JPH0358076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an apparatus for supporting a control rod drive mechanism housing in a reactor pressure vessel in a boiling water nuclear reactor.

[Technical background of the invention]

A conventional control rod drive mechanism (hereinafter referred to as CRD) housing support device will be described with reference to FIGS. 1 to 6.

2 in FIG. 1 is a reactor pressure vessel, and this reactor pressure vessel 2 houses a reactor core 4 therein.
Further, the reactor pressure vessel 2 is filled with reactor water 6 as a coolant, and is configured to cool the reactor core 4.

A plurality of CRDs (not shown) are provided penetrating the lower mirror portion of the reactor pressure vessel 2. This CRD
is housed in a cylindrical CRD housing 8 that penetrates the lower mirror portion of the reactor pressure vessel 2, and is driven by water pressure so that the control rods 10 located above can be inserted into and removed from the reactor core 2. It is composed of

A control rod guide tube 12 (hereinafter referred to as CRGT) is connected to the upper end of the CRD housing 8, and this CRGT 12 passes through a core support plate 14 and is connected to the lower part of the reactor core 4. In the figure, reference numeral 16 denotes an upper lattice plate, and this upper lattice plate 16 supports the fully inserted control rod 10 in the horizontal direction.

The reactor pressure vessel 2 is placed on a cylindrical foundation 18 called a pedestal, and this foundation 18 surrounds the CRD housing 8.

Additionally, a conventional CRD housing support device 20 is provided inside the foundation 18. This support device 20 includes a beam 22, a rod 24, a support block 26, a support bar 28, and a disc spring 30, and is configured to support the CRD housing 8 from below.

As shown in FIGS. 2 and 3, the CRD housing 8 is connected to the reactor pressure vessel 2 through a stub tube 32 protruding from the inner surface of the lower mirror portion of the reactor pressure vessel 2 to maintain watertightness. ing. The lower end opening of the CRD housing 8 is sealed with a flange 33. Further, a thermal sleeve 34 is housed within the CRD housing 8, and the CRD 36 is housed inside the thermal sleeve 34. The upper end of CRD housing 8 is
Connected to CRGT12.

A control rod 10 is housed in the CRGT 12 as shown in FIG.
Connected to CRD36. The CRGT 12 passes through the core support plate 14 and is connected to the core 4.

The control rod 10 has a cruciform cross-sectional shape and is configured to absorb thermal neutrons and control the reactivity of the reactor core 4. Four fuel assemblies 42 are connected around the control rod 10 via fuel support fittings 40.
is located. This fuel assembly 42 and control rod 10 constitute a unit cell. This unit grid is supported by the upper grid plate 16. Note that the core support plate 14 and the upper grid plate 16 are supported by a core shroud 44 that surrounds the core 4 .

With reference to FIG. 4, the CRD housing 8 and
The connection mechanism with CRGT12 will be explained. Reference numeral 46 in FIG. 4 denotes engagement protrusions projecting inward from the upper end of the thermal sleeve 34, and a plurality of these protrusions 46 are provided at equal intervals on the inner peripheral surface of the thermal sleeve 34. . On the other hand, the lower end of the CRGT 12 is shaped to be inserted into the inner surface of the thermal sleeve 34, and an L-shaped engagement groove into which the engagement protrusion 46 engages is formed in this lower end. The engagement groove and the engagement protrusion 46 constitute a so-called bayonet mechanism that is engaged in the vertical direction and then rotated and fixed in the circumferential direction.

Further, a key 48 is fitted into the outer periphery of the lower end of the thermal sleeve 34.
and CRD housing 8 are fixed.

Therefore, the CRGT 12 cannot be removed unless the thermal sleeve 34 is rotated to disengage the bayonet mechanism, and the thermal sleeve 34 cannot be rotated unless the key 48 is removed. It is becoming.

By the way, if the welded portion of the stub tube 32 were to break, there is a risk that the CRD housing 8 would drop downward and the reactor water 6 would flow out. For this reason, CRD
The housing 8 is attached to the CRD housing support device 2.
0 and is configured to be supported from below.

Below, with reference to Figures 5 and 6, the conventional
The CRD housing support device 20 will be explained. Fifth
In the figure, reference numeral 22 denotes a beam, and this beam 22 is installed within the foundation 18 through a gap in the CRD housing 8, in which a plurality of beams are provided.
A plurality of rods 24 are hung vertically through the beam 22, and a disc spring 30 is attached to the upper end of the rod 24 so as to bias the rod 24 upward. Further, the rod 24 extends below the CRD housing 8, and a support block 26 is attached to the lower end of the rod 24. A plurality of support blocks 26 support the beam 2.
It is placed parallel to 2. Furthermore, a support bar 28 is installed on the upper surface of the support block 26. As shown in FIG. 6, the support bar 28 is configured to sandwich the flange 33 and support the CRD housing 8 from below.

[Problems with background technology]

The conventional CRD housing support device 20 had the following problems.

First, when inspecting and repairing the CRD, it was necessary to remove the support device 20. However, there was a problem in that the radiation level was high inside the foundation 18 where the support device 20 was installed, and when a worker entered the foundation 18 and performed the above-mentioned removal work, the amount of radiation exposure to the worker increased.

Also, if the CRD mechanism is changed to an electric type, etc.
There was also a risk that the shapes of the CRD housing 8 and the flange 33 would change, making it impossible to install the support device 20 as described above.

[Object of the Invention] The object of the present invention is to reduce the radiation exposure of workers by eliminating the need for workers to enter the foundation for removal work, and to allow installation even if the shape of the CRD housing is changed. CRD that can
An object of the present invention is to provide a housing support device.

[Summary of the invention]

The CRD housing support device according to the present invention includes engaging bodies protruding from the entire circumference of the upper outer circumferential surface of the CRGT that penetrates the core support plate or at a plurality of opposing positions, and the engaging bodies are engaged with the core support plate. Even if the weld between the lower head of the reactor pressure vessel and the CRD housing is damaged, the load transmitted from the engaging body to the core support plate is equally distributed around the circumference, and the engaging body is firmly supported by the core support plate. This prevents the CRGT from falling.

[Embodiments of the invention]

A first embodiment of the present invention will be described with reference to FIGS. 7 and 8. In addition, the same reference numerals are given to the same parts in the figures as in the prior art to avoid duplication of explanatory text.

12 in Figure 7 is CRGT, and this CRGT
12 penetrates through the core support plate 14 and has an upper portion projected above the core support plate 14 . An engaging body 102 is provided protruding from the upper outer peripheral surface of the CRGT 12 . This engaging body 102 is connected to the CRGT1 as shown in FIG.
They are formed at four equal intervals on the outer periphery of the core support plate 14, and are configured to engage with the upper surface of the core support plate 14.

The operation of the apparatus configured as above will be explained.
In the event that the welded portion of the stub tube 32 is damaged, the CRD housing 8 tends to fall off downward. However, CRD housing 8 is CRGT
Since the engaging body 102 of the CRGT 12 engages with the core support plate 14,
The CRD housing 8 is supported and prevented from falling downward.

The advantages of the apparatus according to the first embodiment of the present invention will be explained.

First, it is not necessary for a worker to enter the foundation 18 and remove the support device 20 as in the past, and the amount of radiation exposure of the worker can be reduced. Also,
To remove CRGT12, disconnect the CRD housing 8 and CRGT12 as described above.
CRGT12 can be removed by lifting it from above the core.

Next, since it is not affected by the shape of the CRD housing 8, it can be easily installed in other types of CRDs such as electric type.

A second embodiment of the present invention will be described with reference to FIG. In this second embodiment, an engaging body 108 is formed by a protruding body 104 protruding from the outer periphery of the CRGT 12 and a buffer body 106 fixed to the lower surface of the protruding body 104.

In addition to the advantages obtained in the first embodiment, the second embodiment can buffer the impact force generated between the protrusion 104 and the core support plate 14.

Note that the present invention is not limited to the above two embodiments. Other embodiments will be described below with reference to FIGS. 10 to 14.

A third embodiment of the present invention will be described with reference to FIG. In this third embodiment, an engaging body 110 in the form of a protruding peripheral wall is formed on the outer periphery of the CRGT 12, and the core support plate 14 is
The engaging body 110 is made to engage with the engaging body 110.

In the third embodiment described above, the strength of the engaging body 110 can be improved and reliability can be further improved.

A fourth embodiment of the present invention will be described with reference to FIG. In this fourth embodiment, an engaging body 114 is formed by a protrusion 104 protruding from the outer periphery of the CRGT 12 and a spacer 112 welded to the protrusion.

In this fourth embodiment, the spacer 112 can adjust the vertical dimensional error that occurs between the protrusion 104 and the core support plate 14.

A fifth embodiment of the present invention will be described with reference to FIG. In this fifth embodiment, a spacer 116 is passed through the projecting body 104.

A sixth embodiment of the present invention will be described with reference to FIG. In this sixth embodiment, an engaging body 122 is formed by a protruding body 104, a spacer 118 loosely inserted into the protruding body 104, and a buffer body 120 interposed between the spacer 118 and the protruding body 104. It is designed to form a .

Furthermore, the present invention is not limited to the connection mechanism as shown in FIG. It can also be applied to In this case, the aforementioned bayonet mechanism may be released by rotating the CRGT 12.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to provide a CRD housing support device that can reduce radiation exposure of workers and can be easily installed even if the shape of the CRD housing is changed. It is possible and the effect is great.

[Brief explanation of drawings]

Figures 1 to 6 are diagrams showing conventional examples.
The figure is a vertical cross-sectional view of the reactor pressure vessel, and the second figure is the CRD.
A vertical cross-sectional view of the housing 8, Figure 3 is CRGT12
Figure 4 is a vertical cross-sectional view of the CRD housing 8 and
Vertical sectional view showing the connection mechanism with CRGT12, No. 5
The figure is a perspective view of the CRD housing support device 20, FIG. 6 is a side view of the lower end of the CRD housing support device 20, and FIGS. 7 and 8 are views showing a first embodiment of the present invention. Longitudinal cross-sectional view of CRGT12,
FIG. 8 is a plan view of the CRGT 12, FIG. 9 is a vertical sectional view of the CRGT 12 showing a second embodiment of the invention, and FIG. 10 is a CRGT 12 showing a third embodiment of the invention.
FIG. 11 shows a fourth embodiment of the present invention.
12 is a longitudinal sectional view of the CRGT 12 showing the fifth embodiment of the present invention; FIG.
The figure is a vertical cross-sectional view of a CRGT 12 showing a sixth embodiment of the present invention, and FIG. 14 is a vertical cross-sectional view of a connecting mechanism showing a modification of the connecting mechanism shown in FIG. 4. 8... Control rod drive mechanism housing (CRD housing), 12... Control rod guide tube (CRGT), 102,
108, 110, 114, 122, ... engaging body, 1
04... Projection body, 106, 120... Buffer body, 11
2,116,118...Spacer.

Claims (1)

[Scope of Claims] 1. A control rod drive mechanism housing provided through a lower mirror of a reactor pressure vessel of a boiling water reactor;
A control rod guide tube provided through a core support plate connected to the upper end of the housing, and a control rod guide tube protruding from the entire circumference of the upper outer peripheral surface of the control rod guide tube or at a plurality of opposing positions to support the core. The method further includes an engaging body that engages with the plate to prevent the control rod guide tube from falling due to damage to the welded portion between the reactor pressure vessel lower mirror portion and the control rod drive mechanism housing. Control rod drive mechanism housing support device. 2. The engaging body is characterized by comprising a protruding body protruding from the entire circumference of the upper outer peripheral surface of the control rod guide tube or at a plurality of opposing positions, and a buffer body attached to the protruding body. Claim 1
Control rod drive mechanism housing support device as described in .