JP2016090556A - Treatment system for radioactive contaminated water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment system capable of stably performing an advanced decontamination treatment of the radioactive contaminated water throughout a long period.SOLUTION: Water to be treated, which contains a radioactive substance, is subjected to (1) a pre-treatment for releasing hydrogen bonding between water molecules, (2) a primary separation treatment for stir-mixing the pre-treated water to be treated in a primary adsorption treatment tank with adsorption material powder added thereto, agglomerating the water to be treated led out from the primary adsorption treatment tank by adding an inorganic coagulant thereto, and filtering an agglomerate to remove the same; and (3) a secondary separation treatment for allowing the water to be treated after the primary separation treatment to pass through a granular adsorption material layer and filtering the water to be treated passing therethrough with a spring filter pre-coated with a filter aid so as to separate minute sludge in the water to be treated to remove the minute sludge.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a treatment system for radioactive contaminated water containing radioactive nuclides such as radioactive cesium and radioactive strontium as a suspended substance, for example, the treatment system useful for removing radioactive substances in contaminated stagnant water at the Fukushima Daiichi Nuclear Power Station.

  At the Fukushima Daiichi Nuclear Power Station, where an explosion occurred in 2011, a large amount of radioactive contaminated water is continuously generated, but sufficient decontamination means have not been established, and storage to store radioactive contaminated water While the number of tanks continues to increase, it is difficult to secure the installation location. On the other hand, accidents involving the leakage of high-dose contaminated water often occur due to radiation deterioration of the packing intervening in the storage tanks and pipe connections. It has fallen into a situation.

  Currently, as a means of decontamination at the Fukushima Daiichi Nuclear Power Station, a multi-nuclide removal facility (hereinafter referred to as the pretreatment facility that performs iron coprecipitation and carbonate coprecipitation) and an adsorbent exchange type multiple adsorption tower in series (Referred to as ALPS) is employed (Non-patent Document 1). However, in ALPS, reverse osmosis membranes and ceramic filters used for filtration become clogged in a short period of time and lose their function. Therefore, these replacement operations are often forced to interrupt processing, and adsorbents. The frequent replacement of expensive materials for advanced processing, including high costs, results in very high maintenance costs and large amounts of used material as non-disposable radioactive contaminants.

Internet web, TEPCO, Multi-nuclide removal equipment (ALPS), search date: June 13, 2014, http // www.tepco.co.jp / nu / fukushima-np / genkyo / fp_alps / index.html

  In view of the current situation of the Fukushima Daiichi nuclear power plant described above, the present invention provides a high-level decontamination treatment of radioactive contaminated water as a pre-treatment for reducing the current load of ALPS and a treatment that can be substituted for the ALPS. An object of the present invention is to provide a treatment system that can perform stably and efficiently over a long period of time.

  In order to achieve the above object, a treatment system for radioactive polluted water according to claim 1 of the present invention is directed to treating the pretreated water in the primary adsorption treatment tank with respect to the treated water containing radioactive substances. Add the powder, stir and mix, add the inorganic flocculant to the water to be treated derived from this primary adsorption treatment tank and agglomerate, filter the filtered aggregates, and the water to be treated after the primary separation treatment. Permeate the granular adsorbent layer and filter the permeate to be treated with a spring filter pre-coated with a filter aid to perform a secondary separation process for separating and removing fine sludge in the water to be treated. It is characterized by that.

  According to a second aspect of the present invention, in the radioactively contaminated water treatment system according to the first aspect, the secondary separation treatment is performed by a circulation treatment that returns the filtered water from the spring filter to the treated water introduction portion of the granular adsorbent layer. The water to be treated is configured to pass through the spring filter and the granular adsorbent layer a plurality of times.

  According to a third aspect of the present invention, in the radioactively contaminated water treatment system according to the second aspect, the secondary separation treatment includes a plurality of circulation treatment steps each including the granular adsorbent layer and a spring filter. The to-be-processed water which passed through the circulation process process shall be comprised so that it may be continuously sent to the next-stage circulation process process.

  According to a fourth aspect of the present invention, in the radioactive contaminated water treatment system according to any one of the first to third aspects, the spring filter has an outer peripheral surface of a long coil encapsulated by a fiber filter medium. The filter aid is precoated on the outside of the fiber filter medium, and backwashing means is provided by introducing compressed air into the inside of the long coil.

  The invention of claim 5 is the treatment system for radioactive polluted water according to any one of claims 1 to 4, wherein the adsorbent for the primary separation treatment is a powder mainly composed of one or both of zeolite and diatomaceous earth. It is said.

The invention according to claim 6 is the treatment system for radioactive contaminated water according to any one of claims 1 to 5, wherein the inorganic flocculant of the primary separation treatment generates at least one of Al ³⁺ and Ca ^{2+ in} water. The composition is made of an inorganic electrolyte.

  A seventh aspect of the present invention is the radioactive contaminated water treatment system according to any one of the first to sixth aspects, wherein the aggregate is filtered and removed in the primary separation process by a belt press.

  Invention of Claim 8 is a processing system of radioactive contamination water in any one of the said Claims 1-7, The powder adsorbent corresponding to the nuclide of the radioactive substance which should be removed to the filter aid of the said spring filter It is configured to include.

  The invention of claim 9 is the treatment system for radioactive contaminated water according to any one of claims 1 to 8, wherein the pretreatment water to be subjected to the primary separation treatment is in a high magnetic field of 5,000 gauss or more. It is set as the structure which performs the magnetic process which makes this to-be-processed water pass.

  The invention of claim 10 is the treatment system for radioactive contaminated water according to any one of claims 1 to 8, wherein the treated water contained in the stirring tank is pretreated as pretreated water to be subjected to primary separation treatment. The configuration is such that high-speed stirring processing is performed for 10 hours or more at a stirring blade speed of 10,000 or more.

  Invention of Claim 11 adds the low concentration acidic mineral to the to-be-processed water as a pre-processing of the to-be-processed water used for a primary separation process in the processing system of the radioactive contamination water in any one of the said Claims 1-8 It is configured to mix.

  In the radioactively contaminated water treatment system according to the first aspect of the present invention, the water to be treated containing radioactive substances is first mixed as a primary separation treatment by adding adsorbent powder in the primary adsorption treatment tank and stirring and mixing. Since the suspended substances in water are adsorbed by the adsorbent particles, the adsorbent that has adsorbed the suspended substances in water immediately aggregates by adding an inorganic flocculant to the water to be treated derived from this primary adsorption treatment tank. Then, it is converted into a coarse aggregate precipitate, and most of the radioactive substance in the water to be treated is removed by filtering off the aggregate. Next, as the secondary separation treatment, the water to be treated that has undergone the primary separation treatment is permeated through the granular adsorbent layer, so that the fine sludge remaining in the treated water is adsorbed and removed by the granular adsorbent. By filtering the water to be treated derived from the next treatment tank with a pre-coated spring filter, fine particles containing a radioactive substance of 1 micron size are reliably removed. Therefore, according to this treatment system, high-level decontamination of radioactive polluted water can be efficiently and stably performed at a low cost by the total amount filtration method.

  According to invention of Claim 2, in the secondary separation process of the said processing system, since the to-be-processed water performs the circulation process which passes a spring filter and a granular adsorbent layer in multiple times, in the to-be-processed water which passed the primary separation process Even fine particles of 1 micron or less containing radioactive substances that may remain can be more reliably removed.

  According to the invention of claim 3, since the circulation process of the secondary separation process is performed in a plurality of stages, fine particles containing radioactive substances of 1 micron or less that may remain in the water to be treated after the primary separation process. While being able to remove reliably, changing the kind of the granular adsorbent in the circulation treatment process of each stage makes it possible to make the circulation treatment process of each stage correspond to the removal of radioactive substances having different nuclides.

  According to the invention of claim 4, as the spring filter for the secondary separation treatment, a long coil whose outer peripheral surface is encapsulated with a fiber filter material and whose filter aid is pre-coated on the outside is used. To very fine particles in the water to be treated. In addition, since the spring filter has backwashing means by introducing compressed air, if the backwashing is performed when the filterability is reduced, the long coil and the fiber filter medium are elongated by the air pressure. The clogging is instantly resolved by the clean water and air passing through the expanded filter medium from the inside to the outside, and at the same time, the precoat layer that has accumulated sludge collapses and peels off from the fiber filter medium. By switching to the filtration direction, the dispersed filter aid is deposited on the outer peripheral surface of the fiber filter medium to regenerate the precoat layer.

  According to the invention of claim 5, since a powder mainly composed of one or both of zeolite and diatomaceous earth is used as the adsorbent for the primary separation treatment, a high adsorption effect on primary nuclides of primary polluted water such as radioactive cesium is obtained. can get.

According to the invention of claim 6, since the inorganic flocculant for the primary separation treatment is composed of an inorganic electrolyte that generates at least one of Al ³⁺ and Ca ^{2+ in} water, a high aggregation effect can be obtained at a high aggregation rate. .

  According to the invention of claim 7, since the aggregate is removed by filtration with the belt press in the primary separation process, it can be filtered and removed continuously and efficiently even if the amount of the aggregate is large.

  According to the invention of claim 8, since the powder filter adsorbent corresponding to the nuclide of the radioactive substance to be removed is included in the filter aid of the spring filter in the secondary separation treatment, the radioactive substance of the nuclide is more efficiently removed. Can be removed.

  According to the inventions of claims 9 to 11, since the pretreatment of the water to be subjected to the primary separation treatment releases extremely fine sludge captured between the hydrogen-bonded water molecules, it naturally aggregates. Such a radioactive substance that exists as extremely fine sludge also behaves as aggregated particles that are easily separated by adsorption or filtration in the subsequent primary and secondary separation processes.

It is process drawing of the processing system of radioactive contamination water concerning one embodiment of the present invention. It is a longitudinal cross-sectional view of the spring filter used for the processing system. The behavior of the main part of the spring filter is shown, (a) is a longitudinal section when the pre-coating of the filter aid is started, (b) is when pre-coating is completed, (c) is during filtration operation, and (d) is during backwashing. FIG.

  Hereinafter, an embodiment of a treatment system for radioactive contaminated water according to the present invention will be specifically described with reference to the drawings. The processing system of the present invention is characterized by performing the primary separation process and the secondary separation process. In this embodiment, the pre-processing is performed before the primary separation process, and the secondary separation process is performed in two stages before and after the circulation process. It is supposed to be performed in the process.

〔Preprocessing〕
As shown in FIG. 1, to-be-treated water W0 containing a radioactive substance in the to-be-treated water tank T is sent to the pretreatment part 1 via the pump P1, and the water molecules of the to-be-treated water W0 in this pretreatment part 1 Pre-processing for breaking hydrogen bonds between each other is performed. That is, most of the radioactive substances contained in the water to be treated W0 exist as suspended particles that are released in water, but other than that, an aggregate in which water molecules are hydrogen-bonded (generally described as a cluster, In tap water, it is taken up as an extremely fine sludge that cannot be visualized in an aggregate of 12 water molecules), and the fine sludge caught between such water molecules is treated with water by ordinary adsorption and filtration. Since it cannot be separated, it becomes an obstacle to high-level decontamination. Therefore, in this pretreatment, energy is applied to the water to be treated W0 to break up hydrogen bonds between water molecules, so that very fine sludge caught between the molecules is released, and these fine sludges become micelle law. Therefore, the radioactive material present as the fine sludge will behave as aggregated particles that are easily separated by adsorption or filtration.

  Specific means for such pretreatment is not particularly limited as long as it is a treatment means that can impart energy for dissociating hydrogen bonds between water molecules, but magnetic treatment, high-speed stirring treatment, low-concentration acidic mineral addition treatment It is recommended to employ any one or two or more of these treatments.

  In the above magnetic treatment, the water to be treated W0 is passed through a high magnetic field of 5,000 gauss or more, so that water molecules are vibrated by magnetic force to dissociate hydrogen bonds between the water molecules, thereby reducing the aggregate. Decompose. As such an apparatus for magnetic treatment of water, JP-A-9-171287, JP-A-11-138173, JP-A-2000-325962, JP-A-2002-177962, JP-A-2004-358041 are disclosed. Those disclosed in Japanese Patent Laid-Open No. 2005-185882 and the like are known.

  In the above high-speed stirring treatment, the water to be treated W0 accommodated in the stirring tank is stirred at high speed for a long time to dissociate hydrogen bonds between water molecules by the mechanical shearing force, thereby breaking down the aggregate into small pieces. Let For this treatment, a high-speed stirrer equipped with various types of stirring blades generally known as a high-speed mixer or a high-speed disperser can be used. It is desirable to apply.

  The above low concentration acidic mineral addition treatment is performed by adding a low concentration acidic mineral aqueous solution such as a low concentration mineral sulfate aqueous solution to the water to be treated W0 to dissociate hydrogen bonds between water molecules as impurities that are not visualized in water. It is intended to agglomerate the existing fine sludge. As such a low-concentration acidic mineral aqueous solution, a low-concentration (several tens to several hundred ppm) obtained by diluting a high-concentration acidic mineral water generally marketed as an acid extract of granites can be used. .

[Primary separation process]
As described above, the water to be treated W1 that has been subjected to the process of breaking hydrogen bonds between water molecules in the pretreatment unit 1 is then sent to the primary adsorption treatment tank 2 of the primary separation process, as shown in FIG. The primary adsorption treatment tank 2 is partitioned into four stirring chambers 2a to 2d from the upstream side to the downstream side by a partition wall 21, and a paddle type stirrer 22 is installed in each of the stirring chambers 2a to 2d. An adsorbent supply device 23 is disposed above the stirring chamber 2a on the most upstream side. The stirring chambers 2a and 2b and the stirring chambers 2c and 2d communicate with each other on the lower side of the partition wall 21, and the stirring chambers 2b and 2c communicate with each other on the upper side of the partition wall 21, respectively.

  The water to be treated W1 sent from the pretreatment unit 1 is first introduced into the most upstream stirring chamber 2a in a state where the stirring chambers 2a to 2d are stirred at a low speed by the stirrer 22, and this stirring is performed. In the chamber 2a, the powder adsorbent Ap introduced from the adsorbent supply device 23 is added and mixed, enters the stirring chamber 2b from the bottom as a suspension in which the powder adsorbent Ap is dispersed, and rises in the stirring chamber 2b. It overflows into the stirring chamber 2c, further descends in the stirring chamber 2c, enters the stirring chamber 2d on the most downstream side from the bottom, rises in the stirring chamber 2d, flows out from the upper portion, and is sent to the next coagulation tank 3 It is done. Then, in the process of moving in the primary adsorption treatment tank 2, most of the sludge containing radioactive substances in the water to be treated W1 is adsorbed by the powder adsorbent Ap.

  Here, as the powder adsorbent Ap, various adsorbents generally used for adsorbing sludge in wastewater, such as zeolite vermiculite, diatomaceous earth, fly ash, silica body, plant opal, sewage sludge, atomic carbon. (Sewage sludge baked in a nitrogen gas furnace), activated carbon and the like. Of these, zeolite and diatomaceous earth, in particular, have a high adsorption effect on primary nuclides of primary polluted water such as radioactive cesium. Therefore, it is recommended to use a powder mainly composed of one or both of zeolite and diatomaceous earth. In addition to these general powder adsorbents, adsorbent components suitable for each radionuclide nuclide, for example, Prussian blue having high adsorptivity to radioactive cesium, may be added.

  The agglomeration tank 3 includes a paddle type agitator 31 and a flocculant supply device 32 is disposed above. In this flocculation tank 3, the inorganic flocculant Fi thrown from the flocculant supply apparatus 32 with respect to the to-be-processed water W2 of the suspension form sent from the primary adsorption treatment tank 2 under the low speed stirring by the stirrer 31. As a result, the suspended substance composed of the powder adsorbent Ap is instantaneously aggregated to generate coarse floc. And the to-be-processed water W3 containing this coarse floc rises from the lower side of the partition wall 33 through the outlet channel 34, overflows and is led out onto the external belt press 4.

The inorganic flocculant Fi added in the agglomeration tank 3 is an inorganic electrolyte that generates polyvalent cations such as Al ³⁺ and Ca ²⁺ in the liquid, and ^neutralizes the particle surface charge that causes the particles to repel each other. Aggregation occurs by summing. Specific examples of such an inorganic flocculant Fi include polyaluminum chloride, sulfate band, lime, polyferric sulfate, ferric chloride, other polyvalent metal salts, and mixtures thereof. Various commercial products such as the trade name Super M Lock manufactured by Morino Shoji Co., Ltd. can also be used. Note that the inorganic flocculant Fi is used as the flocculant for the primary separation treatment because the organic flocculant is a polymer and the belt press 4 and the spring filter 6 for the secondary separation treatment described later are clogged early. By losing the filtration function.

  The belt press 4 has an endless belt-like upper filter cloth 4a and a lower filter cloth 4b that run synchronously in some sections via a plurality of rolls 41, and endlessly applies back pressure to the two filter cloths 4a and 4b that overlap. The filtrate tank 41 is arrange | positioned below by the high pressure belt 4c. In this belt press 4, the treated water W3 derived from the coagulation tank 3 is continuously received on the lower filter cloth 4b, and coarse flocs contained in the treated water W3 are crushed into cake C. It is sandwiched between the upper filter cloth 4b, squeezed and dehydrated, and the dehydrated cake C released from the opening of both filter cloths 4a and 4b is passed through the screw feeder 42 to the contaminant storage container 43 and flexible container (flexible container bag). The filtrate (the water to be treated W4) is stored in the lower filtrate tank 41.

  Since most of the powder adsorbent Ap added in the primary adsorption treatment tank 2 is separated as cake C by this belt press 4, sludge containing radioactive substances adsorbed on the powder adsorbent Ap is also removed. Although the radioactive substance in the filtrate collected in the filtrate tank 41 has a low concentration, the filtrate is sent to the secondary separation process through the pump P2 as the water to be treated W4 in order to perform further decontamination. .

[Secondary separation treatment]
The secondary separation process is composed of two stages of front and rear circulation processing steps, and reliably removes fine particles of 1 micron or less that may remain in the water W4 to be treated after the primary separation process. As shown in FIG. 1, both of the upstream and downstream circulation processing steps include a secondary adsorption treatment tank 5 whose interior is divided into a plurality of (five in the figure) treatment chambers 5 a to 5 e by a partition wall 51, A circulation channel Lc that recirculates the water to be treated W5 in the secondary adsorption treatment tank 5 from the treatment chamber 5e to the treatment chamber 5a by the piping outside the tank, and a spring filter 6 interposed in the circulation channel Lc. Paddle type stirrers 52 for low-speed stirring are installed in the processing chambers 5a to 5e of the adsorption processing tank 5, respectively. The space between the processing chambers 5a and 5b and the space between the processing chambers 5c and 5d of the secondary adsorption processing tank 5 is above the partition wall 51, and the space between the processing chambers 5b and 5c and the space between the processing chambers 5d and 5e are below the partition wall 51. And they communicate with each other. Further, a granular adsorbent Ag1 is formed at the bottom of the processing chambers 5b and 5c, and a granular adsorbent Ag2 is formed at the bottom of the processing chambers 5d and 5e, respectively. When moving from 5c and the processing chamber 5d to 5e, the granular adsorbent Ag1 layer and the Ag2 layer are respectively transmitted.

  Here, as the granular adsorbents Ag1 and Ag2, the same material as the powder adsorbent Ap used in the primary separation process can be used, but as a granular material having a specific gravity greater than that of water, it settles without being suspended in water. Therefore, it is necessary to be able to form a deposited layer. The granular adsorbent Ag1 and the granular adsorbent Ag2 desirably use different types of adsorbent materials in order to enhance the adsorbability with respect to a plurality of types of fine sludge SS having different properties.

  In the circulation channel Lc, recirculation pumps P3 and P4 are interposed on the upstream side of the spring filter 6 via an on-off valve V1, and an auxiliary agent is adjusted between the pumps P3 and P4 and the on-off valve V1. An auxiliary agent introduction line Lf for sending the dispersion of the filter auxiliary agent Fa from the tank 7 to the spring filter 6 is connected via an on-off valve V2. In addition, the secondary adsorption treatment tank 5 is connected to a discharge flow path Lo for discharging the water to be treated W5 from the processing chamber 5e on the most downstream side and a drain pipe line Ld for removing liquid from the bottom. Further, the secondary side of the spring filter 6 is connected to an air supply line La that feeds compressed air from the air compressor 8 via the on-off valve V3.

  In the preceding circulation treatment process, the treated water W4 that has undergone the primary separation treatment is introduced into the treatment chamber 5b of the secondary adsorption treatment tank 5 through the pump P2, and the reflux water that overflows from the upstream treatment chamber 5a is removed. The treated water W5 added passes through the granular adsorbent Ag1 layer, enters the next treatment chamber 5c, rises in the treatment chamber 5c, overflows into the treatment chamber 5d, and flows out of the treatment chamber 5d into the granular adsorbent Ag2. The layer passes through the processing chamber 5e on the most downstream side. And the to-be-processed water W5 which flowed into the processing chamber 5e of the most downstream side derives | leads-out the water quantity equivalent to the introduction part from a primary separation process from the discharge flow path Lo, and is sent to the subsequent circulation processing process. The amount of water corresponding to the reflux water flowing into 5a enters the circulation channel Lc, passes through the spring filter 6, and is returned to the processing chamber 5a. Similarly, in the subsequent circulation processing step, the water to be treated W5 is introduced into the treatment chamber 5b through the discharge channel Lo of the previous circulation treatment step, and the reflux water overflowing from the upstream treatment chamber 5a is added. After passing through the granular adsorbent Ag1 layer and the Ag2 layer while sequentially moving from the processing chamber 5b to the most downstream processing chamber 5e, the processing chamber 5e corresponds to the introduction from the previous circulation processing step. The amount of water is discharged from the discharge passage Lo, and the amount of water corresponding to the reflux water to the uppermost processing chamber 5a is directed to the circulation passage Lc.

  The circulation amount of the water to be treated W5 in these upstream and downstream circulation treatment steps can be arbitrarily set depending on the amount of water supplied by the pumps P3 and P4 interposed in the circulation flow path Lc, but the introduced water is the secondary adsorption treatment tank 5 and the spring filter 6. It is desirable to set so as to be derived through a plurality of cycles passing through. For example, when the water conveyance amount (the amount of water supplied to the secondary separation process by the pump P2) is 1000 L / min, the water supply amount of the pumps P3 and P4 interposed in the circulation channel Lc is set to 5000 L / min. The water W5 is derived through five cycles through the secondary adsorption treatment tank 5 and the spring filter 6.

  As shown in FIG. 2, the spring filter 6 includes a lid frame 62 having a spherical shape on a longitudinal cylindrical body frame 61 and hermetically joined by bolting between the outward flange portions 61 a and 62 a. A bottom frame 63 having a large diameter is welded and integrated with a lower portion of the body frame 61 to form a sealed tank. And by the partition plate 64 supported by the inward flange part 61b provided in the upper end part of the trunk | drum 61, the inside is divided into the lower wide primary side space 6a and the upper narrow secondary side space 6b, A large number of filter tubes 60 hang from the partition plate 64 into the primary space 6a. The body frame 61 has a return port 61c connected to the return pipe Lb to the auxiliary agent adjustment tank 7, and the lid frame 62 has a water supply outlet 62b connected to the downstream side of the circulation channel Lc and an air supply. A compressed air introduction port 62c connected to the pipe line La is provided on the bottom frame 63, and a treated water introduction port 63a connected to the upstream side of the circulation flow path Lc and a discharge port 63b connected to the drain pipe line Ld are provided in a projecting manner. Has been.

  Each filter cylinder 60 is formed by encapsulating the outer peripheral surface of a long coil 65 with a fiber filter material 66, and an expansion hole of the long coil 65 is provided in a holding hole 64 a that expands upward in the partition plate 64. The upper end of the diameter is locked. And the holding plate 67 provided with the through-hole 67a corresponding to the latching position of each filter cylinder 60 is screwed by the upper surface side of the partition plate 64, and filtered water passes through each through-hole 67a, and the primary side space 6a. Since the through-hole 67a is set to have a diameter smaller than that of the upper end portion of the long coil 65, the upper extraction of each filter cylinder 60 is prevented.

  This spring filter 6 is of a precoat type, and is pre-coated with a filter aid Fa on the outside of the fiber filter medium of each filter cylinder 60 in advance. In order to perform this pre-coating, as shown in FIG. 2, the filter aid Fa is introduced into the water of the auxiliary agent adjustment tank 7 from the auxiliary agent supply device 72, stirred and mixed by the stirrer 71, and the dispersion of the filter aid Fa In the state where the on-off valve V1 of the circulation passage Lc connected to the treated water introduction port 63a of the spring filter 6 is closed, the on-off valve V2 of the auxiliary agent introduction pipe Lf is opened to open the pump P3. The dispersion liquid may be introduced into the spring filter 6 by driving P4. As a result, as shown in FIG. 3A, the water in the dispersion liquid passes through the fiber filter medium 66 of each filter tube 60 and flows out to the secondary side, while the filter aid 66 is applied to the surface of the fiber filter medium 66. The agent Fa is deposited, and as shown in FIG. 3B, a precoat layer 68 of the filter aid Fa is formed on the outside of the fiber filter material 66.

  Here, as the fibrous filter medium 66, a woven or non-woven fabric of fiber material such as glass fiber, polyester fiber, polypropylene fiber or the like is used. Further, the filter aid Fa for pre-coating is not particularly limited, but it is preferable to add activated carbon, diatomaceous earth, coal, metal powder or the like to a cut material of a fiber material such as paper. In addition, if there exists what can be supplied with powder as an adsorbent corresponding to the nuclide of a radioactive substance, it will become possible to remove the radioactive substance of the nuclide more efficiently by including it in the filter aid Fa.

  Thus, after the precoat layer 68 having a required thickness is formed, the open / close valve V2 of the auxiliary agent introduction pipe line Lf is closed, and the open / close valve V1 of the circulation flow path Lc is opened to perform the secondary separation process, and the pump P3 , P4 is driven. In this secondary separation process, the water to be treated W5 sent from the treatment chamber 5e of the secondary adsorption treatment tank 5 through the circulation channel Lc flows into the primary space 6a of the spring filter 6 and is shown in FIG. As shown, the water in the water to be treated W5 permeates the precoat layer 68 and the fiber filter medium 66 of each filter cylinder 60 and flows out to the secondary side, but the fine sludge SS in the water to be treated W5 can permeate. Without being caught by the precoat layer 68 and the fiber filter material 66.

  In this secondary separation treatment, in the circulation treatment process in the previous stage, the treated water W4 in which the radioactive substance contained in the original treated water W0 has been almost removed by the primary separation treatment and has become a low concentration is targeted. In addition, after repeating the adsorption of fine sludge SS by passing the granular adsorbent Ag1 layer and Ag2 layer of the secondary adsorption treatment tank 5 and filtration removal of the fine sludge SS by the precoat spring filter 6 a plurality of times, Furthermore, similar adsorption and filtration removal are repeated a plurality of times in the subsequent circulation process. Accordingly, the water to be treated finally discharged from the discharge flow path Lo of the subsequent circulation processing step becomes extremely high decontamination water in which fine particles containing radioactive substances of 1 micron or less are reliably removed. Yes.

  As the secondary separation process continues, in the spring filter 6, the fine sludge SS gradually fills the fine gaps in the precoat layer 68 and the fiber filter material 66, and the outer side of the precoat layer 68 as shown in FIG. A deposited layer D of fine sludge SS is formed at the same time. When the filterability is lowered to some extent due to the progress of clogging of the fiber filter material 66 and the precoat layer 68, the pumps P3 and P4 of the circulation flow path Lc are stopped and the on-off valve V1 is closed, and the air supply pipe The on-off valve V3 on the path La is temporarily opened to introduce the compressed air Air into the secondary space 6b of the spring filter 6, and at the same time the on-off valve V4 (see FIG. 2) on the return pipe Lb is temporarily opened. By doing so, as shown in FIG. 3 (d), the long coil 65 and the fiber filter medium 66 of each filter cylinder 60 are extended by the air pressure, and the filter medium expanded with this is passed from the inside to the outside. The clogging is instantly eliminated by the water and air that flows, and at the same time, the precoat layer 68 and the deposited layer D that have adhered and accumulated the fine sludge SS are collapsed and peeled off from the fiber filter material 66. Note that a part of the water to be treated W5 in the primary space 6a flows out to the auxiliary agent adjustment tank 7 through the return line Lb corresponding to the compressed air Air that has flowed into the spring filter 6.

  After backwashing with the compressed air Air, the on-off valve V4 of the return line Lb is closed, and the on-off valve V2 of the auxiliary agent introduction line Lf is opened to drive the pumps P3, P4, and the auxiliary agent adjusting tank 7 If the dispersion liquid of the filter aid Fa is introduced into the spring filter 6, the filter aid Fa dispersed in the dispersion liquid and the residual water in the primary space 6 a of the fiber filter medium 66 of each filter cylinder 60 is obtained. The precoat layer 68 is regenerated by being deposited on the outer peripheral surface. Therefore, the secondary separation process can be resumed by closing the on-off valve V2 of the auxiliary agent introduction pipe line Lf and opening the on-off valve V1 of the circulation passage Lc. However, in this case, the precoat layer 68 contains the fine sludge SS filtered off in the previous treatment, and the time to clogging is shortened accordingly. Therefore, after a certain number of backwash times, the secondary side It is preferable that the entire liquid in the space 6a is discharged from the drain line Ld, and a new precoat layer 68 is formed only with the filter aid Fa in the auxiliary agent adjustment tank 7.

  As described above, in the treatment system of the present invention, the suspension material in water including the agglomerated particles in the water to be treated W1 is adsorbed by the primary separation treatment for the water to be treated W0 containing the radioactive substance. The adsorbent powder Ap is converted into a coarse aggregate precipitate by an inorganic flocculant Fi and filtered to remove most of the radioactive material in the original treated water W0. As the separation process, the treated water W4 that has undergone the primary separation process is passed through the granular adsorbent Ag1 layer and Ag2 layer of the secondary adsorption treatment tank 5 to adsorb and remove the minute sludge SS, and further, the precoated spring filter 6 minutely removes the minute sludge SS. By filtering off the sludge SS, fine particles containing a radioactive material of 1 micron size are taken into the filter aid layer of the precoat and reliably removed.

  In particular, as a secondary separation process, if a circulation process in which the water to be treated W5 passes through the granular adsorbent material Ag1 layer, the Ag2 layer and the spring filter 6 a plurality of times as in the embodiment is adopted, the treatment subject to the primary separation process. Even fine particles of 1 micron or less that may remain in water can be reliably removed. Further, in the configuration in which the circulation process of the secondary separation process is performed in a plurality of stages, fine particles of 1 micron or less can be completely removed, and the type of the granular adsorbent in each stage of the circulation process can be changed to change each stage. This circulation processing step can be made compatible with decontamination of radioactive materials having different nuclides.

  Such a treatment system can perform high-level decontamination of radioactive polluted water efficiently and stably at a low cost by using a total filtration method. For example, the current state of the system adopted at the Fukushima Daiichi Nuclear Power Station It is also very effective as a pre-process for reducing the load of ALPS and a process that can be substituted for the ALPS.

  In addition, the processing system of this invention includes the structure which abbreviate | omitted the pre-processing part 1 shown by embodiment. However, by performing the pretreatment to break the hydrogen bonds between water molecules, as described above, extremely fine sludge containing radioactive substances caught between water molecules is released and aggregates naturally. Such a radioactive substance that has existed as extremely fine sludge also behaves as aggregated particles that can be easily separated by adsorption or filtration in the subsequent primary and secondary separation processes, thereby enabling a higher degree of decontamination. Further, when the original radioactive polluted water contains coarse garbage and oil, it is desirable to incorporate a removal process of these coarse garbage and oil before introduction into the treated water tank T or before the pretreatment unit 1. .

  As the secondary separation treatment, a two-stage circulation treatment process is adopted in the embodiment, but a plurality of circulation treatment processes are performed depending on the type, treatment amount and treatment speed of the radioactive contaminated water to be treated. Various arrangement configurations including serial connection and parallel connection can be set. Moreover, although the granular adsorbent layer of the secondary separation process is a granular adsorbent Ag1 layer and an Ag2 layer deposited in the secondary adsorption treatment tank 5 in the embodiment, for example, a sealed container is filled with the granular adsorbent, It is good also as a structure which makes to-be-processed water permeate | transmit in a packed bed.

  As the spring filter 6 for the secondary separation treatment, a general configuration in which a filter aid is directly precoated on the outside of the coil spring can be adopted. However, as in the embodiment, the fiber that encloses the long coil 65 is used. In the configuration in which the filter aid Fa is pre-coated on the outside of the filter medium 66, there is an advantage that even very fine particles in the water to be treated can be surely filtered and removed. In addition, when backwashing means by introducing compressed air is employed as in the spring filter 6 of the embodiment, the expanded filter medium from the inside as the long coil 65 and the fiber filter medium 66 are extended by the air pressure. The clogging is instantly resolved by the clean water and air passing outside, and the precoat layer 68 with the fine sludge SS attached and accumulated at that time collapses and peels off from the fiber filter material. By switching to the direction, there is an advantage that the powdered material of the filter aid Fa that has been dispersed is deposited on the outer peripheral surface of the fiber filter material and the precoat layer can be easily regenerated.

  The number of fractions in the primary adsorption treatment tank 2 and the secondary adsorption treatment tank 5 and the movement path of the water to be treated are not limited to the configuration exemplified in the embodiment, so that a residence time capable of performing sufficient adsorption treatment can be secured. What is necessary is just to set suitably according to a processing amount and a processing speed. Moreover, it can change suitably also about the form and installation number of the stirrers 22 and 52. FIG. On the other hand, various filtration methods other than the illustrated belt press can be employed for filtering and removing the aggregates in the primary separation process, but the belt press can continuously and efficiently filter and remove even if the amount of aggregates is large. There are advantages. In addition, in the radioactive polluted water treatment system of the present invention, various design changes other than the embodiment can be made for the detailed configuration including the piping configuration.

DESCRIPTION OF SYMBOLS 1 Pretreatment part 2 Primary adsorption treatment tank 22 Stirrer 3 Aggregation tank 4 Belt press 5 Secondary adsorption treatment tank 5a The treatment room (upstream water introduction part) on the most upstream side
6 Spring filter 60 Filter cylinder 65 Long coil 66 Fiber filter material 68 Precoat layer Ag1, Ag2 Granular adsorbent Air Compressed air Ap Powder adsorbent Fa Filtration aid Fi Inorganic flocculant Lc Circulation channel W0-W5 Water to be treated SS Micro sludge

Claims (11)

For treated water containing radioactive substances,
The pretreated water to be treated is admixed with the adsorbent powder in the primary treatment tank and stirred and mixed, and the water to be treated derived from the primary treatment tank is aggregated by adding an inorganic flocculant, and the aggregates are removed by filtration. A primary separation process;
The treated water that has undergone the primary separation treatment is permeated through the granular adsorbent layer, and the permeated treated water is filtered through a spring filter pre-coated with a filter aid to separate and remove the fine sludge in the treated water. Secondary separation processing to
A treatment system for radioactive contaminated water characterized by applying   The secondary separation treatment is configured such that the water to be treated passes through the spring filter and the granular adsorbent layer a plurality of times by a circulation treatment that returns the filtered water from the spring filter to the treated water introduction part of the granular adsorbent layer. The radioactive contaminated water treatment system according to claim 1, wherein   The secondary separation treatment includes a plurality of circulation treatment steps each including the granular adsorbent layer and a spring filter, and the water to be treated that has passed through the previous circulation treatment step is continuously sent to the next circulation treatment step. The radioactive contamination water treatment system according to claim 2, which is configured to be configured as described above.   In the spring filter, an outer peripheral surface of a long coil is encapsulated with a fiber filter medium, and the filter aid is precoated on the outside of the fiber filter medium, and compressed air is supplied to the inside of the long coil. The treatment system for radioactive contaminated water according to any one of claims 1 to 3, further comprising backwashing means by introduction.   The treatment system for radioactive contaminated water according to any one of claims 1 to 4, wherein the adsorbent powder in the primary separation treatment is a powder mainly composed of one or both of zeolite and diatomaceous earth. The radioactive polluted water treatment system according to any one of claims 1 to 5, wherein the inorganic flocculant for the primary separation treatment comprises an inorganic electrolyte that generates at least one of Al ³⁺ and Ca ²⁺ in water.   The processing system for radioactive contaminated water according to any one of claims 1 to 6, wherein the aggregate is removed by filtration with a belt press in the primary separation process.   The processing system for radioactive polluted water according to any one of claims 1 to 7, wherein the filter aid of the spring filter includes a powder adsorbent corresponding to the nuclide of the radioactive substance to be removed.   The treatment of radioactive polluted water according to any one of claims 1 to 8, wherein a magnetic treatment for allowing the treated water to pass through a high magnetic field of 5,000 gauss or more is performed as a pretreatment of the treated water to be subjected to the primary separation treatment. system.   The pretreatment of the water to be treated for the primary separation treatment, the water to be treated contained in the stirring tank is subjected to a high-speed stirring treatment for 10 hours or more at a stirring blade rotational speed of 10,000 rotations or more. The radioactive contaminated water treatment system described in 1. The processing system of radioactive contamination water in any one of Claims 1-8 which add and mix a low concentration acidic mineral to to-be-processed water as pre-processing of the to-be-processed water provided to a primary separation process.

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