JP7588611B2 - Fuel debris disposal method - Google Patents

Description

The present invention relates to a method for treating fuel debris in a nuclear power plant.

The fuel debris from the Fukushima Daiichi Nuclear Power Plant (1F) will be stored for a while after it is removed from the reactors. Because the fuel debris contains radioactive materials such as nuclear fuel material and fission products, it needs to be processed into a stable form and then ultimately disposed of safely.

Radioactive waste generated from nuclear power generation and reprocessing is stably solidified and then buried in various disposal sites depending on its properties. High-level radioactive waste generated from reprocessing contains radioactive materials with long half-lives, so it is considered that it will be stably vitrified, then treated with multiple barriers and disposed of in a geological repository.

Since fuel debris is produced by melting spent fuel, it contains radioactive materials with long half-lives. Therefore, in order to ultimately dispose of the fuel debris, it is necessary to first process it into waste forms that will remain stable for the long term, and then dispose of it in a way that will ensure safety for the same period.

For these reasons, one of the most promising methods for processing and disposing of fuel debris is to convert it into stable vitrified waste and dispose of it in a geological repository, as is the case with high-level radioactive waste generated during reprocessing.

An example of a typical composition of high-level radioactive waste (solidified glass) (unit: wt%) is given in Non-Patent Document 1 and is shown in Table 1.

In vitrified waste, radionuclides are trapped in the glass matrix to prevent them from being released. As shown in Table ₁ , the base material of glass is mainly _SiO2 or _B2O3 , and the radionuclides trapped are oxides of fission products (FP) and oxides of actinides (AC). According to Table 1, the ratio of the amount of AC oxides to FP oxides is approximately 1:14 for composition A and approximately 1:4 for composition B. In other words, vitrified waste is characterized by having less AC oxides than FP oxides, and it can be said that the ratio of AC oxides to FP oxides in typical vitrified waste is in the range of 1:4 to 1:14.

On the other hand, in Non-Patent Document 2, Washiya et al. estimate the amount of fuel debris at the Fukushima Daiichi Nuclear Power Plant (1F). Based on the estimates by Washiya et al., the amount of fuel debris was set assuming that the amount of concrete generated is roughly equal to the amount of nuclear fuel material, as shown in Table 2.

On the other hand, Patent Document 1 describes fluorination treatment as a method for recovering nuclear fuel material from fuel debris.

That is, Patent Document 1 describes a method for shortening the time required to recover molten nuclear fuel material by supplying fluorine gas into a reactor pressure vessel surrounded by a reactor containment vessel, reacting the fluorine gas with the uranium and plutonium contained in the fuel debris present in the reactor pressure vessel to generate volatile uranium fluoride and volatile plutonium fluoride, and guiding the generated volatile uranium fluoride and volatile plutonium fluoride from the reactor pressure vessel to a cold trap present outside the reactor containment vessel, solidifying them in the cold trap, and recovering them.

JP 2016-48209 A

JNC TN8400 99-085 (1999). T. Washiya et al., “Study of Treatment Scenarios for Fuel Debris Removed from FUKUSHIMA DAIICHI NPS”, Proceedings of ICONE-23, ICONE23-1953, May 17-21, 2015, Chiba, Japan (2015).

The fuel debris is composed of nuclear fuel material derived from the fuel, cladding tube material, structural materials, and concrete, and the representative components are assumed to be UO ₂ , Zr, Fe, and SiO ₂ , respectively.

When considering vitrifying fuel debris as is, it is necessary to classify each component of the fuel debris as either a glass matrix or a target for containment.

First, uranium, which is a nuclear fuel material, is an actinide element, so it corresponds to AC oxides to be trapped in a glass matrix. On the other hand, _SiO2 in concrete is a component of glass, so it corresponds to a glass matrix. Zr in the cladding tube material and Fe in the structural material are not included in the glass matrix, or even if they are included, the amount is very small, so it is considered appropriate to consider them as targets to be trapped in a glass matrix, and since Zr and Fe are not actinide elements, it is appropriate to classify them as FP oxides.

When classified in this way, the ratio of AC oxides to FP oxides to be vitrified based on the quantities in Table 2 is evaluated to be approximately 1:0.8, which shows that the proportion of AC oxides in fuel debris is very high. In other words, when vitrifying fuel debris, the ratio falls far outside the range of AC oxides to FP oxides in existing vitrified bodies, so it is difficult to vitrify fuel debris as is.

The above-mentioned Patent Document 1 and Non-Patent Documents 1 and 2 do not disclose any measures to solve the above-mentioned problems.

The present invention has been made in consideration of the above points, and its purpose is to provide a method for treating fuel debris by fluorinating the fuel debris, fluorinating and volatilizing the nuclear fuel material, separating it, and converting the remaining fluoride residue into an oxide and then vitrifying it, thereby ultimately turning the fuel debris into a vitrified body suitable for disposal, and by providing a proven composition ratio during vitrification that makes vitrification easier.

The inventors thought that since nuclear fuel material is a resource, it could be selectively recovered from the fuel debris and the remaining material could be vitrified as waste.

That is, in order to achieve the above-mentioned object, the fuel debris processing method of the present invention is a fuel debris processing method for converting the fuel debris into a vitrified body, the fuel debris is fluorinated in a halogenation treatment step to volatilize nuclear fuel material, and the remaining fluoride residue is converted into an oxide, and then the obtained oxide is mixed with a glass base material to form a vitrified body,
The halogenation treatment step is carried out in multiple stages,
The fuel debris is reacted with excess fluorine gas in a first halogenation treatment step, and silicon fluoride, excess fluorine gas B, oxygen gas B, and nuclear fuel material A are generated as volatile components by the halogenation in the first halogenation treatment step, and these are sent to a gas separation step A to separate only the nuclear fuel material A,
On the other hand, the fluorinated residue A fluorinated in the first halogenation treatment step is sent to a second halogenation treatment step, in which it is reacted with fluorine gas, and the fluorinated residue A is halogenated in the second halogenation treatment step to generate nuclear fuel material B, excess fluorine gas A and oxygen gas A as volatile components, which are sent to a gas separation step B to separate only the nuclear fuel material B,
Furthermore, the fluorination residue B fluorinated in the second halogenation treatment step is sent to an oxidation treatment step, in which the fluorination residue B is reacted with water vapor to convert its chemical form into an oxide, and the resulting solid is sent to a vitrification step as a waste material, and in the vitrification step, the waste material and a glass base material are melted, and then cooled and solidified to obtain a vitrified body .

When _UO2 , a nuclear fuel material, reacts with fluorine gas, it volatilizes as hexafluoride (sublimation point: 56.5°C), as shown in formula (1).

In addition, when _SiO2, a concrete component, reacts with fluorine gas, it volatilizes as tetrafluoride (sublimation point: -95.7°C), as shown in formula (2).

As shown in equations (3) and (4), Zr and Fe react with fluorine gas to produce fluorides, but because they have low volatility, they remain as solids.

The fluorinated and volatilized uranium can be recovered and effectively used as nuclear fuel material, so the residue after fluorination (hereafter referred to as fluoride residue) ultimately becomes waste. Since fluoride cannot be vitrified as it is, it is converted to oxide before vitrification, and the weight of each substance when fluoride residue is converted to oxide is shown in Table 2.

In principle, all U and Si react with fluorine gas and volatilize as a gas, but the weight of the fluorination residue was evaluated conservatively assuming a volatilization rate of 90% during fluorination.

When fluoride residues are solidified into glass, as in the case of fuel debris mentioned above, the nuclear fuel material corresponds to AC oxide, while the cladding tube material and structural materials correspond to FP oxide, being other solidification targets.

In this case, the amount of AC oxide is 30t and the amount of FP oxide is 318t, making the ratio of AC oxide to FP oxide approximately 1:11. This ratio is within the range of 1:4 to 1:14, which is the ratio of AC oxide to FP oxide in typical vitrified waste, and can be said to be easy to vitrify.

In other words, by first fluorinating the fuel debris, then converting the fluoride residue into an oxide and then vitrifying it, the fuel debris can be turned into a vitrified body suitable for geological disposal, and the vitrification process becomes easier because the composition ratio is proven.

According to the present invention, fuel debris is fluorinated to volatilize and separate the nuclear fuel material, and the remaining fluoride residue is converted to oxide and then vitrified. This ultimately makes it possible to turn the fuel debris into a vitrified body suitable for disposal, and also makes it easier to vitrify because the composition ratio is proven to be effective when vitrifying.

1 is a flowchart showing a first embodiment of a method for treating fuel debris according to the present invention. 1 is a flowchart showing a second embodiment of the fuel debris processing method of the present invention.

The fuel debris processing method of the present invention will be explained below based on the illustrated embodiment.

The first embodiment of the fuel debris processing method of the present invention will be explained with reference to FIG. 1.

Figure 1 is a flow chart showing a first embodiment of a method for treating fuel debris. As shown in Figure 1, the method for treating fuel debris in this embodiment includes a first halogenation treatment process 1, a second halogenation treatment process 2, a gas separation process A6 in the first halogenation treatment process 1, a gas separation process B3 in the second halogenation treatment process 2, an oxidation treatment process 4, and a vitrification process 5.

The fuel debris processing method of this embodiment is described in detail below.

The fuel debris 10 is reacted with fluorine gas in the first halogenation treatment process 1. The gas used in the first halogenation treatment process 1 is surplus fluorine gas A11, which is the gas obtained by separating nuclear fuel material B18 from the off-gas of the second halogenation treatment process 2. Note that the surplus fluorine gas A11 is accompanied by oxygen gas A12, which is a reaction product, as an impurity.

The halogenation in the first halogenation process 1 produces silicon fluoride 13, excess fluorine gas B14, oxygen gas B15, and nuclear fuel material A24 as volatile components. These gases are sent to the gas separation process A6, and only the nuclear fuel material A24 is separated.

The equipment used in the gas separation step A6 is specifically a cold trap that condenses and recovers _UF6 . The temperature of the cold trap is a temperature at which only _UF6 condenses without condensing fluorine gas or oxygen gas, and is preferably, for example, about 0°C. The condensed and recovered _UF6 is recycled as nuclear fuel material. The remaining gas from which the nuclear fuel material has been separated is treated and disposed of as secondary waste, but silicon fluoride may be converted into oxide to make _SiO2 and then used as a glass base material in the vitrification step 5.

The temperature for the halogenation treatment in the first halogenation treatment step 1 may be 350° C. or lower at which _UF6 is not produced by fluorination. The reaction in this case is shown in the following formula (5).

In this reaction, solid _{UO2F2 is} produced, and therefore no volatile nuclear fuel material such as the nuclear fuel material A24 is produced, and therefore there is no need to recover the nuclear fuel material A24 from the gas. In this case, the gas separation step A6 can be omitted.

On the other hand, from the viewpoint of improving the reaction rate while suppressing adhesion of fluorinated volatile gases of impurity components to the reaction vessel, the temperature of the halogenation treatment is preferably 100°C or higher.

The fluorination residue A16 is sent to the second halogenation process 2. In the second halogenation process 2, fluorine gas 17 is used. In this process, since it is desired to fluorinate and volatilize the nuclear fuel material B18, the temperature for the halogenation process is desirably 350° C. or higher at which _UF6 is produced by fluorination.

Halogenation in the second halogenation process 2 produces nuclear fuel material B18, excess fluorine gas A11, and oxygen gas A12 as volatile components. These gases are sent to the gas separation process B3, where only the nuclear fuel material B18 is separated.

The device used in the gas separation step B3 is specifically a cold trap that condenses and recovers _UF6 . The temperature of the cold trap is a temperature at which only _UF6 condenses, without condensing fluorine gas or oxygen gas, and is preferably, for example, about 0° C. The condensed and recovered _UF6 is recycled as a nuclear fuel material.

If the temperature in the first halogenation treatment step 1 is 350°C or lower, the reaction in the second halogenation treatment step 2 is as shown in the following formula (6).

The fluoride residue B19 is sent to the oxidation process 4, where it is reacted with steam 20 to convert its chemical form into an oxide. The resulting solid is sent to the vitrification process 5 as waste 21. Here, the waste 21 and glass base material 22 are melted at high temperature, and then cooled and solidified to obtain a vitrified body 23.

The amount of fluorine gas used in this example is explained below.

Table 3 shows the amounts of substances contained in the fuel debris and the amount of fluorine required to completely fluorinate them, based on the fluorination reaction formula.

Assuming that the total amount of fuel debris is 826.6 t, the total amount of substances is roughly calculated to be 9.4 Mmol (9.4 x ¹⁰⁶ mol) by assuming that each substance is a representative compound, as shown in Table 3. Furthermore, when the amount of fluorine required for fluorination is evaluated based on the fluorination reaction formula, the amount of _F2 required to fluorinate the entire amount of fuel debris is 18.9 Mmol. In Example 1, 18.9 Mmol of fluorine gas is supplied in the first halogenation treatment step 1. As fluorine is a strong reactant, in principle it is completely consumed in the fluorination reaction.

In this example, it is conservatively assumed that 90% is consumed in the fluorination reaction. In that case, 10% becomes unreacted fluorine gas (excess fluorine gas B14) as secondary waste (1.9 Mmol).

The results of the fluorine mass balance evaluation at this time are shown in Table 4.

Then, the fluorinated residue A16 is reacted with 18.9 Mmol of fluorine gas in the second halogenation process 2. The fluorinated residue A16 is 90% fluorinated by reacting with the excess fluorine gas A11 in the first halogenation process 1. Therefore, the amount of fluorine required to fluorinate the fluorinated residue A16 is 1.9 Mmol, and in the second halogenation process 2, 10 times the amount of fluorine required for fluorination is supplied. Since a considerable excess of fluorine is supplied for fluorination, the fluorinated residue A16 is completely fluorinated. The excess fluorine gas A11 is reused in the first halogenation process 1, so no secondary waste is generated. The excess fluorine gas A11 is used in the first halogenation process 1 by adding fluorine gas to make up for the shortage.

The results of evaluating the fluorine mass balance in the second halogenation treatment step 2 are shown in Table 5.

For comparison, the amount of secondary waste generated when complete fluorination is achieved in a single halogenation treatment, rather than in two stages as in Example 1, is evaluated and the results are shown in Table 6.

To achieve complete fluorination, it was assumed that 10 times the amount of fluorine required for fluorination (189 Mmol) would be supplied. In this case, the amount of fluorine that would become secondary waste would be 170.1 Mmol.

The above results show that by performing the halogenation process in two stages as in Example 1, the amount of fluorine that becomes secondary waste can be significantly reduced from approximately 170.1 Mmol to 1.9 Mmol.

According to this embodiment, the fuel debris is fluorinated to volatilize and separate the nuclear fuel material, and the remaining fluoride residue is converted to oxide and then vitrified. This ultimately makes it possible to turn the fuel debris into a vitrified body suitable for disposal, and also makes it easier to vitrify, since the composition ratio (ratio of AC oxides to FP oxides) is proven to be effective in vitrification. In addition, by carrying out the fluorination process in multiple stages, the amount of secondary waste generated can be reduced.

The second embodiment of the fuel debris processing method of the present invention will be explained with reference to FIG. 2.

Figure 2 is a flow chart showing a second embodiment of a method for treating fuel debris. In this embodiment, hydrogen fluoride is used as the halogenating agent.

As shown in FIG. 2, the fuel debris processing method of this embodiment includes a first halogenation treatment process 30, a second halogenation treatment process 31, a gas separation process A 32 in the first halogenation treatment process 30, a gas separation process B 33 in the second halogenation treatment process 31, a third halogenation treatment process 34, a gas separation process C 35 in the third halogenation treatment process 34, an oxidation treatment process 36, and a vitrification process 37.

The fuel debris processing method of this embodiment is described in detail below.

In this embodiment, the fuel debris 40 is first fluorinated in the first halogenation treatment process 30. The gas used in the fluorination process is excess hydrogen fluoride gas A41, which is the gas obtained by separating silicon fluoride A48 from the off-gas of the second halogenation treatment process 31. The excess hydrogen fluoride gas A41 is accompanied by water vapor A42, which is a reaction product, as an impurity.

The reaction formula when fluorinating _UO2 with hydrogen fluoride is shown in the following formula (7).

The temperature for halogenation treatment should be 600°C or less, taking into consideration corrosion of the equipment material.

Unlike Example 1, when fluorinating with excess hydrogen fluoride gas A41, uranium becomes non-volatile uranium tetrafluoride even if the reaction temperature is 350°C or higher, so there is no need to set the reaction temperature below 350°C to suppress the fluorination and volatilization of uranium, and the processing temperature can be set to a higher temperature to increase the reaction rate.

As in Example 1, the temperature of the halogenation treatment is preferably 100°C or higher in order to improve the reaction rate while suppressing adhesion of fluorinated volatile gases of impurity components to the reaction vessel.

The halogenation in the first halogenation treatment process 30 produces silicon fluoride B43, excess hydrogen fluoride gas B44, and water vapor B45 as volatile components. These gases are sent to the gas separation process A32.

The gas separation process A32 is a cold trap that condenses and recovers the excess hydrogen fluoride gas B44 and water vapor B45. The temperature of the cold trap is a temperature at which only the excess hydrogen fluoride gas B44 and water vapor B45 condense without condensing silicon fluoride B43, and is preferably, for example, about 0°C. The condensed and recovered excess hydrogen fluoride gas B44 is recycled as a halogenating agent.

In addition, since fluorine gas was used in Example 1, silicon fluoride (sublimation point: -95.7°C) coexists with fluorine gas (boiling point: -188°C), and the evaporation temperature is low, making it difficult to separate using a cold trap.

In Example 2, the halogenation is performed with hydrogen fluoride, and hydrogen fluoride (point: 19.5°C) and silicon fluoride can be easily separated using a cold trap. Therefore, there is an effect that hydrogen fluoride can be recycled without being transferred to secondary waste. Silicon fluoride, which becomes waste, may be converted into oxide to _SiO2 and then used as a glass base material in the vitrification process 37.

Next, in the first halogenation treatment step 30, the almost completely fluorinated fluoride residue A46 is sent to the second halogenation treatment step 31, where it is reacted with hydrogen fluoride gas 47 to be completely fluorinated. The halogenation in the second halogenation treatment step 31 generates silicon fluoride A48, excess hydrogen fluoride gas A41, and water vapor A42 as volatile components. These gases are sent to the gas separation step B33, where silicon fluoride A48 is separated. The hydrogen fluoride recovered by condensation is recycled as a halogenating agent.

The fluorination residue B49 from the second halogenation process 31 is sent to the third halogenation process 34. Here, the uranium in the fluorination residue is fluorinated to uranium hexafluoride by reacting with fluorine gas 50, which is then volatilized. The generated gas is sent to the gas separation process C35, where the nuclear fuel material C51 and excess fluorine gas 52 are separated using the cold trap described in Example 1. The separated fluorine gas (excess fluorine gas 52) is recycled as a halogenation agent. The fluorination residue C53 is sent to the oxidation process 36.

As in Example 1, in the oxidation treatment process 36, the fluoride residue C53 is reacted with steam 54 to convert the chemical form to an oxide. The resulting solid is sent to the vitrification process 37 as waste 55. Here, the waste 55 and glass base material 56 are melted at high temperature, and then cooled and solidified to finally obtain a vitrified body 57.

This embodiment not only provides the same effects as in Example 1, but also has the effect of making it easier to separate the halogenating agent from silicon fluoride during the process by using hydrogen fluoride as the halogenating agent, and the effect of promoting the reaction by increasing the reaction temperature in the halogenation step using hydrogen fluoride.

The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

1, 30...First halogenation treatment process, 2, 31...Second halogenation treatment process, 3, 33...Gas separation process B in the second halogenation treatment process, 4, 36...Oxidation treatment process, 5, 37...Vitrification process, 6, 32...Gas separation process A in the first halogenation treatment process, 10, 40...Fuel debris, 11...Excess fluorine gas A, 12...Oxygen gas A, 13...Silicon fluoride, 14...Excess fluorine gas B, 15...Oxygen gas B, 16, 46...Fluorination residue A, 17, 50...Fluorine gas, 18...Nuclear fuel material B, 1 9, 49...fluoridation residue B, 20, 54...steam, 21, 55...waste, 22, 56...glass base material, 23, 57...vitrified body, 24...nuclear fuel material A, 34...third halogenation process, 35...gas separation process C in the third halogenation process, 41...surplus hydrogen fluoride gas A, 42...steam A, 43...silicon fluoride B, 44...surplus hydrogen fluoride gas B, 45...steam B, 47...hydrogen fluoride gas, 48...silicon fluoride A, 51...nuclear fuel material C, 52...surplus fluorine gas, 53...fluoridation residue C.

Claims (8)

A method for treating fuel debris by vitrifying the fuel debris, comprising the steps of:
The fuel debris is fluorinated in a halogenation treatment step to volatilize the nuclear fuel material, and the remaining fluoride residue is converted into an oxide. The oxide is then mixed with a glass base material to produce a vitrified body,
The halogenation treatment step is carried out in multiple stages,
The fuel debris is reacted with excess fluorine gas in a first halogenation treatment step, and silicon fluoride, excess fluorine gas B, oxygen gas B, and nuclear fuel material A are generated as volatile components by the halogenation in the first halogenation treatment step, and these are sent to a gas separation step A to separate only the nuclear fuel material A,
On the other hand, the fluorinated residue A fluorinated in the first halogenation treatment step is sent to a second halogenation treatment step, in which it is reacted with fluorine gas, and the fluorinated residue A is halogenated in the second halogenation treatment step to generate nuclear fuel material B, excess fluorine gas A and oxygen gas A as volatile components, which are sent to a gas separation step B to separate only the nuclear fuel material B,
The method for treating fuel debris further comprises: sending the fluorination residue B fluorinated in the second halogenation treatment step to an oxidation treatment step, in which the fluorination residue B is reacted with water vapor to convert its chemical form into an oxide, and sending the resulting solid as waste to a vitrification step, in which the waste and a glass base material are melted and then cooled and solidified to obtain a vitrified body . A method for treating fuel debris according to claim 1 , comprising:
4. A method for treating fuel debris, comprising the steps of: (a) providing an off-gas from the second halogenation treatment step and separating the nuclear fuel material from the off-gas; A method for treating fuel debris according to claim 1 or 2 , comprising:
A method for treating fuel debris, characterized in that in the gas separation step A or the gas separation step B, only the nuclear fuel material A or the nuclear fuel material B is separated using a cold trap that condenses and recovers _UF6 . A method for treating fuel debris according to any one of claims 1 to 3 , comprising:
A method for treating fuel debris, wherein the temperature of the halogenation treatment in the first halogenation treatment step is 350°C or lower at which _UF6 is not produced by fluorination, and the temperature of the halogenation treatment in the second halogenation treatment step is 350°C or higher at which _UF6 is produced by fluorination. A method for treating fuel debris by vitrifying the fuel debris, comprising the steps of:
The fuel debris is fluorinated in a halogenation treatment step to volatilize the nuclear fuel material, and the remaining fluoride residue is converted into an oxide. The oxide is then mixed with a glass base material to produce a vitrified body,
The halogenation treatment step is carried out in multiple stages,
The fuel debris is reacted with excess hydrogen fluoride gas A in a first halogenation treatment step, and silicon fluoride B, excess hydrogen fluoride gas B, and water vapor B are generated as volatile components by the halogenation in the first halogenation treatment step, and these are sent to a gas separation step A to separate only the silicon fluoride B,
On the other hand, the fluoride residue A fluorinated in the first halogenation treatment step is sent to a second halogenation treatment step, in which it is reacted with hydrogen fluoride gas, and silicon fluoride A, excess hydrogen fluoride gas A, and water vapor A are generated as volatile components by the halogenation of the fluoride residue A in the second halogenation treatment step, and these are sent to a gas separation step B to separate only the silicon fluoride A,
Furthermore, the fluorinated residue B fluorinated in the second halogenation treatment step is sent to a third halogenation treatment step, in which it is reacted with fluorine gas, and the fluorinated residue B is halogenated in the third halogenation treatment step to generate nuclear fuel material C and excess fluorine gas as volatile components, which are sent to a gas separation step C to separate only the nuclear fuel material C,
The method for treating fuel debris further comprises: sending the fluorination residue C fluorinated in the third halogenation treatment step to an oxidation treatment step, in which the fluorination residue C is reacted with water vapor to convert its chemical form into an oxide, and sending the resulting solid as waste to a vitrification step, in which the waste and a glass base material are melted and then cooled and solidified to obtain a vitrified body. A method for treating fuel debris according to claim 5 , comprising the steps of:
4. A method for treating fuel debris, comprising the steps of: providing an off-gas from the second halogenation treatment step and separating the silicon fluoride A from the off-gas from the second halogenation treatment step; and removing the silicon fluoride A from the off-gas from the second halogenation treatment step. A method for treating fuel debris according to claim 5 or 6 , comprising the steps of:
A method for treating fuel debris, characterized in that in the gas separation process A, only the silicon fluoride B is separated using a cold trap that condenses and recovers hydrogen fluoride and water vapor, and in the gas separation process C, only the nuclear fuel material C is separated using a cold trap that condenses and recovers _UF6 . A method for treating fuel debris according to any one of claims 5 to 7 , comprising the steps of:
2. The method for treating fuel debris, wherein the halogenation treatment temperature in the first halogenation treatment step is 600° C. or lower.

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