Patent Application
20160225475
Contained herein is material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office patent file or records, but otherwise reserves all rights to the copyright whatsoever. The following notice applies to the software, screenshots, and data as described below and in the drawings hereto and Rights Reserved.
In an embodiment, this disclosure relates generally to methods and apparatus for nuclear waste remediation and to mechanical devices and techniques that are utilized for removal of granular media from confined spaces vessels and tanks).
The ability to isolate and manage specific radioactive ions is necessary for clean, safe, and secure radioactive waste management, which in turn is essential for the safe and cost-effective use of nuclear power. There exist numerous ion exchange waste water treatment systems in operation. Each of these systems comprise ion exchange (IX) vessels containing a specific media that is utilized to perform ion exchange with incoming waste water. Over time, the IX resin or media become loaded with captured ions and can no longer capture additional ions, therefore no longer treating the incoming waste water. Some systems, such as water softening systems, and some contaminated water treatment systems, regenerate the media within the vessels by washing in some manner to renew the media and allow it to capture additional ions. Some systems, especially those capturing radionuclides or other hazardous chemicals, are not regenerated and the radionuclides or contamination stays on the media within the vessel becoming a storage and disposal issue as the number of vessels accumulates.
To reduce the complexity and length of the Detailed Specification, Applicant(s) herein expressly incorporate(s) by reference all of the following materials identified in each numbered paragraph below. The incorporated materials are not necessarily “prior art” and Applicant(s) expressly reserve(s) the right to swear behind any of the incorporated materials.
Advanced Tritium System and Advanced Permeation System for Separation of Tritium from Radioactive Wastes and Reactor Water in Light Water Systems, Ser. No. 62/239,660 filed Oct. 9, 2015, which is herein incorporated by reference in its entirety.
GeoMelt Electrode Seal, Ser. No. 62/272,604 filed Dec. 29, 2015, which is herein incorporated by reference in its entirety.
Mobile Processing System for Hazardous and Radioactive Isotope Removal, Ser. No. 14/748,535 filed Jun. 24, 2015, with a priority date of Jun. 24, 2014, which is herein incorporated by reference in its entirety.
Balanced Closed Loop Continuous Extraction Process for Hydrogen Isotopes, Ser. No. 14/294,033, filed Jun. 2, 2014, with a priority date of May 31, 2013, which is herein incorporated by reference in its entirety.
Methods for Melting of Materials to be Treated, U.S. Pat. No. 7,211,038 filed Mar. 25, 2001, with a priority date of Sep. 25, 2001, which is herein incorporated by reference in its entirety.
Methods for Melting of Materials to be Treated, U.S. Pat. No. 7,429,239 filed Apr. 27, 2007, with a priority date of Sep. 25, 2001, which is herein incorporated by reference in its entirety.
In-Situ Vitrification of Waste Materials, U.S. Pat. No. 5,678,237 filed Jun. 24, 1996, with a priority date of Jun. 24, 1996, which is herein incorporated by reference in its entirety.
Vitrification of Waste with Continuous Filling and Sequential Melting, U.S. Pat. No. 6,283,908 filed May 4, 2000, with a priority date of May 4, 2000, which is herein incorporated by reference in its entirety.
AVS Melting Process, U.S. Pat. No. 6,558,308 filed Apr. 25, 2002, with a priority date of May 7, 2001, which is herein incorporated by reference in its entirety.
Advanced Vitrification System 2, U.S. Pat. No. 6,941,878 filed Sep. 26, 2003, with a priority date of Sep. 27, 2002, which is herein incorporated by reference in its entirety.
Applicant(s) believe(s) that the material incorporated above is “non-essential” in accordance with 37 CFR 1.57, because it is referred to for purposes of indicating the background or illustrating the state of the art. However, if the Examiner believes that any of the above-incorporated material constitutes “essential material” within the meaning; of 37 CFR 1.57(c)(1)-(3), applicant(s) will amend the specification to expressly recite the essential material that is incorporated by reference as allowed by applicable rules.
Aspects and applications presented here are described below in the drawings and detailed description. Unless specifically noted, it is intended that the words and phrases in the specification and the s be given their plain, ordinary,and accustomed meaning to those of ordinary skill in the applicable arts. The inventors are fully aware that they can be their own lexicographers if desired. The inventors expressly elect, as their own lexicographers, to use only the plain and ordinary meaning of terms in the specification and claims unless they clearly state otherwise and then further,expressly set forth the “special” definition of that term and explain how it differs from the plain and ordinary meaning. Absent such clear statements of intent to apply a “special” definition, it is the inventors' intent and desire that the simple, plain and ordinary meaning to the terms be applied to the interpretation of the specification and claims.
The inventors are also aware of the normal precepts of English grammar. Thus, if a noun, term, or phrase is intended to be further characterized, specified, or narrowed in some way,then such noun, term, or phrase ill expressly include additional adjectives, descriptive terms, or other modifiers in accordance with the normal precepts of English grammar. Absent the use of such adjectives, descriptive terms, or modifiers, it is the intent that such nouns, terms, or phrases be given their plain, and ordinary English meaning to those skilled in the applicable arts as set forth above.
Further, the inventors are fully informed of the standards and application of the special provisions of 35 U.S.C. §112, ¶6. Thus, the use of the words “function,” “means” or “step” in the Detailed Description or Description of the Drawings or claims is not intended to somehow indicate a desire to invoke the special provisions of 35 U.S.C. §112, ¶6, to define the systems, methods, processes, and/or apparatuses disclosed herein. To the contrary, if the provisions of 35 U.S.C. §112, ¶6 are sought to be invoked to define the embodiments, the claims will specifically and expressly state the exact phrases means for” or “step for, and will also recite the word “function” (i.e., will state “means for performing the function of insert function]”), without also reciting in such phrases any structure, material or act in support of the function. Thus, even when the claims recite a “means for performing the function of . . . ” or “step for performing the function of . . . ”, if the claims also recite any structure, material or acts in support of that means or step, or that perform the recited function, then it is the clear intention of the inventors not to invoke the provisions of 35 U.S.C. §112, ¶6. Moreover, even if the provisions of 35 U.S.C. §112, ¶6 are invoked to define the claimed embodiments, it is intended that the embodiments not be limited only to the specific structure, material or acts that are described in the preferred embodiments, but in addition, include any and all structures, materials or acts that perform the claimed function as described in alternative embodiments or forms, or that are well known present or later-developed, equivalent structures, material or acts for performing the claimed function.
A more complete understanding of the systems, methods, processes, and/or apparatuses disclosed herein may be derived by referring to the detailed description when considered in connection with the following illustrative figures. In the figures, like-reference numbers refer to like-elements or acts throughout the figures. The presently preferred embodiments are illustrated in the accompanying drawings, in which:
Elements and acts in the figures are illustrated for simplicity and have not necessarily been rendered according to any particular sequence or embodiment.
In the following description, and for the purposes of explanation, numerous specific details, process durations, and/or specific formula values are set forth in order to provide a thorough understanding of the various aspects of exemplary embodiments. It will be understood, however, by those skilled in the relevant arts, that the apparatus, systems, and methods herein may be practiced without these specific details, process durations, and/or specific formula values. It is to be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the scope of the apparatus, systems, and methods herein. In other instances, known structures and devices are shown or discussed more generally in order to avoid obscuring the exemplary embodiments. In many cases, a description of the operation is sufficient to enable one to implement the various forms, particularly when the operation is to be implemented in software. It should be noted that there are many different and alternative configurations, devices, and technologies to which the disclosed embodiments may be applied. The full scope of the embodiments is not limited to the examples that are described below.
In the following examples of the illustrated embodiments, references are made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration various embodiments in which the systems, methods, processes, and/or apparatuses disclosed herein may be practiced. It is to be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the scope.
Presented herein in an embodiment is an approach for integrating a vacuum drying system in combination with a pneumatic removal system to remove dry granular ion exchange (IX) media from spent ion exchange vessels for additional contaminated waste stabilization. The approach is automated and can be operated remotely to enhance worker safety. The approach may both prepare and retrieve spent IX media for additional final stabilization processes such as vitrification.
The gold standard for long-term disposal waste form is glass due to the very low leachability of the contamination out of the glass. As such the systems and methods disclosed herein prepare the spent ion exchange (IX) media and vessel for long-term disposal in a vitrified waste form that reduces both volume as well as dose considerations d to the self-shielding of the glass material. The approach further has utility for de-watering and removal of moist granular media from any confined vessel or tank. The approach removes excess water and dries the spent ion exchange media while still within the containment vessel and then, with the same equipment, pneumatically extract the dry media for further long-term stabilization such as vitrification. As such, the following patents are herein incorporated by reference in their entirety; U.S. Pat. No. 7,211,038 B2, U.S. Pat. No. 7,429,239 B2, U.S. Pat. No. 5,678,237, U.S. Pat. No. 6,283,908, U.S. Pat. No. 6,558,308 B2, and U.S. Pat. No. 6,941,878 B2.
In this concept, spent ion exchange (IX) media is removed from the current storage vessels and fed into either an In-Container Vitrification (ICV™) container or a Mobile Vitrification System (MVS™) where it is then converted to a very durable vitrified waste form. The treatment container for this concept may also serve as the storage container. In some embodiments the contents of four ISM vessels may be processed in each ICV container. A total of four completed ICV containers may fit into one of the existing Interim Storage Facility culverts such that the equivalent media of sixteen ISM vessels may be contained in each culvert, in some embodiments. Other embodiments may contain more or less media depending on conditions such as culvert size, storage container size, location size, amount of media to be contained, etc.
Disclosed herein is an approach to accommodate existing equipment and facilities while also adhering to a site dose objective of 1 Sv/hr or less on contact. In the SI system of units, a millisievert (mSv is defined as “the average accumulated background radiation dose to an individual for 1 year, exclusive of radon, in the United States.” 1 mSv is the dose produced by exposure to 1 milligray (mG) of radiation.
The following benefits will provide a cost-effective and safe approach to treat spent (contaminated) IX resin or media, while providing both near and long-term benefits:
In an embodiment, the systems and methods disclosed provide safe handling of radioactive and hydrogen-generating waste materials while protecting the workers and the environment from the incumbent radiological hazards; and produce a high-quality waste form in compliance with current and future onsite storage requirements (mitigates the need for future retreatment). The ICV process may be successfully deployed in a facility that is contact operated and maintained and may not require heavily shielded hot cell capability.
For proper explanations of the systems and methods disclosed herein, it may be necessary to describe some embodiments by referencing multiple figures in the same paragraph. Figures are mentioned accordingly.
Empty ICV containers 400a are transported from storage or a vessel preparation area. In some embodiments the ICV containers 400a will be placed on a transfer system 416 which may include rails 352 for simple transport through the ICV Treatment Facility 1. The IX media is removed from the ISM vessels 100 and transferred into an IX handling, system 510 where the IX media may be combined with additives to increase efficiency of vitrification. The IX media, which in some embodiments is mixed with one or more additives, will then be transferred to an empty ICV container 400b. The IX media may then be vitrified in the container 400b. As vitrification is being carried out, the volume of material within the ICV container 400b will decrease so IX media may be added throughout the process until the ICV container 400b is full.
In the ICV processing area 515, the filled ICV containers 400c are transferred to ICV cooling area 520 and cooled prior to transfer to storage. Cooled ICV containers 400d are transferred to storage at the completion of processing. Throughout the various processes in the ICV Treatment Facility 1 off-gases may be transferred and treated by an off-gas treatment system 560.
Waste handling and processing operations may be mobile or conducted at permanent installations such as pre-engineered metal buildings.
A central control room (not depicted) may provide for monitoring and control of operations. Alternatively, monitoring and control operations may be performed at a remote location and or may be mobile. Further, monitoring and control operations may be a combination of one or more of on-site, remote, and mobile.
Additional processes may be included. The processes may be performed in other orders. Each step of the depicted embodiment of the process is described in further detail below.
This concept provides a straightforward and simple approach to converting spent IX media into a high-quality and stable vitrified waste form. The melting of a blend of spent IX media and additives also referred to herein as “frit”, “glass formers”, and “glass chemistry modifiers”) may take place within an ICV container. In some embodiments, the ICV container is shielded. The ICV container provides a confinement boundary for the process and for the radionuclides in the waste and it provides shielding that mitigates radiation dose rates and reduces the need for the facility to provide additional shielding. In some embodiments, the ISM vessel processing area 300 provides the capability to receive vessels 100 and hold them as they are opened. In some embodiments the ISM processing area 300 receives four vessels at a time, however other amounts are possible. The IX media may be removed and delivered to the ICV container through a pneumatic transfer system. In some embodiments a skid-mounted off-gas system treats gaseous effluents from the ICV operation 515 and IX media vessel process area 300. An ICV container cool-down area 520 is provided to hold containers 400c until they are ready for shipping to an Interim Storage Facility.
Process Hazards Analyses may be performed at least once for each facility, regularly, or intermittently to ensure the safety of the process. Areas of focus for the Process Hazards Analyses may comprise retrieval d transfer of the spent ISM, the processing in the ICV container, and the off-gas treatment. The following factors relate to increasing the safety of the process:
In further discussion of
In some embodiments, one or more of the processes described herein may be mobile and or modular such as those described in Mobile Processing System for Hazardous and Radioactive isotope Removal, Ser. No. 14/748,535 filed Jun. 24, 2015, with a priority date of Jun. 24, 2014, which is herein incorporated by reference in its entirety.
Referring to
In some embodiments the crane or other lifting device 375 may place the one or more ISM vessels 100 into stations on rails 352 to convey them into the ICV Treatment Facility 1 (
Referring now to
Using waterjet cutting system 160, depicted in
This concept presented here is derailed graphically for a specific ISM vessel 100 type; the same basic approach with slightly modified tooling could be used for other ISM vessel 100 types and sizes.
Clamp 113 may secure the tool 160 during cutting. Once the cut is complete, the clamp 113 may further grip the flange 150 and remove it, as depicted in
Referring to
Once the ISM vessel flange 150 is removed, a temporary cover may be installed over the nozzle opening 161 prior to drying IX media 166. This is done to mitigate potential dusting of dried IX media 166 to the facility 1 (
When the target dryness is achieved for the spent IX media 166, the temporary cover on the nozzle opening 161 may be removed to allow access to the interior of the ISM vessel 100.
In the embodiment depicted in
In the embodiment of
The end of the vacuum tool 705 in the depicted embodiment is a suction head 701. The suction inlets 711 are placed on one side of the suction head 701 and on the other side are pressurized air jets 750. In some embodiments there are three pressurized air jets 750. This allows for material to be drawn into the suction head 701 on one side and blown away on the other. Because the ISM vessel 100 is typically round, this flow of air will circulate the IX media 166 from one side of the ISM vessel 100 to the suction side of the tool 705. The pneumatic jets 750 may also cut and mix the IX media 166. This will move any IX media 166 that is cohered together or outside the range of the vacuum 705. The bottom of the suction head 701 may comprise a grinding plate and cutting edges 720 which mechanically grind any material below the head 701. To fully clean the ISM vessel 100 the suction tube may be rotated slowly and moved down in to the ISM vessel 100 repeatedly. In some embodiments a clear window in the vacuum tool 705 will allow operators to see IX media 166 in the suction flow to determine if the tool position is effective or not. This process will continue downward until all IX media 166 has been removed from the ISM vessel 100.
Preemptive testing shows the viability of using a vacuum tool 705 to remove the IX media 166 from the ISM vessels 100. For these tests, two beakers were filled with IX media 166, and soaked in a 2.5% salt solution in water. The saltwater was decanted off after 24 hours and the first beaker was oven dried for 24 hours at 150° C. The second beaker was left out on a benchtop for 48 hours for the purpose of testing wet IX media 166. The compaction of the wet and dry IX media 166 was tested prior to the vacuum test. The contents of each beaker were then vacuumed using a standard shop vacuum. The testing showed that the vacuuming of both the wet and dry IX media 166 was successful; however, the vacuuming of the dried IX media 166 was easier and quicker than vacuuming the wet IX media 166. The testing validated that the IX media 166 could be readily vacuum extracted.
Water sluicing technologies also may be used for spent IX media 166 retrieval. An alternate embodiment for IX media removal from ISM vessels 100 is depicted in
Referring to the embodiment of
Spent IX media 166 may be blended with additives (also referred to herein as “frit”, “glass thrillers”, and “glass chemistry modifiers”) needed to produce a durable, leach-resistant glass waste form capable of meeting or exceeding industry standards. In some embodiments blending may take place in batches as individual ISM vessels 100 are emptied through pneumatic vacuum 705 retrieval. IX media 166 and additives may be blended as dry reagents inside a receiving unit such as an enclosed, shielded hopper. The receiving unit may be sized to be compatible with the ICV processing rate of 150 kg/hr. The receiving unit may be fitted with one or more mixing blades that will blend the dry IX media 166 with additives while preventing caking or buildup in the container.
The blended material may be fed into the ICV container 400 (
Several IX media are engineered zeolite-based aluminosilicate materials that will form a glass without additives. However, some additives may be used to maintain the processing temperature at or below 1250° C., in order to minimize Cs volatility. The whole rock oxide analyses of a few selected IX media (KUR-H, KUR-EH, and IONSIV IE-96) are shown in Table 1.
As shown in Table 1, above, KUR-H, KUR-EH, and IONSIV IE-96 contain relatively high proportions of the principal glass forming oxides; silica and alumina. While such compositions will make excellent glass, they will result in melt temperatures on the order of 1700 to 1800° C. The processing temperature may be lowered to 1250° C. by the addition of melt temperature and viscosity modifiers; i.e., sodium, calcium, and boron; the corresponding reagents to be added are sodium carbonate (Na2CO3), calcium carbonate (CaCO3), and boric oxide (B2O3).
The compositions given in Table 1 were used in conjunction with fixed values of boric oxide expressed as a weight percentage of the final glass. The amount of CaO and Na2O were then varied while holding the calculated melt temperature to 1250° C. Curves expressing these calculations are shown in
For the KUR-H and KUR-EH and IONSIV IE-96 ISM the data indicate Na2O percentages from 5.94% to 3.95% and the corresponding CaO percentages from 4.48% to 6.73%. Given that the KUR-H and Kur-EH IX media contains 5.81% Na2O and only 1.58% CaO, the lower sodium and higher calcium option was chosen. This translates into the following formulation presented in Table 2, below.
12%
To prepare the spent IX media as a feed thr the ICV container 400, the retrieved dry material may be blended with a glass former mixture tailored for the specific type of IX media 166. Using loss in weight screw feed systems, glass former mixture and IX media 166 may be fed into a screw feeder, or feed rate control system, that provides mixing and conveys the feed to the ICV container 400 as a relatively homogeneous feed stream, as described earlier in this disclosure.
The GeoMelt ICV process may be most efficient when used on inorganic waste matrices. Organic wastes can, however, be accommodated if combined with sufficient quantities of glass forming minerals (GFMs). Note that for optimal processing, the organic content of the resulting mixture should contain no more than 30 wt % organic content in some embodiments.
Spent organic adsorbents stages can be treated in much the same manner. Glass formers can include KUR-H or KUR-EH ISM along with adjunct materials such as boric oxide, soda ash, and lime to act as fluxing agents. The amount of titanium oxide that can be incorporated into the glass may include amounts up to 25 wt %. Similarly, titanium oxide is amenable to the same treatment. This adsorbent is assumed to be titanium dioxide subjected to a surface treatment that optimizes the adsorption of antimony (Sb). A commercial example of the product would be Metsorb® HMRG by Graver Technologies. The surface treatment compounds may not materially affect the gross composition of the resultant glass. Acting on this assumption a glass recipe may be formulated quite easily, provided that the maximum concentration of TiO2 in the resultant glass is stipulated.
Zeolites generally have compositions that result in adequate glasses without amendments. To attain a sufficiently low melting tempo re, fluxing agents may be added, as will be done with KUR-H and the other ISMs. Activated carbon can be treated by GeoMelt ICV, but may result in an extremely reducing environment. A source of oxygen may be introduced, either chemically or by bubbling.
GeoMelt ICV can be used for much of the wastes produced in removing harmful radionuclides from the water. Waste treatment strategies may be implemented where some significant synergies exist, since the processing of organic resins or sludges may need blending with quantities of GFMs. For the example above, titanate could be blended with KUR-H, KUREH, or IONSIV-96 to provide the bulk of the required GFMs. The GFMs could be spent inorganic ISM and mixed with other waste streams while ensuring not to exceed established site worker dose objectives. Spent KUR-EH could be used as the GFMs for the titanium and all of the organic streams.
ICV container 400 (
In some embodiments, the refractory lining 431 (
A starter path, which may comprise a mix of moderately conductive glass frit and graphite flake, may be installed on top of the base primary refractory layer 431 in some embodiments. Electrodes 421 are installed into the starter path and held in position until the ICV container lid 458 is installed. In some embodiments, the electrodes 421 are composed of graphite. In some embodiments the electrodes 421 are 150 mm in diameter. In some embodiments, two or more electrodes 421 may be utilized. The lid 458 (built in hood) contains and directs the process off-gas to an off-gas treatment system 560 (
The ICV container 400 is designed to receive the waste/glass former mixture, contain the vitrification process, and serves as the final disposal container for the vitrified waste. The ICV container 400 provides primary containment for waste received from the ISM vessels 100, the molten glass during processing, and the final waste product.
The assembled ICV contain 400 is moved to the ICV processing area by crane or other lifting/hoisting device. Once in the ICV processing area, the ICV container 400 is connected to the off-gas treatment system 560 (
Waste and additives are conveyed into the ICV contain 400 by a feed system. The initial batch and subsequent batches are fed to a predetermined level in the ICV container 400 correlated to volumetric discharges and verified by observation, which may comprise at least one infrared camera system in some embodiments.
The waste and additives are melted inside the ICV container 400 using electrical power supplied by the electrodes 421. A starter path may be used to initiate the melt at the base of the first batch feed pile. As melting ensues, the waste mixture densifies creating additional volume in the container allowing for additional waste to be fed and processed. The nominal power level required for processing in some embodiments is approximately 400 kW. The processing rate in some embodiments may be 150 kg/hr.
In some embodiments, each ICV container 400 may hold 4000 kg of glass, based on the volume available inside the refractory lining 431 and the density of glass. Using the glass formulation for KUR-H and KUR-EH ISM provided in Table 1, and taking into account loss on ignition (LOI), the mass of material that is converted to gas (primarily CO2) rather than entering the glass, a total of 3,550 kg of ISM may be treated in each melt, as shown in Table 3. In some embodiments, each ISM vessel 400 contains approximately 800 kg of IX media 166. Thus, in such embodiments, each melt will process the contents of approximately four ISM vessels 100. Total melt duration, at a processing rate of 150 kg/hr of total feed material (ISM and glass formers) will be approximately 33 hrs.
On completion of the melt, the ICV container 400 is disconnected from the off-gas treatment system 560 (
Off-gas evolving from ICV plus balance air (for regulating plenum vacuum and temperature in the ICV container 400) constitutes the off-gas routed to off-gas treatment 560 (
In some embodiments the off-gas system 560 (
The off-gas system 560 (
Although airflow through the ICV container plenum is minimized, there can be a small amount of particulate entrainment in the ICV off-gas. Off-gas from the ICV container 400 may be passed through a backpulsable sintered metal filter (SMF). The SMF stage in some embodiments comprises of two filters in parallel. In some embodiments more than two filters are configured in parallel. In some embodiments one or more filters may be included in series. The parallel configuration allows one filter to be taken out of service and the other brought online when recycling collected solids. In some embodiments, the SMF is located with sufficient elevation that particulate is returned to the ICV container 400 by gravity feed. In some embodiments, the SMF is located at a lower elevation with return to the ICV feed hopper by pneumatic transfer. SMFs are rated at 98.3 percent removal efficiency for 0.3 μm particulate. The off-gas entering the SMF may be sufficiently hot that condensation is precluded.
Other filters may be used. Baghouse filters may be used, however, long-term integrity of baghouse filters would be suspect in radioactive application. Additionally, standard High Efficiency Particulate (HEPA) filters may be used. The use of standard HEPA filters as a pre-filter would require physical change-out when the change in pressure approached the filters design pressure drop causing worker exposure issues and additional secondary waste that would have to be processed in the container. A cleanable filter such as the SMFs proposed is a much more efficient approach from a processing standpoint, greatly reduces worker dose and allows for chemical cleaning of the sintered filter in place and remotely.
In some embodiments, treated air exiting the scrub tank is saturated with water vapor and entrains water droplets, thus the exiting air, passes through a filter, which may be a High Efficiency Mist Eliminator (HEME). As contaminated working fluid from the venturi scrubbers collects in the scrub tank, it may circulate through an external loop to be processed through one or more filters to remove particulate, through selective ion exchange to remove soluble cesium, and through a cooler (as needed) before it is introduced at the venturi scrubber. Periodically spent filters and ISM may be transferred to the in-preparation ICV container 400 to be included in a subsequent melter run. Periodically, spent working fluid may be pumped out to an operating melter. Soluble components are retained in the melt and water is evaporated to be released through the off-gas treatment system 560 (
The air passing through the scrubber system may become saturated with water, thus water accumulation can be regulated by adjusting the operating temperature. The ideal operating temperature of the wet scrubber system is the temperature that prevents net accumulation of water. There is a primary cooling effect in the venturi scrubbers as the passing air saturates with water vapor. Additional cooling of the circulating working fluid (as needed) can be applied in the external loop. The working fluid of the wet scrubbing system can become acidic over time from the capture of acidic gases depending on the waste types being processed. Thus, the scrubbing system may include a caustic storage tank and pH adjustment tank to automatically regulate the pH of the working fluid.
Treated off-gas exiting wet scrubbing may be saturated with water vapor. In final conditioning, the treated off-gas may be heated (nominally 15° C. in some embodiments) to reduce relative humidity prior to final filtration. Final conditioning of the off-gas before discharge may be by HEPA filtration, though other filtration methods are possible, HEGA filtration in addition to HEPA filtration for removal of organic carbon and radioiodine may be utilized in some embodiments.
In some embodiments there are two parallel HEPA filter trains: one train normally operating and one on standby. The specific design of the HEPA could include any or all of the following components: regulating butterfly valve, round-to-rectangular transition (as needed), inlet test section, HEPA filter banks (in series as needed with combination test sections), outlet test sections, and rectangular-to-round transition (as needed). In some embodiments more or fewer filters may be incorporated. In some embodiments, one or more other filter types may be used.
In some embodiments, the HEPA filters are equipped for condensate collection consisting of condensate drain lines from the respective filter sections, collection sump, condensate removal pump, and collection tank. Periodically, spent HEPAs are transferred to the in-preparation ICV container 400 to be included in the next melter run.
In some embodiments there are one or more exhaust fans. In some embodiments there may be two or more exhaust fans configured in parallel and/or in series. In some embodiments, two exhaust fans are configured in parallel. One fan may operate continuously and the other may be on standby. The exhaust fans provide the motive force to move exhaust gases and vapors through the off-gas train, while maintaining the required vacuum in the ICV container 400. Variable frequency drives may be used to control fan speed. The exhaust stack may be designed to disperse treated gases to the atmosphere in compliance with local regulations. The exhaust stack may be equipped for flow monitoring, and may be equipped with all sample probes and devices required for stack gas analysis, data collection, and regulatory reporting. Stack monitoring may comprise one or more of the following:
Other capabilities may be included as needed and per the regulatory requirements.
Cooling of the ICV container 400 may take place in the ICV cooling area 520 (
Glass is the preferred waste form for high-level radioactive waste and has been used extensively to immobilize radionuclides from the environment in France, Germany, Belgium, Russia, United Kingdom, Japan, and the USA. Glass is chemically stable in terms of leachability, durability, and corrosion, as defined by several standard test methodologies, described below:
A comparison of the chemical durability of a GeoMelt glass and a reference glass used as the baseline for the U.S. Department of Energy's Hanford Site (located in the United States) is depicted in
Table 5, below, compares GeoMelt glass samples with standard specifications of high-level vitrified waste produced by JNFL and JAEA. The MCC-1 values for the JNFL and JAEA glass is given as Bulk Leach Rate (BLR, or total mass of all elements released), and are not directly comparable to PCT test results given above in Table 4. Table 5 compares JNFL (Rokkasho) and JAEA specifications with GeoMelt glass MCC-1 results. Note that the GeoMelt glass sample was subjected to an extended MCC-1 test duration (1557 days), and the results indicate that the dissolution rate from GeoMelt glass decreases with time. Bulk MCC-1 lead rates of the GeoMelt example given in Table 5 are comparable or lower than the JNFL and JAEA specifications.
In the case of IX media used to capture radionuclides, the chemical composition of the media is typically well known and consistent which provides a uniform feed stream from a glass former standpoint; however, the concentration of the radionuclides loaded onto the media in an ISM vessel can vary to some degree both vertically and radially within the ISM vessel. When the loaded media is removed from the ISM vessel and transported using conventional material handling mechanisms such as with the pneumatic system proposed herein to transfer the waste feed to the ICV container loading mechanism, mixing of the media occurs which serves to distribute and fluffier mix the radionuclide inventory thereby providing a more uniform feed prior to vitrification.
Once fed to one of the GeoMelt Treatment Facilities 1 (
To demonstrate the ability to provide a homogenous waste form, samples of the glass are collected both during the melting process and/or after the melt has cooled that allow for sample analysis to occur which can then be used to show homogeneity as well as other sample data of interest. The post melt sampling has proven to be very flexible and effective as an entire core sample of the treatment container can be collected either vertically or horizontally to provide representative samples of the vitrified product available from any location in the ICV container. Based on an unbiased sampling approach, glass samples from select intervals of the cores may be taken and submitted for appropriate analytical analysis (such as β/γ counting, ICP-MS, or XRF).
GeoMelt ICV glass is typically 5 to 10 times stronger than concrete in both tensile and compressive strengths. This strength is a benefit that helps minimize the potential for human and animal intrusion. Although the vitrified product is strong, it can be broken into manageable pieces and handled with conventional heavy equipment. Table 6 shows the strength and other advantages of GeoMelt glass compared to concrete.
The inclusion of sulfur in to the waste glass, typically as SOx, an inclusive term referring to SO2 and SO3, can be problematical for waste glass melters. The solubility of sulfur oxides in most glass formulations has been reported up to a weight percent of 2.05 as SO3. Exceeding this solubility limit can result in the formation of sulfur salts. These sulfur salts can then segregate and accumulate as a separate phase appearing as a yellowish layer at the top of the melter. This layer of molten ionic salts (MIS) is very corrosive and can cause damage to electrodes, other components of a melter, and the refractory linings of the melters themselves. Additionally, the formation of sulfur salts can increase the volatility of radionuclides such as cesium. Such occurrences are known to be problematic with conventional joule-heated melters. These melters are continuously fed and discharge from midlevel or the bottom of the melt chamber. This allows amounts of sulfur to accumulate over time on the surface, even if the feed has initially low sulfur content. Since they discharge from below the surface of the melt and the sulfur salts accumulate at the top, the salts are never allowed to discharge. The GeoMelt ICV melter is, in contrast, a batch operation where the melt and disposal vessels are one and the same. Provided that the raw feed does not exceed the sulfur limits imposed by the glass formulation there is not an opportunity for a sufficient amount of sulfur salts to accumulate to the point of being problematic. Much work on chemical modification to the waste feed stream has been done such as the demonstration of adding barium to increase sulfur solubility.
The addition of barium may increase the molten pool viscosity into a range where conventional melters cannot operate due to their inability to pour or drain their melters. The GeoMelt ICV process described herein is a batch process thus it does not require a pouring of glass. As a batch process it is capable of accommodating such formulation modifications as means to increase the sulfate loading. The primary waste streams targeted for this concept do not contain sulfur in concentrations exceeding the glass solubility limit so it is unlikely there will be any sulfur-related difficulties.
Each completed ICV container 400 (
Thermal calculations have been performed to establish bounding values for temperature in the vitrified waste and in the concrete wall of the interim storage culvert resulting from radioactive decay. A Computer Aided Design software configured for Finite Element Analysis, such as an ANSYS model, has been developed and initial results reported. These preliminary results indicate that the terminal temperature in the center of the glass will be about 200° C. and temperature rise in the concrete vault will be very small. These results seem reasonable for the thermal loading of 900 watts per ICV container. These temperatures will not cause unfavorable impacts on either the glass or the concrete.
Calculations using Microshield were performed to establish dose rates predicted for ICV containers. Various container configurations were reevaluated. The current round of calculations was reconciled with those done earlier. Higher dose rates for the current round of calculations expected because the earlier calculations assumed all the Cs was Cs-137 and current calculations include a contribution from Cs-134. Though Cs-137 dominates the curie content of the waste, the high energy of the Cs-134 gamma makes the Cs-134 contribution to the dose rates significant.
Calculations were made for containers with varying thicknesses of steel shielding from 1 inch (25 mm) up to 5.6 inches (142 mm). Results of these calculations are shown in
The GeoMelt ICV process may employ a power system which allows for variable power levels to the melt environment and variable voltage levels to be able to accommodate changes in melt resistance due to different waste properties and changes in the size of the melt. The power system may be divided into two main areas: 1) the power supply to the melt which provides the power for the melting process (which may be joule-heated in some embodiments), and 2) ancillary power to the balance of the system for such items as off-gas components (fans, pumps, heaters), instrumentation, heating and air conditioning (HVAC), lighting, and other low voltage needs such as for process control and data acquisition and facility needs.
The power supply system to the melt may employ a 600 kVA Scott-Tee connected transformer in some embodiments that produces variable voltage output through a range of operator selectable voltage taps. Power output is controlled at the primary side of the transformer with silicon control rectifier (SCR) technology, which uses a single potentiometer selectable for either voltage or current control. The Scott-Tee transformer is a system to convert primary 3-phase power (three-wire) to two secondary phases.
Transformers typically have several separate voltage tap settings ranging from >1000 volts to <150 volts. The voltage taps have corresponding increasing current ratings of similar amps per phase (150 A to >1000 Amps, respectively). The power supply to the other ancillary equipment such as the off-gas system, HVAC, lighting, pneumatic system, facility, etc. may typically be on the order of 150-200 KVA and may be designed to transform incoming power into voltages and frequencies applicable to the levels required for the equipment such as that designed for eastern Japan.
The entire GeoMelt facility, including both vitrification power and auxiliary equipment power, requires 850 kVA in some embodiments and can be designed to accept any standard incoming utility grid power level. A backup diesel generator may be utilized to provide energy for the operation of all essential equipment for personnel and environmental safety in the event that utility line power is interrupted. These include the off-gas system, data acquisition system, environmental and system monitoring equipment, heating and air conditioning, and system lighting. Activation of the generator is automatic upon the loss of utility line power, thus providing uninterrupted power to essential process equipment. Additionally, if the availability of grid power is limited due to remoteness or limited capacity, the entire power system can be designed to be supplied by a combustion-based generated power system. Additionally, power generation may be augmented by one or more alternative methods such as solar and wind power.
For the sake of convenience, the operations are described as various interconnected functional blocks or distinct software modules. This is not necessary, however, and there may be cases where these functional blocks or modules are equivalently aggregated into a single logic device, program or operation with unclear boundaries. In any event, the functional blocks and software modules or described features can be implemented by themselves, or in combination with other operations in either hardware or software.
Having described and illustrated the principles of the systems, methods, processes, and/or apparatuses disclosed herein in a preferred embodiment thereof, it should be apparent that the systems, methods, processes, and/or apparatuses may be modified in arrangement and detail without departing from such principles. Claim is made to all modifications and variation coming within the spirit and scope of the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 62110563 | Feb 2015 | US |
