JPS60231196A - Core constraint mechanism of nuclear 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 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, a set of six standard fuel blocks 1 surrounding one control block form a fuel handling area, and the outer periphery of this block is surrounded by a movable reflector block 2, a fixed reflector block 3, and a fuel handling area. A core block is constructed by stacking aggregate blocks surrounded by side shields 4 in a multi-layered manner. Such a core block is
It is constructed on a diagrid installed in the pressure vessel 5 via a hearth insulation layer, a high-temperature plenum block, etc. Now, operate the furnace. Prevents the difference in thermal expansion between the core block and the internal support structure that supports it during shutdown, or the displacement of the core block due to earthquakes, and thereby seals and cools the space between the inside of the core and the gas flow path outside. In order to prevent gas from leaking from the normal flow path, a core barrel 6 is installed on the inner circumferential side of the pressure vessel 5 surrounding the core block, and a core restraint mechanism (details of which will be described later) is attached to the core barrel 6. Tightening is fixed through. 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 piping 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 to form the core block. After flowing down the internal fuel channel and being heated to a high temperature of about 1000° C., it is discharged from the high temperature plenum to the outside of the furnace through the outlet pipe of the main cooling pipe 7. Next, the conventional structure and operation of the core restraint mechanism described above will be described. In other words, the core restraint mechanism can be roughly divided into two ring-shaped restraint bands 8, upper and lower, arranged to surround the outer periphery of each layer of the core block, and a core that restrains and supports the restraint bands 8 to the core barrel 6. It is composed of an initial tightening bag f&10 that applies initial tightening tension to the barrel band. Its detailed structure is shown in FIG.
It is arranged so as to surround the outer periphery of the The band segments 11 constituting the restraint band 8 are interconnected by pins 12 at both ends thereof, and the restraint band 8
An initial tightening device 1o for applying a tensile force to the restraining band 8 is disposed opposite to the interconnecting portion of the band segments 11 over the entire circumference of the restraining band 8. This initial tightening device 1o has a pin 1 whose tip end 13a connects the band segments 11 to each other.
The band support member 13 has a bifurcated leg 13b connected to the upper and lower ends of the band support member 1.
A removable pressurizing operation unit 14 equipped with a hydraulic cylinder is installed in a recessed space between the central part of the shield 3 and the outer wall surface of the side shield 4, and the pressurizing operation unit 14 applies an initial tightening tension. The spacer 15 is inserted into the gap between the leg portion 13b of the band support member 13 and the side shield 4 in the tightened state to maintain the tightened state. Note that the tip end 13a of the band support member 13 is connected to the core barrel 6.
The radial key 9 is fitted into the key groove of the radial key 9 projecting 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. That is, one layer of the core block is stacked and assembled, and the restraining band 8 and the band support member 1 are further attached to the outer periphery of the core block.
3 is supported by the radial key 9 on the core barrel side, first, the entire circumference of the restraint band 8 is covered, and the first part is placed between each band support member 13 and the side shield 4 on the core block side. The pressurizing operation unit 14 described above is provided. Subsequently, a predetermined hydraulic pressure is simultaneously applied to the hydraulic cylinders individually from the hydraulic system, and the restraint band 8 is applied via each band support member 13.
simultaneously from the inner circumference side over its entire circumference. 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 restraint bands 8 over the entire circumference, and if there is any local excess or deficiency of tension, Adjust the hydraulic pressure applied to the hydraulic cylinder in that area, and finally make adjustments so that the tension is uniform all around. This tightening is performed at the stage where the band support member 13 is lifted from the wall surface of the side shield 4.
The holding spacer 15 is inserted so as to completely fill the gap between the leg part 13b of 3 and the wall surface of the side shield 4, and the holding spacer 15 is fixed and held in the expanded state. As a result, one layer of the core block is covered with spacers 15. The initial force applied to the restraining band through the band support member 13 will fix the tightening.Next, the hydraulic pressure is removed from the hydraulic cylinder, and the pressurizing operation unit 14 becomes free. The unit 14 is removed and pulled upward, completing the initial tightening work for one layer of the core block.Subsequently, in the assembly process for the next layer, the previously used pressurization operation unit 1
4, perform the initial tightening of the core block using the same procedure as last 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 pressure operation units are prepared. Uni・
Prepare the throat. 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, a large radial key with sufficient dimensional strength can be used. Difficult to install. If the radial key is large, the inner diameters of the core barrel and pressure vessel must be increased accordingly. Furthermore, if an excessively 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 part will hit the side of the radial key 9 and an excessive load will be applied. In this case, there is a risk that 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 restraining band due to breakage of the hand, etc., the radial key function can be maintained at all times without the risk of excessive load being applied to the radial key mechanism. 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]

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 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 restraint band is unbalanced. The restraining ring plate absorbs the tension of the core barrel and prevents the radial key mechanism between the core barrel and the core barrel from being loaded with a load that would inhibit the radial key function.

[Embodiments of the invention]

1 to 4 show embodiments of this invention,
FIG. 1 is a partial plan view of the main parts showing the assembled state, and FIGS.
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, on the inner peripheral side of the core barrel 6, restraint ring plates 16° 1 are provided above and below the restraint band 8 with the restraint band 8 in the center.
7 are deployed. This restraining ring plate 16. On the one hand, the IT has a radial keyway 18 opened at a location corresponding to the interconnection section of each band segment 11 of the restraint band 8, and a radial key inserted therein into the pin 12 of the interconnection section. Color 19 with function
are fitted and connected to the restraining band 8 with a pin. Further, between the core barrel 6 and the core barrel 6, there is a radial keyway 20 cut out in the outer circumferential edge of the restraining ring plate and located in the middle between the interconnecting parts of adjacent band segments, and a radial keyway 20 that is cut out in the outer peripheral edge of the restraining ring plate, and the core barrel 6 They are mutually coupled via a radial key mechanism 22 consisting of a radial key 21 disposed on the inner periphery of the radial key mechanism 22. With this structure, each strip of restraint band 8 is restrained and supported by core barrel 6 in the circumferential direction while allowing thermal expansion in the radial direction via 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 not only to prevent unbalanced stretch of the restraint band during normal operation, but also to prevent accidents such as unexpected breakage of the restraint band. Even if an excessively unbalanced tension occurs, this circumferential load is received by the restraining ring plates 16 and 17 and does not reach the radial key mechanism 22 between the core barrel 6 and the core barrel 6.
The radial key function of the radial key mechanism 22 is not inhibited, so even if a difference in thermal expansion occurs between the core barrel and the core block, an abnormal situation such as the core block shifting due to the expansion of the core barrel will not occur. can be avoided. 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. Sufficient space for installing the radial key 21 can be secured between the radial key 21 and the band segment. 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 through a radial key mechanism, and an adjacent band segment. The structure includes a radial key mechanism that mutually connects the restraining ring plate and the core barrel at the intermediate position of the mutually connecting part of the restraining band, which prevents unbalanced stretching of the restraining band during normal conditions, as well as when the restraining band breaks. Even if such an unbalanced tension occurs in the restraint band, the restraint ring plate can absorb the excessive unbalanced tension generated in the restraint band, 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 move between layers 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 the drawing]

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,
Figure 5 is a partially vertical side view showing the core structure of a high-temperature gas-cooled reactor, Figure 6 is a cross-sectional view showing part of the core structure in Figure 5, and Figure 7 is a conventional core restraint mechanism. FIG. 3 is a partial plan view showing a detailed structure. 111. fuel block, 200. Movable reflector, 30. . Fixed reflector, 490. Side shield, 590. pressure vessel,
610. Core barrel, 800. Restraint band, 11. ,,
Band segment, 12. , , connection bins between band segments, 13. ,, Band support member, 16.1? ,
,, restraining ring plate, 18.20. ,,radial keyway,
19.21. ,. radial key. Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1) A core restraint mechanism for a nuclear reactor that tightens and fixes a reactor core block, which is a stacked block assembly including fuel blocks, reflector blocks, etc., with a core barrel disposed on the inner periphery of a pressure vessel, A restraint pan 1' is 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, and a restraint pan 1' that is arranged above and below the restraint band with the restraint band in the center. a restraint ring plate that is deployed and coupled to each band segment interconnection portion of the restraint band on its circumference via a radial key mechanism, and the restraint ring plate at an intermediate position between the interconnection portions of adjacent band segments; A core restraint mechanism for a nuclear reactor, comprising a radial key mechanism that interconnects the core barrel and the core barrel.