Evaporating / drying device and evaporating / drying method

Abstract

Provided are an evaporating / drying device and an evaporating / drying method in which scattering of a solution in which a radioactive substance is dissolved is suppressed and the discharge amount of a gas containing the radioactive substance is small. An evaporating / drying fixation device (100) according to the present invention comprises: an evaporating / drying container (101) that holds a solution (207) in which a radioactive substance is dissolved, and evaporates and dries the solution; a heating device (102) that heats the evaporating / drying container (101); and a gas supply device (103) that supplies a gas to the evaporating / drying container (101). The heating device (102) comprises a heating means (110) that heats the lower surface or a position below the evaporating / drying container (101), and a temperature detection means (111) that detects the temperature at a prescribed position of the evaporating / drying container (101). The temperature detection means (111) detects the temperature of the lower surface or at the position below the evaporating / drying container (101).

Description

Evaporation to dryness apparatus and evaporation to dryness method

[0001] The present invention relates to an apparatus for evaporating and drying a solution containing a radioactive substance, and a method for evaporating and drying the solution using the apparatus.

[0002] Radioactive substances are used as radiopharmaceuticals that use radiation from radioactive isotopes. They are administered into the body and used to examine the condition of organs by capturing radiation images, or in treatments to kill cancer cells by injection or oral administration.

[0003] On the other hand, obtaining radiopharmaceuticals requires a separation and purification process to separate the desired radioactive material and remove impurities from radioactive materials produced by neutron irradiation in a nuclear reactor. This separation and purification process involves repeatedly changing the dissolving solution and adsorbing and eluting the material onto a resin. Therefore, an evaporation and drying process is essential, in which the solution containing the radioactive material is heated to evaporate the solvent and precipitate the radioactive material (solid). Various studies have been conducted on evaporation and drying devices and evaporation and drying methods using such devices for solutions containing substances, not just radioactive materials.

[0004] For example, Patent Document 1 describes that a recovery vial containing an acidic organic solvent, in which zirconium ions are dissolved and which has a boiling point lower than that of water and into which zirconium has eluted, is heated by a heater, and the contained recovery effluent is heated. Patent Document 1 also describes an evaporation to dryness step in which, while reducing the pressure inside the recovery vial, a gas such as an inert gas is supplied from a gas supply unit into the recovery vial, and stirring is performed by bubbling, thereby shortening the time required for evaporation to dryness.

[0005] JP 2020-169358 A (for example, paragraph 0039)

[0006] To complete the evaporation and drying of a solution containing a substance, the solvent must be evaporated to the very end. In evaporation and drying methods that involve agitating the solution by bubbling or turning the solution into mist, the specific surface area of ​​the liquid is increased by turning the liquid into droplets, allowing the applied heat to be transmitted more evenly. However, while these methods can efficiently evaporate and dry, they have the problem of the solution containing dissolved radioactive materials scattering due to the bubbling or misting of the solution.

[0007] Furthermore, in the evaporation to dryness method under high temperature and reduced pressure, evaporation to dryness can be carried out efficiently at high temperatures, but there is a possibility that the solution containing dissolved radioactive materials will splash due to overheating. Conversely, in the evaporation to dryness method at a temperature below the boiling point, evaporation takes time, which causes the problem of increased emissions of gas containing radioactive materials.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an evaporation to dryness apparatus and an evaporation to dryness method that suppress the scattering of a solution in which a radioactive substance is dissolved and that emits a small amount of gas containing the radioactive substance.

[0009] The evaporative drying apparatus according to the present invention, which solves the above-mentioned problems, comprises an evaporative drying container for holding a solution in which a radioactive substance is dissolved and evaporating it to dryness, a heating device for heating the evaporative drying container, and a gas supply device for supplying gas to the evaporative drying container, wherein the evaporative drying container has a sealed structure that blocks it from the outside air and comprises at least one gas supply hole through which gas can be supplied and at least one gas discharge hole through which gas can be discharged, the heating device comprises heating means for heating the underside of the evaporative drying container or a position below it, temperature detection means for detecting the temperature at a specified position on the evaporative drying container, and heating control means for controlling the heating means based on the detection value of the temperature detection means, the gas supply device comprises gas supply amount control means for controlling the amount of gas supplied to the gas supply hole, the gas supply hole and the gas discharge hole are located on the top surface of the evaporative drying container or at a position above it, and the temperature detection means detects the temperature at the underside of the evaporative drying container or a position below it.

[0010] The present invention can provide an evaporation to dryness apparatus and an evaporation to dryness method that suppresses scattering of a solution in which a radioactive substance is dissolved and that emits a small amount of gas containing a radioactive substance.

[0011] FIG. 1 is a schematic diagram of an evaporative drying apparatus 100 according to a first embodiment. FIG. 2 is a perspective view of an evaporative drying container 101 and the periphery of the evaporative drying container 101 in the first embodiment. FIG. 3 is a side view of the evaporative drying container 101 and the periphery of the evaporative drying container 101 in the first embodiment. FIG. 4 is a perspective view of an evaporative drying container 101 and the periphery of the evaporative drying container 101 in a second embodiment. FIG. 5 is a side view of an evaporative drying container 101 and the periphery of the evaporative drying container 101 in the second embodiment. FIG. 6 is a schematic diagram of an evaporative drying apparatus 400 according to a third embodiment. FIG. 7 is a graph showing an example of the evaporation to dryness state versus heating time when the flow rate of the supply gas is constant in the evaporative drying apparatus 400 according to the third embodiment, showing the relationship between the amount of residual liquid (Arb.) (arbitrary unit) versus heating time (min) and the detected value (Arb.) of the temperature detection means 111. This is a graph showing an example of the evaporation to dryness state versus heating time when the flow rate of the supply gas is constant in the evaporation to dryness apparatus 400 of the third embodiment, and shows the relationship between the heating output value (%) of the heating means 110 and the detection value (Arb.) of the temperature detection means 111 versus the heating time (min).

[0012] Hereinafter, an evaporation to dryness apparatus and an evaporation to dryness method according to an embodiment of the present invention will be described with reference to the drawings as appropriate. Note that common components in the following description and drawings may be assigned the same reference numerals, and duplicated descriptions may be omitted.

[0013] First Embodiment An evaporation to dryness apparatus according to a first embodiment of the present invention and an evaporation to dryness method according to a first embodiment of the present invention will be described with reference to FIGS. 1, 2A, and 2B.

[0014] (Evaporation to dryness apparatus) Fig. 1 is a schematic diagram of an evaporator to dryness apparatus 100 according to the first embodiment. Fig. 2A is a perspective view of an evaporator to dryness container 101 and the periphery of the evaporator to dryness container 101 in the first embodiment. Fig. 2B is a side view of the evaporator to dryness container 101 and the periphery of the evaporator to dryness container 101 in the first embodiment.

[0015] The evaporative dryness apparatus 100 according to the first embodiment heats a solution 207 in which a radioactive substance is dissolved, thereby precipitating the radioactive substance. As shown in FIG. 1 , the evaporative dryness apparatus 100 according to the first embodiment includes an evaporative dryness container 101, a heating device 102, and a gas supply device 103.

[0016] 2A and 2B , the evaporating and drying container 101 is a cylindrical body with a bottom that holds a solution 207 in which a radioactive substance is dissolved and evaporates and drys the solution. The evaporating and drying container 101 includes at least one gas supply hole 104 that can supply gas, at least one gas discharge hole 105 that can discharge gas, and a liquid supply and discharge hole 106. The evaporating and drying container 101 is connected to a gas supply pipe 107, a gas discharge pipe 108, and a liquid supply and discharge pipe 109. Specifically, the gas supply hole 104 is connected to the gas supply pipe 107. The gas discharge hole 105 is connected to the gas discharge pipe 108. The liquid supply and discharge hole 106 is connected to the liquid supply and discharge pipe 109.

[0017] The heating device 102 heats the evaporator / drying container 101. The heating device 102 includes a heating means 110, a temperature detection means 111, and a heating control means 112. The gas supply device 103 supplies gas to the evaporator / drying container 101. The gas supply device 103 includes a gas supply amount control means 113, a gas supply means 114, and a connection part 115 that connects the gas supply amount control means 113 and the gas supply means 114. The gas supply means 114 and the gas supply pipe 107 are connected by a joint or the like not shown in FIG. 1 .

[0018] As shown in Figures 2A and 2B, the evaporator / drying vessel 101 is fixed to a fixing base 201. The evaporator / drying vessel 101 has a sealed structure that is isolated from the outside air by connecting piping joints 202 that can isolate the vessel from the outside air when no piping is connected to the gas supply hole 104, the gas discharge hole 105, and the liquid supply / discharge hole 106. The bottom of the evaporator / drying vessel 101 has a roughly cone-shaped shape that deepens toward the center. This shape allows the solution 207 to collect in the center as evaporation progresses. This shape is also useful when stopping the evaporation / drying process midway to concentrate the solution 207 with dissolved radioactive materials to a desired concentration.

[0019] The gas supply hole 104, the gas discharge hole 105, and the liquid supply and discharge hole 106 are arranged on the upper surface or at a position approximately above the evaporation and drying container 101. The gas supply hole 104 and the gas supply pipe 107 are connected by a pipe joint 202, and a supply gas 203 supplied from a gas supply device 103 is supplied to the evaporation and drying container 101.

[0020] Meanwhile, the gas discharge hole 105 and the gas discharge pipe 108 are connected by a pipe joint 202, and the discharged gas 204 is discharged from the evaporation and drying container 101. Note that, in order to recover the solvent in the discharged gas 204 or the radioactive material mixed in the discharged gas 204, one or more heat exchangers or an exhaust device may be provided downstream of the gas discharge pipe 108, or one or more heat exchangers and an exhaust device may be provided in series. Also, a vacuum pump may be used instead of the exhaust device.

[0021] The liquid supply and discharge hole 106 and the liquid supply and discharge pipe 109 are connected by a pipe joint 202. Furthermore, a liquid supply and discharge pipe 205 is connected to the end opposite the liquid supply and discharge hole 106, i.e., the end not connected to the liquid supply and discharge pipe 109. The evaporating vessel 101 has a pipe fixing guide 206 extending downward near the center in a plan view. By providing the pipe fixing guide 206, the end of the liquid supply and discharge pipe 205 not connected to the liquid supply and discharge hole 106 is positioned near the center in a plan view within the evaporating vessel 101. Specifically, the open end of this end faces the deepest position of the bottom of the generally cone-shaped evaporating vessel 101, and is positioned close to this deepest position. This prevents the solution 207, in which radioactive material is dissolved, from splashing onto the wall of the evaporating vessel 101 when the solution 207 is supplied to the evaporating vessel 101.

[0022] The evaporation and drying container 101 can also be used as a container for preparing a solution when performing solvent substitution. In this case, even when supplying new solvent after evaporation and drying, splashing of the solution 207 containing dissolved radioactive materials onto the wall surface of the evaporation and drying container 101 can be suppressed. In this case, by repeatedly supplying and discharging a very small amount of solvent, the solution 207 is stirred, which can promote dissolution of the radioactive materials into the solvent. Furthermore, by stopping the evaporation and drying process midway, the solution 207 containing dissolved radioactive materials can be concentrated to a desired concentration. At this time, the small amount of concentrated solution 207 collects in the center, making it easy to discharge the solution 207.

[0023] On the other hand, the end of the liquid supply / discharge pipe 109 that is not connected to the pipe joint 202 can be connected to a column filled with resin for separating desired radioactive substances or removing impurities. Also, this end can be connected to a container storing a solution 207 in which radioactive substances are dissolved, a container storing the solution 207 discharged from the resin-filled column, or a container storing a solvent.

[0024] The heating means 110 is disposed at a position below or on the underside of the evaporating and drying container 101 and heats the evaporating and drying container 101. The temperature detection means 111 detects the temperature at a predetermined position in the evaporating and drying container 101. Specifically, the temperature detection means 111 performs temperature measurement 117 at a position (predetermined position) below or on the underside of the evaporating and drying container 101 that is close to the solution 207 in which the radioactive substance is dissolved, acquires the temperature information, and detects the temperature of the evaporating and drying container 101. Ideally, the temperature detection means 111 would detect the temperature of the solution 207 in which the radioactive substance is dissolved itself. However, the temperature detection means 111 is preferably used to detect the temperature of the evaporating and drying container 101 because: the radioactive substance in the solution 207 may contaminate the temperature detection means 111, increasing the amount of radioactive contaminants; solids after evaporation may adhere to the temperature detection means 111, making it difficult to measure the temperature accurately; and the liquid level changes as the evaporation and drying progresses, making it difficult to measure the temperature accurately.

[0025] In this embodiment, it is preferable to increase the ratio of the bottom area of ​​the evaporator / drying container 101 to the volume of the solution 207 in which the radioactive substance is dissolved. That is, it is preferable to increase the bottom area of ​​the evaporator / drying container 101 and decrease the height of the solution 207 in which the radioactive substance is dissolved. In this way, temperature unevenness in the solution 207 is reduced by thermal convection, and the solvent evaporates efficiently. As a result, the generation of bubbles (boiling) due to overheating is suppressed, and scattering of the solution 207 in which the radioactive substance is dissolved onto the wall surface of the evaporator / drying container 101 can be suppressed. Furthermore, since the temperature unevenness is reduced, the evaporation time is shortened, and the amount of gas containing the radioactive substance emitted is reduced.

[0026] As the material for the evaporation and drying container 101, the material for the gas supply pipe 107, the gas discharge pipe 108, the liquid supply and discharge pipe 109, the liquid supply and discharge pipe 205, the material for the connecting part 115, the pipe joint 202, and the material for joints (not shown), any appropriate material can be used depending on the type of fluid, as long as it does not have an adverse effect on the supply gas 203, the discharge gas 204, and the solution 207 in which the radioactive material is dissolved, and is unlikely to be deteriorated by these. These materials may be the same or different, and can be selected appropriately depending on processability, flexibility, etc.

[0027] The material of the evaporator / drying container 101 can be appropriately selected depending on the type of solvent of the solution 207 containing dissolved radioactive materials and the heat resistance temperature of the material, since it is heated by the heating means 110. Specific examples of the material for the evaporator / drying container 101 include glass, such as quartz glass, soda glass, lead glass, and borosilicate glass, as well as fluorine-based resins, such as PE (polyethylene), PP (polypropylene), PEEK (polyether ether ketone), PC (polycarbonate), PTFE (polytetrafluoroethylene), and PFA (perfluoroalkoxyalkane). Furthermore, to improve corrosion resistance and chemical resistance, a lining made of glass or an oxide film formed by the oxidation of silicon may be formed on the surface of the evaporator / drying container 101. By using a transparent or nearly transparent material for the portion filled with the solution 207 containing dissolved radioactive materials, the evaporation and drying process within the evaporator / drying container 101 can be visually observed.

[0028] The materials of the gas supply pipe 107, the connecting part 115, and the joints (not shown) can be appropriately selected depending on the heat resistance temperature of the materials because they are not heated by the heating means 110. The materials of the gas discharge pipe 108, the liquid supply / discharge pipe 109, the liquid supply / discharge pipe 205, and the pipe joint 202 can be appropriately selected depending on the type of solvent of the solution 207 in which the radioactive material is dissolved and the heat resistance temperature of the materials. Specific examples of materials that can be used for the gas supply pipe 107, the connecting part 115, the joints (not shown), the gas discharge pipe 108, the liquid supply / discharge pipe 109, and the liquid supply / discharge pipe 205 include PE, PP, PEEK, and fluororesins such as PTFE and PFA.

[0029] The heating means 110 may be a plate heater such as a mica heater, a polyimide heater, or a silicone rubber heater, or may be an appropriate device such as a Peltier unit, a mantle heater, a heat exchanger using a heat medium, or a thermostatic bath using a heat medium. The temperature detection means 111 may be any of various thermocouples, platinum resistance thermometers, thermistors, etc.

[0030] The heating control means 112 controls the heating means 110 based on the detected value (temperature detection value 118) of the temperature detection means 111. The heating control means 112 controls the heating means 110 to perform heating (control) 116 of the evaporation / dryness container 101. The heating control means 112 is only required to compare the temperature detection value (observation quantity) 118 by the temperature detection means 111 with the temperature set value and control the heating means 110 in accordance with the deviation, and examples of the control method include continuous control using PID control and ON-OFF control.

[0031] The gas supply amount control means 113 controls the amount of gas supplied to the gas supply hole 104. Examples of the gas supply amount control means 113 include a gas flow meter and a mass flow meter. Examples of the gas supply means 114 include a gas cylinder and a vaporization supply device. The gas supply means 114 can be appropriately selected from means that can supply a gas that does not adversely affect the solution 207 in which the radioactive material is dissolved, such as an inert gas such as nitrogen gas or argon gas, or dry air.

[0032] (Evaporation to dryness method) Next, an evaporation to dryness method using the evaporation to dryness apparatus 100 according to the first embodiment will be described. First, a solution 207 in which a radioactive substance is dissolved is supplied from the liquid supply and discharge pipe 109, through the pipe joint 202, the liquid supply and discharge hole 106, and the liquid supply and discharge pipe 205, into the evaporation to dryness container 101. Note that this solution 207 in which a radioactive substance is dissolved can also be placed in the evaporation to dryness container 101 in advance, depending on the situation.

[0033] The supply of the supply gas 203 from the gas supply device 103 is started. The temperature setting value of the heating device 102 is set to a predetermined temperature, and heating control is started so that the temperature measured by the temperature detection means 111 becomes equal to the temperature setting value. The solvent evaporates according to the saturated vapor pressure of the solvent at the temperature of the supply gas 203, and evaporation progresses. When the temperature detection value 118 of the temperature detection means 111 reaches the temperature setting value, the temperature of the solution 207 in which the radioactive material is dissolved becomes almost constant, and evaporation progresses stably. When evaporation is complete, there is no solvent to be heated, and the supply gas 203 is heated. Because heating is performed in a closed system, the temperature does not decrease, and a state is reached in which heating is no longer necessary. Because the temperature is maintained even without heating, the heating output value 119 of the heating means 110 drops sharply. In this state, evaporation to dryness of the solution 207 in which the radioactive material is dissolved is completed, and precipitation of the radioactive material is also completed.

[0034] The supply gas 203 may be any gas that does not adversely affect the solution 207 containing dissolved radioactive material, and examples thereof include inert gases such as nitrogen gas and argon gas, and dry air. The temperature setting value can be appropriately set depending on the types of the evaporator / drying vessel 101 and the heating device 102, so that the solution 207 containing dissolved radioactive material does not generate bubbles due to overheating (does not boil) and efficiently evaporates. If the temperature setting value is low, bubbles will not be generated due to overheating, but the heating time will be long, which may increase the amount of gas containing radioactive material emitted. On the other hand, if the temperature setting value is too high, bubbles will be generated due to overheating, which may cause the solution 207 containing dissolved radioactive material to splash or lead to thermal denaturation of the radioactive material.

[0035] Therefore, by controlling the solution temperature to a temperature that does not boil and is as high as possible, scattering of the solution 207 in which the radioactive material is dissolved is suppressed and the amount of gas containing the radioactive material emitted is reduced. Specifically, it is desirable to control the stable solution temperature during continuous heating to be several degrees Celsius to 10 degrees Celsius lower than the boiling point, more specifically, 1 degree Celsius to 10 degrees Celsius lower.

[0036] As described above, the evaporative to dryness apparatus 100 according to the first embodiment of the present invention and the evaporative to dryness method using the evaporative to dryness apparatus 100 according to the first embodiment of the present invention suppress scattering of the solution 207 in which radioactive substances are dissolved. In addition, the amount of gas containing radioactive substances emitted is reduced.

[0037] Second Embodiment An evaporative dryness apparatus 100 according to a second embodiment of the present invention and an evaporative dryness method using the evaporative dryness apparatus 100 according to the second embodiment of the present invention will be described with reference to Figures 3A and 3B and 1. The following description will focus on the differences between the second embodiment and the first embodiment.

[0038] (Evaporation to dryness apparatus) Fig. 3A is a perspective view of the evaporator to dryness container 101 and the periphery thereof in the second embodiment. Fig. 3B is a side view of the evaporator to dryness container 101 and the periphery thereof in the second embodiment.

[0039] As shown in Figures 3A and 3B, the evaporative drying apparatus 100 according to the second embodiment differs from the evaporative drying apparatus 100 according to the first embodiment in that it further includes a heat shield plate 301, which is a wall-shaped member, surrounding the side surface of the evaporative drying container 101.

[0040] The heat shield 301 makes the evaporator / drying container 101 less susceptible to the influence of the outside air temperature. Furthermore, when the heat shield 301 is provided, the temperature measured by the temperature detection means 111 reaches the set temperature value more quickly. Furthermore, the heat shield 301 also serves to keep the temperature of the evaporator / drying container 101 more constant. Furthermore, by providing an air layer between the evaporator / drying container 101 and the heat shield 301, the air layer acts as an insulating layer, making it possible to keep the temperature of the evaporator / drying container 101 more constant.

[0041] The material of the heat shield plate 301 can be appropriately selected depending on the heat resistance temperature of the material, since it is heated by the heating means 110. Specific examples of the material of the heat shield plate 301 include metals such as stainless steel, aluminum, and aluminum alloys, and resins such as PE, PP, and PET (polyethylene terephthalate).

[0042] (Evaporation to Dryness Method) Using the evaporative drying apparatus 100 according to the second embodiment described above, the solution 207 having a radioactive substance dissolved therein can be evaporated to dryness, and the radioactive substance can be precipitated, in the same manner as in the evaporation to dryness method using the evaporative drying apparatus 100 according to the first embodiment. In the second embodiment, the heat shield 301 can keep the temperature of the evaporative drying container 101 more constant. Therefore, in the second embodiment, temperature unevenness of the solution 207 is reduced, and the solvent can be evaporated efficiently. As a result, the generation of bubbles due to overheating is suppressed, and the solution 207 having a radioactive substance dissolved therein is prevented from splashing onto the wall surface of the evaporative drying container 101. Furthermore, the reduced temperature unevenness shortens the evaporation time, and reduces the amount of gas containing the radioactive substance emitted.

[0043] As described above, the evaporative dryness apparatus 100 according to the second embodiment of the present invention and the evaporative dryness method using the evaporative dryness apparatus 100 according to the second embodiment of the present invention suppress scattering of the solution 207 in which radioactive materials are dissolved. In addition, the amount of gas containing radioactive materials emitted is reduced.

[0044] Third Embodiment An evaporative to dryness apparatus 400 according to a third embodiment of the present invention and an evaporative to dryness method using the evaporative to dryness apparatus 400 according to the third embodiment of the present invention will be described with reference to Fig. 4. The following description will focus on the differences between the third embodiment and the first and second embodiments.

[0045] (Evaporation to dryness apparatus) Fig. 4 is a schematic diagram of an evaporative to dryness apparatus 400 according to a third embodiment. As shown in Fig. 4, the evaporative to dryness apparatus 400 according to the third embodiment differs from the evaporative to dryness apparatus 100 according to the first and second embodiments in that a primary heat exchanger 401, a secondary heat exchanger 402, and an exhaust device 403 are provided downstream of the gas discharge pipe 108.

[0046] The primary heat exchanger 401 is connected to the gas discharge pipe 108 via a joint (not shown). The secondary heat exchanger 402 is connected to the primary heat exchanger 401 via a first gas discharge pipe 404. The first gas discharge pipe 404 is connected to the primary heat exchanger 401 and the secondary heat exchanger 402 via joints (not shown). The exhaust device 403 is connected to the secondary heat exchanger 402 via a second gas discharge pipe 405. The second gas discharge pipe 405 is connected to the secondary heat exchanger 402 and the exhaust device 403 via joints (not shown).

[0047] The materials of the first gas discharge pipe 404 and the second gas discharge pipe 405 can be appropriately selected depending on the type of solution 207 in which the radioactive material is dissolved and the heat resistance temperature of the material, since they are heated by the gas containing the radioactive material heated by the heating means 110 and cooled by the heat exchanger. Specifically, the materials of the first gas discharge pipe 404 and the second gas discharge pipe 405 can be metals such as stainless steel, or fluororesins such as PE, PP, PEEK, PTFE, and PFA.

[0048] The materials for the primary heat exchanger 401 and the secondary heat exchanger 402 can be appropriately selected depending on the type of solution 207 in which the radioactive material is dissolved and the heat resistance temperature of the material. Specifically, the materials for the primary heat exchanger 401 and the secondary heat exchanger 402 can be metals such as stainless steel, or fluororesins such as PE, PP, PTFE, and PFA. Furthermore, to improve corrosion resistance, chemical resistance, and the like, a lining made of glass or an oxide film formed by oxidizing silicon may be formed on the surfaces of the primary heat exchanger 401 and the secondary heat exchanger 402, respectively. Using a transparent or nearly transparent material allows visual observation of the liquefied solvent being collected in the primary heat exchanger 401 and the secondary heat exchanger 402.

[0049] Examples of the primary heat exchanger 401 and the secondary heat exchanger 402 include a heat exchange trap and a trap bottle. The exhaust device 403 may be equipped with a scrubber, an exhaust gas cleaning device, an exhaust gas treatment device, or the like, depending on the type of the solution 207 in which the radioactive material is dissolved.

[0050] (Evaporation to Dryness Method) In the evaporator to dryness 400 according to the third embodiment, similarly to the evaporation to dryness method using the evaporator to dryness 100 according to the first or second embodiment, the solution 207 in which the radioactive substance is dissolved can be evaporated to dryness, and the radioactive substance can be precipitated.

[0051] During and after evaporation of the solution 207 to dryness, the primary heat exchanger 401 receives the exhaust gas 204 via the gas exhaust pipe 108. The primary heat exchanger 401 liquefies the vaporized solvent in the exhaust gas 204 and also recovers the radioactive material contained in a very small amount together with the solvent.

[0052] Next, the secondary heat exchanger 402 receives the gas that has passed through the first gas discharge pipe 404, liquefies the vaporized solvent that was not liquefied in the primary heat exchanger, and recovers any radioactive material that may be present in trace amounts together with the solvent, thereby reducing the amount of gas containing radioactive material that is discharged.

[0053] Next, the exhaust device 403 removes gases and particles contained in the gas discharged from the secondary heat exchanger 402 , purifies the gas, and discharges it outside the evaporation-to-dryness device 400 .

[0054] Fig. 5A is a graph showing an example of the evaporation to dryness state versus heating time when the flow rate of the supply gas is constant in the evaporative to dryness apparatus 400 according to the third embodiment, showing the relationship between the residual liquid amount (Arb.) (arbitrary unit) versus heating time (min) and the detected value (Arb.) of the temperature detection means 111. Fig. 5B is a graph showing an example of the evaporation to dryness state versus heating time when the flow rate of the supply gas is constant in the evaporative to dryness apparatus 400 according to the third embodiment, showing the relationship between the heating output value (%) of the heating means 110 versus heating time (min) and the detected value (Arb.) of the temperature detection means 111.

[0055] As shown in FIG. 5A, the amount of residual liquid began to decrease as soon as heating control by the heating device 102 was initiated. The detected value of the temperature detection means 111 increased, and the rate of decrease in the amount of residual liquid became steeper after 10 minutes of heating had passed and the set temperature was reached. After 25 minutes of heating, when the amount of residual liquid reached zero and evaporation was complete, the detected value of the temperature detection means 111 tended to become unstable. Meanwhile, as shown in FIG. 5B, the heating output value of the heating means 110 reached its maximum as soon as heating control by the heating device 102 was initiated. Thereafter, the heating output value of the heating means 110 decreased slightly just before the set temperature was reached, and then maintained a constant value, but then suddenly decreased to zero just before evaporation was complete.

[0056] Therefore, the heating control means 112 can determine the temperature setting value of the temperature detection means 111 that will minimize the heating time by detecting in advance the instability of the detection value of the temperature detection means 111 and the sudden drop in the heating output value of the heating means 110 during the evaporation and drying of the solution 207 in which the radioactive material is dissolved. In this way, the evaporation and drying apparatus 400 can minimize the amount of gas emitted that contains the radioactive material.

[0057] Furthermore, the heating control means 112 can detect complete evaporation of the solution 207 in the evaporator / dryer container 101 using at least one of the detection value of the temperature detection means 111 and the heating output value of the heating means 110. When the heating control means 112 detects complete evaporation, it terminates heating. In this manner, the evaporator / dryer device 400 can reduce or prevent thermal denaturation of the radioactive material while minimizing the amount of gas emitted containing the radioactive material. Note that while the solution 207 remains before complete evaporation, the temperature remains almost constant due to the latent heat of evaporation of the solution 207. However, the temperature rises upon complete evaporation. Therefore, complete evaporation can be determined by a change in the detection value of the temperature detection means 111. Furthermore, since the heating output value of the heating means 110 also changes, complete evaporation can also be determined by a change in the heating output value.

[0058] 5A and 5B, the optimum value of the flow rate (amount of gas delivered) of the supply gas 203 can be found as follows. Assuming that the evaporation and drying vessel 101 is not an enclosed space because gas is constantly being supplied and does not follow gas-liquid equilibrium, it is believed that Formula 1 generally holds true based on Boyle's law. (Formula 1) Saturated vapor pressure of solvent at gas temperature × amount of exhaust gas (L / min) ≈ atmospheric pressure at gas temperature × volumetric rate of evaporated solvent (L / min)

[0059] By modifying Equation 1, Equation 2 is obtained. (Equation 2) Amount of exhaust gas (L / min) ≈ Volume rate of vaporized solvent (L / min) × (Atmospheric pressure at gas temperature / Saturated vapor pressure of solvent at gas temperature)

[0060] From Equation 2, it is possible to minimize the amount of gas containing radioactive materials emitted by controlling the amount of gas sent to the evaporation and drying vessel 101 so that it becomes approximately the same as the flow rate (exhaust volume) of the exhaust gas 204 calculated from Equation 2. Specifically, it is desirable to control the amount of gas sent to the evaporation and drying vessel 101 to within ±10 to 20% of the flow rate of the exhaust gas 204 calculated from Equation 2.

[0061] As described above, the evaporative to dryness apparatus 400 according to the third embodiment of the present invention and the evaporative to dryness method using the evaporative to dryness apparatus 400 according to the third embodiment of the present invention suppress scattering of the solution 207 in which radioactive substances are dissolved. In addition, the amount of gas containing radioactive substances emitted is reduced.

[0062] The evaporation-to-dryness apparatus and evaporation-to-dryness method according to the present invention have been described in detail above using embodiments. However, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0063] REFERENCE SIGNS LIST 100 Evaporation to dryness device 101 Evaporation to dryness container 102 Heating device 103 Gas supply device 104 Gas supply hole 105 Gas discharge hole 110 Heating means 111 Temperature detection means 112 Heating control means 113 Gas supply amount control means 207 Solution 301 Heat shield plate

Claims

1. An evaporative drying apparatus comprising: an evaporative drying container for holding a solution in which a radioactive substance is dissolved and evaporating it to dryness; a heating device for heating the evaporative drying container; and a gas supply device for supplying gas to the evaporative drying container; wherein the evaporative drying container has a sealed structure that blocks it from the outside air and is equipped with at least one gas supply hole for supplying gas and at least one gas discharge hole for discharging gas; the heating device comprises heating means for heating the underside of the evaporative drying container or a position below it, temperature detection means for detecting the temperature at a specified position on the evaporative drying container, and heating control means for controlling the heating means based on the value detected by the temperature detection means; the gas supply device comprises gas supply amount control means for controlling the amount of gas supplied to the gas supply hole; the gas supply hole and the gas discharge hole are located on the top of the evaporative drying container or at a position above it; and the temperature detection means detects the temperature at the underside of the evaporative drying container or a position below it.

2. The evaporation-to-dryness apparatus according to claim 1, further comprising a heat shield plate, which is a wall-like member arranged to surround the side of the evaporation-to-dryness container when the evaporation-to-dryness container is heated.

3. The evaporation and drying apparatus according to claim 1, wherein the heating control means controls the temperature of the stable solution during continuous heating to be 1 to 10°C lower than the boiling point.

4. The evaporation and drying apparatus according to claim 1, characterized in that the heating control means uses at least one of the detection value of the temperature detection means and the heating output value of the heating means to detect complete evaporation of the solution in the evaporation and drying container.

5. The evaporation and drying apparatus according to claim 1, characterized in that the amount of gas sent to the evaporation and drying container by the gas supply amount control means is controlled so that the amount of gas sent becomes the amount of gas that is calculated by the following equation: Amount of gas discharged (L / min) = Volumetric rate of solvent vaporization (L / min) x (Atmospheric pressure at gas temperature / Saturated vapor pressure of solvent at gas temperature).

6. A method for evaporating to dryness, comprising evaporating a solution in which the radioactive substance is dissolved using the evaporating to dryness apparatus according to any one of claims 1 to 5, thereby precipitating the radioactive substance.

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