JPH028279B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is directed to nuclear fuel assemblies, particularly during periodic inspections.
This invention relates to an inspection device used for leak inspection of nuclear fission products leaking from a nuclear fuel assembly.

(Prior art) Due to its properties, nuclear fuel assemblies are subjected to periodic inspections after combustion in a nuclear reactor to inspect their integrity and confirm whether they can be used again. After the reactor is shut down to inspect for pinholes in the tubes, they are pulled out of the core and inspected for leaks.

By the way, in leakage inspections during periodic inspections, conventionally the nuclear fuel assemblies are taken out of the reactor using a fuel exchange crane, and the nuclear fuel assemblies are separately transported to a separate pool for each inspection. Stored in a storage rack within the pool until the storage is completed. This stored fuel assembly is then placed in a shipping can and sealed with a lid, where the fuel assembly is placed under adiabatic conditions to raise its temperature, which increases the pressure inside the fuel rod cladding tube. Fission products were allowed to leak through pinholes, etc. present in the cladding tube, and the presence or absence of fission products eluted into water or gas was determined by analyzing the water or gas.

However, in this conventional method, after the nuclear fuel assembly is taken out of the reactor and transported to the pool, it is necessary to transport it between the storage rack and the leakage fuel inspection equipment, which not only wastes working time but also reduces work efficiency. There was a problem.

Therefore, in recent years, we have been aiming to improve this, particularly by omitting the transfer of fuel assemblies from storage racks to leakage testing equipment, shortening work time, and improving workability by shielding fuel assemblies. Here, the fuel assembly is placed under adiabatic conditions to raise its temperature, which raises the temperature inside the fuel rod cladding tube and releases the fission products into the water through pinholes in the cladding tube. A method for detecting fission products by leaking water and collecting the water is proposed, as well as an inspection device for this purpose consisting of a storage rack with a closable lid, a water collection mechanism in the storage rack, and a suspension transfer mechanism for nuclear fuel assemblies. has been done. (Refer to Japanese Unexamined Patent Publication No. 58-182593.) (Problems to be Solved by the Invention) However, the inspection device proposed above allows water to enter only from the top and bottom of the storage rack. The problem remains that the temperature rise of the fuel increases accordingly.

In view of the above-mentioned problems, and with the aim of further solving the problems, the present invention improves the structure of the storage rack, reduces the temperature rise inside the storage rack during fuel storage, and improves the fuel storage condition. During the lid closure inspection, the purpose is to prevent water from entering only in the downward direction and to prevent the temperature of the fuel assembly from increasing due to decay heat.

(Means for Solving the Problems) That is, in order to achieve the above object, the present invention provides a storage rack that is surrounded by a peripheral wall, has a lid for opening and closing an upper opening, and stores and stores nuclear fuel assemblies therein. a water collection mechanism attached to the lid of the storage rack and having an upwardly extending hose and pump means to collect water in the storage rack; and a water collection mechanism for collecting water in the storage rack through an upper opening of the storage rack. In the leakage inspection device comprising a suspension movement mechanism for a nuclear fuel assembly to be moved and inserted into the storage rack, the storage rack is further closed by covering at least a portion of the peripheral wall surface of the storage rack. It is constructed by a shielding plate that can be opened and closed.

(Function) Next, to explain the inspection status using the leakage inspection device having the above configuration, during periodic inspection of a used nuclear fuel assembly taken out from a nuclear reactor, the nuclear fuel assembly is usually first inspected for fuel removal. They are pulled out individually from the reactor core using a replacement crane. Then, it is stored in a storage rack placed in a pool located at a distance from the location.

Therefore, in the conventional method, it was necessary to further put the nuclear fuel assembly into a tube and transport it to the location of the leakage inspection device, but the present invention does not require transport and makes the inside of the storage rack a closed space. As a result, decay heat is generated by the decay effect of the radioactive fission products of the nuclear fuel assembly under the adiabatic conditions in the space, raising the temperature inside the assembly, thereby increasing the fuel of the assembly. If the pressure inside the fuel cladding tube increases and there is a pinhole or other damage in the tube, fission products will leak from there into the water between the storage rack and the nuclear fuel assembly. Then, water-soluble products in the leaked fission products are eluted into the water, and the water is collected and the presence or absence of fission products is confirmed using a water analyzer.
The integrity of the fuel cladding of the nuclear fuel assembly is inspected.

At this time, in the above configuration, when the shielding plate of the peripheral wall is open, water will enter from above and below and from the sides, and the temperature rise of the fuel will be correspondingly smaller, making it possible to obtain a good fuel storage condition. close,
When the lid is closed, water intrusion is extremely small only in the downward direction, which has the advantage of supporting the temperature rise of the fuel assembly by decay heat.

(Embodiments) Hereinafter, embodiments of the apparatus of the present invention will be described with further reference to the accompanying drawings.

FIGS. 1 and 2 show an overview of the entire apparatus of the present invention. In the figures, 1 is a used nuclear fuel assembly taken out from the reactor core, and 2 is a part for transporting the fuel assembly 1. The handling tool 3 is a hoist for winding up the wire of the handling tool 2. The handling tool 2 has a fuel assembly holding mechanism 2a at its lower end, and holds the fuel assembly suspended from the lower end. The nuclear fuel assembly is moved up and down into and out of the storage rack 4, thereby forming a suspension movement mechanism A for the nuclear fuel assembly.

On the other hand, 4 is a storage rack, and this storage rack 4 constitutes a main part in the present invention, the details of which are described in the seventh section.
As shown in the figure, for the sake of simplicity, all four surrounding walls are composed of closed walls, and the upper It has an opening 41, and a lid 9 that can be opened and closed is attached to the opening 41.

In this case, the lid 9 may be separate from the storage rack 4, or may be partially connected to the storage rack 4 and rotated to close the upper opening 41. good.

In any case, the storage rack 4 is provided with a lid mounting stand 42 at the lower part of the upper opening 41 so as to conveniently close the lid 9. A mechanism allows it to be placed on a lid holder 42.

The storage rack 4 supports the nuclear fuel assemblies at the bottom 8 as shown in FIG. In order to allow free entry, a vertically penetrable structure is adopted, and the whole is inserted and held within a frame 43 for fixing a storage rack assembled within a pool (not shown).

Next, on the other hand, B in Fig. 1 shows the water collection mechanism;
It consists of a plastic bin 7 placed on land or the like, a hose 5 and a pump for sucking up and collecting water in the storage rack 4 into the plastic bin 7, and the lower end of the hose 5 is connected to the upper opening 41 of the storage rack 4.
When the upper opening 41 of the storage rack 4 is closed by the lid 9, the water collection mechanism B is attached to the storage rack 4 at the same time.

Therefore, the basic part of the leakage testing device of the present invention is constituted by the suspension moving mechanism A for opening and closing the nuclear fuel assembly 1 or the lid 9, the storage rack A, and the water collection mechanism B. During storage, this inspection device first moves a used nuclear fuel assembly 1 taken out from a nuclear reactor core to a storage rack 4 using a handling tool 2 and a hoist 3, and inserts it into the storage rack. Of course, at this time, the bottom surface of the storage rack 4 is in a vertically penetrating state, allowing water to freely enter.

In the above configuration, the device of the present invention is particularly characterized in that the structure of the storage rack 4 is as shown in FIGS. A structure constructed in this way has been adopted.

In the figure, the suspension moving mechanism A and the water collection mechanism B have the structures described above, and the same parts are indicated by the same reference numerals.

Hereinafter, the above structure will be described in detail with reference to FIGS. 7 and 8.As shown in the figure, the two side plates 11 and 12 are opposite each other, and the structure is provided between the two side plates 11 and 12. A pin 1 is attached to a drive rod 15 that is fitted into a vertically elongated guide groove 13, each having a spring 14 at the bottom thereof, so as to be movable up and down.
6, and a shielding plate 10 that supports a fulcrum shaft 17 on both side plates 11 and 12 and rotates about the fulcrum shaft 17 as a driving rod 15 moves up and down. A notch 18 is provided in the side plate portion of the upper part of the drive rod 15, and a protrusion 19 protrudes downward at the bottom of the lid 9 when the lid is closed.
It is inserted so as to press the upper end of the drive rod 15.

Therefore, when the lid 9 is placed on the storage rack 4',
The lower spring 14 is compressed in response to the weight of the lid 9', allowing the drive rod 15 to move downward and causing the shielding plate 1 to move downward.
0 is rotated about its fulcrum shaft 17 to shield the space between both side plates. On the other hand, when the load from the lid 9 is removed, the driving rod 15 moves upward due to the biasing force of the spring 14, and, contrary to the above, the shielding plate is rotated toward the open side using the fulcrum shaft 17 as a fulcrum.

According to this structure, water intrudes only from the top and bottom of the storage rack in the storage rack disclosed in JP-A-58-182593, but in the open state, water intrudes from the top and bottom and from the sides, and the fuel is reduced accordingly. Temperature rise is small, making it possible to obtain good fuel storage conditions, and when the shielding plate is closed and the lid is closed, water intrusion is extremely small only in the downward direction, and decay heat helps to increase the temperature of the fuel assembly. There is an advantage.

Next, a method for performing a leakage test using the storage rack 4' having the above structure will be explained with reference to FIGS. 5 and 6.

The shielding plate 10 is attached to the storage rack 4', and is opened and closed by the weight of the lid 9' to which the pump 6 and hose 5 for water collection are attached, as described above, and during normal storage. Now it's open.

Therefore, the fuel assembly 1 is moved to the handling tool 2 as described above.
and insert it into the storage rack 4' using the hoist 3. In this state, the shielding plate 10 is opened,
The fuel assembly 1 can be stored. Then, when the lid 9' is placed on the storage rack 4' using the hoist 3, the shielding plate 10 is closed by its own weight. (See Figure 6) In this state, the fission products in the fuel cladding tube are eluted into water due to the decay heat of the fuel assembly 1, and water is pumped into the polybin 7 via the pump 6 and hose 5. After collecting and cocooning, use a water analyzer to confirm the presence or absence of fission products, as in the case described above.

In this embodiment, when the fuel assembly 1 is stored, the cladding tube is opened, which improves the circulation of pool water and provides a good storage condition.

Note that the above is a case where there is one storage rack 4 and one water collection mechanism B, but these storage racks 4,
There may be a plurality of water collection mechanisms B, in which case there are a plurality of storage racks 4, as shown in FIG.
The water collecting mechanisms B are arranged side by side, all or part of them are divided to make a common lid 9, and a required number of protrusions are provided on the lid 9 so that it can be operated using one or a small number of hanging moving mechanisms A.

(Effects of the Invention) As described above, the device of the present invention enables leakage inspection work simply by placing a lid equipped with a water collection mechanism on a storage rack. By forming the shielding plate from a plate and opening and closing the shielding plate in conjunction with the opening and closing of the lid, there is no need to move the fuel assembly from the storage rack to another inspection device.
While making it possible to store fuel assemblies, leakage inspection can be easily carried out by simply creating a closed space at the location, which significantly improves the workability of inspection work by simplifying inspections and shortening inspection time. When the shield plate is open, water enters from above and below and from the sides.
This makes it possible to reduce the temperature rise of the fuel and improve the fuel storage condition. In addition, when the lid is closed, the shielding plate is closed, allowing water to enter only in the downward direction, and using decay heat to increase the temperature of the fuel assembly. Overall, the increase in temperature and pressure inside the fuel rod cladding tube promotes the leakage of fission products from pinholes, etc., and is expected to have the effect of increasing inspection efficiency.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 show one of the inspection apparatuses according to the present invention.
These are schematic explanatory diagrams showing examples, in which FIG. 1 shows the fuel assembly during storage, and FIG. 2 shows the state during leakage inspection. Also, Figure 3 A,
B, C, and D are examples of storage racks in the device, in which A is a front view, B is a plan view, C, C, and D are sectional views taken along A-A and B-B in A, respectively. Fourth
The figure schematically shows a variant of the device according to the invention in which a plurality of storage racks are arranged side by side. Furthermore, the fifth
6 and 6 are schematic diagrams showing the inspection device according to the present invention, FIG. 5 during storage, and FIG. 6 during leakage inspection. FIG. 7 is a detailed perspective view of a storage rack used in the above apparatus, and FIG. 8 is a perspective view of a shielding plate. 1... Nuclear fuel assembly, A... Hanging movement mechanism,
B... Water collection mechanism, 2... Handling tool, 3... Hoist, 4, 4'... Storage rack, 5... Hose,
6...pump, 7...polybin, 9,9'...lid,
10... Shielding plate, 41... Storage rack upper opening,
42...Lid mounting stand.

Claims (1)

[Claims] 1. A storage rack that is surrounded by a peripheral wall and has a lid that opens and closes an upper opening for storing nuclear fuel assemblies inside, and a hose that is attached to the lid of the storage rack and extends upward, and a pump means. a water collection mechanism for collecting water in the storage rack; and a suspension movement mechanism for the nuclear fuel assembly for moving and inserting the nuclear fuel assembly into the storage rack through the upper opening of the storage rack. , and a part of the peripheral wall surface of the storage rack is formed by an openable and closable shielding plate that is closed by covering an upper opening of the storage rack. Device.