Decontamination methods
A gel-like decontamination agent with ultrasonic irradiation addresses the high cost and scattering issues of air blast treatment by effectively separating and containing radioactive materials, enabling cost-effective waste reduction and safe disposal.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TAIHEI DENGYO KAISHA
- Filing Date
- 2024-03-27
- Publication Date
- 2026-07-02
AI Technical Summary
Existing decontamination methods for radioactive wastes, such as air blast treatment, result in high production and maintenance costs due to their complex configurations and pose risks to workers from scattering radioactive substances.
A decontamination method involving the use of a gel-like decontamination agent containing specific gelling agents and optional additives, combined with ultrasonic irradiation, to separate and hold radioactive materials without scattering, using components like locust bean gum, xanthan gum, and cobalt compounds.
The method effectively removes radioactive substances from surfaces, reducing wastes to clearance levels for reuse or disposal, while minimizing scattering and environmental exposure, and reducing costs.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to decontamination treatment.
Background Art
[0002] Wastes generated in nuclear power plants are classified into low-level radioactive wastes (L1, L2, L3), materials that do not need to be treated as radioactive substances (clearance materials), and wastes that are not radioactive wastes (NR) according to the radioactivity level, and need to be disposed of according to the radioactivity level. Among the low-level radioactive wastes, if the L3 wastes with the lowest radioactivity level can be sufficiently decontaminated to become clearance materials, they can be reused and disposed of in the same way as general materials.
[0003] Conventionally, there is air blast treatment as one of the decontamination methods for radioactive wastes. Air blast treatment is a process in which a blasting material is sprayed from a nozzle by compressed air onto radioactive wastes to scrape off the radioactive substances on the surface of the radioactive wastes. However, during the treatment operation, the blasting material and radioactive substances scatter in the air, so the working environment is poor and there are concerns about adverse effects on workers.
[0004] The technology of Patent Document 1 performs blast treatment in a blast box to improve the environment of the decontamination operation and recover the blasting material. Therefore, it has a blast head having a blast nozzle for ejecting the blasting material and a suction hose for sucking the blasting material, and controls the intake of outside air into the blast box as the blasting material is ejected.
Prior Art Documents
Patent Documents
[0005]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0006] However, there are concerns that the device described in Patent Document 1 will have high production and maintenance costs due to its complex configuration.
[0007] Therefore, the object of this invention is to provide a new decontamination method that can remove radioactive materials adhering to the surface of an object to be decontaminated at low cost. [Means for solving the problem]
[0008] This invention was made to achieve the above objective and is characterized by the following:
[0009] The invention described in claim 1 is a method for removing radioactive material adhering to the surface of an object to be decontaminated, comprising: an input step of putting the object to be decontaminated into a container containing a gel-like decontamination agent; and a step of immersing the object to be decontaminated in the gel-like decontamination agent. Super Including an irradiation process that involves irradiating with sound waves. The decontamination agent comprises at least one of locust bean gum, xanthan gum, guar gum, tara gum, carrageenan, gelatin, cellulose derivatives, tremel gum, and konjac powder, and a thioglycolate. It is characterized by [something].
[0012] Claim 2 The invention described in the claim 1 The decontamination method described above, wherein the decontamination agent further comprises a surfactant.
[0013] Claim 3 The invention described in the claim 1 or 2 The decontamination method described above, wherein the decontamination agent further comprises at least one of β-ionone or vanillin.
[0014] Claim 4 The invention described in the claim 1 or 2 The decontamination method described above, characterized in that the decontamination agent further comprises at least one of cobalt oxide, cobalt phosphate, and cobalt aluminate. Claim 5 The invention described in the claim 3The decontamination method described in
[0015] Claim 6 The invention described in A decontamination method for removing radioactive material adhering to the surface of an object to be decontaminated, comprising: an input step of placing the object to be decontaminated into a container containing a gel-like decontamination agent; and an irradiation step of irradiating the object to be decontaminated with ultrasonic waves while the object is immersed in the gel-like decontamination agent, wherein the decontamination agent comprises at least one of locust bean gum, xanthan gum, guar gum, tara gum, carrageenan, gelatin, cellulose derivative, tremel gum, and konjac powder, and at least one of cobalt oxide, cobalt phosphate, and cobalt aluminate. characterized by including
[0017] Claim 7 The invention described in claim Any one of 1, 2, or 6 is a decontamination method described in claim
Effect of the Invention
[0018] According to this invention, since the radioactive substances separated from the decontamination target by ultrasonic waves can be held by the gel-like decontamination agent, the radioactive substances can be removed from the decontamination target without scattering of the radioactive substances like in the blasting process. As a result, for example, L3 waste can be leveled down to clearance waste, and it can be reused or discarded as it is.
Brief Description of the Drawings
[0019] [Figure 1] (A) is a diagram showing a state where ultrasonic waves are irradiated on a decontamination target, and (B) is a diagram showing a state where the radioactive substances separated from the decontamination target are held by a gel-like decontamination agent. [Figure 2] It is a diagram showing a flowchart of the decontamination method according to this embodiment. [Figure 3] It is a diagram showing an example of the components of the decontamination agent used in the experiment of the decontamination method according to this embodiment.
Mode for Carrying Out the Invention
[0020] Embodiments of this invention will be described while referring to the drawings.
[0021] As shown in Figure 1(A), in this embodiment, decontamination of the object to be decontaminated 1, which has radioactive material 2 attached to its surface, is performed by irradiating it with ultrasonic waves 14 using an ultrasonic generator 13 inside a decontamination container 11 (only the bottom of the decontamination container 11 is shown in Figure 1) containing a gel-like decontamination agent 12. As a result, the radioactive material 2 is separated from the object to be decontaminated 1 and held in place by the gel-like decontamination agent 12, thus preventing the separated radioactive material 2 from scattering.
[0022] Herein, the decontamination agent 12 of this embodiment will be described. The decontamination agent 12 includes at least one thickener such as locust bean gum, xanthan gum, guar gum, tara gum, carrageenan, gelatin, cellulose derivatives, tremel gum, or konjac powder for gelling the decontamination agent 12.
[0023] Furthermore, the decontamination agent 12 may further contain borax as a crosslinking agent for various thickeners such as guar gum, tara gum, and konjac powder, or at least one of reducing monosaccharides or oligosaccharides. For example, borax promotes the crosslinking reaction that connects guar gum molecules, thereby increasing the rigidity of the gel-like decontamination agent 12. However, when borax is added to guar gum, the rigidity of the gel-like decontamination agent 12 increases, but its fluidity decreases. Therefore, by further adding reducing monosaccharides or oligosaccharides, both the rigidity and fluidity of the gel-like decontamination agent 12 can be improved.
[0024] Decontamination agent 12 can be manufactured, for example, by adding 0.5 g of guar gum to 50 ml of water, stirring, and allowing it to stand to swell. Then, boric acid solution (10 wt% borax and 13 wt% fructose) is added and stirred.
[0025] The viscosity of the decontamination agent 12 produced in this manner can be adjusted by changing the amount of reducing monosaccharides and oligosaccharides added.
[0026] Furthermore, the decontamination agent 12 may include a mixture of roasted bean gum and xanthan gum as an example of how to make the decontamination agent 12 gel-like. By adjusting the ratio of roasted bean gum to xanthan gum in the range of 2:8 to 7:3, the gel strength can be approximately 150 g / cm². 2 The above can be achieved, and if the ratio is 5 parts roasted bean gum to 5 parts xanthan gum, the gel strength will be approximately 300 g / cm². 2 This can be done. In this way, the gel strength of the decontamination agent 12 can be adjusted by the combination and mixing ratio of various thickeners. The gel strength of the decontamination agent 12 is 150 g / cm³. 2 ~300g / cm 2 It is preferable to do so.
[0027] The amount of the thickening agent should be, for example, 0.5 wt% to 1.5 wt% of the total amount of the decontamination agent 12.
[0028] The decontamination agent 12 can be applied to the surface of the object 1 to be decontaminated, which is contaminated with radioactive material 2, and then removed to decontaminate the object 1. Furthermore, by incorporating the radioactive material 2 into the gel, it is possible to prevent the radioactive material 2 from scattering and contaminating the surrounding area, and disposal is also made easier.
[0029] Next, the ultrasonic generator 13 will be described. A commercially available ultrasonic generator 13 can be used; for example, the plastic welder (SONAC-200) from Honda Electronics Co., Ltd. can be used. The frequency of the ultrasonic waves 14 can be set in the range of 15kHz to 28kHz.
[0030] Next, the decontamination method of this embodiment will be explained using the flowchart in Figure 2.
[0031] First, the object to be decontaminated 1, which has radioactive material 2 attached to its surface, is placed into a decontamination container 11 containing a gel-like decontamination agent 12 (step S11: an example of the "putting process").
[0032] Next, with the object to be decontaminated 1 immersed in the gel-like decontamination agent 12, ultrasonic waves 14 are irradiated onto the object to be decontaminated 1 using an ultrasonic generator 13 (step S12: an example of the "irradiation process").
[0033] As described above, the decontamination method of this embodiment is a decontamination method for removing radioactive material 2 attached to the surface of an object to be decontaminated 1, and includes a step S11 (an example of a "putting step") in which the object to be decontaminated 1 is put into a decontamination container 11 (an example of a "container") containing a gel-like decontamination agent 12, and a step S12 (an example of an "irradiation step") in which ultrasonic waves 14 in the range of 15kHz to 28kHz are irradiated onto the object to be decontaminated 1 while the object to be decontaminated 1 is immersed in the gel-like decontamination agent 12.
[0034] Therefore, according to the decontamination method of this embodiment, the radioactive material 2 separated from the object to be decontaminated 1 by ultrasonic waves 14 can be held in place by the gel-like decontamination agent 12, so that the radioactive material 2 can be removed from the object to be decontaminated 1 without scattering, as in blast treatment. As a result, for example, L3 waste can be reduced to a clearance level, which can then be reused or disposed of as is.
[0035] Furthermore, if the radioactive material 2 is hydrophilic, it can be directly absorbed by the gel-like decontamination agent 12 without irradiation with ultrasonic waves 14. However, if the radioactive material 2 is hydrophobic (such as oil), as in the decontamination method of this embodiment, the radioactive material 2 is lifted away from the object to be decontaminated 1 by irradiation with ultrasonic waves 14, making it easier for the gel-like decontamination agent 12 to absorb it.
[0036] Furthermore, if the radioactive material 2 is rusted on the surface of the object to be decontaminated 1, or if the surface of the object to be decontaminated 1 is radioactive, a thioglycolate such as ammonium thioglycolate or sodium thioglycolate may be added to the gel-like decontamination agent 12. The amount of thioglycolate added should be, for example, 0.3 mol / L to 1 mol / L relative to the total amount of decontamination agent 12. The thioglycolate reduces the radioactive material 2 and radioactive materials attached to the object to be decontaminated 1, making them easier to incorporate into the gel-like decontamination agent 12.
[0037] In addition, a surfactant (for example, an amphoteric surfactant such as sodium cocoamphoacetate (Softazolin® CH-R), cocamidopropyl betaine (Softazolin® CPB-R), or lauramidopropyl betaine) may be added to the decontamination agent 12 along with the thioglycolate. The amount of surfactant added should be, for example, 0.02 wt% to 0.05 wt% of the total amount of the decontamination agent 12.
[0038] Furthermore, since thioglycolate salts exhibit a malodorous and pungent odor, it is preferable to further add at least one of β-ionone or vanillin to mitigate or eliminate this odor. When adding only β-ionone, the amount added should be, for example, 0.08 wt% to 0.2 wt% of the total decontamination agent 12. When adding only vanillin, the amount added should be, for example, 0.08 wt% to 0.2 wt% of the total decontamination agent 12. When adding both β-ionone and vanillin, the amount added should be, for example, 0.08 wt% to 0.2 wt% of the total decontamination agent 12.
[0039] Furthermore, since the decontamination agent 12 contains a thickener that promotes mold growth, at least one of cobalt oxide, cobalt phosphate, and cobalt aluminate may be added to the decontamination agent 12 for the purpose of preventing mold growth. When only cobalt oxide is added, the amount added should be, for example, 0.05 wt% to 0.2 wt% of the total amount of the decontamination agent 12. When only cobalt phosphate is added, the amount added should be, for example, 0.05 wt% to 0.2 wt% of the total amount of the decontamination agent 12. When only cobalt aluminate is added, the amount added should be, for example, 0.05 wt% to 0.2 wt% of the total amount of the decontamination agent 12. This improves the mold resistance of the decontamination agent 12.
[0040] Furthermore, if the radioactive material 2 attached to the object to be decontaminated 1 contains cobalt 60, it may not be completely incorporated into the decontamination agent 12 and may remain on the surface of the object to be decontaminated 1. In this case, by adding a cobalt compound with a structure similar to cobalt 60 to the decontamination agent 12, the cobalt compound acts as a retaining carrier, allowing the cobalt 60 to be incorporated into the decontamination agent 12. In other words, by adding at least one of cobalt oxide, cobalt phosphate, and cobalt aluminate, these will act as antifungal agents and retaining carriers.
[0041] Next, an example of the decontamination agent 12 used in the experiment of the decontamination method of this embodiment, shown in Figure 3, will be described. The decontamination agent 12 in the experimental example is a mixture of a thickener, a decontamination liquid, and an antifungal agent (retaining carrier).
[0042] The thickening agent consists of a solution of 2g of locust bean gum dissolved in 200g of water and a solution of 1.65g of xanthan gum dissolved in 125g of water.
[0043] The decontamination solution consists of 49.2 g of a 55% aqueous solution of ammonium thioglycolate, 41.0 g of water, 0.4 g of a 30% aqueous solution of softazoline CPB-R, and 0.4 g of β-ionone.
[0044] The total mass of the mixture of these thickeners and decontamination solution is 419.65 g. The mass percentage concentration (%) of each component is as follows: Locust bean gum: 0.48% Xanthan gum: 0.39% Ammonium thioglycolate: 6.4% Softazoline CPB-R: 0.03% β-ionone: 0.10% When adding other thioglycolate salts such as sodium thioglycolate instead of ammonium thioglycolate, it is preferable to add an amount of thioglycolate salt that results in a molar concentration of 0.6 mol / L.
[0045] Decontamination agent 12 is prepared by adding 0.10 wt% or less of cobalt oxide as an antifungal agent (retaining carrier) to a mixture of these thickeners and the decontamination solution.
[0046] As described above, the decontamination agent 12 may consist of at least one of the following as a thickener: locust bean gum, xanthan gum, guar gum, tara gum, carrageenan, gelatin, cellulose derivative, tremel gum, and konjac powder; a thioglycolate; a surfactant; at least one of β-ionone or vanillin as a deodorant; and at least one of the following as an antifungal agent (retaining carrier): cobalt oxide, cobalt phosphate, and cobalt aluminate. Here, let the thickener be "A", the thioglycolate be "B", the surfactant be "C", the deodorant be "D", and the antifungal agent (retaining carrier) be "E". An example of a combination of components for the decontamination agent 12 is shown below. However, the combination of components for the decontamination agent 12 is not limited to these, and any combination that is significant as a decontamination agent 12 can be adopted. • "A only" · "A + B" · "A+B+C" · "A+B+D" • "A+B+C+D" • "A+E" · "A+B+E" • "A+B+C+E" • "A+B+D+E" · "A+B+C+D+E" [Explanation of symbols]
[0047] 1: Objects to be decontaminated 2:Radioactive material 11: Decontamination containers 12: Decontamination agent 13: Ultrasonic generator 14: Ultrasound
Claims
1. A decontamination method for removing radioactive materials attached to the surface of an object to be decontaminated, A step of adding the object to be decontaminated to a container containing a gel-like decontamination agent, The process includes an irradiation step in which ultrasonic waves are irradiated onto the object to be decontaminated while the object to be decontaminated is immersed in the gel-like decontamination agent, Includes, The aforementioned decontamination agent is At least one of locust bean gum, xanthan gum, guar gum, tara gum, carrageenan, gelatin, cellulose derivative, tremel gum, and konjac powder, Thioglycolate and A decontamination method characterized by including [a certain component].
2. A decontamination method according to claim 1, The decontamination method is characterized by further comprising a surfactant as the decontamination agent.
3. A decontamination method according to claim 1 or 2, A decontamination method characterized in that the decontamination agent further comprises at least one of β-ionone or vanillin.
4. A decontamination method according to claim 1 or 2, A decontamination method characterized in that the decontamination agent further comprises at least one of cobalt oxide, cobalt phosphate, and cobalt aluminate.
5. A decontamination method according to claim 3, A decontamination method characterized in that the decontamination agent further comprises at least one of cobalt oxide, cobalt phosphate, and cobalt aluminate.
6. A decontamination method for removing radioactive material adhering to the surface of an object to be decontaminated, A step of adding the object to be decontaminated to a container containing a gel-like decontamination agent, The process includes an irradiation step in which ultrasonic waves are irradiated onto the object to be decontaminated while the object to be decontaminated is immersed in the gel-like decontamination agent, Includes, The aforementioned decontamination agent is At least one of locust bean gum, xanthan gum, guar gum, tara gum, carrageenan, gelatin, cellulose derivative, tremel gum, and konjac powder, At least one of cobalt oxide, cobalt phosphate, and cobalt aluminate, A decontamination method characterized by including [a certain component].
7. A decontamination method according to any one of claims 1, 2, or 6, The decontamination method is characterized in that the decontamination agent further contains borax.