JPH02281199A - Refuelling device for nuclear reactor - Google Patents

Abstract

PURPOSE:To prevent enlarging a whole plant size and to improve a safety by providing a fuel transfer machine which covers from a center of a reactor core fuel region to an outer side, in a slit of an upper mechanism of the reactor core, which is dug downwardly and rotatably against a rotary plug. CONSTITUTION:An upper structure 4 of a reactor core is rotated within a rotary plug 3 ad a fuel handling tool 17 of a fuel transfer machine 5 is moved within a slit 4c of the mechanism 4 to position at right above a spent fuel rod. After a driving mechanism 15 is operated to grip a fuel rod, and the fuel rod is lifted up into the handling tool 17, the handling tool 17 is moved to the outer most side of the slit 4c to rotate the mechanism 4, and the fuel rod is temporarily loaded data relaying point 8 in a reactor core fuel region. Then, the handling tool 17 is moved, a refuelling machine 6 is also moved to a position right above the relaying point 8 by rotating the plug 3, the fuel rod is gripped 6a by rotating an off-set arm 6b and the fuel rod is housed in a pod 9 by rotating the plug 3 again. As such a relaying point 8 is provided and the refuelling machine 6 with an off-set arm is used, a diameter of the plug 3 can be reduced to smaller than the maximum outer diameter of the reactor core, and also as the slit 4 is rather short, a leakage can be easily prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a nuclear reactor fuel exchange system, and in particular to a nuclear reactor fuel suitable for application to a liquid metal cooled fast breeder reactor. Relating to a switching device.

(Prior art) In a liquid metal cooled fast breeder reactor, a core upper mechanism and a fuel exchange device are attached to a shielding plug that closes the upper end of the reactor vessel, and this fuel exchange device moves core components such as fuel assemblies into the reactor. It is configured so that it can be moved within the tank to perform fuel exchange, etc. By the way, as nuclear reactors become larger, the core becomes larger in diameter and the number of core components increases.
The structures of fuel exchange devices and the like tend to become more complex.

For example, the currently planned refueling system for large nuclear reactors is to install three rotating plugs (large, medium, and small) one on top of the other, with one direct-acting fuel exchange system mounted on the small rotating plug. Two large and small rotating plugs are installed one on top of the other, and a direct acting or offset arm type fuel exchange device is installed on the small rotating plug, and an offset arm type fuel exchange device is installed on one rotating plug. things are known.

Among these, the triple rotating plug direct-acting fuel exchange system has the drawback that the structure of the rotating plug in the upper part of the reactor is complicated and large, and the reactor upper structure has to be enlarged just for fuel exchange. This also applies to the dual-rotating plug direct-acting fuel exchange system. In addition, the type 2 rotating plug blade type and single rotation plug type that have an offset arm have the disadvantage that as the reactor becomes larger, the length of the offset arm increases, which reduces the lifting capacity for removing core components. there were.

In order to solve these points, for example,
75 and JP-A No. 59-151098,
An elongated slit is provided on a single rotating plug, and a direct-acting fuel transfer machine is run in the direction of this slit, and the rotation of the rotating plug is used in combination to handle core components in the entire core area. Efforts are being made to simplify the reactor superstructure.

(Problems to be Solved by the Invention) However, even in the above-mentioned rotary plug having a slit with a fuel exchanger attached thereto, the following problems still remain that need to be solved.

That is, in order to cover the entire area of the reactor core with a transfer device provided on the single-rotation plug, the single-rotation plug becomes large, which necessitates an unnecessary enlargement of the reactor upper structure. Furthermore, since the fuel transfer device runs within the long and narrow slit, a complicated sealing structure is required to shield radiation from inside the reactor and prevent leakage of radioactive gas.

The purpose of the present invention is to prevent the entire nuclear reactor from increasing in size due to the increase in the size of the rotating plug, and to have a shielding and sealing structure that is highly reliable even when the fuel transfer device runs in a long and narrow slit. The object of the present invention is to provide a miniaturized nuclear reactor refueling device that can perform the following steps.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a fuel exchange device for a nuclear reactor having a core upper mechanism vertically installed above a reactor core housed in a reactor vessel in which a plug is attached. In addition to this, there is a rotating plug that forms part of the plug and is rotatable coaxially with the core, a core upper mechanism that is rotatably installed vertically with respect to the rotary plug, and a core upper mechanism that is vertically rotatable with respect to the rotary plug. A slit provided in the vertical direction including the radius, a fuel transfer machine provided within the slit and movable from the center of the core to the outermost core fuel region in the core, and the outermost core fuel region. The reactor is equipped with relay points set at at least two locations, and a fuel exchanger with an offset am installed vertically and rotatably with respect to the rotating plug outside the upper core mechanism.

(Function) No matter where the fuel is located in the core fuel area, the rotation of the upper core mechanism and the movement of the fuel transfer device are used to bring the fuel transfer device directly above it and pull it up. Afterwards, it can be transported to a relay point. The fuel transferred to the relay point can be transferred out of the reactor core using both the rotation of the rotary plug and the operation of the refueling machine. For core components located outside the core fuel area of the reactor core, a refueling machine is brought directly above the core components using a combination of the rotation of the rotating plug and the operation of the refueling machine, and the components are then lifted out of the core. can do.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a nuclear reactor to which this embodiment is applied, and in FIG. 1, the upper opening of the reactor vessel 1 is covered with a fixing plug 2. In FIG. A reactor core 7 is housed in the reactor vessel 1 . Most of the interior of the reactor vessel 1 is filled with a liquid metal coolant 13, such as liquid sodium, in which the reactor core 7 is immersed, and a space 14 above this is filled with a cover gas, such as argon.

A rotary plug 3 is airtightly attached to the center of the fixed plug 2 so as to be rotatable with respect to the fixed plug 2. A core upper mechanism 4 is airtightly attached to the rotary plug 3 so as to be rotatable relative to the rotary plug 3, and extends to near the upper surface of the core 7. A fuel transfer device 5 is attached to the upper core mechanism 4 . Further, near the outer periphery of the rotary plug 3, a fuel exchanger 6 is installed so as to extend to near the upper surface of the reactor core 7.

In the core fuel region occupying the center of the reactor core 7, a relay point 8 is set near the outer periphery thereof, and a pot 9 is provided near the outer surface of the reactor core 7.

Figure 2 shows the fuel transfer machine 5 and fuel exchange machine 6 for the core 7.
In Fig. 2, the reactor core 7 is a hexagonal reactor core in which mainly fuel rods and other core components are arranged in the center. There is a fuel region 10, and a blanket and a neutron shield are arranged in a region 11 outside the core fuel around the fuel region 10. The relay point 8 is set at a position occupying one corner of the hexagon of the core fuel region 10.

The core upper mechanism reactor interior 4a covers the core fuel region 10, and is provided with a notch 4b cut out at a part of its outer periphery so as to span the corner of the core fuel region 10.

Further, a vertical slit 4c is provided in the core upper mechanism reactor interior 4a, extending radially from the center toward the notch 4b, and the main part of the fuel transfer device 5 is inserted into this slit 4C.

A fuel exchanger 6 is set at a point near the outer circumference of the rotary plug 3, and a fuel gripping portion 6a can be rotated around the main body 6C by an offset arm 6b. The length of the offset arm 6b is determined so that it can reach the relay point 8 or the pot 9 installed beside the outer side of the reactor core 7 when used in conjunction with the movement.

FIG. 3 is a sectional view showing the details of the fuel transfer device 5 together with the main parts of the core upper structure 4 to which it is attached. In FIG. 3, a drive device 1 is mounted on the upper surface of a core upper mechanism upper plate 4d attached to a rotating plug 3 (not shown).
5, and a shielding layer 16 having a radiation and heat shielding function is provided on the lower surface.

The main parts of the fuel transfer device 5 are provided further below the shielding layer 16, and will be described below in conjunction with FIG. 4, which shows a sectional view taken along the line A=A in FIG. 3.

As shown in FIG. 4, a fuel handling tool 17 is housed in a slit 4c provided in the reactor interior 4a of the upper core mechanism. Note that the slit 4C has a narrow slit width as shown by reference numeral 4e on the bottom surface of the core upper mechanism reactor interior 4a.

From the drive device 15, a drive shaft 18 passes through the shielding layer 16.
a and 19a are suspended and transmitted into the slit 4c through gear devices 20 and 21, respectively, movement of the fuel handling tool 17 along the guide rail 23 in the direction of the arrow in FIG. 3, and vertical movement of the gripper 22. It is designed to make you do this. Note that the reference numeral 24 in the figure indicates a guide tube of the control rod drive device.

The details of the connection part of the fuel handling tool 17 to the drive part are as shown in FIG. For example, a screw shaft 18'b connected to the drive shaft 18a via a gear device 20 using a bevel gear is screwed to the upper end of the fuel handling device 17.

The details of the vertical movement drive section of the gripper 22 are as shown in FIG. 6. For example, as shown in FIG. The boss 26 provided in is combined,
A drive shaft 27, which is threadedly connected to the gripper 22, is connected to the boss 26 via a gearing 28, for example a bevel gear.

The details of the gripping part such as the fuel rod at the tip of the gripper 22 are as follows.
As shown in FIGS. 7 and 8, the main body 32 can be moved up and down. A pawl 33 is attached to the tip of the main body 32 by a support shaft 36, and a cam follower 34 disposed on the outside of the pawl 33 is in contact with a cam track 35 fixed to the outer cylinder 29.

FIG. 7 shows a state in which the gripper 22 has reached the lowest end and is in contact with a stopper 31 provided at the tip of the drive shaft 27, and the tips of the claws 33 are closed. When the drive shaft 27 continues to rotate in the direction of lowering the gripper 22, as shown in FIG. The tip of the claw 33 is opened by moving the claw 33. Note that reference numeral 37 in FIGS. 7 and 8 is a locking mechanism for the pawl 33.

Next, the effect of this will be described.

After the reactor has been operated for a certain period of time, when the spent core components such as spent fuel rods disposed in the core fuel region 10 are taken out of the reactor core 7, rotation of the upper core mechanism 4 with respect to the rotary plug 3; Using the operation of the drive device 15 to move the fuel handling tool 17 of the fuel transfer device 5 within the slit 4C, the fuel handling tool 17 is positioned directly above the spent fuel rod to be removed in the core fuel region. Then, operate the drive device 15 to lower the gripper 22, grip the spent fuel rod with the claws 33 opened at the lowest position as described above, and then raise the gripper 22 to remove the spent fuel rod. It is pulled up into the fuel handling equipment 17. At this time, since the width of the slit 4c is narrowed at the lowest portion 4e to about the diameter of the fuel rod, the fuel rods located around it are prevented from floating as the fuel rod to be removed is pulled up.

Next, the fuel handling tool 17 is moved to the outermost side of the sleeve 4c, the core upper mechanism 4 is rotated relative to the rotating plug 3, the fuel handling tool 17 is moved directly above the relay point 8, and the gripper 2
2 is lowered, the held spent fuel rods are temporarily loaded into the relay point 8 in the core fuel region 10.

After moving the fuel handling tool 17 inside the slit 4c, the rotary plug 3 is rotated to connect the fuel exchanger 6 to the relay point 8.
The offset arm 6b is rotated to position the fuel gripping part 6a directly above the relay point 8, and the spent fuel rods that have been moved and stored in the relay point 8 are taken out by the fuel exchanger 6, and the offset arm 6b is rotated. After rotating the fuel gripping part 6a to a position where it is outside the core upper mechanism reactor interior 4a, rotate the rotary plug 3 again, and when the fuel exchanger 6 approaches the pot 9, rotate the offset arm 6b. For example, the spent fuel rods held by the fuel exchanger 6 can be stored in the pot 9.

Further, core components arranged outside the core fuel region 10 of the reactor core 7, such as blanket fuel assemblies, can be directly taken out using the fuel exchanger 6 and placed in the pot 9.

These core components housed in the pot 9 are taken out of the reactor vessel 1 by an unillustrated extraction device.

According to this embodiment, a relay point is provided within the core fuel area, and the removed fuel is transported out of the core from this relay point using a fuel exchanger with an offset arm suspended from a rotating plug. , the diameter of the rotating plug can be made smaller than the maximum outer diameter of the core, and there is no need to make the rotating plug eccentric to the center of the core, so a small and simple rotating plug is sufficient. The outer size of the furnace can be kept small.

In addition, since the linear movement range of the fuel transfer device is within the outer diameter of the inside of the reactor in the upper core mechanism, there is no shielding means to prevent radiation that passes through the slit required for movement of the fuel transfer device from leaking out of the reactor vessel. Since it can be accommodated within the outer diameter of the core upper structure, this can be easily achieved by providing a shielding means fixed to the core upper structure that also serves as a radioactive gas seal.

〔Effect of the invention〕

According to the present invention, even if the reactor becomes larger and the reactor core diameter increases, it is possible to avoid enlarging the outer shape of the reactor due to an increase in the size of the reactor upper mechanism. Regardless, it is possible to provide a highly reliable nuclear reactor fuel exchange device that functions reliably for radiation shielding in the upper direction of the reactor and for leaking gas sills.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing a planar arrangement of an embodiment of the present invention, and FIG. 3 shows details of the fuel transfer device in FIG. 4 is a sectional view taken along the line A-A in FIG. 3, and FIGS. 5 and 6 are details of the main parts of the fuel handling tool in FIG. 3. FIGS. 7 and 8 are cross-sectional views showing details of the gripper shown in FIG. 6, respectively. 1...Reactor vessel 2...Plug 3...
Rotating plug 4... Core upper mechanism 40...
Slit 5...Fuel transfer machine 6...Fuel exchange machine 7...Core 8...Relay point
1o...Reactor fuel area agent Patent attorney Nori Chika Ken Yudo Daishimaru Ken Diagram

Claims (1)

[Claims] 1. In a refueling device for a nuclear reactor having a core upper mechanism vertically installed above the reactor core housed in a reactor vessel covered with a plug, a fuel exchanger that forms part of the plug and is connected to the reactor core. A rotating plug that can rotate coaxially,
The upper core mechanism is further rotatably installed vertically with respect to the rotary plug, the slit is provided in the vertical direction including the radius of the upper core mechanism, and the slit is provided in the slit from the center of the core to the a fuel transfer device that is movable up to the outermost core fuel region in the reactor core; a relay point set at at least one location in the outermost core fuel region;
A refueling device for a nuclear reactor, comprising: a refueling machine with an offset arm rotatably installed vertically with respect to the rotary plug outside the upper core mechanism.