Pollutant removal methods

Abstract

Provided is a method for removing contaminants that removes contaminants without damaging a substrate and without volatilizing the contaminants. [Solution] A water-soluble resin solution is coated on a contaminated surface, dried, and a square flat-top shaped nano-pulse laser beam is irradiated onto the dried film 36 containing the contaminants, peeling off and removing the contaminants together with the water-soluble resin coating film 36 from the substrate surface without heating and volatilizing them. The water-soluble resin is preferably polyvinyl alcohol. The resin film, attached contaminants, and substrate surface can be decontaminated at 75°C or less.

Description

[Technical field]

[0001] The present invention relates to a method for removing pollutants using a water-soluble resin coating film. [Background technology]

[0002] Radioactive contaminants such as radioactive cesium oxide, chloride, radioactive strontium oxide, and chloride, as well as chemical contaminants such as polychlorinated biphenyls (PCBs) and dioxins, that adhere to structures are generally harmful to humans and living organisms on Earth, and must be safely removed and collected from the surfaces of structures. As the removal means, a method of irradiating the surface of a structure to which contaminants are attached with energy-controlled laser light to remove the contaminants has been proposed. Patent Document 1 proposes irradiating radioactive contaminants present on the surface of a metal substrate with CW laser light and pulsed laser light to melt and evaporate or volatilize the radioactive contaminants together with the surface layer of the metal substrate to remove them. In this case, the high heat caused by the laser irradiation causes all the radioactive contaminants to become dust (particle size 1 to 150 μm) or fumes (particle size 0.2 to 1 μm) and scatter. Therefore, a large number of filters must be used to capture a large amount of scattered fine particles, which results in a large amount of contaminated waste. Patent Document 2 proposes irradiating the contaminated target material with a time-shortened pulse laser characterized by a pulse width in picoseconds or femtoseconds to the contaminants in the irradiation area for a sufficiently short time in picoseconds or femtoseconds without affecting the surrounding molecules with heat generated by the energy transfer of the laser light, thereby evaporating or removing the contaminants at the molecular level. In this case, particles smaller than fumes (particle size 0.2 to 1 μm), that is, ultrafine particles of molecular or atomic size, are dispersed into the air, making collection more difficult than the fine dust particles generated in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-016530 A [Patent Document 2] JP 2007-315995 A Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned conventional techniques are based on the technical idea of ​​applying the high or ultra-high temperature energy of laser light to the contaminant for a very short time to avoid thermal effects on the surroundings of the contaminant as much as possible, and melting, evaporating, or vaporizing only the contaminant. Therefore, it is very difficult for any of these methods to collect particles with a diameter smaller than the fume (0.2 to 1 μm) that is removed and scattered. For example, if radioactive contaminants or PCBs contained in organic matter such as oils and fats that vaporize and burn at several hundred degrees are removed from the surface of a substrate using the above-mentioned conventional techniques, the contaminants will be burned or vaporized or vaporized by the high heat, and the contaminants will simply be diffused into the air, which means that the contaminants are not essentially removed, and there is also the problem that the substrate will be damaged.

[0005] In order to solve the problems of the prior art, the present invention provides a method for removing contaminants that does not damage the substrate and does not burn or volatilize the contaminants due to the high temperatures generated when the contaminants are irradiated with laser light. [Means for solving the problem]

[0006] One embodiment of the present invention is a method for removing contaminants by irradiating a contaminated surface with nano-pulse laser light oscillated from a pulse oscillator, the method comprising: coating the contaminated surface with a water-soluble resin solution, drying the coating, The present invention relates to a method for removing contaminants, which comprises irradiating a dried film containing contaminants with nano-pulse laser light having a rectangular flat top shape, and peeling off the contaminants together with the water-soluble resin coating film from the substrate surface without heating and volatilizing them. Effect of the Invention

[0007] In the present invention, a water-soluble resin solution is coated on a contaminated surface, the contaminants are encapsulated in the gaps between the resin polymer particles, then the contaminated surface is irradiated with a square flat-top shaped nano-pulse laser beam from the surface of the dried film, the contaminants are removed from the substrate surface together with the dried film by applying energy for an ablation effect against the van der Waals force, which is the adhesion energy of the dried film, and the vibrating peeling is performed, thereby efficiently peeling and removing the dried film encapsulating the contaminants at a low temperature without damaging the substrate and without burning or volatilizing it. This allows the contaminants to be removed in the form of a film, making it possible to collect and remove them without using a high-performance filter as in conventional technology. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic explanatory diagram of a nano-pulse laser oscillator according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic explanatory diagram of a nanopulse laser irradiation device according to one embodiment of the present invention. [Diagram 3] FIG. 3 shows a schematic waveform diagram (left) of a conventional Gaussian-shaped nano-pulse laser beam, and a schematic waveform diagram (right) of a square flat-top shaped nano-pulse laser beam according to one embodiment of the present invention. [Figure 4] FIG. 4A is a schematic top view showing an irradiation state with a square flat-top beam shape according to one embodiment of the present invention, and FIG. 4B is a schematic side cross-sectional view of the same. [Diagram 5] FIG. 5A is a schematic top view showing an irradiation state with a conventional Gaussian beam shape, and FIG. 5B is a schematic side cross-sectional view of the same. [Figure 6] FIG. 6A is a schematic energy distribution diagram of laser light having a flat-top beam shape, and FIG. 6B is a schematic energy distribution diagram of laser light having a Gaussian beam shape. [Figure 7] FIG. 7 is a schematic cross-sectional view of an embodiment of the present invention in which sodium hydrogen carbonate is added to an aqueous polyvinyl alcohol resin solution and then coated. [Figure 8] FIG. 8 is a schematic cross-sectional view of the resin coating after drying. [Figure 9] FIG. 9 is a schematic perspective view of one embodiment of the present invention during irradiation with nanopulse laser light. [Figure 10] FIG. 10 is a schematic perspective view of an embodiment of the present invention with the resin coating peeled off. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The method for removing contaminants according to one embodiment of the present invention includes the following steps. (1) Water-soluble resin solution coating process In this process, a water-soluble resin solution adjusted to the chemical characteristics of the contaminants that have already adhered to the substrate surface is applied using an airless spray, brush, roll coater, etc. For example, if the adhering substances are radioactive Cs chloride, radioactive Sr chloride, or oils and fats, an alkaline water-soluble resin coating material is used, and the contaminants are quickly ionized in water by the OH groups in the water and dispersed in the water-soluble resin fine particle polymer. For metal oxides, etc., a water-soluble resin coating material containing an organic acid, inorganic acid, etc. is used, and the metal molecules are ionized and dispersed as solid oxide or chloride fine particles between the fine particle polymer when the water-soluble resin dries. It is preferable to add an alkaline substance such as sodium bicarbonate or an acidic substance such as ascorbic acid to the water-soluble resin solution. The amount of addition is preferably 1 to 20 parts by mass per 100 parts by mass of the water-soluble resin solution. This makes it possible to dissolve the contaminants in the water and disperse the contaminants in the aqueous resin as fine particles when the water evaporates. The coating amount is preferably such that the thickness of the coating after water evaporation and drying is 0.1 mm to 2 mm in a dry state, more preferably 0.1 to 1.5 mm, and even more preferably 0.1 to 1 mm. (2) Drying process Drying is preferably natural drying or drying with low-temperature hot air dehumidification at about 20 to 40°C. The low-temperature hot air dehumidification effect allows the moisture in the coating film to be evaporated and dried slowly from the lower surface to the upper surface at low temperature, so that the moisture present between the resin polymer particles can be sufficiently evaporated and removed, and a film can be formed without volatilizing contaminants with low evaporation temperatures. Drying with high-temperature air is not preferable because it causes the problem that a dry film is formed quickly on the coating film surface, leaving moisture in the film. In this way, a dry film of the water-soluble resin coating containing the fixed contaminants on the substrate surface is formed. (3) Nanopulse laser light irradiation process This process will be explained in detail later. The important point is that by irradiating the square flat-top shape of the present invention with a laser beam having a nano-pulse width of 20 nm to 100 nm at an appropriate repetition frequency (kHz) and scanning speed, the dried coating film is peeled off from the substrate surface by the ablation effect of the nano-pulse laser without thermal damage. Therefore, the dried coating film can be easily peeled off from the metal substrate surface later. (4) Coating film removal process By irradiating the nano-pulse laser light under the above conditions, a very high vibration phenomenon occurs between the coating film and the metal substrate surface due to the ablation effect, and a very small gap is created at the interface between the coating film and the metal substrate, which can be peeled off more easily by air blowing in some cases. At this time, the dried coating film is not destroyed by the wind pressure of the air blow, so the coating film can be peeled off in a film state without the contaminants diffusing, and the contaminants can be safely disposed of.

[0010] The water-soluble resin may be any water-soluble resin so long as it is water-soluble, and examples thereof include polyvinyl alcohol, polyvinyl acetal, polyvinyl acetate, polyvinyl pyrrolidone, polyethylene oxide, phenolic hydroxyl group-containing resins, carboxyl group-containing resins, etc. Among these, polyvinyl alcohol is preferred from the standpoints of handling, safety, cost, etc.

[0011] The polyvinyl alcohol water-soluble resin solution is preferably prepared by dissolving 100 parts by mass of polyvinyl alcohol resin in 1000 to 10,000 parts by mass of water. Water is a safe solvent and is easy to handle. In addition, the adhesion energy of the dried coating film using polyvinyl alcohol resin to the metal substrate surface due to van der Waals force is extremely low, and the magnitude of van der Waals force is usually about 2 kJ to 4 kJ / mol.

[0012] Next, the nanopulse laser light irradiation step will be described. The surface contaminant removal device used in the present invention includes a means for converting a Gaussian-shaped nano-pulse laser beam emitted from a pulse oscillator into a square flat-top shaped nano-pulse laser beam using a flat beam shaver, and a means for irradiating the contaminated surface with the square flat-top shaped nano-pulse laser beam. This allows efficient removal of contaminants without damaging the substrate and without volatilizing them. Damage to the substrate can compromise safety in nuclear power-related equipment, and volatilizing contaminants into the atmosphere can cause damage to the surrounding area, both of which are important issues. The contaminants are removed at low temperatures by irradiating the contaminated surface with nano-pulse laser light emitted from a pulse oscillator capable of emitting highly accurate pulse laser light with little dispersion when passing through a lens with a single wavelength laser light, utilizing the ablation effect, which is the vibration effect of the nano-pulse laser light. In other words, the dried coating containing the contaminants is given energy greater than the van der Waals force, which is the binding energy between the contaminated surface and the dried coating, mainly through the ablation effect of the nano-laser light, and the contaminants are peeled off from the substrate surface in the form of a film, removing the contaminants from the substrate surface without scattering them in the form of fine particles. In the present invention, the term "without heating to volatilize" refers to decontaminating the resin film, adhering contaminants, and substrate surface at 75°C or lower.

[0013] Typically, the square flat-top nano-pulse laser light irradiated to the contaminated surface has an energy density per unit area of ​​1 J / cm 2More preferably, it is 1 to 10 J / cm 2 and more preferably 5 to 10 J / cm 2 and more preferably 7 to 10 J / cm 2 However, the van der Waals force of the contaminated surface, which is a polyvinyl alcohol resin film that is the adhesion energy of the interface between the metal substrate surface and the dried coating film, which is a dried coating film that dissolves or encapsulates contaminants, is 1 J / cm for a thickness of 0.2 mm. 2 By irradiating a nano-pulse laser beam having an energy density of at least 100 J, the substrate is not damaged and the contaminants can be efficiently removed by the ablation effect without volatilizing them. To achieve the above energy density, it is preferable to adjust the maximum output (kW), pulse width, repetition frequency, laser beam scanning speed, and focal diameter of the square flat-top shape of the pulse beam in combination. Polyvinyl alcohol has a mass of 44.05 g / mol, and the van der Waals force of a 0.2 mm thick polyvinyl alcohol is approximately 1 J / cm 2 Heat resistance is over 300℃, and there is no heat damage.

[0014] The focal diameter of the nano-pulse laser light of the square flat-top shape irradiated to the contaminated surface is preferably adjustable from 1 mm to 1.8 mm, which allows the focal diameter of the laser light to be small, the energy density (J) to be high, and a deep focal depth (several cm to several tens of cm), which is a characteristic of the square flat-top laser light, to be obtained, and since there are fewer gaps during laser light scanning than with a round flat-top laser, uniform energy application to the unevenness of the irradiated surface is possible at a high scanning speed.

[0015] The pollutant removal device preferably includes a pulsed Nd:YAG laser oscillator that oscillates light of a single wavelength controlled to a wavelength of 1064 nm or more and 1070 nm or less. Since the occurrence of splitting in a nano-pulse laser with a pulse width in the nanosecond range prevents uniform energy deposition on the irradiated surface, it is preferable to employ a MOPA type pulsed Nd:YAG laser oscillator that oscillates light of a single wavelength with extremely high accuracy controlled to a wavelength between 1064 nm and 1070 nm.

[0016] The pulse width of the pulse oscillator is preferably 20 ns to 500 ns, which makes it possible to increase the energy density (J) of the flat-top focusing surface of a relatively low-output nano-pulse laser with an average output of 500 W when the focused shape of the pulsed light is a square flat-top. The frequency of the pulse oscillator is preferably 10 kHz or more and 50 kHz or less, so that when the focused shape of the pulsed light is a square flat top, it is possible to impart energy to the irradiation surface without gaps even if the scanning speed of the laser light is increased.

[0017] The nano-pulse laser light oscillated by the pulse oscillator preferably has a minimum average output of 500 W or more and a maximum output of 2.5 Mw or more, which makes it possible to increase the energy density (J) of the focusing surface when the focused shape of the pulse light is a square flat top. Incidentally, the energy density per pulse of a pulsed laser can be calculated by the average output (W) divided by the oscillation repetition frequency. Also, the maximum output can be calculated by the energy density per pulse divided by the pulse width.

[0018] It is preferable to include a means for transmitting the nano-pulse laser light generated by the pulse oscillator to the irradiation device via a fiber cable having a length of 10 m to 150 m. This makes it possible to place the oscillator at a safe location in a wide area such as a large structure, and to mount only the irradiation device on a remote-controlled robot or the like for movement.

[0019] The nano-pulse laser light oscillated by the pulse oscillator decontaminates the resin film, the adhering contaminants, and the substrate surface at preferably 75° C. or less, more preferably 65° C. or less, and even more preferably 55° C. or less. This allows the substrate to be removed without being damaged and the contaminants to be removed without being burned or volatilized.

[0020] The contaminant removal method of the present invention is suitable for removing contaminants that are compatible with water-soluble resin coating materials, such as contaminants including fine particles of sea salt containing radioactive contaminants Cs, Sr and / or chloride components including Na, Ca, etc., and / or oils and fats, fine particle metal oxides, inorganic substances, etc.

[0021] Next, the description will be given with reference to the drawings. In the following, the same reference numerals in the drawings indicate the same objects. FIG. 1 is a schematic diagram of a nano-pulse laser oscillator 1 according to an embodiment of the present invention. The nano-pulse laser oscillator 1 generates pulses using a pulse generator 2. The pulse generator preferably uses a Nd:YAG fiber laser. This is an infrared laser with a single wavelength of 1067 nm, and when the average output is set to 500 w or more, the fiber cable can be extended up to 150 m in the case of 2 kW. Therefore, in a wide area such as a large structure, the oscillator is placed at a safe location, and only the irradiation device is mounted on a remote-controlled robot or the like, and can be moved. The pulse oscillator 1 is preferably a MOPA type pulse oscillator capable of oscillating pulse light with a pulse width of nanoseconds at a stable maximum output and frequency. It is necessary to irradiate the adhesion interface between the surface contaminant and the metal surface with light of a single wavelength with high precision and little scattering. Conventionally, CW lasers with a large wavelength tolerance of 1070 nm ±50 nm have been used, but with nanopulse lasers, whose pulse width is in the nanosecond range, the occurrence of spectroscopic phenomena prevents uniform energy deposition on the irradiated surface. Therefore, it is preferable to employ a MOPA-type pulse oscillator of an Nd:YAG laser that emits light of a single wavelength with extremely high precision, controlled at a wavelength between 1064 nm and 1070 nm. The pulse generated by the pulse generator 2 is converted by the seed LD 3 into picosecond to subnanosecond pulse laser light.

[0022] Next, the isolator 4 in the preamplifier 8 prevents signal leakage, protects the equipment, and reduces the effects of noise. The semiconductor laser excitation light is input from the excitation LD 6 to the rare earth doped fiber cable 7 via the coupler 5 . Next, the isolator 9 in the main amplifier 13 prevents signal leakage, protects the equipment, and reduces the effects of noise, and the bandpass filter 10 extracts physical phenomena in a specific frequency band. The semiconductor laser excitation light is then input from the excitation LD 11 to the rare-earth doped fiber cable 7 via the coupler 12. The fiber cable 7 is connected to the nano-pulse laser irradiation device 20.

[0023] 2 is a schematic diagram of a nano-pulse laser irradiation device 20 according to one embodiment of the present invention. First, the laser light is collimated by a collimator 14. Next, a Gaussian-shaped beam, which is a typical pulsed laser beam shape, is converted by a flat-beam shaver 15 into a flat-top beam shape when it reaches the irradiation surface. Next, the nano-pulse laser light passes through optical system focus adjusters 16a and 16b, a scan head 17, and a laser profiler 18, and is irradiated onto an irradiation target (contaminated surface) 19 with a square flat-top shape.

[0024] FIG. 3 is a schematic waveform diagram (left) of a nano-pulse laser beam of a Gaussian-shaped beam 21 according to an embodiment of the present invention, and a schematic waveform diagram (right) of a nano-pulse laser beam of a square flat-top-shaped beam 25. By flattening the laser beam shape into a trapezoidal shape like the square flat-top-shaped beam 25, the thermal effect on the irradiated surface is reduced, and only the ablation effect, which is the vibration abrasion effect, can be utilized, reducing melting of contaminants. However, in this case, the excess energy part of a general pulse laser beam is flattened to an irradiation intensity up to a line where the irradiation intensity reaches a part slightly above the ablation threshold 28, so the irradiation intensity area at the ablation threshold 28 is expanded. However, as described above, in order to achieve a separation speed that satisfies the cleaning speed of a metal structure for contaminants attached to the surface of a metal substrate, it is necessary to set the irradiation intensity line at the ablation threshold to several J / cm, which is the irradiation intensity line that destroys the van der Waals force, which is the adhesion energy, at an appropriate range and speed. 2 It is necessary to raise the line, and for that purpose, it is preferable to use an irradiation device having an optical system that stably outputs pulsed light of Nd:YAG fiber laser light (wavelength 1064 nm) with an average output of 500W or more, a maximum output of 1.25Mw or more, a pulse width of 10ns to 500ns, and a pulse shape of the pulsed light in a square flat-top shape. In FIG. 3, 22 is the excess energy of the Gaussian-shaped beam 21, 23 is the irradiation diameter, and 24 is the thermal energy. Also, 26 is the irradiation diameter of the square flat-top shaped beam 25, and 26 is the thermal energy of the skirt. The width of the Gaussian-shaped beam 21 is extremely narrow compared to the width of the thermal energy 24.

[0025] Fig. 4A is a schematic top view showing the irradiation state with the square flat-top beam shape of one embodiment of the present invention, and Fig. 4B is a schematic side cross-sectional view of the same. Fig. 5A is a schematic top view showing the irradiation state with a conventional Gaussian beam shape, and Fig. 5B is a schematic side cross-sectional view of the same. In Figs. 4A-B and 5A-B, it is assumed that red rust (Fe2O3) has occurred in which a polyvinyl alcohol film containing contaminants is attached to the surface of a steel material, and that the red rust layer is about 500 μm thick. In order to remove this red rust, the adhesion energy of the boundary between the steel material surface to which the contaminants are attached and the contaminants themselves is the van der Waals force, and its magnitude is 1 cm 2 Since the energy density is 2~4 kJ / mol per mole, it is estimated that the atoms are fixed at the following energy density: A Adhesion energy (J / cm 2 ) Calculation example 1. Red rust (Fe2O3) (1) Calculate the molecular weight per mole of attached red rust: 160 g / mol (2) Thickness of attached red rust: 500 μm (3) Adhesion surface area: 1 cm 2 Weight of rust per unit: 5.24g / cm 2 (Density of Fe2O3) x 1 / 20 = 0.262g (4) 1 cm 2 Number of moles of red rust per mole: 0.262g ÷ 160g / mol = 0.0016375mol (5) Van der Waals bond strength of 0.0016375 mol of red rust: 3.275 J / cm 2 ~6.55J / cm 2 From the above, it takes 1 cm to remove red rust with a thickness of 500 μm. 2 7J / cm per 2It is theoretically believed that contaminants can be dissociated by irradiating a pulsed laser beam with a certain energy density. However, in reality, the boundary surface between the surface where red rust has formed and the steel material is not flat, but has irregularities caused by corrosion, increasing the boundary surface area. Also, the distance from the laser beam emitting lens to the boundary surface changes slightly due to the irregularities from the boundary surface. In addition, the thickness of the actual red rust layer is not constant. For this reason, the following points must be kept in mind when removing red rust from steel materials by irradiating it with a pulsed laser beam. (1) The pulsed light is 1cm 2 7J / cm per 2 It is preferable to use one having an energy density corresponding to To meet this requirement, the threshold pulsed light intensity is 7 J / cm 2 It is advantageous to irradiate with a flat-top beam having a shape such that the flat-top beam has ... (2) It is preferable that the irradiation pitch is appropriate under the condition (1) above. The appropriate irradiation pitch is determined by the combination of the scanning speed and repetition frequency of the laser light. In the irradiation condition settings on the left side of Figure 4, the scanning speed and repetition frequency settings are well-balanced, so there are no gaps on the irradiated surface, making it possible to remove contaminants reliably. However, if the scanning speed is too fast compared to the repetition frequency conditions, as in the right side of Figure 4, gaps will appear on the irradiated surface, and these will remain unremoved.

[0026] Figure 6A is a schematic energy distribution diagram of a laser beam with a flat-top beam shape, and Figure 6B is a schematic energy distribution diagram of a laser beam with a Gaussian beam shape. Compared to the Gaussian beam shown in Figure 6A, the optimum energy density of the flat-top beam shown in Figure 6B can be set in a wider optimum energy density zone in both the focal length direction and focal diameter. Within this optimum zone, the energy required for separation can be appropriately applied. Also, within the optimum zone, energy is not applied that is greater than the energy required to destroy the van der Waals forces, so the steel part will not be destroyed. From the above, in order to reliably remove contaminants such as radioactive contaminants from the surface of a metal structure or the like without damaging the substrate, it is possible to provide an energy density that resists van der Waals forces by irradiating the interface between the contaminant and the substrate with a flat-top beam-shaped nano-pulse laser light at an appropriate repetition frequency, scanning speed and focal diameter.

[0027] Fig. 7 is a schematic cross-sectional view of an embodiment of the present invention, in which sodium bicarbonate is added to an aqueous polyvinyl alcohol resin solution and the solution is coated. Chloride particles 31 of Cs, Sr, Na, etc., oil molecules 32 of PCB contaminants, etc., and water-insoluble particulate deposits 33 are attached to the surface of a SUS substrate 30. A coating film 34 in a wet state contains dissolved polyvinyl alcohol resin 35 and sodium ions (Na + ), hydroxide ion (OH - ), carbonate ion (CO3 2- ) etc. exist. Figure 8 is a schematic cross-sectional view of the resin coating after drying. Between the SUS substrate 30 and the polyvinyl alcohol resin coating 36, there is a weak adhesive surface 40 due to van der Waals forces. Within the polyvinyl alcohol resin coating 36, there are particles 38 that have been atomized and captured within the polyvinyl alcohol resin coating, as well as sodium bicarbonate (NaHCO3) particles 37. Arrows 39 indicate low-temperature evaporation of water.

[0028] 9 is a schematic perspective view of an embodiment of the present invention during irradiation with nano-pulse laser light. A polyvinyl alcohol resin film 36 coated on the surface of a SUS substrate 30 is irradiated with nano-pulse laser light 42 from a laser irradiation device 41.

[0029] 10 is a schematic perspective view of an embodiment of the present invention in a state where the resin coating has been peeled off. When air 44 is blown from an air duster (air knife) 43 between the SUS substrate 30 and the polyvinyl alcohol resin coating 36, the resin coating 36 is peeled off and can be disposed of as it is. EXAMPLES

[0030] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Example 1 (1) Water-soluble resin Polyvinyl alcohol was used as the water-soluble resin. Polyvinyl alcohol is soluble in water, has a melting point of 200°C, and a density of 1.19 g / cm 3 and boiling point: 340° C. The polyvinyl alcohol (10% by mass), sodium hydrogen carbonate (5% by mass), and the remaining 85% by mass of water were mixed together to prepare a coating liquid. (2) Coating The contaminated surface was spray coated using an airless gun and naturally dried at room temperature (25°C). The coating amount was 0.2 mm thick after drying. The contaminated surface had sea salt and other trace contaminants (including oils and fats, and trace amounts of metal oxides) and chlorides of Cs and Sr radioactive nuclides attached to the surface of the SUS substrate. By applying this aqueous solution, the sea salt and the Cs and Sr chlorides dissolve in the water in the polyvinyl alcohol aqueous solution, and the minute amounts of water-insoluble particles are mixed into the film during the drying process and are included in the film. (3) Cleaning method The water evaporated from the applied aqueous solution, and after the film was completely formed, the coating surface was irradiated with a nano-pulse laser, and the coating was peeled off and removed by blowing air between the coating and the SUS substrate interface. This cleaning method utilizes the effect of easily removing surface contaminants from the substrate surface by incorporating contaminants into the coating during the film-forming process caused by the evaporation of water from the weak alkaline polyvinyl alcohol aqueous solution, and also utilizes the film-forming power and heat resistance of the film that is formed. Since the Van der Waals force, which is the adhesion force of the polyvinyl alcohol coating to the SUS substrate, is very low, the processing speed of nano-pulse laser irradiation is improved, and even on curved SUS substrates, contaminants on deeper curves can be removed in film form, preventing fine dust particles of contaminants from scattering into the atmosphere. (4) Pollutant removal equipment The apparatus shown in Figures 1 and 2 was used. The nano-pulse laser oscillator 1 used was manufactured by Narran and has the product name "ROD 500W". This product has an Nd:YAG fiber laser, an average output of 500W, an optical wavelength of 1064-1070nm, a frequency of 10-50kHz, a transmission fiber length of 15-100m, an irradiator weight of 2.5kg, an ambient temperature of 5-45°C, a weight of 245kg, and a power consumption of 5kW. The flat beam shaver 15 used was also manufactured by Narran, brand name “ROD500”. The waveform of the nano-pulse laser light with a square flat top shape irradiated onto the contaminated surface is shown on the right side of Figure 3, and the energy density per unit area is 1 J / cm. 2 , focal diameter: 1.8 mm, pulse width: 20 ns. (5) Coating film removal process After irradiation with the square flat-top nano-pulse laser light, the resin coating was peeled off by blowing air from an air duster (air knife) between the substrate and the polyvinyl alcohol resin coating, as shown in Figure 10. This allowed the contaminants to be peeled off together with the resin coating without diffusing, and the contaminants could be safely disposed of. [Industrial Applicability]

[0031] The contaminant removal device and the contaminant removal method of the present invention are useful for removing harmful substances including radioactive contaminants such as cesium oxide, strontium oxide, etc., and / or chemical contaminants such as polychlorinated biphenyls (PCBs), dioxins, etc. Furthermore, they are also useful in nuclear power-related facilities, waste incineration facilities, etc. [Explanation of symbols]

[0032] 1. Nano-pulse laser oscillator 2 Pulse generator 3 Seed LD3 4,9 Isolator 5,12 Coupler 6,11 Excitation LD 7 Fiber optic cable 8. Preamplifier 10 Bandpass Filters 13 Main amplifier 14 Collimator 15 Flat beam shaver 16a,16b Optical system focus adjuster 17 Scan Head 18 Laser Profiler 19 Irradiation target (contaminated surface) 20 Nano-pulse laser irradiation device 21 Gaussian Shaped Beam 22 Excess energy in Gaussian-shaped beams 23 Irradiation diameter of Gaussian beam 24 Thermal Energy of Gaussian Shaped Beam 25 Square flat top beam 26 Radiation diameter of square flat-top beam 27 Thermal Energy of Square Flat Top Beam 28 Ablation Threshold 30 SUS base material 31 Chloride particles 32 Oil molecules 33 Particulate deposits 34 Coating 35 Polyvinyl alcohol resin 36 Polyvinyl alcohol resin coating 37 Sodium bicarbonate (NaHCO3) particles 38 Microparticles trapped in resin coating 39 Low-temperature evaporation of water 40 Weak adhesive surface 41 Laser irradiation device 42 Nano-pulse laser light 43 Air duster (air knife) 44 Air

Claims

1. A method for removing contaminants by irradiating a contaminated surface with nano-pulse laser light oscillated from a pulse oscillator, the method comprising: coating the contaminated surface with a water-soluble resin solution, and drying the coating; A method for removing contaminants, comprising irradiating a dried film containing contaminants with nano-pulse laser light having a rectangular flat-top shape, and peeling off the contaminants together with the water-soluble resin coating film from the substrate surface without heating and volatilizing them.

2. 2. The method for removing contaminants according to claim 1, wherein the water-soluble resin is at least one selected from the group consisting of polyvinyl alcohol, polyvinyl acetal, polyvinyl acetate, polyvinylpyrrolidone, polyethylene oxide, phenolic hydroxyl group-containing resins, and carboxyl group-containing resins.

3. 3. The method for removing pollutants according to claim 1, wherein the water-soluble resin solution is a solution in which 100 parts by mass of water is added to 1,000 to 10,000 parts by mass of water and dissolved in the water.

4. 3. A method for removing pollutants according to claim 1 or 2, wherein an alkaline substance and / or an acidic substance is added to the water-soluble resin solution to dissolve the pollutants in the water, and the pollutants are dispersed in fine particles in the aqueous resin when the water evaporates.

5. The square flat-top nano-pulse laser light irradiated to the contaminated surface has an energy density per unit area of ​​1 to 10 J / cm 2 3. The method for removing pollutants according to claim 1 or 2,

6. 3. The method for removing contaminants according to claim 1, wherein a focal diameter of the nano-pulse laser light having a square flat-top shape that is irradiated onto the contaminated surface is adjustable within a range of 1 mm or more and 1.8 mm or less.

7. 3. The method for removing contaminants according to claim 1, wherein the contaminant removal device includes a pulsed Nd:YAG laser oscillator that oscillates light of a single wavelength controlled to be equal to or greater than 1064 nm and equal to or less than 1070 nm.

8. 3. The method for removing pollutants according to claim 1, wherein the pulse width of the pulse oscillator is 20 ns or more and 500 ns or less.

9. 3. The method for removing pollutants according to claim 1, wherein the frequency of the pulse oscillator is 10 kHz or more and 50 kHz or less.

10. 3. The method for removing pollutants according to claim 1 or 2, wherein the nano-pulse laser light oscillated by the pulse oscillator has a minimum average output of 500 W or more and a maximum output of 2.5 Mw or more.

11. 3. The method for removing pollutants according to claim 1, further comprising a means for transmitting the nano-pulse laser light oscillated by the pulse oscillator to an irradiation device via a fiber cable having a length of 10 m or more and 150 m or less.

12. 3. The method for removing contaminants according to claim 1 or 2, wherein the nano-pulse laser light oscillated by the pulse oscillator decontaminates a resin film, adhering contaminants, and a substrate surface at 75° C. or less.

13. 3. The method for removing contaminants according to claim 1 or 2, wherein the contaminants are radioactive contaminants and / or chemical contaminants containing a chlorine component.

14. The method for removing contaminants according to claim 1 or 2, wherein the contaminants include metals and / or inorganic substances.

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