JPH0334836B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] The present invention relates to a fast breeder reactor in which reactor fuel is stored in a container and a fuel inlet/output machine is used to transfer the reactor vessel and reactor in an inert gas atmosphere. The present invention relates to a bucket of a fuel loading/unloading machine that is filled with liquid sodium as a coolant liquid metal and transferred between the bucket and an external fuel relay device.

[Prior art and its problems] Fuel handling involves installing new fuel as reactor fuel (hereinafter referred to as fuel) into the reactor in a fast breeder reactor, and removing spent fuel from the reactor and performing fuel handling such as cleaning. Insert fuel handling equipment is known as such equipment. Figure 3 is a layout diagram showing the configuration of this fuel handling equipment. In the figure, 1 is a reactor vessel;
Liquid sodium as a liquid metal serving as a coolant is stored inside the reactor, and a reactor core 1a and an in-core fuel storage rack 1b are provided below the liquid level. The fuel exchanger 2 exchanges fuel within the reactor vessel 1, and before loading and unloading fuel from the reactor vessel 1, the fuel exchanger 2 exchanges fuel within the reactor vessel 1.
Fuel is temporarily placed and stored in b. Fuel intake/discharge machine 3
is arranged in the inert gas cell 20a of the fuel transfer cell 20, and fuel is taken in and out by the swing arm 3a of the fuel inlet/output machine 3 through the reactor side chute 1c, which is provided by penetrating the damping plug of the reactor vessel 1. do. The swing arm 3a is connected within the inert gas cell 20a to the transfer port of the swing out-of-core fuel relay device 4, and fuel is transferred between the swing arm 3a and the out-of-core fuel relay device 4.

The fuel transfer cell 20 is composed of the above-mentioned inert gas cell 20a and humid air cell 20b, and the inert gas cell 20a is equipped with a damaged fuel storage facility 6, a new fuel underground truck 7, in addition to the out-of-core fuel relay device 4. A fuel cleaning facility 8 is disposed astride the inert gas cell 20a and the humid air cell 20b, and an underwater fuel storage tank 10 and a cask truck 11 are disposed in the humid air cell 20b via respective delivery ports. In addition, an inert gas cell 20a, a humid air cell 20b
In-cell grippers 5 and 5a for transferring fuel are respectively disposed. Therefore, the fuel placed in the relay container 4a of the out-of-core fuel relay device 4 is transferred between the fuel handling equipment arranged in the fuel transfer cell 20 by the insel grits 5, 5a. Note that the spent fuel is transported to an unloading trailer 13 by an overhead crane 12. In addition, new fuel is delivered to the inert gas cell 2 by an underground trolley 7 from a new fuel storage area (not shown).
It is transported to the delivery port of 0a.

By the way, when handling fuel as described above, the fuel taken in and out of the reactor vessel 1 by the fuel inlet/outlet machine 3 is stored in a fuel bucket, and this fuel bucket is transferred to the swing arm 3a of the fuel inlet/outlet machine 3.
The fuel is transferred between the reactor vessel 1 and the extra-core fuel relay device 4 by swinging the swing arm 3a. FIG. 4 is a sectional view of a conventional fuel bucket, and in the figure, a relay container 4a of an out-of-core fuel relay device 4 is installed through a delivery port to an inert gas cell 20a.
is supported by a flange 4b on the concrete floor of a pit 4c and installed in an inert gas atmosphere. A fuel bucket 16 serving as a container for storing fuel 15 is connected to a traction tool 18 along a guide rail 17 to which the swing arm of the fuel loading/unloading machine connects at the delivery port, and the fuel bucket 16 is connected to a traction tool 18 by operating the traction tool 18 by the fuel loading/unloading machine. It can be taken in and out of the relay container 4a of the external fuel relay device 4. Note that FIG. 4 shows a state in which the fuel bucket 16 is housed in the relay container 4a. The fuel bucket 16 is provided with a siphon pipe 16a on its side wall, and the liquid level 30a of liquid sodium filled in the fuel bucket 16 is set at the opening position of the inner wall of the siphon pipe 16a. The fuel 15 is held by opening a plurality of claws 19a of a gripper 19 of a fuel inlet/output machine (not shown), inserted into a grip portion 15a of the fuel 15, and immersed in liquid sodium 30.

The liquid sodium in the fuel bucket 16 is filled with liquid sodium as a coolant in the reactor vessel, and when it is lifted above the liquid sodium level in the reactor vessel by the fuel loading/unloading machine, it is suspended above the fuel bucket 16. Liquid sodium filled to the end surface flows out from the siphon tube 16a into the reactor vessel, and a liquid level 30a is maintained. Note that this liquid level 30a is set to a height that sufficiently covers the fuel 15. Therefore, when fuel, especially spent fuel, is transferred by the fuel bucket 16, decay heat flows through the coolant flow channels between the plurality of entrance nozzle holes 15b of the fuel 15, the fuel pins in the fuel 15, and the opening 15c at the top. The decay heat is removed by the natural circulation of the liquid sodium in the direction of the arrow through the sodium chloride, and even if an accident occurs during transportation and the sodium stays in the same place for a long time, the decay heat is removed by this natural circulation. By the way, since the fuel 15 in the fuel bucket 16 is in liquid sodium, the claws 19a of the gripper 19 of the incel gripper
The claw operating portion of the gripping mechanism that opens and closes the fuel 15 is operated in liquid sodium to grip and release the fuel 15.

However, in such a structure, the gripper 1
Liquid sodium adheres to the claw operating parts such as 9a, for example, the rotating parts that open and close the claws, and when the liquid sodium is taken out of the liquid sodium in this state and cooled, the claw operating parts of the gripping mechanism, etc. become stuck with the sodium. There is a problem in that it becomes impossible to hold and release the fuel. For this reason, it is necessary to use a heating device to heat and melt the fixed sodium and to frequently clean the grasping mechanism of the gripper, which raises the problem of increased equipment costs and longer refueling time.

[Purpose of the invention]

In view of the above-mentioned points, the present invention provides a fuel inlet/output system that can grip and release fuel in a fuel bucket to transfer fuel without immersing the gripping mechanism of an in-cell gripper in liquid metal that may cause sticking. The purpose is to provide fuel buckets for aircraft.

[Summary of the invention]

According to the present invention, the siphon provided on the side wall of the container housing the reactor fuel is fixed by the grip of the reactor fuel rising due to the thermal expansion of the liquid metal accompanying the decay heat of the spent fuel. The container has an opening on its inner surface exposed above the liquid metal surface, and the effective height of the siphon tube is such that the effective height of the siphon tube remains tilted within the fuel inlet/output device during fuel transfer and when the container containing fuel is stopped. This is achieved by maintaining the liquid metal level which rises due to thermal expansion of the liquid metal.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings. FIG. 1 is a partial cross-sectional view of a fuel bucket of a fuel inlet/outlet device according to an embodiment of the present invention, which is housed in an out-of-core fuel relay device. In FIG. 1 and FIG. 2, which will be described later, the same parts as in the conventional example shown in FIGS. 3 and 4 are given the same reference numerals. In FIG. 1, the structures and functions of the out-of-core fuel relay device 4, relay container 4a, fuel 15, fuel bucket 16, traction tool 18, gripper 19, etc. are the same as those in the prior art, so their explanations will be omitted. In this embodiment, the liquid level A of liquid sodium as a liquid metal, which is a coolant, determined by the inner wall opening of the siphon pipe 16a provided on the side wall of the fuel bucket 16 is transferred from the out-of-core fuel relay device 4 to the downstream fuel handling device. During a short period of about 30 minutes until the fuel 15 is stored, the liquid sodium thermally expands due to the decay heat of the spent fuel and rises to the liquid level B, but the grip part 15a of the fuel 15 does not reach the liquid level. The siphon tube 16a is positioned so as to be exposed to the space above B. Note that the effective height of the siphon tube 16a is higher than the liquid level rise due to thermal expansion during storage, which will be described later. Even if the liquid sodium rises due to thermal expansion, the liquid sodium filled in the siphon tube is prevented from being discharged to the outside of the fuel bucket through the inside of the siphon tube.

With this structure, the grip portion 15a of the fuel 15 stored in the relay container 4a of the out-of-core fuel relay device 4 is located in a space above the liquid sodium level B that has risen due to thermal expansion, so the gripping mechanism of the gripper 19 is The opening and closing of the space above B, that is, the claws of the gripper 19, is performed in an inert gas atmosphere above the liquid level. For this reason, the claw operation part of the gripper 19's gripping mechanism is not immersed in liquid sodium, so sodium does not adhere to the claw opening/closing rotating part of the gripper 19, so sticking due to cooling does not occur, and good claw opening/closing ability is maintained. Can be retained over time.

In addition, in the case of normal fuel transfer, the fuel 15 remains in the fuel bucket 16 for only a short time as described above, so even if the fuel 15 is a spent fuel, its decay heat will not cause the temperature of the fuel to rise abnormally.

Figure 2 shows the spent fuel in the fuel bucket shown in Figure 3 being transported between the external fuel relay device and the reactor vessel along the inclined shute sleeve 22 by the towing tool 18 of the fuel inlet/outlet machine. , shows the state of the fuel bucket 16 whose transfer was relayed and stopped due to an accident. In this case, the sodium liquid level is initially at the liquid level c determined by the siphon tube 16a, but since the grip portion 15a is in an inert gas, natural circulation does not take place within the fuel bucket, the temperature of the liquid sodium rises, and the liquid level increases. Rise. When the liquid level rises to the liquid level D due to a long stop, the fuel 15 is immersed below the sodium liquid level D. Therefore, the natural circulation of the fuel 15 is performed in the direction of the arrow as described above through the entrance nozzle hole 15b and the opening 15c at the top, and the decay heat of the spent fuel is removed and the temperature of the spent fuel is abnormal. No rise occurs, and the sodium liquid level also maintains the liquid level D. In addition, the effective height of the siphon tube 16a is set to such a height that even if the liquid level rises to D, the sodium liquid in the fuel bucket 16 does not spill out through the siphon tube 16a, so the sodium liquid level is maintained. be done.

When the accident recovers and normal conditions return, the fuel bucket should be immersed in the liquid sodium inside the reactor vessel again using the fuel inlet/output machine, cooled, and then raised again into the inert gas cover gas above the sodium liquid level. Therefore, the liquid level in the fuel bucket 16 is the liquid level A determined by the opening position of the inner wall of the siphon pipe 16a.
(See Figure 1). Therefore, the fuel stored in the fuel bucket is gripped and released by the gripper without immersing the gripper's gripping mechanism in liquid sodium again.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the liquid metal level of the fuel bucket containing reactor fuel is determined by the siphon pipe provided on the side wall of the fuel bucket, and is further used during normal transfer of the fuel bucket. The grip part of the nuclear fuel is positioned so as to be exposed above the liquid level which has risen above the liquid level due to the decay heat of the reactor fuel, and the effective height of the siphon tube is adjusted so that the fuel bucket is on the inclined shoot sleeve. In the event of a shutdown due to an accident, the liquid metal level can be maintained even if it rises due to thermal expansion, so the gripper that grips and releases the fuel is always operated in an inert gas above the sodium liquid level. This prevents sodium from adhering to the gripper's gripping mechanism and causing it to stick to the operating parts for opening and closing the claws.Therefore, there is no need for a heating device to melt the adhesion, reducing equipment costs and reducing the frequency of cleaning the gripper's gripping mechanism. The fuel handling time can also be shortened.
In addition, in the event of a transfer accident, even if the fuel bucket stops, the spent fuel's decay heat is absorbed by the thermal expansion of the liquid metal, which causes the liquid metal level to rise and the spent fuel to be covered by the liquid metal, allowing for natural circulation and collapse. This has the effect of effectively removing heat and preventing melting of the fuel.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a fuel bucket of a fuel inlet/outlet machine according to an embodiment of the present invention housed in an extra-core fuel relay device, and Fig. 2 shows a state in which the fuel bucket of Fig. 1 is stopped during transfer along a chute sleeve. 3 is a layout diagram of fuel handling equipment, and FIG. 4 is a partial sectional view showing a fuel bucket of a conventional fuel inlet/output machine housed in an extra-core fuel relay device. 1: Reactor vessel, 3: Fuel inlet/output machine, 4: External fuel relay device, 5: Incel gripper, 15: Reactor fuel, 15a: Grip section, 16: Fuel bucket, 16a: Siphon tube, 19: Gripper.

Claims (1)

[Claims] 1. A container that is filled with liquid metal as a coolant in an inert gas atmosphere, equipped with a siphon on the side wall, and that stores the reactor fuel, and has a grip on the top. In a fuel bucket for a nuclear power plant, the siphon is attached to the inner surface of the container so that the grip of the reactor fuel is exposed above the liquid metal level determined by rising due to the thermal expansion of the liquid metal due to the decay heat of the spent fuel. The siphon tube has an opening, and the effective height of the siphon tube is such that it maintains the liquid metal level that rises due to thermal expansion of the liquid metal when the container containing the fuel is stopped while remaining inclined in the fuel inlet/output machine during fuel transfer. A fuel bucket for a fuel inlet/output machine characterized by the following features.