JPH04152294A - Transport method for spent fuel rod - Google Patents

Abstract

PURPOSE:To enable a spent fuel rod to be efficiently transported without need of much cost and manpower by inserting the spent fuel rod in the guide thimble of an aggregate of other spent fuel, together with an elastic body, plugging the guide thimble and transporting the spent fuel rod, together with the fuel aggregate. CONSTITUTION:A control rod guide thimble 4 has a lower section secured to a lower nozzle with a coupling screw 7. A spent fuel rod 1 is drawn out and inspected. The rod 1 during transportation is constrained in vertical motion with a spring 9 welded to a plug 8. This plug 8 is constituted of the same material as the thimble 4, and has a vent hole 8a at the center thereof. As a fitting method for the plug 8, welding is, for example, applied. According to the aforesaid construction, spent fuel rods equivalent to the number of guide thimbles can be transported, together with a fuel aggregate.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for transporting spent fuel rods of a PWR fuel assembly, and more specifically relates to a method for transporting spent fuel rods of a PWR fuel assembly. The present invention relates to a method for transporting spent fuel rods that can efficiently transport the rods.

(Prior Art) Generally, as shown in FIG. 8, a PWR fuel assembly consists of a support grid (2) in which a large number of fuel rods (1) are vertically arranged.
) and through the support grid (2) an instrumentation tube guide simple (3) and a control rod guide simple (4).
), the fuel assembly is attached to the upper nozzle (5) and the lower nozzle (6) through a be. One of these is a non-destructive inspection of the appearance of the fuel rods, deformation, surface damage, etc. In this case, several fuel rods are selected and extracted from the fuel assembly and subjected to the above-mentioned inspection.

After inspection, when transporting the extracted fuel rods to a reprocessing plant, if the original fuel assembly is available, it can be returned to the original fuel assembly and transported, but it is better to transport the assembly more quickly. There are many cases where the fuel rods are stored away, or only the fuel rods are transferred to a hot cell (post-irradiation test facility).
In this case, the fuel rods must be cut into short lengths and transported in spent uranium containers, just like uranium residue. This is because, under current standards, reprocessing plants cannot accept single fuel rods as they are, and at present, large rods such as those mentioned above are mainly transported using these uranium containers. A beggar is being taken.

(Problem to be Solved by the Invention) However, with the above transportation method using a uranium container, only 4.5 fuel rods can be transported at a time because the container has a capacity of about 20 kg. However, as mentioned above, it is necessary to cut the fuel rods, which requires a lot of effort and cost.

The present invention deals with the actual situation such as ridges, and pays particular attention to the fact that the simple guide pipe of the fuel shed body has a diameter larger than the outer diameter of the fuel rods, and by storing the fuel rods in the simple pipe, it The purpose is to efficiently transport spent fuel rods from the reactor site or hot cell to the reprocessing plant without requiring much cost or effort.

(Means for Solving the Problems) That is, the feature of the method for transporting spent fuel rods of the present invention that meets the above object is that the fuel rods are simply inserted together with an elastic body as a guide for joining other spent fuel sources, and The guide is to simply plug it and transport it together with the fuel assembly.

(Function) A PWR fuel assembly is provided with a total of 17 to 25 simple instrumentation pipe guides and simple control rod guides, and the inner diameter of these simple pipes is larger than the outer diameter of the fuel rods, and the length is also slightly smaller. long. Spent fuel rods are inserted into these simple tubes, and elastic bodies such as springs that also have shock absorption properties are used.
The fuel assembly is transported together with the fuel assembly while its axial movement is restrained by a stopper.

Furthermore, even if a fuel rod is inserted into a simple tube, there is almost no effect on criticality (reactivity), and the transport container for spent fuel assemblies can be used as is. No rework is necessary.

(Example) The present invention will be described in detail below with further reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of a guide simple used in the fuel rod transportation method of the present invention, (1) is a fuel rod,
(4) is a simple control rod guide, (5) is an upper nozzle, (
6) respectively indicate the lower nozzles.

As shown in the figure, the guide simple (4) has a connecting screw (7) at the bottom.
) and has a general structure fixed to the lower nozzle (6) by the guide simple (4).
is inserted from above. Then, the inserted spent fuel rod (1) is attached to a coil spring (9) welded to the plug (8).
) restricts vertical movement.

The plug (8) is made of the same material as the guide simple, has an air vent hole (8a) in the center, and is attached to the guide simple (4) by welding in this example.

In addition, if the upper nozzle (5) and the guide simple (4) are of a removable type with a screw connection as shown in the figure, the plug (8) cannot be attached using this screw. You can. That is, as shown in FIGS. 2(a) and 2(0), a plug (8
), and as shown in Fig. 3, the guide is screwed into the male threaded body aυ for simple installation. This stopper (8) also has an air vent hole (8a) in the center, and a simple guide (4).
), but the guide is simple (4).
) originally has a hole (not shown) on the side surface, etc., so the chain hole (8a) is not necessarily necessary.

On the other hand, as shown in Fig. 4, if the upper nozzle (5) and the simple guide (4) are fixedly attached by bulge processing, the bulge part (B) can be used to plug it. is also possible.

As a stopper in this case, a one-shear-shaped stopper with a part cut off as shown in Fig. 5 (() and (0) is first considered. In other words, this stopper (8) is shown in Fig. 5(a). As shown, shift the cut parts (8b) and (8b) up and down and retract them, and after inserting them into the bulge part (B), align the cut parts (8b) and (8b) as shown in the same figure (B). Expand it as shown and fix it inside the bulge part (B).

In addition, as another plug (8), there is a C-shaped large ring body as shown in Fig. 6, and this plug (8) can also be expanded from the inside after being inserted into the bulge part (B). It is permanently deformed and fixed in the bulge part (B) as shown in FIG.

Furthermore, Fig. 7 (a) is a plug that can be used regardless of the installation of the upper nozzle and the guide simple.

A tapered pusher plug (8) shown in CU> can be mentioned.

Therefore, the method for transporting spent fuel rods of the present invention usually involves using a simple instrumentation pipe guide or a control rod in a spent fuel assembly different from the fuel assembly from which the spent fuel rods were extracted as described above. The spent fuel rods are inserted into the guiding simple together with an elastic body such as a spring, fixed with a stopper, and transported, and the number of spent fuel rods in the guiding simple can be transported together with the assembly.

In the embodiment, the spring as an elastic body is inserted only above the fuel rod, but the spring may be inserted below the fuel rod or both above and below the fuel rod.

(Effects of the Invention) As explained above, the method for transporting spent fuel rods of the present invention involves inserting the spent fuel rods together with an elastic body into the guide simple of the spent fuel assembly, and plugging the guide. It is transported together with the fuel assemblies mentioned above, and eliminates the need for transporting inspected fuel rods, which conventionally had to be cut into short pieces and transported in spent uranium containers, reducing labor and costs, resulting in extremely efficient transport. In addition, the elastic body absorbs vibrations during transportation to prevent damage to the fuel rods, and since the fuel rods are incorporated into a part of the assembly, they can be easily accepted at reprocessing plants. It has many excellent effects, and its practical value is extremely large in terms of workability and economy.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a guide simple used in the transportation method of the present invention, Fig. 2 (a) is a sectional view showing an example of a stopper, and Fig. 2 (b) is a plan view of the same. , Fig. 3 is a cross-sectional view showing the attached state of the stopper, Fig. 4 is a cross-sectional view showing another example of the guide simple used in the transportation method of the present invention, and Fig. 5 (() and (U) are other examples). 6 is a perspective view showing another stopper, FIG. 7(A) is a front view showing still another stopper, and FIG. 7(III) is a plan view of the same. (1) )...Fuel rod, (3), (4)...Simple guide, (5)...Upper nozzle, (6)...Lower nozzle, (8)...Bung, (9)... ...Spring. 7 4 Figure 7 Figure 8 Procedural amendment (method) Case description 1990 Patent Application No. 278031 Address 3-23-5 Nishi-Shinbashi, Minato-ku, Tokyo Name Nuclear Fuel Industry Co., Ltd. Company representative Kaoru Shimizu 4゜

Claims (1)

[Claims] 1. When transporting spent fuel rods extracted from fuel assemblies for inspection, etc., the fuel rods are simply inserted into other spent fuel assemblies, and an elastic body is placed on one or both the top and bottom of the spent fuel rods. A method for transporting spent fuel rods, which comprises inserting a rod, plugging the rod above the guide simple, and transporting the fuel rod together with the fuel assembly.