JPS59217191A - Stationary reflector of gas cooled 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 [Field of the Invention] The present invention relates to a fixed reflector that is a stacked assembly of graphite blocks constructed around the core of a gas-cooled nuclear reactor.

[Prior art and its problems]

First, an outline of the configuration of the A-warm reactor, which is a gas-cooled nuclear reactor mentioned above, will be described with reference to FIG. In the figure, l is the reactor pressure vessel, 2 is the reactor core configured as an assembly of fuel bodies and movable reflectors, 3 is the high-temperature plenum block, 4 is the hearth insulation block, and 5 is the pumps 3 and 4. A high-temperature plenum is formed in between, 6 is a core support plate, 7 is a diagonal grid that supports the core structure, 8 is an artificial vibe for gas as a primary coolant, 9 is a core that penetrates the core support plate 6 and the hearth insulation block 4. A gas outlet vibrator 10 is a fixed reflector which is the subject of this invention.As is well known, this fixed reflector 10 surrounds the reactor core and is attached to the side. Directional support: This is for supporting the radiation from the core, and is made up of a large number of graphite blocks 11 stacked vertically and circumferentially. Note that the core barrel, core restraint mechanism, control rods, etc. are omitted in the figure.

The flow path of the cooling gas during operation in the high temperature gas furnace is as follows. That is, the cooling gas enters the pressure vessel 1 through the inlet vibrator 8 at a temperature of 00° C.
While cooling the lower surface of the reactor, it spreads out to the surroundings, rises between the fixed reflector 10 and the pressure vessel 1, changes direction at the upper part of each vessel, and flows into the reactor core 2. Here, heat is exchanged with the fuel body up to about 1000℃! After being heated, it is collected in a high-temperature plenum, from where it flows out of the furnace through an exit vibe 9. The primary gas circulation is carried out by a gas blower outside the furnace, with the inlet vibrator 8 serving as a high-pressure discharge side and the outlet vibrator 9 serving as a low-pressure suction side.

By the way, in the fixed reflector lO, which is constructed as an assembly of a large number of stacked graphite blocks 11, as described above, if a gap occurs between the abutting surfaces between adjacent graphite blocks, the high-pressure side will be cooled through this gap. Some of the gas ends up bypassing the hot plenum, instead of taking the normal route to the reactor core.

Moreover, when this bypass flow occurs, a part of the low-temperature gas introduced into the pressure vessel 1 short-circuits and flows into the exit vibe, reducing the effective flow rate of the cooling gas that normally flows within the core 2. As a result, not only does the heat extraction efficiency decrease, but also heat removal from the fuel body is not performed sufficiently, which may lead to abnormal heating of the fuel body and damage to the furnace.

From this point of view, conventionally, in order to suppress the above-mentioned bypass flow as much as possible, the plane machining accuracy of the left and right and upper and lower joint surfaces 12 and 13 of each graphite plate constituting the fixed reflector 10 as shown in FIG. The method used is to increase the flow resistance of the graphite blocks, minimize gaps between the graphite blocks, and create a seal using the flow resistance. Note that in the figure, A represents the inner peripheral side, and B represents the outer peripheral side. However, this method has drawbacks such as defects. In other words, during operation of a high-temperature waste reactor, the inner circumferential surface of the fixed reflector is exposed to a high temperature of about 1000°C in contact with the reactor core, while the outer circumferential surface is exposed to a high temperature of about 400°C flowing with the outer circumferential area inside the pressure vessel. It is in contact with the gas flow and is relatively low temperature. Therefore, in the graphite block U, the amount of thermal expansion in the inner circumferential region is greater than that in the outer circumferential region. For this reason, as shown in FIG. 3, when the fixed reflector is assembled, the graphite blocks 11, which are lined up in close contact with each other as shown by the solid line, are affected by the difference in thermal expansion between the inner and outer circumferences as the furnace is operated. Since the inner peripheral edge contacts and is restrained first, on the other hand, in the outer peripheral region, the blocks are opened and displaced as shown by the dotted lines. As a result, the joint surfaces 12 of the blocks cannot be brought into sufficient contact with each other, resulting in a gap, which significantly reduces the sealing performance and increases the bypass flow rate of the cooling gas.

[Purpose of the invention]

It is an object of the present invention to provide a fixed reflector that eliminates the above-mentioned disadvantages and provides stable sealing performance against the bypass flow of cooling gas without impairing the function of the fixed reflector.

[Key points of the invention]

In order to achieve the above object, the present invention has developed a method to apply thermal expansion differentials due to temperature differences between the inside and outside of the graphite blocks that are supported during furnace operation to the inner circumferential areas of the left and right end surfaces of each graphite block adjacent to each other along the circumferential direction. Appropriate notched tapered surfaces are formed, and when the furnace is operated, the tapered surfaces come into close contact with each other between the graphite plates and seal the joint surfaces.

[Embodiments of the invention]

FIG. 4 and FIG. 5 show an embodiment of the present invention in which a part of the fixed reflector is taken out, and the graphite dots 11 arranged along the circumferential direction have their left and right sides connected to the bonding surface. 12, they are adjacent to each other with their joint surfaces facing each other. In such a structure, according to the present invention, a notched tapered surface 13 is formed in the inner circumferential region of the joint surface 12 of each dot lead block 11, so that the taper surface 13 is formed in the assembled state of the fixed reflector. A gap 14 is defined between the surfaces 13.

The inclination angle of this notch tapered surface with respect to the radial direction is determined based on the temperature distribution of the graphite block obtained from the temperature conditions of gas flowing inside and outside the graphite block 11 during operation of the furnace. While the furnace is in operation, the gap 14 is filled and the tapered surfaces 13 are brought into close contact with each other, as shown by the chain line in FIG. 5, and this portion forms a joint sealing surface.

With the above configuration, in the assembled state, each graphite block 11 forms a fixed reflector by abutting the outer peripheral areas of the bonding surfaces 12 against each other, as shown by the solid lines in FIGS. 4 and 5. It forms seven inner and outer surfaces of the fixed reflector. When the furnace starts operation from this state, the temperature of the graphite block 11 rises to the next level, and a difference in thermal expansion occurs between the inner and outer peripheral regions due to the difference in gas temperature between the inside and outside. The tapered surfaces 13 in the inner circumferential region are stably and closely attached to each other, and this portion forms a 7-round surface. Therefore, even if the gap between the outer circumferential regions of the joint surfaces 12 increases due to thermal expansion, stable sealing performance can be ensured, thereby suppressing the bypass flow of cooling gas. Moreover, according to this method, it can be easily implemented without requiring a complicated sealing member, and moreover, high reliability can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, a notched tapered surface corresponding to the difference in thermal expansion between the inside and outside is formed in the inner circumferential region of the joint surface between the left and right sides of the graphite block. Since the surfaces are in close contact with each other, stable sealing performance can be maintained between the graphite blocks, and an excellent effect can be exerted on suppressing cooling gas bypass flow during reactor operation.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of the high-temperature gas furnace, Figure 2 is a perspective view of a part of the fixed reflector in Figure 1, and Figure 3 is a conventional graphite block configuration. FIG. 4 is a perspective view of a partial configuration of a fixed reflector showing an embodiment of the present invention, and FIG. 5 is a plan view of FIG. 4. DESCRIPTION OF SYMBOLS 1... Reactor pressure vessel, 2. Reactor core, 10... Fixed reflector, 11. Graphite block O, 12. Joint surface between graphite blocks, 13. Notch tapered surface.

Claims (1)

[Claims] 1) In the fixed reflector of a gas-cooled nuclear reactor, which is a stack of graphite blocks constructed around the core, the inner peripheral side of the left and right end faces of each adjacent graphite block along the circumferential direction. A notched tapered surface corresponding to the thermal expansion difference caused by the temperature difference between the inner and outer peripheral regions of the graphite block during furnace operation is formed in the area, and the tapered surfaces are brought into close contact between the graphite blocks during furnace operation to form a bonding surface. A fixed reflector for a gas-cooled nuclear reactor, characterized in that it is designed to provide a seal.