JPH0638119B2 - Radioactive waste extinction processing device and extinction processing method - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

This invention irradiates a radioactive waste containing a long-lived radionuclide with γ-rays to convert the long-lived radionuclide in the waste into a stable nuclide or a short-lived radionuclide. TECHNICAL FIELD The present invention relates to a radioactive waste extinction processing apparatus and extinction processing method, and more particularly to a radioactive waste extinction processing apparatus and extinction processing method improved in terms of extinction processing amount and energy efficiency.

2. Description of the Related Art Currently, a large amount of high-level radioactive waste is generated and accumulated by operating a nuclear facility such as a nuclear reactor. Conventionally, high-level radioactive wastes of this type were stored in a solidified body such as glass in a strictly confined manner, and waited until the radioactivity naturally disappeared due to the collapse, so it was especially important to recycle spent fuel. It is contained in the high-level radioactive waste generated during the treatment process. Fission products (EP), such as strontium ,. Actinides (Np, Am, Cm, etc.) generated by nuclear reaction in a nuclear reactor and.
Long-lived radionuclides such as unrecovered uranium and plutonium must be safely managed for many years,
As the amount of storage increases, it has become difficult to secure and secure a storage location. On the other hand, recently, to shorten the storage period of radioactive waste and reduce the storage location, radioactive waste containing long-lived radionuclides as described above is irradiated with γ-rays with an energy of 10 to 25 MeV. Therefore, the applicant of the present invention has proposed a method for treating radioactive waste in which a long-lived radionuclide in waste is converted into a stable nuclide or a short-lived radionuclide (Japanese Patent Application No. 59-48698). ).

[Problems to be Solved by the Invention]

However, in order to treat a large amount of waste coming out of a nuclear reactor by the above method, technical development of a large amount of treatment by an accelerator is necessary. In addition, this method causes a large amount of energy to be used to operate the accelerator, resulting in poor energy efficiency. Therefore, improvements aimed at increasing the amount of elimination processing and improving energy efficiency have been desired. In the above method, only γ-rays with an energy of 10 to 25 MeV, that is, the γ-ray (γ, n) reaction is used to extinguish the radioactive waste, and the neutrons generated by the (γ, n) reaction are effectively used. Not not. Therefore, the present invention is based on the above method, and particularly improves the target portion so that neutrons can be effectively used,
It is an object of the present invention to provide a annihilation treatment device and annihilation treatment method for radioactive waste, which are improved in terms of annihilation treatment amount and energy effect.

[Means for Solving the Problems]

This invention uses a fast reactor as a target furnace, and arranges a radioactive waste and a fuel body inside and outside the target furnace, respectively, and further adds a moderator to the inside of the radioactive waste or as a radioactive waste. An electron beam accelerator is installed at a position that irradiates radioactive waste with γ-rays while being connected to the fuel body, and the radioactive waste is irradiated with γ-rays generated by the electron beam accelerator (γ, n) reaction Then, the radioactive waste is extinguished, and then the fuel body is irradiated with neutrons generated by the reaction to maintain a high neutron flux, and at the same time, the heat generated in the target reactor is converted into electric power and supplied to the electron beam accelerator. Further, the above-described object is achieved by irradiating the radioactive waste with the neutrons and extinguishing the radioactive waste by the (n, γ) reaction.

[Action]

According to the present invention, by supplying power to the electron beam accelerator, the γ-rays generated by the electron beam accelerator are irradiated to the radioactive waste, and the radioactive waste is extinguished by the (γ, n) reaction and the neutrons are removed. Occurs. When the generated neutrons collide with radioactive waste, the (n, γ) reaction causes the radioactive waste to be extinguished and γ rays are generated.
The γ-rays are again absorbed by the radioactive waste, and the radioactive waste is extinguished by the (γ, n) reaction and neutrons are generated. Furthermore, since the target reactor of the neutrons generated in the above process is a fast reactor, it collides with the fuel body and is multiplied by the chain reaction of nuclear fission to maintain a high neutron flux and the fuel body generates heat. It functions as a nuclear reactor operated in a subcritical state using the neutron as a radiation source. Further, the heat generated in this nuclear reactor is converted into electric power and supplied again to the electron beam accelerator. Further, when the moderator is arranged between the radioactive waste and the fuel body, the fast neutrons in the fuel body region are thermally converted by the moderator and absorbed in the radioactive waste, promoting the (n, γ) reaction of the radioactive waste. To be done.

【Example】

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 shows an example of the radioactive waste elimination processing apparatus of the present invention. This device is an accelerator-reactor hybrid system basically composed of an electron beam accelerator 1 and a target reactor 2. A radioactive waste 3 and a fuel body 4 are decelerated inside and outside the target reactor 2, respectively. The material 5 such as deuterium or Be is arranged in between, and the electron beam accelerator 1 is arranged at a position where the radioactive waste 3 is irradiated with γ-rays. Among them, the target reactor 2 is not a light water reactor but a fast reactor in order to maintain a high neutron flux. That is, the target furnace 2 is the electron beam accelerator 1
The subcritical fast reactor is operated by using the neutrons generated by the γ-ray beam from the electron source as a radiation source, and the electron beam accelerator 1 is operated by the electric power generated by the target furnace 2. In the apparatus having such a structure, a region having a high annihilation treatment rate due to the (γ, n) reaction and a large amount of annihilation treatment rate can be processed in the center of the target furnace 2 containing the radioactive waste 3 ( There is an annihilation processing region due to the (n, γ) reaction. That is, when the radioactive waste 3 is irradiated with γ-rays, the radioactive waste 3 is extinguished by the (γ, n) reaction, and when neutrons collide with the radioactive waste 3, the radioactive waste 3 is extinguished by the (n, γ) reaction. After the treatment, the radioactive waste 3 can be eliminated by any of the (γ, n) reaction and the (n, γ) reaction. On the other hand, since the fuel body 4 is arranged outside of these extinction treatment regions and high neutron flux can be maintained. That is, neutrons collide with the fuel body 4 and are multiplied by a chain reaction of nuclear fission, so that a high neutron flux is maintained. Further, since the moderator 5 is arranged between the radioactive waste 3 and the fuel body 4, the fast neutrons from the fuel body 4 are thermally converted by the moderator 5 and absorbed by the radioactive waste 3 (n,
γ) The radioactive waste 3 is eliminated by the reaction. Using the above apparatus (accelerator-reactor hybrid system), a general nuclear reactor is first operated to accumulate 137 Cs (Fig. 2). Then, in the Cs loading area in the center of the target furnace 2, this 137
When Cs (hereinafter referred to as Cs) is satisfied and the Cs is accumulated, the electron beam accelerator 1 and the target furnace 2 are started. Then, the target reactor 2 extinguishes Cs generated by the reactor and itself, and suppresses the total amount of Cs to a constant value (in FIG. 2). After the reactor is shut down, Cs is reduced to an equilibrium value by the electron beam accelerator 1 and the target furnace 2 (see FIG. 2). This equilibrium value is determined by the amount of Cs generated and the amount of Cs extinguished in the target furnace 2, and the equilibrium value can be finally lowered by gradually reducing the scale of the target furnace 2. The Cs remaining at the end stops the target furnace 2 and disappears only by the electron beam accelerator 1 (in FIG. 2). For example, in a system in which the above extinction processing devices are associated with 32 power generation reactors of 1 million kilowatts, it takes about 5 hours to wait for the decay of radioactivity due to natural decay after the power reactor is stopped.
It can be seen that the need for 00 years can be shortened to about 80 years by the elimination process.

As described above, the present invention has not heretofore been considered by using a fast reactor as a target furnace and arranging radioactive waste and fuel bodies inside and outside the target furnace, respectively. The neutrons generated when irradiating radioactive waste with γ-rays to extinguish the radioactive waste are positively utilized, which enables the hybridization between the radioactive waste extinction processing device and the nuclear reactor. Therefore, the amount of annihilation processing can be increased and the energy efficiency can be improved. Also, by converting the thermal energy obtained by applying the neutrons to the nuclear fuel to electric energy, the power of the electron beam accelerator for irradiating γ-rays can be self-sufficient, and the cost of disposing of radioactive waste can be reduced. It can be carried out. Further, when the moderator is arranged between the radioactive waste and the fuel body, the fast neutrons in the fuel body region are thermally converted by the moderator and absorbed in the radioactive waste, so that the reaction process for extinguishing the radioactive waste is further improved. Further promoted. In addition, the target reactor is
Since it is a subcritical reactor that is operated by using the neutrons generated by the electron beam from the electron beam accelerator as the radiation source, the safety during processing is high.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a radioactive waste extinguishing processing apparatus of the present invention, and FIG. 2 is a graph showing an extinguishing processing effect on the radioactive waste 137Cs of the extinguishing processing apparatus of FIG. . 1 ... Electron beam accelerator, 2 ... Target furnace, 3 ... Radioactive waste, 4 ... Fuel, 5 ... Moderator.

Claims (4)

[Claims] 1. A fast reactor is used as a target furnace, a radioactive waste and a fuel body are arranged inside and outside the target furnace, respectively, and an electron beam accelerator is arranged at a position for irradiating the radioactive waste with γ-rays. A device for disposing of radioactive waste, characterized in that 2. A device according to claim 1, wherein a moderator is arranged between the radioactive waste and the fuel body. 3. A radioactive waste is irradiated with γ-rays generated by an electron beam accelerator to extinguish the radioactive waste by a (γ · n) reaction, and then the fuel body is irradiated with neutrons generated by the reaction. And maintaining a high neutron flux, and irradiating the radioactive waste with the neutrons to extinguish the radioactive waste by (n · γ) reaction. 4. The heat generated in the target furnace by irradiating the fuel body with neutrons generated by the (γ · n) reaction performed by irradiating the radioactive waste with γ rays generated by an electron beam accelerator. The method according to claim 3, wherein the electricity is converted into electric power and is supplied to the electron beam accelerator.