JP3265116B2 - Control rod shielding device in reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shielding device for a control rod in a nuclear reactor, which is used to shield radiation from the control rod during inspection of a boiling water reactor.

[0002]

2. Description of the Related Art An improved boiling water reactor has a structure as shown in FIGS. 5 and 6, for example. That is, in the reactor pressure vessel 1, a large number of fuel assemblies 2 and a set of four such fuel assemblies 2 are inserted into the cruciform gap, and control rods 3 of cruciform cross blades are inserted into the cruciform gap. Core 4 consisting of
Is configured.

[0003] A shroud 5 is provided outside the core 4, a shroud cover 6 is attached to an upper end of the shroud 5, and a steam separator 7 and a steam dryer 8 are sequentially provided on the shroud cover 6. . The fuel assembly 2 is shown in FIG.
As shown in (a) and (b), the upper part is the upper lattice plate 9,
The lower end is supported by a fuel support on the core support plate 10.

The control rod 3 is inserted through the control rod guide tube 11 and penetrates the lower surface of the reactor pressure vessel 1 to be installed therein.
It is driven up and down by 12. An internal pump 13 is attached to the lower surface of the reactor pressure vessel 1, and a cooler 14 is connected to the internal pump 13. Reactor pressure vessel 1
The upper end opening is closed by a pressure vessel cover 15.

In the core 4, measuring tubes 16 such as a neutron source region monitor (SRM), an intermediate region monitor (IRM), and a local region output monitor (LPRM) are dispersedly arranged to monitor the power distribution of each part of the core. are doing.

In a boiling water reactor, a cover (not shown) of the containment vessel and a pressure vessel cover 15 during periodic inspection are provided.
Are removed and the fuel assembly 2 is moved. For example, when the construction such as replacement of the measuring pipe 16 and maintenance and inspection of the internal pump 13 is performed thereafter, the worker is usually protected from radiation exposure by water shielding with reactor water. Conventionally, the control rod is not particularly shielded from radiation.

[0007]

In the case of a boiling water reactor, if it becomes necessary to lower the reactor water during periodic inspection, the fuel assembly 2 is moved to a fuel storage pool.
The control rod 3 is retracted and the control rod 3 is stored in the control rod guide tube 11.

However, there are cases where the work is performed while lowering the reactor water level to the vicinity of the core support plate 10 for the sake of construction. In this case, even if the control rods 3 are stored in the control rod guide pipes 11, there is a problem in terms of the structure. The upper part of the control rod 3 protrudes, and in particular, the lifting handle part of the control rod 3 remains on the fuel support fitting to generate high radiation. For this reason, the amount of radiation generated from the control rod 3 increases, and the radiation exposure of the worker increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and the radiation generated from the control rods is shielded even when the reactor water drops during the inspection of the reactor and the upper part of the control rods protrudes. An object of the present invention is to provide a shielding device for a control rod in a nuclear reactor, which can significantly reduce a radiation exposure dose.

[0010]

The invention according to claim 1 has a cross-shaped gap inserted between the upper lattice plate in the reactor pressure vessel and the core support plate and inserted into the control rod guide tube. A shield assembly to which a set of four columnar shields arranged in two rows and two columns is attached, a handling tool detachably connected to an upper end of the shielding assembly, and a fastening bolt is provided at an upper end of the handling tool. a grid guide connected through, characterized by comprising a wire rope which connects in this grid guide hanging Ri hands on the top plate of the insertion and the handling tool. Invention according to claim 2
The shield assembly is a polygonal cylindrical top plate and the top plate
A handle having a pin lock hole provided on the surface,
A cross-shaped gap is attached to the lower surface of the tabletop along the axial direction.
And a set of four columnar shields arranged in two rows and two columns.
It is characterized by that . The invention according to claim 3 is characterized in that the handling
A pin inserted into a pin lock hole of the handle,
A cylinder that resiliently operates this pin, and this cylinder
And a top provided at the upper end of the body.
It consists of a plate and a suspender provided on this top plate.
Sign . The invention according to claim 4 is characterized in that the columnar shields are
Characterized by being made of heavy stainless steel or lead
You .

[0011]

[Function] With the control rod lowered into the control rod guide tube,
Move the refueling machine installed on the platform on the furnace,
Use the chain block attached to the overhead crane.
The handling tool is directly hung by a wire rope connected below the roller chain, and the handling tool and the columnar shield of the shield assembly pin-locked are inserted into the control rod in the control rod guide tube.

The lower surface of the top plate cylindrical portion of the shield assembly lands on the upper end surface of the control rod guide tube, and the columnar shield is inserted between the cross blades of the control rod. As a result, the upper part of the control rod protruding from the control rod guide tube is covered by the top plate cylindrical portion of the shield assembly, so that leakage radiation from the control rod is blocked. Therefore, since irradiation in the furnace due to the leaked radiation can be prevented, the radiation exposure of workers can be reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control rod shielding apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an elevational view showing the entire control rod shielding apparatus in a nuclear reactor according to the present embodiment. FIG. 2A is an elevational view of the shield assembly in FIG. 1, and FIG. ), A-A view, (c) is a BB view of (a), (d) is a CC view of ( b ), (e) is a DD of (d). It is arrow sectional drawing. 3 is a longitudinal sectional view showing the handling tool of FIG. 1, and FIG. 4 is a schematic sectional view for explaining the operation of the shielding device of FIG.

In FIG. 1, reference numeral 17 denotes a shield device for a control rod in a nuclear reactor according to the present embodiment. The shield device 17 is mainly composed of a grid guide 18, a handling tool 19 and a shield assembly having a low-and-low cylindrical shape. It has a structure in which the three-dimensional body 20 is sequentially connected up and down.

A wire rope 21 and an air hose 22 are inserted into the grid guide 18, and the upper end of the wire rope 21 is connected to the roller chain 24 of the refueling machine 23 shown in FIG. It is connected to the suspender 25 of the handling tool 19 shown.

The grid guide 18 are those of the upper grid plate 9 handling device 19 and the shielding assembly 20 serves as a guide during insertion, the lower portion of the shield assembly 20 on the control rod guide tube 11
Pillar-shaped shield 30 also serves as a guide during insertion.

The shield assembly 20 is shown in FIGS. 2A and 2B.
, A top plate 26 having an octagonal cylindrical portion 26a, a handle 28 having a pin lock hole 27 attached to an upper surface of the top plate 26, and a bolt 29 on the lower surface of the top plate 26 with a bolt 29. It consists four pillars shaped shield 30 for being.

As shown in FIG. 2 (c), the shields 30 are arranged in two rows and two columns, and have cross-shaped gaps 31 along the axial direction. Is blocked by As shown in FIGS. 2D and 2E, a small hole 33 for bleeding air is provided between the top plate 26 and the handle 28.

The shield 30 is an elongated cylindrical member made of heavy stainless steel or lead, at its distal end with a tapered inclined surface is formed, the insertion of the control rod guide tube 11 Take into account.

As shown in FIG. 3, the handling tool 19 includes a top plate 34, a cylindrical body 35 connected to the lower surface of the top plate 34, columns 36, 37 provided at the center of the body 35, and Three
A pin 38 supported by 6, 37, and a cylinder 39 which slides in the horizontal direction and is fixed by penetrating the side of the body 35.
A plug 40 for closing one end of the cylinder 39 and a coil spring 41 inserted between the plug 40 and the pin 38.

The pin 38 has a hollow portion, and the increased diameter portion serves as a piston portion and slides in the cylinder 39. A small-diameter plug 42 is connected to the cylinder 39. The small-diameter plug 42 is connected to the air hose 22 shown in FIG. 1, and pressurizes air into the cylinder 39 to slide the pin 38 as shown by a dashed line. pin
38 is inserted into the pin lock hole 27 of the handle 28 shown in FIG.

A balance cylinder 43 is connected to the left support column 37. Each of the columns 36 and 37 is attached to a flange 44, and the flange 44 is connected to the inner surface of the top plate 34 by bolts 45. The upper surface of the top plate 34 is connected to the bottom plate 46 of the grid guide 18 by a fastening bolt 47. Hanger 25 on bottom plate 46
Through hole 48 is formed.

Next, the operation of the above embodiment will be described. At the time of periodic inspection of the nuclear reactor, the fuel assembly 2 shown in FIG. At this time, the control rod 3 is pulled down into the control rod guide tube 11, and the reactor water level normally keeps a water level of about 15 m or more from the upper lattice plate 9. However, due to periodic inspection work, the furnace water level may be lowered to perform work. For example, maintenance of a nozzle or the like is one example.

When the reactor water level is lowered, the influence of radiation from the control rod 3 projecting its neck (head) above the control rod guide tube 11 becomes large. In the case of water shielding, a water depth of several meters is required. Instead of the water shielding, the shielding device 17 of this embodiment for shielding individual control rods is used as an effective and simple shield.

In this embodiment, the shield assembly 20 of the shielding device is mounted on the upper part of the control rod while the control rod is pulled down into the control rod guide tube. The grid guide 18 ties up with the upper lattice plate 9 to erect the handling tool 19. The core support plate 10 supports an upper lateral direction of the control rod guide tube 11.

That is, as shown in FIG.
And the auxiliary crane (not shown) of the overhead crane 49 is moved accordingly. A chain block 50 is suspended under the auxiliary crane, and is operated from a workbench of the refueling machine 23.

The wire rope 21 is connected to the end of the roller chain 24, and the rope 21 and the handling tool 19 are connected. Also,
The air hose 22 is connected to the cylinder 39 of the handling tool 19. Next, the grid guide 18 is fastened to the handling tool 19 with bolts 47, and the above-described wire rope 21 is passed through the center of the grid guide 18.

Air pressure is applied to the cylinder 39 of the handling tool 19 so that the pin 38 is inserted into the pin locking hole 27 of the handle 28 of the shield assembly 20.
Insert and dock to release air and lock the pin.
The shield 30 of the shield assembly 20 is suspended by the chain block 50 with the shield 30 at the top, and is lowered directly above the control rods of the core.

The shield 30 penetrates into the control rod guide tube 11 while covering the cross-shaped lifting handle of the control rod,
The lower surface of the cylindrical portion of the top plate 26 of the shield assembly 20 is the control rod guide tube 11
Stop after waiting for the landing on the top of the vehicle, release the pin lock by air turbulence, leave the shield assembly 30
And raise the grid guide 18.

Similarly, the shield assembly 20 is mounted on the other control rod 3. When the covering work of the shield assembly 20 for the control rod at the required location is completed, predetermined maintenance work is performed. After the completion of the periodic inspection work, the handling tool 19 is suspended as described above, pin-locked to the shield assembly, and sequentially removed and collected.

According to this embodiment , heavy stainless steel
Since the control rod is covered with the columnar shield , the radiation protection effect is great. This has a positive effect on the reduction of exposure during regular inspection work when the reactor water is low. In addition, the effect increases in proportion to the number of used shield assemblies, and the handling operation of the shield assemblies is easy.

In this embodiment, for example, a columnar shield made of lead material can be used instead of stainless steel to achieve the intended purpose of this embodiment, and a hand-wound winch or the like can be used without using an auxiliary hoist of an overhead crane. You may. Instead of the air lock pin, another fluid such as water pressure or hydraulic pressure may be used.

[0033]

According to the present invention, even if the reactor water drops at the time of regular inspection of the nuclear reactor and the upper part of the control rod protrudes to generate radiation from the control rod, the radiation can be shielded by the shield assembly. The radiation exposure dose to workers can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is an elevational view, partially in section, of an embodiment of a control rod shielding device in a nuclear reactor according to the present invention.

2 (a) is an elevational view showing the shield assembly in FIG. 1 in a partial cross section, FIG. 2 (b) is a top view of FIG. 1 (a) viewed from the direction of arrows AA, and FIG. (a) is a bottom view as viewed from the direction of the arrow BB, (d) is a cross-sectional view of the direction of the arrow CC in (b), and (e) is a cross-sectional view of the direction of the arrow DD in (d).

FIG. 3 is a longitudinal sectional view showing the handling tool in FIG.

FIG. 4 is a schematic diagram for explaining a use state of the control rod shielding device in FIG. 1;

FIG. 5 is a longitudinal sectional view showing a boiling water reactor.

6 (a) is an elevational view showing a part of the core in FIG. 5 in a partial cross section, and FIG. 6 (b) is a plan view showing a partial cross section in FIG. 5 (a).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Fuel assembly, 3 ... Control rod, 4
... core, 5 ... shroud, 6 ... shroud cover, 7 ...
Steam separator, 8 ... Steam dryer, 9 ... Upper lattice plate, 10 ... Core support plate, 11 ... Control rod guide tube, 12 ... Control rod drive mechanism, 13
... internal pump, 14 ... cooler, 15 ... pressure vessel cover, 16 ... measuring tube, 17 ... shielding device for control rod in reactor, 18 ...
Grid guide, 19… Handling tool, 20… Shield assembly, 21…
Wire rope, 22 ... air hose, 23 ... refueling machine, 24 ...
Roller chain, 25 ... Hanger, 26 ... Top plate, 27 ... Pin lock hole, 28 ... Handle, 29 ... Bolt, 30 ... Shield, 31 ...
Cruciform gap, 32… Connecting, 33… Small hole for air bleeding, 34… Top plate, 35… Body, 36, 37… Prop, 38… Pin, 39… Cylinder, 40… Plug, 41… Coil spring, 42… Small diameter plug , 43
… Balance cylinder, 44… Flange, 45… Bolt, 46
... bottom plate, 47 ... fastening bolt, 48 ... through hole, 49 ... overhead crane, 50 ... chain block.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21C 19/02 G21C 19/20 G21C 7/10 G21C 7/14

Claims (4)

(57) [Claims] 1. A set of four tubes arranged in two rows and two columns with a cross-shaped gap inserted between an upper lattice plate in a reactor pressure vessel and a core support plate and inserted into a control rod guide tube. A shield assembly having a columnar shield attached thereto, a handling tool detachably connected to an upper end of the shielding assembly, a grid guide connected to an upper end of the handling tool via a fastening bolt, and the grid guide inserting the inner said handling device shielding device in a nuclear reactor control rod, characterized by comprising a wire rope connected to the hanging Ri hand provided on the top plate of the. 2. The shield assembly includes a polygonal cylindrical top plate, a handle having a pin lock hole provided on an upper surface of the top plate, and an axial direction attached to a lower surface of the top plate. shielding device in the reactor control rod according to claim 1, characterized in that it consists of a four pair of columnar shield that two rows and two columns arranged with a cross-shaped gap. 3. The handle includes a pin inserted into a pin lock hole of the handle, a cylinder for resiliently operating the pin, a body for holding the cylinder, and an upper end of the body. The top plate provided and the suspension provided on this top plate
Ri shielding device in the reactor control rod according to claim 2, characterized in that it consists of a hand. 4. The columnar shield is made of stainless steel or lead.
3. The method according to claim 1 , wherein the weight comprises :
Shielding device of the mounting of the reactor control rods.