JPH0114957Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a slope for carrying in and out of fuel in a fast breeder reactor, and in an emergency when spent fuel is stopped being carried in and out of the slope, the fuel is cooled and deactivated by decay heat. This invention relates to a slope for carrying in and out of fuel which prevents overheating of the fuel bucket and slope and shields radiation.

Fast breeder reactor fuel transfer equipment requires double or triple safety measures for radiation protection.

An overview of the fuel transfer equipment of a fast breeder reactor is explained with reference to FIG. 1. Slopes 3 and 3' for carrying fuel into and out of the reactor vessel 1 and the external fuel storage tank 2 are connected to fuel transfer cells in an Ar gas atmosphere. Fuel is transferred by a fuel bucket 6 which is provided protruding within the fuel bucket 4 and is moved up and down within the slopes 3, 3' by a fuel bucket drive device 5. That is, the spent fuel in the reactor tank 1a of the reactor vessel 1 is placed in a fuel bucket 6, lifted up by the drive device 5 through the slope 3, and stored in the movable truck 7, and then moved by the swing movement of the movable truck 7. After that, the fuel bucket 6 is suspended by the drive device 5 through the slope 3' and stored in the out-of-core fuel storage tank 2. Also, fresh fuel in the out-of-core fuel storage tank 2 is put into a fuel bucket 6 and passed through the ramp 3' to the drive device 5.
Then, the movable truck 7 swings to stop at the slope 3, and then the fuel bucket 6 is lowered down the slope 3 by the drive device 5. It is accommodated in the core 1a of the reactor vessel 1.

The slopes 3, 3' are closed by port valves 8 except when fuel is being carried in and out.

By the way, in the fuel transfer equipment for such a fast breeder reactor, if the fuel bucket drive device 5 breaks down during operation, or if the spent fuel being transferred stops in the slope 3 or 3' due to an earthquake or the like, and becomes unable to move. If
The decay heat of the spent fuel may cause the fuel protection pipe to melt and damage, and not only the fuel bucket 6 but also the ramp 3 or 3' will be overheated.

When such a situation arises, manual repairs are extremely dangerous and difficult.

Furthermore, when fuel is carried in and out under normal conditions, the liquid sodium filled in the reactor vessel 1 and the ex-core fuel storage tank 2 may adhere to the fuel bucket and cause the truck to move down the ramp. If this solidifies, it will be difficult to move the fuel bucket, and there is a possibility that it will not be possible to carry in and out the fuel.

The present invention was developed to solve this problem, and in an emergency when spent fuel is stopped in the slope, the spent fuel is cooled in the slope to prevent melting of the fuel protection pipe due to decay heat and to prevent the fuel from melting. A ramp for loading and unloading fuel that stops overheating of the bucket and ramp, shields radiation leaking along the ramp, and prevents sodium from adhering to the tracks of the ramp during normal fuel loading and unloading. It is intended to provide a path.

Hereinafter, an embodiment of the ramp for carrying in and out of fuel according to the present invention will be described with reference to FIG. 2, only with respect to the ramp 3 of the reactor vessel 1. The ramp 3 is constructed by inserting an elliptical track 10 into a cylindrical guide pipe 9 (see Figs. 3 to 6).The fuel bucket 6 shown in Fig. 10. On both sides of the track 10 inserted into the guide tube 9, a space having a half-moon shape in cross section is formed between the track 10 and the inner peripheral surface of the guide tube 9, as shown in FIG. A jacket 12 and an inner jacket 13 are inserted, and coolant flow paths 14 and 15 are formed. The coolant channels 14 and 15 are bent in a hook shape with respect to the longitudinal direction of the slope 3, and the longitudinal direction of the coolant channels 14 and 15 is blocked by hook-shaped bent portions 16 and 17. .
The hook-shaped bent portions 16 and 17 are formed by changing the wall thicknesses of the outer jacket 11 and the inner jacket 13 in the middle, and bending the intermediate jacket 12 accordingly. The coolant channels 14 and 15 are formed by overlapping the jackets 11, 12 and 13 with a spacer portion 18 in between. In Figure 2,
19 is a coolant inlet, and 20 is a coolant outlet. The coolant inlet 19 penetrates to the inner coolant flow path 15, and the coolant outlet 20 is provided in the outer coolant flow path 14. ing. A space having a half-moon shape in cross section below the coolant channels 14 and 15 is filled with a heat insulating material 21, which blocks heat from the core 1a and prevents the slope from flowing from the fuel transfer cell 7 to the core 1a. Thermal effects on the penetrations are reduced. Further, a sleeve 22 is further provided outside the guide tube 9 in the inclined path penetration part to form an annular space 23 to reduce the thermal influence on the inclined path penetration part. 24
is a bellows for absorbing thermal expansion of the slope 3 at the support portion of the slope 3.

The slope for carrying in and out of fuel in the reactor vessel 1 configured as described above, when carrying in and out of fuel under normal conditions, supplies high-temperature argon gas from the coolant inlet 19 to the coolant flow path 15. Let it flow, track 10
The spent fuel is heated from the outside, and the spent fuel is put into the fuel bucket 6 from the reactor core 1a in the liquid sodium that is deposited in the track 10, that is, the liquid sodium filled in the reactor vessel 1, and the track 10 on the ramp 3 is suspended. The liquid sodium deposited inside the track 10 is caused to melt and flow down to prevent it from depositing and solidifying inside the track 10.

Now, in an emergency situation where the fuel bucket drive device 5 malfunctions during operation due to some reason, or when the spent fuel being transferred stops in the slope 3 due to an earthquake or the like and becomes unable to move, If a long period of time elapses, the decay heat of the spent fuel may cause the protective tube that protects the fuel to melt and damage the fuel bucket 6 as well as the track 1 on the ramp 3.
0 is overheated. At this time, the coolant flows in from the coolant inlet 19 and is supplied into the coolant passage 15, and the spent fuel is cooled by the coolant from both sides of the track 10, and the decay heat of the spent fuel is used in the protection tube. This prevents the fuel bucket 6 and the track 10 of the ramp 3 from overheating. The coolant flowing in the coolant flow path 15 is located outside the upper and lower ends of the coolant flow path 1.
4 and is discharged from the coolant outlet 20 in the middle and high part. Further, radiation leaking from the core 1a along the inclined path 3 is blocked by the hook-shaped bent portions 16 and 17 of the coolant channels 14 and 15.

To explain this point in detail, Figure 2 shows the structure of the ramp 3 for carrying in and out of fuel, and also shows the structure of the roof slug corresponding to the lid of the reactor vessel (main vessel). As shown in the figure, a heat insulating layer 26 for blocking heat from the core and a radiation shielding layer 27 for blocking radiation are provided. The slope 3 for carrying in and out of fuel passes through this roof slug 25, and the slope 3 is also required to have a heat insulation function and a radiation shielding function like the roof slag 25. In FIG. 2, the outer jacket 11, the middle jacket 1
2. The inner jacket 13 is made of a radiation shielding member, and 21 is a heat insulating material.

In this embodiment, in order to flow argon gas for preheating and cooling into the outer jacket 11, intermediate jacket 12, and inner jacket 13, coolant passages 14, 1 are used.
5 is set. These coolant passages 14, 15 do not contribute at all to shielding radiation from the core. This is because radiation, like light, has the property of traveling in a straight line. However, in the middle of the coolant passages 14 and 15, there is a hook-shaped bent portion 1 bent at right angles to the longitudinal direction.
6 and 17, the radiation is blocked by the radiation shielding members of the outer jacket 11 and the intermediate jacket 12 at the hook-shaped bent portions 16 and 17.

As described in detail above, according to the ramp for carrying in and out of fuel according to the present invention, by introducing high temperature argon gas into the ramp during fuel transfer, the track of the ramp is heated and the sodium adhering inside the track is melted and flowed down. coagulation can be prevented. In addition, when spent fuel stops in the ramp during fuel transfer, the trucks and spent fuel can be cooled by introducing a coolant, such as low-temperature argon gas, into the ramp.
It is possible to prevent melting of the fuel protection pipe and overheating of the fuel bucket and slope track due to the decay heat of the spent fuel. In addition, since the space between the slope track and the guide tube is shielded by a jacket made of shielding material that forms a hook-shaped coolant flow path, radiation leaks from the core into the fuel transfer cell along the slope. It has excellent effects such as not causing any problems.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the entire fuel transfer facility of a fast breeder reactor, FIG.
The figure is a diagram showing one half of the cross section taken along the line A-A in FIG. 2, and FIG. 4 is a diagram showing one half of the cross section taken along the line B-B in FIG.
5 is a diagram showing one half of the cross section taken along the line C--C in FIG. 2, and FIG. 6 is a diagram showing one half of the cross-section taken along the line D--D in FIG. 3... Slope, 9... Guide pipe, 10... Track, 11... Outer jacket, 12... Intermediate jacket, 13... Inner jacket, 14, 15...
...Coolant flow path, 16, 17...Hook-shaped bent portion.

Claims (1)

[Scope of utility model registration request] A coolant circulation circuit is constructed using a shielding material in the space between the inner circumferential surface of the guide tube and the elliptical track inserted into the guide tube on the ramp for carrying in and out fuel between the reactor vessel and the ex-core fuel storage tank. and the coolant circulation circuit is bent in a hook shape with respect to the longitudinal direction of the slope, so that when the fuel stops in the slope, the fuel is cooled and radiation is shielded at the same time. A slope for carrying fuel in and out of a breeder reactor.