JP6304537B2 - Decontamination method for concrete - Google Patents

Description

  The present invention relates to a concrete body decontamination method for decontaminating a surface layer portion such as dirt concrete contaminated with a radioactive substance.

  For example, when an accident occurs at a nuclear power plant or the like, radioactivity may leak out and the surrounding area may be contaminated with radioactive materials.

  There are various types of pollution nuclides in such accidents, but the main nuclides of pollution that will be a problem in the medium to long term after the initial stage are radioactive cesium (Cs-134, Cs-137) and strontium (fission products). Sr-90). If an accident occurs at a nuclear power plant or the like, the surrounding area is mainly contaminated with radioactive cesium, while the building of the nuclear power plant may be contaminated with radioactive strontium as well as radioactive cesium. Conceivable.

  In particular, Cs-137 has a long half-life of about 30 years, and Sr-90 has a long half-life of about 29 years. For this reason, it is difficult to use an area or building contaminated with Cs-137 or Sr-90 unless it is actively decontaminated. For example, since radioactive materials have permeated from the surface to a predetermined depth in the soil and the like, it can be decontaminated by physically removing the surface layer portion.

  However, even in a concrete body such as a building, a radioactive substance penetrates from the surface to a predetermined depth, but it is difficult to physically remove the contaminated surface layer portion without damaging the concrete body.

  For example, as a method for cleaning the surface of a building, cleaning using tap water or the like as clean water is common. For example, in cleaning with a high pressure washer, several tens of liters of purified water per minute is used at a pressure of several MPa.

  Here, as a method of removing the spray material containing asbestos, a liquid-absorbing material that permeates the acidic liquid is placed on the surface of the spray material containing asbestos, and the liquid solution is sprayed on the liquid-absorbing material. There has been proposed a technique for permeating and removing the acidic liquid by permeating the spray material containing asbestos (see, for example, Patent Document 1).

  However, in the area contaminated with radioactive substances as described above, since tap water is also contaminated in the first place, it is necessary to carry in a huge amount of purified water from the outside. Moreover, since the purified water used for cleaning is contaminated, it is necessary to collect a huge volume of contaminated purified water.

  Furthermore, when purified water is sprayed at a high pressure on the surface of a contaminated concrete body, a large amount of splashes and dusts containing radioactive substances are generated and scattered. For this reason, secondary contamination occurs due to the splashes and dusts scattered and scattered. In such work, it is difficult to prevent the worker from being exposed to the radiation.

  In the first place, it is difficult to remove the surface of a high-strength concrete body by jetting high-pressure water. In order to realize this, it is necessary to inject purified water at an extremely high pressure. However, if it does so, while the capacity | capacitance of the required purified water will become enormous, the capacity | capacitance of the contaminated purified water to collect | recover will also become enormous, and the splash and dust which will be scattered and scattered will also be enormous.

  In addition, the technique of patent document 1 is specialized in the removal of the spray material containing asbestos, and cannot be utilized for decontaminating the surface layer part contaminated with the radioactive substance of the concrete body as it is.

  In order to solve the above-mentioned problems, as a method for removing radioactive substances existing on the surface of the concrete body, a fluid supply step for supplying an acidic fluid to the surface of the concrete body whose surface layer is contaminated with radioactive substances, A structure dissolving step in which the cement component of the surface layer portion of the concrete body contaminated by the fluid is dissolved, a decontamination step of sucking and removing the dissolved cement component from the surface of the concrete body, and the dissolved cement A decontamination method comprising a surface neutralization step for neutralizing the surface of a concrete body from which components have been removed by supplying a neutralizing agent, and a surface washing step for washing the surface of the neutralized concrete body with purified water. It has been proposed (see, for example, Patent Document 2). According to the decontamination method described in Patent Document 2, it is possible to effectively remove radioactive substances present in the surface layer portion of the concrete body.

JP 2012-17592 A JP 2014-41100 A

As mentioned above, when the surrounding area has been contaminated with the above radioactive cesium or radioactive strontium that can be released in the event of an accident at a nuclear power plant, etc. Decontamination methods are being studied.
Here, when the decontamination process of a radioactive substance is performed by the method described in Patent Documents 1 and 2, contaminated wastewater containing the radioactive substance removed from the decontamination target is generated. Such contaminated wastewater is a wastewater containing a certain amount or more of radioactive substances, so it cannot be discharged directly into sewers or discharged into the ocean or rivers, so it must be stored strictly in storage facilities such as tanks. It will be necessary.

On the other hand, when contaminated wastewater containing radioactive substances is stored in a tank or the like, it is assumed that the capacity will be very large, which makes it difficult to secure a storage location. For this reason, it is conceivable to remove the radioactive material from the contaminated wastewater and then discard the wastewater from which the radioactive material has been removed or reuse it as cleaning water.
However, in the conventional method for decontaminating concrete bodies including the decontamination method described in Patent Document 2, no method has been proposed for effectively removing radioactive substances from contaminated wastewater generated by decontamination treatment. There wasn't.

  The present invention has been made in view of the above-described problems, and can easily decontaminate a surface layer portion contaminated with a radioactive substance in a concrete body, and also contains a radioactive substance contained in drainage generated by decontamination. The present invention provides a decontamination method for a concrete body that can reliably remove water and perform wastewater treatment.

In order to solve the above-described problems, a decontamination method for a concrete body according to the present invention includes a fluid supply step of supplying an acidic fluid to the surface of a concrete body whose surface layer is contaminated with a radioactive substance, and the supplied acidity A structure dissolving step in which the cement component of the contaminated surface layer portion of the concrete body is dissolved with a fluid, a decontamination step of sucking and removing the cement component dissolved from the surface of the concrete body, and dissolution A surface neutralization step of neutralizing the surface of the concrete body from which the cement component has been removed by supplying a neutralizing agent, a surface cleaning step of washing the neutralized surface of the concrete body with purified water, and the surface after washing step, a soaking step of immersing the concrete body into aqueous sodium hydrogen carbonate solution, the decontamination stearate The dissolved cement component removed in the step, the cleaning wastewater generated in the surface cleaning step, and the immersion wastewater generated in the immersion step are recovered, and these mixed wastewaters are neutralized and then included in the mixed wastewater. And a waste water treatment step for solid-liquid separation of the mixed waste water into a precipitate and treated water.

  Therefore, in this concrete body decontamination method, in the fluid supply step, an acidic fluid is supplied to the surface of the concrete body whose surface layer portion is contaminated with a radioactive substance. Next, it is left until the cement component of the contaminated surface layer portion of the concrete body is dissolved by the supplied acidic fluid in the structure dissolving step. Next, in the decontamination step, the dissolved cement component is removed by suction from the surface of the concrete body. Next, in the surface neutralization step, the surface of the concrete body from which the dissolved cement component has been removed is neutralized by supplying a neutralizing agent. Next, in the surface cleaning step, fine contaminants that could not be removed from the surface of the neutralized concrete body in the contamination removal step are removed by cleaning the purified water. Next, in the dipping step, the concrete body is dipped in an aqueous sodium bicarbonate solution. Next, in the wastewater treatment step, the dissolved cement component removed in the decontamination step, the cleaning wastewater generated in the surface cleaning step, and the immersion wastewater generated in the immersion step are collected, and these mixed wastewaters are collected as After summing, the radioactive material contained in the mixed waste water is agglomerated and precipitated, and the mixed waste water is solid-liquid separated into precipitate and treated water. As a result, it is possible to easily decontaminate the concrete body whose surface layer is contaminated with radioactive substances, and it is possible to reliably remove radioactive substances contained in the wastewater generated by decontamination and perform wastewater treatment. Become.

  In the concrete body decontamination method as described above, in the present invention, the waste water treatment step adds sodium hydroxide as a neutralizing agent to the mixed waste water.

  Therefore, in this concrete body decontamination method, since the mixed waste water containing the radioactive substance is neutralized, the radioactive substance can be effectively coagulated and precipitated in the subsequent steps.

  In the concrete body decontamination method as described above, in the present invention, the waste water treatment step further includes a treatment of adding calcium bicarbonate to the mixed waste water after neutralization to precipitate calcium.

  Therefore, in this decontamination method of concrete body, sodium hydrogen carbonate is added to the mixed waste water after neutralization to precipitate calcium in advance, so that aggregation of radioactive substances is inhibited by calcium in the subsequent steps. It is possible to effectively aggregate and precipitate radioactive materials.

  In the concrete body decontamination method as described above, in the present invention, the waste water treatment step further includes adding Prussian blue to the mixed waste water in which the calcium bicarbonate is precipitated by adding the sodium hydrogen carbonate to add radioactive material. While adsorbing cesium, a titanium hydroxide-supporting resin is added to adsorb radioactive strontium, and then the mixed waste water is stirred, and then the radioactive cesium and each compound adsorbed with radioactive strontium are coagulated and precipitated.

  Therefore, in this decontamination method of concrete body, radioactive cesium is adsorbed to Prussian blue and radioactive strontium is adsorbed to titanium hydroxide-supported resin. Therefore, in the subsequent steps, the radioactive substance is surely precipitated and solid-liquid separated. It becomes possible to do.

  In the concrete body decontamination method as described above, in the present invention, the fluid supply step supplies the acidic fluid of an organic acid to which a surfactant is added.

  Therefore, in this decontamination method of concrete body, as an acidic fluid that dissolves contaminated cement components on the surface of concrete body, it easily penetrates into fine pores and cracks, etc., and has a high dissolving ability, but pH is an inorganic acid. It is possible to supply an acidic fluid which is not so low and has high safety and good reactivity.

  In the concrete body decontamination method as described above, in the present invention, the structure dissolving step further includes the depth of contamination of the concrete body, the dissolving ability of the acidic fluid, It is allowed to stand for a time corresponding to at least one of the acid dissociation constants of the acidic fluid.

  Therefore, in this concrete body decontamination method, the concrete body to which the acidic fluid has been supplied corresponds to at least one of the depth of contamination, the dissolving ability of the acidic fluid, and the acid dissociation constant of the acidic fluid. Since it is left until time, the contaminated cement component of the surface layer portion is surely dissolved.

In the concrete body decontamination method as described above, in the present invention, the contamination removing step is performed before the precipitates that precipitate together with the dissolution of the cement component of the concrete body are solidified.

  Therefore, in this decontamination method of the concrete body, a precipitate is deposited with the dissolution of the cement component of the concrete body, but this precipitate is removed before solidifying.

  The various components of the present invention do not necessarily have to be independent of each other. A plurality of components are formed as a single member, and a single component is formed of a plurality of members. It may be that a certain component is a part of another component, a part of a certain component overlaps with a part of another component, or the like.

  In addition, the concrete body referred to in the present invention is a so-called cement mixed with water or gravel, etc., solidified using cement instead of asphalt, so-called soil-concrete, surface-cement finished, surface mortar For example, a finished body, etc. is included. For example, in addition to an outer wall, an inner wall, a roof, a veranda, etc. of various buildings, a concrete body that does not constitute a structure, such as precast concrete, is also included.

  In the decontamination method for a concrete body described in the present invention, an acidic fluid is supplied to the surface of the concrete body whose surface layer is contaminated with a radioactive substance, and the contaminated cement component on the surface of the concrete body is supplied with the supplied acidic fluid. The dissolved cement component is removed by suction from the surface of the concrete body, the surface of the concrete body from which the dissolved cement component has been removed is neutralized by supplying a neutralizing agent, and the surface of the neutralized concrete body To remove fine pollutants from clean water. Further, in the concrete body decontamination method according to the present invention, the concrete body is immersed in an aqueous sodium hydrogen carbonate solution, the dissolved cement component removed in the decontamination step, the cleaning wastewater generated in the surface cleaning step, and the immersion After the immersion wastewater generated in the step is collected and the mixed wastewater is neutralized, radioactive substances contained in the mixed wastewater are coagulated and settled, and the mixed wastewater is solid-liquid separated into precipitate and treated water. This makes it possible to easily decontaminate a concrete body whose surface layer is contaminated with radioactive material, and to reliably remove the radioactive material contained in the wastewater generated by decontamination of the concrete body, and to perform wastewater treatment. Is possible.

It is a typical flowchart which shows the decontamination method of the concrete body of embodiment of this invention. It is a schematic diagram which shows the structure of the concrete decontamination system of embodiment of this invention. It is a typical vertical front view which shows the concrete body which will be decontaminated with the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention. It is a typical vertical front view which shows the state in which the concrete body decontaminated with the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention is contaminated with a radioactive substance. It is a typical vertical front view which shows the state which supplies the acidic fluid to the concrete body contaminated by the fluid supply step of the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention. It is a typical vertical front view which shows the state by which the acidic fluid was supplied to the concrete body contaminated by the fluid supply step of the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention. It is a typical vertical front view which shows the state which the acidic fluid osmose | permeated to the surface layer part which the concrete body was contaminated by the structure melt | dissolution step of the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention. It is a typical vertical front view which shows the state which has removed the contaminated surface layer part of the concrete body in the decontamination step of the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention. The typical vertical front view which shows the state which wash | cleans the surface of the concrete body from which the surface layer part contaminated by the surface washing | cleaning step of the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention was removed It is. It is a typical vertical front view which shows the concrete body from which the surface layer part contaminated with the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention was removed. It is a typical vertical front view which shows the processing method of the waste_water | drain contaminated at the waste_water | drain processing step of the decontamination method of the concrete body by the concrete decontamination system of embodiment of this invention.

  Next, an embodiment of the present invention will be described below with reference to the drawings. 1 is a schematic flowchart showing the concrete body decontamination method of the present embodiment, FIG. 2 is a schematic diagram showing the configuration of the concrete decontamination system of the present embodiment, and FIGS. FIG. 2 is a schematic longitudinal sectional front view showing a concrete body decontamination method by the concrete decontamination system of the present embodiment.

  The concrete decontamination system 100 of this Embodiment has the fluid supply apparatus 110, the decontamination apparatus 120, the surface washing apparatus 130, and the waste water treatment apparatus 140, as shown in FIG.

  The fluid supply device 110 includes a solution tank 111, a flexible tube 112 connected to the solution tank 111, a fluid pump 113 through which the flexible tube 112 is inserted, and an injection nozzle 114 connected to the tip of the flexible tube 112. And having.

  The solution tank 111 contains an acidic solution AL that is an acidic fluid. The acidic solution AL is composed of an organic acid solution that has a dissolution ability as compared with an inorganic acid but does not have a low pH and a high acid dissociation constant. The organic acid of the acidic solution AL is a simple substance or a mixture of food additives such as citric acid, malic acid, fermented lactic acid and tartaric acid.

  As this acidic solution AL, a high-concentration solution may be used, but it is preferable to dilute with water or the like in consideration of affinity with a concrete body CS such as soil concrete. The organic acid concentration of such an acidic solution AL may be 0.1% by mass to 100% by mass, and particularly preferably about 10% by mass to 20% by mass.

  The flexible tube 112 is inserted into the fluid pump 113 as described above, and connects the solution tank 111 and the injection nozzle 114, and the acidic solution AL flows. The fluid pump 113 pumps the acidic solution AL from the solution tank 111 to the injection nozzle 114 through the flexible tube 112. The injection nozzle 114 injects the acidic solution AL to be pumped.

  The decontamination device 120 includes a waste tank 121, a flexible tube 122 connected to the waste tank 121, a fluid pump 123 through which the flexible tube 122 is inserted, and a suction nozzle 124 connected to the tip of the flexible tube 122. And having.

  As will be described later in detail, the waste tank 121 stores the cement component CB that has been dissolved and sucked. The flexible tube 122 is inserted through the fluid pump 123 as described above, and connects the waste tank 121 and the suction nozzle 124, and the dissolved cement component CB flows.

  The fluid pump 123 pumps the melted cement component CB from the suction nozzle 124 to the waste tank 121 through the flexible tube 122. The suction nozzle 124 is used to suck the dissolved cement component CB.

  The surface cleaning device 130 includes a water purification tank 131 and a waste water tank 132, a first flexible tube 133 and a second flexible tube 134 individually connected to the water purification tank 131 and the waste water tank 132, and the first flexible tube. The pump 133 and the suction pump 136 into which the tube 133 and the second flexible tube 134 are individually inserted, and the injection nozzle 137 individually connected to the tips of the first flexible tube 133 and the second flexible tube 134. And a suction nozzle 138.

  The purified water tank 131 contains purified water CW such as tap water and pure water. As described above, the first flexible tube 133 is inserted through the pressure pump 135 and connects the water purification tank 131 and the first injection nozzle 137, and the water purification CW flows.

  The pumping pump 135 pumps the purified water CW from the purified water tank 131 to the spray nozzle 137 with the first flexible tube 133, and the spray nozzle 137 sprays the pumped purified water CW.

  As will be described in detail later, the waste water tank 132 stores the purified water CW from which the contaminant AC has been washed. Further, the second flexible tube 134 is inserted through the suction pump 136 as described above, and connects the waste water tank 132 and the suction nozzle 138, and the purified water CW from which the contaminant AC has been washed flows.

  The suction pump 136 pumps the purified water CW from which the contaminant AC has been washed from the suction nozzle 138 to the waste water tank 132 through the second flexible tube 134. Further, the suction nozzle 138 is used for suction of the purified water CW that has cleaned the contaminant AC. The suction nozzle 138 and the injection nozzle 137 are integrated in parallel.

  The waste water treatment device 140 includes a stirring and mixing tank 141, a drain introduction pipe 142 communicating with the stirring and mixing tank 141, a neutralizing agent supply unit 143, a sodium hydrogen carbonate supply unit 144, a Prussian blue supply unit 145, and a titanium hydroxide-supported resin. It has supply 146 and supply pipes 143a, 144a, 145a, 146a for supplying each compound from each of these supply toward the stirring mixed layer 141.

  The stirring and mixing layer 141 is generated by immersing the dissolved cement component CB sucked by the decontamination device 120, the purified water (washed water) CW sucked by the surface cleaning device 130, and the concrete body CS in an aqueous sodium bicarbonate solution. Collected waste water (not shown) is collected and mixed. The agitation / mixing layer 141 neutralizes the mixed waste water ML (see FIG. 11) by adding a neutralizing agent, and then aggregates and precipitates radioactive substances contained in the mixed waste water, and further precipitates the mixed waste water. This is a treatment tank that separates the product and treated water into solid and liquid, and is provided with stirring means (not shown).

  The drainage introduction pipe 142 is a pipe for introducing the recovered dissolved cement component CB, purified water (cleaning purified water) CW, and immersion drainage (not shown) into the agitation and mixing layer 141, and the above-described drainage and the like are pumped. Flow in the tube by means (not shown).

  The neutralizer supplier 143 adds a neutralizer to the mixed waste water ML in the stirring and mixing layer 141 through the supply pipe 143a. As the neutralizing agent supplied by the neutralizing agent supplier 143, for example, sodium hydroxide is used.

  The sodium hydrogencarbonate feeder 144 precipitates calcium contained in the mixed wastewater ML in advance by adding sodium hydrogencarbonate to the mixed wastewater ML in the stirring and mixing layer 141 through the supply pipe 144a.

  The Prussian blue supplier 145 adds Prussian blue through the supply pipe 145a to the mixed waste water ML in the stirring mixed layer 141 in which the calcium compound is precipitated by the addition of sodium hydrogen carbonate. The radioactive cesium contained in the mixed waste water ML is adsorbed by Prussian blue and becomes a precipitate.

  The titanium hydroxide-supported resin supplier 146 adds the titanium hydroxide-supported resin through the supply pipe 146a to the mixed waste water ML in the stirring and mixing layer 141 in which the calcium compound is precipitated by the addition of sodium hydrogen carbonate. Radioactive strontium contained in the mixed waste water ML is adsorbed on the titanium hydroxide-supporting resin and becomes a precipitate.

  As described above, the stirring and mixing layer 141 is provided with stirring means (not shown). This stirring means stirs the mixed waste water ML in which the compound containing the radioactive substance is precipitated, and then stops the stirring operation, thereby aggregating and precipitating each compound containing the radioactive substance in the stirring and mixing layer 141. Thereafter, the mixed wastewater ML in the stirring and mixing layer 141 is subjected to solid-liquid separation, whereby the mixed wastewater ML is treated with a precipitate made of a compound containing a radioactive substance and a content of the radioactive substance removed to a predetermined concentration or less. Separate into water.

  In the above-described configuration, the concrete body CS decontamination method by the concrete decontamination system 100 of the present embodiment will be described below in order with reference to FIGS. 1 and 3 to 11.

  First, as shown in FIG. 3, when a concrete body CS such as soil concrete not contaminated with the radioactive material RM is constructed, for example, when the radioactive material RM is scattered due to an accident at a nuclear power plant or the like, FIG. As shown, the surface layer portion SL of the concrete body CS is contaminated by the radioactive material RM.

  Therefore, in the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment, first, as shown in FIGS. 1 and 5, first, as the fluid supply step S1, the surface layer portion SL is formed with the radioactive material RM. The acidic solution AL is supplied by the fluid supply device 110 to the surface of the concrete body CS contaminated with water.

  At this time, the fluid supply device 110 injects the organic acid acidic solution AL composed of the food additive from the solution nozzle 111 from the injection nozzle 114 by the pressure of the fluid pump 113 as described above.

  As shown in FIG. 6, when the acidic solution AL is evenly applied to the entire surface of the concrete body CS contaminated by this injection, as shown in FIG. 1, the supplied acidic solution is used as a cement dissolution step S2. The contaminated cement component CB on the surface of the concrete body CS is dissolved by AL.

  In this cement dissolving step S2, as shown in FIG. 7, the cement component CB of the surface layer portion SL contaminated with the concrete body CS is left to dissolve with the supplied acidic solution AL.

  For this reason, until the time corresponding to the depth of contamination of the concrete body CS, the acid dissociation constant indicating the dissolving ability of the acid solution AL, the temperature of the concrete body CS, the temperature of the atmosphere, etc. from the supply of the acid solution AL to the concrete Leave the body CS.

  As described above, the standing time is adjusted according to a plurality of conditions as described above, and is, for example, 1 to 60 minutes, more preferably 5 to 60 minutes. Then, the acidic solution AL permeates into the contaminated surface layer portion SL of the concrete body CS, so that the surface layer portion SL is dissolved in the acidic solution AL to become a contaminated cement component CB.

  In such a state, as shown in FIG. 1 and FIG. 8, as a contamination removal step S3, the dissolved cement component CB is removed from the surface of the concrete body CS by the contamination removal device 120. At this time, the decontamination device 120 sucks the cement component CB from the suction nozzle 124 by the negative pressure generated by the fluid pump 123 and stores it in the waste tank 121.

  In addition, when the cement component CB of the concrete body CS is dissolved by the acidic solution AL as described above, a precipitate (not shown) is deposited. Therefore, in the above-described contamination removal step S3, it is preferable to remove the cement component CB before the deposited precipitate is solidified.

  When the removal of the cement component CB is completed, a neutralizing agent such as baking soda is sprayed on the surface of the concrete body CS as a surface neutralization step S4. Further, in order to eliminate the uneven distribution of the sprayed neutralizing agent, the surface of the concrete body CS to which the neutralizing agent is sprayed is brushed with a deck brush or the like. And using pH test paper etc., it confirms that the surface of concrete body CS became neutral about pH 5-9, more preferably about pH 6-8 (not shown).

  When this neutralization is confirmed, basically, the decontamination work of the concrete body CS contaminated with this is completed. However, even if the cement component CB dissolved in the decontamination apparatus 120 is removed from the surface of the concrete body CS as described above, the contaminated cement component CB is removed from the surface of the concrete body CS as shown in FIG. Fine contaminants AC may remain on the surface.

  Therefore, in the decontamination method using the concrete decontamination system 100 of the present embodiment, the fine contaminant AC remaining on the surface of the concrete body CS from which the dissolved cement component CB has been removed in the contamination removal step S3 is generally used. Aspirated by a typical vacuum cleaner or the like (not shown).

  Furthermore, in the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment, the fine contaminant AC as described above is removed by a vacuum cleaner or the like, and then FIG. 1 and FIG. As shown in FIG. 5, the surface of the concrete body CS neutralized with the neutralizing agent in the surface neutralization step S4 after the cement component CB dissolved in the decontamination step S3 is removed is used as a surface cleaning step S5. Wash with.

  At this time, the surface cleaning device 130 injects the purified water CW accommodated in the purified water tank 131 from the injection nozzle 137 to the surface of the concrete body CS with the pressure of the pressure feed pump 135, and simultaneously from the surface of the concrete body CS, The purified water CW mixed with the contaminant AC is stored in the waste water tank 132 from the suction nozzle 138 by the negative pressure of the suction pump 136.

  Thus, as shown in FIG. 10, the concrete body CS is in a state in which the surface layer portion SL contaminated with the radioactive substance RM is removed and the remaining fine contaminant AC is also washed. Thus, in the concrete body CS decontamination method by the concrete decontamination system 100 of the present embodiment, the concrete body CS contaminated with the radioactive substance RM can be easily decontaminated.

  Furthermore, in the decontamination method of the present embodiment, the concrete body CS is immersed in an aqueous sodium hydrogen carbonate solution using an immersion tank (not shown) as the immersion step S6 shown in FIG. By this immersion step S6, for example, when radioactive strontium or the like slightly remains as the contaminant AC on the surface of the concrete body CS, it can be taken out as a precipitate into the immersion waste water.

  As described above, the cement component CB removed from the surface of the concrete body CS by the contamination removing device 120, the fine contaminant AC sucked by a vacuum cleaner, etc., and the waste water tank 132 of the surface cleaning device 130 are accommodated. The immersion waste water generated when the purified water CW and the concrete body CS are immersed in the sodium hydrogen carbonate aqueous solution can be temporarily stored in a drum can or the like as a temporary storage step (not shown).

  And in the decontamination method of the concrete body CS by the concrete decontamination system 100 of this Embodiment, the waste water treatment as shown in FIG. 2 and FIG. The waste water treatment apparatus 140 decontaminates each contaminated waste water as a waste water treatment step S7.

  Specifically, in the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment, using the wastewater treatment device 140, as the wastewater treatment step S7, the contamination collected and temporarily stored in a drum can or the like. Dissolved cement component CB removed in removal step S3, purified water (washing wastewater) CW as wastewater generated in surface cleaning step S5, and immersion wastewater (not shown) generated in immersion step S6 Through 142, the pressure mixing means (not shown) is used to introduce the mixture into the stirring and mixing tank 141 to obtain the mixed waste water ML.

  Next, in the wastewater treatment step S7, neutralization is performed by adding a neutralizer from the neutralizer supplier 143 through the supply pipe 143a to the mixed wastewater ML in the stirring and mixing layer 141. Examples of the neutralizing agent used at this time include sodium hydroxide.

Next, in the waste water treatment step S7, calcium bicarbonate contained in the mixed waste water ML is added to the mixed waste water ML after neutralization in the stirring mixed layer 141 by adding sodium hydrogen carbonate from the sodium hydrogen carbonate feeder 144 through the supply pipe 144a. (Ca) is precipitated as calcium carbonate (CaCO ₃ ). At this time, sodium hydrogen carbonate is added until the amount of precipitate formed reaches an equilibrium state, and the addition of sodium hydrogen carbonate is stopped when the precipitate no longer increases.
At this time, a precipitate of calcium is generated, and radioactive strontium contained in the mixed waste water ML is also precipitated as strontium carbonate (SrCO ₃ ).

  In the decontamination method described in the present embodiment, the reason for precipitating calcium by adding sodium hydrogen carbonate to the mixed waste water ML after neutralization is as follows. When calcium is contained in the mixed waste water ML when the resin is added, this calcium reacts with titanium hydroxide, and it becomes difficult to obtain the radioactive strontium precipitation effect due to the addition of the titanium hydroxide-supporting resin. is there. In the present embodiment, after neutralizing the mixed wastewater ML, by immediately adding sodium bicarbonate to precipitate calcium, radioactive strontium can be precipitated more effectively in the subsequent treatment, Decontamination effect is enhanced.

  Next, in the waste water treatment step S7, the mixed waste water ML is further added to the mixed waste water ML after the calcium is precipitated in the stirring mixed layer 141 by adding Prussian blue from the Prussian blue supply device 145 through the supply pipe 145a. The radioactive cesium contained in is adsorbed on Prussian blue, and the radioactive cesium is precipitated. At the same time, in the waste water treatment step S7, the titanium hydroxide-supporting resin is added to the mixed waste water ML, so that the radioactive strontium contained in the mixed waste water ML is adsorbed on the titanium hydroxide-supporting resin, and the radioactive strontium is precipitated.

  Next, in the wastewater treatment step S7, the mixed wastewater ML in a state where various precipitates are generated is stirred in the stirring and mixing layer 141 using a stirring means (not shown). Then, the mixed waste water ML in a sufficiently agitated state is allowed to stand for a predetermined time, whereby the radioactive cesium and the radioactive strontium are coagulated and precipitated in a state where they are adsorbed on the Prussian blue or titanium hydroxide-supported resin.

  Thereafter, in the waste water treatment step S7, the mixed waste water ML is separated into the above precipitate and treated water by solid-liquid separation, thereby separating the radioactive substance as a precipitate, and the treated water from which the radioactive substance has been removed to a predetermined concentration or less. Get. The treated water after decontamination obtained by the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment has been obtained by removing radioactive substances to a predetermined amount or less. For example, this treated water is discarded. Or it can be reused as cleaning water.

  As described above, in the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment, the contaminated cement component CB is dissolved on the surface of the concrete body CS washed with the purified water CW as described above. Therefore, the surface of the concrete body CS can be decontaminated with a small amount of purified water CW.

  In particular, since the surface of the concrete body CS is washed with the purified water CW and at the same time the purified water CW mixed with the contaminant AC is sucked in, the contaminant AC does not remain on the surface of the washed concrete body CS or the surroundings.

  Moreover, in the concrete body CS decontamination method by the concrete decontamination system 100 of the present embodiment, the acidic solution AL of the organic acid is supplied to the concrete body CS by the fluid supply device 110 in the fluid supply step S1.

  Therefore, as the acidic solution AL for dissolving the contaminated cement component CB on the surface of the concrete body CS, an acidic solution AL having a high dissolving ability but a pH not lower than that of an inorganic acid and having a high safety and a good reactivity is supplied. be able to.

  In particular, since the organic acid acidic solution AL made of food additives is supplied, the acidic solution AL that has been confirmed to be harmless to the human body can be supplied. Moreover, the liquid acidic solution AL is supplied to the surface of the concrete body CS. For this reason, the acidic solution AL can be supplied in a liquid state that penetrates well into the surface of the concrete body CS.

  Furthermore, in the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment, the cement component CB of the surface layer portion SL of the concrete body CS contaminated with the supplied acidic solution AL is used as the cement dissolution step S2. Leave until dissolved.

  Therefore, the cement component CB of the contaminated surface layer portion SL of the concrete body CS to which the acidic solution AL is supplied can be reliably dissolved.

  In particular, in the cement dissolving step S2, after the acidic solution AL is supplied, the concrete body CS is left for a time corresponding to the depth of contamination of the concrete body CS and the acid dissociation constant indicating the dissolving ability of the acidic solution AL.

  Therefore, the cement component CB of the contaminated surface layer portion SL of the concrete body CS supplied with the acidic solution AL can be surely dissolved without excess or deficiency.

  Moreover, in the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment, the dissolved cement component CB is sucked and removed by the decontamination device 120 in the decontamination step S3.

  Therefore, since the cement component CB dissolved from the concrete body CS is removed by suction, the contaminated and dissolved cement component CB is removed without scattering around.

  In particular, precipitates are precipitated with the dissolution of the cement component CB of the concrete body CS. In the contamination removal step S3, the precipitates are removed before solidifying, so that the solidified precipitates adhere to the surface of the concrete body CS. Can be prevented.

  In addition, in order to verify the effect | action of the decontamination method of concrete body CS by said concrete decontamination system 100, this inventor actually conducted experiment which dissolves a concrete body with an acidic solution.

In the experiment, a concrete body was prepared by blending according to the design strength standard 27 (N / mm ² ) and standard curing at 100 mmφ × 200 mmH for 28 days. Next, an aqueous solution of 20% by mass of citric acid, an aqueous solution of 20% by mass of malic acid, an aqueous solution of 20% by mass of fermented lactic acid, and an aqueous solution of 20% by mass of tartaric acid were prepared as acidic solutions.

  And the concrete body was immersed in these various acidic solutions for 1 hour, and the change of the diameter was measured. Then, as shown in Table 1 below, it was found that the diameters decreased by about 0.3 mm to 0.8 mm, respectively, as compared to the standard concrete body that was not immersed in the acidic solution.

  From this, it was confirmed that the surface layer of the concrete body CS can be sufficiently dissolved in a practical time by the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment.

  Furthermore, in the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment, as the waste water treatment step S7, the dissolved cement component CB removed in the contamination removal step S3, the waste water generated in the surface cleaning step S5. The purified water (washing wastewater) CW and the immersion wastewater (not shown) generated in the immersion step S6 are collected. And after neutralizing these mixed waste water ML, radioactive cesium and radioactive strontium are coagulated and settled, so that these radioactive substances are surely precipitated, and further, the mixed waste water ML is solid-liquid separated into precipitate and treated water. Therefore, the radioactive material contained in the wastewater generated by the decontamination of the concrete body CS can be surely removed and the wastewater treatment can be performed.

  In addition, in the wastewater treatment step S7 of the present embodiment, sodium bicarbonate is added to the neutralized mixed wastewater ML to preliminarily precipitate calcium, and in subsequent steps, radioactive is caused by calcium. Aggregation of the substance is not inhibited, and the radioactive substance can be effectively aggregated and precipitated.

  Further, in the wastewater treatment step S7 of the present embodiment, radioactive cesium contained in the mixed wastewater ML is adsorbed on Prussian blue, and radioactive strontium is adsorbed on the titanium hydroxide-supported resin, so that these radioactive substances are absorbed. By adopting a method of coagulating and precipitating together with each compound, it is possible to reliably coagulate and precipitate the above-mentioned radioactive substance and perform solid-liquid separation.

  Therefore, according to the decontamination method of the concrete body CS by the concrete decontamination system 100 of the present embodiment, by adopting the above method, the concrete body whose surface layer portion is contaminated with radioactive substances can be easily decontaminated. In addition, it has an excellent effect that the radioactive substance contained in the wastewater generated by decontamination of the concrete body can be surely removed and the wastewater treatment can be performed.

  The present invention is not limited to the present embodiment, and various modifications are allowed without departing from the scope of the present invention. For example, in the above embodiment, it is assumed that the operator manually operates the fluid supply device 110, the decontamination device 120, the surface cleaning device 130, and the wastewater treatment device 140 of the concrete decontamination system 100.

  However, in the present invention, the concrete decontamination system (not shown) connected to the robot arm or the like from the fluid supply device 110, the decontamination device 120, the surface cleaning device 130, and the waste water treatment device 140 as described above. Or the like, and the concrete decontamination work may be performed by remote control.

  Moreover, in the said form, although using the acidic solution AL of an organic acid was illustrated in fluid supply step S1 by the fluid supply apparatus 110, you may use the acidic solution of an inorganic acid.

  Furthermore, in the said form, although it illustrated using food additives, such as a citric acid, malic acid, fermented lactic acid, tartaric acid, as the acidic solution AL of organic acid, food addition, such as an acetic acid, formic acid, oxalic acid, was carried out. An organic acid which is not a product may be used.

  Moreover, in the said form, using the acidic solution AL of an organic acid as it illustrated was illustrated. However, a surfactant may be added to such an acidic solution AL. In this case, the acidic solution AL can be easily infiltrated into fine pores or cracks on the surface of the concrete body CS.

  As described above, the surfactant added to the acidic solution AL may be any surfactant that can ensure stability with an acid, and anionic, cationic, nonionic, or other surfactants can be used.

  In addition, as mixing | blending of such surfactant, 0.01 mass%-10 mass% may be sufficient with respect to the acidic solution AL, and about 0.5 mass%-2 mass% are good especially.

  Moreover, in the said form, it illustrated that the acidic solution AL was sprayed and apply | coated to the surface of the concrete body CS by the fluid supply apparatus 110 by fluid supply step S1. However, it may be applied with a brush or a roller.

  Furthermore, in the said form, supplying the acidic solution AL of a liquid state to the surface of concrete body CS by the fluid supply apparatus 110 by fluid supply step S1 was illustrated. However, the acidic solution AL in a vapor state may be supplied and liquefied on the surface of the concrete body CS.

  Moreover, in the said form, the cement component CB melt | dissolved by contamination removal step S3 is removed, and the surface of the concrete body CS neutralized with the neutralizing agent by surface neutralization step S4 is wash | cleaned by purified water CW by surface washing step S5. Exemplified what to do.

  However, the surface of the concrete body CS from which the cement component CB dissolved in the decontamination step S3 has been removed is neutralized and washed with purified water in which a neutralizing agent is mixed or dissolved as a surface neutralization step and a surface cleaning step. It may be done (not shown).

  Needless to say, the above-described embodiment and a plurality of modifications can be combined within a range in which the contents do not conflict with each other. Further, in the above-described embodiments and modifications, the structure of each part has been specifically described, but the structure and the like can be changed in various ways within a range that satisfies the present invention.

DESCRIPTION OF SYMBOLS 100 ... Concrete decontamination system, 110 ... Fluid supply apparatus, 120 ... Decontamination apparatus, 130 ... Surface washing apparatus, 140 ... Waste water treatment apparatus, CS ... Concrete body, ML ... Mixed waste water, S1 ... Fluid supply step, S2 ... Cement Dissolution step, S3 ... contamination removal step, S4 ... surface neutralization step, S5 ... surface cleaning step, S6 ... dipping step, S7 ... drainage treatment step.

Claims (7)

A fluid supply step for supplying an acidic fluid to the surface of the concrete body whose surface layer is contaminated with radioactive material;
A structure dissolving step that is allowed to stand until the cement component of the contaminated surface portion of the concrete body is dissolved by the supplied acidic fluid;
A decontamination step of sucking and removing the cement component dissolved from the surface of the concrete body;
A surface neutralization step of neutralizing the surface of the concrete body from which the dissolved cement component has been removed by supplying a neutralizing agent;
A surface washing step of washing the neutralized surface of the concrete body with purified water;
After the surface cleaning step, an immersion step of immersing the concrete body in an aqueous sodium bicarbonate solution;
The dissolved cement component removed in the decontamination step, the cleaning wastewater generated in the surface cleaning step, and the immersion wastewater generated in the immersion step are recovered, and the mixed wastewater is neutralized and then mixed. A decontamination method for a concrete body, comprising: a wastewater treatment step for coagulating and precipitating radioactive substances contained in wastewater and further solid-liquid separating the mixed wastewater into precipitate and treated water.   The said waste water treatment step is a decontamination method of the concrete body of Claim 1 which adds sodium hydroxide as a neutralizing agent to the said mixed waste water.   The said waste water treatment step is a decontamination method of the concrete body of Claim 1 or Claim 2 including the process which adds sodium hydrogencarbonate to the said mixed waste water after neutralization, and precipitates calcium.   In the waste water treatment step, Prussian blue is added to adsorb radioactive cesium to the mixed waste water in which calcium bicarbonate is precipitated by adding sodium hydrogen carbonate, and a titanium hydroxide-supporting resin is added to add radioactive strontium. The concrete body decontamination method according to claim 3, wherein after adsorbing the mixture, and then stirring the mixed waste water, the compounds adsorbed with the radioactive cesium and the radioactive strontium are coagulated and precipitated.   The said fluid supply step is a decontamination method of the concrete body as described in any one of Claims 1-4 which supplies the said acidic fluid of the organic acid which added surfactant.   The structure dissolving step is a time corresponding to at least one of the depth of contamination of the concrete body, the dissolving ability of the acidic fluid, and the acid dissociation constant of the acidic fluid after the acidic fluid is supplied. The concrete body decontamination method according to any one of claims 1 to 5, wherein the concrete body is left to stand. The decontamination step is removed before the precipitates precipitated with dissolution of the cement component of the concrete bodies is solidified, the decontamination methods of the concrete body according to any one of claims 1 to 6.

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