JPH025278B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a core restraint mechanism for tightening and fixing a core block of a high-temperature gas-cooled nuclear reactor to a core barrel within the reactor.

[Prior art and its problems]

The high-temperature gas-cooled nuclear reactor mentioned above is already well known, and its core structure consists of regular hexagonal blocks arranged densely in a plane, as shown in Figures 5 and 6. There is. In other words, six standard fuel blocks 1 surrounding one control block form a set of fuel handling areas, and the outer periphery of this block is surrounded by movable reflector blocks 2, fixed reflector blocks 3, and A core block is constructed by stacking assembled blocks surrounded by side shields 4 in a multi-layered manner. Such a core block is constructed on a diamond grid installed in the pressure vessel 5 via a hearth insulation layer, a high temperature plenum block, etc. This prevents the difference in thermal expansion between the core block and the in-core support structure that supports it during reactor operation and shutdown, or the displacement of the core block due to earthquakes. A core barrel 6 is installed on the inner peripheral side of the pressure vessel 5 surrounding the core block, and the core block is connected to the core barrel 6 in order to seal the space between the core blocks and prevent leakage from the normal flow path of the cooling gas. It is tightened and fixed via a core restraint mechanism whose details will be described later. Note that 7 is a main cooling pipe drawn out from the pressure vessel 5. Here, the cooling gas introduced into the pressure vessel from the inlet pipe of the main cooling pipe 7 flows upward through the gap between the outer periphery of the core block and the pressure vessel 5, and then reverses from above the core block and flows into the core block. After flowing down the fuel channel inside the furnace and being heated to a high temperature of about 1000°C, it is discharged from the high temperature plenum through the outlet pipe of the main cooling pipe 7 to the outside of the furnace. Next, the conventional structure and operation of the core restraint mechanism described above will be described. That is, the core restraint mechanism can be roughly divided into two ring-shaped restraint bands 8, upper and lower, which are arranged to surround the outer periphery of each layer of the core block, and a core barrel that restrains and supports the restraint bands 8 to the core barrel 6. A radial key 9 protrudes radially from the radial key 9 and an initial tightening device 10 that applies an initial tightening tension to the restraint band.
It is made up of. Its detailed structure is as shown in FIG. 7. First, the restraint band 8 is constructed by interconnecting a plurality of band segments 11 in a ring shape, and is connected to the outer periphery of the fixed reflector block 3 constituting the core block. It is arranged to surround the Furthermore, the band segments 11 constituting the restraint band 8 are interconnected by pins 12 at both ends thereof, and the interconnected portions of the band segments 11 over the entire circumference of the restraint band 8 are used to apply a tensile force to the restraint band 8. initial tightening device 10
are installed facing each other. This initial tightening device 10
A top and bottom double band support member 13 having a bifurcated leg portion 13b whose tip portion 13a is connected to the upper and lower ends of a pin 12 connecting band segments 11, and a central portion of the band support member 13. A removable pressurizing operation unit 1 equipped with a hydraulic cylinder interposed in a recess space with the outer wall surface of the side shield 4
4, and a spacer 15 that is inserted into the gap between the leg portion 13b of the band support member 13 and the side shield 4 to maintain the tightened state when the initial tightening tension is applied by the pressurizing operation unit 14. It is configured. The tip end 13a of the band support member 13 is fitted into a key groove of a radial key 9 extending from the core barrel 6, and is restrained and supported by the core barrel 6 together with the restraint band 8. Next, the procedure for tightening the core block using the above mechanism will be explained. In other words, core block 1
At the stage where the layers are laminated and assembled, and the assembly of the restraint band 8 and the band support member 13 is supported on the outer periphery by the radial key 9 on the core barrel side, first, each band support member is attached to the entire circumference of the restraint band 8. Member 13
The above-mentioned pressurizing operation unit 14 is interposed between the reactor and the side shield 4 on the core block side. Subsequently, a predetermined hydraulic pressure is simultaneously applied to the hydraulic cylinders individually from the hydraulic system, and the restraining band 8 is simultaneously expanded from the inner circumferential side over its entire circumferential area via each band supporting member 13. Here, for each band segment 11, use a strain gauge or the like to check whether tension is applied uniformly to the upper and lower two restraining bands 8 over the entire circumference, and if there is local excess or deficiency in tension, check that part. The hydraulic pressure applied to the hydraulic cylinder is adjusted to provide even tension all around. At this tightening stage, the band support member 13 is lifted from the wall surface of the side shield 4. Next, the holding spacer 15 is inserted so as to completely fill the gap between the leg part 13b of the band support member 13 and the wall surface of the side shield 4, and the restraint band 8 is fixed and held in the expanded state. . As a result, one layer of the core block is tightened and fixed by the initial tightening tension applied to the restraint band via the spacer 15 and the band support member 13. Next, remove the hydraulic pressure from the hydraulic cylinder and pressurize operation unit 1.
4 is in a free state, the unit 14 is removed and pulled upwards, completing the initial tightening work for one layer of the core block. Subsequently, in the assembly process of the next layer, the initial tightening of the core block is performed using the pressurizing operation unit 14 used previously in the same procedure as the previous time. Note that the number of pressure operation units 14 corresponding to the number of band segments 11 constituting the restraint band 8 is prepared. For example, if one strip of the restraint band is composed of 18 band segments,
18 pressurized operation units will be prepared. However, the conventional structure described above has the following problems. That is, since the radial key 9 is installed in a limited narrow gap between each vertex of the polygonal restraint band 8 and the core barrel 6,
It is difficult to install a large radial key with sufficient dimensional strength. If the radial key is large, the inner diameters of the core barrel and pressure vessel must be increased accordingly.
Furthermore, if an excessive unbalanced tension is applied to each band segment 11 on the circumference of the restraint band 8 due to an earthquake or an unexpected breakage accident of the restraint band, the band connecting portion will hit the side of the radial key 9 and an excessive load will be applied. In addition, in the worst case, the radial key 9 may fall off from the core barrel 6. In addition, if a difference in thermal expansion occurs between the core block and the core barrel in the vertical axial direction when the connection part of the restraint band is pressed against the side surface of the radial key and there is a difference in thermal expansion in the vertical axial direction, the core The blocks shift through the restraint mechanism, resulting in gaps between the upper and lower layers of the core block, causing gas leaks.

[Purpose of the invention]

This invention has been made in consideration of the above points, and its purpose is to eliminate the drawbacks of the conventional structure, to ensure sufficient installation space for the radial key mechanism that connects the core barrel and the core restraint mechanism, and to provide a restraint mechanism. Even if tension imbalance occurs in the restraint band due to breakage of the band, etc., the radial key mechanism can be maintained at all times without the risk of excessive load being applied to the radial key mechanism, and the core barrel and the radial key To provide a core restraint mechanism for a nuclear reactor that can avoid an abnormal situation in which a core block unduly shifts together with a core barrel even if a thermal expansion difference occurs between the core block and the core barrel.

[Key points of the invention]

In order to achieve the above object, the present invention relates to a restraining band formed by interconnecting a plurality of band segments arranged in a ring shape so as to surround the outer periphery of each layer of a core block and tighten the core block. Restraint ring plates are installed above and below the restraint band, sandwiching the restraint band in the center and connected to each band segment interconnection portion of the restraint band via a radial key mechanism, and at an intermediate position between the interconnection portions of adjacent band segments. The restraint ring plate and the core barrel are mutually connected by a radial key mechanism, and the unbalanced tension of the restraint band is received by the restraint ring plate, so that the radial key mechanism between the core barrel and the core barrel is not subjected to any load that would inhibit the radial key function. This is to prevent the addition of

[Embodiments of the invention]

1 to 4 show an embodiment of the present invention, in which FIG. 1 is a partial plan view of main parts showing an assembled state, and FIGS. 2 and 3 are respectively shown in the direction of the arrow in FIG. - A sectional view, and FIG. 4 is a partial external perspective view, and the same reference numerals as in FIG. 7 indicate the same members. That is, a restraining band 8 is provided around the outer periphery of the core block via a band supporting member 13 as in the conventional case. Corresponding to each strip of the restraint band 8, restraint ring plates 16 and 17 are disposed on the inner peripheral side of the core barrel 6 above and below the restraint band 8 with the restraint band 8 in the center. The restraint ring plates 16 and 17 have, on the one hand, a radial keyway 18 opened on the circumference at a location corresponding to the interconnection portion of each band segment 11 of the restraint band 8;
A collar 19, which functions as a radial key, is fitted into the pin 12 of the interconnection portion, and is connected to the restraint band 8 by the pin. In addition, between the core barrel 6 and the core barrel 6, a radial key groove 20 is located midway between the interconnecting parts of adjacent band segments and is cut out in the outer peripheral edge of the restraining ring plate.
and a radial key 21 disposed on the inner periphery of the core barrel 6 facing the key groove. With this structure, each strip of the restraint band 8 is restrained and supported in the circumferential direction by the core barrel 6 while allowing thermal expansion in the radial direction via the restraint ring plates 16 and 17. By connecting the restraint band 8 to the core barrel 6 through the restraint ring plates 16 and 17 in this way, it is possible to prevent the restraint band from unbalanced elongation during normal operation, as well as from unexpected accidents such as the restraint band breaking. Even if an excessively unbalanced tension occurs, this circumferential load is received by the restraining ring plates 16 and 17 and
This does not affect the radial key mechanism 22 between the two, and the radial key function of the radial key mechanism 22 is not inhibited. Therefore, even if there is a difference in thermal expansion between the core barrel and the core block,
It is possible to avoid abnormal situations such as the core block shifting due to the elongation of the core barrel. Furthermore, since the radial key mechanism 22 between the core barrel 6 and the restraining ring plates 16 and 17 is disposed at an intermediate position between the band segments 11 on the circumference, it is possible to avoid interference with the band segments and to avoid interference with the cylindrical core barrel inner wall surface. and the radial key 2 between the band segment and the band segment.
1 can be secured. In addition, in this core restraint mechanism, the restraint band, band support member 13, and restraint ring plate for each stage are mutually assembled in advance outside the pressure vessel, and this assembly is lowered into the pressure vessel to connect the core block and core barrel. It is installed between.

【Effect of the invention】

As described above, according to the present invention, the core restraint mechanism is formed by a restraint band formed by interconnecting a plurality of band segments arranged in a ring shape so as to surround the outer periphery of each layer of the core block and tighten the core block. , a restraint ring plate disposed above and below the restraint band with the restraint band in the center, and connected to each band segment interconnection portion of the restraint band on its circumference via a radial key mechanism, and an adjacent band. By comprising a radial key mechanism that mutually connects the restraining ring plate and the core barrel at the intermediate position of the mutually connecting parts of the segments, there is no imbalance in the stretch of the restraining band during normal conditions, not only when the restraining band breaks. Even when this occurs, the excessive unbalanced tension generated in the restraining band can be absorbed by the restraining ring plate, thereby preventing excessive load from acting on the radial key mechanism between the core barrel and the core barrel. In addition, this allows the function of the radial key between the core barrel and the core barrel to be maintained at all times, and even if there is a difference in thermal expansion between the core block and the core barrel during reactor operation, the core block will be able to maintain interlayer interaction due to the elongation of the core barrel. Abnormal situations such as misalignment can be reliably avoided. In addition, it is possible to secure installation space for the radial key mechanism between the core barrel and the core barrel without the conventional space constraints, and there are advantages such as being able to install a sufficiently strong radial key here. can get.

[Brief explanation of drawings]

1 to 4 show a core restraint mechanism according to an embodiment of the present invention, in which FIG. 1 is a partial plan view of main parts showing an assembled state, and FIGS. 2 and 3 are respectively similar to FIG. 1. 4 is a partial external perspective view, and FIG. 5 is a partial longitudinal side view showing the core structure of a high-temperature gas-cooled reactor.
FIG. 6 is a cross-sectional view showing a part of the core structure of FIG. 5, and FIG. 7 is a partial plan view showing the detailed structure of a conventional core restraint mechanism. 1...fuel block, 2...movable reflector, 3...
... Fixed reflector, 4 ... Side shield, 5 ... Pressure vessel, 6 ... Core barrel, 8 ... Restraint band, 11
... band segment, 12 ... connection pin between band segments, 13 ... band support member,
16, 17... Restriction ring plate, 18, 20... Radial key groove, 19, 21... Radial key.

Claims (1)

[Claims] 1 A core restraint mechanism for a nuclear reactor that tightens and fixes a core block, which is a stacked assembly of fuel blocks, reflector blocks, etc., with a core barrel disposed on the inner periphery of a pressure vessel, which A restraint band is formed by interconnecting a plurality of band segments in a ring shape, which are arranged to surround the outer periphery of each layer and tighten the core block; A restraint ring plate coupled to each band segment interconnection portion of the restraint band via a radial key mechanism on the circumference, and between the restraint ring plate and the core barrel at an intermediate position between the interconnection portions of adjacent band segments. A nuclear reactor core restraint mechanism characterized by comprising a radial key mechanism that interconnects the two.