JPH0235277B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a gas-cooled tritium breeding blanket for a nuclear fusion reactor, and relates to a gas-cooled tritium breeding blanket with improved heat/flow characteristics and tritium breeding characteristics. In a nuclear fusion reactor, for example, a tokamak-type fusion reactor that confines plasma, as shown in FIG. 1, an inner blanket 2, an outer blanket 2', an inner shield 3, an outer shield 3', A toroidal magnetic field coil 4, a poloidal magnetic field coil 5, a diverter 6, an exhaust device 7, etc. are arranged. The inner and outer blankets 2 and 2' are important core components, and are used to produce tritium (tritium), which is the fuel for nuclear fusion, by reacting neutrons generated by the fusion reaction with breeder material. ,
It has functions such as converting the energy of these neutrons into thermal energy that can be used for power generation, etc., and blocking radiation together with a shield.
In this way, the energy possessed by neutrons is converted into a large amount of thermal energy within the blanket, so a coolant is required to remove this and transport it to a system for use such as power generation. A gas coolant such as helium is mainly used because it does not require minimum temperature control of the breeder to continuously recover tritium and is easy to handle. Traditionally, gas-cooled blankets have been made by filling a pressure vessel with a pebble- or block-shaped solid breeding material (such as lithium oxide), and flowing a high-pressure gas coolant through it to directly cool it and recover the produced tritium. A pressure vessel type blanket is used, and a pressure pipe 9 having a structure as shown in Fig. 3 is placed in the pressure piping hole 8 in the box type blanket as shown in Fig. 2 to remove heat and recover tritium. There were two types of pressure tube type blankets that did not apply pressure directly to the blanket container 10, but pressure vessel type blankets used high-pressure coolant, which limited the size of the pressure vessel. There are problems such as an increase in the number of modules and an extremely large number of pipes penetrating the vacuum boundary for confining the plasma, so pressure tube type blankets are currently the mainstream. There are two structures for the pressure tube 9 in the pressure tube type blanket, as shown in Figures 3a and 3b. In Figure 3a, an annular tritium breeder pellet 11 is loaded into the pressure tube 9, and the pressure tube 9 is exposed from both the inside and outside. In this method, heat is removed by a coolant 12. Figure b shows a pressure tube 9 filled with spherical tritium breeder pebbles 13, and a coolant flowing through the pebbles 13 to remove heat. This is a collection method. However, in the method shown in Figure a, since the tritium breeding material pellet 11 is annular, temperature differences are likely to occur and cracks are likely to occur due to thermal stress.Therefore, since the wall thickness is limited, the volume ratio of the structural material increases and the tritium breeding performance is reduced. Furthermore, there are disadvantages such as difficulty in manufacturing the pellets 11 and loading them into the pressure pipe, and in the method shown in Figure b, the pressure loss is excessive because the coolant flows at a considerable speed within the packed bed of the pebbles 13. There is a drawback.

The present invention was made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a gas-cooled tritium breeding blanket for a fusion reactor, which has improved tritium breeding performance and heat removal performance.

The gas-cooled tritium breeder blanket for a fusion reactor of the present invention divides the inside of a pressure tube with a concentric double-walled tube with porous walls, fills the gap between the porous walls with a pebble-shaped breeder material, and creates an inlet coolant flow path from the inside. The coolant is divided into three regions: a breeder region and an outlet coolant flow path, and the coolant is allowed to flow into the breeder region from the inlet coolant flow path, and then introduced into the outlet coolant flow path through the air of the breeder material to be removed from the system. A cylindrical blanket cooling pressure pipe is installed inside the box-shaped blanket container, and a neutron moderator made of graphite or the like is placed around the pressure pipe to reduce the plasma in the container. The neutrons that enter through the first wall that forms the side wall surface are decelerated, the energy of the neutrons is converted into thermal energy, and the heat is removed by the coolant flowing through the cooling pipe installed in the moderator. The tritium transported outside the system and produced by the reaction of neutrons with a pebble-shaped tritium breeder material placed inside the pressure pipe and the thermal energy generated are recovered by the coolant flowing inside the pressure pipe. This is what I did.

An embodiment of the present invention will be described in detail below. FIG. 2 shows a cross-sectional structure of a box-shaped blanket, and the blanket container 10 includes a coolant flow pipe 14 for cooling the container 10, and a manifold section for supplying or recovering coolant to the flow pipe 14. It consists of 15. Inside the container 10 is a moderator 16 that slows down neutrons entering from the first wall 10a constituting the plasma side surface of the container 1 and converts the nuclear energy of the neutrons into thermal energy. A cooling pipe 18 for transporting the thermal energy generated in the system to the outside of the system and a pressure pipe hole 8 containing a pressure pipe containing a tritium breeding material are provided. A pressure pipe 9' having a structure shown in FIG. 4 is installed in the pressure pipe hole 8. Inside the pressure pipe 9', porous cylinders 9a and 9b are arranged in a double layer, and there is a gap between the layers. It is filled with a pebble-shaped tritium breeder material 13. The diameter and number of pressure pipes 9' are set so as to enable average cooling according to the heat generation distribution. Furthermore, the first
A neutron multiplier material 17 made of beryllium or the like is installed between the wall of the container 10 on the wall 10a side and the moderator 16,
Tritium breeding ratio is being adjusted.

Next, the operation of this embodiment configured as described above will be explained. The neutron flux generated by the nuclear fusion reaction is irradiated into the blanket container 10 through the first wall 10a. The neutrons entering the blanket container 10 are multiplied by the neutron multiplier 17 installed in front of the blanket container 10, and repeatedly collide with the atoms of the moderator 16 installed in the container 10. The neutrons are decelerated and their energy is converted into thermal energy and released, which is transported out of the system by cooling pipes 18 suitably disposed between the moderators 16 in the blanket. The pressure pipes 9' are provided in accordance with the heat generation distribution in order to averagely cool the cross section of the blanket, and a pressure pipe with a relatively smaller diameter than the opposite side is installed on the first wall 10a side where the heat generation distribution is large. A large number of them are arranged to prevent uneven cooling. The flow of the coolant is as shown in FIG. 5. A gas coolant such as helium is introduced from the inlet coolant channel 9c and passes through the circular tube 9a with the porous wall to form a storage layer of the pebble-shaped tritium breeder material 13. The propagation material 13 is cooled, passed through the porous-wall circular pipe 9b on the exit side, collected in the exit coolant channel 9d, and discharged out of the system, but at the conventional pressure shown in FIG. Compared to the structure of the pipe 9, the effective flow path length of the packed bed of the proliferation material 13, which causes excessive pressure loss, is short, and the coolant flow rate in the packed bed is also small, so the pressure loss can be reduced. By making the pebble diameter of the propagation material 13 small, the temperature difference in the propagation material 13 can be reduced, so the generation of thermal stress is small, and damage to the propagation material 13 is prevented. In addition, in order to make the flow rate of the coolant passing through the breeder region uniform in the axial direction (poloidal direction) of the pressure tube 9', the number of holes in the perforated wall circular tubes 9a and 9b is changed to increase the flow resistance. Since the flow rate is adjusted, the flow rate is properly distributed and local overheating of the blanket is prevented. On the other hand, the neutrons that have released energy react with the pebble-shaped breeding material 13 in the pressure tube 9' to generate tritium, which is transported with the coolant to the outside of the system through the outlet coolant flow path 9d and recovered. .

As detailed above, the gas-cooled breeder blanket for a fusion reactor of the present invention has a porous concentric double tube installed in the cooling pressure tube, and a pebble-shaped tritium breeder material is placed between the double tubes. Because it is filled, it is possible to construct a pressure pipe with low pressure loss and low thermal stress.Moreover, the diameter and number of pressure pipes can be selected relatively freely, and are adjusted according to the heat generation distribution. It has excellent heat/flow performance, tritium breeding performance, and ease of manufacture, such as being able to obtain good tritium breeding performance and at the same time having excellent cooling performance, making it suitable for conventional gas-cooled breeder blankets for fusion reactors. It can be said to be an epoch-making product that can be replaced.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view schematically showing a tokamak-type fusion reactor, Fig. 2 is a cross-sectional view of a box-shaped blanket, Fig. 3 a and b are cross-sectional views of a conventional pressure tube, and Fig. 4 is a tritium reactor according to the present invention. A cross-sectional view of the pressure tube in the growth blanket; FIG. 5 is an enlarged cross-sectional plan view of the pressure tube. 9...Pressure pipe, 9a, 9b...Porous wall circular pipe, 1
0... Blanket container, 10a... First wall, 1
3... Pebble-shaped growth material, 16... Moderator, 17...
...Neutron multiplier, 18...Cooling pipe for moderator.

Claims (1)

[Claims] 1 The inside of the pressure pipe is divided by a concentric double walled pipe, and the porous walls are filled with a pebble-shaped breeder material, which is divided from the inside into an inlet coolant channel, a breeder region, and an outlet coolant channel. 1. A gas-cooled tritium breeding blanket for a nuclear fusion reactor, characterized in that a pressure tube is installed in a box-shaped blanket container, and a neutron moderator is arranged around the pressure tube.