JPH041317B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a high temperature plenum block for a gas-cooled nuclear reactor.

[Conventional technology]

This type of high-temperature plenum block supports the stacked columns of fuel blocks that make up the core from below, and forms the upper boundary of the high-temperature plenum section that collects the primary cooling gas flowing through the core and directs it to the exit duct. A large number of them are arranged on the same plane at the bottom of the furnace vessel,
Such high-temperature plenum blocks are designed to improve the sealing performance between the blocks in order to prevent the bypass flow of cooling gas flowing into the high-temperature plenum by bypassing the normal fuel channel inside the fuel block, and to improve the seismic resistance of the core. It is desirable to be able to make key connections between blocks in order to improve performance.

First, FIG. 1 shows the hearth structure of a high-temperature gas furnace employing a conventional high-temperature plenum block, and FIGS. 2 and 3 show the combination structure of the high-temperature plenum blocks shown in FIG. 1. In each figure, 1 is a fuel block, 2 is a high-temperature plenum block made of graphite, ceramic, etc., which is the subject of this invention, and 3 is defined between the high-temperature plenum block 2 and the lower hearth insulation block 4. In the high-temperature plenum section, 5 is a pillar of the high-temperature plenum block, 6 is a fixed reflector surrounding the outer periphery of the core, 7 is a cooling gas outlet dust, and 8 is a support plate. Here, the high-temperature plenum block 2 supports seven columns of fuel blocks constituting a unit area of the core on its upper surface, and its planar shape is made into a regular hexagon, and the planar shape is made to match the channels of each fuel block. A total of seven cooling gas passage holes 9 leading to the high temperature plenum part 3 are provided in the block.
is provided. Further, a notch groove 10 is formed on the upper surface periphery of the block 2 in order to fit a sealing element therein, and a plate-shaped sealing element 11 made of graphite is formed in the notch groove 10 so as to span between adjacent blocks that are lined up on the left and right. is inserted. This seal element 1
1 to prevent a gas bypass flow from flowing into the high temperature plenum section 3 through the gap between the fuel block columns. Furthermore, adjacent blocks are interconnected via vertical radial keys 12 and key grooves 13 formed on the circumferential side, and the restraint by this radial key connection is useful for positioning when assembling high-temperature plenum blocks, and for earthquake prevention. This is intended to prevent relative positional shift of the blocks. The method of assembling the high-temperature plenum block having the above structure is to first assemble all the blocks together on the same plane while connecting them with the radial keys 12, and then install the sealing element 11 on the periphery of the upper surface between the blocks. It is arranged in such a way that

[Problem to be solved by the invention]

By the way, in order to suppress as much as possible the bypass flow of cooling gas that flows into the high-temperature plenum without passing through the normal path within the reactor core, it is necessary to improve the sealing performance between the high-temperature plenum blocks. This is an important issue. However, the seal structure in which a plate-shaped seal element 11 made of graphite is inserted into the premises across blocks as shown in the figure has a limit to its sealing performance, and the conventional seal structure in which such a seal element is provided in only one stage has a limit. It is extremely difficult to obtain sufficient sealing performance. Note that since the sealing element installation location is exposed to high temperatures during operation of the furnace, ordinary sealing members such as rubber O-rings cannot be used. From this point of view, if the above-mentioned sealing elements can be installed in multiple stages, it is possible to improve the sealing performance against the gas bypass flow between the high-temperature plenum blocks. However, if the conventional high-temperature plenum block is used as is, even if two or more upper and lower sealing elements are installed between the sides along the gap between the blocks, the sealing element and the radial key will only interfere with each other. Moreover, once the hot plenum blocks are aligned and assembled in position, it is impossible to assemble the sealing elements by inserting them from the outside into the notches cut out in the middle of the sides of the blocks.

The present invention has been made in view of the above points, and its object is to provide a high sealing performance that allows multistage sealing elements to be installed between each block of a high temperature plenum block assembly without interference with the radial key. The object of the present invention is to provide a high temperature plenum block that can be obtained.

[Means to solve the problem]

In order to achieve the above object, the present invention divides a regular polygonal high-temperature plenum block into upper and lower divided blocks that are stacked and fitted together,
In addition, a plurality of upper and lower notch grooves parallel to the periphery are formed on the circumferential side of the upper divided block, and a sealing element is inserted horizontally into the notch groove during the process of assembling the block in the furnace. Adjacent lower divided blocks of the block are connected to each other by vertical radial keys.

〔Example〕

4 to 7 show embodiments of the invention, FIGS. 4 and 5 showing the structure of one high-temperature plenum block, and FIGS. 6 and 7 showing the block and sealing elements. It shows the set assembly structure of. As shown in the figure, according to the present invention, the high-temperature plenum block 2 is first divided into upper and lower halves, which are fitted into each other by a dowel 14 with an upper divided block 2 for sealing element installation and a lower divided block 2 for radial key connection. It becomes a laminated structure. Of these, in addition to the notch groove 10 formed on the upper surface side of the block on the outer circumferential surface of the upper divided block 2 for installing a seal element, there is another notch groove 10 parallel to the notch groove 10 in the middle of the circumferential surface. Two notch grooves 15 are formed. On the other hand, in the lower divided block 2, vertical radial keys 12 and key grooves 13 are alternately formed on three sides of the hexagonal outer peripheral surface.

Next, a procedure for assembling the high-temperature plenum block and sealing element of the above structure in a furnace will be described. First, only the lower divided blocks 2 are supported by the pillars 5 shown in FIG. 1 and arranged on the same plane.
Blocks are connected to each other using radial keys to position and constrain each other. Next, the upper divided block 2 is laminated on top of the lower divided block 2 by ferrule bonding. In this case, when one adjacent block is lined up, the plate-shaped sealing element 16 shown in FIG. Insert it so that it straddles the notch groove 15 of. Thereafter, proceed with the assembly work in the same manner, and while inserting the sealing element 16 between the sides of the upper divided blocks, attach all the upper divided blocks 2 to the lower divided blocks 2.
Assemble by stacking on top. Finally, the notch groove 10 on the top surface of the block spans between adjacent blocks.
The sealing element 11 is inserted from above to complete the assembly of the blocks. In this assembled state, the lower divided blocks 2 are connected to each other by a radial key 12 and are positioned relative to each other.
Therefore, the relative positioning of the upper divided blocks 2 which are in-rotated to each of the lower divided blocks 2 is also performed at the same time. Moreover, multi-stage sealing elements shown as sealing elements 11 and 16 are installed in the gaps between the high-temperature plenum blocks that form the boundary between the core fuel block and the high-temperature plenum without interfering with the radial key 12. As a result, the sealing performance against the bypass flow of cooling gas can be significantly improved compared to the conventional one-stage seal system. Although the illustrated example shows an example in which sealing elements 11 and 16 are installed in two stages, upper and lower, it is also possible to install sealing elements in three or more stages, if necessary. Regarding the radial key, the radial key 12 is inserted into the lower division block 2.
In addition to the illustrated embodiment in which a portion of the block is bulged, a keyway is formed in advance on both opposite sides of adjacent blocks, and a radial key as an independent part is inserted from above across this keyway. It is also possible to carry out the key combination between the blocks by using the key combination.

[Effects of the Invention] As described above, according to the present invention, a high-temperature plenum block is provided with an upper divided block in which a plurality of upper and lower notched grooves for installing seal elements are formed on the circumferential side thereof;
By dividing the seal into two parts with a lower divided block connecting adjacent blocks with a radial key, and stacking the two divided blocks by fitting them together, it is possible to install a sealing element that could only be installed in one stage with the conventional structure. It can be installed in multiple stages without interfering with the radial key, and thus, in addition to the seismic function provided by the radial key connection, the sealing performance between high-temperature plenum blocks can be greatly improved.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the hearth of a high-temperature gas reactor that employs a high-temperature plenum block of conventional structure, Figure 2 is a partially enlarged plan view of the assembly of high-temperature plenum blocks in Figure 1, and Figure 3 is FIG. 2 is a sectional view taken in the direction of arrows, FIGS. 4 and 5 are a partially cutaway plan view and a side view of one high-temperature plenum block showing an embodiment of the present invention, and FIGS. 6 and 7 are FIG. 7 is a partial plan view and a sectional view taken along the direction of the arrows in FIG. 6, showing an assembled state of the blocks according to the embodiment of the present invention. 1...Fuel block, 2...High temperature plenum block, 21...Upper division block, 2...Lower division block, 3...High temperature plenum section, 10,1
5... Notch groove for seal element installation, 11, 16...
Seal element, 12... Radial key, 13... Keyway, 14... Fitting ring.

Claims (1)

[Claims] 1. A high-temperature plenum block that supports the fuel block of the reactor core and forms the upper boundary of the high-temperature plenum section, and is made up of regular polygonal divided blocks in two stages, upper and lower, which are stacked and fitted together, and the upper stage is divided into upper and lower stages. A plurality of upper and lower notched grooves are formed parallel to the circumferential edge of the block, and a sealing element is inserted between the notched grooves of the adjacent high-temperature plenum blocks. A high-temperature plenum block for a gas-cooled nuclear reactor, characterized in that the divided blocks are connected to each other by vertical radial keys.