JPH10307198A - Housing structure of control rod drive device for reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent stress corrosion cracking of housing of control rod drive shaft of a pressurized water reactor. SOLUTION: A control rod drive device for a pressurized water reactor is constituted so that a pressure housing provided connecting to a space in a reactor vessel upper lid and accepting a control rod drive shaft has a latch housing 5 and a rod housing 27 coaxially connected to this and extending upward. The lower end boss part 27a of the rod housing 27 in this case screws in the upper end part of the latch housing 5. Between the upper surface of the boss part 27a and the upper surface of the latch housing 5, a canopy seal part is formed. A plurality of connection holes connecting the canopy room 29 formed inside the canopy seal part and the inner space of the rod housing 27 are constituted of a plurality of vertical holes 31 and a plurality of horizontal holes 33 which penetrates the boss part 27a and extends.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control rod driving device for a nuclear reactor, and more particularly to a control rod driving device for a pressurized water reactor.

[0002]

2. Description of the Related Art In a pressurized water reactor, a control rod for controlling a reaction in a reactor core is inserted into and removed from the reactor core from above. The control rod drive for this has a generally cylindrical pressure housing 3 whose lower part is connected and fixed to the reactor vessel top lid 1 as shown in FIG. And This is because this type of control rod driving device extends into the interior space of the reactor vessel and is connected to the control rod, and a control rod driving shaft formed with a number of circumferential grooves formed side by side is driven by an electromagnetic force driven latch. This is because it is configured as a so-called magnetic jack-type driving device that is driven by a mechanism in the axial direction. The pressure housing 3 is formed as a pressure-resistant vessel because a high-temperature and high-pressure fluid in a reactor vessel, that is, light water, enters therein.

FIG. 9 shows a structure of a connecting portion between the latch housing 5 and the rod housing 7. The lower end of the rod housing 7 has a larger diameter and is screwed to the upper end of the latch housing 5, and the screw joint surface is sealed from the outside by a canopy seal weld 9 as described later. The latch housing 5 has built-in magnetic poles such as the raised magnetic pole 11, and a plurality of electromagnetic coils corresponding to these are arranged on the outer surface. A rod inner cylinder 13 is provided in the latch housing 5 and the rod housing 7, and contains a control rod drive shaft. FIGS. 10 to 12 more clearly show the structure of the connecting portion as an enlarged sectional view. As shown in these figures, the latch housing 5 and the rod housing 7 are joined by a threaded surface 15, and a space or cavity 17 having a relatively large cross-sectional area is defined on the canopy seal welding 9 side.
In addition, between the rod housing 7 etc. and the rod inner cylinder 13,
Light water 19, which is a reactor coolant, enters under high-temperature and high-pressure conditions, and reaches the canopy chamber 18 via the contact surface between the rod housing 7 and the lifting magnetic pole 11, the screw surface 15 and the cavity 17, where the canopy seal welding 9 Sealed by

[0004]

In the above-described control rod driving device, the joining of the rod housing and the latch housing by the screw and the canopy seal welding are performed at the time of manufacture and at the time of inspection after the start of operation of the reactor. Air is present in the canopy chamber 18 since it is performed in air. Thus, when the reactor is operated, the light water supplied into the reactor vessel enters the inside of the rod housing 7 and is replaced with air during production or inspection and maintenance (for example,
However, since the canopy chamber 18 is located in a recessed portion and has the threaded surface 15 on the entrance side, it is difficult to vent the air. The residual air in the canopy chamber 18 and the cavity 17 is eventually replaced by light water, but due to the resistance of the cavity chamber 17 and the screw surface 15, the residual air remains in the canopy chamber for a long time and enters the canopy chamber. A high oxygen concentration region is formed adjacent to the canopy seal weld in cooperation with the hot light water. Such hot water having a high oxygen concentration at a high temperature forms a corrosive atmosphere, and if it exists adjacent to canopy seal welding, which is a kind of weld, there is a possibility that stress corrosion cracking may occur in the weld. If a crack occurs, the reactor coolant leaks out therefrom, which is not preferable.

[0005]

According to the present invention, there is provided, in accordance with the present invention, a pressure housing provided in communication with a space within a reactor vessel head for receiving a control rod drive shaft. A latch housing having a built-in latch mechanism that moves by gripping, and a rod housing that is coaxially connected to the latch housing and extends upward,
A lower end boss of the rod housing is screwed to an upper end of the latch housing, and a canopy seal portion is formed between an upper surface of the lower end boss and an upper surface of the latch housing. A plurality of communication holes communicating between the canopy seal space formed inside the canopy seal portion and the space inside the rod housing are drilled through the lower end boss portion to remove residual air in the canopy seal space into the rod housing space. To make it easier to leak. In a preferred embodiment of the present invention, the communication hole is a radial hole communicating between a space formed in the rod housing and a cavity formed below the canopy seal space, An axial hole communicating with the canopy seal space. Further, in the canopy seal portion, an annular groove extending in a circumferential direction is formed in a top chamfered portion where the rod housing and the latch housing are in contact with each other, and an inclined linear hole communicating with the rod housing internal space is formed in the annular groove. Is preferably opened. Furthermore, it is also preferable that the cross section of the annular groove is formed in the same semicircular shape as the cross section of the canopy seal space, and the cross section of the canopy seal space is circular.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The same parts as those of the above-described conventional structure are denoted by the same reference numerals. First,
Referring to FIGS. 1 and 2, the upper end of the latch housing 5 forming the pressure housing of the control rod driving device has an enlarged diameter or boss 27a at the lower end of the rod housing 27.
At the screw surface 15. The upper end surface of the latch housing 5 has a semi-dome-shaped protrusion or canopy 5a.
Are protrudingly formed, and are connected to a similar canopy 27 b on the rod housing 27 side by a canopy seal weld 9. Therefore, a canopy seal space, that is, a canopy chamber 29 is defined inside the canopies 5a and 27b, but an inner corner at the upper end of the latch housing 5 is provided with an arc-shaped chamfer 5b, while the outside of the boss 27a is provided. Since the corners are also arc-shaped chamfered 27c, the upper end surface of the latch housing 5 and the boss 27a of the rod housing 27 are formed.
And cooperate with each other to form an annular groove having a semicircular cross section. For this reason, the cross section of the canopy chamber 29 is circular, forming an annular space along the outer periphery of the boss 27 a of the rod housing 27. On the other hand, an annular space or cavity 17 is formed on the canopy side of the threaded surface 15 between the boss portion 27a and the latch housing 5 in the same manner as in the conventional structure, and is formed at intervals in the circumferential direction. Multiple longitudinal communication grooves 3
1 communicates with the canopy chamber 29. Further, the cavity 17 communicates with the internal space of the rod housing 27 by a lateral communication hole 33 that is radially extended from the boss portion 27a and is spaced apart in the circumferential direction. Vertical communication groove 31
It is preferable that the horizontal communication hole 33 and the horizontal communication hole 33 have the same circumferential position. The control rod drive shaft 21 is movably housed in the inner space of the rod housing 27, and a gap 23 is formed between the outer surface of the control rod drive shaft 21 and the inner surface of the rod housing 27. Coolant comes in.

Prior to the activation of the pressurized water reactor, light water is put into the primary cooling system including the reactor vessel, and the air inside is replaced with light water. Light water also enters the latch housing 5 and the rod housing 27, and pushes out the internal air from the upper system. At this time, the air in the vicinity of the screw joint surface 15, the air in the cavity 17, and the horizontal communication hole 3
The air in the cavity 3 is also discharged, but some air in the cavity 17 and air in the canopy chamber 29 remain. Then, when the operation of the nuclear reactor starts, the coolant in the hot water state at a further increased pressure passes through the gap 23 and the like, and flows into the canopy chamber 29.
And the residual air is somewhat pressurized and the canopy chamber 29
Collect at the top of the. The manner in which such residual air is removed by the embodiment of the present invention will be described below with reference to FIG.

FIG. 3 shows a simplified flow path model of the structure shown in FIGS. The canopy chamber 29 is formed as a complete circular annular space,
The horizontal communication hole 33 is lower than the canopy chamber 29. The cavity 17 is also formed in an annular shape. Temperature T _H of the coolant hydrothermal conditions in the surrounding gap 23 of the control rod drive shaft 21 (hereinafter hydrothermal referred.) Is higher than the temperature T _C of the canopy chamber 29 from near the reactor vessel side. Therefore, a natural circulation force is generated between the two due to the temperature difference of the hot water. Gap 23
Is usually not completely uniform, so that a natural circulation of hot water occurs here. The natural circulation of this hot water is indicated by arrows in the figure. That is, the high-temperature hot water in the gap 23 flows into the cavity 17 through the horizontal communication hole 33 on the right side in the figure, rises in the corresponding vertical communication groove 31 from the cavity 17, and enters the canopy chamber 29. The hot water flows laterally in the canopy chamber 29, flows downward through the left longitudinal communication groove 31 by the thermosyphon effect, and enters the cavity 17. Furthermore, it returns inside the gap 23 and flows downward. This natural circulation of hot water contacts and dissolves the air above it in the canopy chamber 29, i.e. the residual air flows out with the hot water. If the natural circulation of the hot water proceeds to some extent, the accumulated air in the canopy chamber 29 disappears, and hot water having a normal oxygen concentration exists. In the above embodiment, the horizontal communication holes 33
Since the natural circulation flow of the hot water is generated through the longitudinal communication groove 31, the residual air in the canopy chamber can be quickly removed, and the lower part of the canopy chamber is formed in an annular groove having a semicircular cross section. In addition, the circumferential flow of the hot water is always ensured, and the reliability of the above-described air removing action is greatly increased. Therefore, it is possible to suppress the occurrence of stress corrosion cracking at the welded portion of the canopy seal, and to reliably prevent leakage of the radioactive substance.

In the above-described embodiment, the lower side of the canopy chamber is formed as an annular groove having a semicircular cross section. However, the same effect can be obtained by merely performing normal chamfering as shown in FIGS. The effect is obtained. In the figure, the rod inner cylinder 13 is inside the rod housing 127, and hot water has entered between the rod inner cylinder 13 and the rod housing 127. The upper end of the latch housing 105 is screwed into the threaded surface of the outer peripheral surface of the boss portion 127a of the rod housing 127, and the canopies 105a and 127b are sealed by welding.
9 to define an annular canopy space or canopy chamber 129. And canopy room 12
9 communicates with the cavity 117 through the longitudinal communication groove 131, which also communicates with the internal space of the rod housing 127 through the horizontal communication hole 133. Therefore, it will be apparent to those skilled in the art that the natural circulation flow of the hot water as described above also occurs in the present embodiment.

Further, instead of the horizontal communication holes 133 in the embodiment shown in FIG. 4, the inclined communication holes 23 are formed as shown in FIG.
3 may be formed on the boss 127a of the rod housing 127 in a similar circumferential arrangement. In this way, for example, the hot water flowing upward flows into the inclined communication hole 233 much more easily than entering the horizontal communication hole 133, so that the natural circulation of the hot water through the canopy chamber 129 is promoted, The accumulated air can be removed in a short period of time, and the occurrence of stress corrosion cracking can be further suppressed.

[0011]

As described above, according to the present invention,
Since the canopy seal space formed at the boundary between the rod housing and the latch housing of the control rod drive unit communicates with the internal space of the rod housing through a plurality of communication holes penetrating the lower end boss of the rod housing, the The residual air in the canopy seal space is removed by the natural circulation of the hot water composed of the coolant, and the generation time of the atmosphere having a high oxygen concentration is shortened. Therefore, the occurrence of stress corrosion cracking in the peripheral portion can be suppressed. Further, according to the present invention, since the communication hole is constituted by the radial passage and the axial passage, natural circulation is reliably generated, and the above-described effect can be further enhanced. Further, according to the present invention, by forming the communication hole by a straight straight inclined hole, the structure is simplified, the resistance of the natural circulation of hot water is reduced, and the removal of residual air is ensured. Can more effectively suppress the occurrence of stress corrosion cracking. Further, according to the present invention, since the lower portion of the canopy seal space is formed as an annular groove having a semicircular cross section, the movement of hot water by natural circulation can be ensured, and the occurrence of stress corrosion cracking in the peripheral portion is further reduced. It can be suppressed effectively.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a main part of an embodiment of the present invention.

FIG. 2 is a plan sectional view taken along the line II-II in FIG.

FIG. 3 is a simplified model diagram for explaining the operation of the embodiment.

FIG. 4 is a partial sectional view showing a main part of another embodiment of the present invention.

FIG. 5 is a plan sectional view taken along the line VV of FIG. 4;

FIG. 6 is a partially enlarged sectional view of FIG. 5;

FIG. 7 is a partial cross-sectional view showing a main part of a modified embodiment in which a part of the embodiment shown in FIG. 4 is modified.

FIG. 8 is a side view showing an example of the outer shape of the control rod driving device of the pressurized water reactor.

FIG. 9 is a cutaway perspective view showing a part of the internal structure of the control rod driving device.

FIG. 10 is a sectional view showing a main part of a housing of the conventional control rod driving device.

FIG. 11 is a plan sectional view taken along line XI-XI in FIG. 10;

12 is a partially enlarged sectional view showing a part of FIG. 10 in an enlarged manner.

[Explanation of symbols]

 Reference Signs List 5 latch housing 5a canopy 5b arc chamfer 9 canopy seal welding 15 screw face 17 cavity 21 control rod drive shaft 23 gap 27 rod housing 27a boss 27b canopy 27c arc chamfer 29 canopy chamber 31 longitudinal communication hole 33 lateral communication hole 105 latch Housing 105a Canopy 117 Cavity 127 Rod housing 127a Boss 127b Canopy 129 Canopy chamber 131 Vertical communication hole 133 Horizontal communication hole 233 Inclined communication hole

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tohru Osaki 2-1-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. 1 Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Kuniharu Ito 1-1-1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo

Claims (4)

[Claims] A pressure housing provided in communication with a space inside the upper cover of the reactor vessel for receiving a control rod drive shaft, a latch housing including a latch mechanism for gripping and moving the drive shaft, and A rod housing coaxially connected and extending upward, wherein a lower end boss portion of the rod housing is screwed to an upper end portion of the latch housing, and between an upper surface of the lower end boss portion and an upper surface of the latch housing. In the housing of the control rod driving device in which a canopy seal portion is formed, a canopy seal space formed inside the canopy seal portion, and a plurality of communication holes communicating with the rod housing space are formed at the lower end boss portion. A housing structure for a control rod drive unit for a nuclear reactor, characterized by being penetrated. 2. The communication hole includes: a radial hole communicating a space formed in the rod housing with a cavity formed below the canopy seal space; and a communication hole formed between the cavity and the canopy seal space. And an axial hole communicating with the shaft.
A housing structure of the control rod drive device for a nuclear reactor as described in the above. 3. An inclined groove extending in the circumferential direction is formed in a chamfered top portion of the canopy seal portion where the rod housing and the latch housing are in contact with each other, and the inclined groove communicates with the inner space of the rod housing. The housing structure of a control rod drive for a nuclear reactor according to claim 1 or 2, wherein a straight hole is opened. 4. The reactor according to claim 3, wherein a cross section of said annular groove is formed in the same semicircular shape as a cross section of said canopy seal space, and a cross section of said canopy seal space is circular. Control rod drive device housing structure.