor, and reference numeral 1 in the figure indicates a reactor vessel. A reactor core 2 is housed within the reactor vessel 1, and liquid storium 3 as a coolant is stored up to the liquid level shown in the figure. This liquid sodium 3 flows into the lower part of the reactor vessel 1 through an inlet pipe 4, flows upward through the reactor core 2, is heated, and is discharged from an outlet pipe 5. The upper opening of the furnace vessel 1 is closed by a shielding plug 6, and the inside of the furnace vessel 1 is hermetically sealed. Further, a cover gas space 8 formed from the coolant liquid level 7 in the furnace vessel 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 7, but also because the inside of the shielding plug 6 has an insulating structure, the amount of heat radiated from this part is suppressed to a low level, and it is maintained at a very high temperature. has been done. Note that 9 in the figure is a core upper mechanism provided through the shielding plug 6.

[Technical background of the invention]

Incidentally, a gap 10 of about 20 to 25 mm is formed between the inner peripheral surface of the reactor vessel 1 and the outer peripheral surface of the shielding plug 6 in such a fast reactor so that the shielding plug 6 can rotate smoothly. Since the heat source in the gap 1o is located at the bottom, the temperature of the cover gas in the gap 1o becomes lower as it goes to the top.Especially at the top, the cover gas is cooled to near normal temperature, and the wall surface of the gap 10,
That is, the average temperature of the inner peripheral surface of the furnace vessel 1 and the outer peripheral surface of the shielding plug 6 is kept much lower than the temperature of the cover gas near the coolant liquid level 7. Therefore, a density difference occurs between the cover gas near the coolant liquid level 7 and the cover gas in the gap 10, and the dense heavy gas cooled in the gap 10 and the density near the coolant liquid level 7 occur. Natural convection occurs between the particles and the small, light debris, resulting in heat exchange. However, this natural convection does not necessarily form a two-dimensional flow that rises at the center of the gap 10 and descends at the side walls, but instead forms a flow that rotates in the circumferential direction of the shielding plug 6. As a result, a large temperature difference occurs in the circumferential direction of the shielding plug 6, which may cause large thermal stress to act on the structural material and cause thermal deformation.

Also, due to this natural convection, the evaporated sodium of liquids 1 to 3 adheres to the side wall of the gap 10, and the shielding plug 6
There was also a risk that the rotational movement of the motor would not be able to operate smoothly.

[Purpose of the invention]

The present invention was made in view of the above circumstances,
The purpose is to provide a fast breeder reactor that can effectively prevent the occurrence of natural convection of the cover gas, and can also effectively prevent the deposition of evaporated l-lium on the inner peripheral surface of the reactor vessel and the outer peripheral surface of the shielding plug. There is a particular thing.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention has been developed to provide a planar circular shape having four ports for medium heat and installed in the cover gas space so as to be located below the gap between the inner circumferential surface of the furnace vessel and the outer circumferential surface of the shielding plug. an annular fixing groove member, a plurality of columns that are installed along the same direction on the fixing groove member so as to be located in the widthwise center of the gap, and a plurality of columns that are attached to the columns and that are attached to the inner circumferential surface of the furnace vessel and the shield. a plurality of convection prevention plates that come into elastic contact with the outer peripheral surface of the plug and vertically partition the gap in the circumferential direction; and a plurality of convection prevention plates that are provided between the fixed groove member and the shielding plug and come into elastic contact with the convection prevention plates and partition the gap and the cover. This device is characterized by the addition of a lithium evaporation prevention plate that partitions the space from the gas space.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. As shown in the figure, the fast breeder reactor according to the present invention has a planar annular fixing groove 44101 in the cover gas space 8 located below the gap 10 between the inner peripheral surface of the reactor vessel 1 and the outer peripheral surface of the shielding plug 6. is provided. This fixing groove member 101 has an opening in the center, has an L-shaped cross section, and is arranged by appropriately fixing the outer circumferential edge of the horizontal portion to the inner circumferential surface of the furnace vessel 1. In addition, a plurality of columns 102 are erected along the circumferential direction in the horizontal part of the fixed groove member 101 so as to be located at the center in the width direction within the gap 10, and these columns 102 are made of a shape memory alloy to prevent convection. A plate 103 is attached. This convection prevention plate 103 is configured as shown in FIGS. 3 to 5, for example, and deforms when the temperature inside the gap 10 reaches around 200°C, causing the inner peripheral surface of the furnace vessel 1 and the outer peripheral surface of the shielding plug 6 to deform. They come into elastic contact and partition the gap 10 vertically in the circumferential direction.

For example, the convection prevention plate 103 shown in FIG. The contact piece 32 is formed, and the overall planar shape is approximately U.
The base of the wing piece 31 is connected to the branch office 10.
2 and arranged point-symmetrically in the inner and outer directions with the support column 102 as the center. When the temperature inside the gap 10 reaches around 200'C, the angle of inclination of the blades 31 is changed in accordance with the width of the gap 10, so that the gap 10 becomes perpendicular in the circumferential direction. It's in charge.

In addition, the convection prevention plate 103 shown in FIG. 4 is made of elastic blades 41 which are curved into a substantially C-shaped cross section so that their curved outer circumferential surface comes into elastic contact with the inner circumferential surface of the reactor vessel 1 or the outer circumferential surface of the shielding plug 6. One end is fixed to the column 102, and the tubes are arranged point-symmetrically in the inner and outer directions with the column 102 as the center. In this case, when the temperature inside the gap 10 reaches around 200°C, the elastic blades 41 expand outward in diameter corresponding to the width of the gap 10, thereby vertically partitioning the gap 10 in the circumferential direction. ing.

Further, the convection prevention plate 103 shown in FIG. It is fixed to the support column 102 via the support column 102. In this case, similarly to the convection prevention plate 103 shown in FIG. 4, when the temperature inside the gap 10 reaches around 200°C, the elastic contact piece 51 expands in diameter to the outside corresponding to the width of the gap 10. The gap 10 is vertically partitioned in the circumferential direction.

In addition to the convection prevention plate 103, a cylindrical sodium evaporation prevention plate 104 made of a shape memory alloy is provided between the shielding plug 6 and the fixed groove member 101. This sodium evaporation prevention plate 104 is fixed and supported on the lower surface of the shielding plug 6, and has a tip section curved into a substantially U-shape. This step 1 Helium evaporation prevention plate 104
When the temperature in the gap 10 reaches around 200° C., the tip portion deforms so that its curved outer peripheral surface comes into elastic contact with the convection prevention plate 103. Therefore, the gap 10
When the temperature in the gap 10 reaches around 200° C., the cover gas space 8 is partitioned off by the sodium vapor-deposited plates 104.

Next, the effect will be explained. As mentioned above, the cover gas filled in the 7J gas space 8 formed from the coolant liquid level 7 in the furnace vessel 1 to the lower surface of the shielding plug 6 absorbs heat from the coolant liquid level 7. In addition, since the inside of the shielding plug 6 has a heat insulating structure, the heat radiation m from this part is suppressed to a low level, and the shielding plug 6 is maintained at a considerably high temperature. on the other hand,
Since the cover gas in the gap 10 is away from the heat source,
The temperature is kept considerably lower than that of the cover gas near the coolant liquid level 7. Therefore, natural convection may occur between the heavy gas with high density in the gap 10 and the light gas with low density near the coolant liquid level 7.
Since a convection prevention plate 10 that vertically partitions the gap 10 in the circumferential direction is installed inside the gap 10, the cover gas flows through the gap 10.
The inner surface heals in the circumferential direction and no longer flows, suppressing the occurrence of natural convection.

In addition, since the gap 10 and the cover gas space 8 are partitioned by the thorium evaporated plate 104, evaporated sodium does not enter the gap 10, and the side walls of the gap 10, that is, the inner circumferential surface of the furnace vessel 1, and the shielding plug 6 Evaporated sodium is prevented from adhering to the outer peripheral surface. In addition, in this embodiment, the convection prevention plate 103 and the lithium prevention plate 10
4 is formed from a shape memory alloy, so the gap 10
When the temperature inside the furnace is low, the convection prevention plate 103 and the S1 to Rium prevention plates 104 do not deform, and in particular, the convection prevention plate 103 does not come into elastic contact with the inner peripheral surface of the furnace vessel 1 and the outer peripheral surface of the shielding plug 6, so that the shielding plug There is no risk of interfering with the rotational movement of 6.

〔Effect of the invention〕

As described above, according to the present invention, the fixing groove member is provided in the cover gas space so as to be located below the gap between the inner circumferential surface of the furnace vessel and the outer circumferential surface of the shielding plug, and has a planar annular shape with an opening in the center. a plurality of struts standing upright along the circumferential direction of the fixed groove member so as to be located at the center in the width direction of the gap; a plurality of convection prevention plates that contact and vertically partition the gap in the circumferential direction; and a plurality of convection prevention plates that are provided between the fixed groove member and the shielding plug and come into elastic contact with the convection prevention plates to partition the gap from the cover waste space. Since the structure incorporates a sodium evaporation prevention plate, it is possible to effectively prevent the occurrence of natural convection of the cover gas, and also to effectively prevent the adhesion of evaporated sodium to the inner peripheral surface of the furnace vessel and the outer peripheral surface of the shielding plug. We can provide a fast breeder reactor that can prevent

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing the schematic configuration of a conventional fast breeder reactor;
Figures 2 to 5 all show one embodiment of the present invention, with Figure 2 being a sectional view of a fast breeder reactor, and Figures 3 to 5 showing an example of a convection prevention plate. FIG. DESCRIPTION OF SYMBOLS 1... Reactor vessel, 2... Core, 3... Liquid sodium, 4... Inlet piping, 5... Outlet piping, 6... Shielding plug, 7... Coolant liquid level, 8...Cover gas space, 9...Core upper mechanism, 10...Gap portion, 101
. . . Fixed groove member, 102 . . . Pillar, 103 . . . Convection prevention plate, 104 . Applicant's representative Patent attorney Takehiko Suzue Figure 3 Figure 3 Figure 4 Figure 5

Claims (4)

[Claims] (1) A planar annular fixing groove member provided in the cover gas space so as to be located below the gap between the inner circumferential surface of the reactor vessel and the outer circumferential surface of the shielding plug, and having a frontage in the center, and a fixing groove member in the width direction of the gap. A plurality of columns are installed in the fixed groove member along the circumferential direction so as to be located in the center, and are attached to the columns and elastically contact the inner circumferential surface of the furnace vessel and the outer circumferential surface of the shielding plug to extend the gap in the circumferential direction. a plurality of convection prevention plates vertically partitioning the fixed groove member and the shielding plug; and a lithium evaporation prevention plate provided between the fixed groove member and the shielding plug and elastically contacting the convection prevention plates to partition the gap and the cover gas space. A fast breeder reactor characterized by comprising: (2) The fast breeder reactor according to claim 1, wherein the convection prevention plate and the sodium evaporation prevention plate are made of a shape memory alloy. (3) The temperature in the gap of the convection prevention plate is 2OO℃.
The fast breeder reactor according to claim 2, wherein the fast breeder reactor is deformed when it reaches the front and back and comes into elastic contact with the inner circumferential surface of the reactor vessel and the outer circumferential surface of the shielding plug. (4) The high speed according to claim 2, wherein the lithium evaporation prevention plate deforms when the temperature in the gap reaches around 200°C and comes into elastic contact with the convection prevention plate. Breeder reactor.