JPH0531118B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a core structure of a fast breeder reactor.

[Technical background of the invention]

Generally, as shown in FIG. 4, a core 1 of a fast breeder reactor is composed of a number of core components such as a fuel assembly 3, a blanket 5, a neutron shield 7, a fuel rod 9, and a neutron source 11. . These core components are positioned and arranged regularly by upper and lower pads provided on the wrapper tubes of the core components.

By the way, in the core 1 of such a fast breeder reactor, core components such as the fuel assembly 3 exhibit group vibration behavior when an earthquake occurs. Due to this group vibration behavior, as shown in FIG. 5, the upper part 15 and intermediate part 17 of the wrapper tube 13 in the core component may collide with each other. Due to the collision force at that time, the upper and middle parts 15, 17
There is a risk that the core components will be damaged and the integrity of the core components will be compromised. Therefore, in order to ensure the integrity of the core components and improve the earthquake resistance of the core, it is necessary to make the upper and intermediate parts 15 and 17 sufficiently thick.

[Problems with background technology]

However, although it is possible to make the upper part part 15 of the core components such as the fuel assembly 3 have a thick wall structure, making the intermediate part part 17 have a thick wall structure increases the pitch of the core components. I will invite you. As a result, the gap between the core components increases, which may reduce the breeding performance of the fast breeder reactor. Furthermore, making the intermediate part 17 have a thick structure may increase the bending load generated on the core components due to swelling due to neutron irradiation.

[Purpose of the invention]

This invention has been made in consideration of the above facts, and provides a core structure of a fast breeder reactor that can improve the seismic resistance of the core without increasing both the pitch and bending loads of the core components. The purpose is to

[Summary of the invention]

In order to achieve the above object, the core structure of a fast breeder reactor according to the present invention includes a core structure including a lapper tube of a core component arranged outside the core among a large number of core components constituting the core of the fast breeder reactor. , has approximately the same outer diameter as the wrapper tubes of the other core components, and is configured to have a thicker wall than the wrapper tubes of the other core components, and has a thicker wall than the wrapper tubes of the core components located outside the core. This is a pipe with increased strength.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 2, inside the reactor building 21,
The reactor vessel 23 of the fast breeder reactor 20 is installed.
A reactor core 25 is housed within this reactor vessel 23 and filled with liquid metal primary coolant 26 . The reactor core 25 is
It is supported by a core support plate 29 attached to a flange 27 of the reactor vessel 23.

In addition, the upper part of the reactor vessel 23 has a fixed plug 3
1 and a rotating plug 33. These fixed plugs 31 and rotating plugs 33 shield radiation from the reactor core 25 and perform a heat insulating function. Further, the rotating plug 33 is provided with a core upper mechanism 35 equipped with a control rod drive mechanism and the like.

On the other hand, as shown in FIG.
9 and a neutron shield 41 are each sequentially loaded outside the reactor core. Further, control rods 43 are loaded between a large number of fuel assemblies 37, and a neutron source 45 is loaded at the boundary between the fuel assemblies 37 and the blanket 39. These fuel assemblies 37, blankets 39, neutron shields 41, control rods 43, and neutron sources 45 are collectively referred to as core components. A core 25 made up of these core components is separated from others by a core barrel 46.

Each core component has a hexagonal wrapper tube and is protected by the wrapper tube. Further, an upper part and an intermediate part are provided at the upper and middle parts in the longitudinal direction of the wrapper tube, and the core components are positioned by these upper part and intermediate part. In addition, in the case of the control rod 4, this wrapper tube is also called a guide tube.

A nuclear fission chain reaction is caused in the fuel assembly 37 by fast neutrons. The energy generated by this nuclear fission chain reaction heats the liquid metal primary coolant that has flowed into the reactor core 25 from the high-pressure lower plenum 47 shown in FIG. The heated liquid metal primary coolant 26 is led to an intermediate heat exchanger, and the heat is passed through the liquid metal secondary coolant and a steam generator to vaporize feed water and provide power generation.

Further, as shown in FIG. 3, the neutron shielding body 41 is constructed by housing a large number of stainless steel neutron shielding blocks 51 inside a wrapper tube 49.
This neutron shielding block 51 decelerates and absorbs fast neutrons within the reactor core 25. moreover,
The neutron shield 41 is provided with an entrance nozzle 53 and a handling head 55 integrally or integrally at the lower and upper portions of the wrapper tube 49, respectively. Neutron shielding block 51 is cooled by liquid metal primary coolant 26 entering from entrance nozzle 53 and exiting from handling head 55.

By the way, the Lampa tube 4 of this neutron shield 41
9 has a different configuration depending on the position of the neutron shield 41. That is, four layers of neutron shields 41 are loaded in the core 25 as shown in FIG. reactor core 2
Two-layer inner neutron shield 4 placed inside 5
1, the outer diameter and wall thickness of the wrapper tube 49 are formed to be approximately the same as those of the core components arranged inside the core 25, such as the fuel assembly 37. On the other hand, core 2
Two layers of outer neutron shield 4 placed outside of 5
1B, the thickness of the wrapper tube 49 is approximately 1.5 to 2 times thicker than the wrapper tube 49 of the inner neutron shield 41A. Furthermore, the outer neutron shield 41
The wrapper tube 49 of B is formed to have substantially the same outer diameter as the wrapper tube of the inner neutron shield 41A.

Generally, when an earthquake occurs, the reactor building 21 is
When the core components composing the core 25 vibrate as shown in FIG. A, the vibrations become larger as the core components located outside the core 25 are disposed. Therefore, as shown in FIG. 6, the impact force acting on the intermediate parts of the core components increases more rapidly as the intermediate parts of the core components are disposed outside the core 25.
Therefore, the earthquake resistance of the core can be improved by making the wrapper tube 49 of the outer neutron shield 41 disposed at the outermost periphery of the core 25 thick-walled and increasing its strength.

Furthermore, since fast neutrons are decelerated and absorbed by the inner neutron shield 41A, even if the wrapper tube 49 of the outer neutron shield 41B has a thick wall structure,
Swelling does not occur in the wrapper tube 49, and the bending load acting on the wrapper tube 49 does not increase. As a result, the integrity of the core can be ensured.

Furthermore, the lapper tube 4 of the outer neutron shield 41B
9 has an outer diameter that is almost the same as the outer diameter of the wrapper tube of the other core components, so there is no need to change the arrangement pitch of the core components. Therefore, not only is it not necessary to change the core layout design, but also there is no reduction in the core breeding performance.

Furthermore, since the wrapper tube 49 of the inner shield 41A has the same wall thickness as the others, swelling does not occur in the wrapper tube 49 even when irradiated with fast neutrons, and the bending load does not increase. , the health of the reactor core can be maintained.

In the above embodiment, the two-layered outer neutron shield 41B has a thick-walled wrapper tube, but the structure is not limited to two layers and may be three layers. Furthermore, when the neutron shielding body has four or more layers, the neutron shielding body having the thick-walled wrapper tube may have three or more layers.

〔Effect of the invention〕

As described above, according to the core structure of the fast breeder reactor according to the present invention, the lapper tube of the core component arranged outside the core has approximately the same outer diameter as the lapper tube of other core components, and the upper Since it is configured to have a thicker wall than the wrapper tubes of other core components, it has the effect of improving the earthquake resistance of the core without increasing the pitch and bending load of the core components.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of core components showing an embodiment of the core structure of a fast breeder reactor according to the present invention, and FIG. 2 is a longitudinal sectional view of a fast breeder reactor having a core having the core structure of FIG. 1. , Figures 3A and 3B are cross-sectional views showing the inner and outer neutron shields, respectively; Figure 4 is a layout diagram of core components in the core of a conventional fast breeder reactor;
Figure 5 is a diagram showing the vibration behavior of core components;
The figure is a graph showing changes in the impact force acting on the intermediate parts of the core components. 20...Fast breeder reactor, 25...Reactor core, 41...
Neutron shield, 41A...Inner neutron shield, 4
1B...Outer neutron shield, 49...Ratsupa tube.

Claims (1)

[Scope of Claims] 1. Among the many core components constituting the core of a fast breeder reactor, the wrapper tube of a core component located outside the core is substantially the same as the wrapper tubes of other core components. 1. A core structure for a fast breeder reactor, characterized in that the core structure has a large diameter and is thicker than a lapper tube of the other core components. 2. The core structure of a fast breeder reactor according to claim 1, wherein the core component arranged outside the core is a neutron shield. 3. The core structure of a fast breeder reactor according to claim 2, wherein the core components arranged outside the core are several layers of neutron shields located outside the core among the neutron shields.