JPS58196486A - Burnable poison rod - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] FIELD OF THE INVENTION The present invention relates to a burner pull poison rod.

A suitable number of burner poison rods (thick burnable poison rods) are hung down and fixed in clusters along with simple plugs, etc. to the nuclear fuel insert structure, and inserted into a predetermined gap in the nuclear fuel assembly in the reactor. It is used to suppress the reactivity of nuclear fuel.

This burner pull poison rod includes a long zirconium alloy cladding tube 1 with a large number of boron sintered pellets 2 inserted in the axial direction, as shown in Fig. Some have borate glass inserted into the tube.

These burner pull poison rods are
The reactivity of nuclear fuel is suppressed and controlled by absorbing excess neutrons generated in nuclear reactions with boron 10 contained therein, and boron 10 dissipates every time a neutron is absorbed.

Therefore, a burnable poison rod that has been used for a certain period of time loses its function as a burner poison and is disposed of as waste.

Since this waste is radioactive, it is stored separately on the premises of the nuclear power plant, but storage space is required, and the amount of used Minobanapur poison rods that are generated one after another increases. The drawback is that the processing requires a lot of effort and space.

In addition, these burner-pull poison rods sometimes become unusable due to deformation of the absorbent material and stress corrosion cracking of the cladding. Further, when handling a long burner pull poison rod, the long thin cladding tube may be damaged for some reason, resulting in a drawback of low mechanical strength.

The present invention has been made to solve the above-mentioned problems, and it improves the mechanical strength of a long burner-pull poison rod, and even after boron-10 has dissipated, the poison rod remains effective in suppressing the reactivity of nuclear fuel. The purpose of this rod is to provide a burner pull poison rod that can maintain a long life and reduce the amount of radioactive waste that needs to be stored. 10 was dispersed.

The present invention is based on the already known finding that filter stainless steel itself has a small neutron absorbing effect, and has been made by applying this knowledge.

Hereinafter, the present invention will be explained in detail based on examples thereof.

FIG. 2 is an explanatory diagram of a burner pull poison rod 4 made of a stainless steel solid rod 6 in which boron 10 is dispersed.

One end of the stainless steel solid rod 6 is formed with a joint 5 for attachment to a nuclear fuel insert structure (not shown).

The aforementioned boron 10 is added in an appropriate amount to molten steel during the steelmaking stage of manufacturing stainless steel, and as a result is uniformly dispersed within the stainless steel.

When such a burner pull poison rod 4 is used instead of the conventional one, at the beginning of the life when there is a lot of 22'U in the nuclear fuel, the boron 10 dispersed in the stainless steel solid rod 3 is
exhibits a neutron absorption effect and suppresses the reactivity 23
From the middle to the end of life, when rU is decreasing, even if the boron 10 is dissipated, the stainless steel solid rod 6 itself exhibits a corresponding neutron absorption effect.

Therefore, there is no need to discard the boron 10 once it has dissipated, as in the conventional case, and it can be used for neutron absorption.

This is based on the knowledge that stainless steel itself has a slight neutron absorption effect.

Additionally, since the burner pull poison rod 4 is a solid bar made of stainless steel, its mechanical strength is high, and it will not be damaged unlike conventional cladding tubes.

Furthermore, since the burner-pull poison rod has a longer lifespan, it is possible to avoid the need for a large amount of space for storage, etc. when disposing of the rod.

By the way, there is an idea to use a round bar made only of stainless steel as a poison rod.

This poison rod does not contain 10 pieces of parnable boron, so it is only used as a poison rod for fine adjustment, and it is not used as a burner pull poison rod by itself, for example, it is used as a burner pull poison rod. It is always used in conjunction with a burner pull poison rod, which is a stainless steel clad tube with borate glass inserted.

Therefore, it should be noted that it does not have the function of a poison rod.

This is because the above-mentioned poison rod does not contain boron-10, which is a pernable poison, and therefore cannot exert an effective neutron absorption effect by itself in the early stage of the life of the nuclear fuel.

In addition, in the above-mentioned case where a poison rod and a burner pull poison rod are used together, the burner pull poison rod has a thin-walled cladding tube, so its mechanical strength is low, and it is generated one after another as waste, making it difficult to store. The problem is as described above.

As described above, in the present invention, since boron 10 is dispersed in the solid stainless steel rod, its mechanical strength is dramatically improved and there is no possibility of damage due to deformation of the insert.

In addition, the reactivity suppressing effect can be achieved semi-permanently from the beginning to the end of the nuclear fuel's life using only the stainless steel parnable poison rod containing boron 10, and the amount of waste produced is reduced, saving storage space and saving space. There is no need to spend much effort on maintenance.

In addition, the production of conventional burner-pull poison rods requires a complicated process of sequentially inserting pellets into a long cladding tube and then welding and sealing the ends of the rod. It has the advantage of not requiring such an assembly process.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional burner pull poison rod, and FIG. 2 is an explanatory diagram of a burner pull poison rod of the present invention. DESCRIPTION OF SYMBOLS 1... Long cladding tube of zirconium alloy, 2... Alumina sintered pellets containing boron, 6... Stainless steel solid rod in which boron 10 is dispersed, 4... Burner pull poison rod . 71M ■Figure 2

Claims (1)

[Claims] 1. A burner-pull poison rod characterized by having boron 10 dispersed in a solid stainless steel rod.