WO2019203725A1 - Process and system for removing radioactive ions present in a liquid - Google Patents

Process and system for removing radioactive ions present in a liquid Download PDF

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Publication number
WO2019203725A1
WO2019203725A1 PCT/SG2018/050190 SG2018050190W WO2019203725A1 WO 2019203725 A1 WO2019203725 A1 WO 2019203725A1 SG 2018050190 W SG2018050190 W SG 2018050190W WO 2019203725 A1 WO2019203725 A1 WO 2019203725A1
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Prior art keywords
precipitant
supernatant
treatment tank
liquid
precipitate
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PCT/SG2018/050190
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French (fr)
Inventor
Ganendra ARIYATHAVARATNAM
Chong Lin TAN
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E.L.I (Environment Laboratory Impact) Services Pte. Ltd.
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Publication date
Application filed by E.L.I (Environment Laboratory Impact) Services Pte. Ltd. filed Critical E.L.I (Environment Laboratory Impact) Services Pte. Ltd.
Priority to AU2018419491A priority Critical patent/AU2018419491A1/en
Priority to PCT/SG2018/050190 priority patent/WO2019203725A1/en
Publication of WO2019203725A1 publication Critical patent/WO2019203725A1/en

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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/04—Treating liquids
    • G21F9/06—Processing
    • G21F9/10—Processing by flocculation

Definitions

  • the present disclosure relates to a process for removing radioactive ions present in a liquid.
  • the present disclosure relates to a process for removing radioactive ions present in a urine through the formation of insoluble substance by adding a precipitant to the urine.
  • Radioactive isotopes have been studied and utilized for clinical applications. Many iodine radioisotopes, such as 131 I, 124 I, 123 I, and 125 I, are routinely used in diagnosis and treatment of diseases such as thyroid cancer and hyperthyroidism. Furthermore, the iodine radioisotopes can be attached to other chemicals forming radioactive tracers which are useful in Positron Emission Tomography (PET) and Single Photo Emission Tomography (SPECT) for diagnosis of many cancers.
  • PET Positron Emission Tomography
  • SPECT Single Photo Emission Tomography
  • the lutetium radioisotope also has various medical uses such as treatment of cancer and palliation of bone pain due to cancer metastasis.
  • the lutetium radioisotope is also attached to other chemicals.
  • 177 Lu is routinely conjugated to PSMA, DOTATATE, DOTATOC, DOTANOC, MDP, HMDP, and/or HEDP for treatment of recurrent prostate cancer, neuroendocrine tumor, and/or bone pain palliation.
  • the general practice is to apply a store-and-decay method in which patients’ urine is to be collected and stored in a specific environment for a period of time equivalent to at least 10 half-lives before being discharged to public sewage.
  • Each radioisotope has a specific half-life and some radioisotopes have significantly longer half-lives than the others.
  • 177 Lu has a half-life of 6 days and 131 I has a half-live of 8 days, while 125 I has a half-life of 60 days.
  • urine from the patients administered with 177 LU will have to be stored for at least 60 days, urine from the patients administered with 131 I for at least 80 days, and urine from the patients administered with 125 I for at least 600 days.
  • the storage conditions include extensive spaces, complex monitoring protocols, and hygienist treatment for the urine storage tanks.
  • a typical storage system would require 3 storage tanks of more than 5000 L, each provided with various equipment, such as radiation monitor, pH monitor, liquid level monitor, and gas trap.
  • One of the methods involves using strong chemicals such as hydrochloric acid and lengthy procedures such as adjusting pH, heating to 40°C and passing through silver chloride column (Fletcher K, “The Fractionation of urinary iodine”, Biochemical Journal , 1957; 67(1): 140-146).
  • the method described is only carried out in a small portion which is insufficient for a practical waste load and it can be disadvantageously difficult to implement as a system since it would require numerous components for the procedures.
  • Benes et al. (U.S. Patent 6,773,686, filed on August 7, 1978) describes an apparatus for the removal of radioactive iodine from a liquid by adding a carrier substance, such as potassium iodide, and a solution of a silver salt to the liquid.
  • a carrier substance such as potassium iodide
  • the process develops an insoluble, radioactive precipitate which is removed from the urine by the use of a filtration unit.
  • This process requires a production of a filtration unit which in turn increases the cost of the system. Additionally, the filtration unit would require manual replacement after a relatively short period of time.
  • Jeon et al. discloses a process and a device for removing iodide using gold particles.
  • One embodiment describes the process of contacting the urine with the gold particles using a column or a membrane filter. This process requires a large size column into which gold particles are poured. The requirement for the gold particles as one of the main components can result in an expensive system.
  • the present invention alternatively provides a faster and/or cheaper method of removing radioactive ions from a liquid which can minimize the space and monitoring requirement of the store-and-decay method.
  • the invention can also replace the conventional methods for removing radioactivity which can be relatively expensive.
  • a process for removing radioactive ions present in a liquid comprising the steps of opening a first precipitant inlet for introducing a precipitant to the liquid in a first treatment tank, mixing the precipitant with the liquid by starting a first mixing device to form a first suspension by precipitation reaction involving the precipitant and the liquid, settling the first suspension after stopping the first mixing device and closing the first precipitant inlet for separating the first suspension into a first supernatant layer and a first precipitate layer, detecting radioactivity in the first supernatant layer using a first radiation probe, opening a first supernatant outlet for draining the first supernatant layer out of the first treatment tank, opening a first precipitate outlet for disposing the first precipitate layer out of the first treatment tank and using a controller which is in electrical communication with the first precipitant inlet, the first mixing device, the first radiation probe, and the first supernatant outlet, to control the first mixing device, the first precipitant inlet, the first radiation probe, and the first supernatant outlet.
  • the step of mixing includes providing a turbine or providing a diffuser for introducing air, the air being supplied from an air compressor via an air supply line.
  • the process further comprises the step of reacting the first precipitate layer by introducing a desludging agent to the first precipitate layer.
  • the process further comprises the step of disposing the reacted first precipitate layer away from the first treatment tank via the first precipitate outlet.
  • the step of reacting the first precipitate layer includes introducing an acidic solution as the desludging agent.
  • the step of opening the first precipitant inlet for introducing the precipitant to the liquid includes providing a supply tank in fluid communication with the first treatment tank for holding the precipitant or includes introducing any one of metal solution and anion solution as the precipitant.
  • the step of introducing the precipitant to the liquid includes providing at least one of nitrate, chloride, bromide, carbonate, and bicarbonate of any one of lead (Pb), silver (Ag), and Mercury (Hg) as the metal solution or includes providing at least one of oxalate, carbonate, hydroxide, fluoride, phosphate, and oxide solution as the anion solution.
  • the radioactive ions include any of iodide ion and lutetium ion.
  • the process further comprises the step of providing a second treatment tank for opening a second precipitant inlet for introducing the precipitant to the liquid in the second treatment tank, wherein the precipitant is introduced from the supply tank; mixing the precipitant with the liquid by starting a second mixing device to form a second suspension by precipitation reaction involving the precipitant and the liquid; settling the second suspension after stopping the second mixing device and closing the second precipitant inlet or separating the second suspension into a second supernatant layer and a second precipitate layer; detecting radioactivity in the second supernatant layer using a second radiation probe; opening a second supernatant outlet for draining the second supernatant layer out of the second treatment tank; opening a second precipitate outlet for disposing the second precipitate layer out of the second treatment tank; and using the controller which is in electrical communication with the second precipitant inlet, the second mixing device, the second radiation probe, and the second supernatant outlet, to control the second mixing device, the second precipitant inlet, the second radiation probe, and the second supernatant outlet
  • a system for removing radioactive ions present in a liquid comprising a first precipitant inlet for opening to introduce a precipitant to the liquid and closing to discontinue introduction of the precipitant to the liquid, a first treatment tank for forming a first suspension by precipitation reaction involving the precipitant and the liquid and settling the first suspension to separate the first suspension into a first supernatant layer and a first precipitate layer, a first mixing device disposed in the first treatment tank for mixing the precipitant with the liquid, a first radiation probe disposed in the first treatment tank for detecting radioactivity in the first supernatant layer, a first supernatant outlet disposed on the first treatment tank for draining the first supernatant layer out of the first treatment tank, a first precipitate outlet disposed on the first treatment tank for disposing the first precipitate layer out of the first treatment tank and a controller which is in electrical communication with the first precipitant inlet, the first mixing device, the first radiation probe, and the first supernatant outlet for controlling the first precipitant inlet, the first mixing device
  • the first mixing device includes a turbine or includes a diffuser for introducing air, wherein the diffuser is in fluid communication with an air compressor and an air supply line for supplying the air.
  • a desludging agent is introduced to the first precipitate layer for reacting the first precipitate layer.
  • the reacted first precipitate layer is disposed away from the first treatment tank via the first precipitate outlet.
  • the desludging agent is an acidic solution.
  • the system further comprises a supply tank for holding the precipitant, wherein the supply tank is in fluid communication with the first treatment tank for introducing the precipitant to the liquid.
  • the precipitant is any one of metal solution and anion solution.
  • the metal solution is at least one of nitrate, chloride, bromide, carbonate, and bicarbonate of any one of lead (Pb), silver (Ag), and Mercury (Hg).
  • the anion solution is at least one of oxalate, carbonate, hydroxide, fluoride, phosphate, and oxide solution.
  • the radioactive ions include any of iodide ion and lutetium ion.
  • the system further comprises a second precipitant inlet for opening to introduce the precipitant from the supply tank to the liquid and closing to discontinue introduction of the precipitant to the liquid; a second treatment tank in fluid communication with the first treatment tank and the first supernatant outlet for forming a second suspension by precipitation reaction involving the precipitant and the liquid and settling the second suspension to separate the second suspension into a second supernatant layer and a second precipitate layer; a second mixing device disposed in the second treatment tank for mixing the precipitant with the liquid; a second radiation probe disposed in the second treatment tank for detecting radioactivity in the second supernatant layer; a second supernatant outlet disposed on the second treatment tank for draining the second supernatant layer out of the second treatment tank; a second precipitate outlet disposed on the second treatment tank for disposing the second precipitate layer out of the second treatment tank; wherein the controller is in electrical communication with the second precipitant inlet, the second mixing device, the second radiation probe, and the second supernatant outlet for controlling the second precipitant
  • Figure 1 shows a schematic diagram of a system for removing radioactive ions present in a liquid according to an embodiment of the present invention
  • FIG 2 shows a flowchart of the process according to the embodiment of the present invention as shown in Figure 1.
  • Figure 3 shows a schematic diagram of the system according to another embodiment of the present invention.
  • the description herein may be, in certain portions, explicitly or implicitly written as algorithms and/or functional operations that operate on data within a computer memory or an electronic circuit. These algorithmic descriptions and/or functional operations are usually used by those skilled in the information/data processing arts for efficient description.
  • An algorithm is generally relating to a self-consistent sequence of steps leading to a desired result.
  • the algorithmic steps can include physical manipulations of physical quantities, such as electrical, magnetic, or optical signals capable of being stored, transmitted, transferred, combined, compared, and otherwise manipulated.
  • the disclosure may have provided a method and/or process as a particular sequence of steps. However, unless otherwise required, it will be appreciated the method or process should not be limited to the particular sequence of steps disclosed.
  • embodiments described herein provide a system 100 for removing radioactive ions, such as radioactive iodine and radioactive lutetium, present in a liquid.
  • the liquid includes urine excreted by patients administered with radioactivity, such as iodine and lutetium.
  • the system 100 comprises a reagent inlet 101, also called as a precipitant inlet and/or a supply inlet, which can be opened to introduce a precipitant/reagent to the urine.
  • the reagent inlet 101 can also be closed to stop the introduction of the precipitant to the urine as appropriate.
  • the system 100 further comprises a treatment tank/decay tank 102 where a suspension (not shown) can be formed by precipitation reaction involving the precipitant and the urine.
  • a mixing device 104 is installed in the decay tank 102 for mixing the precipitant with the urine in order to facilitate the precipitation reaction.
  • the suspension is settled in the decay tank 102 and thus is separated into a supernatant 106 and a precipitate/sludge 108.
  • a radiation probe 110 is further installed in the decay tank 102 to determine the radioactivity of the supernatant 106.
  • a supernatant outlet 112 is placed on the decay tank 102 for removing the supernatant 106 from the decay tank 102, and a precipitate outlet 1 14 is placed on the decay tank 102 for removing the precipitate 108 from the decay tank 102.
  • a controller 1 15 is in electrical communication, such as wired connection, with the reagent inlet 101, the mixing device 104, the radiation probe 1 10, and the supernatant outlet 1 12 for controlling the functions of the components.
  • Figure 2 illustrates a process 200 for removing radioactive ions present in the urine according to the embodiment in Figure 1.
  • the reagent inlet 101 is opened in order to add the precipitant to the urine in the decay tank 102.
  • the precipitant is mixed with the urine by activating the mixing device 104.
  • the suspension is formed by precipitation reaction involving the precipitant and the urine.
  • the mixing device 104 is stopped and the reagent inlet 101 is closed so that the suspension can settle. Accordingly, the suspension is separated into the supernatant 106 and the precipitate 108.
  • the radiation probe 1 10 detects/measures radioactivity of the supernatant 106.
  • the supernatant outlet 1 12 is opened in order to drain the supernatant 106 out of the decay tank 102.
  • the precipitate outlet 1 14 is used for removing the precipitate 108 out of the decay tank 102.
  • the controller 1 15 is used for controlling the reagent inlet 101, the mixing device 104, the radiation probe 1 10, and the supernatant outlet 1 12. With the use of the controller 1 15, the steps 202, 203, 204, and 205 are performed in sequential order.
  • the radioactive ions include an iodide ion.
  • the radioactive liquid includes any iodide solution and urine excreted by the patients administered with at least one type of isotopes of iodine.
  • the isotopes of iodine include non-radioactive isotopes and radioactive isotopes (also known as radioisotope, radionuclide, and radioactive nuclide) such as 108 I, 109 I, 110 I, 1U I, 112 I, 113 I, 114 I, 114m I, 115 I, 116 I, 116m I, 117 i
  • the radioactive ions include a lutetium ion.
  • the radioactive liquid includes any lutetium solution and urine excreted by the patients administered with at least one type of isotopes of lutetium.
  • the isotopes of lutetium include non radioactive isotopes and radioactive isotopes such as 150 Lu, 150m Lu, 151 Lu, 151m Lu, 152 Lu, i53 Lu , 153ml Lu, 153m2 Lu, 153m3 Lu, 154 LU, 154ml Lu, 154m2 Lu, 155 Lu, 155ml Lu, 155m2 Lu, 156 Lu, 156m Lu, 157 LU, 157m Lu, 158 LU, 159 LU, 159m Lu, 160 Lu, 160m Lu, 161 Lu, 161m Lu, 162 Lu, 162ml Lu, 162m2 Lu, 163 LU, 164 LU, 165 LU, 166 LU, 166ml
  • the decay tank 102 is connected with an external source 116 via an inlet channel 118 and an inlet valve 120.
  • the urine is introduced to the decay tank 102 from the external source 116 where the external source 116 is a means of collecting urine including a receptacle provided at a conventional toilet and a separation toilet (also known as urine-diverting toilet).
  • the external source 116 is a means of collecting urine including a receptacle provided at a conventional toilet and a separation toilet (also known as urine-diverting toilet).
  • a level sensor 122 capable of detecting a substance in a container is installed in the decay tank 102 and is in electrical communication with the controller 115.
  • the level sensor 122 detects the level of the liquid in the decay tank 102 whether the level has reached a certain threshold, e.g. the urine from the external source 116 has been introduced into the decay tank 102, then sends the signal to the controller 115.
  • a certain threshold e.g. the urine from the external source 116 has been introduced into the decay tank 102
  • the step 201 includes providing a supply tank/reagent tank 124 for holding the precipitant/reagent.
  • the reagent tank 124 is in fluid communication or connected with the decay tank 102 via the reagent inlet 101 and a supply valve/reagent valve 128.
  • the reagent inlet 101 is connected with a supply pump/reagent pump 130 in order to facilitate the conveyance/transportation of the precipitant in the reagent tank 124 to the decay tank 102.
  • the reagent valve 128 and the reagent pump 130 are in electrical communication with the controller 115.
  • the signal from the level sensor 122 is received by the controller 115 and the controller 115 supplies an electrical signal to activate the reagent pump 130 and the reagent valve 128.
  • the activation of the reagent pump 130 and the reagent valve 128 results in the introduction of the precipitant to the decay tank 102 as well as the urine present in the decay tank 102 via the reagent inlet 101.
  • the mixing device 104 includes any one of applicable industrial mixers, such as a turbine, where the mixing device 104 is installed inside the decay tank 102 and in electrical communication with the controller 115.
  • the controller determines if step 202 should be commenced (e.g. after the introduction of the precipitant to the decay tank 102 is completed) and supplies an electrical signal to the mixing device 104, e.g. a turbine, to activate the operation thereof.
  • the mixing device 104 e.g. a turbine
  • the mixing device 104 is a diffuser or similar means capable of introducing air to a defined space.
  • the mixing device 104 e.g. a diffuser, is in fluid communication with at least one air compressor 132 via an air supply line/air channel 134.
  • the air channel 134 is in fluid communication with an air supply/air valve 136.
  • an air vent 138 is provided at the decay tank 102, preferably at the top of the decay tank 102 connecting to outside environment.
  • the air compressor 132 and the air valve 136 are in electrical communication with the controller 115.
  • the controller determines if step 202 should be commenced (e.g. after the introduction of the precipitant to the decay tank 102 is completed) and sends an electrical signal to the air compressor 132 and the air valve 136 to activate the operation thereof.
  • air is drawn by the air compressor 132 from outside environment and introduced to the mixing device 104 via the air channel 134 and air valve 136.
  • the air is further introduced to the decay tank 102 by the mixing device 104, e.g. a diffuser, located preferably at the bottom of the decay tank 102, moves upwards through the substance in the decay tank 102, and is ventilated to outside environment via the air vent 138.
  • step 202 enables or results in producing the suspension by precipitation reaction involving the precipitant and the urine in step 203.
  • the suspension After stopping the mixing device 104 and closing the reagent inlet 101, the suspension is allowed to stand for a certain period of time to separate the suspension into the supernatant 106 and the precipitate 108.
  • the step is indicated as step 203.
  • the step 203 is effected by sending an electrical signal from the controller 115 to the mixing device 104, e.g. a turbine, to stop the mixing device 104 and waiting for a set period of time.
  • the mixing device 104 e.g. a turbine
  • the step 203 is effected by sending an electrical signal from the controller 115 to the air valve 136 and the air compressor 132 so that air no longer flows or circulates inside the decay tank 102 and waiting for a set period of time.
  • the step of stopping the mixing device 104 is carried out automatically by the controller 115, for example, the controller 115 sends an electrical signal to stop the mixing device 104 after a predetermined period of time has expired.
  • the predetermined period of time is programmed in the controller.
  • the set period of time is the time required for at least 50 percent of the suspension to separate into the supernatant 106 and the precipitate 108.
  • the set period of time is generally in the range of 0.5 to 2 hours.
  • the decay tank 102 is provided with the radiation probe 110 for detecting the radioactivity of the supernatant 106 in the decay tank 102.
  • the radiation probe 110 is in electrical communication with the controller 115.
  • a tank pump 140 is provided in the decay tank 102 where the supernatant 106 is for draining the supernatant 106 out of the decay tank 102.
  • the tank pump 140 is in fluid communication with the supernatant outlet 112 and is in electrical communication with the controller 115.
  • the tank pump 140 receives the supernatant 106 directly from the decay tank 102 and further conveys the supernatant 106 via the supernatant outlet 112.
  • the supernatant outlet 112 is provided at the location where the supernatant 106 is in the decay tank 102 for draining the supernatant 106 out of the decay tank 102.
  • the supernatant outlet 112 is in fluid communication with the tank pump 140 and the tank pump 140 is in electrical communication with the controller 115.
  • the supernatant outlet 112 receives the supernatant 106 from the decay tank 102 and conveys the supernatant 106 to the tank pump 140.
  • the supernatant outlet 112 for draining the supernatant 106 out of the decay tank 102 can be in fluid communication with a supernatant valve 144.
  • the supernatant valve 144 is in electrical communication with the controller 115.
  • the radiation probe 110 detects radioactivity of the supernatant 106 in the decay tank 102 whether the radioactivity has fallen below a threshold, e.g. the activity level of 0.5 mSv (the background radiation), then sends the signal to the controller 115. Once the signal is received by the controller 115, the controller 115 sends an electrical signal to activate the tank pump 140 and the supernatant valve 144. The activation of the tank pump 140 and the supernatant valve 144 results in the drainage of the supernatant 106 away from the decay tank 102.
  • a threshold e.g. the activity level of 0.5 mSv (the background radiation
  • any one of the decay tank 102, the supernatant outlet 112, and the supernatant valve 144 or the combinations thereof are in fluid communication with sewage.
  • the supernatant 106 can be drained away from the decay tank 102 to sewage.
  • the supernatant outlet 112 can be further in fluid communication with an outlet radiation probe 146 where the outlet radiation probe 146 is in electrical communication with the controller 115.
  • the process further comprises the step of preventing the radioactive supernatant from draining away from the decay tank 102.
  • the outlet radiation probe 146 detects radioactivity of the supernatant 106 drained away from the decay tank 102 via the supernatant outlet 112 whether the radioactivity has reached a threshold, e.g. the activity level of 0.5 mSv (the background radiation), then sends the signal to the controller 115. Once the signal is received by the controller 115, the controller 115 sends an electrical signal to shut the supernatant valve 144 and the tank pump 140 in order to prevent the drainage of the radioactive supernatant 106.
  • a threshold e.g. the activity level of 0.5 mSv (the background radiation
  • the controller 115 includes controller and electronic circuit capable of running a control program and sending electrical signals to devices.
  • the controller 115 is a programmable logic controller (PLC).
  • the controller 115 is a relay circuit of electromechanical type or solid-state type, and further, the controller 115 is a fully electronic control circuit or a mixed control circuit.
  • the process further comprises the step of reacting the precipitate 108, also called desludging, by introducing a desludging agent to the precipitate 108.
  • the introduction of the desludging agent may be carried out manually via a manual opening of a valve or by using the controller 115.
  • the desludging agent is an acidic solution which includes, but not limited to, hydrochloric acid at the concentration in the range of 5 % to 30%.
  • the process further comprises the step of disposing the reacted precipitate away from the decay tank 102 via the precipitate outlet 114.
  • the precipitate outlet 114 is generally located at the bottom of the decay tank 102, preferably in fluid communication with at least one valve.
  • the disposal of the reacted precipitate may be carried out manually via a manual opening of a valve or by using the controller 115.
  • the steps of reacting the precipitate and disposing the reacted precipitate should only occur once between every 180 days to every 360 days based on the load.
  • the comparative designs of the treatment tank may allow only for 90 days which in turn limits the capacity.
  • the decay tank 102 of an embodiment of the present invention can keep more liquid for a longer period of time without requiring the frequent disposal due to volume or radioactivity limits. Additionally, such longer period of time can advantageously decrease the radioactivity of the disposed precipitate, for example, 133 I present in the liquid may go through over forty half-lives which reduces radioactivity to background radiation.
  • a maintenance outlet 148 is provided at the decay tank 102 which is accessed manually for maintenance purposes.
  • the maintenance outlet 148 includes a manhole/maintenance hole with or without a fluid communication with a valve.
  • the precipitant includes a metal solution and/or anion solution.
  • the metal solution is at least one of nitrate, chloride, bromide, carbonate, and bicarbonate of any one of lead (Pb), silver (Ag), and Mercury (Hg) where the metal solution is used for removing iodide ion in urine.
  • the anion solution is at least one of oxalate, carbonate, hydroxide, fluoride, phosphate, and oxide solution where the anion solution is used for removing lutetium ion in urine.
  • the metal solution is silver nitrate solution at the concentration in the range of 500 to 800 mg/mL.
  • a silver nitrate solution is added to urine from the patients administered with radioactive iodine.
  • Such process causes a reaction creating a formation of an insoluble silver iodide compound (also called as precipitate) which is radioactive and a supernatant urine which is non-radioactive and thus can be discharged into sewage.
  • a solution containing the anion is added to the urine from the patients administered with radioactive lutetium.
  • the process causes a reaction creating a formation of an insoluble lutetium compound (also called as precipitate) which is radioactive and a supernatant urine which is non-radioactive and thus can be discharged into sewage.
  • a system 300 comprises a second treatment/second decay tank 350 connected with a first decay tank 302 (comparable to the decay tank 102 of the system 100) and the supernatant outlet 312 (comparable to the supernatant outlet 112 of the system 100).
  • the system 300 further comprises a second reagent inlet 351 which can be opened to introduce the precipitant from the supply tank 324 to the urine and closing to discontinue introduction of the precipitant to the urine.
  • the second reagent inlet 351 similar to the reagent inlet 101 of the system 100, can also be closed to stop the introduction of the precipitant to the urine as appropriate.
  • a second suspension is formed in the second decay tank 350 by precipitation reaction involving the precipitant and the urine.
  • a second mixing device 352 is installed in the second decay tank 350 for mixing the precipitant with the urine the second suspension is settled to separate the second suspension into a second supernatant 354 and a second precipitate 356.
  • a second radiation probe 358 is installed inside the second decay tank 350 to determine radioactivity of the second supernatant 354; a second supernatant outlet 360 is placed on the second decay tank 350 for removing the second supernatant 354 from the second decay tank 350; and a second precipitate outlet 362 is placed on the second decay tank 350 for removing the second precipitate 356 from the second decay tank 350.
  • the desludging agent is an acidic solution and the precipitant is a metal solution and/or anion solution based on the radioactive element present in the urine.
  • a controller 315 (comparable to the controller 115 of the system 100) is in electrical communication with the second mixing device 352, the second radiation probe 358, and the second supernatant outlet 360 for controlling the function of the components.
  • embodiments described herein comprise the steps of opening the second reagent inlet 351 for introducing the precipitant to the liquid in the second decay tank 350, wherein the precipitant is introduced from the supply tank 324; mixing the precipitant with the liquid using the second mixing device 352 to form a second suspension by precipitation reaction involving the precipitant and the liquid; settling the second suspension after stopping the second mixing device 352 and closing the second reagent inlet 351 for separating the second suspension into the second supernatant 354 and the second precipitate 356; detecting radioactivity in the second supernatant 354 using the second radiation probe 358; opening the second supernatant outlet 360 for draining the second supernatant 354 out of the second decay tank 350; opening the second precipitate outlet 362 for disposing the second precipitate 356 out of the second decay tank 350; using the controller 315 whereby the second decay tank 350 is in fluid communication with the decay tank 302 and the supernatant outlet 312.
  • the steps of mixing, settling the second suspension, detecting radioactivity, and opening the second supernatant outlet are performed in sequential order by the means of the controller 315.
  • the second decay tank 350 can perform the steps independently with the decay tank 302.
  • the second decay tank 350 may perform the steps alternatively, sequentially, chronologically, and/or simultaneously with the first decay tank 302. Since each tank may operate independently, it can be shut down for maintenance separately. This enables the process to be carried out with higher capacity when needed while providing ease of maintenance.
  • the embodiment can be further realized into providing a third decay tank 364.
  • the third decay tank 364 can perform the steps independently with the other decay tanks.
  • the third decay tank 364 may perform the steps alternatively, simultaneously, sequentially, chronologically, and/or in rotation among the other decay tanks.
  • each tank since each tank may operate independently, it can be shut down for maintenance separately. This also enables the process to be carried out with higher capacity when needed while providing ease of maintenance.
  • the embodiment can be further realized into providing a fourth decay tank, a fifth decay tank and so forth.
  • the urine specimen for the experiments were prepared based on a 1 : 10 scale simulation of the practical situation in which a normal person may urinate as much as 300 mL of urine and a single toilet flush is about 3L. Each specimen was therefore prepared by adding 300mL water to 30 mL urine.
  • Three batches of sodium iodide solution were prepared by dissolving 7.5 gm sodium iodide (GCE Laboratory Chemical, ETSP, BP, Ph Eur Lot # 6128) in 50 mL water so that 10 mL of the solution will contain 1500 gm (10 meq) sodium iodide.
  • Three batches of silver nitrate solution were prepared by dissolving 35 gm silver nitrate (GCE laboratory Chemical, ACS grade, Lot # 6228) in 50 mL water so that 10 mL of the solution will contain 7000 mg (41 meq) silver nitrate.
  • Each urine specimen was divided into the control arm and the experiment arm.
  • To the experiment arm was added 10 mL of sodium iodide solution (10 meq of iodide).
  • To both the control arm and experiment arm was added 10 mL of silver nitrate solution (41 meq of silver) afterward.
  • the weight of silver iodide formed was calculated by subtracting the weight of control arm precipitate (silver chloride) from the weight of experiment arm (silver chloride + silver iodide).
  • the meq of iodide removed from urine was calculated by dividing the weight of silver iodide by the molecular weight of silver iodide (234.77). The iodide removal efficiency was then calculated using the following formula:
  • the removal efficiency meq of iodide ion removed from urine x 100% / meq of iodide ion added (10 meq)
  • the concentration of the sodium iodide solution prepared are shown in Table 5.
  • the amount of iodide added to the urine specimen ranged from 10.07 meq to 10.21 meq.
  • the average was 10.14 ⁇ 0.099 meq.
  • the concentration of silver nitrate solution prepared are shown in Table 6.
  • the amount of silver added to the urine specimen ranged from 41.27 meq to 41.44 meq. The average was 41.39 ⁇ 0.078 meq.
  • Table 6 The concentration of the prepared silver nitrate solution

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  • Removal Of Specific Substances (AREA)

Abstract

A process for removing radioactive ions present in a liquid comprising the steps of opening a first precipitant inlet for introducing a precipitant to the liquid in a first treatment tank, mixing the precipitant with the liquid by starting a first mixing device to form a first suspension by precipitation reaction involving the precipitant and the liquid, settling the first suspension after stopping the first mixing device and closing the first precipitant inlet for separating the first suspension into a first supernatant layer and a first precipitate layer, detecting radioactivity in the first supernatant layer using a first radiation probe, opening a first supernatant outlet for draining the first supernatant layer out of the first treatment tank, opening a first precipitate outlet for disposing the first precipitate layer out of the first treatment tank.

Description

PROCESS AND SYSTEM FOR REMOVING RADIOACTIVE IONS PRESENT IN A
LIQUID
TECHNICAL FIELD
The present disclosure relates to a process for removing radioactive ions present in a liquid. Particularly, the present disclosure relates to a process for removing radioactive ions present in a urine through the formation of insoluble substance by adding a precipitant to the urine.
BACKGROUND
Various radioactive isotopes have been studied and utilized for clinical applications. Many iodine radioisotopes, such as 131I, 124I, 123I, and 125I, are routinely used in diagnosis and treatment of diseases such as thyroid cancer and hyperthyroidism. Furthermore, the iodine radioisotopes can be attached to other chemicals forming radioactive tracers which are useful in Positron Emission Tomography (PET) and Single Photo Emission Tomography (SPECT) for diagnosis of many cancers.
Concurrently, the lutetium radioisotope, 177Lu, also has various medical uses such as treatment of cancer and palliation of bone pain due to cancer metastasis. The lutetium radioisotope is also attached to other chemicals. For example, 177Lu is routinely conjugated to PSMA, DOTATATE, DOTATOC, DOTANOC, MDP, HMDP, and/or HEDP for treatment of recurrent prostate cancer, neuroendocrine tumor, and/or bone pain palliation.
Once patients have been administered with the radioisotopes and subjected to diagnosis or therapy, they will excrete these radioisotopes through their urine. For 131I, when the amount of radioactivity administered is higher than 30mCi (11 lOMBq), the patients will be hospitalized. In other treatments using radioisotopes such as 177Lu, patients will be required to stay in a clinic for under observation for at least 5 to 6 hours. During this period, it is unavoidable that the patients will urinate. The relevant laws and regulations in many countries set discharge limits that control radioactive substance to be discharged to the sewage or landfill. In addition, such radioactive waste will have major hazardous impact on the environment and human health and well-being if released without proper treatment. As such, health facilities are required to implement appropriate measures to manage the radioisotope waste produced from the patients.
The general practice is to apply a store-and-decay method in which patients’ urine is to be collected and stored in a specific environment for a period of time equivalent to at least 10 half-lives before being discharged to public sewage. Each radioisotope has a specific half-life and some radioisotopes have significantly longer half-lives than the others. For example, 177Lu has a half-life of 6 days and 131I has a half-live of 8 days, while 125I has a half-life of 60 days. Accordingly, urine from the patients administered with 177LU will have to be stored for at least 60 days, urine from the patients administered with 131I for at least 80 days, and urine from the patients administered with 125I for at least 600 days. In addition to the possible long storage time, the storage conditions include extensive spaces, complex monitoring protocols, and hygienist treatment for the urine storage tanks. A typical storage system would require 3 storage tanks of more than 5000 L, each provided with various equipment, such as radiation monitor, pH monitor, liquid level monitor, and gas trap.
The increasing usage of radioisotopes nowadays leads to an increasing amount of radioisotope waste being produced. This results in more demanding storage conditions that could possibly exceed financial and/or storage capabilities of some health facilities.
Accordingly, various methods and systems for removing radioisotopes from urine, before discharging it into sewers, have been developed to reduce the need of space consuming storage system in health facilities. An efficient method for the removal of radioactive ions from urine will be beneficial for health facilities as well as the field of medicine.
One of the methods involves using strong chemicals such as hydrochloric acid and lengthy procedures such as adjusting pH, heating to 40°C and passing through silver chloride column (Fletcher K, “The Fractionation of urinary iodine”, Biochemical Journal , 1957; 67(1): 140-146). The method described is only carried out in a small portion which is insufficient for a practical waste load and it can be disadvantageously difficult to implement as a system since it would require numerous components for the procedures.
Benes et al. (U.S. Patent 6,773,686, filed on August 7, 1978) describes an apparatus for the removal of radioactive iodine from a liquid by adding a carrier substance, such as potassium iodide, and a solution of a silver salt to the liquid. The process develops an insoluble, radioactive precipitate which is removed from the urine by the use of a filtration unit. This process requires a production of a filtration unit which in turn increases the cost of the system. Additionally, the filtration unit would require manual replacement after a relatively short period of time.
Jeon et al. (U.S. Patent Application US2017/0305760, filed on April 21, 2017) discloses a process and a device for removing iodide using gold particles. One embodiment describes the process of contacting the urine with the gold particles using a column or a membrane filter. This process requires a large size column into which gold particles are poured. The requirement for the gold particles as one of the main components can result in an expensive system.
The present invention alternatively provides a faster and/or cheaper method of removing radioactive ions from a liquid which can minimize the space and monitoring requirement of the store-and-decay method. The invention can also replace the conventional methods for removing radioactivity which can be relatively expensive.
SUMMARY OF INVENTION
A process for removing radioactive ions present in a liquid comprising the steps of opening a first precipitant inlet for introducing a precipitant to the liquid in a first treatment tank, mixing the precipitant with the liquid by starting a first mixing device to form a first suspension by precipitation reaction involving the precipitant and the liquid, settling the first suspension after stopping the first mixing device and closing the first precipitant inlet for separating the first suspension into a first supernatant layer and a first precipitate layer, detecting radioactivity in the first supernatant layer using a first radiation probe, opening a first supernatant outlet for draining the first supernatant layer out of the first treatment tank, opening a first precipitate outlet for disposing the first precipitate layer out of the first treatment tank and using a controller which is in electrical communication with the first precipitant inlet, the first mixing device, the first radiation probe, and the first supernatant outlet, to control the first mixing device, the first precipitant inlet, the first radiation probe, and the first supernatant outlet.
The step of mixing includes providing a turbine or providing a diffuser for introducing air, the air being supplied from an air compressor via an air supply line.
The process further comprises the step of reacting the first precipitate layer by introducing a desludging agent to the first precipitate layer. The process further comprises the step of disposing the reacted first precipitate layer away from the first treatment tank via the first precipitate outlet. The step of reacting the first precipitate layer includes introducing an acidic solution as the desludging agent.
The step of opening the first precipitant inlet for introducing the precipitant to the liquid includes providing a supply tank in fluid communication with the first treatment tank for holding the precipitant or includes introducing any one of metal solution and anion solution as the precipitant.
The step of introducing the precipitant to the liquid includes providing at least one of nitrate, chloride, bromide, carbonate, and bicarbonate of any one of lead (Pb), silver (Ag), and Mercury (Hg) as the metal solution or includes providing at least one of oxalate, carbonate, hydroxide, fluoride, phosphate, and oxide solution as the anion solution.
The radioactive ions include any of iodide ion and lutetium ion.
The process further comprises the step of providing a second treatment tank for opening a second precipitant inlet for introducing the precipitant to the liquid in the second treatment tank, wherein the precipitant is introduced from the supply tank; mixing the precipitant with the liquid by starting a second mixing device to form a second suspension by precipitation reaction involving the precipitant and the liquid; settling the second suspension after stopping the second mixing device and closing the second precipitant inlet or separating the second suspension into a second supernatant layer and a second precipitate layer; detecting radioactivity in the second supernatant layer using a second radiation probe; opening a second supernatant outlet for draining the second supernatant layer out of the second treatment tank; opening a second precipitate outlet for disposing the second precipitate layer out of the second treatment tank; and using the controller which is in electrical communication with the second precipitant inlet, the second mixing device, the second radiation probe, and the second supernatant outlet, to control the second mixing device, the second precipitant inlet, the second radiation probe, and the second supernatant outlet. The second treatment tank is in fluid communication with the first treatment tank and the first supernatant outlet; the desludging agent is an acidic solution; and the precipitant is any one of metal solution and anion solution.
A system for removing radioactive ions present in a liquid comprising a first precipitant inlet for opening to introduce a precipitant to the liquid and closing to discontinue introduction of the precipitant to the liquid, a first treatment tank for forming a first suspension by precipitation reaction involving the precipitant and the liquid and settling the first suspension to separate the first suspension into a first supernatant layer and a first precipitate layer, a first mixing device disposed in the first treatment tank for mixing the precipitant with the liquid, a first radiation probe disposed in the first treatment tank for detecting radioactivity in the first supernatant layer, a first supernatant outlet disposed on the first treatment tank for draining the first supernatant layer out of the first treatment tank, a first precipitate outlet disposed on the first treatment tank for disposing the first precipitate layer out of the first treatment tank and a controller which is in electrical communication with the first precipitant inlet, the first mixing device, the first radiation probe, and the first supernatant outlet for controlling the first precipitant inlet, the first mixing device, the first radiation probe, and the first supernatant outlet in sequential order.
The first mixing device includes a turbine or includes a diffuser for introducing air, wherein the diffuser is in fluid communication with an air compressor and an air supply line for supplying the air. A desludging agent is introduced to the first precipitate layer for reacting the first precipitate layer. The reacted first precipitate layer is disposed away from the first treatment tank via the first precipitate outlet. The desludging agent is an acidic solution.
The system further comprises a supply tank for holding the precipitant, wherein the supply tank is in fluid communication with the first treatment tank for introducing the precipitant to the liquid.
The precipitant is any one of metal solution and anion solution. The metal solution is at least one of nitrate, chloride, bromide, carbonate, and bicarbonate of any one of lead (Pb), silver (Ag), and Mercury (Hg). The anion solution is at least one of oxalate, carbonate, hydroxide, fluoride, phosphate, and oxide solution. The radioactive ions include any of iodide ion and lutetium ion.
The system further comprises a second precipitant inlet for opening to introduce the precipitant from the supply tank to the liquid and closing to discontinue introduction of the precipitant to the liquid; a second treatment tank in fluid communication with the first treatment tank and the first supernatant outlet for forming a second suspension by precipitation reaction involving the precipitant and the liquid and settling the second suspension to separate the second suspension into a second supernatant layer and a second precipitate layer; a second mixing device disposed in the second treatment tank for mixing the precipitant with the liquid; a second radiation probe disposed in the second treatment tank for detecting radioactivity in the second supernatant layer; a second supernatant outlet disposed on the second treatment tank for draining the second supernatant layer out of the second treatment tank; a second precipitate outlet disposed on the second treatment tank for disposing the second precipitate layer out of the second treatment tank; wherein the controller is in electrical communication with the second precipitant inlet, the second mixing device, the second radiation probe, and the second supernatant outlet for controlling the second precipitant inlet, the second mixing device, the second radiation probe, and the second supernatant outlet in sequential order; wherein the desludging agent is an acidic solution; and the precipitant is any of metal solution and anion solution. BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present disclosure are described herein with reference to the drawings in which:
Figure 1 shows a schematic diagram of a system for removing radioactive ions present in a liquid according to an embodiment of the present invention
Figure 2 shows a flowchart of the process according to the embodiment of the present invention as shown in Figure 1.
Figure 3 shows a schematic diagram of the system according to another embodiment of the present invention.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. Illustrative embodiments described in the detailed description, drawings and claims are not meant to be limiting. Other embodiments can be utilized, and other changes can be made, without departing from the spirit or scope of the subject matter presented herein.
Unless specified otherwise, the terms “comprising,” “comprise,” “including” and “include” used herein, and grammatical variants thereof, are intended to represent “open” or“inclusive” language such that they include recited elements but also permit inclusion of additional, un-recited elements.
The description herein may be, in certain portions, explicitly or implicitly written as algorithms and/or functional operations that operate on data within a computer memory or an electronic circuit. These algorithmic descriptions and/or functional operations are usually used by those skilled in the information/data processing arts for efficient description. An algorithm is generally relating to a self-consistent sequence of steps leading to a desired result. The algorithmic steps can include physical manipulations of physical quantities, such as electrical, magnetic, or optical signals capable of being stored, transmitted, transferred, combined, compared, and otherwise manipulated. Additionally, when describing some embodiments, the disclosure may have provided a method and/or process as a particular sequence of steps. However, unless otherwise required, it will be appreciated the method or process should not be limited to the particular sequence of steps disclosed. Other sequences of steps may be possible. The particular order of the steps disclosed herein should not be construed as undue limitations. Unless otherwise required, a method and/or process disclosed herein should not be limited to the steps being carried out in the order written. The sequence of steps may be varied and still remain within the scope of the disclosure.
Further, terms such as "about", "approximately" and the like whenever used, typically means a reasonable variation, for example a variation of +/- 5% of the disclosed value, or a variance of 4% of the disclosed value, or a variance of 3% of the disclosed value, a variance of 2% of the disclosed value or a variance of 1% of the disclosed value.
As shown in Figure 1, embodiments described herein provide a system 100 for removing radioactive ions, such as radioactive iodine and radioactive lutetium, present in a liquid. The liquid includes urine excreted by patients administered with radioactivity, such as iodine and lutetium.
The system 100 comprises a reagent inlet 101, also called as a precipitant inlet and/or a supply inlet, which can be opened to introduce a precipitant/reagent to the urine. The reagent inlet 101 can also be closed to stop the introduction of the precipitant to the urine as appropriate.
The system 100 further comprises a treatment tank/decay tank 102 where a suspension (not shown) can be formed by precipitation reaction involving the precipitant and the urine. A mixing device 104 is installed in the decay tank 102 for mixing the precipitant with the urine in order to facilitate the precipitation reaction. The suspension is settled in the decay tank 102 and thus is separated into a supernatant 106 and a precipitate/sludge 108. A radiation probe 110 is further installed in the decay tank 102 to determine the radioactivity of the supernatant 106. Additionally a supernatant outlet 112 is placed on the decay tank 102 for removing the supernatant 106 from the decay tank 102, and a precipitate outlet 1 14 is placed on the decay tank 102 for removing the precipitate 108 from the decay tank 102.
In addition, a controller 1 15 is in electrical communication, such as wired connection, with the reagent inlet 101, the mixing device 104, the radiation probe 1 10, and the supernatant outlet 1 12 for controlling the functions of the components.
Figure 2 illustrates a process 200 for removing radioactive ions present in the urine according to the embodiment in Figure 1.
At step 201, the reagent inlet 101 is opened in order to add the precipitant to the urine in the decay tank 102. At step 202, the precipitant is mixed with the urine by activating the mixing device 104. As a result, the suspension is formed by precipitation reaction involving the precipitant and the urine. At step 203, the mixing device 104 is stopped and the reagent inlet 101 is closed so that the suspension can settle. Accordingly, the suspension is separated into the supernatant 106 and the precipitate 108. At step 204, the radiation probe 1 10 detects/measures radioactivity of the supernatant 106. At step 205, once the supernatant 106 is determined to be non-radioactive, the supernatant outlet 1 12 is opened in order to drain the supernatant 106 out of the decay tank 102. At step 206, the precipitate outlet 1 14 is used for removing the precipitate 108 out of the decay tank 102.
At step 207, the controller 1 15 is used for controlling the reagent inlet 101, the mixing device 104, the radiation probe 1 10, and the supernatant outlet 1 12. With the use of the controller 1 15, the steps 202, 203, 204, and 205 are performed in sequential order.
In one embodiment, the radioactive ions include an iodide ion. The radioactive liquid includes any iodide solution and urine excreted by the patients administered with at least one type of isotopes of iodine. The isotopes of iodine include non-radioactive isotopes and radioactive isotopes (also known as radioisotope, radionuclide, and radioactive nuclide) such as 108I, 109I, 110I, 1UI, 112I, 113I, 114I, 114mI, 115I, 116I, 116mI, 117i
118y 118my 119y 120mly 120m2y 121y 121my 122y 123y 124y 125y 126y 127y 128y 128mly 128m2y 129y 130y 130mly 130m2y 130m3y 130m4y 131y 132y 132my 133y 133mly 133m2y 134y 134my 135y 136y
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
Figure imgf000011_0001
In another embodiment, the radioactive ions include a lutetium ion. The radioactive liquid includes any lutetium solution and urine excreted by the patients administered with at least one type of isotopes of lutetium. The isotopes of lutetium include non radioactive isotopes and radioactive isotopes such as 150Lu, 150mLu, 151Lu, 151mLu, 152Lu, i53 Lu, 153mlLu, 153m2Lu, 153m3Lu, 154LU, 154mlLu, 154m2Lu, 155Lu, 155mlLu, 155m2Lu, 156Lu, 156mLu, 157LU, 157mLu, 158LU, 159LU, 159mLu, 160Lu, 160mLu, 161Lu, 161mLu, 162Lu, 162mlLu, 162m2Lu, 163LU, 164LU, 165LU, 166LU, 166mlLu, 166m2Lu, 167Lu, 167mLu, 168Lu, 168mLu, 169Lu, 169mLu, 170LU, 170mLu, 171LU, 171mLu, 172LU, 172mlLu, 172m2Lu, 172m3Lu, 172m4Lu, 173Lu, 173mLu, 174LU, 174mlLu, 174m2Lu, 174m3Lu, 175Lu, 175mlLu, 175m2Lu, 176Lu, 176mLu, 177Lu, 177mlLu, 177m2Lu, 177m3Lu, 177m4Lu, 178LU, 178mLu, 179Lu, 179mLu, 180Lu, 180mlLu, 180m2Lu, 181LU, 182LU, 183LU, and 184Lu.
The decay tank 102 is connected with an external source 116 via an inlet channel 118 and an inlet valve 120.
The urine is introduced to the decay tank 102 from the external source 116 where the external source 116 is a means of collecting urine including a receptacle provided at a conventional toilet and a separation toilet (also known as urine-diverting toilet).
A level sensor 122 capable of detecting a substance in a container is installed in the decay tank 102 and is in electrical communication with the controller 115.
The level sensor 122 detects the level of the liquid in the decay tank 102 whether the level has reached a certain threshold, e.g. the urine from the external source 116 has been introduced into the decay tank 102, then sends the signal to the controller 115.
Preferably, the step 201 includes providing a supply tank/reagent tank 124 for holding the precipitant/reagent. The reagent tank 124 is in fluid communication or connected with the decay tank 102 via the reagent inlet 101 and a supply valve/reagent valve 128. Moreover, the reagent inlet 101 is connected with a supply pump/reagent pump 130 in order to facilitate the conveyance/transportation of the precipitant in the reagent tank 124 to the decay tank 102. The reagent valve 128 and the reagent pump 130 are in electrical communication with the controller 115.
The signal from the level sensor 122 is received by the controller 115 and the controller 115 supplies an electrical signal to activate the reagent pump 130 and the reagent valve 128. The activation of the reagent pump 130 and the reagent valve 128 results in the introduction of the precipitant to the decay tank 102 as well as the urine present in the decay tank 102 via the reagent inlet 101.
The mixing device 104 includes any one of applicable industrial mixers, such as a turbine, where the mixing device 104 is installed inside the decay tank 102 and in electrical communication with the controller 115.
Accordingly, the controller determines if step 202 should be commenced (e.g. after the introduction of the precipitant to the decay tank 102 is completed) and supplies an electrical signal to the mixing device 104, e.g. a turbine, to activate the operation thereof.
Alternatively, the mixing device 104 is a diffuser or similar means capable of introducing air to a defined space. The mixing device 104, e.g. a diffuser, is in fluid communication with at least one air compressor 132 via an air supply line/air channel 134. The air channel 134 is in fluid communication with an air supply/air valve 136. Furthermore, an air vent 138 is provided at the decay tank 102, preferably at the top of the decay tank 102 connecting to outside environment. The air compressor 132 and the air valve 136 are in electrical communication with the controller 115.
Accordingly, the controller determines if step 202 should be commenced (e.g. after the introduction of the precipitant to the decay tank 102 is completed) and sends an electrical signal to the air compressor 132 and the air valve 136 to activate the operation thereof. As a result, air is drawn by the air compressor 132 from outside environment and introduced to the mixing device 104 via the air channel 134 and air valve 136. The air is further introduced to the decay tank 102 by the mixing device 104, e.g. a diffuser, located preferably at the bottom of the decay tank 102, moves upwards through the substance in the decay tank 102, and is ventilated to outside environment via the air vent 138.
The mixing of the precipitant and the liquid helps to break down an organic element in the liquid, e.g. urea from urine, and enabling the production of the suspension. In one embodiment, the step 202 enables or results in producing the suspension by precipitation reaction involving the precipitant and the urine in step 203.
After stopping the mixing device 104 and closing the reagent inlet 101, the suspension is allowed to stand for a certain period of time to separate the suspension into the supernatant 106 and the precipitate 108. The step is indicated as step 203.
The step 203 is effected by sending an electrical signal from the controller 115 to the mixing device 104, e.g. a turbine, to stop the mixing device 104 and waiting for a set period of time.
Alternatively, the step 203 is effected by sending an electrical signal from the controller 115 to the air valve 136 and the air compressor 132 so that air no longer flows or circulates inside the decay tank 102 and waiting for a set period of time.
Preferably, the step of stopping the mixing device 104 is carried out automatically by the controller 115, for example, the controller 115 sends an electrical signal to stop the mixing device 104 after a predetermined period of time has expired. The predetermined period of time is programmed in the controller.
The set period of time is the time required for at least 50 percent of the suspension to separate into the supernatant 106 and the precipitate 108. The set period of time is generally in the range of 0.5 to 2 hours.
The decay tank 102 is provided with the radiation probe 110 for detecting the radioactivity of the supernatant 106 in the decay tank 102. The radiation probe 110 is in electrical communication with the controller 115. A tank pump 140 is provided in the decay tank 102 where the supernatant 106 is for draining the supernatant 106 out of the decay tank 102. The tank pump 140 is in fluid communication with the supernatant outlet 112 and is in electrical communication with the controller 115. For example, the tank pump 140 receives the supernatant 106 directly from the decay tank 102 and further conveys the supernatant 106 via the supernatant outlet 112.
Alternatively, the supernatant outlet 112 is provided at the location where the supernatant 106 is in the decay tank 102 for draining the supernatant 106 out of the decay tank 102. The supernatant outlet 112 is in fluid communication with the tank pump 140 and the tank pump 140 is in electrical communication with the controller 115. For example, the supernatant outlet 112 receives the supernatant 106 from the decay tank 102 and conveys the supernatant 106 to the tank pump 140.
In addition, the supernatant outlet 112 for draining the supernatant 106 out of the decay tank 102 can be in fluid communication with a supernatant valve 144. The supernatant valve 144 is in electrical communication with the controller 115.
Accordingly, the radiation probe 110 detects radioactivity of the supernatant 106 in the decay tank 102 whether the radioactivity has fallen below a threshold, e.g. the activity level of 0.5 mSv (the background radiation), then sends the signal to the controller 115. Once the signal is received by the controller 115, the controller 115 sends an electrical signal to activate the tank pump 140 and the supernatant valve 144. The activation of the tank pump 140 and the supernatant valve 144 results in the drainage of the supernatant 106 away from the decay tank 102.
Additionally, any one of the decay tank 102, the supernatant outlet 112, and the supernatant valve 144 or the combinations thereof are in fluid communication with sewage.
Accordingly, the supernatant 106 can be drained away from the decay tank 102 to sewage. The supernatant outlet 112 can be further in fluid communication with an outlet radiation probe 146 where the outlet radiation probe 146 is in electrical communication with the controller 115.
In addition, the process further comprises the step of preventing the radioactive supernatant from draining away from the decay tank 102. The outlet radiation probe 146 detects radioactivity of the supernatant 106 drained away from the decay tank 102 via the supernatant outlet 112 whether the radioactivity has reached a threshold, e.g. the activity level of 0.5 mSv (the background radiation), then sends the signal to the controller 115. Once the signal is received by the controller 115, the controller 115 sends an electrical signal to shut the supernatant valve 144 and the tank pump 140 in order to prevent the drainage of the radioactive supernatant 106.
The controller 115 includes controller and electronic circuit capable of running a control program and sending electrical signals to devices. For example, the controller 115 is a programmable logic controller (PLC). Alternatively, the controller 115 is a relay circuit of electromechanical type or solid-state type, and further, the controller 115 is a fully electronic control circuit or a mixed control circuit.
The process further comprises the step of reacting the precipitate 108, also called desludging, by introducing a desludging agent to the precipitate 108. The introduction of the desludging agent may be carried out manually via a manual opening of a valve or by using the controller 115.
Preferably, the desludging agent is an acidic solution which includes, but not limited to, hydrochloric acid at the concentration in the range of 5 % to 30%.
The process further comprises the step of disposing the reacted precipitate away from the decay tank 102 via the precipitate outlet 114. The precipitate outlet 114 is generally located at the bottom of the decay tank 102, preferably in fluid communication with at least one valve. The disposal of the reacted precipitate may be carried out manually via a manual opening of a valve or by using the controller 115. Considering the common loads for health facilities of about 200 L per day up to 1000 L per day, the steps of reacting the precipitate and disposing the reacted precipitate should only occur once between every 180 days to every 360 days based on the load. The comparative designs of the treatment tank may allow only for 90 days which in turn limits the capacity. As such, the decay tank 102 of an embodiment of the present invention can keep more liquid for a longer period of time without requiring the frequent disposal due to volume or radioactivity limits. Additionally, such longer period of time can advantageously decrease the radioactivity of the disposed precipitate, for example, 133I present in the liquid may go through over forty half-lives which reduces radioactivity to background radiation.
Generally, a maintenance outlet 148 is provided at the decay tank 102 which is accessed manually for maintenance purposes. The maintenance outlet 148 includes a manhole/maintenance hole with or without a fluid communication with a valve.
At step 201, the precipitant includes a metal solution and/or anion solution.
Preferably, the metal solution is at least one of nitrate, chloride, bromide, carbonate, and bicarbonate of any one of lead (Pb), silver (Ag), and Mercury (Hg) where the metal solution is used for removing iodide ion in urine.
Preferably, the anion solution is at least one of oxalate, carbonate, hydroxide, fluoride, phosphate, and oxide solution where the anion solution is used for removing lutetium ion in urine.
More preferably, the metal solution is silver nitrate solution at the concentration in the range of 500 to 800 mg/mL.
For instance, a silver nitrate solution is added to urine from the patients administered with radioactive iodine. Such process causes a reaction creating a formation of an insoluble silver iodide compound (also called as precipitate) which is radioactive and a supernatant urine which is non-radioactive and thus can be discharged into sewage. Similarly, a solution containing the anion is added to the urine from the patients administered with radioactive lutetium. The process causes a reaction creating a formation of an insoluble lutetium compound (also called as precipitate) which is radioactive and a supernatant urine which is non-radioactive and thus can be discharged into sewage.
As shown in Figure 3, embodiment described herein provide a system 300 comprises a second treatment/second decay tank 350 connected with a first decay tank 302 (comparable to the decay tank 102 of the system 100) and the supernatant outlet 312 (comparable to the supernatant outlet 112 of the system 100).
The system 300 further comprises a second reagent inlet 351 which can be opened to introduce the precipitant from the supply tank 324 to the urine and closing to discontinue introduction of the precipitant to the urine. The second reagent inlet 351, similar to the reagent inlet 101 of the system 100, can also be closed to stop the introduction of the precipitant to the urine as appropriate.
Accordingly, a second suspension is formed in the second decay tank 350 by precipitation reaction involving the precipitant and the urine. A second mixing device 352 is installed in the second decay tank 350 for mixing the precipitant with the urine the second suspension is settled to separate the second suspension into a second supernatant 354 and a second precipitate 356.
A second radiation probe 358 is installed inside the second decay tank 350 to determine radioactivity of the second supernatant 354; a second supernatant outlet 360 is placed on the second decay tank 350 for removing the second supernatant 354 from the second decay tank 350; and a second precipitate outlet 362 is placed on the second decay tank 350 for removing the second precipitate 356 from the second decay tank 350.
Similar to the aforementioned embodiments, the desludging agent is an acidic solution and the precipitant is a metal solution and/or anion solution based on the radioactive element present in the urine. Moreover, a controller 315 (comparable to the controller 115 of the system 100) is in electrical communication with the second mixing device 352, the second radiation probe 358, and the second supernatant outlet 360 for controlling the function of the components.
Additionally, embodiments described herein comprise the steps of opening the second reagent inlet 351 for introducing the precipitant to the liquid in the second decay tank 350, wherein the precipitant is introduced from the supply tank 324; mixing the precipitant with the liquid using the second mixing device 352 to form a second suspension by precipitation reaction involving the precipitant and the liquid; settling the second suspension after stopping the second mixing device 352 and closing the second reagent inlet 351 for separating the second suspension into the second supernatant 354 and the second precipitate 356; detecting radioactivity in the second supernatant 354 using the second radiation probe 358; opening the second supernatant outlet 360 for draining the second supernatant 354 out of the second decay tank 350; opening the second precipitate outlet 362 for disposing the second precipitate 356 out of the second decay tank 350; using the controller 315 whereby the second decay tank 350 is in fluid communication with the decay tank 302 and the supernatant outlet 312.
The steps of mixing, settling the second suspension, detecting radioactivity, and opening the second supernatant outlet are performed in sequential order by the means of the controller 315.
The second decay tank 350 can perform the steps independently with the decay tank 302. In addition, the second decay tank 350 may perform the steps alternatively, sequentially, chronologically, and/or simultaneously with the first decay tank 302. Since each tank may operate independently, it can be shut down for maintenance separately. This enables the process to be carried out with higher capacity when needed while providing ease of maintenance.
The embodiment can be further realized into providing a third decay tank 364. Similarly, the third decay tank 364 can perform the steps independently with the other decay tanks. The third decay tank 364 may perform the steps alternatively, simultaneously, sequentially, chronologically, and/or in rotation among the other decay tanks. Similarly, since each tank may operate independently, it can be shut down for maintenance separately. This also enables the process to be carried out with higher capacity when needed while providing ease of maintenance.
Furthermore, the embodiment can be further realized into providing a fourth decay tank, a fifth decay tank and so forth.
EXAMPLE
The following are experiments carried out on an embodiment of the invention without in any way limiting scope of the present invention.
Example 1
Experiments were carried out to find iodide removal efficiency of urine specimens using an embodiment of the present invention. Three batches of urine were collected and duplicated experiments were carried out on each batch of urine as illustrated in Table 1.
Table 1 : The experiment model of the urine batches
Figure imgf000019_0001
The urine specimen for the experiments were prepared based on a 1 : 10 scale simulation of the practical situation in which a normal person may urinate as much as 300 mL of urine and a single toilet flush is about 3L. Each specimen was therefore prepared by adding 300mL water to 30 mL urine.
Three batches of sodium iodide solution were prepared by dissolving 7.5 gm sodium iodide (GCE Laboratory Chemical, ETSP, BP, Ph Eur Lot # 6128) in 50 mL water so that 10 mL of the solution will contain 1500 gm (10 meq) sodium iodide. Three batches of silver nitrate solution were prepared by dissolving 35 gm silver nitrate (GCE laboratory Chemical, ACS grade, Lot # 6228) in 50 mL water so that 10 mL of the solution will contain 7000 mg (41 meq) silver nitrate.
Each urine specimen was divided into the control arm and the experiment arm. To the experiment arm was added 10 mL of sodium iodide solution (10 meq of iodide). To both the control arm and experiment arm was added 10 mL of silver nitrate solution (41 meq of silver) afterward.
White precipitate of silver chloride formed immediately when silver nitrate was added to the control arm since urine contains chloride ion. Mixture precipitate of silver chloride and silver iodide formed immediately when silver nitrate was added to the experiment arm which contains 10 meq of iodide ion. The precipitate was collected, air died, and then weighted (A&D Compact Scale, model HL-100).
The weight of silver iodide formed was calculated by subtracting the weight of control arm precipitate (silver chloride) from the weight of experiment arm (silver chloride + silver iodide).
The meq of iodide removed from urine was calculated by dividing the weight of silver iodide by the molecular weight of silver iodide (234.77). The iodide removal efficiency was then calculated using the following formula:
The removal efficiency = meq of iodide ion removed from urine x 100% / meq of iodide ion added (10 meq)
The experiment designs of urine batch 1, urine batch 2, and urine batch 3 are shown in Table 2, Table 3, and Table 4, respectively.
Table 2: The experiment design of urine batch 1
Figure imgf000020_0001
Figure imgf000021_0001
Table 3: The experiment design of urine batch 2
Figure imgf000021_0002
Table 4: The experiment design of urine batch 3
Figure imgf000022_0001
The concentration of the sodium iodide solution prepared are shown in Table 5. The amount of iodide added to the urine specimen ranged from 10.07 meq to 10.21 meq. The average was 10.14 ± 0.099 meq.
Table 5: The concentration of the prepared sodium iodide solution
Figure imgf000022_0002
The concentration of silver nitrate solution prepared are shown in Table 6. The amount of silver added to the urine specimen ranged from 41.27 meq to 41.44 meq. The average was 41.39 ± 0.078 meq. Table 6: The concentration of the prepared silver nitrate solution
Figure imgf000023_0001
The detailed data is further illustrated in Table 7, Table 8, and Table 9. The amount of iodide removed as silver iodide precipitate ranged from 5.67 meq to 7.97 meq (N=6). The average was 7.16 ± 0.82 meq (N=6).
Table 7: The detailed experimental data of urine batch 1
Figure imgf000023_0002
Table 8: The detailed experimental data of urine batch 2
Figure imgf000024_0001
Table 9: The detailed experimental data of urine batch 3
Figure imgf000024_0002
The iodide removal efficiency obtained the experiment of all urine batches were summarized in Table 10. Table 10: The iodide removal efficiencies of urine batch 1, urine batch 2, and urine batch 3
Figure imgf000025_0001
As shown in Table 10, the removal efficiency ranged from 55.50% to 78.55% (N=6). The average iodide removal efficiency was 70.73 ± 8.30% (N=6)
It will be appreciated by a person skilled in the art that other variations and/or modifications may be made to the specific embodiments without departing from the scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Claims

1. A process for removing radioactive ions present in a liquid comprising the steps of:
a) opening a first precipitant inlet for introducing a precipitant to the liquid in a first treatment tank;
b) mixing the precipitant with the liquid by starting a first mixing device to form a first suspension by precipitation reaction involving the precipitant and the liquid; c) settling the first suspension after stopping the first mixing device and closing the first precipitant inlet for separating the first suspension into a first supernatant layer and a first precipitate layer;
d) detecting radioactivity in the first supernatant layer using a first radiation probe;
e) opening a first supernatant outlet for draining the first supernatant layer out of the first treatment tank;
f) opening a first precipitate outlet for disposing the first precipitate layer out of the first treatment tank; and
g) using a controller in electrical communication with the first precipitant inlet, the first mixing device, the first radiation probe, and the first supernatant outlet;
wherein the controller controls the first mixing device, the first precipitant inlet, the first radiation probe, and the first supernatant outlet whereby the steps b), c), d), and e) are performed in sequential order.
2. The process as claimed in claim 1, wherein the step of mixing includes providing a turbine.
3. The process as claimed in claim 1, wherein the step of mixing includes providing a diffuser for introducing air, the air being supplied from an air compressor via an air supply line.
4. The process as claimed in claim 1, further comprising a step of reacting the first precipitate layer by introducing a desludging agent to the first precipitate layer.
5. The process as claimed in claim 4, further comprising a step of disposing the reacted first precipitate layer away from the first treatment tank via the first precipitate outlet.
6. The process as claimed in claim 4, wherein the step of reacting the first precipitate layer includes using an acidic solution as the desludging agent.
7. The process as claimed in claim 1, wherein the step of opening the first precipitant inlet for introducing the precipitant to the liquid includes providing a supply tank in fluid communication with the first treatment tank for holding the precipitant.
8. The process as claimed in claim 1, wherein the step of opening the first precipitant inlet for introducing the precipitant to the liquid includes using any one of metal solution and anion solution as the precipitant.
9. The process as claimed in claim 8, wherein the step of using any one of metal solution as the precipitant includes using at least one of nitrate, chloride, bromide, carbonate, and bicarbonate of any one of lead (Pb), silver (Ag), and Mercury (Hg) as the metal solution.
10. The process as claimed in claim 8, wherein the step of using any one of anion solution as the precipitant includes using at least one of oxalate, carbonate, hydroxide, fluoride, phosphate, and oxide solution as the anion solution.
11. The process as claimed in claim 1, wherein the radioactive ions include any of iodide ion and lutetium ion.
12. The process as claimed in claim 7, further comprising a step of providing a second treatment tank for performing the steps of:
h) opening a second precipitant inlet for introducing the precipitant to the liquid in the second treatment tank, wherein the precipitant is introduced from the supply tank; i) mixing the precipitant with the liquid by starting a second mixing device to form a second suspension by precipitation reaction involving the precipitant and the liquid;
j) settling the second suspension after stopping the second mixing device and closing the second precipitant inlet or separating the second suspension into a second supernatant layer and a second precipitate layer;
k) detecting radioactivity in the second supernatant layer using a second radiation probe;
l) opening a second supernatant outlet for draining the second supernatant layer out of the second treatment tank;
m) opening a second precipitate outlet for disposing the second precipitate layer out of the second treatment tank; and
n) using the controller in electrical communication with the second precipitant inlet, the second mixing device, the second radiation probe, and the second supernatant outlet;
wherein the controller controls the second mixing device, the second precipitant inlet, the second radiation probe, and the second supernatant outlet whereby the steps i), j), k), and 1) are performed in sequential order;
wherein the second treatment tank is in fluid communication with the first treatment tank and the first supernatant outlet; the desludging agent is an acidic solution; and the precipitant is any one of metal solution and anion solution.
13. A system for removing radioactive ions present in a liquid comprising:
a) a first precipitant inlet for introducing a precipitant to the liquid and stopping the precipitant from going into the liquid;
b) a first treatment tank for forming a first suspension by precipitation reaction involving the precipitant and the liquid and settling the first suspension to separate the first suspension into a first supernatant layer and a first precipitate layer;
c) a first mixing device disposed in the first treatment tank for mixing the precipitant with the liquid;
d) a first radiation probe disposed in the first treatment tank for detecting radioactivity in the first supernatant layer; e) a first supernatant outlet disposed on the first treatment tank for draining the first supernatant layer out of the first treatment tank;
f) a first precipitate outlet disposed on the first treatment tank for disposing the first precipitate layer out of the first treatment tank; and
g) a controller in electrical communication with the first precipitant inlet, the first mixing device, the first radiation probe, and the first supernatant outlet for controlling the first precipitant inlet, the first mixing device, the first radiation probe, and the first supernatant outlet in sequential order.
14. The system as claimed in claim 13, wherein the first mixing device includes a turbine.
15. The system as claimed in claim 13, wherein the first mixing device includes a diffuser for introducing air, wherein the diffuser is in fluid communication with an air compressor and an air supply line for supplying the air.
16. The system as claimed in claim 13, wherein a desludging agent is introduced to the first precipitate layer for reacting with the first precipitate layer.
17. The system as claimed in claim 16, wherein the reacted first precipitate layer is disposed away from the first treatment tank via the first precipitate outlet.
18. The system as claimed in claim 16, wherein the desludging agent is an acidic solution.
19. The system as claimed in claim 13, further comprising a supply tank for holding the precipitant, wherein the supply tank is in fluid communication with the first treatment tank for introducing the precipitant to the liquid.
20. The system as claimed in claim 13, wherein the precipitant is any one of metal solution and anion solution.
21. The system as claimed in claim 20, wherein the any one of metal solution is at least one of nitrate, chloride, bromide, carbonate, and bicarbonate of any one of lead (Pb), silver (Ag), and Mercury (Hg).
22. The system as claimed in claim 20, wherein the any one of anion solution is at least one of oxalate, carbonate, hydroxide, fluoride, phosphate, and oxide solution.
23. The system as claimed in claim 13, wherein the radioactive ions include any of iodide ion and lutetium ion.
24. The system as claimed in claim 17, further comprising:
h) a second precipitant inlet for introducing the precipitant to the liquid and stopping the precipitant from flowing to the liquid;
i) a second treatment tank in fluid communication with the first treatment tank and the first supernatant outlet for forming a second suspension by precipitation reaction involving the precipitant and the liquid and settling the second suspension to separate the second suspension into a second supernatant layer and a second precipitate layer;
j) a second mixing device disposed in the second treatment tank for mixing the precipitant with the liquid;
k) a second radiation probe disposed in the second treatment tank for detecting radioactivity in the second supernatant layer;
1) a second supernatant outlet disposed on the second treatment tank for draining the second supernatant layer out of the second treatment tank;
m) a second precipitate outlet disposed on the second treatment tank for disposing the second precipitate layer out of the second treatment tank;
wherein the controller is in electrical communication with the second precipitant inlet, the second mixing device, the second radiation probe, and the second supernatant outlet for controlling the second precipitant inlet, the second mixing device, the second radiation probe, and the second supernatant outlet in sequential order.
PCT/SG2018/050190 2018-04-17 2018-04-17 Process and system for removing radioactive ions present in a liquid WO2019203725A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4229300A (en) * 1976-01-14 1980-10-21 Ivan Benes Process for the removal of radioactive iodine from a liquid, especially urine, and apparatus to carry out the process
JP2001318190A (en) * 2001-04-02 2001-11-16 Hitachi Ltd Processing method and device for radioactive washing liquid waste
US20100258500A1 (en) * 2008-02-08 2010-10-14 Mitsubishi Heavy Industries, Ltd. Apparatus and method for treating radioactive nitrate waste liquid
JP2012233766A (en) * 2011-04-28 2012-11-29 Ohbayashi Corp Method for removing radioactive substance in radioactive effluent and system for removing radioactive substance in radioactive effluent
CN106683731A (en) * 2016-12-23 2017-05-17 中广核核电运营有限公司 Radioactive waste liquid treating method, radioactive waste liquid treating device and facility

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4229300A (en) * 1976-01-14 1980-10-21 Ivan Benes Process for the removal of radioactive iodine from a liquid, especially urine, and apparatus to carry out the process
JP2001318190A (en) * 2001-04-02 2001-11-16 Hitachi Ltd Processing method and device for radioactive washing liquid waste
US20100258500A1 (en) * 2008-02-08 2010-10-14 Mitsubishi Heavy Industries, Ltd. Apparatus and method for treating radioactive nitrate waste liquid
JP2012233766A (en) * 2011-04-28 2012-11-29 Ohbayashi Corp Method for removing radioactive substance in radioactive effluent and system for removing radioactive substance in radioactive effluent
CN106683731A (en) * 2016-12-23 2017-05-17 中广核核电运营有限公司 Radioactive waste liquid treating method, radioactive waste liquid treating device and facility

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