JPH0476077B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a boiling water reactor (generally known as
In particular, boiling water reactors (hereinafter referred to as BWRs) are capable of attaching and detaching control rods and control rod drive mechanisms from either side of the control rods or control rod drive mechanism. Regarding.

[Technical background of the invention] BWR uses coolant (soft water) as shown in Figure 4.
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. 5 and 6, this CR6 has four blades 6a containing a neutron absorbing material assembled in a cross-shaped cross section, and has a socket 6a at the lower end. The blades 6a are interposed between adjacent fuel assemblies 4, and are arranged at a ratio of one for every four fuel assemblies 4. and each
By inserting the CR6 between the fuel assemblies 4 from below, the core output is suppressed according to the amount of insertion, and by pulling out each CR6 downward from between the fuel assemblies 4, the core output is increased. The structure is such that output control is performed during reactor operation.

In addition, 7 in Figure 4 indicates each CR6 below the core 5.
A cylindrical control rod guide tube (hereinafter referred to as CR guide tube) is provided correspondingly 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. 7, 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 circumferential surface of the CR guide tube 7 on which the lower end of the CR 6 is seated, and at a substantially mid-height position on the inner circumferential surface of the CR guide tube 7, the seat surface 14 engages with the blade 6a of the CR6. A rotation preventing portion 7a is provided to prevent rotation of CR6.

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.
While positioned below the CRD housing 15,
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. Especially those that use a bayonet mechanism.
It is called ABWR (Advance BWR) and is the 8th
The specific structure is shown in Figures a and b and Figures 9a and b. 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 elongated engaging pieces 18a arranged at equal intervals in the circumferential direction, and the outer end of each engaging piece 18a is provided with a bayonet type connecting portion 18. Bulging part 1
8b is formed. Further, a support rod 18c is provided at the center of the four engagement pieces 18a to protrude upward, and this support rod 18c is used to connect the four engagement pieces 18a to the center.
The amount of inward deflection of 8a is limited. On the other hand, a recess 19a for accommodating the connecting portion 18 is provided in the socket 6b at the lower end of the CR6, and each of the engaging pieces 1 is provided at the open end of the inner peripheral surface of the recess 19a.
8a, four engaging protrusions 19b are protruded at equal intervals in the circumferential direction to form the bayonet type connected portion 1.
9 are configured. 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 engages the engagement protrusion 19 as shown in Fig. 8a and b.
b, so that the support rod 18c passes through the recess 1.
When it comes into contact with the bottom surface of the CRD 9a, rotate the CRD 8 by about 45 degrees to engage the protrusion 18b of each engagement piece 18a with the engagement protrusion 19b in the recess 19a, as shown in FIGS. 9a and 9b. . At this time, rotation of the CR6 is prohibited by engagement between each blade 6a of the CR6 and the rotation stopper 7a. Also, the separation from CR6 and CRD8 is
First, the CR 6 is seated on the seat surface 14 of the CR guide tube 7, and the CRD 8 is rotated approximately 45 degrees from the state shown in FIGS. is removed from the engagement protrusion 19b in the recess 19a, and the engagement piston 16 is lowered so that the engagement piece 18a passes between the engagement protrusions 19b.
Note that even when performing a detachment operation, the CR 6 is prohibited from rotating due to the engagement between each blade 6a and the rotation stopper 7a.

[Problems with the background technology] In the conventional BWR, the CR and CRD can be attached and detached by mutually rotating them at a predetermined angle.
Since rotation of the CRD is prohibited by a rotation stopper provided at approximately the mid-height position of the CR guide tube, attachment and detachment of both is performed exclusively by rotating the CRD. For this reason, even if only the CR was to be removed, the CRD had to be removed from the CRD housing each time. For this reason, it took a long time to remove the CRD, and the amount of time workers spent working inside the pedestal increased, resulting in an increased radiation dose for workers. It is also conceivable to rotate the CR and remove it without removing the CRD. However, in order to rotate the CR, the piston of the CRD must be raised above the detent, and since the detent is located at a fairly high position, the CRD piston is tilted. In reality, it would have been extremely difficult for the two parties to separate in such a situation.

[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 the CR and CRD by mutually rotating them by a predetermined angle.
In BWR, attaching and detaching CR and CRD is done by CR or
Can be done from either side of the CRD,
In particular, the aim is to significantly reduce the radiation exposure of workers by making it possible to remove the CR in a short time without removing the CRD from the CR housing.

[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 having a guiding function for the operating CR is connected to the lower end of the CR, and during reactor operation, the CR is raised and lowered inside the CR guide tube, and the attachment and detachment from the CR is performed by rotating with a predetermined sensitivity to the CR. This is achieved by comprising a CRD that is performed by the CRD, and a rotation stopper that is provided at the lower end of the CRD guide tube and engages the lower end from above to prevent rotation of the CR.

[Embodiment of the Invention] FIGS. 1 to 3 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 each cylindrical channel box, and is arranged in a matrix in the reactor core shroud 102 in a plan view. container 1
The coolant flowing upward from the bottom of 01 is heated by nuclear reaction heat. In addition, CR1 is installed in the core 105.
06 is installed. This CR106 combines four blades 106a containing a neutron absorbing material so that the cross section is cross-shaped, and has a socket 106b (see Figure 2) at the lower end.
The four fuel assemblies 1 are interposed between the adjacent fuel assemblies 104 with the blades 106 a
They are placed at a ratio of 1 to 04. By inserting each CR 106 from below between the fuel assemblies 104, the core output is suppressed according to the insertion amount, and by withdrawing each CR 106 from below between the fuel assemblies 104, the core output is increased. The configuration 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 evaporated coolant 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 and has its upper end outer periphery suspended by the core support plate 103, and its upper end is 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. Furthermore, 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. Also, CR guide tube 1
A locking portion 113 is provided at the lower end portion of 07.

In addition, as shown in FIGS. 1 and 2,
The CRD 108 is housed and supported in a cylindrical CRD housing 114 that passes through the bottom end plate 101a of the reactor pressure vessel 101 and is welded to the bottom end plate 101a. And this CRD housing 1
14 includes a locking portion 113 of the CR guide tube 107.
is being introduced 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. Furthermore, the CRD 108 includes a piston 117 that moves the outer tube 115 up and down, and a motor section 118 (first
), and with the motor section 118 located below the CRD housing 114, the CRD
It is attached to the lower end flange portion of the housing 114 with bolts or the like.

At the upper end of the piston 117 of the CRD 108,
Four vertically long engagement pieces 1 arranged at intervals in the circumferential direction
A bayonet type connecting portion 119 consisting of 19a is provided, and a bulging portion 119b is formed at the tip of the outer surface of each engaging piece 119a. Further, a support rod 119c is provided at the center of the four engagement pieces 119a to project upward, and this support rod 119c limits the amount of inward deflection of the four engagement pieces 119a. I have to. On the other hand, the socket 106b at the lower end of the CR 106 is provided with a recess 120a for accommodating the connecting portion 119, and the opening end of the inner peripheral surface of the recess 120a has four engaging pieces corresponding to the respective engaging pieces 119a. The bayonet type connected portion 120 is constructed by projecting mating projections 120b at equal intervals in the circumferential direction. The connecting portion 119 and the connected portion 12
0 is 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.

At the lower end of the CR guide tube 107, a CR10
A rotation preventing portion 122 is provided into which the lower end portion of each blade 106a of No. 6 is fitted from above. This rotation prevention part 122 has a structure in which four fitting grooves 123 are formed at equal intervals in the upper part of a cylindrical body. An inclined surface 123a is formed in the upper half of both inner surfaces of the fitting groove 123 to serve as a guide when fitting the blade 106a from above. As shown in FIG.
12, they are in a relationship in which they fit into each other in a concave and convex manner from above and below.

Therefore, the CR 106 and CRD 108 can be attached and detached using the following two methods.

The first method is to rotate the CRD 108. This lowers the CR106 further below the operating range during reactor operation, and lowers the lower end of the CR106 (socket 106b) to the CRD guide pipe 10.
This is done with the person seated on the seat surface 112 of No. 7. 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 then the piston 11 of the CRD 108 is connected.
7 will rise. At this time, the engagement piece 119a on the CRD 108 side is made to pass between the engagement protrusions 120b, and when the support rod 119c comes into contact with the bottom surface of the recess 120a, the entire CRD 108 is rotated about 45 degrees, and each engagement piece 119a engaging the protrusion 119b and the engagement protrusion 120b in the recess 120a;
Attach CRD 108 to CRD housing 114 with bolts. Also, CR106 and CRD108
To remove the CR106, first seat the CR106 on the seat surface 112 of the CR guide tube 107, and then
Remove the mounting bolts for the housing 114,
Rotate the entire CRD 108 by approximately 45 degrees and attach each engaging piece 11.
9a is removed from the engagement protrusion 120b in the recess 120a, and the engagement piston 1 is moved so that the engagement piece 119a passes between the engagement protrusions 120b.
17 will be lowered.

And in this way CR106 and CRD108
When attaching and detaching the CR106 to the blade 10
Fitting groove 123 between the lower end of 6a and the rotation stopper 122
Rotation is prohibited due to engagement with
CRD 108 can be easily rotated relative to CR 106.

The second method is to rotate the CR 106, which is particularly effective when only the CR 106 needs to be removed while leaving the CRD 108 behind. This is CRD
The CR 106 is slightly raised from the lowest position by the piston 117 of 108, and the lower end of the blade 106b of the CR 106 is inserted into the fitting groove 1 of the rotation stopper 122.
It is carried out in a state where it is separated from 23. That is,
First, the CR 106 is slightly raised by the piston 117 of the CRD 108, and the lower end of the blade 106b of the CR 106 is inserted into the fitting groove 12 of the rotation stopper 122.
3, rotate the CR 106 by about 45 degrees to disengage the engagement protrusion 120b in the recess 120a from the bulge 119b of each engagement piece 119a, and then lift the CR 106 upward. be. In this case, the piston 117 of CRD108
Since rotation is prohibited within the CRD housing 114, rotation of the CR 106 can be easily performed.

Therefore, in the above configuration, CR106 and
Attaching and detaching from CRD108 to CR106 or CRD10
It can be done from either side of the 8, especially
Since the removal work of the CR 106 can be carried out in a short time without removing the CRD 108 from the CR housing 114, it is possible to significantly reduce the radiation dose to the workers.

[Effect of the invention] As detailed above, according to the present invention, CR and
In BWRs, which can be attached and detached from the CRD by rotating them by a predetermined angle, the CR and CRD can be attached and detached from either the CR or the CRD.
This can be done in a short time without removing it from the CR housing, significantly reducing the radiation dose to workers.

[Brief explanation of the drawing]

Figures 1 to 3 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 view taken in the direction of - arrow in Fig. 2, Figs. 4 to 9 show conventional examples, and Fig. 4 shows a conventional example.
5 is a cross-sectional view showing the schematic configuration of BWR, FIG. 5 is a cross-sectional view of FIG. 7, FIG. 6 is a cross-sectional view of FIG. 7, and FIG. , Figure b is a cross-sectional view of Figure a, No. 9
Figure a is a sectional view showing the connection state of CR and CRD, and figure b is a cross-sectional view taken from figure a. 105...Reactor core, 106...CR (control rod), 1
06a...Blade, 106b...Socket, 1
07...CR guide tube (control rod guide tube), 108...
CRD (control rod drive mechanism), 122... rotation stopper,
123... Fitting groove.

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. A control guide tube having a control rod is connected to the lower end of the control rod, and during reactor operation, the control rod is raised and lowered inside the control rod guide tube, and the control rod is attached to and detached from the control rod by rotating at a predetermined angle with respect to the control rod. and a rotation stopper provided at the lower end of the control rod guide tube to fit the lower end of the control rod from above to prevent rotation of the control rod. Characteristic boiling water reactor. 2. The boiling water nuclear reactor according to claim 1, wherein the rotation stopper has four fitting grooves into which the lower ends of the four blades of the control rod are respectively fitted.