Nuclear Wastes Technologies for Separations and Transmutation (1996) / Chapter Skim
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D SEPARATIONS TECHNOLOGY
D SEPARATIONS TECHNOLOGY
Pages 147-190
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From page 147... ...
Fast reactor cladding is essentially iron and chromium with very little nicked present. In processing of commercial spent oxide fuels, Zircaloy is removed by mechanical chopping of the fuel rods into segments, followed by dissolution of the spent nuclear fuel in nitric acid.
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From page 148... ...
A _ ~ A 1 ~ ~ ~ ~ _ ~ J ~ ~ w _ The single-stage separation factors in pyrochem~stry can be large for equilibria between liquid metal and molten salt phases, and cascades are not usually required for fuel recycle. Multistage equipment using short-stage-time centrifugal contactors originally designed for aqueous systems is being developed for those molten-salt/molten-alloy processes that require a high degree of purification.
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From page 149... ...
The extraction equipment used for liquid-liquid separation processes is however, to a first approximation, independent of the solvents used. Thus, new processes that may be developed using, for example, liquid ion exchangers, phosphine oxides, phosphoric acid derivatives, or solvent systems based on amides, may entail only simple changes in operating conditions rather than new plant equipment.
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From page 150... ...
Bismuth Phosphate Process In 1941 it was known that plutonium has multiple oxidation states. A greatly expanded investigation of the aqueous chemistry of plutonium on the tracer level was initiated, which included separations methods based on precipitation, organic solvent extraction, and other approaches.
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From page 151... ...
The uranyl ion was stripped from the solvent with dilute nitric acid later in the process. Like the Bismuth Phosphate Process that exploited the differences in solubility of plutonium phosphate between Pu+4 and PuO2+2 oxidation states, the REDOX process utilized changes in the plutonium and other actinides.
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From page 152... ...
NONAQUEOUS PROCESSES Fluoride Volatility Processing Uranium hexafluoride production processes were initially developed to produce feed for the gaseous diffusion process for uranium enrichment and became routine on the multiton per day scale. The final purification of the uranium from ore is usually by solvent extraction, and the recovered uranium oxide is reduced to the dioxide, hydrofluorinated with hot anhydrous hydrofluor~de, and then fluorinated with fluorine from a nonaqueous electrolytic cell.
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From page 153... ...
The resulting actinide metals can then be processed as if they were irradiated metallic reactor finals. In the Molten Salt Reactor Experiment application, the molten fluoride salt consisting of BeF2, 7LiF, ThF4, arid UF4 was used as the working fluid.
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From page 154... ...
The salt transport process (Steunenber~ et al. 19691 a Dvrochem~cal method for ~ ~ ~ ~ - 7 a, 7 A- ~ recovering actinide elements from spent fast-reactor finals, is an example of a sophisticated pyrochemical system.
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From page 155... ...
, has the advantages of high density, compact size, and fast kinetics as a consequence of the use of liquid metals, the high concentrations of the elements in molten salts, the temperatures employed, and the generally adequate element-to-element separation factors in the electrochemistry of moltensalt systems. The technologies required are under development and demonstration at present.
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From page 156... ...
The strontium and cesium fission products, as well as iodide and some of the rare earths, are retained in the KCVEiC! molten-salt waste stream and are selectively sorbed from the salt by contacting the molten salt with solid zeolites.
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From page 158... ...
However, to maintain the proper salt composition, the molten salt electrolyte would need to be adjusted on occasion by discard and replacement or by a new processing step (i.e., preconditioned' lithium-loaded zeolite. ANL is developing centrifugal contact reactors for use in cascades for "stripping"-reduction in this case -- of the rare earths and residual TRUs from the molten salt stream with an alloy of lithium and uranium in cadmium.
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From page 159... ...
As of May 1 993, there were still two processes under consideration, but the zinc magnesium process had been replaced by a lithium process and the salt transport process had been modified and subsequently has been abandoned. The elimination of the two processes previously under consideration, and modification ofthe salt transport process, eliminated the use of fluoride ions in the molten salt employed in the reduction step; fluorides caused degradation of the zeolites being considered as a waste form.
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From page 160... ...
| Sol vent Metal | Separation l .| E, aporation | MetalWaste ~ TRU Product Halide Slagging or Electrorefining Uranium Source: Argonne National Laboratory - Integral Fast Reactor Program, managed by the University of Chicago for the U.S. Department of Energy under Contract No.
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From page 161... ...
Clx 13861 CaO 8772 ~ SALT RECOVERY Cu 33500 ~ - ~ 800°C Mg 18000 Ca 5903 Pu 40 Am 4.5 MgCI2 20000 1~ SALT TR kNSPORT DONOR 8( 0°C ~i · 33500 Mg 18075 U 60 Pu 40 Am 4.5 Cm 0.2 Np 2.4 NM 10 RE 50 . , y _ Np 2.4 Cm 0.2 NM 10 RE 50 U 60 C 943 M9C44 SALT TRANSPORT | ~ 9 ACCEPTOR 8009C t MAGNI SIUM Z.' 9000 RETORT Mg 925 950°C 2 NCRETo:3' Am 16 Cm 0.9 RE 187 U 270 _ _ STMB.drw 1 O/1 5/93 ~ Includes Cal2 and CaTe CaCI2 2000 (FPs)
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From page 162... ...
OCI 249 (182 RE) Li2O4.9 Li1.2 TRU0.0007 U0.068 02/07/94 Includes Lil and U2Te Source: Argonne National Laboratory - Integral Fast Reactor Program, managed by The University of Chicago for the U.S.
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From page 163... ...
The rare earths and noble metal fission products would follow the waste streams from the IFR process. ALL has not yet published in the open literature process parameters documenting the proposed EWR process flowsheets, since the details of these proposed processes are "applied nuclear technology" and may not be made available to foreign interests unless specifically released by DOE.
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From page 164... ...
Although zeolites are proposed as a matrix for disposal of salt waste, the processing is still in such an early stage of development that is not now possible to identifier the specific nature of the optimum zeolite and the products or waste forms from the acting extraction processing. This scheme would probably also result in another new waste form for the metal waste as well; since the process to be developed has not been selected, it is not possible to further define the metal waste stream.
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From page 165... ...
MORRIS, ILLINOIS A second 300 MTU/yr EWE reprocessing plant was constructed with private funds at Morris, Illinois in the early 1970s. This plant was designed to operate on a hybrid fluoride volatility and solvent extraction process, rather than the usual standard PUREX process.
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From page 166... ...
This plant employed the basic PUREX process, using a centrifi~gal contactor for first-cycle extraction and pulsed columns for second- and third-cycle extraction. The head-end ofthis plant was designed for remote operation and maintenance in a large hot cell.
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From page 167... ...
These are readily removed quantitatively and rapidly Tom equipment by washing with dilute nitric acid. Experience Abroad FRANCE France is probably the most advanced nation in the world in the effective deployment of nuclear energy and in the resolution of fuel-cycle matters; Over 75°/O of that nation's electricity is currently derived from nuclear fission, and all of its spent Mel is scheduled for reprocessing.
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From page 168... ...
FUTURE SEPARATIONS PROCESSES This section surveys of a variety of separation technologies that have potential use in the transmutation processing systems or the nuclear wastes remediation program. Limitations of time and personnel determined the thoroughness of this survey and precluded an in-depth evaluation of every possible technology.
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From page 169... ...
Similar ligands could possibly be applied to processing and removal of Punch from dilute aqueous waste streams. It might also be feasible to use them in high-salt waste streams.
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From page 170... ...
Tramex in High Nitrate Solutions. High chloride systems with liquid anion exchangers such as trialkylam~nes or tetraalkylammonium salts have been used to extract and separate triand tetravalent actin~des from most other fission products and the trivalent lanthanides.
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From page 171... ...
Sofi-Donor Complexants. Good separation factors have been reported between trivalent lanthanides and trivalent actinides for solvent extraction systems based on complexants with "soR" donor groups (e g., nitrogen and sulfur)
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From page 172... ...
No documented reports were found in which supercritical fluid extraction provides a separation for actinides, sodium salts, or fission products in a way that could be advantageous for processing of nuclear wastes, nor is there particular reason to expect such ejects. ION EXCHANGE AND ADSORPTION Organic Resins.
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From page 173... ...
Several of the approaches described in the subsection Solvent Extraction are adaptable to the adsorption mode; that is, functional groups such as ethers, ketones, ester, and crown ethers can be attached to surfaces of solids In comparison with liquid-liquid extraction, solid absorbents usually require the use of fixed or fluidized beds rather than simple countercurrent flow, although countercurrent flow has been utilized in pulsed towers and systems of tanks, but this may be offset by little or no residual solubility of the sorbent in the waste. A more subtle difference is that the interaction between the functional group and the solute occurs in an aqueous environment for an adsorbent, as opposed to an organic environment for extraction.
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From page 174... ...
Facilitated transport membranes are impregnated with a chemical agent solar to the extractants used in solvent extraction processes. Regeneration of the agent occurs on the product side of the membrane.
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From page 175... ...
Work at LANE on plutonium recovery using OFFS and KrF2 is an example of the possibilities of using fluoride volatility. For the proposed ATW, a molten salt system of LiF/BeF2 is under consideration, based on the earlier developments of the ORNL-MSBR program (Fitzpatrick et al., 1992~.
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From page 176... ...
It involves columns heated on the inside and cooled on the outside and there are few pumping demands. There are ion exchange and solvent extraction process that could be applied with the usual limitations of these procedures in radiation fields.
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From page 177... ...
Alkali and alkaline earth elements, tellurium, europium, possibly samarium, and iodine fission products remain in the salt phase, while the rest of the rare earths and the noble metal fission products accumulate in the coppermagnesium-calcium alloy.
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From page 178... ...
Recovery of the TRU elements can be 99.9% with no significant waste Dom this salt transport step. The copper-magnesium donor alloy with uranium can be recycled to accumulate uranium until the latter DreciDitates.
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From page 179... ...
proposed a separate tail-end solvent extraction using a primary amine and pH adjustment with formic acid to remove technetium Dom the waste stream. It further proposed to use an amine extraction or ion exchange separation of the technetium remaining in the uranium nitrate product.
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From page 180... ...
EVAPORATORS Evaporation is already in use at Hanford and can be expected to have a prominent role in processing techniques for nuclear wastes. Fouling of heat transfer surfaces can be expected to be a problem.
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From page 181... ...
One stage of washing, recrystallization, or adsorption could take place for each cycle. This provides the equivalent of countercurrent flow, without actually removing the sludge , ion exchange resin, other solid, or water insoluble liquid Tom the tank until sludge washing is complete.
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From page 182... ...
For example, TRLEX is rated high based on its likely success and the immediate value of such a techr~ology in processing the defense wastes. By contrast, diphosphine oxides and diamides are given a medium priority, as they would serve the same purpose as TRUEX but have not been as finely evaluated.
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From page 183... ...
reprocessing Diamides and Defense wastes Advanced lab Whenever High/ diphosphines oxides partitioning studies developed medium reprocessing Molten Salt Reprocessing Readyforpilot- Nextdecade High plant tests Soft Donor Complexants Defense wastes Basic lab Whenever High/ partitioning research developed medium Dicarbollide Complexation Defense wastes Advanced lab Whenever Medium partitioning studies developed reprocessing Super Critical Fluid Defense wastes Basic lab Whenever Low Chromatography reprocessing research developed Organic Resins Defense wastes Advancedlab As soon as High . partitioning studies possible reprocessing pilot plant
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From page 184... ...
184 TECHNOLOGIES FOR SEPARATIONS AND TRANSMUTATION Inorganic Exchangers Defense wastes Basic to advanced As soon as High partitioning late studies possible Adsorption Defense wastes Basic to advanced As soon as Medium partitioning lab studies possible Ultrafiltration Defense wastes Advanced lab Whenever High Microfiltration studies developed Electrolysis Defense wastes Basiclab Whenever High/ research developed medium Facilitated Transport Defense wastes BasicIab Whenever Medium research developed Reverse Osmosis Defense wastes Basic lab Whenever Low research developed Dialysis Defense wastes Basic lab Whenever Low research developed Fluorides Reprocessing Advancedlab As soon as High research possible ,8-Diketones Reprocessing Advancedlab Next decade Medium research Chlorides Reprocessing Advanced lab Next decade Low research Atomic Vapor Partitioning Advanced lab Whenever Low reprocessing research developed Precipitation Defense wastes Basic lab As soon as Medium partitioning research possible Siderophore(microbial) Defense wastes BasicIab Whenever High/ research developed medium limson Weed Defense wastes Basic lab Whenever Medium research developed Chitin Defense wastes BasicIab Whenever Medium research developed
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From page 185... ...
. ngmeermg Handling and Drying of Defense wastes Pilot-plant Whenever High Sludges and Slurries tests developed Evaporators Defense wastes Pilot-plant Whenever High tests developed Extractors Defense wastes Pilot-plant Whenever High tests developed Engineenog Defense wastes Pilot-plant Whenever High Opportunities tests developed
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From page 186... ...
1956. Reprocessing of Reactor Fuel and Blanket Materials by Solvent Extraction.
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From page 187... ...
1992. Review of ORNE Molten Salt Reactor Experiment.
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From page 188... ...
1955. Survey of separations processes -- other than solvent extraction.
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From page 189... ...
1971. Recent progress in molten salt reactor development.
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From page 190... ...
Jay ~ ~-~ lAikonie`~ G No andI)
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