JPS58214891A - Fast breeder - 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 The present invention relates to a fast breeder reactor, and more particularly, to a fast breeder reactor suitable for improving earthquake resistance.

A fast breeder reactor has a reactor core built into a reactor vessel and a rotating plug provided at the top of the reactor vessel. The rotating plug is provided with an upper core mechanism consisting of a control rod drive device, a fuel exchanger, and the like.

Since it is necessary to rotate the rotating plug when changing fuel,
The upper core mechanism and the core are not connected.

Therefore, in the event of an earthquake, the horizontal shaking between the upper core mechanism and the core is relatively different, and the relative displacement between them becomes large. Therefore, it is difficult to insert control rods into the reactor core during an earthquake.

As a solution to this problem, it has been proposed to engage the lower end of the connecting cylinder fixed to the rotating plug with the upper end of the core, thereby reducing the relative displacement in the horizontal direction between the core and the upper core mechanism. In this plan, the relative displacement in the horizontal direction is reduced. However, during fuel exchange, it is necessary to lift the rotating plug in order to release the coupling cylinder from the core.
Replacing fuel becomes a hassle.

An object of the present invention is to provide a fast breeder reactor in which fuel exchange is easy and control rods can be easily inserted into the reactor core during an earthquake.

A feature of the present invention is that a rod is provided that penetrates the rotary plug and whose lower end portion removably engages with the core structure, and that a drive means is provided that moves the rod up and down.

A preferred embodiment of the present invention will be explained based on FIGS. 1, 2, and 3. A fast breeder reactor 1 includes an inlet nozzle A/3 and an outlet nozzle 4 for IJum (coolant). The reactor vessel 2 has a rotary plug 5 rotatably attached to the upper end of the reactor vessel 2, and a reactor core 6 disposed within the reactor vessel 2. Although not shown, the reactor core 6 is composed of a large number of fuel assemblies and neutron shields. The fuel assembly and the neutron shield are supported by a core lower support plate 7. The core lower support plate 7 is fixed to the reactor vessel 2 by a support member 8. There are two types of fuel assemblies. This is a core fuel assembly containing PU, which is a fissile material, and a blanket fuel assembly consisting of natural uranium.

A large number of core fuel assemblies are arranged in approximately 1,000 parts of the reactor core 6, and many blanket fuel assemblies are arranged to surround the area. A number of neutron shields form the outer periphery of the core 6 and surround the outside of the area where the blanket fuel assemblies are located. Such a core 6 exists in a cylindrical core barrel 9 installed on a core lower support plate 7 . The core top support plate 10 is provided at the upper end of the core barrel 9 .

A control rod drive 12 is installed on the rotating plug 5. An upper control rod guide tube 13 extending downwardly from each control rod drive 12 is also attached to the rotating plug 5 . The upper control rod guide tubes 13 are connected by a support plate 14, fixed to the rotating plug 5, and arranged in a joint shell 15. The upper core mechanism is composed of the control rod drive device 12, the upper control rod guide tube 13, the joint shell 15, the fuel exchanger (not shown), and the like. On the outside of the jacket 15 and in its quarters, support lugs 20 are provided, as shown in FIG. Each of the support lugs 2° is provided with a thrust guide 21.

A lower guide tube (not shown) facing each upper control rod guide tube 13 is arranged within the reactor core 6 . The insertion amount of the control rods into the reactor core 6 is adjusted by operating the control rod drive device 12 to move the control rods within the upper and lower control rod guide tubes.

A vibration damping device 16 is provided on the rotating plug 5 . The vibration suppressing device 16 includes a plurality of connecting rods 17 and a jacking device 18. The connecting rod 17 passes through the rotating plug 5 and reaches into the reactor vessel 2 . As shown in FIG. 4, the connecting portion 19 at the lower end of the connecting rod 17 is
The cross-sectional area is decreasing. The connecting rod 17 passes through the strado guide 21. Although not shown, a ball screw is provided at the upper end of the connecting rod 17 (above the rotary plug 5). A bellows (not shown) is provided in the through hole of the connecting rod 17 of the rotary plug 5, and the connecting rod 17 also passes through this bellows. The upper end of the bellows is the connecting rod 1
7, the lower ends of the bellows are respectively attached to rotating plugs 5. The bellows prevents radioactive materials within the reactor vessel 2 from leaking to the outside through the annular gap between the rotating plug 5 and the connecting rod 17. Although not shown, the jack-up device 18 consists of a pole nut and the aforementioned pole nut rotation device.

The pole nut meshes with a screw thread provided on the connecting rod 17.

During normal operation of the fast breeder reactor, the connecting rod 17 is pushed down by the action of the jack-up device 18, and its connecting portion 19 is inserted into the recess 11 provided in the core top support plate 10 as shown in FIG. It is inserted like this. 4 connecting rods 1
7 improves the rigidity of the core 6 by engaging with the recess 11 . That is, even if an earthquake occurs during normal operation, horizontal shaking of the reactor core 6 is suppressed by the engaged connecting rods 17. Therefore, the relative displacement between the reactor core 6 and the upper core mechanism during an earthquake is significantly reduced.

A control rod that has been completely withdrawn from the reactor core 6 can be easily inserted into the reactor core 6.

Refueling is performed by completely inserting all control rods into the reactor core 6, and then separating the control rods and control rod drive device 12. At this time, the pole nut of the jack-up device 18 is rotated by the rotating device, and the connecting rod 17 that engages with the pole nut moves upward. The connecting portion 19 of the connecting rod 17 is pulled out from the recess 11, and the connecting rod 17 and the core top support plate 10 are separated. Fuel exchange is performed in this state. The rotating plug 5 is rotated and the fuel exchanger is
It is moved onto the fuel assembly to be replaced in the core 6. Since the connecting rod 17 and the core top support plate 10 are separated,
The rotating plug 5 can be easily rotated. The fuel exchanger takes out a predetermined fuel assembly to the outside of the reactor vessel 2. A new fuel assembly is put into the reactor vessel 2 by the fuel exchange machine,
This fuel assembly is loaded at the location where the fuel assembly taken out from the core 6 was.

When the fuel exchange is completed, the rotary plug 5 is rotated to a predetermined position that allows the connecting rod 17 and the recess 11 to engage. This position can be detected by a tachometer or the like of the rotary plug 5. Thereafter, the connecting rod 17 is pushed down by the jack-up device 18, and its connecting portion 19 is inserted into the recess 11. That is, the connecting rod 17 and the core top support plate 10 are engaged.

According to this embodiment, the earthquake resistance of the core structure, that is, the fuel assembly, the neutron shield, the core barrel, etc., can be improved as well as the control rods can be easily inserted into the reactor core 6 during an earthquake. This allows the fast breeder reactor to be completely shut down even in the event of an earthquake, improving safety.

Further, since the rotary plug 5 can be easily rotated simply by raising the connecting rod 17, fuel exchange becomes easy.

It is also easy to engage the connecting rod 17 with the recess 11 after the fuel exchange is completed. Only the connecting rod 17 is moved up and down, and the structure of its driving device is also simple.

Although a pole nut and a screw were used as the driving device for moving the connecting rod 17 up and down, other structures can also be applied. That is, a piston is provided at the upper end of the connecting rod 17 -1
This piston may be inserted into a cylinder and the connecting rod 17 may be moved up and down by pressurized gas supplied into the cylinder. Alternatively, a rack may be provided at the upper end of the connecting rod 17, and the connecting rod 17 may be moved by a pinion that meshes with the rack.

In the embodiment described above, the lower end of the connecting rod 17 was engaged with the core top support plate 10, but the lower end of the connecting rod 17 was connected to the upper end of the neutron barrier body disposed on the outer periphery of the reactor core 6. It may also be engaged with the link hole.

According to the present invention, the horizontal relative displacement between the rotary plug and the reactor core during an earthquake can be significantly reduced with a simple structure, and fuel exchange is also facilitated.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a fast breeder reactor that is a preferred practical example of the present invention, FIG. 2 is a cross-sectional view of I[-It in FIG. 1, and FIG. 3 is a cross-sectional view of Figure 4 is an enlarged view of part ■ in Figure 1. 1...Fast breeder reactor, 2...Reactor vessel, 5...Rotating plug, 6...Reactor core, 9...・Core tank, 10...
Core top support plate, 11... recess, 12... control rod drive device, 13... upper control rod guide tube, 15... joint shell, 16... vibration suppression %/figure penalty 2 figure/ '/ ■Figure 3 Figure 4-Figure

Claims (1)

[Claims] 1. A reactor vessel, a rotating plug provided at the upper end of the reactor vessel, a core structure disposed within the reactor vessel, and a reactor provided on the rotating plug above the core structure. A fast breeder reactor comprising an upper core structure located in the reactor core, the fast breeder reactor having a rod penetrating the rotating plug and removably engaged with the core structure, and having means for vertically moving the rod. fast breeder reactor. ,