JPS6056289A - Support structure of reactor core structure - 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] This invention relates to a support structure for a core structure for a gas-cooled nuclear reactor. This figure shows the core structure support structure of the high temperature gas reactor. In the figure, 1 is a core consisting of a fuel body and a movable reflector, 2 is a high-temperature plenum, 3 is a fixed reflector, and 4 i
d, a hearth insulation part, and a core structure 5 which is an assembly of these parts is supported on a diagrid 8 supported on the bottom of a reactor pressure vessel 7 via a core support plate 6. Note that 9 is a primary coolant outlet pipe that penetrates the pressure vessel 7 and the hearth insulation part 4 and opens into the high-temperature plenum part 3;
10 is an inlet pipe, 11 is a core restraint machine 1'f surrounding the outer periphery of the core structure 5, and 12 is a core barrel. Here, each of the elements 1 to 4 constituting the core structure 5 is a laminated assembly of ceramic blocks made of graphite or the like, and is laminated and constructed on the core support plate 6 when assembling the reactor. . On the other hand, the core support plate 6 is a metal plate made of chromium molybdenum steel, and its shape is a flat disk.

With the above configuration, during operation of the furnace, primary cooling gas at a low temperature of about 400° C. is introduced under pressure into the pressure vessel 7 from the inlet 10 as shown by arrow A, and flows upward through the outer peripheral area of the fixed reflector 3. It then reverses direction at the top of the reactor and flows down into each gas channel of the reactor core.

Here, the gases heated to about 1000° C. by heat exchange with the fuel body join together in the high-temperature plenum portion 2, and from there flow out of the furnace through the outlet pipe 9.

By the way, as mentioned above, the core structure 5 is made of a ceramic material such as graphite with a small coefficient of thermal expansion.
The core support plate 6 is a metal plate with a large coefficient of thermal expansion. For this reason, when the temperature inside the reactor increases during operation of the reactor, the core support plate 6 as a whole undergoes large thermal expansion in the radial direction as shown by arrows P as shown in FIG. Thermal expansion is extremely small. At this point, set 4 on top of the core support plate 6.
The ceramic blocks such as fixed reflectors, which are the components of the core structure being built, are dragged by the thermal expansion of the core support plate 6 and are individually displaced in the radial direction, resulting in each ceramic block being moved in the radial direction as shown in FIG. A gap g will be generated between the joint surfaces of the blocks.

Furthermore, as this gap I expands, a part of the primary cooling gas bypasses the normal path from the middle of the outer periphery of the core to the high-temperature plenum through the above-mentioned gap I, as shown by the arrow ′. This results in a reduction in the effective furnace gas flow rate through the fuel channel. Moreover, if the effective gas flow rate decreases, the fuel body may become abnormally heated and may be damaged. For this purpose, in the past, a core restraint mechanism 11 was provided as described in FIG. 1, and the core structure 5 was
Measures are taken to aggregate the ceramic blocks by tightening them.

By the way, the tightening force imposed on the core restraint mechanism 11 described above must be greater than the frictional force acting between the core structure 5 and the core support plate 6, but this force d, Actual sword/
The core restraint mechanism is required to be strong enough to withstand the large load of this pot and to have high long-term reliability, such as the fact that the valve cylinder has a large diameter. However, it is difficult to guarantee long-term integrity under harsh industrial conditions, including high temperatures and heat cycles due to furnace operation and shutdown, and the 8'j decision on this issue is a major appeal. Z) 0 [Object of the Invention] This invention is based on the assumption that cancer is present at the l: fteO point, and does not require a core restraint mechanism, or can reduce the load on the core restraint PA structure while It is an object of the present invention to provide a support structure for a core structure in which core structures can be skillfully aggregated against the thermal expansion of a support plate.

[Key points of the invention]

In order to achieve the above object, the core support plate is formed into a cone shape with the apex at the center of the reactor, and the core support plate is placed on the diagrid with the apex facing downward;
By stacking and constructing the core structures on the core support plate, the tilting force of the core support plate due to the core structure's own weight [component force directed toward the center along the surface, The force that gathers the ceramic blocks of the elements toward the center of the core cancels out the frictional force that acts between them and the core support plate, which tends to extend in the radial direction due to thermal expansion, and each ceramic block due to the thermal expansion of the core support plate The purpose is to prevent the positional shift of the

[Embodiments of the invention]

3 and 4 show different embodiments of the present invention, and in each embodiment, the difference from the conventional structure shown in FIG. 1 is that the core support plate 6 has a cone shape with the apex at the center of the reactor. The top of the core support plate 6 is placed on the diamond grid with the apex facing downward, and the lowest level of the main cables of the core structure 5 to be constructed on the support plate 6 is The ceramic block is made so that its bottom surface is inclined in accordance with the LfC support plate inclination angle θ. In the embodiment shown in FIG. 3, the total static friction coefficient μ between the ceramic block of the core structure 5 and the metal core support plate 6 is defined as the inclination angle θ of the support plate 6〉tam=μ, The angle is set to be larger than the friction angle between the two sides.

According to the above configuration, due to the weight of the core structure 5, each of the ceramic blocks, which are small in number, has a core support plate 6.
The force of arrow Q toward the center of the reactor core acts along the inclined surface of . The direction of this centripetal force Q is opposite to the direction of thermal expansion (arrow P) of the core support plate 6 that occurs during reactor operation, and is stronger than the frictional force that tries to drag the core structure in the direction of arrow P due to the thermal expansion of the brackets. It's also thick. Therefore, each ceramic block of the core structure 5 follows the thermal expansion of the core support plate 6, and its position does not shift as shown in FIG. 2, maintaining the aggregated state.

In this way, the gap between the bonding surfaces of the ceramic blocks does not expand, and an increase in the binocular gas flow S of the secondary cooling gas can be prevented. Moreover, in the embodiment shown in FIG. 3 in which the inclination angle θ of the core support plate 6 is set larger than the friction angle, the core restraint mechanism can be omitted.

In the embodiment of FIG. 4, the inclination angle θ of the core support plate 6 is smaller than that of the previous embodiment, and the angle θico<θ<tarrlμ
In addition to this cone-shaped support plate 6, a core restraint mechanism 11 is also used. In this embodiment, as in the case of FIG. 3, a centripetal force Q due to the weight of the core structure acts along the inclined surface of the core support plate 6. Therefore, the load sharing of the core restraint mechanism 11 is reduced by that amount, and the reliability of ensuring the integrity of the core restraint mechanism 11 is improved. Further, in this embodiment, since the inclination angle of the support plate 6 is smaller than that in FIG. 3, the cylindrical dimension is reduced, so that the space inside the furnace can be saved.

〔Effect of the invention〕

As described above, according to the present invention, the core support plate is formed into a cone shape whose plate surface is inclined downward toward the center of the reactor,
By stacking the core structure on this core support plate, the core restraint mechanism can be omitted or the load shared by the core restraint mechanism can be significantly reduced. This makes it possible to rationalize the reactor internal structure and obtain a core support structure that greatly improves the integrity of the core restraint mechanism.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the internal structure of a conventional high-temperature gas reactor, FIG. 2 is a partial plan view showing the quasi-motion of the core structure following the thermal expansion of the core support plate in FIG. 3 and 4 are structural cross-sectional views of core support structures showing different examples of the present invention. 1...Reactor core, 2...High temperature blenheim section, 3
... Fixed reflector, 4 ... Hearth insulation part, 5
...Core structure, 6... Core support plate, 8...
... Diagrid, 11... Core restraint mechanism,
P...Thermal expansion direction of the core support plate, Q...The centroid A due to the core structure's own weight Figure 2 Figure 3! :1 δ

Claims (1)

[Claims] 1) Reactor core as a stacked assembly of ceramic blocks,
In a support structure for a nuclear reactor structure in which a reactor core structure constituted by a combination of a fixed fouling body, a high-temperature plenum part, a hearth insulation part, etc. is supported on a diagrid via a metal core support plate, the above-mentioned The core support plate is formed into a cone shape with the apex at the center of the reactor, and the core support plate is placed on the dialing grid with the apex facing downward, and the core structure is laminated and constructed on the core support plate. A support structure for a nuclear reactor structure characterized by: