Patent Application
20180350478
Embodiments of the present invention relate generally to methods and systems for treating liquid wastes having high levels of radionuclides. More specifically, embodiments of the present invention relate to methods and systems for treating liquid wastes having high levels of cesium.
As is well known, nuclear fuel produced in government facilities is processed to remove special nuclear material (SNM) such as plutonium, enriched uranium and other radionuclides of interest. SNM is recovered by dissolving the fuel in acid followed by elemental and isotopic separation of the SNM into separate streams for re-use in nuclear fuel and thermo-nuclear devices. The spent processing wastes remaining after SNM recovery contains fission products, such as strontium-90 and cesium-137, and other radionuclides, primarily lanthanides and actinides, in concentrations sufficient to generate measurable amounts of heat and be labeled as high-level nuclear waste by the US Nuclear Regulatory Commission (US-NRC). The primary non-radioactive constituents of high-level waste are sodium, potassium, aluminum, nitrates, nitrites and sulfates. Most of the high-level waste in the United States was generated by the Department of Energy (DOE) at the Hanford, Savannah River and Idaho National Laboratory sites. The high-level waste typically exists inside large storage tanks in three physico-chemical phases known as supernate, salt cake and sludge. The Hanford Site has over 53 million gallons of high-level and chemical waste that is now being stored in approximately 170 underground tanks. The Savannah River Site has over 36 million gallons of high level-waste stored in approximately 50 underground tanks. Over the years the DOE has further concentrated wastes stored in the tanks by evaporation to make room for adding more liquids and they have added significant amounts of sodium hydroxide and sodium nitrite to the tanks to maintain high pH and chemically reducing conditions that inhibit tank corrosion. These practices have led to highly concentrated chemical solutions and the precipitation of sodium nitrate/nitrite salts. When the high-level waste tanks are emptied the salt cake will have to be re-dissolved by purified water thus leading to the creation of millions of gallons of additional liquid waste requiring future treatment.
Currently, both the Savannah River Site (SRS) and Hanford Site (Hanford) have experienced delays associated with the design, installation and commissioning of equipment needed to separate strontium-90 (Sr-90) and cesium-137 (Cs-137) from the high-level waste supernate and related liquids. The inability to effectively remove Sr-90 and Cs-137 could cause the sites to miss regulatory milestones and extend the time required for the site cleanup missions thus resulting in hundreds of millions of dollars of cost overruns.
Therefore there at least remains a need in the art for methods and systems for treating liquid wastes having high levels of radionuclides such as cesium and strontium.
Example embodiments of the present invention recognize and address considerations of prior art constructions and methods.
According to one aspect, an example embodiment of the present invention provides a method for treating a liquid waste having at least one radionuclide in a salt solution. The method includes supplying the liquid waste to a plurality of cross flow filters from at least one high level waste tank; filtering the liquid waste via the plurality of cross flow filters to form a clarified salt solution; removing at least one radionuclide from the clarified salt solution via a plurality of elutable ion exchange columns filled with an ion exchange media to form an eluate and a decontaminated salt solution; and removing at least one radionuclide from the eluate via a first non-elutable adsorption component to form a dewatered radionuclide sorbent and a decontaminated eluate solution.
According to another aspect, an example embodiment of the present invention provides a regenerable system for treating a liquid waste having at least one radionuclide in a salt solution. The system includes a plurality of cross flow filters having an inlet and an outlet, a plurality of elutable ion exchange columns in fluid communication with the outlet and comprising an eluate outlet and a decontaminated salt solution outlet, and a first non-elutable adsorption component in fluid communication with the eluate outlet and comprising a decontaminated eluate solution outlet. The plurality of elutable ion exchange columns comprises an ion exchange media.
Those skilled in the art will appreciate the scope of the present invention and realize additional aspects thereof after reading the following detailed description of example embodiments in association with the accompanying drawing figures.
A full and enabling disclosure of the present invention, including the best mode thereof directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which:
Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.
Reference will now be made in detail to certain preferred embodiments of the present invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations.
Exemplary embodiments provide a regenerable system and method that can be designed, manufactured, installed, and commissioned in a short timeframe to address waste treatment and disposal issues, which, for example, would aid the DOE in meeting regulatory commitments and budgetary constraints. Of particular value is the ability to send cesium loaded non-elutable adsorption media directly to disposal, thus eliminating the need, for example, for producing “salt-only” waste canisters at SRS and for operating the High Level Waste (HLW) vitrification facility for supernate treatment at Hanford.
In one aspect, a regenerable system for treating a liquid waste having at least one radionuclide in a salt solution is provided. In general, the system may include a plurality of cross flow filters (e.g., four) having an inlet and an outlet, a plurality of elutable ion exchange columns in fluid communication with the outlet and comprising an eluate outlet and a decontaminated salt solution outlet, and a first non-elutable adsorption component in fluid communication with the eluate outlet and comprising a decontaminated eluate solution outlet. In some embodiments, the plurality of elutable ion exchange columns may comprise an ion exchange media.
In accordance with an exemplary embodiment, the liquid waste may comprise at least one radionuclide. In some embodiments, for instance, the liquid waste may comprise at least one of cesium, strontium, actinide, or any combination thereof. In further embodiments, for example, the liquid waste may comprise cesium.
Following filtration by the plurality of cross flow filters 107, for instance, the clarified salt solution 108 may move through a plurality of elutable ion exchange columns 114 (e.g., Generation 3 Shielded Ion Exchange Module (SIXM3)). In some embodiments, for example, the plurality of elutable ion exchange columns may comprise a gamma dose rate reduction by a factor greater than 106. In further embodiments, for instance, the plurality of elutable ion exchange columns may comprise a maximum decay heat loading of about 3,000 W (e.g., 2,896 W). Although multiple elutable ion exchange columns 114 are referenced herein, the system may comprise only one elutable ion exchange column 114.
The plurality of elutable ion exchange columns 114 may include at least one ion exchange media. According to certain exemplary embodiments, for instance, the ion exchange media may comprise spherical resorcinol formaldehyde (sRF). In such embodiments, for example, the sRF may be used for over thirty loading/elution/regeneration cycles. In further embodiments, for instance, the sRF may comprise a loading cycle of about 155 bed volumes. In addition, by using sRF as the ion exchange media, for instance, the plurality of elutable ion exchange columns 114 may achieve high cesium decontamination factors (e.g., 5,0002) in liquid waste. Moreover, in certain embodiments, for example, eluted cesium may be adsorbed onto another sorbent ore returned to a tank as secondary liquid waste.
Moreover, in accordance with certain embodiments and as shown in
According to certain embodiments, for example, the decontaminated salt solution 129 may then be transferred to a waste processor 130. In some embodiments, for instance, the waste processor 130 may be in fluid communication with the decontaminated salt solution outlet of the plurality of elutable ion exchange columns 114. In this regard, the waste processor 130 may package, stabilize, and/or treat the decontaminated salt solution 129. In certain embodiments, for example, the waste processor 130 may scrub the decontaminated salt solution 129. In some embodiments, for instance, the waste processor 130 may comprise a processing facility (e.g., Saltstone Processing Facility (SPF) at SRS), a direct feed low activity vitrifier (e.g., DFLAW at Hanford), a supplemental low activity vitrifier (e.g., supplemental LAW at Hanford) and/or the like. Moreover, in further embodiments, for example, the decontaminated salt solution 129 may be transferred to tanker trucks for off-site processing. As a result of processing by the waste processor 130, packaged solids 135 (e.g., cement-like grout, stabilized glassified waste canisters, filters, resins, solidified concentrations and/or the like) and a scrubber condensate 131 may be formed. In some embodiments, for instance, the packaged solids 135 may be disposed via any suitable means of solid waste disposal 136 understood by one of ordinary skill in the art. In further embodiments, for example, the scrubber condensate 131 may undergo condensate treatment. For instance, the scrubber condensate 131 may be treated by any suitable effluent treatment means 132 understood by one of ordinary skill in the art. Treatment by the effluent treatment means 132 may form purified water 137 and packaged solids 133 (e.g., cesium-loaded non-elutable adsorbent columns, cement-like grout, stabilized glassified waste canisters, filters, resins, solidified concentrations and/or the like). The purified water 137 may be disposed of by any suitable water disposal means 138 understood by one of ordinary skill in the art. Moreover, the packaged solids 133 may be disposed via any suitable means of solid waste disposal 134 understood by one of ordinary skill in the art.
In accordance with certain embodiments, for example, the eluate solutions 115 formed from the treatment of the clarified salt solution 108 with the plurality of elutable ion exchange columns 114 or from sRF elution/regeneration may be treated with an alkali 116 and run through a first non-elutable adsorption component 117 to form a decontaminated eluate solution 118, which may be stored in one or more eluate tanks 119. In this regard, the first non-elutable adsorption may remove cesium from all eluate and eluate related liquids (rinses, etc.) upstream of the eluate tanks 119. The first (and similarly the second) non-elutable adsorption components 117, 120 may be physically located inside at least one shielded transport cask wherein several operations involving liquid treatment and waste processing may take place prior to transporting the non-elutable adsorption components 117, 120. The non-elutable adsorption components 117, 120 may be designed with remote ancillary features that allow them to be loaded with cesium, dewatered, and sealed for shipment in a safe and ALARA manner. The non-elutable adsorption components 117, 120 may be operated in a manner that precludes the accumulation of cesium and related liquid waste radionuclides above legal cutoff limits, which makes the dewatered non-elutable adsorption components 117, 120 candidates for disposal as low-level waste (LLW). In particular, after treatment by non-elutable adsorption components 117, 120, the cesium concentration in the decontaminated eluate solutions 118, 121 may be very low, and the neutralized sodium nitrate in this stream may be at a concentration of about 0.25 M. In this regard, the decontaminated eluate solutions 118, 121 may have low concentrations of radionuclides and salts.
In some embodiments, for instance, the one or more eluate tanks 119 may be in fluid communication with the decontaminated eluate solution outlet of the first non-elutable adsorption component 117. Moreover, in further embodiments, for example, the one or more eluate tanks 119 may comprise an eluate tank outlet. According to certain exemplary embodiments, for instance, the first non-elutable adsorption component 117 may comprise a plurality of non-elutable adsorption columns (e.g., 3 Generation 2 Shielded Ion Exchange Modules (SIXM2)). The plurality of non-elutable adsorption columns may be arranged in series, on a carousel and/or the like. In some embodiments, for example, the first non-elutable adsorption component 117 may comprise at least one of chabazite zeolite, crystalline silicotitanate (CST), metal-hexacyanoferrate (FeCN), or any combination thereof. In further embodiments, for instance, the first non-elutable adsorption component 117 may comprise chabazite zeolite. The zeolite may provide effective removal of cesium from the eluate solution 115 comprising dilute sodium nitrate.
In accordance with an exemplary embodiment, the decontaminated eluate solution 118 may either flow through a second non-elutable adsorption component 120 to form a double decontaminated eluate solution 121, or, in other embodiments, may flow directly to the waste processor 130 to be processed if the decontaminated eluate solution 118 comprises a low cesium concentration. In some embodiments, for example, the second non-elutable adsorption component 120 may be in fluid communication with the eluate tank outlet. Moreover, in further embodiments, for instance, the second non-elutable adsorption component 120 may comprise a second non-elutable adsorption component outlet. According to certain exemplary embodiments, for instance, the second non-elutable adsorption component 120 may also comprise a plurality of non-elutable adsorption columns (e.g., 3 Generation 2 Shielded Ion Exchange Modules (SIXM2)). The plurality of non-elutable adsorption columns may be arranged in series, on a carousel and/or the like. In some embodiments, for example, the second non-elutable adsorption component 120 may comprise at least one of chabazite zeolite, crystalline silicotitanate (CST), metal-hexacyanoferrate (FeCN), or any combination thereof. In further embodiments, for instance, the second non-elutable adsorption component 120 may comprise chabazite zeolite.
If the decontaminated eluate solution 118 flows through the second non-elutable adsorption component 120 to form the double decontaminated eluate solution 121, for example, the double decontaminated eluate solution 121 may then flow through a concentrator 122 (e.g., sodium nitrate concentrator) to form purified water 123 and concentrator reject 126. In some embodiments, for example, the concentrator 122 may be in fluid communication with the second non-elutable adsorption component outlet. In certain embodiments, for example, the concentrator 122 may comprise any suitable means of reverse osmosis, evaporation and/or the like as understood by one of ordinary skill in the art. Moreover, in further embodiments, for instance, the concentrator 122 may comprise a purified water outlet and a concentrator reject outlet. In certain embodiments, for example, the concentrator reject outlet may be in fluid communication with the waste processor 130. The purified water may be stored in one or more purified water storage tanks 124, which may be in fluid communication with the purified water outlet, and, in this regard, provide reclaimed water for reuse 125. The concentrator reject 126, however, may then flow to the waste processor 130 to be processed as previously described herein.
In accordance with certain embodiments, for example, sodium hydroxide may be added to the decontaminated eluate solution 118 and/or the double decontaminated eluate solution 121, and the treated decontaminated eluate solutions 118, 121 may be transferred to a holding tank or to one or more of the high level waste tanks 101. In such embodiments, for instance, the decontaminated eluate solutions 118, 121 may be an 0.2M solution of sodium nitrate having a pH greater than 12 or any other suitable alkaline pH value. In this regard, the treated decontaminated eluate solutions 118, 121 may be reused in salt dissolution.
The system described above may be used until the lead ion exchange column 610 requires regeneration. The method of regenerating the lead ion exchange column 610 is discussed in more detail below. However, to accomplish regeneration, one or more reagents 110 (e.g., sodium hydroxide, sodium nitrate and/or the like) may be stored in one or more reagent tanks 109. The reagents 110 and reclaimed water 111 may flow to one or more eluent tanks 112 to form eluent solutions 113. The eluent solutions 113 may then be utilized in the regeneration of the lead ion exchange column 610. In this regard, the elution/regeneration cycle may be counter-current from oldest to the most recently eluted ion exchange column such that freshly eluted and regenerated ion exchange columns 114 will be placed on-line in the polishing position 630 and then sequenced forward as upstream columns 610, 620 experience cesium breakthrough.
In accordance with certain embodiments, for example, the system may operate at a treatment rate from about 1 gallon/min. to about 100 gallons/min. In other embodiments, for instance, the system may operate at a treatment rate from about 3 gallons/min. to about 50 gallons/min. In further embodiments, for example, the system may operate at a treatment rate from about 5 gallons/min. to about 25 gallons/min. In some embodiments, for instance, the system may operate at a treatment rate from about 7 gallons/min. to about 12 gallons/min. In certain embodiments, for example, the system may operate at a treatment rate of about 10 gallons/min. As such, in certain embodiments, the system may operate at a treatment rate from at least about any of the following: 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 gallons/min. and/or at most about 100, 75, 50, 40, 30, 25, 20, 15, 12, 11, and 10 gallons/min. (e.g., about 8-75 gallons/min, about 10-100 gallons/min., etc.).
In accordance with certain embodiments, for instance, the system may operate at a temperature from about 10° C. to about 60° C. In other embodiments, for example, the system may operate at a temperature from about 20° C. to about 50° C. In further embodiments, for instance, the system may operate at a temperature from about 30° C. to about 40° C. In certain embodiments, for example, the system may operate at a temperature of about 38° C. As such, in certain embodiments, the system may operate at a temperate from at least about any of the following: 10, 15, 20, 25, 30, 35, and 38° C. and/or at most about 60, 55, 50, 45, 40, and 38° C. (e.g., about 30-50° C., about 20-60° C., etc.).
In another aspect, a method for treating a liquid waste having at least one radionuclide in a salt solution is provided. In general, the method may include supplying the liquid waste to a plurality of cross flow filters from at least one high level waste tank; filtering the liquid waste via the plurality of cross flow filters to form a clarified salt solution; removing at least one radionuclide from the clarified salt solution via a plurality of elutable ion exchange columns filled with an ion exchange media to form an eluate and a decontaminated salt solution; and removing at least one radionuclide from the eluate via a first non-elutable adsorption component to form a dewatered radionuclide sorbent and a decontaminated eluate solution. Moreover, any and all disclosures made in relation to the system also apply to the method as described herein.
As shown in
As shown in
In this regard, in certain embodiments, for example, the elution/regeneration method may last from about 12 hours to about 48 hours. In other embodiments, for instance, the elution/regeneration method may last from about 18 hours to about 40 hours. In further embodiments, for example, the elution/regeneration method may last from about 20 hours to about 30 hours. In certain embodiments, for instance, the elution/regeneration method may last about 24 hours. As such, in certain embodiments, the elution/regeneration method may last for a time from at least about any of the following: 12, 15, 18, 20, 21, 22, 23, and 24 hours and/or at most about 48, 45, 40, 35, 30, 29, 28, 27, 26, 25, and 24 hours (e.g., about 18-26 hours, about 21-30 hours, etc.).
Moreover, according to certain embodiments, for example, the sRF may go through an elution/regeneration cycle after treating from about 25,000 gallons to about 75,000 gallons. In other embodiments, for instance, the sRF may go through an elution/regeneration cycle after treating from about 40,000 gallons to about 60,000 gallons. In further embodiments, for example, the sRF may go through an elution/regeneration cycle after treating about 50,000 gallons. As such, in certain embodiments, the sRF may go through an elution/regeneration cycle after treating a number of gallons of liquid waste from at least about any of the following: 25,000; 30,000; 35,000; 40,000; 45,000; and 50,000 gallons and/or at most about 75,000; 70,000; 65,000; 60,000; 55,000; and 50,000 gallons (e.g., about 40,000-65,000 gallons, about 50,000-75,000 gallons, etc.). In this regard, each elution/regeneration cycle may generate about 6,200 gallons of cesium-laden eluate and regeneration chemicals (i.e. eluent solutions 113) to be transferred to the one or more eluate tanks 119.
As shown in
While one or more example embodiments of the invention have been described above, it should be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. In addition, the embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention. Thus, it should be understood by those of ordinary skill in this art that the present invention is not limited to these embodiments since modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the scope and spirit thereof.
This application is a divisional application based upon and claiming priority to U.S. utility patent application Ser. No. 14/940,960, filed Nov. 13, 2015, which is based upon and claims priority to U.S. provisional application Ser. No. 62/079,368, filed Nov. 13, 2014. The foregoing applications are incorporated fully herein by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 62079368 | Nov 2014 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14940960 | Nov 2015 | US |
| Child | 16057921 | US |
