WO2025203734A1 - Evaporating/drying device and evaporating/drying method - Google Patents

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

The present invention relates to an apparatus for evaporating and drying a solution containing dissolved radioactive materials, and a method for evaporating and drying using the same.

Radioactive substances are used as radiopharmaceuticals that utilize radiation from radioactive isotopes. They are administered into the body to take radiological images to examine the condition of organs, and are also used in treatments to kill cancer cells by injection or oral administration.

Meanwhile, obtaining radiopharmaceuticals requires a separation and purification process to separate the desired radioactive material and remove impurities from radioactive material produced by irradiating neutrons in a nuclear reactor. In this radioactive material separation and purification process, the dissolving solution is changed as needed, and the process of adsorption and elution onto a resin is repeated. For this reason, an evaporation and drying process is essential, in which the solution in which the radioactive material has been dissolved is heated, the solvent evaporates, and the radioactive material (solid) is precipitated. 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 substances.

For example, Patent Document 1 describes a method in which 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 in which zirconium has eluted, is heated by a heater, thereby heating the recovered effluent contained therein. Patent Document 1 also describes an evaporation to dryness process in which the time required for evaporation to dryness is shortened by reducing the pressure inside the recovery vial while supplying a gas, such as an inert gas, from a gas supply unit into the recovery vial and performing agitation by bubbling.

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

In order to complete the evaporation and drying of a solution containing a substance, it is necessary to evaporate the solvent to the very end. In evaporation and drying methods that agitate the solution by bubbling, or that turn the solution into mist, turning the liquid into droplets increases the specific surface area of the liquid, 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 when the solution is bubbling or turned into mist.

Furthermore, while evaporation to dryness at high temperatures and reduced pressure can be carried out efficiently, there is a risk that the solution containing dissolved radioactive materials will splash due to overheating. Conversely, evaporation to dryness at temperatures below the boiling point poses the problem of increased emissions of gas containing radioactive materials, as evaporation takes time.

The present invention was made in consideration of the above situation. It is an object of the present invention to provide an evaporation-to-dryness device and an evaporation-to-dryness method that suppresses the scattering of a solution containing dissolved radioactive materials and reduces the amount of gas containing radioactive materials emitted.

The evaporative drying apparatus of the present invention, which solves the above-mentioned problems, comprises an evaporative drying container for holding a solution in which radioactive substances are 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. The evaporative drying container has a sealed structure that blocks 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 or a position below the evaporative drying container, 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 gas discharge hole are located on the top surface or above the evaporative drying container, and the temperature detection means detects the temperature at the underside or a position below the evaporative drying container.

The present invention provides an evaporation-to-dryness device and evaporation-to-dryness method that suppresses the scattering of solutions containing dissolved radioactive materials and reduces the amount of gas containing radioactive materials emitted.

1 is a schematic diagram of an evaporative to dryness apparatus 100 according to a first embodiment. FIG. FIG. 2 is a perspective view of an evaporating/drying container 101 and the periphery of the evaporating/drying container 101 in the first embodiment. FIG. 2 is a side view of the evaporating/drying container 101 and the periphery of the evaporating/drying container 101 in the first embodiment. FIG. 10 is a perspective view of an evaporating/drying container 101 and the periphery of the evaporating/drying container 101 according to a second embodiment. FIG. 10 is a side view of the evaporating/drying container 101 and the periphery of the evaporating/drying container 101 in the second embodiment. FIG. 10 is a schematic diagram of an evaporation to dryness apparatus 400 according to a third embodiment. 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 residual liquid amount (Arb.) (arbitrary unit) versus the heating time (min) and the detection 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).

Below, an evaporation-to-dryness apparatus and an evaporation-to-dryness method according to one embodiment of the present invention will be described, with appropriate reference to the drawings. Note that common components in the following description and drawings may be assigned the same reference numerals, and duplicate descriptions may be omitted.

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.

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

The evaporation to dryness apparatus 100 according to the first embodiment heats the solution 207 in which the radioactive substance is dissolved, thereby precipitating the radioactive substance.
As shown in FIG. 1, the evaporating/drying apparatus 100 according to the first embodiment includes an evaporating/drying container 101 , a heating device 102 , and a gas supplying device 103 .

As shown in Figures 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 it. The evaporating and drying container 101 has 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.

The heating device 102 heats the evaporation/dryness 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 evaporation/dryness 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.

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 to the gas supply hole 104, gas discharge hole 105, and liquid supply/discharge hole 106, which can block the outside air when no piping is connected. The bottom of the evaporator/drying vessel 101 has a roughly bowl-like shape that deepens towards 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 and concentrating the solution 207 with dissolved radioactive material to a desired concentration.

The gas supply hole 104, gas discharge hole 105, and liquid supply/discharge hole 106 are located on the top surface of the evaporation/drying container 101 or at a position approximately above it. The gas supply hole 104 and the gas supply pipe 107 are connected by a pipe joint 202, and the supply gas 203 supplied from the gas supply device 103 is supplied to the evaporation/drying container 101.

Meanwhile, the gas discharge hole 105 and the gas discharge pipe 108 are connected by a pipe joint 202, and discharged gas 204 is discharged from the evaporation and drying container 101. Furthermore, in order to recover the solvent in the discharged gas 204 or radioactive materials mixed in the discharged gas 204, one or more heat exchangers or an exhaust device can be installed downstream of the gas discharge pipe 108, or one or more heat exchangers and exhaust devices can be installed in series. A vacuum pump can also be used instead of an exhaust device.

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 opposite end of the liquid supply and discharge hole 106, i.e., the end not connected to the liquid supply and discharge pipe 109. The evaporator/drying 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 evaporator/drying vessel 101. Specifically, the open end of this end faces the deepest position on the bottom of the roughly cone-shaped evaporator/drying vessel 101, and is positioned close to this deepest position. This prevents the solution 207, containing dissolved radioactive material, from splashing onto the wall of the evaporator/drying vessel 101 when it is supplied to the evaporator/drying vessel 101.

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, it is possible to prevent the solution 207 containing dissolved radioactive material from splashing onto the walls of the evaporation and drying container 101. In this case, by repeatedly supplying and discharging very small amounts of solvent, the solution 207 is stirred, which promotes the dissolution of the radioactive material into the solvent. Furthermore, by stopping the evaporation and drying process midway, the solution 207 containing dissolved radioactive material can be concentrated to the desired concentration. At this time, the small amount of concentrated solution 207 collects in the center, making it easy to discharge the solution 207.

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 to separate the desired radioactive material or to remove impurities. This end can also be connected to a container that stores a solution 207 in which the radioactive material has been dissolved, a container that stores the solution 207 discharged from the resin-filled column, or a container that stores a solvent.

The heating means 110 is disposed on or below the bottom surface of the evaporator/drying container 101 and heats the evaporator/drying container 101. The temperature detection means 111 detects the temperature at a specified position on the evaporator/drying container 101. Specifically, the temperature detection means 111 performs temperature measurement 117 at a specified position on or below the bottom surface of the evaporator/drying container 101, close to the solution 207 in which the radioactive material has been dissolved, to obtain this temperature information and detect the temperature of the evaporator/drying container 101. Ideally, the temperature detection means 111 would detect the temperature of the solution 207 in which the radioactive material has been dissolved itself. However, the temperature detection means 111 would be radioactively contaminated by the radioactive material in the solution 207, increasing the amount of radioactive contaminants; solids after evaporation may adhere to the temperature detection means 111, making it impossible to measure the temperature accurately; and the liquid level changes as evaporation progresses, making it difficult to measure the temperature accurately. For these reasons, the temperature detection means 111 is used instead.

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. In other words, 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, thermal convection reduces temperature unevenness in the solution 207, allowing the solvent to evaporate efficiently. As a result, the generation of bubbles (boiling) due to overheating is suppressed, and the solution 207 in which the radioactive substance is dissolved is prevented from splashing onto the wall surface of the evaporator/drying container 101. Furthermore, because temperature unevenness is small, the evaporation time is shortened, and the amount of gas containing radioactive substance emitted is reduced.

As materials for the evaporation and drying vessel 101, 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 connection part 115, the pipe fitting 202, and the fittings (not shown), any suitable material can be used depending on the type of fluid, as long as it does not adversely affect the supply gas 203, the discharge gas 204, or the solution 207 containing dissolved radioactive material, 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.

The material of the evaporator/drying vessel 101 is heated by the heating means 110, and can be appropriately selected depending on the type of solvent in the solution 207 containing dissolved radioactive material and the heat resistance temperature of the material. Specific examples of materials that can be used for the evaporator/drying vessel 101 include glass such as quartz glass, soda glass, lead glass, and borosilicate glass, as well as fluororesins 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 vessel 101. Furthermore, by using a transparent or nearly transparent material for the portion filled with the solution 207 containing dissolved radioactive material, the evaporation and drying process within the evaporator/drying vessel 101 can be visually observed.

Since the materials for the gas supply pipe 107, the connecting part 115, and the joints (not shown) are not heated by the heating means 110, they can be selected appropriately depending on the heat resistance temperature of the material. The materials for the gas discharge pipe 108, the liquid supply/discharge pipe 109, the liquid supply/discharge pipe 205, and the pipe joints 202 can be selected appropriately depending on the type of solvent in the solution 207 in which the radioactive material is dissolved and the heat resistance temperature of the material. 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.

The heating means 110 may be a plate heater such as a mica heater, polyimide heater, or silicone rubber heater, a Peltier unit, a mantle heater, a heat exchanger using a heat medium, or a thermostatic bath using a heat medium, or any other suitable device.
The temperature detection means 111 may be any of various thermocouples, platinum resistance thermometers, thermistors, and the like.

The heating control means 112 controls the heating means 110 based on the detection value (temperature detection value 118) of the temperature detection means 111. The heating control means 112 controls the heating means 110 to heat (control) 116 the evaporation/drying container 101. The heating control means 112 is only required to compare the temperature detection value (observation quantity) 118 from the temperature detection means 111 with the temperature set value and control the heating means 110 according to the deviation. Examples of control methods include continuous control using PID control and ON-OFF control.

The gas supply amount control means 113 controls the amount of gas supplied to the gas supply hole 104. The gas supply amount control means 113 may be a gas flow meter or a mass flow meter.
Examples of the gas supply means 114 include a gas cylinder, a vaporization supply device, etc. 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.

(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/discharge pipe 109 through the pipe joint 202, the liquid supply/discharge hole 106, and the liquid supply/discharge pipe 205 into the evaporation/dryness container 101. Note that this solution 207 in which a radioactive substance is dissolved can also be placed in the evaporation/dryness container 101 in advance, depending on the situation.

The supply of supply gas 203 begins from gas supply device 103. The temperature setting value of heating device 102 is set to a predetermined temperature, and heating control is initiated so that the temperature measured by temperature detection means 111 is equal to the temperature setting value. The solvent evaporates according to the saturated vapor pressure of the solvent at the temperature of supply gas 203, and evaporation progresses. When temperature detection value 118 of temperature detection means 111 reaches the temperature setting value, the temperature of solution 207 containing dissolved radioactive material becomes almost constant, and evaporation progresses stably. Once evaporation is complete, there is no solvent to be heated, and supply gas 203 is heated. Because heating is performed in a closed system, the temperature does not drop, 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 heating means 110 drops sharply. In this state, evaporation to dryness of solution 207 containing dissolved radioactive material is completed, and precipitation of the radioactive material is also completed.

The supply gas 203 may be any gas that does not adversely affect the solution 207 in which the radioactive material is dissolved, and may be an inert gas such as nitrogen gas or argon gas, or dry air.
Furthermore, the temperature setting value can be appropriately set to a temperature at which bubbles due to overheating do not occur (no boiling occurs) and the solution 207 containing dissolved radioactive materials evaporates efficiently, depending on the types of evaporator/drying container 101 and heating device 102. If the temperature setting value is low, bubbles due to overheating do not occur, but the heating time becomes longer, which may increase the amount of gas emitted containing radioactive materials. On the other hand, if the temperature setting value is too high, bubbles may occur due to overheating, which may cause the solution 207 containing dissolved radioactive materials to splash or lead to thermal denaturation of the radioactive materials.

Therefore, by controlling the solution temperature to a temperature that does not boil and is as high as possible, scattering of the solution 207 containing dissolved radioactive material is suppressed and the amount of gas containing 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.

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

Second Embodiment
An evaporative to dryness apparatus 100 according to a second embodiment of the present invention and an evaporative to dryness method using the evaporative to 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.

(Evaporation to dryness apparatus)
Fig. 3A is a perspective view of the evaporating/drying container 101 and the surrounding area thereof in the second embodiment. Fig. 3B is a side view of the evaporating/drying container 101 and the surrounding area thereof in the second embodiment.

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.

The heat shield 301 makes the evaporator/drying container 101 less susceptible to the effects of 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.

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

(Evaporation to dryness method)
Using the evaporative drying apparatus 100 according to the second embodiment described above, the solution 207 in which a radioactive substance is dissolved can be evaporated to dryness, and the radioactive substance can be precipitated, in the same manner as in the evaporative drying 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 in which the radioactive substance is dissolved 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.

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

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.

(Evaporation to dryness apparatus)
FIG. 4 is a schematic diagram of an evaporation to dryness apparatus 400 according to the third embodiment.
As shown in FIG. 4, the evaporative drying apparatus 400 according to the third embodiment differs from the evaporative drying apparatus 100 according to the first and second embodiments in that it is provided with a primary heat exchanger 401, a secondary heat exchanger 402, and an exhaust device 403 downstream of the gas exhaust piping 108.

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

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

The materials for the primary heat exchanger 401 and the secondary heat exchanger 402 can be selected appropriately 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 and chemical resistance, a lining made of glass or an oxide film formed by the oxidation of silicon may be formed on the surfaces of the primary heat exchanger 401 and the secondary heat exchanger 402, respectively. Furthermore, by using a transparent or nearly transparent material, it is possible to visually observe the recovery of the liquefied solvent in the primary heat exchanger 401 and the secondary heat exchanger 402.

The primary heat exchanger 401 and the secondary heat exchanger 402 may be a heat exchange trap, a trap bottle, or the like.
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 solution 207 in which the radioactive material is dissolved.

(Evaporation to dryness method)
In the evaporative drying apparatus 400 according to the third embodiment, the solution 207 in which the radioactive substance is dissolved can be evaporated to dryness to precipitate the radioactive substance, in the same manner as in the evaporative drying method using the evaporative drying apparatus 100 according to the first or second embodiment.

During and after the 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 then liquefies the vaporized solvent in the exhaust gas 204, and recovers any radioactive material contained in very small amounts along with the solvent.

The secondary heat exchanger 402 then receives the gas that has passed through the first gas discharge pipe 404, liquefies any vaporized solvent that was not liquefied in the primary heat exchanger, and recovers any traces of radioactive material that may be present along with the solvent. This reduces the amount of gas containing radioactive material that is emitted.

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 and drying device 400.

Figure 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 drying apparatus 400 according to the third embodiment, and shows the relationship between the residual liquid amount (Arb.) (arbitrary units) versus heating time (min) and the detected value (Arb.) of the temperature detection means 111. Figure 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 drying apparatus 400 according to the third embodiment, and shows 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.

As shown in Figure 5A, the amount of residual liquid began to decrease as soon as heating control by heating device 102 was initiated. The value detected by 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 had passed and the amount of residual liquid had reached zero and evaporation was complete, the value detected by temperature detection means 111 tended to become unstable. On the other hand, as shown in Figure 5B, the heating output value of heating means 110 reached its maximum as soon as heating control by heating device 102 was initiated. Thereafter, the heating output value of 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.

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 instability in the detection value of the temperature detection means 111 and a sudden drop in the heating output value of the heating means 110 in advance when evaporating and drying the solution 207 containing dissolved radioactive materials. In this way, the evaporating and drying apparatus 400 can minimize the amount of gas emitted that contains radioactive materials.

Furthermore, the heating control means 112 can detect complete evaporation of the solution 207 in the evaporator/drying 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 in this way, it terminates heating. In this way, the evaporator/drying device 400 can reduce or prevent thermal denaturation of the radioactive material while minimizing the amount of gas discharged that contains the radioactive material.
Before complete evaporation, while the solution 207 remains, the temperature is almost constant due to the latent heat of evaporation of the solution 207. However, once complete evaporation occurs, the temperature rises. Therefore, complete evaporation can be determined by a change in the detection value of the temperature detection means 111.
Furthermore, the heating output value of the heating means 110 also changes, so complete evaporation can also be determined from the change in the heating output value.

The optimum value of the flow rate (amount of gas sent) of the supply gas 203 in FIGS. 5A and 5B can be determined as follows.
Since the evaporation and drying vessel 101 is constantly supplied with gas, it is not an enclosed space, and assuming that it does not follow gas-liquid equilibrium, it is believed that Equation 1 generally holds true according to Boyle's law.
(Formula 1)
Saturated vapor pressure of solvent at gas temperature × exhaust volume (L/min) ≒ atmospheric pressure at gas temperature × solvent vaporization volume rate (L/min)

By transforming Equation 1, Equation 2 is obtained.
(Formula 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)

From Equation 2, it is possible to minimize the amount of gas containing radioactive materials emitted by controlling the amount of gas supplied 203 to the evaporation and drying vessel 101 so that it is approximately the same as the flow rate (exhaust volume) of exhaust gas 204 calculated by Equation 2. Specifically, it is desirable to control it to within ±10 to 20% of the flow rate of exhaust gas 204 calculated by Equation 2.

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

The evaporation to dryness apparatus and evaporation to dryness method according to the present invention have been described in detail above using embodiments, but 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 are 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 set forth in the claims.

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 (6)

The method comprises: an evaporation and drying container for holding a solution in which a radioactive substance is dissolved and evaporating and drying the solution; a heating device for heating the evaporation and drying container; and a gas supplying device for supplying a gas to the evaporation and drying container;
the evaporation and drying container has a sealed structure that is isolated from the outside air, and includes at least one gas supply hole that can supply gas and at least one gas discharge hole that can discharge gas;
The heating device includes a heating means for heating the lower surface or a position below the evaporating and drying container, a temperature detecting means for detecting the temperature at a predetermined position of the evaporating and drying container, and a heating control means for controlling the heating means based on a value detected by the temperature detecting means;
the gas supply device includes a 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 arranged on the top surface or at an upper position of the evaporation and drying container;
An evaporation to dryness apparatus, characterized in that the temperature detection means detects the temperature of the lower surface or a position below the evaporation to dryness container. The evaporation and drying apparatus described in claim 1, characterized in that it is equipped with a heat shield, which is a wall-shaped member arranged to surround the side of the evaporation and drying container when the evaporation and drying container is heated. The evaporation and drying apparatus described in claim 1, characterized in that the heating control means controls the stable solution liquid temperature during continuous heating to be 1°C to 10°C lower than the boiling point. The evaporation and drying apparatus described in 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. The amount of gas sent to the evaporation and drying container by the gas supply amount control means is
Discharge volume (L/min) = solvent vaporization volume rate (L/min) × (atmospheric pressure at gas temperature/saturated vapor pressure of solvent at gas temperature)
2. The evaporation and drying apparatus according to claim 1, wherein the amount of exhaust gas is controlled so as to be determined by the following formula: An evaporation-to-dryness method, characterized by evaporating a solution containing a radioactive substance using the evaporation-to-dryness apparatus described in any one of claims 1 to 5, thereby precipitating the radioactive substance.