JPH0347477B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a core seismic device for a nuclear reactor, and relates to an earthquake-resistant structure of core components constituting the core of a fast breeder reactor using liquid metal coolant. This article concerns an improved core seismic device.

[Technical background of the invention and its problems]

A fast breeder reactor that uses liquid metal as a coolant, as shown in FIG. As it passes through the four parts of the reactor core, it is overheated by the energy generated by the nuclear fission reaction and reaches a sufficiently high temperature, and is then sent to a steam generator or the like to generate electricity. As shown in FIG. 2, the core 4 section includes a number of core components such as a fuel assembly 5 having a hexagonal cross section, a control rod assembly 6, a blanket 7, a neutron source 8, and a neutron shield 9, which will be described later. It is constructed by regularly arranging pads 10 and 11 for positioning guidance. Note that the marks □, +, ○, and ◎ in FIG. 2 are symbols indicating the types of these core components 5 to 9, but do not indicate their shapes. In addition, the reactor vessel 2 supports four parts of the reactor core with a core support plate 14 attached to the flange part 13, and the upper part of the reactor vessel 2 is closed with a rotating plug 15, a fixed plug 16, etc. A core upper mechanism 17 is inserted into the plug 12 to shield radiation from the 4 parts of the core and at the same time serve as a heat insulator. The reactor vessel 2 configured in this manner is installed within the reactor building 18.

By the way, when an earthquake occurs as shown by the waveform (A) in FIG. 1, the vibrations of the reactor building 18 cause the core components 5 to 9 to vibrate in groups through the reactor vessel 2 and further through the core support plate 14. As a result, each core component 5 to 9 is connected to a lapper tube 1 as shown in FIG.
Collision caused by colliding with each other at the upper part 10 with a hexagonal cross section for positioning provided at the upper part of the control rod components (also referred to as the guide tube in particular in the case of control rod components) or the similar intermediate part 11 provided in the middle. generate force. In this case, as the strength of the earthquake increases, the collision force also increases, so if no measures are taken to prevent this, the upper parts 10 and intermediate parts of the core components 5 to 9 will be affected by the considerably large collision force. Because it is necessary to show the soundness of the patch part 11, due to the design,
There was a problem in that the wall thickness and size of the collision part were larger than necessary.

[Purpose of the invention]

In order to solve the above-mentioned conventional problems, the present invention provides a core seismic device that further improves the earthquake resistance of core components. The second purpose is to rationalize the configuration of the impact section, and the second purpose is to improve the integrity of the core by damping the vibrations of the core components during earthquakes.

[Summary of the invention]

In order to achieve the above-mentioned object, the core seismic device for a nuclear reactor according to the present invention has the entrance nozzle portions of a plurality of core components such as fuel assemblies and control rod assemblies regularly provided on a core support plate. In a nuclear reactor core in which the core components are inserted and arranged in positioning insertion holes, and the core components are surrounded by a core barrel, there is a gap between each core component and between the core components and the inner part of the core barrel. A fluid damper is disposed on the contact surface of the upper part between the parts to attenuate the collision load generated between them, and the fluid damper is a cylinder that is recessed in the part and contains a coolant inside. and a piston that is inserted into the cylinder so as to be freely retractable and has a circulation hole for circulating coolant within the cylinder, and between the protruding part of the piston located outside the cylinder and the outer surface of the part part, It consists of a ring spring wound around the body of the piston.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 4 to 7.

FIG. 4 shows the application locations of the nuclear reactor core seismic device according to the present invention. As is clear from this figure, core components such as the fuel assembly 5, control rod assembly 6, blanket 7, neutron source 8, and neutron shield 9 are regularly arranged in a hexagonal grid on the core support plate 14. In the insertion hole 20 provided with
By inserting the entrance nozzle part 21 at the lower end of the core components 5 to 9, they are regularly arranged in a self-supporting state on the core support plate 14, and the core components 5 to 9 are surrounded by a core barrel 22.
surrounded by.

And between each core component 5 to 9,
And, on the contact surface of the upper part part 10 between the core components 5 to 9 located at the outermost periphery among the arranged core components 5 to 9 and the inner part of the core barrel 21, that is, on the opposing surface thereof. A fluid damper 23 (hereinafter referred to as a damper) is provided on the surfaces to attenuate the collision load generated between them. The core components 5 to 9 have a hexagonal cross section as shown in the figure, and since the core components 5 to 9 face each other in six directions, dampers 23 are disposed on each face in the six directions. has been done. In addition, □ in Figure 5,
The +, ◎, and ◎ marks are symbols that indicate the types of core components 5 to 9, but do not indicate their shapes.

Next, the structure of the damper 23 will be explained with reference to FIGS. 6 and 7, in which the structure of the upper part part 10 is illustrated only on one side due to the axial symmetry of the structure. That is, the damper 23 includes a cylinder 24 which is narrow on the opening side and widened on the deep side, has a convex cross section, is recessed in the pad part 10, and contains the coolant 1 such as liquid metal therein; A piston 26 with an I-shaped cross section is inserted into and retracted from the cylinder 24 and has a circulation hole 25 that allows the coolant 1 to flow through the protruding portion located inside the cylinder 24, and a piston 26 located outside the cylinder 24. The ring spring 28 is wound around the body 27 of the piston 26 in a restrained manner between the protruding portion of the piston 26 and the outer surface of the pad portion 10. Furthermore, the diameter of the opening of the cylinder 24 is made substantially the same as the diameter of the body 27 of the piston 26, so that the movement direction in which the piston 26 moves in and out is constrained to move in a constant direction at all times. 29 in the figure is a stopper, and the cylinder 2 is provided so that the piston 26 is supported from the upper end of the upper part part 10.
By being buried in the upper part of the hole for forming the damper 23, the damper 23 itself moves in the axial direction of the core components 5 to 9 and is prevented from being removed.The damper 23 is attached by, for example, welding.

The structure of the damper 23 is such that it is disposed inside the core barrel 22 and, if necessary, is provided with an intermediate part in order to attenuate the collision at approximately the center of the core components 5 to 9. 11 can be similarly adopted. Of course, it is of course possible that some changes may be made to the structure of the inner part of the core barrel 22 and the intermediate part 11.

Therefore, by interposing such a damper 23 between the core components 5 to 9 and the inner side of the core barrel 22 so as to face each other, the ring spring 28 expands and contracts in the event of a collision. The piston 26 moves against the buffering effect caused by this and the flow resistance effect caused by the flow of the coolant 1 in the cylinder 24 through the circulation holes 25. Since this is a forced repelling action, the collision force is attenuated and the core components 5 to 9 can be sufficiently protected.

〔Effect of the invention〕

As described above, in the present invention, even if the core components vibrate in the lateral direction and the upper parts collide through the fluid damper in the event of an earthquake, the fluid drag of the fluid damper can be avoided. Since the spring force generates a strong resistance force against an instantaneous, short-term collision load and absorbs earthquake energy, the collision load is greatly attenuated and absorbed, and the collision force can be significantly reduced.

When the damping due to collision is increased in this way, the lateral vibrations of the core components are also greatly attenuated, and by mitigating the vibrations, the stress generated in the core components is also reduced, and safety is maintained.

In addition, since collisions occur between each core component and between the core components and the inside of the core barrel via dampers, the stress generated in the upper parts of the core components and the stress in the core barrel are also reduced. Not only can this be achieved, but the collision force at the intermediate part can also be expected to be alleviated by alleviating vibrations.

In addition, during normal operation, the damper, especially the bending of the core components themselves, which occurs due to the temperature difference or the difference in the irradiation amount between the opposing sides of the upper wrapper tube that has a guiding function in the core components, is Since this can be absorbed by the contraction of the ring spring, the bending stress that conventionally occurs by restraining bending can be expected to be alleviated.

As described above, according to the present invention, it is not only possible to rationalize the structure of the upper part, which is the collision part of the core components, and also the intermediate part, but also to significantly improve the integrity of the core components and the core barrel during an earthquake. In addition, it has excellent effects such as being able to relieve the stress that would otherwise occur by restraining the bending of the core components even during normal operation, and improving the integrity of the reactor during normal operation. It is something.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view to explain the configuration of the reactor, Figure 2 is a plan view showing the arrangement of the core components, Figure 3 is a side view of the main parts at the time of an earthquake, and Figure 4 is a side view of the main parts at the time of an earthquake. 7 to 7 show one embodiment of the present invention, FIG. 4 is a side view of the main part, FIG. 5 is a plan view, and FIG. 6 is a vertical cross-section of the main part of the upper part showing the structure of the damper. The top view and FIG. 7 are also cross-sectional views of the main parts. DESCRIPTION OF SYMBOLS 1...Coolant, 2...Reactor vessel, 3...High pressure plenum part, 4...Reactor core, 5...Fuel assembly, 6
...Control rod assembly, 7...Blanket, 8...
Neutron source, 9... Neutron shield, 10... Upper part part, 11... Intermediate part part, 14... Core support plate, 15... Rotating plug, 16... Fixed plug, 17... Core upper mechanism, 18...Reactor building, 19...Ratsupa tube, 20...Insertion hole, 21...
... Entrance nozzle section, 22 ... Core barrel,
23...damper, 24...cylinder, 25...
...Flow hole, 26... Piston, 27... Body, 2
8...Ring spring, 29...Stopper.

Claims (1)

[Claims] 1. Inserting and arranging the entrance nozzles of multiple core components such as fuel assemblies and control rod assemblies into positioning insertion holes regularly formed in the core support plate, and placing the entrance nozzles around these core component groups. In a nuclear reactor core surrounded by a core barrel,
On the contact surfaces of the upper part between the core components and between the core components and the inside of the core barrel,
A fluid damper is provided to attenuate the collision load generated between them, and the fluid damper includes a cylinder that is recessed in the part and contains a coolant therein, and is inserted into the cylinder so as to be freely retractable. At the same time, a ring spring is wound around the body of the piston between a piston having a circulation hole for circulating coolant in the cylinder, and a protruding part of the piston located outside the cylinder and an outer surface of the part. A nuclear reactor core seismic device characterized by comprising: