Treatment method of contaminated water containing tritium

Abstract

To provide a treatment method capable of reducing volume of a large amount of contaminated water containing tritium to a practical level.SOLUTION: A treatment method of contaminated water containing tritium is a treatment method of contaminated water containing tritium in which after dissolving non-electrolyte water-soluble carbohydrates in contaminated water containing tritium, the carbohydrates are crystallized, tritium is taken into sugars by isotope exchange between hydrogen in sugar crystals and tritium in tritium water. In the treatment method of contaminated water containing tritium, a water-absorbent polymer is placed away from the contaminated water containing tritium in a closed space, the tritium in the contaminated water containing tritium is transferred to the water-absorbent polymer by isotope exchange via water vapor.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a treatment method that enables the reduction of the volume of large amounts of contaminated water containing tritium to a practical level. [Background technology]

[0002] In the treatment of contaminated water from nuclear power plants, multi-nuclide removal equipment is capable of removing radioactive materials other than tritium. The concentration of tritium in contaminated water is within the legal limit of 6 x 10 4 There is a demand to reduce the level to below Bq / L. Here, tritium (T) exists as tritiated water (HTO or TO), which is difficult to separate from light water (HO).

[0003] Tritium separation technologies include low-temperature distillation after converting it into liquid hydrogen, and multi-stage distillation of tritiated water and light water. The latter distillation method separates tritiated water by utilizing the difference in vapor pressure between light water and tritiated water. However, the difference in vapor pressure between tritiated water and light water is small, which increases the number of theoretical plates, resulting in problems such as larger equipment and high energy consumption. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2015 / 098160 issue [Patent Document 2] JP 2017-100090 A [Patent Document 3] JP 2016-13535 A [Patent Document 4] JP 2015-112589 A

[0005] Patent Document 1 teaches that tritiated water can be concentrated by performing low-temperature distillation at 40°C or less using a distillation column packed with silica gel beads as a packing material. It also cites that when low-temperature distillation is performed, the relative volatility improves from 1.05 to 1.16 at 40°C compared to 60°C, for example, and that using silica gel beads as a packing material for the distillation column further improves the relative volatility, so that the synergistic effect of the two makes it possible to reduce the number of theoretical plates and to miniaturize the equipment for practical use.

[0006] Patent Document 2 teaches a method of electrolyzing tritium water in an electrolytic cell and separating the resulting hydrogen gas into hydrogen and tritium using a separation membrane made of a palladium alloy. Patent Document 3 discloses a method in which organic matter such as an organic acid or an organic acid alkali salt is added to contaminated water containing tritium, fine bubbles are circulated to cause a reaction in which the hydrogen at the α-position of the carboxylic acid group is replaced with tritium through the fine bubble interface, an inorganic metal salt is added to the reaction, and the water insolubility of the tritium-substituted product is increased, followed by adsorption and separation using activated carbon and zeolite. Patent Document 4 discloses a method in which contaminated water containing tritiated water is treated by an interfacial progressive freezing method to cause frozen water crystals to precipitate in layers while these are scraped off and removed, the contaminated water containing the removed frozen water crystals is supplied to an maturation tank to grow the frozen tritiated water crystals, and the contaminated water containing the grown frozen tritiated water crystals is separated into frozen tritiated water crystals and contaminated water using a solid-liquid separation device.

[0007] As mentioned above, several methods have been proposed for treating contaminated water containing tritium, but there is a problem with the high equipment and operating costs involved in treating large quantities of contaminated water with a high concentration of over 1 million Bq / L and reducing it to 60,000 Bq / L or less. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, there has been a demand for a treatment method that requires simple equipment, has low operating costs, and is capable of reducing the volume of contaminated water to a high degree. [Means for solving the problem]

[0009] The present invention is a method for treating contaminated water containing tritiated water, which comprises: causing a water-absorbent polymer to absorb tritiated water, to obtain a water-containing water-absorbent polymer; evaporating or distilling at a low temperature of 80°C or less 50% or more of the amount of absorbed water in the water-containing water-absorbent polymer, thereby concentrating the tritiated water in the water in the water, into the water-absorbent polymer, to obtain a concentrated water-containing water-absorbent polymer; and storing the concentrated water-containing water-absorbent polymer in which tritiated water has been concentrated in a container.

[0010] A second aspect of the present invention is a method for treating contaminated water containing tritiated water, comprising the steps of: causing a water-absorbent polymer to absorb tritiated water-containing contaminated water to form a water-containing water-absorbent polymer or an aqueous phase containing the water-containing water-absorbent polymer; evaporating or distilling the water in this water-containing water-absorbent polymer or aqueous phase at a low temperature of 80°C or lower to obtain a semi-solid concentrated water-containing water-absorbent polymer; and storing the semi-solid concentrated water-containing water-absorbent polymer in a container.

[0011] When the tritium-containing contaminated water is absorbed into the water-absorbent polymer to form the water-absorbent polymer, it is desirable to make the water-absorbent polymer contain a non-electrolyte water-soluble sugar, for example. It is also desirable to further subject the semi-solid concentrated water-absorbent polymer to an evaporation treatment to reduce the water concentration and the tritium concentration in the water.

[0012] The evaporation or distillation can be carried out at a temperature equal to or higher than the ambient temperature, preferably at 20 to 60° C. As the water-absorbing polymer, a polyacrylate-based polymer can be used. By absorbing 10 to 1000 times the weight of the water-absorbing polymer and evaporating or distilling off 90 to 99% of the absorbed water, a significant weight reduction can be achieved.

[0013] A third aspect of the present invention is a method for treating contaminated water containing tritiated water, which comprises dissolving non-electrolyte water-soluble carbohydrates in the contaminated water containing tritiated water in an enclosed space, and then crystallizing the carbohydrates to incorporate tritium into the carbohydrates.

[0014] A fourth aspect of the present invention is a method for treating contaminated water containing tritiated water, characterized in that a water-absorbent polymer is disposed in an enclosed space away from the contaminated water containing tritiated water, and tritium in the contaminated water containing tritiated water is transferred to the water-absorbent polymer by isotope exchange via water vapor or the like. Effect of the Invention

[0015] According to the present invention, the volume of tritium-containing contaminated water can be significantly reduced.

[0016] According to the second aspect of the present invention, by adding a water-absorbing polymer, when the water is concentrated and becomes semi-solid, the surface area increases and the evaporation rate can be improved. In addition, it is possible to promote isotope exchange with moisture in the air and promote the reduction of the amount of tritium in the tritiated water absorbed by the water-absorbing polymer. Furthermore, by adding a non-electrolyte sugar, crystallization occurs as the water is concentrated, further increasing the surface area of ​​the water-absorbing polymer, and the above effect can be further improved.

[0017] According to the third aspect of the present invention, by crystallizing a carbohydrate, tritium can be efficiently incorporated into the carbohydrate or into water of crystallization. According to the fourth aspect of the present invention, by disposing the tritiated water-containing contaminated water and the water-absorbent polymer at a distance in an enclosed space, it becomes possible to move the tritiated water to the water-absorbent polymer. [Brief description of the drawings]

[0018] [Figure 1] 1 is a graph showing the change over time in the amount of tritium in Example 4. [Diagram 2] 1 is a graph showing the change in drying speed over time in Example 4. [Diagram 3] 1 is a graph showing the change over time in the amount of tritium in Example 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will now be described. The present invention has the requirements of causing a water-absorbent polymer to absorb tritiated water-containing contaminated water to form a water-absorbent polymer, evaporating or distilling at a low temperature of 80°C or less to obtain a concentrated water-absorbent polymer by 50% or more of the water absorption amount, and storing the concentrated water-absorbent polymer in a container.

[0020] Contaminated water containing tritiated water is preferably one that contains tritiated water at or above the regulated value, but if the concentration is too high, it becomes difficult to lower the concentration of the discharged gas or distillate water to a safe level, so it is preferable that the concentration is about 100 times the regulated value or less. Therefore, if the concentration is too high, it is better to dilute it with fresh water, etc. Also, since ions such as calcium ions and magnesium ions interfere with and reduce the water absorption performance of the water-absorbent polymer, it is better to remove these interfering ions in advance. Here, it is preferable to manage the concentration of tritiated water in Bq / L, and the regulated value is 60,000 Bq / L or less for wastewater and 5 Bq / L or less for exhaust gas.

[0021] The water-absorbent polymer is preferably a polyacrylate-based polymer such as sodium polyacrylate, but is not limited thereto. However, the water-absorbent polymer is preferably one having a high maximum water absorption rate (water absorption amount g / water-absorbent polymer g), and is preferably about 20 to 1000.

[0022] There is no limitation on the method for absorbing tritium-containing contaminated water to make a water-absorbent polymer, but an impregnation method is suitable. The amount of water content varies depending on the water absorption rate of the water-absorbent polymer, but it is preferable to make it 100% or less of the maximum water absorption rate, and it is preferable to be in the range of 50 to 99%. From another perspective, it is desirable to absorb water in an amount 10 to 1000 times by weight, preferably 20 to 500 times by weight, of the water-absorbent polymer.

[0023] In order to promote evaporation, it is desirable to absorb the tritiated water-containing contaminated water into a water-absorbent polymer in the presence of a non-electrolyte water-soluble carbohydrate, thereby incorporating the carbohydrate into the water-absorbent polymer. The carbohydrate is preferably a non-electrolyte, water-soluble, and crystalline carbohydrate. In other words, it is preferably one that, when a certain concentration is reached, precipitates as crystals from the contaminated water absorbed by the water-absorbent polymer. Any carbohydrate having such properties can be used, and examples of such carbohydrate include monosaccharides such as glucose, fructose, and arabinose, and disaccharides or polysaccharides such as sucrose, lactose, starch, and xylitol. In terms of ease of availability, however, monosaccharides and disaccharides are preferred. The amount of carbohydrate to be used varies depending on the type of water-absorbing polymer and the solubility of the carbohydrate, but a range of 10 to 1000 parts by weight of a carbohydrate solution with a density of 1.18 g / ml per part by weight of the water-absorbing polymer is suitable. In any case, at least a part of the carbohydrate must be dissolved before concentrating the water-absorbent polymer and precipitate as the concentration proceeds, so an appropriate amount to be used can be calculated from this.

[0024] The water-absorbent polymer that has absorbed the tritium-containing contaminated water is then evaporated or distilled to remove 50% or more of the absorbed water. This treatment is called a drying treatment because it is a treatment to remove a part of the water in the water-absorbent polymer and dry it. Here, the drying treatment is performed at 80°C or less, preferably 60°C or less. The lower limit temperature should be 0°C or more at which water remains liquid, but if it is performed at ambient temperature or higher, cooling operation is not required. Also, if it is performed near ambient temperature, it is possible to minimize heating. From this viewpoint, it is preferably performed at 10 to 60°C, more preferably 15 to 40°C. By setting this temperature to a low temperature of 80°C or less, it is possible to increase the vapor pressure ratio P(H2O) / P(HTO). For example, P(H2O) / P(HTO) at 100°C is 760 / 739, but at 80°C it is 355 / 341, and at 20°C it is 24 / 22. In addition, since water-absorbing polymers have the property of absorbing moisture from the surrounding area when the temperature drops and as the drying process progresses, it is recommended to keep the temperature at 30°C or higher in the latter half of the drying process, although this will depend on the type of water-absorbing polymer and the humidity of the atmosphere.

[0025] Since the water-absorbing polymer itself is a compound containing a large amount of hydrogen, it is thought that a reaction will occur in which the tritium in the contaminated water replaces the hydrogen in the water-absorbing polymer.

[0026] The drying process may involve evaporating or distilling the water in the water-containing water-absorbing polymer. When evaporating, the evaporated water is preferably discharged as exhaust gas, and when distilling, it is preferably discharged as wastewater.

[0027] When drying is performed by evaporation, there is a method of slowly evaporating the wastewater while exposing it to the atmosphere at a low temperature, but when treating a large amount of wastewater, it is preferable to evaporate the wastewater while flowing a gas such as air. When evaporating the wastewater while flowing a gas in this way, the moisture in the wastewater is sufficiently diluted, making it easier to satisfy the above-mentioned regulated value. From another perspective, it is preferable to set the temperature and the amount of flowing gas so as to satisfy the above-mentioned regulated value. When performing the drying while flowing a gas, it is preferable to place the water-absorbent polymer in a perforated container or bag. In addition, as the drying progresses, the tritiated water concentration of the water in the hydrated water-absorbing polymer increases, so it is desirable to gradually lower the temperature or increase the amount of circulating gas to keep the tritiated water concentration in the exhaust gas at a certain value or less. When the drying temperature is made higher than the atmospheric temperature, it is possible to effectively utilize the relatively low-temperature waste heat generated during the operation of nuclear power plants or accident treatment. In addition, increasing the humidity of the circulating gas is effective in promoting drying, and in this case, the waste heat or exhaust gas from the nuclear power plant can be used. The drying treatment time is preferably one day or more, and preferably about 5 to 15 days, depending on the surface area of ​​the hydrated water-absorbing polymer. Furthermore, the natural drying method using sunlight has the advantage that the heating and cooling means can be greatly simplified. In this case, drying can be achieved simply by placing the water-containing water-absorbent polymer in an open-topped container or bag indoors or outdoors where there is a window that lets in sunlight, and storing it in sunlight or indoors where the temperature is raised by the greenhouse effect. This drying method requires a long processing time and certain humidity and exhaust gas control, but it can significantly reduce the drying processing costs compared to forced drying. If necessary, heated air can be used for indoor ventilation.

[0028] When the drying treatment is carried out by distillation, a device such as a distillation device or a device such as that used for the evaporation may be used. In either case, at least a part of the gas generated or discharged is cooled and distilled to become wastewater. If this wastewater does not satisfy the regulation value, it can be subjected to the treatment of the present invention again. The drying treatment should be carried out until 80% or more, preferably 90% or more, and more preferably 95 to 99% of the moisture contained in the initial hydrated water-absorbing polymer that has absorbed tritiated water-containing contaminated water is removed. If more than this amount is attempted to be removed, the concentration of tritiated water in the exhaust gas or wastewater will become high. On the other hand, if the moisture removal rate is low, the volume of the remaining hydrated water-absorbing polymer will increase, and the amount of storage will increase. It is desirable to leave moisture at about 1 to 2 times the weight of the water-absorbing polymer.

[0029] The concentrated water-absorbent polymer that has been dried and contains tritiated water in a concentrated form in the water-absorbent polymer will greatly exceed the regulated value, so it is recommended that it be stored in a container until it becomes equal to or less than the regulated value. In the present invention, the volume is significantly reduced by the drying process, and since it is a solid gel as a whole, it is easy to store. If it is burned and disposed of after a sufficient storage period calculated from the half-life has passed, the final amount of waste will also be significantly reduced. In addition, when the drying process is performed by flowing a circulating gas, not only is a high temperature or sealed device not required, but the device can be simplified, and air can be used as the circulating gas, resulting in excellent operating costs. Furthermore, the tritiated water concentration in the exhaust gas can be easily controlled by changing the temperature or the amount of circulating gas, so that safe operation is possible.

[0030] In the second aspect of the present invention, the drying treatment can be carried out in the same manner as described above, but in order to promote the isotope exchange reaction with water vapor in the air, it is advantageous to carry out the drying treatment at around room temperature. As the drying treatment progresses, the fluidity of the water-containing water-absorbent polymer or the aqueous phase containing the same gradually decreases, and the water-containing water-absorbent polymer phase becomes a semi-solid state, but in this case, the surface area can be significantly increased compared to a normal liquid aqueous solution. When the water content is less than the maximum water absorption rate of the water-absorbent polymer, the pure water phase disappears and the whole becomes a semi-solid state, and when the water content is further reduced, the fluidity decreases, and when the water content is about 1 weight times or less of the water-absorbent polymer, the water-absorbent polymer becomes almost solid, so it is preferable to carry out the drying treatment so that the water-absorbent polymer becomes a semi-solid state of about 10 to 90% of the maximum water absorption rate.

[0031] It is advantageous to dry the contaminated water even after it becomes semi-solid. In this case, the presence of the water-absorbing polymer increases the surface area, promoting evaporation even at room temperature, and increasing the isotope exchange reaction with moisture in the air, thereby reducing the tritium concentration in the contaminated water that is finally contained in the semi-solid concentrated water-absorbing polymer. When carbohydrates are present in the water-absorbent polymer or the aqueous phase containing the same, they will precipitate as crystals as drying progresses, further increasing the surface area and increasing the isotope exchange reaction upon drying.

[0032] In a third aspect of the present invention, a water-soluble carbohydrate that is a non-electrolyte is dissolved in the tritiated water-containing contaminated water, and then the carbohydrate is crystallized to incorporate and concentrate tritium in the carbohydrate, while at the same time reducing the tritiated water concentration in the tritiated water-containing contaminated water. This is presumably due to the fact that the carbohydrate and tritiated water come into contact with each other, causing isotope exchange with hydrogen in the carbohydrate, and the incorporation of tritiated water as water contained as water of crystallization in the crystallized carbohydrate. Note that, as water-soluble carbohydrates, similar incorporation is observed in arabinose, water-soluble starch, and the like in addition to glucose, but little incorporation of tritium is observed in water-insoluble carbohydrates such as cellulose.

[0033] In a fourth aspect of the present invention, a water-absorbing polymer is placed in an enclosed space away from tritiated water-containing contaminated water, and tritium in the tritiated water-containing contaminated water is transferred to the water-absorbing polymer by exchange via water vapor. This is presumably due to isotope exchange in the gas phase of water vapor evaporated in the enclosed space, and tritiated water being relatively well absorbed by the water-absorbing polymer, etc.

[0034] A specific example of operation will be described below. Example 1 The superabsorbent resin TAISAP-SK273 (manufactured by Taiwan Plastics Industry Co., Ltd.), consisting of a partially sodium salt-crosslinked acrylic acid polymer, was used as the absorbent polymer. 10 g of this was placed in a 1000 mL cylindrical container made of stainless steel with a 60 mesh opening, and allowed to absorb 1000 g of contaminated water containing 60,000 Bq / L of tritium, to produce sample S1. The sample is placed in a glass container together with the stainless steel container, and air at 30°C is passed through it for 10 days to dry it until the moisture weight is reduced to 1 / 10. The tritium in the water contained in the dried sample at this time is at least 76,400 Bq / L based on the simulation results of the vapor pressure ratio (H2O) / P(HTO), but an even higher value can be expected due to the gelling effect of the water-absorbing polymer on the tritium-containing water. Therefore, the volume of tritium-containing contaminated water can be significantly reduced. On the other hand, the simulation results showed that the maximum tritium concentration in the exhaust gas due to drying was 0.0016 Bq / cm 3 This is below the atmospheric emission standard of 0.005 Bq / cm 3 The following is true:

[0035] Example 2 Using the same sample S1 as used in Example 1, place this sample together with the stainless steel mesh container in a glass container and pass air at 50°C through it for 5 days to dry it until the moisture weight is reduced to 1 / 10. The tritium in the water contained in the dried sample is also estimated to be at least 69,700 Bq / L from the simulation results, but an even higher value can be expected due to the effect of the water-absorbing polymer. Therefore, the volume of tritium-containing contaminated water can be significantly reduced. On the other hand, the simulation results of the tritium concentration in the exhaust showed that the maximum value was 0.0044 Bq / cm 3 This satisfies the atmospheric emission standard for tritium. However, if the drying temperature exceeds 52.8°C under these conditions, the maximum tritium concentration in the exhaust gas exceeds the atmospheric emission standard value of 0.005 Bq / cm. 3 Caution is required as there is a possibility of exceeding this limit.

[0036] Example 3 Sample S1, the same as in Example 1, is placed on a stainless steel tray and left in an indoor draft for 15 days to dry until the water weight is reduced to 1 / 10. The temperature and humidity at this time are atmospheric conditions (room temperature of approximately 25°C). The simulation result of the tritium concentration in the water contained in the sample after drying is 76,500 Bq / L or more, and the volume of tritium-containing contaminated water can be significantly reduced. On the other hand, the maximum tritium concentration in the surrounding air is 0.0012 Bq / cm 3 This satisfies the atmospheric emission standards for tritium.

[0037] Example 4 Various samples were prepared using tritiated water stock solution (Perkinelmer HTO 37MBq / mL). The samples prepared were 10 mL of pure water containing approximately 0.6 kBq / mL of tritium (Sample S4A), 10 mL of pure water containing approximately 0.6 kBq / mL of tritium to which 0.1 g of water-absorbing polymer (Sanyo Chemical Industries: Sunfresh ST-500D) was added (Sample S4B), and 10 mL of glucose (Fujifilm Wako Pure Chemical Industries: special grade reagent) aqueous solution (concentration 0.18 g / mL) containing approximately 0.5 kBq / g of tritium to which 0.1 g of water-absorbing polymer was added (Sample S4C). These samples S4A, S4B, and S4C were placed in eight 20mL glass vials (diameter 2.4cm, height 4.5cm, opening diameter 1.5cm) for liquid scintillation counter measurement for the same sample. The vials containing the samples were left in a draft to evaporate naturally at room temperature and dry. Every 1 to 4 days, the weight of one of them was measured, and after adding tritium-free ultrapure water to compensate for the evaporation, 10mL of liquid scintillator (Aquasol-2) was added, and each sample was measured for 5 minutes with a liquid scintillation counter (PerkinElmer, Tri-Carb). The radioactivity of each sample was quantified by comparing it with a sample with known tritium content to determine the change in tritium content (T amount: Bq) over time.

[0038] The results are shown in Table 1 and Figures 1 and 2. There was almost no difference in the drying rate of each of the samples S4A, S4B, and S4C (Figure 2), but the rate of tritium reduction increased dramatically in sample S4C, which had been added with a water-absorbing polymer and glucose (Figure 1). In Tables 1 and 2, the sample weight (g) is the total amount of tritium-containing water, water-absorbing polymer, and glucose, and is the weight of the sample (dry residue) remaining in the vial. 。 The tritium concentration (T concentration: Bq / g) was calculated using the following formula. Since ultrapure water was added to measure the amount of tritium to compensate for evaporation, the value was converted based on the initial sample weight. In the table, T1 is listed as the tritium concentration (Bq / g). Tritium concentration (Bq / g) = Tritium amount (Bq) / sample weight (g) × initial sample weight (g) / sample weight (g) Here, if the amount of tritium (Bq) / sample weight (g) is T1 (Bq / g) and the initial sample weight (g) / sample weight (g) is k, the above formula can be expressed as follows: Tritium concentration (Bq / g) = T1 (Bq / g) × k

[0039] [Table 1]

[0040] Example 5 The following were used: 10 mL of glucose aqueous solution (concentration 0.18 g / mL) containing 0.4 kBq / g tritium (Sample S5A), 10 mL of glucose aqueous solution (concentration 0.09 g / mL) containing 0.3 kBq / mL tritium with 0.1 g of absorbent polymer (Sample S5B), 10 mL of glucose aqueous solution (concentration 0.18 g / mL) containing 0.4 kBq / mL tritium with 0.1 g of absorbent polymer (Sample S5C), 10 mL of glucose aqueous solution (concentration 0.27 g / mL) containing 0.3 kBq / mL tritium with 0.1 g of absorbent polymer (Sample S5D), and 10 mL of glucose aqueous solution (concentration 0.36 g / mL) containing 0.3 kBq / mL tritium with 0.1 g of absorbent polymer (Sample S5E). These samples were placed in eight 20 mL glass vials each in the same manner as in Example 4, and left in a draft to allow natural evaporation and drying at room temperature. Every 1 to 5 days, weights were measured and measurements were made using a liquid scintillation counter in the same manner as in Example 4.

[0041] The results are shown in Table 2 and FIG. The amount of tritium in samples S5B, S5C, S5D, and S5E, which contain glucose and a water-absorbing polymer, is significantly reduced (Figure 3).

[0042] [Table 2]

[0043] Example 6 As sample S6, 100 mL of tritiated water adjusted to a tritium concentration of 0.6 kBq / mL was heated to 98°C in a glass sealed container with a lid, and 103 g of glucose was added to create a saturated glucose solution. This was left sealed in a draft at room temperature (10 to 20°C) for about one month. It was confirmed that a sufficient amount of glucose crystals had formed in the sealed glass container. 0.5 mL (0.955 g) of the solution and 1.45 g of the crystals were taken. 10 mL of liquid scintillator was added to the solution, and 10 mL of liquid scintillator was added to the crystals, which were dissolved in 5 mL of pure water not containing tritium, and then the crystals were measured using a liquid scintillation counter. The tritium concentration (Bq / g) of the glucose saturated solution containing tritium was 131 Bq / g in the solution and 249 Bq / g in the crystal, and the tritium concentration ratio (crystal / solution) was 1.90. The tritium concentration in the glucose crystal was 1.9 times higher than in the solution, which is thought to be due to preferential isotope exchange between the hydrogen atoms in the glucose crystal and the tritium atoms in the HTO.

[0044] Example 7 0.5 g of water-absorbing polymer was added to 50 g of tritium-free pure water and solidified, and the mixture was placed in a glass petri dish and used as sample S7. A plastic beaker containing sample S7 and 50 g of tritium-containing water with a tritium concentration adjusted to 1.44 kBq / g was placed in a desiccator container from which the desiccant had been removed, and the desiccator container was sealed and left to stand. After 14, 21 and 42 days had passed, the desiccator was opened and a portion (approximately 0.5 to 1.2 g) was taken from the top of sample S7, 10 mL of liquid scintillator was added, and the result was measured using a liquid scintillation counter. The results are shown in Table 3. The tritium concentration (T concentration: kBq / g) in sample S7 increased over time, and after 42 days, it reached approximately 28% of the tritium concentration in the original tritium-containing water. This suggests that by using a water-absorbing polymer in an enclosed space, tritium could be transferred without contact through isotope exchange via water vapor.

[0045] [Table 3]

Claims

1. A method for treating contaminated water containing tritiated water, comprising dissolving a non-electrolyte water-soluble carbohydrate in the contaminated water containing tritiated water, crystallizing the carbohydrate, and incorporating tritium into the carbohydrate through isotope exchange between hydrogen in the carbohydrate crystals and tritium in the tritiated water.

2. A method for treating tritiated water-containing contaminated water, comprising: arranging a water-absorbent polymer away from the tritiated water-containing contaminated water in an enclosed space; and transferring tritium in the tritiated water-containing contaminated water to the water-absorbent polymer by isotope exchange via water vapor.

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