JPH0476076B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a boiling water reactor (hereinafter referred to as BWR) in which a control rod and a control rod drive mechanism can be attached and detached by mutually rotating a predetermined angle. ) related to improvements.

[Technical background of the invention] BWR uses coolant (soft water) as shown in Figure 5.
A core shroud 2 is provided inside a reactor pressure vessel 1 that accommodates a reactor, and a reactor core 5 is constructed by loading a large number of fuel assemblies 4 onto a core support plate 3 provided within this core shroud 2. . Each of the fuel assemblies 4 is made up of a large number of fuel rods housed in a rectangular cylindrical channel box, and in a plan view, they are arranged in a matrix within the core shroud 2, and are arranged in a matrix in the reactor core shroud 2. The coolant flowing upward from the bottom of the pressure vessel 1 is heated by nuclear reaction heat. Further, control rods (hereinafter referred to as CR) 6 are arranged in the reactor core 5 . As shown in FIGS. 6 and 7, this CR6 is constructed by combining four fingers 6a containing a neutron absorbing material so that the cross section is cross-shaped.
are arranged between adjacent fuel assemblies 4, with one fuel assembly for every four fuel assemblies 4. Then each CR6 is attached to the fuel assembly 4 above.
By inserting each CR6 from below between the fuel assemblies 4, the core output is controlled according to the insertion amount, and by pulling each CR6 downward from between the fuel assemblies 4, the core output is increased, and the output during reactor operation is increased. The configuration is such that control is performed.

In addition, 7 in Fig. 5 indicates each CR6 below the core 5.
A cylindrical control rod guide tube (hereinafter referred to as CR guide tube) is provided corresponding to each CR guide tube 7, and each CR6 is inserted into the CR guide tube 7 as shown in FIG.
It guides the CR6, which moves up and down during normal reactor operation. Below the reactor pressure vessel 1 is a control rod drive mechanism (hereinafter referred to as
(referred to as CRD) 8 is provided.

The upper end of the core shroud 2 is closed with a shroud head 9.
A steam separator 10 is connected to the top. This steam-water separator 10 separates the coolant vapor heated and evaporated in the core 5 into steam and water, and further above the steam-water separator 10 is a steam dryer 11 for drying the separated steam. is connected. The steam that has passed through the steam dryer 11 is sent to a generator-driving turbine outside the reactor vessel 1 through a main steam pipe (not shown).

As shown in FIG. 8, the CR guide tube 7 passes through the core support plate 3, has its upper end outer periphery supported by the core support plate 3, and further has its upper end supported by the core support plate 3.
Its rotation is prohibited by engagement with a pin 12 protruding from the upper surface of the holder. Furthermore, fuel supports 13 are formed at the four corners of the upper end of each CR guide tube 7 to support the fuel assembly 4 from below. Furthermore, a seat surface 14 is provided at the lower end of the inner peripheral surface of the CR guide tube 7 on which the lower end of the CR 6 is seated.

The CRD 8 is housed and supported in a cylindrical control rod drive housing (hereinafter referred to as CRD housing) 15, as shown in FIG. The CRD housing 15 penetrates the bottom head plate 1a of the reactor pressure vessel 1 and is welded to the bottom head plate 1a. It has a motor section 17 that drives the motor section 17.
With the CRD housing 15 exposed below,
It is attached to the lower end flange portion 15a of the CRD housing 15 with bolts or the like.

The upper end of the CRD 8 is detachably connected to the lower end of the CR 6, and there are various types of such connection mechanisms. Examples are shown in FIGS. 9a and 9b and 10a and 10b. That is, the upper end of the piston 16 of the CRD 8 is provided with a bayonet type connecting portion 18 consisting of four vertically long engaging pieces 18a arranged at equal intervals in the circumferential direction, and the outer end of each engaging piece 18a has a bayonet type connecting portion 18. A bulging portion 18b is formed. Furthermore, a support rod 18c is provided at the center of the four engagement pieces 18a to project upward, and this support rod 18c limits the amount of inward deflection of the four engagement pieces 18a. I have to. On the other hand, a recess 19a for accommodating the connecting portion 18 is provided at the lower end of the CR6, and each of the engaging pieces 18 is provided at the open end of the inner peripheral surface of the recess 19a.
The bayonet type connected portion 19 is constructed by projecting four engaging protrusions 19b at intervals in the circumferential direction as shown in FIG. When the connecting portion 18 and the connected portion 19 are connected, the bottom surface of the recess 19a comes into contact with the support rod 18c, and the weight of the CR 6 is supported by the support rod 18c.

Therefore, when attaching and detaching CR6 and CRD8, CR6 is lowered further than the operating range during reactor operation, and the lower end of CR6 is attached to the seat surface 14 of CR guide tube 7.
It is performed with the person seated on top. That is, CR
6 and the CRD 8, first, the CR 6 is seated on the seat surface 14 of the CR guide tube 7, and the piston 16 of the CRD 8 is raised. At this time, the engagement piece 18a on the CRD 8 side is inserted into the engagement protrusion 19 as shown in FIGS. 9a and 9b.
b, so that the support rod 18c passes through the recess 1.
Rotate the CRD 8 by about 45 degrees when it comes into contact with the bottom surface of the CRD 9a, and then attach each engaging piece 18a as shown in FIGS. 10a and 10b.
The bulging part 18b and the engaging protrusion 19b in the recess 19a
engage with. To release the connection between CR6 and CRD8, first connect CR6 to the seat surface 14 of CR guide tube 7.
CRD8 from the states shown in Figure 10 a and b.
Rotate about 45 times to remove each engaging piece 1 as shown in Figure 9 a and b.
The bulging portion 18b of 8a is inserted into the engaging protrusion 1 in the recess 19a.
9b, and the engaging piston 16 is lowered so that the engaging piece 18a passes through the engaging protrusion 19b.

[Problems with the background technology] In BWR, which allows the CR and CRD to be attached and detached by rotating them by a predetermined angle, the CR
When the CR fingers are lowered to a position where they are seated on the seat surface of the CR guide tube, the upper ends of the CR fingers are interposed between adjacent fuel assemblies.
Rotation is prohibited by their fuel assemblies, but
Each finger is thin and long (about 4m)
Therefore, when a rotational force is applied to the lower end portion when attaching and detaching from the CRD, twisting tends to occur, which poses problems in workability and soundness during attaching and detaching.

[Object of the Invention] The present invention was made based on the above circumstances, and its object is to enable the attachment and detachment of CR and CRD by mutually rotating them by a predetermined angle.
In BWR, when attaching and detaching CR and CRD,
The objective is to prevent the CR from twisting even when a rotational force is applied to the lower end of the CR, thereby improving workability during attachment and detachment and the soundness of the CR.

[Summary of the Invention] In order to achieve the above objects, the present invention provides a CR that is inserted into and pulled out of the reactor core to control output during reactor operation, and a CR that is inserted into the inside of the reactor and used to move up and down during reactor operation. A CR guide tube has a guiding function for the operating CR and has a seat surface on the lower end for seating the CR, and is connected to the lower end of the CR to raise and lower the CR inside the CR guide tube during reactor operation. Attachment/detachment is performed by rotating the CR by a predetermined angle relative to the CR with the CR seated on the seat surface of the CR guide tube. It is configured to include an engaging portion and an engaged portion that are provided so as to be able to fit in the concave and convex portions from the direction, and prohibit rotation of the CR when the CR and the CRD are attached and detached.

[Embodiment of the Invention] FIGS. 1 to 4 show an embodiment of the present invention, and FIG. 1 shows a schematic configuration of a BWR. That is, a core shroud 102 is provided inside a reactor pressure vessel 101 that accommodates a coolant (soft water), and a large number of fuel assemblies 104 are loaded onto a core support plate 103 provided within this core shroud 102. A reactor core 105 is configured. Each of the fuel assemblies 104 is made up of a large number of fuel rods housed in a rectangular cylindrical channel box, and in a plan view they are arranged in a matrix within the reactor core shroud 102. The coolant flowing upward from the bottom of the pressure vessel 101 is heated by nuclear reaction heat. Further, a CR 106 is disposed in the control rod of the reactor core 105. This CR10
6 is made by combining four fingers containing a neutron absorbing substance so that the cross section is cross-shaped.
The four fingers are interposed between adjacent fuel assemblies 104 to form four fuel assemblies 10.
They are arranged at a ratio of 1 to 4. and each
By inserting the CR 106 from below between the fuel assemblies 104, the core output is controlled according to the insertion amount, and by pulling each CR 106 downward from between the fuel assemblies 104, the core output is increased. The structure is such that output control is performed during reactor operation.

In addition, 107 in the figure indicates each area below the core 105.
Cylindrical shape corresponding to each CR106
This CR guide tube 107 is for each CR10
6 is inserted into the interior to guide the CR 106 which moves up and down during normal reactor operation. A CRD 108 is provided below the reactor pressure vessel 101 to drive the CR 106 up and down.

The upper end of the core shroud 102 is closed with a shroud head 109, and a steam separator 110 is connected above the shroud head 109. This steam-water separator 110 separates the coolant vapor heated and evaporated in the core 105 into steam and water, and further above the steam-water separator 110 is a steam dryer 111 for drying the separated steam. is connected. The steam that has passed through the steam dryer 111 is sent to a generator-driving turbine outside the reactor vessel 101 through a main steam pipe (not shown).

The CR guide tube 107 penetrates through the core support plate 103, has its upper end outer periphery suspended by the core support plate 103, and has its upper end engaged with a pin protruding from the upper surface side of the core support plate 103. Its rotation is prohibited. Furthermore, fuel supports are formed at the four corners of the upper end of each CR guide tube 107 to support the fuel assembly 104 from below. moreover
A seat surface 112 is provided at the lower end of the inner peripheral surface of the CR guide tube 107, as shown in FIG. 2, on which the lower end of the CR 106 is seated. In addition, CR guide tube 10
A locking portion 113 is provided at the lower end portion of 7.

The CRD 108 passes through the bottom head plate 101a of the reactor pressure vessel 101 and is connected to the bottom head plate 101a.
Cylindrical CRD housing 114 welded to
It is supported by accommodation. The locking portion 113 of the CR guide tube 107 is introduced into the CRD housing 114 from above.

The CRD 108 has a locked portion 116 at the upper end of an outer tube 115 that fits into the inner periphery of the CRD housing 114.
The locking portion 113 of the CR guide tube 107 constitutes a bayonet connection mechanism that can be freely engaged and detached from each other. The CRD 108 further includes a piston 117 that moves up and down within the outer tube 115, and a motor section 118 (see FIG. 1) that drives the piston 117 up and down. , is attached to the lower end flange portion of the CRD housing 114 with bolts or the like.

At the upper end of the piston 117 of the CRD 108,
A bayonet type connecting portion 119 is provided which is made up of four vertically elongated engaging pieces 119a arranged at equal intervals in the circumferential direction, and a bulging portion 119b is formed at the tip of the outer surface of each engaging piece 119a. . Furthermore, a support rod 119c is provided in the center of the four engaging pieces 119a to protrude upward, and this support rod 119c
The amount of inward deflection of the book engagement piece 119a is limited. On the other hand, a recess 120a for accommodating the connecting portion 119 is provided at the lower end of the CR 106, and four engaging protrusions are provided at the open end of the inner peripheral surface of the recess 120a to correspond to each of the engaging pieces 119a. The bayonet type connected portion 120 is configured by projecting the portions 120b at intervals in the circumferential direction. When the connecting portion 119 and the connected portion 120 are connected, the bottom surface of the recess 120a comes into contact with the support rod 119c, and the weight of the CR 106 is supported by the support rod 119c.

As shown in FIGS. 2 to 4, an engaging portion 121 consisting of one or more convex portions (the figure shows an example with two convex portions) is provided on the outer peripheral portion of the lower end of the CR 106. ing. On the other hand, at the lower part of the CR inner tube 107, the engaging portion 12 of the CR 106 is provided.
A cylindrical portion 12 is located at a position surrounding the location where 1 is provided.
2, and on the inner circumferential surface of this cylindrical portion 122, an engaged portion 123 consisting of the same number of concave portions as the convex portions and corresponding to each convex portion of the engaging portion 121 is provided. These engaging portions 121 and engaged portions 123
means that the CR106 is connected to the CR guide pipe 107 as shown in Figure 2.
When lowered to a position where they are seated on the seat surface 112, they are in a relationship in which they fit into each other from above and below.

Therefore, to attach and detach CR106 and CRD108,
This is carried out with the CR 106 lowered further than the operating range during reactor operation and with the lower end of the CR 106 seated on the seat surface 112 of the CRD guide tube 107. That is, to connect the CR 106 and the CRD 108, first the CR 106 is seated on the seat surface 112 of the CR guide tube 107, and the piston 117 of the CRD 108 is raised. At this time CRD10
The engagement piece 119a on the 8th side passes between the engagement protrusions 120b, and the support rod 119c is inserted into the recess 120a.
When the CRD 108 comes into contact with the bottom surface of the CRD 108, the CRD 108 is rotated approximately 45 degrees to engage the bulging portion 119b of each engagement piece 119a with the engagement protrusion 120b in the recess 120a. To disconnect the CR 106 and CRD 108, first seat the CR 106 on the seat surface 112 of the CR guide tube 107, rotate the CRD 108 by about 45 degrees, and align the bulge 119b of each engagement piece 119a with the recess.
20a from the engagement protrusion 120b, and remove the engagement piece 1.
The engagement piston 117 is lowered so that the engagement piston 19a passes between the engagement protrusions 120b.

And in this way CR106 and CRD108
When attaching and detaching the CR 106, the lower end of the CR 106 is prohibited from rotating due to the engagement between the engaging portion 121 and the engaged portion 123, so even if the CRD 108 is rotated relative to the CR 106, the lower end of the but
It does not rotate following the CRD 108 and does not cause twisting or the like. Therefore, CR1
The workability when attaching and detaching the CRD 108 to the CRD 108 is improved, and the soundness of the CR 106 is also improved.

In addition, in the above embodiment, the engaging portion 1 on the CR106 side
21 is a convex portion, and the engaged portion 12 on the CRD 108 side
Although 3 is a recessed portion, the relationship between the protruding portion and the recessed portion may be reversed. Further, the number of these convex portions and concave portions can also be set arbitrarily.

[Effects of the Invention] As detailed above, according to the BWR of the present invention, the lower end of the CR and the upper end of the CR guide tube are provided so that the CR and the CR guide tube can be engaged with each other from above and below.
CR
Even if rotational force is applied to the lower end of the CR when attaching and detaching the CR and the CRD, the CR will not be twisted.
It is possible to improve workability during attachment and detachment and the soundness of the CR.

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment of the present invention, in which Figure 1 is a cross-sectional view showing the schematic configuration of a BWR, Figure 2 is a cross-sectional view of the area around the connection between the CR guide pipe and the CRD, Fig. 3 is a cross-sectional view of Fig. 2, Fig. 4 is a perspective view showing the relationship between the engaging part of the CR and the engaged part of the CR guide tube, and Figs. 5 to 10 explain the background art. Figure 5 is a cross-sectional view showing the schematic configuration of the BWR, Figure 6 is a cross-sectional view of Figure 8, and Figure 7 is a cross-sectional view showing the schematic configuration of the BWR.
The figure is a cross-sectional view of Fig. 8, and Fig. 9 a is a cross-sectional view of CR.
A cross-sectional view showing the disconnected state from the CRD, Figure b is a - cross-sectional view of Figure a, Figure 10 a is the CR and CRD
Figure b is a cross-sectional view taken from figure a. 105...Reactor core, 106...CR (control rod), 1
07...CR guide tube (control rod), 108...CRD
(control rod drive mechanism), 112... seat surface, 121
...Engaging part, 123...Engaged part.

Claims (1)

[Scope of Claims] 1. A control rod that is inserted into and pulled out of the reactor core to control output during reactor operation, and a guide function for the control rod that is inserted into the core and moves up and down during reactor operation. and a control rod guide tube having a seat surface on which a control rod is seated at its lower end; and a control rod guide tube connected to the lower end of the control rod so that the control rod is raised and lowered inside the control rod guide tube during reactor operation;
The control rod is attached to and detached from the control rod by rotating the control rod at a predetermined angle with respect to the control rod while seated on the seat surface of the control rod guide tube. The lower end of the rod guide tube is provided with an engaging part and an engaged part that are provided so as to be able to engage with each other in a concave and convex manner from above and below, and that prohibit rotation of the control rod when the control rod and the control rod drive mechanism are attached or detached. A boiling water reactor characterized by: 2. The boiling point according to claim 1, wherein a convex portion is provided at the lower end of the outer periphery of the control rod to serve as the engaging portion, and a concave portion is provided at the upper end of the control rod guide tube to serve as the engaged portion. Water reactor.