JPS5811599B2 - fuel support fitting plug - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel support plug disposed around the core of a nuclear reactor.

A nuclear reactor core can be said to be a collection of cells formed by a fuel assembly in which fuel pins containing fissile material are regularly arranged and control rods made of neutron absorbing material arranged in the gaps between the fuel assemblies. .

The cell in the center of the core consists of one control rod and four cells around it.
The main fuel assemblies (containing fissile materials such as UO2) are arranged in an array, but the cells around the core are arranged around control rods and around the control rods. A fuel support metal plug (commonly called dummy fuel) that supports and fixes the fuel assembly.

). FIG. 1 shows cells around the core that have been conventionally used.

Below is one control rod, three fuel assemblies around it, and one control rod.
Although the description will be made regarding a cell constituted by a fuel support plug, it goes without saying that the generality of the present invention will not be impaired even when the number of fuel assemblies is three or less.

Fig. 2 is a configuration diagram showing the structure of a conventional fuel support plug by cutting out a part, and Fig. 3 is a sectional view taken along the line ■-■ in Fig. 2. Explanation will be given with reference numerals.

A fuel assembly 10 in which fuel pins containing pelleted fissile material such as UO2 are regularly arranged is supported individually by fuel support fittings at its lower part, and its upper part is incorporated into an upper grid plate 12 to prevent it from falling over. is supported by

However, in the upper part, the 104 fuel assemblies are only assembled in the upper grid plate 12 in such a manner that they are pushed against each other, and are not supported individually.

Therefore, in the cells around the core, the number of fuel assemblies 10 is four or less. For example, in addition to three fuel assemblies 10, the remaining one is a fuel support plug 11 that does not contain fissile material.
is used to construct the cell so that the fuel assembly 10 does not fall over.

This fuel support fitting plug 11 includes an upper tie plate 2 which is provided with a channel 1 that serves as a guide when inserting a control rod and has bundles 2a at its upper and lower ends, and a lower tie plate 3 that is fitted into the lower support fitting. is connected.

A shaft 4 is provided in a wide space within the channel 1, and the shaft 4 is supported by the upper tie plate 2 provided above within the channel 1.

At the bottom of this shaft 4 is this fuel support fitting plug 11.
is placed in the fuel support fitting, the fuel support fitting plug 1
1 is provided with a pin 6 that is hooked onto the stop rod to prevent it from being lifted up by the force of the control rod and buoyancy when the control rod is inserted.

Further, an externally inserted sleeve 7 and a spring 8 are provided in the lower part of the pin 6 so that the pin 6 does not come off from the stopper rod.

The sleeve 7 is provided with a parallel pin 9 for fixing the shaft 4.

As mentioned above, although it is located around the core, it is simply a fuel assembly 1.
A fuel support fitting plug 11 is provided only for supporting 0,
Moreover, it is uneconomical to leave this space inside the fuel support plug 11 alone.

In consideration of the above points, the present invention provides a fuel support fitting plug that can store test pieces of these materials in order to effectively utilize the space around the reactor core and to learn the irradiation characteristics of these materials. The purpose is to

Fig. 4 is a configuration diagram showing a part of the fuel support plug according to the present invention cut away, Fig. 5 is a cross-sectional view taken along the line ■-■ in Fig. 4, and Fig. 6 is a sample box. A perspective view showing details of the
FIG. 7 is a perspective view showing details of the lid of the sample box, and the same parts as in FIGS. 1 to 3 will be described with the same reference numerals.

A channel 1 is provided as a guide when inserting the control rod,
An upper tie plate 2 having a bundle 2a and a lower tie plate 3 fitted into a lower support fitting are connected to the upper and lower ends of the channel 1, respectively.

A shaft 4 is disposed within the channel 1, and the upper portion of the shaft 4 is fixed within the channel 1 and is supported through the upper tie plate 2.

The lower part extends to the outside through the lower tie plate 3, and a stop rod (not shown) is installed near the lower end to prevent it from floating due to coolant flow or frictional force due to control rod insertion after the fuel support plug 11 is installed. ) is provided with a pin 6 to be hooked on.

In order to prevent the pin 6 from coming off the stopper rod, there is a sleeve 7 fitted over the shaft 4 in the lower part of the channel 1.
A spring 8 is provided within this sleeve 7, and the sleeve 7
The provision of parallel pins 9 for fixing the shaft 4 is the same as in the conventional case.

On the lower tie plate 3, a holding stand 21 is attached above and outside of the fixed portion of the sleeve 7 and the shaft 4 so that the sample holding device 20 is placed thereon.

The upper tie plate 2 and the lower tie plate 3 are connected outside the sample holding device 20 by a plurality of connecting rods 22 provided with a very small gap.

This connecting rod 22 not only supports the entire load during transportation, but also has a guide function so that the sample holding device 20 can be smoothly attached and detached.

As an embodiment of the main body of the sample holding device 20 is shown in FIG. A sample insertion section 25 having a shape is formed, and a sample 26 is housed therein.

Also, a plurality of cooling holes 27 are provided on the side of the box.

Further, a lid 28 having a handle 28a on the upper surface for easy handling is removably connected to the upper part by bolts or the like.

These constitute a sample holding device 20, and these sample holding devices 20 are normally stacked in several stages in the channel 1 for use.

The fuel support plug according to the present invention has the above-described configuration and is disposed around the core.

During a core reaction, the sample 26 housed in the sample holding device 20 in the channel 1 is irradiated.

When neutron irradiation exceeds a certain level, this sample holding device 20
will be taken out.

This sample 26 is cooled by a coolant flowing through a cooling hole 27 provided on the side of the box.

Furthermore, the cover 28 attached to the top of the cylinder prevents the coolant from flying out of the box due to flow of coolant.

Connecting rod 2 connecting upper and lower tie plates 2゜3
2 and the shaft 4 hold down the periphery of the sample holding device 20, so that the sample holding device 20 does not move or
The sample 26 stored inside does not vibrate.
will not cause any damage.

Furthermore, by stacking the sample holding devices 20 on a platform within the same channel 1, more effective space utilization is possible.

Furthermore, the handle 28a attached to the top of the lid 28 allows the sample holding device 20 to be easily attached to and taken out from the channel 1, and also to be easily operated during transportation.

FIG. 8 is a perspective view showing another embodiment of the sample holding device to be housed in the fuel support fitting plug according to the present invention, and FIG. 9 is a sectional view showing a sample holder inserted into this sample holding device. - The same parts as in FIG. 7 will be described with the same reference numerals.

The sample holding device 20 of this embodiment has a box-shaped box 30 that has a recess 31 on one side so as not to interfere with the shaft 4 and a plurality of cooling holes 34 on the side. .

The inside of the box 30 is partitioned into a grid pattern by a grid plate 32, and a sample holder insertion section 33 is formed, and a sample holder 35 is inserted into this sample holder insertion section 33.

This box 30 and sample holder 35 are vertically long, and the fourth
It is placed on the holding stand 21 shown in the figure, and has a length up to the top of the channel 1.

The sample holder 35 has a hollow cylindrical shape, and its shape is not particularly limited.

The sample holder 35 has a hollow portion 35a into which the sample 26 is inserted, and end plugs 35b are attached to the upper and lower ends.

At least one of the end plugs 35b is detachably attached to allow the sample 26 to enter and exit.

The fuel support plug having the above structure is installed around the core, and when the stored sample 26 is exposed to a certain neutron irradiation, it is taken out and its characteristics are inspected. This is extremely advantageous for investigating axial properties.

It goes without saying that the box 30 may also be used as the channel 1 to directly partition the lattice plate 32 into the channel 1 in a grid pattern.

FIG. 10 is a sectional view showing another embodiment of the fuel support plug according to the present invention, and the same parts as in FIGS. 1 to 9 will be described with the same reference numerals.

A channel 1 is provided as a guide when inserting the control rod,
An upper tie plate 2 having a bundle 2a and a lower tie plate 3 fitted into a lower support fitting are attached to the upper and lower ends of the channel 1, respectively.

Inside the channel 1, a guide box 36 for guiding the sample holding device 38 is attached at its upper end to the tie plate 2 and at its lower end to the lower tie plate 3.

A simulated heavy object 37 that prevents the fuel support plug from floating up and also serves as a stand for the sample holding device 38 is fixed in the lower part of the guide box 36 .

The simulated heavy object 37 may be any heavy object having corrosion resistance and heat resistance, such as stainless steel, and may be installed at the lower part of the gap between the channel 1 and the guide box 36.

A sample holding device 38 containing a sample is placed on the simulated heavy object 37 within the guide box 36 .

The shape of this sample holding device 38 is not particularly limited, and any shape can be used as long as it can be inserted into the guide box 36.The inside of the sample holding device 38 is arranged in a square pattern with a lattice plate similar to the embodiment shown in FIGS. 6 and 8. It shall be a partition.

Further, the lower tie plate 3 and the simulated heavy object 37 are provided with a plurality of coolant flow holes 3a, 37a so as to obtain uniform cooling, and the upper tie plate 2 is also provided with coolant flow holes 2b, Forms the coolant flow path for the fuel support plug.

It goes without saying that cooling holes for cooling the sample are also provided on the side surface of the sample holding device 38.

Sample holding device 3 inserted into the guide box 36
8 may be a vertically elongated device that stores the sample holder 35 inside, as in the embodiment shown in FIG. Although they may be stacked in the direction of individual shafts, since the shaft 4 shown in these embodiments is eliminated, the recess provided to avoid interference becomes unnecessary, and it goes without saying that the structure becomes simpler.

The fuel support plug in this example is also installed around the core, and the stored sample is cooled and subjected to neutron irradiation for a certain period of time, after which it is removed and its characteristics are examined. By providing a simulated heavy object at the bottom of the fuel support fitting plug, the structure and operation are simplified and work time is shortened, and the space for inserting the sample holding device 38 can be arbitrarily selected without any restrictions. Become.

As explained above, by using the space inside the fuel support plug installed around the core to store neutron irradiation samples, it is possible to obtain data on actual power reactors relatively easily. In addition, by placing these neutron irradiation samples around the reactor core, the amount of neutrons leaking from the reactor is reduced, reducing radioactive contamination outside the reactor pressure vessel, and repair and inspection of equipment, piping, etc. This can sometimes reduce secondary exposure of workers.

Although the present invention has been described above with reference to specific examples thereof, the present invention is not limited to these specific embodiments, and it goes without saying that many changes and modifications can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Figure 1 is a layout diagram showing the core arrangement of fuel support plugs;
Fig. 2 is a structural diagram showing the internal structure of a conventional fuel support plug by cutting out a part thereof, and Fig. 3 is a structural diagram showing the internal structure of Fig. 2.
FIG. 4 is a structural diagram showing an embodiment of the internal cross section of a fuel support plug according to the present invention, which is partially cut out, and FIG. 5 is a cross-sectional view taken from ■-■ in FIG. 6th cross-sectional view of
The figure is a perspective view showing one embodiment of the main body of the sample holder shown in Fig. 5, Fig. 7 is a perspective view showing one embodiment of the lid of the sample holder, and Fig. 8 is a perspective view of another embodiment of the main body of the sample holder. FIG. 9 is a sectional view showing one embodiment of the sample holder, and FIG. 10 is a sectional view showing another embodiment of the fuel support plug according to the present invention. 1... Channel, 2... Upper tie plate, 2a
...Handle, 2b...Coolant distribution hole, 3...Lower tie plate, 3ay 37a...Coolant distribution hole, 4.
・・Shaft, 6・Pin, 7・Sleeve, 8・
...Coil spring, 9...Parallel pin, 20.38...
Sample holding device, 21... Holding stand, 22... Connecting rod,
23, 31... recess, 24.32... lattice plate, 25
...Sample insertion part, 26...Sample, 27.34...
Cooling hole, 28...lid, 28a...handle, 30...
Box, 38... Sample holder entry section, 35... Sample holder, 35a... Space, 35b... End plug, 3
6... Guide box, 37... Simulated heavy object.

Claims (1)

[Claims] 1. A channel for guiding control rods, an upper tie plate and a lower tie plate provided at the upper and lower ends of this channel to support the channel, and a sample housed in the channel and containing a sample. It consists of a holding device, a guide member provided in the channel for attaching and detaching the sample holding device, and a floating prevention device provided in the channel to prevent floating. A fuel support fitting plug characterized in that it is incorporated into. 2. The sample holding device includes a main body forming an outer cylinder and having a plurality of holes for passage of coolant on the side surface, a partition plate provided to guide the insertion of the sample into the main body, and the above-mentioned 2. The fuel support plug according to claim 1, comprising a lid that is removably attached to the upper part of the main body. 3 The sample holding device consists of a main body forming an outer cylinder and having a plurality of holes on the side for passage of coolant, a partition plate provided to guide insertion of the sample into the main body, and this partition. Claim 1: The sample holder is inserted into a space partitioned by a plate, has a space for storing a sample therein, and is equipped with an end plug for closing the end. Fuel support fitting plug as described in section. 4. The fuel support plug according to claim 1, wherein the guide member is a plurality of connecting rods provided so as to be almost in contact with the side surface of the sample holding device containing the sample. 5. The fuel support plug according to claim 1, wherein the guide member is a cylinder provided at regular intervals along the side surface of the sample holding device that houses the sample. 6. The anti-lifting device is rotatably attached to pass through the upper tie plate provided at the upper part of the channel, and has a protrusion external to the lower tie plate and near the edge of the channel for engaging with another member. The fuel support fitting according to claim 1, characterized in that the shaft comprises a shaft and an engagement device for applying a force in the axial direction so that the shaft does not separate from the member with which the protrusion engages. plug. 7. The lifting prevention device is provided on the lower tie plate in the lower part of the channel, and is made of a heavy object made of a corrosion-resistant and heat-resistant material having a large number of holes for coolant circulation. Fuel support fitting plug described in scope 1.