JPH0126519B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a reactor superstructure for a liquid metal cooled fast breeder reactor.

[Technical background of the invention]

In a liquid metal cooled fast breeder reactor, a core upper mechanism and a fuel exchanger are attached to a shielding plug that closes the upper end of the reactor vessel, and this fuel exchanger moves core components such as fuel assemblies within the reactor. It is configured to perform fuel exchange, etc. By the way, as nuclear reactors become larger, the core becomes larger in diameter,
Furthermore, as the number of core components increases, the structure of fuel exchangers and the like tends to become more complex. Currently, the following structures have been developed for fuel exchangers and the like in large-scale fast breeder reactors.

The example shown in FIGS. 1 and 2 is a combination of a triple rotary plug and a direct acting refueling device.
In the figure, 1 is the reactor vessel. Inside the reactor vessel 1, a reactor core 3 composed of a large number of core components such as fuel assemblies 2, etc. is housed. Further, inside the reactor vessel 1, a liquid metal (for example, liquid sodium) 4 is accommodated as a coolant.
The upper end of the reactor vessel 1 is closed by a shielding plug 5. This shielding plug 5 includes a fixed plug 6 fixed to the reactor vessel 1, a large rotating plug 7 concentrically and rotatably attached to the fixed plug 6, and a large rotating plug 7 rotatably mounted eccentrically with respect to the large rotating plug 7. The installed medium rotation plug 8,
It consists of a small rotation plug 9 rotatably mounted eccentrically to the medium rotation plug 8. The medium-rotating plug 8 is provided with a core upper mechanism 10 at an eccentric position with respect to the medium-rotating plug 8, and by rotating the medium-rotating plug 8, the core upper mechanism 10 is moved into the core 3 as shown in FIG. It is configured so that it can be adapted upwardly. Further, a direct-acting fuel exchanger 11 is attached to the small-rotation plug 9 at a position eccentric to the small-rotation plug 9. This direct-acting fuel exchanger 11 is inserted into the reactor vessel 1 through the small rotation plug 9, and moves the reactor core components such as the fuel assemblies 2 only in the vertical direction. When exchanging fuel, the medium-rotation plug 8 and the small-rotation plug 9 are rotated to move the direct-acting refueling machine 11 in the radial direction of the reactor vessel 1, and the large-rotation plug 7 is rotated to move it in the circumferential direction. Then, the direct-acting fuel exchanger 11 lifts up the core components such as the fuel assembly 2, etc., and then rotates the large-rotation plug 7, medium-rotation plug 8, and small-rotation plug 9. Fuel assembly 2 lifted by
It is configured to move core components such as... to arbitrary positions.

Further, FIGS. 3 and 4 show an example in which a double rotary plug and an offset arm type fuel exchanger are combined. In the figure, 21 is a reactor vessel. Inside the reactor vessel 21, a reactor core 23 composed of core components such as a large number of fuel assemblies 22, etc. is accommodated. Further, a liquid metal (for example, liquid sodium) 24 is housed inside the reactor vessel 21 as a coolant. Further, the upper end of the reactor vessel 21 is closed by a shielding plug 25 . This shielding plug 25 includes a fixed plug 26 fixed to the reactor vessel 21, a large rotating plug 27 rotatably attached to the fixed plug 26 concentrically with the fixed plug 26, and a large rotating plug 27 rotatable at a position eccentric to the large rotating plug 27. The small rotation plug 28 is attached to the small rotation plug 28.
The small rotation plug 28 is provided with a core upper mechanism 29 at an eccentric position with respect to the small rotation plug 28, and is configured such that by rotating the small rotation plug 28, the core upper mechanism 29 can be made to correspond to the top of the reactor core. has been done. Also, this small rotation plug 28
A hold down plug 30 is provided at an eccentric position. An offset arm type fuel exchanger 31 is provided passing through this hold down plug 30. This offset arm type fuel exchanger 31 has a pantograph mechanism 31 at the tip.
A, the core components such as the fuel assemblies 22 are lifted by the grippers 31B, and the grippers 31B are lifted by the pantograph mechanism 31A.
It is configured so that it can be moved horizontally as well. This device rotates the large rotation plug 27 to rotate the offset arm type fuel exchanger 31 to move the offset arm type fuel exchanger 31 in the circumferential direction, and also rotates the small rotation plug 28 to move it in the radial direction. The offset arm type refueling machine 31 is moved to an arbitrary position, and the gripper 31B is moved by the pantograph mechanism 31A to move the core components such as the fuel assemblies 22, etc. within the reactor. .

[Problems with background technology]

In the above-described combination of the triple rotary plug and the direct-acting refueling machine, the direct-acting refueling machine simply lifts the core components, and its structure is simple. However, the structure of this direct-acting fuel exchanger becomes complicated in order to finely adjust the position or obtain the necessary radial stroke.

Additionally, a combination of a double rotating plug and an offset arm type refueling machine has a simple structure, but an offset arm type refueling machine has a complex structure and has moving parts inside the furnace. As a result, reliability was low, and the lifting force was low because the core components were lifted through a pantograph mechanism.

[Purpose of the invention]

It is an object of the present invention to provide a nuclear reactor upper structure in which the structure of a fuel exchanger is simple, the reliability is high, and the lifting force for the reactor core components can be sufficiently increased.

[Summary of the invention]

The reactor upper structure of the present invention includes a fixed plug fixed to the upper opening of the reactor vessel, a rotating plug attached to the fixed plug,
A core upper mechanism provided in the rotating plug, an elongated opening provided in the rotating plug, and a core component that is inserted into the reactor vessel through the opening and moves only in the vertical direction. This configuration includes a sealing mechanism that closes the space between the direct-acting fuel exchanger and the direct-acting fuel exchanger and allows movement of the direct-acting fuel exchanger.

Therefore, the moving mechanism of the refueling machine allows fine adjustment of the radial position of the refueling machine and securing the necessary stroke, and the use of a direct-acting fuel exchanger simplifies the structure and improves reliability. The pulling force of the core components can also be sufficiently large.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 5 to 8. In the figure, 51 is a nuclear reactor vessel, which is housed in a protective vessel 52. Inside the reactor vessel 51, a reactor core 54 is accommodated, which is composed of a large number of reactor core components such as fuel assemblies 53, . . . . Further, a liquid metal (for example, liquid sodium) 55 is housed inside the reactor vessel 51 as a coolant. The liquid sodium 55 then flows into the lower part of the reactor vessel 51 from the inlet pipe 56.
The outlet pipe 57 passes upward through the reactor core 54 and is heated.
It is configured to flow more easily. In addition, argon is sealed as a cover gas in the cover gas space above the liquid level of the liquid sodium 55. The upper end of the reactor vessel 51 is a shielding plug 58
It is blocked by. This shielding plug 58 includes a fixed plug 59 fixed to the reactor vessel 51, a large rotating plug 60 that is rotatably mounted concentrically to the fixed plug 59, and a large rotating plug 60 that is rotatably mounted eccentrically with respect to the large rotating plug 60. It consists of a small rotation plug 61. Note that airtightness is maintained between the fixed plug 59 and the large rotation plug 60 and between the large rotation plug 60 and the small rotation plug 61 by a freeze seal mechanism (not shown). And the small rotation plug 6
1, a core upper mechanism 62 is installed at an eccentric position as shown in FIG. By rotating the small rotation plug 61, the upper core mechanism 62 is positioned at the center of the reactor vessel 51, that is, above the core 54 during operation. The small rotation plug 61 is provided with an elongated, e.g., oval opening 61A along the radial direction of the small rotation plug 61 at a position eccentric to the center of the small rotation plug 61. A direct-acting fuel exchanger 63 is provided passing through this opening 61A. This direct-acting fuel exchanger 63 is configured to be movable along the longitudinal direction of this opening 61A by a fuel exchanger moving mechanism 64. Further, a sealing mechanism 65 maintains airtightness between the opening 61A and the direct-acting fuel exchanger. The direct-acting fuel exchanger 63 is configured to grip the core components such as the fuel assemblies 53 and move them only in the vertical direction, so that the core components such as the fuel assemblies 53 can be extracted or loaded within the reactor. has been done. The fuel exchanger moving mechanism 64 is constructed as follows. That is, a pair of rails 66 and 67 are provided on both sides of the opening 61A along the longitudinal direction of the opening 61A. A movable table 68 is slidably guided by the rails 66, 67, and is movable along the longitudinal direction of the opening 61A. On the sides of the rails 66, 67 are racks 69, 70.
is formed. The movable table 68 is provided with pinions 71 and 72, and these pinions 71 and 72 are connected to the racks 6 of the rails 66 and 67.
9 and 70, respectively. These pinions 71 and 72 are rotationally driven by drive mechanisms 73 and 74, and as these pinions 71 and 72 rotate, the movable table 68 is moved. Further, this moving table 68 is provided with fixing mechanisms 75 and 76, and these fixing mechanisms 75 and 76 are configured to fix the moving table 68 integrally with the small rotation plug 61 at an arbitrary position. There is. The above-mentioned direct-acting refueling machine 63 is attached to the moving table 68, and the direct-acting refueling machine 63 is inserted into the reactor vessel 51 through the moving table 68 and the opening 61A. ing. Further, the sealing mechanism 65 described above is configured as follows. In other words, the small rotation plug 61
Flexible members 77, 78 made of stainless steel, for example, are provided on the upper surface between the seal end plates 82, 83 and both end surfaces of the moving table 68, corresponding to both ends of the opening 61A. It is being These bellows 77, 78 have an inverted V-shaped cross section, and both ends have seal end plates 82, 83 and a moving stage 68.
is airtightly attached to the end face of the opening 6.
1A and its lower edge is a small rotation plug 6
1, and this opening 61
A is blocked. And this bellows 71,7
An inert gas, such as argon, which is the same type as the cover gas, is supplied to the inside of the reactor vessel 51 through pipes 79 and 80, and this supplied gas flows into the reactor vessel 51 through the opening 61A. The gas inside the reactor vessel 51 flows through the bellows 77 and 61A.
It is configured so that it does not flow into the inside of 78.
When the movable table 68 moves, these bellows 77 and 78 expand and contract, allowing the movable table 68 to move.

As shown in FIG. 8, during reactor operation, the direct-acting fuel exchanger 63 and the fuel exchanger moving mechanism 6
4 etc. from the small rotation plug 61, and insert the blocking plug 81 into the opening 61A of the small rotation plug 61.
The opening 61A is sealed.

When performing fuel exchange in the fast breeder reactor configured as described above, the blocking plug 81 is removed from the opening 61A of the small rotation plug 61, and the direct-acting fuel exchanger 61 is
3. Fuel exchanger moving mechanism 64 and sealing mechanism 6
Attach 5th grade. This work shall be performed in an isolated state. Then, the large-rotation plug 60 and the small-rotation plug 61 are rotated, and the direct-acting fuel exchanger 63 is moved along the opening 61A by the fuel exchanger moving mechanism 64, and the core configuration of the fuel assemblies 53 to be replaced, etc. Fixed at a position corresponding to the element's position. Then, perform the fuel exchange work. When the fuel exchange work is completed, the direct-acting fuel exchanger 63 and the fuel exchanger moving mechanism 64 are removed, and the closing plug 81 is again attached to the opening of the small rotation plug 61. Then, the inside of the opening 61A is sealed and the operation is restarted.

In this case, the position of the direct-acting fuel exchanger 63 can be finely adjusted by the fuel exchanger moving mechanism 64, and the necessary stroke can be obtained. This simplifies the structure of the sill. In addition, since a direct-acting type fuel exchanger 63 was used,
The limit of the pulling force when pulling out reactor core components such as fuel assemblies 53... is increased, and the reactor vessel 51
This makes it easier to change fuel inside the vehicle. Furthermore, this direct-acting fuel exchanger 63 has high reliability because there are no sliding parts inside the furnace.

In the above embodiment, a double rotary plug and a direct acting fuel exchanger are combined, but the present invention is not limited to this.

〔Effect of the invention〕

As explained above, in the reactor superstructure of the present invention, the direct-acting refueling machine, which is inserted into the reactor vessel and moves the reactor core components only in the vertical direction, is moved in the longitudinal direction of the opening of the rotary plug. The exchanger moving mechanism includes a pair of rails laid on a rotating plug near both side edges of the opening and whose upper surface is a sliding surface, a pair of racks formed on the side surfaces of each rail, and a pair of racks formed on the side surfaces of each rail. a movable base that is slidably provided on the sliding surface of the rail and through which the direct-acting fuel exchanger passes through the center; a pair of pinions that are attached to the movable base and mesh with each of the racks; A drive mechanism that rotationally drives a pinion to move the moving platform in the longitudinal direction of the opening along the pair of rails, and if necessary, fixing the moving platform moved by the drive mechanism to the rotating plug. It consists of a fixing mechanism.

Further, a sealing mechanism for closing the gap between the direct-acting refueling machine and the opening and allowing movement of the direct-acting refueling machine is provided, one end of each of which is connected to the moving stage, and each other end of which is connected to each edge of the opening. It consists of a pair of bellows connected to each seal end plate mounted on a rotating plug near the rotary plug, and an inert gas injected into the inside of the pair of bellows.

Therefore, the moving mechanism of the refueling machine allows fine adjustment of the radial position of the refueling machine and securing the necessary stroke, and the use of a direct-acting fuel exchanger simplifies the structure and improves reliability. The effects are significant, such as the ability to obtain a sufficiently large pullout force for the core components.

In addition, the longitudinal movement position of the opening of the moving platform is determined by the combination of the rack formed on the side of each rail and the pinion attached to the moving platform, and the rotation angle of the pinion can be precisely controlled by the drive mechanism. As a result, the longitudinal positioning accuracy of the opening in the direct-acting refueling machine is greatly improved.

[Brief explanation of drawings]

Figures 1 and 2 show a first conventional example, in which Figure 1 is a longitudinal sectional view showing the schematic structure of a fast breeder reactor, Figure 2 is a plan view of the same, and Figures 3 and 4. 3 shows a second conventional example, FIG. 3 is a vertical sectional view showing a schematic structure of a fast breeder reactor, and FIG. 4 is a plan view of the same. Figures 5 to 8 show an embodiment of the present invention, in which Figure 5 is a longitudinal sectional view showing the schematic structure of a fast breeder reactor, Figure 6 is a plan view of the same, and Figure 7 is a fuel exchanger moving mechanism. FIG. 8 is a plan view showing the configuration of the engine, and FIG. 8 is a longitudinal cross-sectional view showing the state in which the direct-acting fuel exchanger during operation, the fuel exchanger moving mechanism, etc. are removed, and the blocking plug is attached. 51...Reactor vessel, 59...Fixing plug, 60...
Large rotation plug, 61... Small rotation plug, 61A... Opening, 53... Fuel assembly, 63... Direct acting type fuel exchanger, 64... Fuel exchanger moving mechanism, 65... Seal mechanism.

Claims (1)

[Claims] 1. A fixed plug fixed to the upper opening of the reactor vessel, a rotating plug attached to the fixed plug, a core upper mechanism provided to the rotating plug, and a core upper mechanism provided to the rotating plug. a direct acting refueling machine that is inserted into the reactor vessel through the opening and moves the reactor core components only in the vertical direction; A fuel exchanger moving mechanism that moves the fuel exchanger along the longitudinal direction; and a sealing mechanism that closes a gap between the direct-acting fuel exchanger and the opening and allows movement of the direct-acting fuel exchanger. In the reactor upper structure, the fuel exchanger moving mechanism includes a pair of rails laid on the rotating plug near both side edges of the opening and having a sliding surface on the upper surface, and a side surface of each rail. a pair of racks formed on the rails, a movable base that is slidably provided on the sliding surfaces of the pair of rails and through which the direct-acting fuel exchanger passes through the center, and each of the racks that are attached to the movable base. a pair of pinions meshing with each other; a drive mechanism that rotationally drives the pair of pinions to move the moving table in the longitudinal direction of the opening along the pair of rails; and a fixing mechanism for fixing the movable base moved by the rotary plug to the rotary plug, and each of the seal mechanisms has one end connected to the movable base and each other end connected to the rotary plug near each edge of the opening. A nuclear reactor upper structure comprising a pair of bellows connected to each seal end plate attached to the reactor, and an inert gas injected into the inside of the pair of bellows.