JPH06324188A - Fast breeder reactor - Google Patents

Abstract

PURPOSE:To improve inserting performance of a control rod at earthquake time by restricting relative displacement by connecting the lower end part of a reactor core upper structure to the top part of a reactor core. CONSTITUTION:A circular hole necessary for nuclear reactor operation is evaded, and a fuel aggregate 12 is arranged in the top part of a reactor core 1, and a connecting recessed part 14 is arranged in the corner square part of a hexagonal pillar 6 of a control rod lower part guiding pipe 13, and a connecting projecting part 15 is arranged in the lower end part of a reactor core upper mechanism 5, and both are fitted to each other, and the reactor core upper machanism 5 is connected to the top part of the reactor core 1. As a result, the reactor core upper mechanism 5 is not vibrated at earthquake time as a hand holding beam only by support of a fixing cover 3, and horizontal directional relative displacement is restricted, so that inserting performance of a control rod is improved remarkably. Shaft directional displacement caused by a temperature change in a nuclear reactor is absorbed when the projecting part 15 moves slidingly in the recessed part 14, and when fuel is replaced, since the projecting part 15 is pulled up together with the reactor core upper mechanism 5, work space of a gripper device can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fast breeder reactor using liquid metal sodium as a coolant, and more particularly to a fast breeder reactor in which the upper core mechanism is pulled up for refueling.

[0002]

2. Description of the Related Art A liquid metal sodium-cooled fast breeder reactor for pulling up an upper core mechanism of this type to exchange fuel is
As shown in FIG. 12, the reactor core 1 is housed in the reactor vessel,
This core 1 is covered with a coolant 2 of liquid metal sodium, and has a structure in which a control rod drive mechanism 4, an upper core mechanism 5 and a refueling machine 6 are installed on a fixed lid 3 that closes the reactor vessel. There is.

Power control and shutdown of the nuclear reactor are carried out by driving a control rod guided inside the upper core mechanism 5 by a control rod drive mechanism 4 and inserting it into the core 1.
At the time of refueling, as shown in FIG. 13, first, the control rod drive mechanism 4 is removed from the core upper part mechanism 5, the elevating coupler 7 is attached thereto, and then the elevating mechanism 8 and the guide cylinder 9 are installed.

Next, the elevating mechanism 8 is used to move the upper core 5
Pull up. Then, using the space in which the core upper part mechanism 5 is pulled up, the variable arm 10 provided at the lower end of the fuel exchanger 6 guides the gripper device 11 to the upper part of the fuel rod of the core 1, and the gripper device 11 grips this fuel rod. And replace it.

[0005]

In the conventional fast breeder reactor configured as described above, when the gripper device 11 of the fuel exchanger 6 is moved to the position of each fuel rod of the core 1 at the time of refueling, Upper core mechanism 5 to core 1
Since it has to be pulled up from directly above, the structure is such that the core upper part mechanism 5 is supported only from the fixed lid 3 side.

Therefore, at the time of an earthquake, the lower end of the core upper mechanism 5 vibrates more than the upper part, and a relative positional displacement occurs between the control rod insertion hole of the core 1 and the hole guiding the control rod of the core upper mechanism 5. When this displacement is large, there is a problem that the insertability of the control rod is hindered.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fast breeder reactor having improved control rod insertability during an earthquake.

[0008]

In order to solve the above-mentioned problems, the first aspect of the present invention relates to a core housed in a reactor vessel, and guides the control rod into a control rod insertion hole of this core. In a fast breeder reactor having a core upper part mechanism provided with control rod guide holes and pulling up the core upper part mechanism to perform fuel exchange, a connecting mechanism for connecting the top part of the core and the lower end part of the core upper part mechanism is provided. It is provided.

According to a second aspect of the present invention, there is provided a core housed in a reactor vessel, and an upper core mechanism having a control rod guide hole for guiding the control rod into a control rod insertion hole of the core. In a fast breeder reactor in which the upper core mechanism is pulled up for refueling, a cylindrical body surrounding the upper core mechanism is provided, and a supporting member that supports an intermediate portion of the upper core mechanism is provided in the cylindrical body.

[0010]

In the first aspect of the present invention having the above structure, since the lower end portion of the core upper part mechanism is connected to the top portion of the core, both of them have the same displacement even at the time of earthquake, and as a result, It becomes possible to eliminate horizontal relative displacement between the control rod guide hole of the upper core mechanism and the control rod insertion hole of the core.

Further, according to the present invention, since the intermediate portion of the core upper part mechanism is supported by the supporting member provided in the cylindrical body surrounding the core upper part mechanism, the deformation of the lower end part of the core upper part mechanism is reduced even during an earthquake. As a result, the horizontal relative displacement of the core with respect to the control rod insertion hole can be reduced.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view of a fast breeder reactor including an upper core mechanism according to the first embodiment of the present invention, and FIG. 2 is shown in FIG.
3 is a perspective view showing in detail the structure of the lower end of the core upper part mechanism and the top of the core, which are the main parts of the embodiment in FIG. Note that the same or corresponding portions as those of the conventional configuration will be described using the same reference numerals as those in FIGS.

As shown in FIG. 1, in a fast breeder reactor, a reactor core 1 is housed in a reactor vessel, and the reactor core 1 is covered with a liquid metal sodium coolant 2 and has a fixed lid for closing the reactor vessel. An upper core mechanism 5 and a fuel exchanger 6 are installed at 3. Further, FIG. 1 shows a state at the time of refueling, in which an elevating coupler 7 is attached to the core upper part mechanism 5, and an elevating mechanism 8 and a guide cylinder 9 are provided.
Thus, a part of the core upper part mechanism 5 is pulled up.

As shown in FIG. 2, the core 1 is constructed by arranging a hexagonal columnar fuel assembly 12 and a control rod lower guide tube 13 in a honeycomb shape, and the control rod lower guide tube 13 serves as a control rod insertion hole. Is formed into a hexagonal prism with a circular hole 13a,
The fuel assembly 12 is a hexagonal column containing a fuel pin therein, and has a structure in which a coolant 2 for removing heat generated by a fuel rod in the core 1 flows. Therefore, the fuel assembly 1
A circular hole is formed at the top of 2 as an outlet for the coolant 2.

While avoiding the circular holes necessary for the operation of the reactor, connecting recesses 14 are formed at the top of the core 1, that is, at the corners of the hexagonal columns of the fuel assembly 12 and the lower control rod guide tube 13. , A connecting recess 14 at the lower end of the core upper mechanism 5.
There are provided a plurality of connecting convex portions 15 that fit with.

Next, the operation of this embodiment will be described.

In the above-mentioned structure, the lower end portion of the upper core mechanism 5 is restrained by fitting the connecting convex portion 15 of the upper core mechanism 5 into the connecting concave portion 14 of the upper core portion. As a result, the upper core mechanism 5 does not vibrate as a cantilever beam supported only by the fixed lid 3 during an earthquake, and the lower end of the upper core mechanism 5 always moves horizontally relative to the top of the lower control rod guide tube 13. It will never happen.

A difference in thermal expansion occurs between the upper core mechanism 5, the core 1 and other structures of the reactor due to temperature changes in the reactor during operation or shutdown of the reactor, and the lower end of the upper core mechanism 5 and the core. An axial displacement is generated at the top of No. 1, but this displacement is absorbed by the sliding of the connecting projection 15 in the connecting recess 14.

Further, at the time of refueling, when the core upper part mechanism 5 is pulled up as shown in FIG. 1, the connecting projection 15 is pulled up at the same time as the core upper part mechanism 5, so that the upper part of the core is similar to that of the conventional fast breeder reactor. The gripper device 11 of the refueling machine 6
Will be secured as a working space.

In the above embodiment, FIG. 2 shows the case where the core upper mechanism 5 guides one control rod and guides it to the control rod lower guide tube 13. However, the core upper mechanism 5 is not limited to this. A plurality of control rods may be guided. In this case, the connecting projections 15 may be installed below the control rod guide holes of the core upper mechanism 5.

As described above, according to this embodiment, the horizontal relative displacement between the upper core mechanism 5 and the lower control rod guide tube 13 which hinders the insertion of the control rod during an earthquake is eliminated, and the control rod insertability during an earthquake is improved. Remarkably improved.

FIG. 3 is a perspective view showing in detail the structure of the lower end of the core upper part mechanism and the top of the core, which is the main part of the first modification of this embodiment, and is the same as that of the first embodiment already described. Alternatively, corresponding parts will be described using the same reference numerals. The same applies to the following modified examples and examples.

In this first modification, the connecting recess 14 formed at the top of the control rod lower guide tube 13 of the core 1 is eliminated. That is, the top part of the control rod lower guide tube 13 has a cylindrical structure, and the space 13b for fitting is formed between the adjacent fuel assemblies 12. The fitting projection 16 provided at the lower end of the core upper mechanism 5 is formed into a substantially triangular shape so as to fit in the fitting space 13b. The fitting gap 13b and the fitting projection 16 constitute a connecting mechanism.

In the modification shown in FIG. 3, only the top of the control rod lower guide tube 13 has a cylindrical structure. However, the top of the control rod lower guide tube 13 and the fuel assembly 12 are shown.
Both of the tops of the cylinder are cylindrical or the fuel assembly 12
It is also possible to form only the top portion of the cylinder into a cylindrical shape and form the connection structure of the core upper part mechanism 5 in a shape matching this.

Also in this first modification, the same effects as those of the first embodiment can be obtained. Other configurations and effects are the same as those in the first embodiment, and therefore their explanations are omitted.

FIG. 4 shows a second modification of the first embodiment. In this second modification, the connecting structure of the lower end of the core upper mechanism 5 is changed to a fitting flange 17. By making the top of the control rod lower guide tube 13 lower than the top of the fuel assembly 7, a fitting space 13c is formed at the top of the core 1.

The lower end of the core upper mechanism 5 has a hexagonal flange structure, and the fitting flange 17 is fitted into the fitting space 13c at the top of the core 1 so that the lower end of the core upper mechanism 5 is fitted. And the top of the control rod lower guide tube 13 are connected. Other configurations and effects are the same as those in the first aspect.
The description is omitted because it is the same as the embodiment.

FIG. 5 shows a third modification of the first embodiment, which is a modification of the core 1 including a dummy fuel assembly 18. That is, in this third modified example, unlike the fuel assembly and the fuel rod lower guide tube in the core 1, the shape of the core apex comes from the reactor operation, etc.
For example, a dummy fuel assembly 18 is installed that is not restricted by the coolant sodium flow path and the control rod insertion hole.

The dummy fuel assembly 18 can be installed by changing the core design relating to, for example, fission reaction. At the lower end of the core upper part mechanism 5, a connecting projection 19 that is connected to the upper part of the dummy fuel assembly 18 is installed,
The connecting projection 19 is fitted on the top of the dummy fuel assembly 18. Other configurations and effects are the same as those in the first embodiment, and therefore their explanations are omitted.

FIG. 6 is a longitudinal sectional view of a fast breeder reactor including an upper core mechanism according to the second embodiment of the present invention, FIG. 7 (A),
8B is a longitudinal sectional view showing the universal joint of FIG. 6, FIG.
(A), (B) is an explanatory view showing the operation of the embodiment of FIG.

In the second embodiment, as shown in FIG. 6, a flexible universal joint 20 is provided in the middle portion of the core upper part mechanism 5. This shaft coupling 20 is shown in FIGS.
As shown in FIG. 4, the spherical shaft 22 is displaced by a predetermined angle with respect to the spherical seat 21, so that the bow-shaped deformation of the core upper part mechanism 5 is eliminated, and the core upper part mechanism at the fitting portion with the top part of the control rod lower guide tube 13 is eliminated. The angle formed by 5 and the control rod lower guide tube 13, that is, the bending angle of the hole through which the control rod is guided is reduced.

The upper part of the upper core mechanism 5 is supported by the fixed lid 3 of the reactor vessel, while the core 1 is supported from the lower part of the reactor vessel, so that both of them vibrate in different modes during an earthquake.

Therefore, when the lower end of the core upper mechanism 5 and the top of the control rod lower guide tube 13, which is the top of the core 1, are fitted to each other as in the first embodiment, the relative displacement between the two is caused during an earthquake. As a result, the core upper part mechanism 5 connecting them is deformed into a bow shape as shown in FIG. 8 (A). Here, when the flexible universal joint 20 having flexibility is inserted into the upper part of the core upper part mechanism 5, the above-mentioned bow-like deformation is eliminated as shown in FIG. 8B.

Further, comparing the case where the universal shaft coupling 20 is provided and the case where it is not provided, as shown in FIGS. 8A and 8B, when the horizontal displacement of the core 1 and the fixed lid 3 is the same, The angle at the joint between the core upper mechanism 5 and the control rod lower guide tube 8 through which the control rod passes is smaller when the joint is provided (angle a> b).

That is, when horizontal relative displacement occurs above and below the upper core mechanism 5, the spherical shaft 22 slides on the spherical seat 21, which causes the upper core mechanism 5 to bend and deform at the joint portion. As a result, the angle formed by the lower end of the core upper mechanism 5 and the top of the core 1 is smaller than that when the shaft coupling 20 is bowed.

Therefore, the factors that hinder the insertion of the control rod, such as hitting at three points, for the control rod passing therethrough during an earthquake are reduced, and the insertability of the control rod is further improved.

FIG. 9 is a longitudinal sectional view of a fast breeder reactor including an upper core mechanism according to the third embodiment of the present invention. In the third embodiment, a cylindrical body 30 surrounding the core upper mechanism 5 in the circumferential direction is installed on the bottom surface of the fixed lid 3, and a horizontal support plate 31 as a supporting member is attached to the lower portion of the cylindrical body 30. .

Therefore, by supporting the middle portion of the core upper part mechanism 5 by the horizontal support plate 31, the core upper part mechanism 5 does not vibrate as a cantilever supported by the fixed lid 3 at the time of an earthquake, but the horizontal support plate 31. Since the vibration is equivalent to that of a cantilever having a length from the supporting portion 31 to the lower end, the displacement during an earthquake is reduced.

At the time of refueling, as shown in FIG. 10, the core upper part mechanism 5 is pulled up, but since the cylindrical body 30 and the horizontal support plate 31 are out of the operating range of the refueling machine 6, a replacement work space is secured. It

FIG. 11 shows a modification of the third embodiment. In this modification, a split horizontal plate 32 is provided at the lower end of the core upper mechanism 5 in addition to the cylindrical body 30 and the horizontal support plate 31 of the third embodiment. The horizontal plates 32 are fitted together by a fitting member.

Therefore, according to this modification, by connecting the divided horizontal plates 32 to each other, the rigidity can be further enhanced and the displacement during an earthquake can be further reduced.

[0043]

As described above, according to the first aspect of the present invention.
According to the above, since the lower end of the core upper part mechanism is connected to the top part of the core, the same displacement occurs even during an earthquake, and the control rod guide hole of the core upper part mechanism and the control rod insertion hole of the core are It is possible to eliminate the relative displacement in the horizontal direction. As a result, the control rod insertability at the time of an earthquake is improved, the shutdown of the reactor at the time of an earthquake becomes more reliable, and the safety is enhanced.

Further, according to the present invention, since the intermediate portion of the core upper part mechanism is supported by the supporting member provided in the cylindrical body surrounding the core upper part mechanism, the deformation of the lower end part of the core upper part mechanism is reduced even during an earthquake. Therefore, the horizontal relative displacement of the core with respect to the control rod insertion hole can be reduced. Thereby, claim 1
Similarly to the above, the control rod insertability at the time of the earthquake is improved, the shutdown of the reactor at the time of the earthquake becomes more reliable, and the safety is improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a fast breeder reactor including an upper core mechanism according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing in detail the structures of the lower end portion of the core upper part mechanism and the top portion of the core, which are the main parts of the embodiment in FIG.

FIG. 3 is a perspective view showing in detail the structures of the lower end portion of the core upper part mechanism and the top portion of the core, which are the main parts of the first modification example of the first embodiment.

FIG. 4 is a perspective view showing in detail the structures of the lower end portion of the core upper part mechanism and the top portion of the core, which are the main parts of the second modification example of the first embodiment.

FIG. 5 is a vertical cross-sectional view of a fast breeder reactor including a core upper part mechanism showing a third modified example of the first embodiment.

FIG. 6 is a vertical cross-sectional view of a fast breeder reactor including a core upper part mechanism according to a second embodiment of the present invention.

7 (A) and 7 (B) are vertical sectional views showing the universal joint of FIG. 6.

8A and 8B are explanatory views showing the operation of the embodiment of FIG.

FIG. 9 is a vertical cross-sectional view of a fast breeder reactor including a core upper part mechanism according to a third embodiment of the present invention.

10 is a vertical cross-sectional view showing a state in which the core upper part mechanism is pulled up at the time of refueling in FIG.

FIG. 11 is a vertical cross-sectional view of a fast breeder reactor including an upper core mechanism showing a modification of the third embodiment.

FIG. 12 is a vertical cross-sectional view of a fast breeder reactor including an upper core mechanism in a conventional example.

FIG. 13 is a vertical cross-sectional view showing a state in which the core upper part mechanism is pulled up at the time of refueling in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 core 2 coolant 3 fixed lid 4 control rod drive mechanism 5 core upper mechanism 12 fuel assembly 13 control rod lower guide tube 13a circular hole (control rod insertion hole) 14 connection recess (connection mechanism) 15 connection projection ( Coupling mechanism) 20 Universal shaft joint 21 Spherical seat 22 Spherical shaft 30 Cylindrical body (cylindrical body) 31 Horizontal support plate (support member) 32 Divided horizontal plate

Front Page Continuation (72) Inventor Masakazu Jimbo 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock Company Toshiba Yokohama Office

Claims (2)

[Claims] 1. A core housed in a nuclear reactor vessel, and a core upper mechanism having a control rod guide hole for guiding a control rod into a control rod insertion hole of the core, and the core upper mechanism is pulled up. A fast breeder reactor for exchanging fuel by providing a connecting mechanism for connecting the top part of the core and the lower end part of the core upper part mechanism. 2. A core housed in a nuclear reactor vessel, and a core upper mechanism having a control rod guide hole for guiding a control rod into a control rod insertion hole of the core, and the core upper mechanism is pulled up. A fast breeder reactor for exchanging fuel by providing a tubular body surrounding the upper core mechanism, and providing a supporting member for supporting an intermediate portion of the upper core mechanism in the tubular body.