Metal ion separation technique using pH adjustment and resin-packed columns

Abstract

The waste extraction system includes a settling tank having a waste stream input, a solution input, and a waste stream output, the waste stream input fluidly coupled to an upstream portion of a main waste pathway; a column waste tank; an adsorption column positioned between the settling tank and the column waste tank and fluidly coupled to the settling tank and the column waste tank along the main waste pathway, the adsorption column containing an ion exchange resin and positioned downstream of the settling tank; a solution pathway extending from a solution source to the solution input of the settling tank, the solution source containing an alkaline solution; and a particle filtration unit positioned between the settling tank and the adsorption column and fluidly coupled to the settling tank and the adsorption column.

Description

[Technical Field]

[0001] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT This disclosure was developed with government support under Contract No. DE-NA0004010 awarded by the U.S. Department of Energy. The government has certain rights in this disclosure.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to systems and methods for extracting waste radionuclides, for example, waste radionuclides produced in medical isotope production processes. [Background technology]

[0003] Current technologies for nuclear waste separation involve solvent-based extraction, often referred to as solvent extraction or liquid-liquid extraction. Solvent extraction is a separation technique in which an extractant-containing organic phase is contacted with a metal ion-containing aqueous phase. Upon mixing, the metal ions migrate from the aqueous phase to the organic phase. Despite its popularity in industry, solvent extraction has numerous drawbacks, including challenges associated with phase dissociation, the formation of heavy or "third" phases, and the generation of large amounts of hazardous organic waste. Processes that rely on hazardous aromatic organic solvents pose particular challenges from an environmental standpoint. Many commercial waste haulers have low tolerance for the presence of benzene or other aromatic hydrocarbons in solidified waste.

[0004] Thus, there is a need for improved methods and systems for nuclear waste separation, for example, in medical isotope production processes. Summary of the Invention

[0005] According to a first aspect of the present disclosure, a waste extraction system includes a settling tank having a waste stream input, a solution input, and a waste stream output, the waste stream input fluidly coupled to an upstream portion of a main waste pathway; a column effluent tank; an adsorption column positioned between the settling tank and the column effluent tank and fluidly coupled to the settling tank and the column effluent tank along the main waste pathway, the adsorption column containing an ion exchange resin and positioned downstream of the settling tank; a solution pathway extending from a solution source to a solution input of the settling tank, the solution source containing an alkaline solution; and a particle filtration unit positioned between the settling tank and the adsorption column and fluidly coupled to the settling tank and the adsorption column.

[0006] A second embodiment includes the waste extraction system of the first embodiment, wherein the alkaline solution comprises a NaHCO3 solution, a Na2CO3 solution, or a NaHCO3 / Na2CO3 solution.

[0007] A third embodiment includes the waste extraction system of the first embodiment or the second embodiment, wherein the waste stream input and solution input of the settling tank are each located at a first end of the settling tank, and the waste stream output is located at a second end of the settling tank opposite the first end.

[0008] A fourth embodiment includes the waste extraction system of the third embodiment, wherein the first end of the settling tank is above the second end of the settling tank.

[0009] A fifth embodiment includes the waste extraction system of any of the preceding embodiments, wherein the adsorption column comprises a waste stream input located at a first end of the adsorption column and a waste stream output located at a second end of the adsorption column, the first end of the adsorption column opposite the second end of the adsorption column and the first end of the adsorption column above the second end of the adsorption column.

[0010] A sixth embodiment includes the waste extraction system of any of the previous embodiments, wherein the ion exchange resin comprises ion exchange resin beads with an average diameter in the range of 400 μm to 800 μm.

[0011] A seventh embodiment includes the waste extraction system of any of the previous embodiments, wherein the ion exchange resin comprises a crystalline silicotitanate resin.

[0012] An eighth embodiment includes the waste extraction system of any of the preceding embodiments, wherein the particulate filtration unit comprises a plurality of filters, the plurality of filters comprising an initial filter and a final filter, the initial filter being upstream of the final filter relative to the waste stream output of the settling tank, and the initial filter having a larger mesh size than the final filter.

[0013] A ninth aspect includes the waste extraction system of the eighth aspect, wherein the plurality of filters comprises one or more intermediate filters positioned between the initial filter and the final filter, each of the one or more intermediate filters having a mesh size less than or equal to the mesh size of the initial filter and greater than or equal to the mesh size of the final filter.

[0014] According to a tenth aspect of the present disclosure, a method for radionuclide waste extraction includes directing a waste stream from an upstream portion of a main waste pathway to a settling tank; directing an alkaline solution into the settling tank, thereby increasing the pH of the waste stream and causing precipitation of a first target radionuclide from the waste stream to form a radionuclide precipitate; directing the waste stream from the settling tank to an adsorption column; and adsorbing a second target radionuclide from the settling tank onto an ion exchange resin contained in the adsorption column.

[0015] An eleventh aspect includes the method of the tenth aspect, further comprising the step of harvesting the radionuclide precipitate using a particle filtration unit positioned between and fluidly coupled to the settling tank and the adsorption column.

[0016] A twelfth aspect includes the method of the tenth or eleventh aspects, wherein the first target radionuclide includes strontium-90 and the second target radionuclide includes cesium-137.

[0017] A thirteenth embodiment includes the methods of the tenth to twelfth embodiments, wherein the waste stream in the upstream portion of the main waste pathway has a pH of 0-3, and the waste stream entering the adsorption column has a pH of 7-10.

[0018] A thirteenth embodiment includes the methods of the tenth to twelfth embodiments, wherein the waste stream in the upstream portion of the main waste pathway has a pH of 0-3, and the waste stream entering the adsorption column has a pH of 7-10.

[0019] A fourteenth aspect includes the methods of the tenth to thirteenth aspects, wherein the alkaline solution comprises a NaHCO3 solution, a Na2CO3 solution, or a NaHCO3 / Na2CO3 solution.

[0020] A fifteenth aspect includes the method of any of the tenth through fourteenth aspects, further comprising directing a waste stream from the adsorption column to a column effluent tank, wherein the waste stream entering the column effluent tank comprises treated waste having less than or equal to 0.04 curies per cubic meter of strontium-90 and less than or equal to 1 curie per cubic meter of cesium-137.

[0021] A sixteenth aspect includes the method of the fifteenth aspect, further comprising directing the treated waste from the column waste tank to a waste tank, and then solidifying the treated waste.

[0022] A seventeenth embodiment includes the methods of the tenth through sixteenth embodiments, wherein the waste stream in the upstream portion of the primary waste pathway contains uranium at a gram / liter level that is at least 500 times higher than the gram / liter levels of both strontium-90 and cesium-137.

[0023] An eighteenth embodiment includes the methods of the tenth through seventeenth embodiments, wherein the first target radionuclide comprises barium, cerium, cesium, lanthanum, molybdenum, sodium, neodymium, palladium, praseodymium, rubidium, rhodium, ruthenium, samarium, strontium, yttrium, zirconium, or protactinium, or a combination thereof; and the second target radionuclide comprises barium, cerium, cesium, lanthanum, molybdenum, sodium, neodymium, palladium, praseodymium, rubidium, rhodium, ruthenium, samarium, strontium, yttrium, zirconium, or protactinium, or a combination thereof.

[0024] A nineteenth embodiment includes the method of the tenth through eighteenth embodiments, wherein the waste stream in the upstream portion of the main waste pathway contains 1 gram / liter or more of uranium.

[0025] A twentieth embodiment includes the method of the tenth to nineteenth embodiments, wherein the ion exchange resin comprises ion exchange resin beads having an average diameter in the range of 400 μm to 800 μm.

[0026] These and additional features provided by the embodiments described herein will be more fully understood when considered in conjunction with the following detailed description and drawings.

[0027] The embodiments illustrated in the drawings are illustrative and representative in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of exemplary embodiments can be understood when read in conjunction with the following drawings, in which like structure is designated with like numerals. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of a waste extraction system according to one or more embodiments shown and described herein; [Figure 2] 2 is a schematic diagram of an exemplary particle filtration unit of the waste extraction system of FIG. 1 according to one or more embodiments shown and described herein. [Figure 3] 2 is a schematic diagram of another exemplary particle filtration unit of the waste extraction system of FIG. 1 according to one or more embodiments shown and described herein. [Figure 4] 2 is a schematic diagram of an ion exchange resin contained in an adsorption column of the waste extraction system of FIG. 1 according to one or more embodiments shown and described herein. DETAILED DESCRIPTION OF THE INVENTION

[0029] Referring generally to the drawings, embodiments of the present disclosure are directed to a waste extraction system and method for the removal of target waste radionuclides from a waste stream formed during a medical isotope production process. The waste stream contains multiple radionuclides, such as uranium (U-238), cesium-137 (Cs-137), and strontium-90 (Sr-90). The waste extraction system includes a precipitation tank, an adsorption column, and a column effluent tank fluidly coupled along a main waste pathway. The waste stream flows through the waste extraction system configured to remove the target radionuclides from the waste stream. The precipitation tank facilitates a pH adjustment step, and the adsorption column contains an ion exchange resin. The pH adjustment step uses an alkaline solution, such as sodium bicarbonate solution, to increase the pH of the waste stream from a pH of about 1 to a pH of about 8. Raising the pH of the waste stream precipitates the first target radionuclide, such as Sr-90, and other fission products from the waste stream, which are then filtered and removed. The resulting alkaline uranium-containing waste liquid is directed from the settling tank to an adsorption column, where an ion exchange resin absorbs a second target radionuclide, such as Cs-137. For example, under alkaline conditions, the ion exchange resin may exhibit a higher affinity for Cs-137 than for uranium.

[0030] The combination of precipitation and adsorption provided by the waste extraction system provides an efficient and effective system for removing certain radionuclides from nuclear waste streams. Indeed, the waste extraction system does not introduce organic reagents or materials, avoiding the generation of organic waste and simplifying waste disposal. Furthermore, the waste extraction system does not precipitate or concentrate uranium in solution; instead, the uranium remains diluted in the waste stream, reducing criticality concerns. Embodiments of the waste extraction system and a method of radionuclide waste extraction using the waste extraction system are now described. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0031] 1 , an exemplary embodiment of a waste extraction system 100 is shown. The waste extraction system 100 includes a settling tank 120, a particle filtration unit 140, an adsorption column 130, a column effluent tank 150, and a waste tank 155, each of which is fluidly coupled to a main waste pathway 160. The main waste pathway 160 includes one or more pipes, tubing, or other fluid transport mechanisms for facilitating the flow of a waste stream from a manufacturing facility through the settling tank 120, the particle filtration unit 140, and the adsorption column 130, to the column effluent tank 150, and ultimately to the waste tank 155. One or more pumps 180 are coupled to the main waste pathway 160 and serve to generate the flow of fluid within the main waste pathway 160. In one example operation, an upstream portion 162 of the main waste pathway 160 fluidly couples the waste extraction system 100 to a manufacturing area of a medical isotope production facility, and the waste stream includes radionuclide waste produced by the medical isotope production process.

[0032] The settling tank 120, particle filtration unit 140, and adsorption column 130 are positioned between and fluidly coupled to the upstream portion 162 of the main waste pathway 160 and the column effluent tank 150. The settling tank 120 is upstream of the adsorption column 130 such that a waste stream containing radionuclide waste enters the waste extraction system 100 along the upstream portion 162 of the main waste pathway 160 (e.g., the initial waste stream), traverses the settling tank 120 fluidly coupled to the upstream portion 162, traverses the particle filtration unit 140, and then traverses the adsorption column 130 along the main waste pathway 160. The settling tank 120 is fluidly coupled to a solution source 175 for introducing an alkaline solution into the precipitation tank 120 to increase the pH of the waste stream and precipitate a first target radionuclide, such as Sr-90, from the waste stream. The adsorption column 130 contains an ion exchange resin 112 configured to preferentially adsorb a second target radionuclide, such as Cs-137, from the elevated pH waste stream (FIG. 4). A column effluent tank 150 is fluidly coupled to the adsorption column 130 and, during operation, receives the waste stream currently being treated, which contains reduced levels of the first and second target radionuclides and may contain reduced levels of additional radionuclides.

[0033] 1 , settling tank 120 includes a waste stream input 123, a solution input 124, and a gas outlet 127, each located at a first end 121 of settling tank 120, and a waste stream output 125 located at a second end 122 of settling tank 120. Waste stream input 123 is fluidly coupled to an upstream portion 162 of a main waste pathway 160, and waste stream output 125 is fluidly coupled to an inter-column portion 165 of main waste pathway 160 that extends from settling tank 120 to a particle filtration unit 140 (which is itself fluidly coupled to adsorption column 130 by another inter-column portion 165). Solution input 124 is fluidly coupled to a solution pathway 172 that extends from a solution source 175 to solution input 124. Gas outlet 127 is fluidly coupled to off-gas pathway 128, which provides a pathway for off-gas formed in settling tank 120 to exit settling tank 120 and flow to an off-gas management system. As an example, during operation, sodium bicarbonate solution may contact sulfuric acid in settling tank 120, producing carbon dioxide gas, which is vented through gas outlet 127.

[0034] In operation, an alkaline solution, such as a NaHCO3 solution, a Na2CO3 solution, or a NaHCO3 / Na2CO3 solution, can be introduced into the precipitation tank 120 through the solution input 124. The alkaline solution raises the pH of the waste stream in the precipitation tank 120, causing precipitation of a first target radionuclide, such as Sr-90, thereby forming a radionuclide precipitate. Forming the radionuclide precipitate removes a quantity of the first target radionuclide from the waste stream. For example, the alkaline solution causes precipitation of 85% or more of the first target radionuclides initially present in the waste stream (e.g., present in the waste stream in the upstream portion 162 of the main waste pathway 160), such as 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 98.5% or more, 99% or more, 99.5% or more, 99.9% or more, or a value within a range having any two of these values as endpoints.

[0035] 1-3, radionuclide precipitates can be collected by particle filtration units 140. Exemplary particle filtration units 140a and 140b are shown in FIGS. 2 and 3, respectively. Particle filtration units 140, 140a, 140b include multiple filters 141, such as multiple in-line filters 141a (FIG. 2) or multiple concentric filters 141b (FIG. 3), fluidly coupled to waste stream output 125 of settling tank 120 by inter-column section 165 of main waste path 160. Each particle filtration unit 140a, 140b includes filter cavities 145a, 145b, fluid inputs 168a, 168b fluidly coupled to settling tank 120, and fluid outputs 169a, 169b fluidly coupled to adsorption column 130. Multiple filters 141a, 141b are housed within filter cavities 145a, 145b. The plurality of filters 141 includes an initial filter 142 and a final filter 144. The initial filter 142 is upstream of the final filter 144 relative to the waste stream output 125 of the settling tank 120. The initial filter 142 has a larger mesh size than the final filter 144. In some embodiments, the plurality of filters 141 includes one or more intermediate filters 146 positioned between the initial filter 142 and the final filter 144. Each of the one or more intermediate filters 146 has a mesh size that is equal to or smaller than the mesh size of the initial filter 142 and equal to or larger than the mesh size of the final filter 144. Indeed, in some embodiments, the plurality of filters 141 includes mesh sizes that gradually decrease from the initial filter 142 to the final filter 144. This facilitates separate collection of various sizes of radionuclide precipitate particles in each in-line filter, increasing collection efficiency.

[0036] In operation, a waste stream enters particle filtration units 140a, 140b through fluid inputs 168a, 168b, traverses multiple filters 141a, 141b, and exits through fluid outputs 169a, 169b. Particle filtration units 140a, 140b may include shielding shells 149a, 149b comprising lead or other radioactive shielding material and inner liners 148a, 148b separating filter cavities 145a, 145b from shielding shells 149a, 149b. In some embodiments, particle filtration units 140a, 140b are removably coupled to main waste path 160 (e.g., removably coupled to inter-column section 165 of main waste path 160). Thus, the particle filtration units 140, 140a, 140b may be removed from the main waste pathway 160 for disposal of the collected radionuclide precipitate and reinstallation of the particle filtration units 140, 140a, 140b, or alternatively for removal and replacement (e.g., replacement with new particle filtration units 140, 140a, 140b).

[0037] Referring now to FIG. 2 , particle filtration unit 140a is a linear particle filtration unit, and filters (i.e., multiple in-line filters 141a) are disposed along the Z-axis between fluid input 168a and fluid output 169a. Multiple in-line filters 141a include initial in-line filter 142a and final in-line filter 144a. Initial in-line filter 142a is upstream of final in-line filter 144a relative to fluid input 168a. Initial in-line filter 142a has a larger mesh size than final in-line filter 144a. In some embodiments, multiple in-line filters 141a include one or more intermediate in-line filters 146a positioned between initial in-line filter 142a and final in-line filter 144a. Each of one or more intermediate in-line filters 146a has a mesh size equal to or smaller than the mesh size of initial in-line filter 142a and equal to or larger than the mesh size of final in-line filter 144a. Indeed, in some embodiments, the multiple in-line filters 141 a include mesh sizes that progressively finer from the initial in-line filter 142 a to the final in-line filter 144 a, which facilitates separate collection of different sized radionuclide precipitate particles in each in-line filter, increasing collection efficiency.

[0038] 3, particle filtration unit 140b is a concentric particle filtration unit having filters (i.e., multiple concentric filters 141b) arranged concentrically, with a radially outer filter surrounding a radially inner filter, and each of the multiple concentric filters 141b being radially outward of fluid input 168b. Multiple concentric filters 141b include initial stage concentric filter 142b and final stage concentric filter 144b. Initial stage concentric filter 142b is upstream of final stage concentric filter 144b relative to fluid input 168b of particle filtration unit 140b. Additionally, both initial and final stage concentric filters 142b, 144b are radially outward (e.g., along the r-axis) from fluid input 168b such that a fluid (e.g., a waste stream) entering particle filtration unit 140b through fluid input 168b passes through initial filter 142b before passing through final filter 144b and ultimately exiting through fluid output 169b. Initial filter 142b has a larger mesh size than final filter 144b. In some embodiments, multiple concentric filters 141b include one or more intermediate filters 146b positioned radially between initial filter 142b and final filter 144b. Each of the one or more intermediate filters 146b has a mesh size equal to or smaller than the mesh size of initial filter 142b and equal to or larger than the mesh size of final filter 144b. Indeed, in some embodiments, the plurality of concentric filters 141b comprise progressively finer mesh sizes from the initial concentric filter 142b to the final concentric filter 144b. This facilitates separate collection of various sized radionuclide precipitate particles in each concentric filter, increasing collection efficiency. While particle filtration units 140a, 140b are two exemplary particle filtration units 140 that may be used in the waste extraction system 100, it should be understood that any particle filtration unit sized and configured to remove radionuclide precipitates in the waste extraction system 100 may be used.

[0039] 1 , in some embodiments, the first end 121 of the settling tank 120 faces the second end 122 of the settling tank 120, and the first end 121 of the settling tank 120 is above the second end 122 of the settling tank 120. This orientation promotes gravity-assisted flow of the waste stream through the settling tank 120. Gravity-assisted flow may reduce the pump pressure and pump power required to flow the waste stream through the settling tank 120. Furthermore, by positioning the second end 122 below the first end 121, the waste stream output 125 may be positioned below the first end 121 and at the lowest point of the settling tank 120, causing gravity-assisted settling of the radionuclide precipitate at the second end 122 of the settling tank 120 and promoting the flow of the radionuclide precipitate through the waste stream output 125 so that it can be collected as the waste stream traverses the particle filtration unit 140.

[0040] The adsorption column 130 includes a waste stream input 134 and a waste stream output 135. The waste stream input 134 is located at a first end 131 of the adsorption column 130, and the waste stream output 135 is located at a second end 133 of the adsorption column 130. The waste stream input 134 is fluidly coupled to an inter-column section 165 of a main waste path 160 extending from the settling tank 120. The waste stream output 135 is fluidly coupled to the inter-column section 165 of the main waste path 160 extending toward the column waste tank 150, and to one or more intervening components of the waste extraction system 100 that provide additional processing of the waste stream, which may be positioned, for example, directly to the column waste tank 150 (as shown in FIG. 1 ) or between the adsorption column 130 and the column waste tank 150. Additionally, in some embodiments, first end 131 of adsorption column 130 faces second end 133, and first end 131 of adsorption column 130 is above second end 133. This orientation promotes gravity-assisted flow of the waste stream through adsorption column 130. Gravity-assisted flow may reduce the pump pressure and pump power required to flow the waste stream through adsorption column 130. Gravity-assisted flow may also maximize contact between ion exchange resin 112 (FIG. 4) and the waste stream, maximizing adsorption of the second target radionuclide.

[0041] Column waste tank 150 is fluidly coupled to main waste pathway 160, for example, one of inter-column portions 165 of main waste pathway 160. After passing through settling tank 120, particle filtration unit 140, and adsorption column 130, the treated waste stream flows into column waste tank 150. Waste tank 155 is fluidly coupled to column waste tank 150 by waste tank portion 164 of main waste pathway 160. The resulting waste in column waste tank 150 can be directed along waste tank portion 166 to waste tank 155 for final treatment and off-site removal. This final treatment may include solidifying the resulting waste with concrete, which may occur in waste tank 155, to form a solidified final waste. In some embodiments, column effluent tank 150 and waste tank 155 are the same volume, e.g., 30 gallons, 35 gallons, 40 gallons, 45 gallons, 50 gallons, 55 gallons, 60 gallons, 65 gallons, 70 gallons, or the like, in the range of 25 gallons to 75 gallons. In other embodiments, column effluent tank 150 and waste tank 155 may be different volumes, in the range of 25 gallons to 75 gallons. During operation, treated waste in column effluent tank 150 may be directed along waste tank portion 164 to waste tank 155 for final treatment and removal off-site. For example, the treated waste stream may ultimately be disposed of as a solid waste form. Waste tank 155 may be pre-filled with a solidifying agent, such as concrete, to facilitate solidification of treated waste received from the column effluent tank. The waste tank 155 may also include a mixing system, which may include a motor and mixing mechanism to combine the treated waste and solidification agent to form a solidified concrete waste that is easier to dispose of than liquid waste.

[0042] The treated waste, after passing through the settling tank 120 and the adsorption column 130, contains reduced amounts of the first and second target radionuclides and may have reduced amounts of other radionuclides. By removing radionuclides such as the first and second target radionuclides using the waste extraction system 100, the resulting waste contains lower levels of radioactivity than the initial waste stream. In fact, the target radionuclides contribute a disproportionate amount of the total radioactivity in the initial waste stream. For example, Cs-137 is a gamma-emitting nuclide, and therefore, it is desirable to minimize the amount of Cs-137 in the resulting waste. Adsorption of target radionuclides such as Cs-137 and Sr-90 allows these target radionuclides to be disposed of separately from the resulting waste, for example, in a minimized volume sealed in concrete.

[0043] Referring now to FIG. 4, a schematic cross-sectional view of an adsorption column 130 is shown. The ion exchange resin 112 is housed within the adsorption column 130 and may comprise a cation exchange resin. One example of the ion exchange resin 112 is an inorganic cation exchange resin, such as a crystalline silicotitanate resin. Other examples of ion exchange resins include spherical resorcinol formaldehyde (sRF) resin. Without intending to be limited by theory, the crystalline silicotitanate resin is configured such that steric hindrance of metal ions (e.g., radionuclide ions present in the waste stream) affects the adsorption process. For example, the geometry of the crystalline silicotitanate resin preferentially adsorbs cesium ions, such as Cs-137, upon contact between the crystalline silicotitanate resin and cesium ions with relatively large radii and hydration diameters. Furthermore, crystalline silicotitanate resins have a preference for adsorption of Cs-137 under alkaline conditions, and therefore, crystalline silicotitanate resins as ion exchange resins 112 are effective in adsorption column 130. Without intending to be limited by theory, it is believed that the adsorption of Cs-137 onto crystalline silicotitanate resins proceeds by a two-step mechanism, specifically, the adsorption of Cs +The hydrated and crystalline silicotitanate resin network stiffness variations work in concert to accommodate Cs-137 ions. In some embodiments, the ion exchange resin 112 has a Cs-137 content in the range of 100 mg Cs-137 per gram of cation exchange resin 116 (i.e., 100 mg / g) to 200 mg / g, such as 125 mg / g to 175 mg / g, for example, 105 mg / g, 110 mg / g, 115 mg / g, 120 mg / g, 125 mg / g, 130 mg / g, 135 mg / g, 140 mg / g, 145 mg / g, 150 mg / g, or 160 mg / g. g / g, 153 mg / g, 155 mg / g, 157 mg / g, 160 mg / g, 165 mg / g, 170 mg / g, 175 mg / g, 180 mg / g, 185 mg / g, 190 mg / g, 195 mg / g, 200 mg / g, or any range having any two of these values as endpoints, or any value within a range having any two of these values as endpoints.

[0044] By using a cation exchange resin with a particular affinity for Cs-137 adsorption, such as a crystalline silicotitanate resin, as the ion exchange resin 112, Cs-137 can be removed from a waste stream with an increased pH (i.e., after traversing the settling tank 120 and particle filtration unit 140) in the presence of large amounts of uranium. Indeed, the waste stream can contain uranium at a gram / liter level that is at least 500 times higher than the gram / liter levels of both strontium-90 and cesium-137, e.g., at least 750 times higher, at least 1000 times higher, at least 1250 times higher, at least 1500 times higher, at least 2000 times higher, or a multiplier within a range having any two of these values as endpoints. In some embodiments, the initial waste stream may include uranium at a gram / liter level that is at least 500 times higher than the gram / liter level of any individual of the following radionuclides: barium, cerium, lanthanum, molybdenum, neodymium, palladium, praseodymium, rubidium, rhodium, ruthenium, samarium, yttrium, and zirconium, e.g., at least 750 times higher, at least 1000 times higher, at least 1250 times higher, at least 1500 times higher, at least 2000 times higher, or a multiplier within a range having any two of these values as endpoints. Further, uranium may comprise 40% to 60% by weight of the total radionuclides in the initial waste stream. In some embodiments, the initial waste stream includes uranium at 1 gram / liter or higher, such as 1.5 grams / liter, 2 grams / liter or higher, 2.5 grams / liter or higher, 3 grams / liter or higher, and values within a range having any two of these values as endpoints. Other radionuclides present in the waste stream that can be adsorbed by the ion exchange resin 112 include barium, cerium, cesium, lanthanum, molybdenum, sodium, neodymium, palladium, praseodymium, rubidium, rhodium, ruthenium, samarium, strontium, yttrium, zirconium, protactinium, or combinations thereof.

[0045] 4, in some embodiments, the ion exchange resin 112 comprises a plurality of ion exchange resin beads 114, such as beads of crystalline silicotitanate resin. The ion exchange resin beads 114 have an average diameter ranging from 200 μm to 1000 μm, e.g., 400 μm to 800 μm, such as 400 μm, 425 μm, 450 μm, 475 μm, 500 μm, 525 μm, 550 μm, 575 μm, 600 μm, 625 μm, 650 μm, 675 μm, 700 μm, 725 μm, 750 μm, 775 μm, 800 μm, or any range having any two of these values as endpoints. In some embodiments, the plurality of ion exchange resin beads 114 are dry-pumped into the adsorption column 130. Upon entering the adsorption column 130, the ion exchange resin beads 114 may be pre-treated with an alkaline solution, such as aqueous sodium carbonate, and added to the adsorption column 130 as a resin slurry (e.g., resin in alkaline solution). The pre-treatment solution is of a similar pH (e.g., within 1 pH unit) to the initial waste stream. For example, the pre-treatment solution may include sodium carbonate with a pH of 8. Pre-treating the ion exchange resin beads 114 improves separation (i.e., adsorption) effectiveness and efficiency, especially when the waste stream is initially introduced into the adsorption column 130. Furthermore, pre-treating the ion exchange resin beads 114 may occur at a location remote from the waste stream, such as a different location within the waste extraction system 100 or a different location within a medical isotope production facility. Thus, personnel performing this pre-treatment may be located remote from the waste stream containing radionuclides.

[0046] 1-4, a method of radionuclide waste extraction using waste extraction system 100 will now be described. The method includes directing a waste stream from an upstream portion 162 of a main waste pathway 160 to a settling tank 120 and directing an alkaline solution, such as a sodium bicarbonate solution, to the settling tank 120. Directing the alkaline solution to the settling tank 120 increases the pH of the waste stream. The waste stream in the upstream portion 162 of the main waste pathway 160 has a pH between 0 and 3, e.g., 0.2, 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.4, 1.5, 1.6, 1.8, 2, 2.2, 2.4, 2.5, 2.6, 2.8, 3, or a range including any two of these values as endpoints. Directing the alkaline solution to the precipitation tank 120 may increase the pH of the waste stream so that the waste stream entering the adsorption column 130 has a pH of 7 to 10, e.g., 7.2, 7.4, 7.5, 7.6, 7.8, 8, 8.2, 8.4, 8.5, 8.6, 8.8, 9, 9.2, 9.4, 9.5, 9.6, 9.8, 10, or a range including any two of these values as endpoints.

[0047] An alkaline solution may be directed from a solution source 175 along a solution path 172 through a solution input 124 to the precipitation tank 120. One or more of pumps 180 may be fluidly coupled to the solution path 172 to help facilitate the flow of the alkaline solution through the solution path 172 and into the precipitation tank 120. Increasing the pH of the waste stream causes precipitation of a first target radionuclide, such as Sr-90, from the waste stream to form a radionuclide precipitate. In some embodiments, the first target radionuclide includes Sr-90. However, it should be understood that additional radionuclides may be precipitated in the precipitation tank 120, such as Ba, La, Ce, Nd, Pr, Rb, Sm, Y, and Zr, any one of which may be considered a “first target radionuclide” in the terminology used herein. Furthermore, it should be understood that the precipitation process is not limited to precipitating one single radionuclide, but instead, any combination of these radionuclides may be precipitated during the same processing step.

[0048] The method then includes directing the waste stream and radionuclide precipitate from the settling tank 120 to a particle filtration unit 140, e.g., along inter-column section 165. The waste stream traverses the particle filtration unit 140, which removes the radionuclide precipitate from the waste stream. The waste stream then flows from the particle filtration unit 140 to an adsorption column 130, e.g., along another inter-column section 165. In operation, the waste stream flows into the adsorption column 130 through the waste stream input 134, and the ion exchange resin 112 contained within the adsorption column 130 adsorbs a second target radionuclide, such as Cs-137, present in the waste stream. Increasing the pH of the waste stream in the settling tank 120 increases the adsorption effectiveness of the ion exchange resin 112, particularly when the ion exchange resin comprises a crystalline silicotitanate resin. During operation, the ion exchange resin 112 contained in the adsorption column 130 adsorbs 85% or more of the second target radionuclides initially present in the waste stream (e.g., present in the waste stream in the upstream portion 162 of the main waste pathway 160), e.g., strontium-90 and cesium-137 present in the waste stream, such as 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 98.5% or more, 99% or more, 99.5% or more, 99.9% or more, or a range having any two of these numbers as endpoints.

[0049] The method then includes directing the waste stream from the adsorption column 130 to the column waste tank 150, for example, along the inter-column section 165 of the main waste pathway 160. In some embodiments, the method further includes directing the resulting waste along the waste tank section to the waste tank 155 for final treatment and off-site removal. As described above, the final treatment of the resulting waste can be solidified with concrete to form a solidified final waste. This densifies the resulting waste. The final waste contains a lower level of curies per cubic meter than the waste used to form the final waste. Furthermore, the method of radionuclide waste extraction using the waste extraction system 100 described herein is effective in removing a majority of the targeted radionuclides, such that the final waste formed from the resulting waste retains low levels of radioactivity. For example, the resulting waste may contain Sr-90 of less than 0.25 curies per cubic meter, e.g., less than 0.2 curies per cubic meter, less than 0.15 curies per cubic meter, less than 0.1 curies per cubic meter, less than 0.08 curies per cubic meter, less than 0.06 curies per cubic meter, less than 0.05 curies per cubic meter, less than 0.04 curies per cubic meter, less than 0.03 curies per cubic meter, less than 0.02 curies per cubic meter, less than 0.01 curies per cubic meter, or any value in a range having any two of these values as endpoints. The resulting waste may also contain Cs-137 at less than 10 curies per cubic meter, e.g., less than 8 curies per cubic meter, less than 6 curies per cubic meter, less than 5 curies per cubic meter, less than 4 curies per cubic meter, less than 2 curies per cubic meter, less than 1 curie per cubic meter, less than 0.75 curies per cubic meter, less than 0.5 curies per cubic meter, less than 0.25 curies per cubic meter, less than 0.1 curies per cubic meter, or any value within a range having any two of these values as endpoints.In some embodiments, the resulting waste contains less than 0.04 Curies per cubic meter of Sr-90 and less than 1 Curie per cubic meter of Cs-137. In some embodiments, the final densified waste contains less than 0.04 Curies per cubic meter of Sr-90 and less than 1 Curie per cubic meter of Cs-137.

[0050] Furthermore, the above values of curies per cubic meter in the resulting waste may be greater than or equal to 1000 curies per cubic meter, e.g., greater than 200 curies per cubic meter, greater than 300 curies per cubic meter, greater than 300 curies per cubic meter, greater than 500 curies per cubic meter, greater than 1000 curies per cubic meter, greater than 2500 curies per cubic meter, greater than 5000 curies per cubic meter, or within a range having any two of these values as endpoints. In embodiments including any value of Sr-90 and including Cs-137 of greater than 44 curies per cubic meter, e.g., greater than 50 curies per cubic meter, greater than 100 curies per cubic meter, greater than 250 curies per cubic meter, greater than 500 curies per cubic meter, greater than 800 curies per cubic meter, greater than 1000 curies per cubic meter, greater than 1500 curies per cubic meter, greater than 2000 curies per cubic meter, greater than 3500 curies per cubic meter, or any value in a range having any two of these values as endpoints, can be achieved using the waste extraction system 100 described herein.

[0051] In the embodiments described herein, Cs-137 and Sr-90 are referred to as target radionuclides, although other target radionuclides may be present in the waste stream and precipitated by the increased pH in the precipitation tank 120 and / or adsorbed by the ion exchange resin 112 contained in the adsorption column 130. For example, other target radionuclides that may be present in the waste stream and precipitated in the precipitation tank 120 and / or adsorbed by the ion exchange resin 112 include barium, cerium, cesium, lanthanum, molybdenum, sodium, neodymium, palladium, praseodymium, rubidium, rhodium, ruthenium, samarium, strontium, yttrium, zirconium, protactinium, or combinations thereof.

[0052] As used herein, the words "approximately," "about," "substantially," and similar words are intended to have broad meanings consistent with common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. These words should be understood by those of ordinary skill in the art who review this disclosure to allow for the description of certain features described in the detailed description and claimed below without limiting the scope of those features to given precise numerical values or idealized geometric configurations. Accordingly, these words should be interpreted as indicating that insubstantial or minor variations or modifications of the subject matter described in the detailed description and claimed below are considered to be within the scope of the disclosure as set forth in the subsequent claims.

[0053] As used herein, the term "coupled" and variations thereof mean that two members are joined to one another, either directly or indirectly. The joining can be static (e.g., permanent or fixed) or movable (e.g., removable or releasable). The joining can be achieved by two members being directly joined to one another, by two members being joined to one another using a separate intervening member and an additional intermediate member joined to one another, or by two members being joined to one another using an intervening member integrally formed with one of the two members as a single, unitary body. When "coupled" or variations thereof are modified by an additional term (e.g., directly coupled), the general definition of "coupled" given above is modified by the plain linguistic meaning of the additional term (e.g., "directly coupled" means joining of two members without any separate intervening member), resulting in a narrower definition than the general definition of "coupled" given above. The joining can be mechanical, electrical, optical, or fluid.

[0054] References to the location of elements herein (e.g., "top," "bottom," "upper," "lower") are used merely to describe the orientation of various elements in the drawings. It should be noted that the orientation of various elements may vary in other exemplary embodiments, and such variations are intended to be encompassed by the present disclosure.

[0055] Although the figures and detailed description may indicate a particular order of method steps, the order of the steps may differ from that shown and described unless specified otherwise. Also, two or more steps may be performed simultaneously or concurrently in parallel unless specified otherwise. Such variations may depend, for example, on the software and hardware selected and on the choice of the designer. All such variations are within the scope of this disclosure. Similarly, software implementations of the described methods may be realized using standard programming techniques with rule-based logic and other logic implementing the various connection, processing, comparison, and decision steps.

[0056] While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications can be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. Accordingly, the following claims are intended to cover all such changes and modifications that are within the scope of the claimed subject matter.

Claims

1. 1. A waste extraction system comprising: a settling tank having a waste stream input, a solution input, and a waste stream output, the waste stream input being fluidly coupled to an upstream portion of a main waste pathway; a column waste tank; an adsorption column positioned between the settling tank and the column effluent tank, fluidly coupled to the settling tank and the column effluent tank along the main waste path, the adsorption column containing an ion exchange resin and positioned downstream of the settling tank; a solution path extending from a solution source to the solution input of the settling tank, the solution source containing an alkaline solution; a particle filtration unit positioned between the settling tank and the adsorption column and fluidly coupled to the settling tank and the adsorption column; A waste extraction system comprising:

2. The alkaline solution is NaHCO ３ Solution, Na ２ CO ３ solution or NaHCO ３ / Na ２ CO ３ The waste extraction system of claim 1 comprising a solution.

3. 2. The waste extraction system of claim 1, wherein the waste stream input and the solution input of the settling tank are each located at a first end of the settling tank, and the waste stream output is located at a second end of the settling tank opposite the first end.

4. 4. The waste extraction system of claim 3, wherein the first end of the settling tank is above the second end of the settling tank.

5. the adsorption column comprising a waste stream input located at a first end of the adsorption column and a waste stream output located at a second end of the adsorption column; the first end of the adsorption column faces the second end of the adsorption column; the first end of the adsorption column is above the second end of the adsorption column; 10. The waste extraction system of claim 1.

6. 10. The waste extraction system of claim 1, wherein the ion exchange resin comprises ion exchange resin beads with an average diameter in the range of 400 μm to 800 μm.

7. 10. The waste extraction system of claim 1, wherein the ion exchange resin comprises a crystalline silicotitanate resin.

8. the particle filtration unit comprises a plurality of filters; the plurality of filters include a first-stage filter and a last-stage filter, the initial filter is upstream of the final filter relative to the waste stream output of the settling tank; The initial stage filter has a larger mesh size than the final stage filter.

10. The waste extraction system of claim 1.

9. 9. The waste extraction system of claim 8, wherein the plurality of filters comprises one or more intermediate filters positioned between the initial filter and the final filter, each of the one or more intermediate filters having a mesh size that is less than or equal to the mesh size of the initial filter and greater than or equal to the mesh size of the final filter.

10. 1. A method for radionuclide waste extraction comprising: directing a waste stream from an upstream portion of a main waste path to a settling tank; directing an alkaline solution into the precipitation tank, thereby increasing the pH of the waste stream and causing precipitation of a first target radionuclide from the waste stream to form a radionuclide precipitate; directing the waste stream from the settling tank to an adsorption column; adsorbing the second target radionuclide from the precipitation tank onto an ion exchange resin contained in the adsorption column; A method for providing

11. 11. The method of claim 10, further comprising harvesting the radionuclide precipitate using a particle filtration unit positioned between and fluidly coupled to the settling tank and the adsorption column.

12. 11. The method of claim 10, wherein the first target radionuclide comprises strontium-90 and the second target radionuclide comprises cesium-137.

13. 11. The method of claim 10, wherein the waste stream in the upstream portion of the main waste pathway comprises a pH of 0 to 3, and the waste stream entering the adsorption column comprises a pH of 7 to 10.

14. The alkaline solution is NaHCO ３ Solution, Na ２ CO ３ solution or NaHCO ３ / Na ２ CO ３ The method of claim 10 comprising a solution.

15. 11. The method of claim 10, further comprising directing the waste stream from the adsorption column to a column effluent tank, wherein the waste stream flowing into the column effluent tank comprises treated waste containing less than or equal to 0.04 curies per cubic meter of strontium-90 and less than or equal to 1 curie per cubic meter of cesium-137.

16. 16. The method of claim 15, further comprising directing the treated waste from the column waste tank to a waste tank, and then solidifying the treated waste.

17. 11. The method of claim 10, wherein the waste stream in the upstream portion of the main waste pathway comprises a gram / liter level of uranium that is at least 500 times higher than the gram / liter levels of both strontium-90 and cesium-137.

18. the first target radionuclide comprises barium, cerium, cesium, lanthanum, molybdenum, sodium, neodymium, palladium, praseodymium, rubidium, rhodium, ruthenium, samarium, strontium, yttrium, zirconium, or protactinium, or a combination thereof; 11. The method of claim 10, wherein the second target radionuclide comprises barium, cerium, cesium, lanthanum, molybdenum, sodium, neodymium, palladium, praseodymium, rubidium, rhodium, ruthenium, samarium, strontium, yttrium, zirconium, or protactinium, or a combination thereof.

19. 11. The method of claim 10, wherein the waste stream in the upstream portion of the main waste pathway comprises 1 gram / liter or more of uranium.

20. The method of claim 10, wherein the ion exchange resin comprises ion exchange resin beads having an average diameter in the range of 400 μm to 800 μm.

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