JP3028678B2 - Reactor upper mechanism of fast breeder reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor upper mechanism of a fast breeder reactor using liquid metal as a coolant.

[0002]

2. Description of the Related Art A fast breeder reactor uses fast neutrons, and the speed at which neutrons are absorbed by a nuclear source material to produce a new fission material is greater than the speed at which nuclear fuel required for a chain reaction is consumed. Since it is a furnace and takes out heat from a small core, it uses sodium, which has a good heat transport capacity, as a coolant. Since the sodium must not be exposed to the air, the reactor vessel is sealed and the liquid level is covered with an inert gas. The upper lid of the furnace is tightly sealed and serves as a shield. However, the fuel needs to be changed without opening the lid, so various measures are required.

FIG. 5 is a sectional view of a conventional fast breeder reactor.
In FIG. 5, a reactor core 1 is housed in a reactor vessel 2, and an upper part of the reactor is provided with a core upper mechanism 3, a roof deck 4 having a multilayer disk structure, a rotary plug 5, a large rotary plug driving device 6a, and a small rotary plug drive device 6a. It comprises a rotary plug drive 6b and a refueling machine 7. The upper core mechanism 3 includes a control rod guide tube and a thermocouple for measuring a coolant temperature at the outlet of the fuel assembly. The rotary plug 5 in FIG. 5 shows a double rotary plug type configuration, in which a large rotary plug driven by a large rotary plug drive 6a and a small rotary drive driven by a small rotary plug drive 6b eccentrically attached to the large rotary plug. It is composed of a plug, and the fuel operation hole can be set directly above the fuel, so that the fuel can be exchanged only by moving up and down. On the other hand, in the method using a rotating arm with a single-rotation plug, only one large rotating body is required. However, a pantograph that requires expansion and contraction and requires a horizontal motion in a furnace may be used. The rotary plug 5 is made of a layer of stainless steel, carbon steel, graphite or the like, the inside of which is cooled by nitrogen gas, and serves as a shield. Fuel in the reactor core can be accessed at all positions by a combination of the rotation angle of the rotary plug 5 and the rotation angle of the fuel exchanger 7 (or the amount of expansion and contraction of the arm).

[0004] Shielding of radiation to the upper part of the reactor during operation of the reactor or the like is performed by the shielding layer provided on the roof deck 4 having a multilayer disk structure and the rotary plug. In addition, a thermal shield layer and a cooling layer are installed at the bottom of each, and depending on the temperature distribution during reactor operation,
The roof deck 4 and the rotating plug 5 are significantly deformed,
It prevents the generation of excessive stress. Rotating plug 5
An airtight seal is maintained even between the rotary plug 5 and the roof deck 4 by an expansion seal or a fusion seal. In addition, these seal structures
If the rotary shaft of the rotary plug 5 is removed, the structure can be replaced and maintained.

[0005]

The reactor upper mechanism shown in FIG. 5 is widely adopted for a fast breeder reactor using active liquid metal (sodium) as a coolant, but has the following problems. is there. (1) The roof deck and rotary plug are multilayered structures having a shielding layer, a cooling layer, a thermal shielding layer, etc., and control the total displacement of the core upper mechanism and the core during an earthquake to a predetermined value or less. In order to ensure that the rod is inserted during an earthquake, it is necessary to have a considerably rigid structure, which results in a very heavy structure. (2) The rotary bearing structure, seal structure, and the like for rotating the rotary plug are very complicated and heavy structures, and replacement and maintenance work becomes large. As a result, it hinders an increase in the utilization rate of the power plant. (3) Since the control rod drive and the like that require maintenance and inspection when the plant is stopped are on the rotating plug that rotates when fuel is replaced, maintenance and inspection during fuel replacement are difficult to perform. As a result, it hinders an increase in the utilization rate of the power plant.

[0006] The present invention is characterized by providing a reactor upper mechanism of a fast breeder reactor capable of refueling without using a rotating plug.

[0007]

SUMMARY OF THE INVENTION In a fast breeder reactor using liquid metal as a coolant, the upper part of the reactor vessel is used as a head plate to seal inert gas and to control expansion and contraction through the head plate. A core upper mechanism comprising a rod guide tube and a support member for connecting and supporting the lower end of the control rod guide tube;
A refueling machine having a telescoping arm disposed at the center of the core upper mechanism, wherein the core upper mechanism is positioned above the core during normal operation, and the fuel core upper mechanism is separated from the upper part of the core during fuel exchange. The above object is attained by exchanging fuel by the fuel exchanger.

[0008] Further, if the core upper mechanism is moved up and down by a guide tube elevating drive device supported on the floor of the building above the reactor vessel, it is preferable to reduce the load on the head plate.

Further, it is preferable that the refueling machine is supported on the floor of the building above the reactor vessel in order to reduce the load on the head plate.

[0010]

In the present invention, the upper portion of the reactor vessel is used as a head plate to seal the inert gas and form a cover gas boundary. Equipped with a control rod guide tube that can be extended and retracted through the head plate, and at the time of refueling, the upper part of the core is pulled up by the guide tube elevating drive unit, and the arm of the refueling machine is turned and extended and separated from the upper part of the core to move the gripper throughout the core. Can be accessed. As described above, since the fuel is exchanged using the fuel exchanger and the control rod guide tube, a rotating plug can be dispensed with.

[0011]

FIG. 1 is a sectional view showing a fast breeder reactor equipped with a reactor upper mechanism according to an embodiment of the present invention in a normal operation state. In FIG. 1, the same parts as those in FIG. 5 are denoted by the same reference numerals. In FIG. 1, a reactor core 1 is housed in a reactor vessel 2. The upper part of the reactor vessel 2 is a head plate 10, and a cover gas boundary is formed by sealing an inert gas on the surface of sodium. At the upper part of the core 1, an upper core mechanism 3 is configured by a telescopic control rod guide tube 3 a and a lower plate radial key 3 b as a support member that connects the lower part of the control rod guide tube 3 a and supports it horizontally. I have. End plate 10
The control rod driving device 8 is attached to the upper part of a plurality of control rod guide tubes 3a penetrating through the control rod guide tube 3a, and the control rod driving device 8 is supported on the floor 12 of the building. The control rod guide tube 3a has a telescopic shape by removing the outer shell of the outer periphery so as to easily expand and contract. The control rod driving device 8 has a stroke corresponding to the stroke required for normal operation plus the stroke of the control rod guide tube 3a. In addition, by removing the outer shell, the overall rigidity is reduced and the control rod insertion property during an earthquake becomes unstable, but the lower end of the upper core mechanism is connected to the top of the core by the lower plate radial key 3b or the like. Thus, the restriction condition can be satisfied. The guide tube lifting / lowering drive device 11 is supported by the building floor 12, penetrates the end plate 10, and has a lower end connected to the lower plate radial key 3 b as a support member. The core upper mechanism 3 is moved up and down by a guide tube elevating drive device 11. During normal operation, the core upper mechanism 3 is located above the core 1. During normal operation, the fuel exchanger is pulled out of the reactor vessel 2. 9 is a fuel access machine.

FIG. 2 is a sectional view showing a state of the high-speed breeding passage of FIG. 1 at the time of refueling. In FIG. 2, a space is formed in the upper part of the core 1 by pulling up the upper core mechanism 3 by the guide tube raising / lowering drive device 11 and contracting the control rod guide tube 3 a, separating the upper core mechanism 3 from the upper part of the core 1. Next, a manipulator type fuel exchanger 7 is arranged at the center of the core upper mechanism 3, and the entire area of the core 1 can be accessed by turning the fuel exchanger 7 and expanding and contracting the arm 7a. In addition, the same handling is possible for the fuel exchanger 7 even with an existing pantograph type fuel exchanger.

FIG. 3 is a sectional view of the control rod driving device of FIG. In FIG. 3, reference numeral 13 denotes a lifting drive, 14 denotes a position detector, 15 denotes a control rod latch mechanism, 16 denotes a magnet for holding, 17 denotes a link, 18 denotes a ball screw for lifting, 19 denotes a sealing member, and 20 denotes a sodium scraper. Pa and 21 are grippers. The elevating drive device 13 is driven to rotate the elevating ball screw 18 to elevate and lower the extension tube 22. The link 17 is operated by exciting the holding magnet 16 to hold the extension tube 22. For the part immersed in the sodium liquid, the attached sodium is removed by the sodium scraper 20.

FIG. 4 is a block diagram of the manipulator type fuel exchanger of FIG. Reference numeral 23 denotes a body trunk, 24 denotes an inner trunk, 25 denotes an arm, 26 denotes a gripper, 27 denotes a hold-down tube, 28 denotes a gripper claw driving device, 29 denotes an arm lifting / lowering driving device, 30 denotes a gripper lifting / lowering driving device, and 31 denotes an arm expansion / contraction driving. Device, 32 is the main body turning drive, 33 is the upper joint,
34 is a crank, 35 is a ball screw for raising and lowering the arm, 36
Is the fuel top. The arm lift drive device 28 is driven to rotate the lift ball screw 34 so that the built-in inner body 24
Arm 25 connected to the inner body 24 by raising and lowering
Up and down. The arm 25 is rotated about the upper joint 33 as a fulcrum by raising and lowering the crank 34 provided on the upper joint 33 by the arm extension / contraction drive device 31. The gripper 26 is driven up and down by the gripper lifting drive device 30.

[0015]

According to the present invention, at the time of refueling, the upper portion of the core is pulled up by the guide tube raising / lowering drive device, and the arm of the refueling machine is turned and extended and retracted from the upper portion of the core to access the gripper to the entire core. Can be. By making the upper part of the reactor vessel a head plate, the total weight of the reactor can be significantly reduced as compared with the conventional roof deck and rotary plug structure. In addition, the number of maintenance items can be reduced by removing the rotary plug. In addition, if maintenance and inspection of the control rod drive device are performed in parallel at the time of refueling, the period of the periodic inspection can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a fast breeder reactor equipped with a reactor upper mechanism according to an embodiment of the present invention during normal operation.

FIG. 2 is a cross-sectional view showing a state of the fast breeder reactor of FIG. 1 at the time of refueling.

FIG. 3 is a sectional view of the control rod driving device of FIG. 1;

FIG. 4 is a configuration diagram of the fuel exchanger of FIG. 2;

FIG. 5 is a sectional view of a conventional fast breeder reactor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactor core 2 Reactor vessel 3 Core upper mechanism 3a Control rod guide tube 3b Lower plate radial key as a support member 7 Refueling machine 8 Control rod drive device 10 End plate 11 Guide tube elevating drive device 12 Building floor surface

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G21C 1/02 G21C 11/02 G21C 13/00 G21C 19/19

Claims (3)

(57) [Claims] In a fast breeder reactor using liquid metal as a coolant, an upper portion of a reactor vessel is used as a head plate to seal an inert gas, and a control rod guide tube having a number of control rods extending and retractable through the head plate. An upper core mechanism comprising a support member for connecting and supporting the lower end of the control rod guide tube; and a refueling machine having a telescopic arm disposed at the center of the upper core mechanism and having a telescopic arm. A reactor upper mechanism for a fast breeder reactor, wherein an upper mechanism is located at an upper part of a core, and at the time of refueling, the core upper mechanism is separated from an upper part of the core to exchange fuel by the fuel exchanger. 2. The reactor upper mechanism of a fast breeder reactor according to claim 1, wherein the core upper mechanism is moved up and down by a guide tube elevating drive device supported on a floor of a building above the reactor vessel. Reactor upper mechanism of fast breeder reactor. 3. The reactor upper part of a fast breeder reactor according to claim 1, wherein the fuel exchanger is supported on a floor of a building above the reactor vessel. mechanism.