JPH02156196A - Spent fuel storage for high temperature gas nuclear reactor and its facility - Google Patents

Abstract

PURPOSE:To enable a small sized and easy to handle spent fuel storage by separating fuel rods from graphite blocks of spent fuel-assembly, by storing only fuel rods in a spent fuel storage facility in a nuclear reactor building and by disposing graphite blocks. CONSTITUTION:A fuel assembly 5 is taken out from a reactor core 2 by using refuelling machine, is separated into fuel rods 4 and graphite blocks at an outside of a nuclear reactor 1, the fuel rods 4 are transferred to a spent fuel storage facility 7 in a nuclear reactor building and the graphite blocks from which the fuel rods 4 are extracted are brought out from the nuclear reactor building to be treated as disposing treatment. The fuel rods 4 are placed in holes of graphite blocks and therefore can be easily pulled out by an automatic remote operation. The separated fuel rods 4 are housed in a casing 12 as a group of certain number of the rods and furthermore the casing is inserted into a storage rack 9 and, after plugged with shielding plugs, are transferred to a storage pool 8 which is filled with water, and finally are cooled down and stored.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a storage method for storing spent fuel taken out from a core of a high-temperature gas reactor, and a storage facility for storing spent fuel.

[Conventional technology]

A high-temperature gas reactor is a nuclear reactor designed to have a reactor core structure containing fuel made of graphite, use a gas such as helium as a coolant, and be able to extract a coolant with a high outlet temperature. Its characteristics are as follows. i) Thin air conditions comparable to those of cutting-edge thermal power plants can be obtained, resulting in high plant efficiency (approximately 40%). ii) High safety factor. iii) Environmentally friendly (high thermal efficiency,
This reduces the problem of hot water drainage and releases less radioactivity into the environment). 8I) Since coated particle fuel is used, it is suitable for high temperatures and can obtain high burnup. ■) Utilizing high temperatures, it is suitable for multipurpose uses other than power generation. Japan Atomic Energy Research Institute's High Temperature Engineering Test and Research Reactor (HTTR)
thermal output 30MW, reactor outlet coolant temperature 950
The planned spent fuel storage method will be explained below. i) FIG. 3 is a diagram showing a conventional spent fuel storage method. Conventionally, spent fuel bodies taken out from a reactor core were directly transferred to a spent fuel storage facility and stored. 1i) The core structure of the HTTR is shown in Figure 4. pressure vessel 1
The reactor core 2 housed in the reactor core 2 consists of 150 fuel bodies 5 in which fuel rods 4 are built in graphite blocks 3, which are hexagonal columnar moderators, and 400 other components. FIG. 5 is a perspective view showing the structure of the fuel body 5, and FIG. 6 is a perspective view showing the structure of the fuel rod 4. The fuel body 5 is equipped with a plurality of fuel bodies that are inserted through large holes for fuel rods drilled in the graphite block 3, and has a grip hole in the center that is used as a base for the gripper of the fuel exchanger. ij) Figure 7 is a detailed diagram of the reactor building of a high-temperature gas reactor. Fuel exchanger 11 is connected to the stand pipe at the top of the pressure vessel l.
is connected, the spent fuel is placed on a base with a gripper, and the spent fuel is picked up in blocks and transferred to the spent fuel storage facility 7. ■) Figure 8 is a configuration diagram of a conventional spent fuel storage facility in a reactor building. Figure 8 (A) is a partial partial view, and Figure 8 (B) is a diagram of Figure 8 (A). FIG. 8(C) is a sectional view of the storage rack. The spent fuel transferred from the reactor core 2 is stored in storage racks 9 in stacks of four, and the upper portions of the storage racks 9 are plugged with shielding plugs 10 and placed in the storage pool 8. . The storage racks 9 are immersed in a pool of water within the storage pool 8 to indirectly cool the spent fuel. The spent fuel storage facility 7 in the reactor building of this HTTR is scheduled to store spent fuel for two reactor cores, and is equipped with 63 storage racks 9. ■) Figure 9 is a configuration diagram of the spent fuel storage facility outside the reactor building. Figure 9 (A) is a partial partial view, and Figure 9 (B) is the
FIG. 9(A) is a view taken in the direction of the arrow, and FIG. 9(C) is a sectional view of the storage rack. In FIG. 9, the same parts as in FIG. 8 are given the same numbers. Furthermore, outside the reactor building, in order to store all the spent fuel generated during reactor operation, there is a spent fuel storage facility outside the reactor building that has a structure similar to the spent fuel storage facility described above. The reactor building will have a capacity to store spent fuel for 10 cores, and the spent fuel storage facility in the reactor building will receive spent fuel that has been stored for attenuation for two years for long-term storage. In the spent fuel storage facility outside the reactor building, a storage rack 9 containing a plurality of fuel bodies 5 is arranged in a storage cell 13, and the storage rack 9 is cooled by sending air in the direction of arrow B.

[Problem to be solved by the invention]

A,L However, spent fuel must be handled with care because it contains a large amount of nuclear material, and the spent fuel storage facility that stores this spent fuel must meet the following safety design requirements. There is. ) Removal of decay heat from spent fuel. ii) Criticality prevention. iii) Radiation shielding. ■) Earthquake resistance. ■) Containment of radioactive materials. In order to meet these many demands, spent fuel storage facilities require a large amount of space, reliability, heat removal system, concrete shielding several meters thick to shield from radiation, and strong construction to withstand expected earthquakes. This requires a large support structure, which occupies a large amount of space and cost in nuclear power generation facilities. B. Since the HTTR is a high-temperature gas reactor test and research reactor, its handling methods and storage capacity are as described above, but in future demonstration reactors, the spent fuel storage capacity will increase as the reactor output increases. This is expected to lead to an increase in construction costs. Therefore, a small-scale and low-cost spent fuel storage facility is required relative to the power plant capacity. This invention is small in scale compared to the capacity of the power plant, and the above purpose is to separate the fuel rods and graphite blocks of a spent fuel body,
This is achieved by a method for storing spent fuel for a high-temperature gas reactor, in which only the fuel assembly is stored in a spent fuel storage facility in a reactor building, and the graphite block is discarded. Furthermore, a casing for accommodating a plurality of fuel rods separated from the spent fuel body, a storage rank for storing the plurality of casings, and a storage rank arranged in the reactor building for accommodating the plurality of storage racks and filled with water. This is achieved by a spent fuel storage facility for a high-temperature gas reactor, which is characterized by comprising a storage pool.

[For use]

Since the spent fuel body is separated into fuel rods and graphite blocks, the graphite blocks have less radioactivity and can be disposed of as waste. Since fuel rods stored as spent fuel have significantly reduced weight and volume compared to fuel bodies, spent fuel storage facilities can be downsized.

【Example】

The present invention will be described in detail below based on the drawings. FIG. 1 is a diagram showing a spent fuel storage method for a high-temperature gas reactor according to an embodiment of the present invention, in which fuel bodies 5 are taken out from the reactor core 2 using a refueling machine, and fuel rods 4 and graphite particles are removed outside the reactor 1. - The fuel rods 4 are separated from the Z-type 3 and transferred to the spent fuel storage facility 7 inside the reactor building, and the graphite block 3 from which the fuel rods 4 have been removed is carried outside the reactor building as disposal. FIG. 2 is a block diagram of a spent fuel storage facility according to an embodiment of the present invention. FIG. 2(A) is a partial sectional view of the spent fuel storage facility, and FIG. 2(B) is a perspective view of the casing of FIG. 2(A). Since the fuel rods 4 are fitted into holes in the graphite block 3, they can be easily extracted by automatic remote control. The separated fuel rods 4 are housed together in a casing 12, further inserted into a storage rack 9, plugged with a shielding plug 10, and then transferred to a storage pool 8 filled with water for cooling and storage. The spent fuel storage facility 7 includes a casing 12 that stores a plurality of fuel rods 4, a storage rack 9 that stores the plurality of casings 12, and a plurality of storage racks 9 that are placed inside the reactor building and filled with water. It consists of a storage pool 8 that houses the Furthermore, since the graphite block 3 from which the fuel rods 4 have been removed has low radioactivity, it can be easily disposed of as solid waste without being subject to the strict restrictions stipulated for spent fuel as in the past.

【Effect of the invention】

According to this invention, the fuel rods and graphite blocks of a spent fuel assembly are separated, only the separated fuel rods are stored in a spent fuel storage facility in a reactor building, and the graphite block is disposed of. This has the following effect. i) The weight of the fuel rods stored in the spent fuel storage facility will be approximately 30% of the conventional one, and the volume ratio will be approximately 60% of the conventional one. lI) This can be achieved by reducing the weight and volume of the stored items. (Mountain) The above effect becomes more effective as the output of a nuclear power plant increases.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a spent fuel storage method for a high-temperature gas reactor according to an embodiment of the present invention, and FIG. 2 is a block diagram of a spent fuel storage facility for a high-temperature gas reactor according to an embodiment of the present invention. (A) is a partial sectional view of the spent fuel storage facility, Figure 2 (B) is a perspective view of the casing in Figure 2 (A), and Figure 3.
The figure is a diagram showing a conventional spent fuel storage method, Figure 4 is a core configuration diagram of a high-temperature gas reactor, and Figure 5 is a
A perspective view showing the structure of the fuel body in the high temperature gas reactor shown in Figure 6.
The figure is a perspective view showing the fuel rod structure of the fuel assembly in Figure 5, Figure 7 is a Toritake diagram of the high temperature gas reactor building, and Figure 8 is a configuration diagram of a conventional spent fuel storage facility in the reactor building. So, Figure 8 (A
) is a partial sectional view, FIG. 8(B) is a view in the direction of arrow A in FIG. 8(A), FIG. 8(C) is a storage rack configuration diagram in FIG. 8(A), and FIG. FIG. 9(A) is a partial sectional view, FIG. 9(B) is a view taken in the direction of arrow A in FIG. 9(A), and FIG. FIG. 9(C) is a block diagram of the storage rack of FIG. 9(A). 1: Pressure vessel, 2: Core, 3: Graphite block, 4: Fuel rod, 5: Fuel body, 6: Stand pipe, 7: Spent fuel storage facility, 8: Storage pool, 9: Storage rack, lO: Shielding Plug, 11: Fuel exchanger, 12: Casing. Figure (human gu't+dedication) (L 艷、decay) 0.7 gu) Lamp π 粁 体 Ｇ Ｇ Ｇ Ｇ Ｇ fig. (A) Graph ○○○○0O (B) (C) Graph

Claims (1)

[Scope of Claims] 1) A spent fuel storage method in which a spent fuel body consisting of graphite blocks and fuel rods of a high-temperature gas reactor is taken out from a reactor core and stored, wherein the fuel rods and graphite blocks of the spent fuel body are A spent fuel storage method for a high-temperature gas reactor, characterized in that the fuel rods are separated from the fuel rods, and only the fuel rods are stored in a spent fuel storage facility in a reactor building, and the graphite blocks are discarded. 2) In a spent fuel storage facility that takes out and stores spent fuel bodies consisting of graphite blocks and fuel rods from a high-temperature gas reactor core, a casing that accommodates a plurality of fuel rods separated from the spent fuel bodies; , a spent fuel storage for a high-temperature gas reactor, comprising a storage rack for storing the plurality of casings, and a storage pool filled with water and arranged in a reactor building and accommodating the plurality of storage racks. Facility.