JPH03243896A - Transporting method for atomic fuel pellet - Google Patents

Abstract

PURPOSE:To facilitate repacking operation by inserting a pellet into a tube which has an inside diameter a little larger than the outside diameter of the pellet and has an outside diameter nearly equal to that of a fuel rod, fitting end plugs to both ends, and inserting a pressure spring between the end plugs and pellet. CONSTITUTION:The tube 1 where the pellet is inserted consists of stainless steel and B-containing stainless steel which absorbs ore neutrons than Zircaloy and the end plugs 3 and 4 are fitted to both ends. The inside diameter of the tube 1 is a little larger than the outside diameter of the pellet, the outside diameter is nearly equal to the diameter of the fuel rod, and the pellet is inserted into the tube 1. Further, the spring 2 is interposed between the end plugs 3 and 4 and pellet to form the tube 1 in a shape similar to the fuel rod. This tube 1 is constituted by as an assembly of many tube bundles by plural support members 5 having elastic support parts and upper and lower end plates 6 and 7 holding both ends.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for efficiently transporting nuclear fuel pellets.

(Prior art) As shown in Fig. 5, a nuclear fuel rod (A) is made by loading pellets (P) into a cladding tube 01), inserting two plenum springs, and attaching end plugs (+3) 04) at the top and bottom, respectively. This fuel rod (A) is hermetically welded as shown in Figure 6.
~300 rods are arranged in a square grid through the support grid 06), and are connected to the upper and lower nozzles 07) Qfl along with the control rod guide tube 051.
) is fixed between them to form a fuel assembly.

Nuclear fuel assemblies like the one described above are normally manufactured at a fuel manufacturing factory and then transported to a nuclear power plant, but due to the nature of the fuel, strict management is required to prevent accidents such as falls and collisions. For safety reasons, a cylindrical transport container is used in which a lid body I2I, which also has a double shell, is attached to the container body 09), which also has a double shell, so that it can be opened and closed using a bolt structure (B), as shown in Figure 7. .

However, on the other hand, nuclear fuel is not only transported in the form of fuel assemblies, but also fuel pellets are transported in the form of pellets in order to manufacture fuel rods.

The transportation of such fuel pellets is completely different from the transportation of the fuel assemblies, and conventionally, as shown in FIG.
(P) is placed on top, a similarly corrugated tray (22) is placed on top, the whole is secured, and several of these are placed in a can and transported.

(Problem to be Solved by the Invention) However, in the pellet transport method as described above, (a) a special container just for transporting the pellets is required in addition to the aggregate transport container, and this is separately designed and manufactured. There is a need.

(b) Since there is nothing to absorb the shock, the shock is applied directly to the pellet, causing chipping of the pellet, which is not necessarily desirable in terms of the health of the pellet.

(c) When loading fuel rods on the receiving side, since the type of pellets to be loaded into each fuel rod is determined, extra work such as sorting the pellets is required.

There are problems such as. It is technically difficult to manufacture a particularly special container for transporting pellets, and it is also economically disadvantageous.

The present invention deals with the above-mentioned situation, and by discovering that the pellets are formed as a simulated fuel rod when transporting the pellets, it is possible to share the conventional transport container for fuel assemblies, and to transfer the pellets to the fuel rods. The purpose is to make refilling easier and eliminate the need for extra work on the sending and receiving sides.

(Means for Solving the Problems) That is, the features of the transportation method of the present invention that meet the above objectives are as follows: (1) The pellets have an inner diameter slightly larger than the outer diameter of the pellets, and the outer diameter is approximately the same as that of an actual fuel rod. (2) Next, at least one end plug is removably attached to both ends of the tube into which the pellet has been inserted, and a pressing spring is attached to at least one of the spaces between the end plug and the inserted pellet. (3) Thereafter, the tube into which the pellets and springs have been inserted is assembled into a bundle using a plurality of support members having elastic support portions and upper and lower end plates, and transported using a fuel assembly transport container.

Here, the support member that supports the tube is a simplified one that has only the elastic support part of the support grid in the fuel assembly, and the support grid can be used for other purposes, and the plate thickness can be increased It is formed by making improvements and making it more durable.

Further, the upper and lower end plates correspond to the upper and lower nozzles in the fuel assembly, and the upper and lower nozzles can be used for other purposes, and are configured by omitting things unnecessary for transportation such as water flow holes in the actual upper and lower nozzles.

Note that the support member and the upper and lower end plates may each be formed independently, but it is also possible to attach them to the structure of the transport container itself in advance.

(Function) According to the pellet transportation method as described above, the assembled pellets and the tube into which the pressure spring is inserted become fuel rods, and therefore, in the bundle, the support member corresponds to the support grid of the fuel assembly, and the upper and lower end plates are the upper and lower end plates. There is no need to manufacture a special container for transporting pellets as in the past as a simulated fuel assembly corresponding to a nozzle, and the cylindrical transport container conventionally used as a fuel assembly transport container can be used as is Can fulfill pellet transport.

Furthermore, the tube into which the pellets and presser springs are inserted and accommodated is similar to the cladding tube of a fuel rod, and by removing the end plug, it is easy to transfer to a true cladding tube.

(Examples) Hereinafter, specific examples of the present invention will be described with further reference to the accompanying drawings.

Figures 1 and 2 show examples of pellet transport modes in the transport method of the present invention. In the figures, (1) indicates pellets (P).
(2) is a pressure spring, (3) and (4) are end plugs that seal both ends of the tube (1). Pellets (P) are made of stainless steel and B-containing stainless steel that absorb a lot.
), the pellet (P) is inserted into the pipe (1) with an inner diameter slightly larger than the outer diameter of the pipe (P), and the outer diameter also has the same diameter as the actual fuel rod, and the end plug (3) or (4) is inserted into the pipe (1). ), in the figure, the pressure spring (2) is inserted into the space between the end plug (4) and the pellet (P), and the tube ends are sealed with the end plugs (3) and (4). The fuel rod is formed in a form similar to a fuel rod.

In addition, in forming a form similar to the above fuel rod, at least one end plug (3) or (4) must be removable in order to insert and remove the pellet (P), and in the illustrated example, A screw structure is applied. However, it is also possible to use a projection 00) and a groove 00)' as shown in FIG. 4(a) (+7) instead of the threaded structure.

In addition, as shown in the illustrated example, the structure for removing the end plug may be applied to both ends, and in this case, the inner pellet tube (1
), it becomes easier to insert and take out the pellets, and it also becomes possible to transfer the pellets to the cladding tube.

Moreover, in any of the above cases, if the outer diameters (D) of the end plugs are fixed so that they are in contact with each other, vibration can be further prevented.

In this way, the tube (1) into which the pellets and presser springs are inserted, which is formed to resemble a fuel rod as described above, is then fitted with a plurality of support members (5) having elastic support portions as shown in FIG. It is assembled into a large number of assembled tube bundles using upper and lower end plates (6, 7) (located on the left and right in the figure) that hold both ends.

At this time, the supporting member (5) is used as the framework structure during the assembly.
The support grid and upper and lower nozzles of the fuel assembly are normally used for the upper and lower end plates (6) and (7).These support grids and upper and lower nozzles may be used as they are, but with some modification. Sometimes.

For example, for the upper and lower nozzles, unrelated items such as the water flow holes in the actual upper and lower nozzles may be removed, and the support grid may only require an elastic support part. etc.

In addition, in the above assembly, a spring (9) is inserted between at least one side between the end plate and the end plug of the simulated fuel rod, as shown in Figure 3, and between the end plate (6) and the end plug (3) in the figure. This can prevent vibration in the axial direction.

The method described above is to insert Pellet (P) into a pipe (]) and create it as a simulated fuel rod. Therefore, by regarding it as a fuel rod during transportation, a dummy assembly is created. It is then handled in the same way as a fuel assembly, loaded and housed inside a conventional fuel assembly transport container, and transported in the same manner as the same fuel assembly.

On the other hand, as a modification of the above transportation method, instead of loading the assembled dummy assembly into the transportation container during the transportation described above, the support member (5) and the upper and lower end plates (6) and (7) are attached to the structure (8) of the transportation container itself. ) can also be installed in advance.

In this case, if only one of the upper and lower end plates is made removable, the tube into which the pellets have been inserted can be directly stored in the container as shown in FIG.

Note that fuel assemblies for pressurized water reactors have a control rod guide tube as shown in Figure 6, but it is possible to omit a part of this and insert a tube with pellets inserted here as well to increase efficiency. can.

However, it goes without saying that recalculation is required to ensure criticality safety.

Thus, when nuclear fuel is transported in the form of pellets as described above, the pellets are basically formed into a form similar to actual fuel rods, and the same containers used for conventional transport of fuel rod assemblies can be used as is. Transport can be carried out using pellets.

(Effects of the Invention) As described above, in transporting nuclear fuel pellets, the present invention forms the pellets into a form similar to fuel rods, bundles them in the same way as fuel assemblies, and transports them using a fuel assembly transport container. This method is extremely economically advantageous, as the conventional transport container for fuel assemblies can be used as is, and there is no need to manufacture a special pellet transport container as in conventional pellet transport. There is almost no need to re-evaluate the above, and there are no problems with licensing, making it possible to transport pellets very smoothly.

Furthermore, since the transportation method of the present invention makes the pellets similar to fuel rods, chipping and cracking of the pellets can be prevented, and the pellets can be transported in a sound manner during transportation.

Furthermore, the present invention uses a tube into which pellets can be inserted and at least one of the end plugs can be removed, making it possible not only to insert and remove pellets, but also to directly transfer them to a true fuel rod cladding tube. This makes it easier to refill fuel rods, and there is no need for extra work such as rearranging the receiver at the receiving end, which is expected to have a significant effect in terms of manufacturing.

[Brief explanation of drawings]

Figure 1 shows one of the pellet transportation modes in the transportation method of the present invention.
As an example, a partially omitted sectional view showing a configuration similar to the fuel rod, FIG. Vibration prevention structure schematic diagram, Figure 4 (a) (0) is a diagram showing a modified example of the connecting part between the end plug and the pipe in the end plug removal structure, and Figure 5 shows the general configuration of the fuel rod. 6 is a schematic front view of the fuel assembly, FIG. 7 is a partially cutaway perspective schematic diagram showing an example of a conventional fuel assembly transport container, and FIG. 8 is an internal structure diagram.
The figure is a schematic diagram showing an example of a conventional pellet transport means. (A) ...Fuel rod (P) ...Pellet. (1)...Pipe. (2)...Press spring. (3) (4)...End plug. (5) Support member. (6) (7)...End plate. Figure 1 Figure 6 Figure 2 Figure 4

Claims (1)

[Claims] 1. When transporting nuclear fuel pellets, the pellets are inserted into a tube that has an inner diameter slightly larger than the outer diameter of the pellets and whose outer diameter is approximately the same as the actual fuel rod, and then the tube into which the pellets are inserted. At least one end plug is removably attached to both ends of the tube, and a presser spring is inserted into at least one of the spaces between the end plug and the inserted pellet, and then the tube into which the pellet and presser spring are inserted is elastically attached. A method for transporting nuclear fuel pellets, which comprises assembling a bundle using a plurality of support members each having a support portion and upper and lower end plates, and transporting the pellets using a fuel assembly transport container.