JPH0262029B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a nuclear reactor fuel storage method, and more particularly to a nuclear reactor fuel storage method for storing irradiated fuel generated in a boiling water reactor.

[Background of the invention]

In this type of reactor fuel storage method, irradiated fuel taken out from the reactor core at a nuclear power plant is stored as reactor fuel underwater in a fuel pool installed inside the reactor building. This can be achieved by storing it in storage racks. The fuel stored by this type of storage method is
The fuel is stored in nuclear reactor fuel storage racks for about six months to a year before being transported to a fuel reprocessing plant for reprocessing.

In recent years, there has been concern about the lack of reprocessing capacity in fuel reprocessing plants, and for this reason, it is desired to store irradiated fuel for a long period of time in a fuel pool inside a nuclear reactor building. It is necessary to increase the storage capacity of irradiated fuel. The best way to increase storage capacity is to make the fuel pool larger. However, the size of the fuel pool is naturally limited due to the size of the reactor building and its internal arrangement. Therefore, efficient fuel storage methods are required.

For this reason, so-called high-density racks made of stainless steel or other neutron-absorbing materials have been used in the past to reduce the spacing between the stored fuels.

Furthermore, in addition to the fuel pool inside the reactor building, various fuel storage methods have recently been considered, such as constructing an independent storage facility for irradiated fuel outside the reactor building and storing the spent fuel in this storage facility. ing.

However, in the case of the former, a dedicated high-density rack is required, and the technology to pack the racks at high density is difficult. In addition, the latter requires the construction of a new storage facility, which requires construction costs, construction materials, and time required for construction.

[Purpose of the invention]

An object of the present invention is to provide a nuclear reactor fuel storage method that suppresses the generation of radioactive solid waste and allows existing equipment to be used.

[Summary of the invention]

To achieve the above object, the present invention provides a method for storing fuel for a nuclear reactor in which only fuel rods are taken out of a channel box and stored. This is to house the fuel rods.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings, but before that, matters on which the present invention is based will be explained.

FIG. 1 is a sectional view showing the structure of a boiling water reactor fuel.

In Figure 1, the boiling water reactor fuel is placed on the upper tie plate 1, which is used as a grip when exchanging the fuel.
and lower tie plate 2 for stable installation.
, fuel rods 3 provided between the tie plates 1 and 2, a spacer 4 for keeping the fuel rods 3 at a constant interval, and a rectangular channel box 5 for surrounding and protecting the fuel rods 3. A spring 7 is interposed in the upper sensor 6 at the upper part of the fuel rod 3 in order to absorb the expansion of the fuel rod 3 due to reaction heat during fueling. A portion of the fuel rod 3 is provided with several threaded fuel rods (hereinafter referred to as "tie rods") 8 above and below, and these tie rods 8 connect the upper tie plate 1 and the lower tie plate 2. It is joined. That is, the tie rod 8 and the upper tie plate 1 are connected by inserting the threaded portion of the tie rod 8 into the hole of the tie plate 1, and inserting the connecting nut 9 into the tie rod 8 as shown in the figure.
It is joined by tightening it into the threaded part. The tie rod 8 and the lower tie plate 2 are connected to each other by screwing the threaded portion of the tie rod 8 into a threaded tie plate mounting hole 10.

The procedure for replacing irradiated fuel in a boiling water reactor will be explained below with reference to FIGS. 2 to 4.

FIG. 2 is a cross-sectional view showing the fuel pool and reactor well.

In FIG. 2, the fuel 12 is
A fuel gripping device 15 attached to the fuel exchanger truck 14 grips the upper tie plate 1, which is a gripping portion at the top of the fuel 12, and takes it out. The fuel 12 taken out in this way passes through a passage 16 and is transferred to a fuel storage pool (hereinafter referred to as pool) 17.
will be transferred to. The fuel 12 thus transferred is stored in a fuel storage rack (hereinafter referred to as rack) 18 provided within the pool 17.

FIG. 3 is a front view showing the outer shape of the fuel storage rack, and FIG. 4 is a diagram showing the main parts of FIG. 3 in detail. As shown in FIG.
A rectangular pipe 19 for housing 2 is welded and connected to a reinforcing member 20, and the rectangular pipe 19 is further welded to a sheet plate 21.
A base 22 is attached to the lower part of the seat plate 21, as shown in FIG. Thus, the rack 18 is fixed to a mounting bolt 24 installed from the pool floor 23 by inserting a screw into the base 18 through a hole drilled in the base 18. The seat plate 21 is provided with a seating hole 25 into which the lower tie plate 2 is inserted, so that the fuel 12 can be seated stably.

The storage facility is configured as described above. Using such a facility, the fuel 12 is stored in the main rack 18, and then, with the channel box 5 removed, several fuels are put together into a lead shielding container (hereinafter referred to as a cask). It will be taken to a reprocessing plant.

The channel boxes 15 are stored as radioactive solid waste in a pool 17 inside the reactor building, or are taken out in casks to a pool in a highly radioactive solid waste storage facility and stored there. Efforts are being made to achieve high-density storage, such as storage capacity.

Thus, the storage method that forms the basis of the present invention stores the fuel 12. However, with this storage method, there is a risk that the storage amount will be insufficient in the current situation where there are concerns about insufficient processing capacity at reprocessing plants. Therefore, a high density fuel storage method is provided. FIG. 5 is an external view showing the storage method described above.

Now, fuel rod consolidation will be explained with reference to FIGS. 1 and 5.

Fuel rod consolidation refers to extracting only individual fuel rods 3 from the fuel 12 shown in FIG. 1 and using a dedicated fuel rod storage container (hereinafter referred to as a canister).
This method is currently being considered as a storage method that can store irradiated fuel at high density.

Fuel 1 for boiling water reactor as shown in Figure 1
The second channel box 5 can be removed by loosening and removing the nut 11 connecting the upper tie plate 1. Thereafter, by removing the connecting nut 9 and removing the upper tie plate 1, the individual fuel rods 3 can be easily pulled out. As a result, the fuel 12 is disassembled into the upper tie plate 1, the lower tie plate 2, the spacer 4, the channel box 5, and the fuel rods 3. Therefore, radioactive solid waste such as the channel box 5 other than the fuel rods 3 is stored in a storage facility such as the pool 17 inside the reactor building or the pool inside the highly radioactive solid waste storage facility, as described above. becomes.

On the other hand, the fuel rods 3 are stored in a fuel rod storage canister 26, as shown in FIG. However,
The fuel rod storage canister 26 is moved to a predetermined location and stored by hooking a dedicated hanging tool to a hanging fitting 27 provided thereon.

In this way, fuel rod consolidation is a storage method that takes advantage of the fact that the connected state of the fuel rods 3 is an excellent state for maintaining the subcriticality of the fuel, and it is a storage method that takes advantage of the fact that the state in which the fuel rods 3 are connected is an excellent state for maintaining the subcriticality of the fuel. It can be said that this is a method of storing high-density irradiated fuel in which the fuel rods 3 are separated and stored in a rod storage container.

Of course, if this storage method is adopted, it goes without saying that the efficiency of transporting the irradiated fuel to the reprocessing plant will also be improved.

However, when fuel rod consolidation is adopted, not only is a dedicated fuel rod storage container required, but also the storage of highly radioactive solid waste such as upper and lower tie plates, spacers, etc. produced by decomposing the fuel. Space is required.

As described above, the fuel storage method on which the present invention is based has disadvantages, and the embodiments of the present invention solve these problems.

FIG. 6 to FIG. 9 are diagrams shown for explaining an embodiment of the fuel rod storage method according to the present invention.

FIG. 6 is an explanatory view, partially in cross section, showing a connection state between a tie rod and a lower tie plate that constitute a part of a fuel rod storage canister used in an embodiment of the fuel storage method according to the present invention.

In FIG. 6, first, remove the channel box 5 of the irradiated fuel 12 by unscrewing the screw 11, then loosen and remove the connecting bolt 9 on the top of the tie rod 8, and then remove the upper tie plate 1 and remove it from all parts other than the tie rod 8. Fuel rod 3 is taken out. Therefore, this results in a state in which only the lower tie plate 2 and tie rod 6 are left.

The equipment used to achieve this condition is the channel attachment/detachment machine currently installed in the existing plant and used for periodic inspection of the fuel 12.
This can be adequately addressed by expanding its functions.

FIG. 7 is a configuration diagram showing the structure of a fuel rod extraction device constructed by expanding the function of the channel attachment/detachment device.

In FIG. 7, in the fuel rod extraction device, an elevator 28 that can load fuel 12 is connected to a fuel pool 1.
The channel box 5 and upper tie plate 1 can be moved up and down in the vertical direction along the side wall of the box 7, and the channel box 5 and the upper tie plate 1 can be removed by operation from the operating table 29. This structure is similar to channel attachment/detachment machines used in existing plants. A fuel rod extraction device is constructed by adding a fuel rod extraction mechanism 30 to such a structure. Therefore, the fuel rod extraction device described above can be used in conjunction with a channel attachment/detachment device.

When using such a fuel rod extraction device, first remove the upper tie plate, remove the channel box 5, and then use the fuel rod extraction mechanism 30 to extract the fuel rods 3 other than the tie rods 8, the members shown in FIG. It remains.

Figure 8 shows the channel box 5 in Figure 6.
FIG. 3 is a partially cutaway external view of the reattached state.

In FIG. 8, a fuel rod storage canister 31 is composed of a lower tie plate 1 generated as radioactive solid waste, a channel box 5 fitted thereto, and a tie rod 8 screwed to the lower tie plate 2. be done.

FIG. 9 is an explanatory view, partially cut away, showing a state in which the fuel rods 3 are stored in the fuel rod storage canister 31 configured as shown in FIG. 8, and the upper tie plate 1 is attached via a nut 9. .

In FIG. 8, fuel rods 3 are tightly stored in the fuel rod storage canister 31. The fuel rod storage canister 31 stored in this manner has an external shape similar to the fuel 12 shown in FIG. 1. At this stage, it is possible to transfer and store the fuel in racks 18 of the existing plant using fuel grabbers 15 mounted on conventional fuel exchanger trucks 14.

According to this embodiment, since the upper tie plate 1 and the connecting bolts 9 can be reused, the amount of radioactive solid waste generated can be reduced.

In this way, the upper tie plate 1, which constitutes the fuel 3 and has become radioactive solid waste after irradiation,
By connecting the lower tie plate 2 and the channel box 5 with the tie rod 8 to form a fuel rod storage container, the generation of radioactive solid waste can be reduced. In addition, by making it the same shape as the fuel,
The existing fuel clamping device 15 that grips and transfers the upper tie plate 1 can be used, and the rack 18 for storing the fuel 12 can also be used as a rack for fuel rod consolidation.

According to this embodiment, even if fuel rod consolidation is adopted, there is no need for a dedicated fuel storage container.On the other hand, if adopted in an existing plant, it can be easily used in combination, which is advantageous in terms of cost. Instead, the generation of radioactive solid waste can be reduced by eliminating fuel storage containers that become radioactive solid waste.

FIG. 10 is a diagram shown for explaining an application example of the embodiment of the present invention. The one shown in Figure 10 is the 8th
The difference from the diagram is the upper part 6 of tie rod 8.
A fuel rod storage spacer 32 as shown in FIG. 11 is provided through the fuel rod. As shown in FIG. 11, the fuel rod storage spacer 32 has a plate that is fixed in contact with the inner periphery of the channel box 5, and has a fuel rod insertion hole 33 into which the fuel rod 3 is inserted and an upper sensor insertion hole 34. has been configured.

By inserting the fuel rods through the fuel rod storage spacer 32, there is an effect that the accommodation capacity and packing density can be kept constant. After inserting the fuel rods, attach the upper tie plate 1 and the 9th
It is clear that the external shape is the same as the state shown in the figure.

〔Effect of the invention〕

As described above, according to the present invention, the racks and handling equipment currently used in fuel rod consolidation, which stores spent fuel in a high density, can be used, so radioactive solid waste can be Not only does this reduce the amount of fuel generated, but it is also extremely advantageous in terms of cost, and has the effect of providing an inexpensive high-density fuel storage method.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the structure of nuclear reactor fuel, Figure 2 is a sectional view showing the fuel pool and reactor well, Figure 3 is an external view showing the fuel storage rack, and Figure 4 is a sectional view showing the structure of the reactor fuel.
The figures show details of the part shown in Fig. 3. Fig. 5 is a sectional view showing the structure of the seat plate and its attachment to the fuel pool. Fig. 5 is an outline drawing showing the storage state in the fuel rod consolidation. The figure is a configuration diagram showing the connection state of the tie rod and the lower tie plate that constitute a part of the fuel rod storage canister according to the present invention, and FIG. 7 is an explanatory diagram showing the external shape of the fuel rod extraction device.
FIG. 8 is an external view showing a fuel rod storage canister used in an embodiment of the present invention, FIG. 9 is a partially cutaway sectional view showing a state in which fuel rods are stored in the fuel rod storage canister of FIG. 8, FIG. 10 is an external view showing a modification of the fuel rod storage canister used in the embodiment of the present invention, and FIG. 11 is a plan view showing the spacer used in FIG. 10. 1... Upper tie plate, 2... Lower tie plate, 3... Fuel rod, 5... Channel box, 31... Canister.

Claims (1)

[Scope of Claims] 1. In a nuclear reactor fuel storage method in which irradiated fuel taken out from the core of a nuclear reactor is decomposed and only fuel rods are taken out and stored, a lower tie plate that is produced when the irradiated fuel is decomposed. A method for storing fuel for a nuclear reactor, characterized in that a container is constructed using an upper tie plate, a channel box, and a tie rod, and the fuel is stored in the container. 2. In claim 1, a tie rod is fixed to the lower tie plate and a channel box is fitted to the lower tie rod to form a bottomed container, and after storing fuel rods in the bottomed container, the upper tie plate is attached to the tie rod. A fuel storage method for a nuclear reactor, characterized by storing fuel rods in a container by fixing them to a container.