CA1241201A - Magnesium reduction of uranium fluoride in molten salts - Google Patents
Magnesium reduction of uranium fluoride in molten saltsInfo
- Publication number
- CA1241201A CA1241201A CA000479831A CA479831A CA1241201A CA 1241201 A CA1241201 A CA 1241201A CA 000479831 A CA000479831 A CA 000479831A CA 479831 A CA479831 A CA 479831A CA 1241201 A CA1241201 A CA 1241201A
- Authority
- CA
- Canada
- Prior art keywords
- uranium
- molten
- magnesium
- salt
- fluoride
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Manufacture And Refinement Of Metals (AREA)
Abstract
MAGNESIUM REDUCTION OF URANIUM
FLUORIDE IN MOLTEN SALTS
ABSTRACT OF THE DISCLOSURE
A method and apparatus are provided for reducing uranium fluoride with magnesium to form uranium metal or uranium alloys. The reduction is carried out in a molten-salt solution in which the metallic product sinks and sep-arates while the magnesium fluoride by-product dissolves into the molten salt or forms a solid precipitate outside of the metallic region.
FLUORIDE IN MOLTEN SALTS
ABSTRACT OF THE DISCLOSURE
A method and apparatus are provided for reducing uranium fluoride with magnesium to form uranium metal or uranium alloys. The reduction is carried out in a molten-salt solution in which the metallic product sinks and sep-arates while the magnesium fluoride by-product dissolves into the molten salt or forms a solid precipitate outside of the metallic region.
Description
I_GNESIUM REDUCTION OF RYAN
FLUORIDE IN OLDEN SALTS ~2~2~
__ BACKGROUND _ THE INVENTION
This invention relates generally to a method and appear-anus for reducing uranium fluoride by reaction with mug-noisome in a molten salt medium, thereby generating uranium as bulk metal, the process being accomplished at pressures and temperatures lower than those usually employed in come Marshall reductions of uranium fluoride by magnesium in pressure-containment vessels; likewise, the present invent lion offers a means to carry out substantially continuous reductions. Both continuous operations and operations at reduced pressures and temperatures offer economic and engineering advantages over commercial practice and other prior art.
Definitions: In this disclosure, unless otherwise specified, the unrestricted term "uranium" is defined to include substantially metallic alloys comprising at least 50 percent by weight in total of isotopes of the element with the chemical symbol, Us As examples, "uranium" may refer to so-called depleted uranium, DU, to natural uranium as reduced from natural ore, or to alloys of such forms of the element, e.g., DU containing 7.5 weight percent of niobium.
Likewise, "uranium fluoride" is defined to include substantially fluoride mixtures comprising at least 50 weight percent in total of one or more of the fluorides of isotopes of the element, Together or alone UF3, UF4, and UF6 will be present in "uranium fluoride" under this definition to a total of at least 50 percent, impurities such as UO2 may be present, and materials such as Nb2O5 or NbF5 may be deliberately added to form desired alloys directly upon reduction; likewise, the content of U may involve any isotopes in any proportions.
Lo As suggested above, most reductions of uranium fluoride to uranium are made by magnesium in pressure-containment vessels. For reactions to produce DU metal from UF4 (where no nuclear-criticality hazard is involved), the reductions on commercial scale are usually carried out in large, sealed reaction vessels made of heavy-walled steel which is carbon lined inside and otherwise coated with relatively inert materials. Reaction charges as large as 0.7 tons of blended mixtures of powdered UF4 and slightly more than enough magnesium to reduce all the UF4 to metal are packed into the reaction vessels. These charges are tamped and covered with inert material, then sealed to withstand high pressures.
Next, these sealed reaction vessels are placed in large furnaces and are heated to about 700C, at which tempera-lure the charge inside a vessel will ignite and generate temperature and high pressure of magnesium vapor. If the ignition produces a successful reduction of the UF4, the products of the reaction include molten uranium, molten MgF2, and liquid and gaseous magnesium. The reaction Yes-sots are cooled after ignition, the charge is dumped outland MgF2 is broken off the billet of metallic DU. Metallic DU is latter moved to a different heating unit and is remelted and alloyed. The MgF2 waste contains small amounts of uranium, primarily as UF3 and UO2, so the MgF2 must be shipped to central burial sites for radioactive materials.
Numerous things can go wrong with current reductions of UF4 as just described: (l) Handling UF4 in open rooms creates personnel and environmental and environmental hazards involving escape of the slightly radioactive dust.
FLUORIDE IN OLDEN SALTS ~2~2~
__ BACKGROUND _ THE INVENTION
This invention relates generally to a method and appear-anus for reducing uranium fluoride by reaction with mug-noisome in a molten salt medium, thereby generating uranium as bulk metal, the process being accomplished at pressures and temperatures lower than those usually employed in come Marshall reductions of uranium fluoride by magnesium in pressure-containment vessels; likewise, the present invent lion offers a means to carry out substantially continuous reductions. Both continuous operations and operations at reduced pressures and temperatures offer economic and engineering advantages over commercial practice and other prior art.
Definitions: In this disclosure, unless otherwise specified, the unrestricted term "uranium" is defined to include substantially metallic alloys comprising at least 50 percent by weight in total of isotopes of the element with the chemical symbol, Us As examples, "uranium" may refer to so-called depleted uranium, DU, to natural uranium as reduced from natural ore, or to alloys of such forms of the element, e.g., DU containing 7.5 weight percent of niobium.
Likewise, "uranium fluoride" is defined to include substantially fluoride mixtures comprising at least 50 weight percent in total of one or more of the fluorides of isotopes of the element, Together or alone UF3, UF4, and UF6 will be present in "uranium fluoride" under this definition to a total of at least 50 percent, impurities such as UO2 may be present, and materials such as Nb2O5 or NbF5 may be deliberately added to form desired alloys directly upon reduction; likewise, the content of U may involve any isotopes in any proportions.
Lo As suggested above, most reductions of uranium fluoride to uranium are made by magnesium in pressure-containment vessels. For reactions to produce DU metal from UF4 (where no nuclear-criticality hazard is involved), the reductions on commercial scale are usually carried out in large, sealed reaction vessels made of heavy-walled steel which is carbon lined inside and otherwise coated with relatively inert materials. Reaction charges as large as 0.7 tons of blended mixtures of powdered UF4 and slightly more than enough magnesium to reduce all the UF4 to metal are packed into the reaction vessels. These charges are tamped and covered with inert material, then sealed to withstand high pressures.
Next, these sealed reaction vessels are placed in large furnaces and are heated to about 700C, at which tempera-lure the charge inside a vessel will ignite and generate temperature and high pressure of magnesium vapor. If the ignition produces a successful reduction of the UF4, the products of the reaction include molten uranium, molten MgF2, and liquid and gaseous magnesium. The reaction Yes-sots are cooled after ignition, the charge is dumped outland MgF2 is broken off the billet of metallic DU. Metallic DU is latter moved to a different heating unit and is remelted and alloyed. The MgF2 waste contains small amounts of uranium, primarily as UF3 and UO2, so the MgF2 must be shipped to central burial sites for radioactive materials.
Numerous things can go wrong with current reductions of UF4 as just described: (l) Handling UF4 in open rooms creates personnel and environmental and environmental hazards involving escape of the slightly radioactive dust.
(2) Magnesium powder has some chance of igniting if it is sparked. (3) If the reaction does not seal properly, ~z~z~
flammable magnesium vapor mixed with UF4 dust can be released. (4) Moisture adsorbed on the UF4 powder can form U2 which reacts poorly at best, also CO which adds undesirable carbon to the metallic product, plus HO which coats the magnesium powder and may retard the reduction reaction, and other products which are unwanted. (S) Improperly coated carbon liners can introduce carbon into the metallic product. (6) Cracked carbon liners can permit the metallic DU to attack the steel and melt holes in it by forming low-melting iron-uranium alloy. (7) Leaky vessels can lead to loss of magnesium and incomplete reaction. (8) MgF2 can be trapped inside the billet. (9) Metallic uranium dispersed in the cooled MgF2 can ignite magnesium-vapor condensate when exposed to air. As corollary to all the aforementioned problems with current practice, there is need for new concepts in reduction as presented by the invention described here.
The problems just discussed are substantially a consequence of designing the system to retain magnesium vapor pressures far higher than atmospheric, i.e., at transient temperatures which will assure melting of both uranium and magnesium products of the reduction reaction.
Thus the magnesium vapor pressures, following current operating procedures, can rise to several hundred pounds per square inch in a routine reduction, and these pressures exhibit variability, depending upon the way ignition of the reduction takes place, i.e., temperature, time, location, etc.
The present invention avoids the high pressures just mentioned by carrying out the reactions at much lower temperatures in a molten-salt bath which is substantially .
~29~1Z(~
unreactive except that it dissolves magnesium, thereby reducing the magnesium vapor pressure relative to what it would have been for pure magnesium at the same temperature.
Likewise, to keep temperatures and pressures down, the MgF2 product may be generated in solution in molten salt rather than at the melting point of pure MgF2, which melts about 128C higher than uranium. Finally, the molten salt bath may be operated in a temperature gradient with its surface regions below the the boiling point of magnesium (about 1090) where the US reductions take place; then the solid uranium is allowed to sink to a warmer region where it melts (about 1133), coalesces, and may form a trap to pass uranium but hold molten salt, as will be discussed further.
Further advantages of the present invention over cur-rent practice are: (1) relatively small amounts of US rehandled at any time, so work can be done in a well-con-twined, protected, dry environment, (2) only small amounts of magnesium powder need be used at one time, and the atoms-phone can be inert, (3) the reaction can be carried out substantially at atmospheric pressure, (4) moisture either is not absorbed by the UF4, or the moisture can be removed before the reduction reaction takes place, (5) carbon liners are not used, (6) container steel is not used, (7) leaky vessels and escape of UF4 and magnesium vapor are avoided or can he more readily controlled than under current practice, (8) because the phase separations are slow and continuous, there is little chance that MgF2 will be trapped in the uranium, (9) uranium has little chance of becoming entrapped in the waste MgF2, and (10) dissolution or suspension of UO2 or UF3 in the molten-salt waste is anticipated to be minimal.
. .
The process depends upon choosing chemicals which are, first, either inert or yield desired chemical reactions, second, have suitable melting points, third, have proper solubilities or immiscibilities, and, fourth, have densities which will cause the the reactants and products of the reaction to move (by gravity or by mechanical action) in the right directions. In this way the process can be designed to be capable of substantially continuous operation, with streams of uranium product and MgF2-containing waste being cleanly separated as they move out of the reduction system.
In selection of the process chemistry, the usual react lion of UF4 with magnesium is accepted as the principal reaction. (But see uranium-fluoride definition given ear-tier regarding impurities and possible additives such as those for direct alloying.) The reaction is expected to take place in two steps:
2UF4 My = 2UF3 + MgF2 (1) 2UF3 + 3Mg = MU + 3MgF2 (2) or, if the reactions are combined:
UF4 + 2Mg = U + 2MgF2 (3) (If an additive such as Nb2O3 is present, it, too, will be reduced by the magnesium:
Nb2O5 + 3Mg = 2Nb + 3MgO (4) where the Nub is alloyed with the U formed by reaction 3.
Such coreduction is expected to result in large savings, because pure niobium is very expensive to buy alone, e.g., $60 per pound, and because the alloying process involves an expensive remelting of the coreduction product, in current technology.) Depending upon the content of the uranium fluoride and upon other factors, including economic factors, any of sex-I
oral halides of the alkali and alkaline earth metals may be selected to produce eutectic lowering of the melting point of the MgF2. Thus, Buff is probably a good solvent for magnesium, and the Buff can be recovered for recycle by dissolution in water; Cook is cheap and easy to recover for recycle, but it perhaps will introduce significant impure-ties for some uses; Nay may be useful if the liquid compound MgF2.NaF is present to stabilize the Nay. Similar lines of reasoning can be given for other alkali and alkaline earth halides.
To hold the magnesium and uranium fluoride reactants together, and to sink the light magnesium into the melt, compacts such as pellets are added to the molten-salt region region in which the reactions take place. Technology for forming such pellets is known to those versed in the art.
An excess of magnesium is maintained in the molten-salt region, as dissolved magnesium, so that (a) uranium recovery will be high, and (by radioactive contamination in the MgF2 by-product will be low, thereby reducing disposal problems.
Because the vapor pressure of magnesium is greater than one atmosphere at the melting point of uranium, one or more of four concepts is employed to reduce magnesium vapor-ization: First, a temperature gradient in the molten-salt region may be employed so that solid uranium may be formed at temperatures below the melting point of uranium and below the boiling point of magnesium, with the solid uranium subsequently sinking into hotter locations in the molten-salt region and melting there. Second, dissolving magnesium into the molten salt will lower the magnesium vapor pressure relative to that of pure magnesium at the same temperature.
Third, vaporized magnesium may be condensed and fed back ~241~20~
to the molten-salt region. Fourth, the system may be open-axed pressurized to pressures slightly greater than atoms-phonic, e.g., by a column of molten salt or by a loppers sure containment vessel.
Molten uranium may be used as a trap to retain molten salt but pass molten uranium. This concept is discussed further in the description of the drawings.
Prior art in UF4/Mg reductions offers neither contain-use processing nor operations to produce molten metal at low pressure. The need for the invention is demonstrated by the high cost and rate of failures of the current reduction practice in forming substantially pure uranium from UF4 and by the environmental and personnel hazards in current pray-lice.
SUMMARY OF THE INVENTION
The invention seeks to provide a method of reducing uranium fluoride to uranium by reaction with magnesium at near-atmospheric pressure.
Further, this invention seeks to provide compositions of molten salts suitable for carrying out reductions of uranium fluoride to uranium by reaction with magnesium at near-atmospheric pressure.
Still further, this invention seeks to provide methods of establishing near-atmospheric pressures of magnesium during reductions of uranium fluoride.
Still further, this invention seeks to provide the intro-diction of magnesium and uranium fluoride into a molten-salt region.
Still further, this invention seeks to provide maintenance of compositions in a molten-salt region.
flammable magnesium vapor mixed with UF4 dust can be released. (4) Moisture adsorbed on the UF4 powder can form U2 which reacts poorly at best, also CO which adds undesirable carbon to the metallic product, plus HO which coats the magnesium powder and may retard the reduction reaction, and other products which are unwanted. (S) Improperly coated carbon liners can introduce carbon into the metallic product. (6) Cracked carbon liners can permit the metallic DU to attack the steel and melt holes in it by forming low-melting iron-uranium alloy. (7) Leaky vessels can lead to loss of magnesium and incomplete reaction. (8) MgF2 can be trapped inside the billet. (9) Metallic uranium dispersed in the cooled MgF2 can ignite magnesium-vapor condensate when exposed to air. As corollary to all the aforementioned problems with current practice, there is need for new concepts in reduction as presented by the invention described here.
The problems just discussed are substantially a consequence of designing the system to retain magnesium vapor pressures far higher than atmospheric, i.e., at transient temperatures which will assure melting of both uranium and magnesium products of the reduction reaction.
Thus the magnesium vapor pressures, following current operating procedures, can rise to several hundred pounds per square inch in a routine reduction, and these pressures exhibit variability, depending upon the way ignition of the reduction takes place, i.e., temperature, time, location, etc.
The present invention avoids the high pressures just mentioned by carrying out the reactions at much lower temperatures in a molten-salt bath which is substantially .
~29~1Z(~
unreactive except that it dissolves magnesium, thereby reducing the magnesium vapor pressure relative to what it would have been for pure magnesium at the same temperature.
Likewise, to keep temperatures and pressures down, the MgF2 product may be generated in solution in molten salt rather than at the melting point of pure MgF2, which melts about 128C higher than uranium. Finally, the molten salt bath may be operated in a temperature gradient with its surface regions below the the boiling point of magnesium (about 1090) where the US reductions take place; then the solid uranium is allowed to sink to a warmer region where it melts (about 1133), coalesces, and may form a trap to pass uranium but hold molten salt, as will be discussed further.
Further advantages of the present invention over cur-rent practice are: (1) relatively small amounts of US rehandled at any time, so work can be done in a well-con-twined, protected, dry environment, (2) only small amounts of magnesium powder need be used at one time, and the atoms-phone can be inert, (3) the reaction can be carried out substantially at atmospheric pressure, (4) moisture either is not absorbed by the UF4, or the moisture can be removed before the reduction reaction takes place, (5) carbon liners are not used, (6) container steel is not used, (7) leaky vessels and escape of UF4 and magnesium vapor are avoided or can he more readily controlled than under current practice, (8) because the phase separations are slow and continuous, there is little chance that MgF2 will be trapped in the uranium, (9) uranium has little chance of becoming entrapped in the waste MgF2, and (10) dissolution or suspension of UO2 or UF3 in the molten-salt waste is anticipated to be minimal.
. .
The process depends upon choosing chemicals which are, first, either inert or yield desired chemical reactions, second, have suitable melting points, third, have proper solubilities or immiscibilities, and, fourth, have densities which will cause the the reactants and products of the reaction to move (by gravity or by mechanical action) in the right directions. In this way the process can be designed to be capable of substantially continuous operation, with streams of uranium product and MgF2-containing waste being cleanly separated as they move out of the reduction system.
In selection of the process chemistry, the usual react lion of UF4 with magnesium is accepted as the principal reaction. (But see uranium-fluoride definition given ear-tier regarding impurities and possible additives such as those for direct alloying.) The reaction is expected to take place in two steps:
2UF4 My = 2UF3 + MgF2 (1) 2UF3 + 3Mg = MU + 3MgF2 (2) or, if the reactions are combined:
UF4 + 2Mg = U + 2MgF2 (3) (If an additive such as Nb2O3 is present, it, too, will be reduced by the magnesium:
Nb2O5 + 3Mg = 2Nb + 3MgO (4) where the Nub is alloyed with the U formed by reaction 3.
Such coreduction is expected to result in large savings, because pure niobium is very expensive to buy alone, e.g., $60 per pound, and because the alloying process involves an expensive remelting of the coreduction product, in current technology.) Depending upon the content of the uranium fluoride and upon other factors, including economic factors, any of sex-I
oral halides of the alkali and alkaline earth metals may be selected to produce eutectic lowering of the melting point of the MgF2. Thus, Buff is probably a good solvent for magnesium, and the Buff can be recovered for recycle by dissolution in water; Cook is cheap and easy to recover for recycle, but it perhaps will introduce significant impure-ties for some uses; Nay may be useful if the liquid compound MgF2.NaF is present to stabilize the Nay. Similar lines of reasoning can be given for other alkali and alkaline earth halides.
To hold the magnesium and uranium fluoride reactants together, and to sink the light magnesium into the melt, compacts such as pellets are added to the molten-salt region region in which the reactions take place. Technology for forming such pellets is known to those versed in the art.
An excess of magnesium is maintained in the molten-salt region, as dissolved magnesium, so that (a) uranium recovery will be high, and (by radioactive contamination in the MgF2 by-product will be low, thereby reducing disposal problems.
Because the vapor pressure of magnesium is greater than one atmosphere at the melting point of uranium, one or more of four concepts is employed to reduce magnesium vapor-ization: First, a temperature gradient in the molten-salt region may be employed so that solid uranium may be formed at temperatures below the melting point of uranium and below the boiling point of magnesium, with the solid uranium subsequently sinking into hotter locations in the molten-salt region and melting there. Second, dissolving magnesium into the molten salt will lower the magnesium vapor pressure relative to that of pure magnesium at the same temperature.
Third, vaporized magnesium may be condensed and fed back ~241~20~
to the molten-salt region. Fourth, the system may be open-axed pressurized to pressures slightly greater than atoms-phonic, e.g., by a column of molten salt or by a loppers sure containment vessel.
Molten uranium may be used as a trap to retain molten salt but pass molten uranium. This concept is discussed further in the description of the drawings.
Prior art in UF4/Mg reductions offers neither contain-use processing nor operations to produce molten metal at low pressure. The need for the invention is demonstrated by the high cost and rate of failures of the current reduction practice in forming substantially pure uranium from UF4 and by the environmental and personnel hazards in current pray-lice.
SUMMARY OF THE INVENTION
The invention seeks to provide a method of reducing uranium fluoride to uranium by reaction with magnesium at near-atmospheric pressure.
Further, this invention seeks to provide compositions of molten salts suitable for carrying out reductions of uranium fluoride to uranium by reaction with magnesium at near-atmospheric pressure.
Still further, this invention seeks to provide methods of establishing near-atmospheric pressures of magnesium during reductions of uranium fluoride.
Still further, this invention seeks to provide the intro-diction of magnesium and uranium fluoride into a molten-salt region.
Still further, this invention seeks to provide maintenance of compositions in a molten-salt region.
3 Still further, this invention seeks to provide an appear-pa ~2~2~)~
g tusk for reacting uranium fluoride with magnesium to produce uranium.
Other aspects, advantages, and novel features of the invention will be set forth in part in the descriptions which follow, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The aspect and advantages of the invention may be realized and attained by means of instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method of the invention comprises:
providing a means for heating and containing molten salt, providing a substantially inert atmosphere within the said means for heating and containing molten salt, emplacing molten salt in the said means for heat-in and containing molten salt, thereby creating a molten-salt region, introducing uranium fluoride and magnesium into the said molten-salt region, allowing the said reaction of uranium fluoride with magnesium to take place, allowing the said uranium produced by the said reaction of uranium fluoride with magnesium to settle from the said molten salt, and independently removing the said uranium and the magnesium fluoride by-product of the said reaction of uranium fluoride with magnesium.
zap I
In a preferred embodiment, the reactants which form uranium, i.e., uranium fluoride and magnesium yin this case shown as compacts in the form of pellets) are dropped into a molten-salt region where the uranium product forms and set-lies into a molten-uranium region, and magnesium fluoride product dissolves into molten salt or forms a solid which can float on the molten salt.
In another preferred embodiment, compacts of uranium fluoride, magnesium, and Buff are dropped into a molten-salt region of uniform temperature where uranium product settles into a billet mold; meanwhile, excess molten salt is disk placed from its region and into a waste collector. Prefer-ably the molten salt has a eutectic temperature at least as low as 1150C.
In another preferred embodiment, compacts of uranium fluoride, magnesium, and Buff are dropped into a molten-salt region with cooled upper surface in which solid uranium product is formed, falls into a hotter region where it melts, and further falls into a molten-uanium region from which it displaces excess molten-uranium into a billet mold.
In another preferred embodiment, a condenser for trap-ping magnesium and dropping it to a return system is used to supply stirrers which pump magnesium into a molten-salt region where uranium fluoride is reduced.
In a final preferred embodiment, reactive compacts fall through magnesium floating on a molten-salt region.
In a still further aspect of the present invention in accordance with its purposes, the apparatus of the invention comprises:
a first containment means with at least one first entry means and, at lower elevation, at least one first .`_ ` I
I
11`
discharge means, molten uranium filling the said first containment means to the discharge elevation of the said first discharge means, a second containment means with at least one second entry means and, at lower elevation, at least one second discharge means, the said second discharge means being positioned within the said molten uranium and at an elevation lower than elevation of the said first discharge means, and the second entry means being positioned at a higher elevation than the said molten uranium, molten salt both at least partially filling the said second containment means and floating upon the said molten uranium, a means for introducing at least uranium fluoride and magnesium through the said second entry means and into the said molten salt, a means for collecting molten uranium which has formed in the said molten salt, has moved from the said molten salt, has passed into the said molten uranium, thereby passing through the said second discharge means and through the said first entry means, a means for discharging at least magnesium flu-oxide separate from the said first discharge means, and a means for providing an inert atmosphere in regions where reactants, i.e., uranium fluoride and magnesium, and the uranium product of the reaction, could be attacked by a reactive atmosphere.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in I
and form a part of the specification, illustrate various embodiments of the present invention and, together with the description, serve to explain the principles of the invent lion. In the drawings:
FIGURE 1 is a schematic illustration in cross section of an embodiment of an apparatus demonstrating the method - of the invention showing pellets of uranium fluoride together with magnesium dropping into a molten-salt region where the uranium product forms and settles into a molten-uranium region, and magnesium fluoride product dissolves into molten salt or floats.
FIGURE 2 is a schematic illustration in cross section of an embodiment of an apparatus demonstrating the addition of pellets containing uranium fluoride, magnesium, and Buff into a molten-salt region of uniform temperature above the melting point of uranium, where molten-uranium reaction product settles into a molten-uranium region and displaces excess molten uranium into a billet mold; meanwhile, excess molten salt is displaced from its region and into a waste collector.
FIGURE 3 is a schematic illustration in cross section of an embodiment of an apparatus demonstrating the addition of pellets containing uranium fluoride, magnesium, and Buff into a molten-salt region with cooled upper surface area in which solid-uranium reaction product is formed, falls into a hotter area where the solid uranium melts, then falls fur-then into a molten-uranium region from which it displaces excess molten uranium into a billet mold, which mold is not shown.
FIGURE 4 is a schematic illustration in cross section of a molten-salt region with magnesium condenser above for Sue returning magnesium which has vaporized, the magnesium being returned deep within the molten-salt region by stirrers.
FIGURE 5 is a schematic illustration in cross section of molten magnesium floating on molten salt so that restive compacts must fall through magnesium before whey enter a molten-salt region.
DESCRIPTION _ THE PREFERRER EMBODIMENTS
Among the preferred embodiments, Fig. 1 shows a glove box 5 with inert atmosphere 7 holding an inert-c~ramic container 9 and heater 11. Within the inert-ceramic con-trainer 9, there is a molten-salt region 13 into which react live compacts 15 fall as delivered by feeder 17. The molten-salt region 13 may vary in composition from about 60 mole percent of Buff with MgF2 and various impurities to about 40 mole percent of Buff. The compacts may be stoic-isometric mixtures of US and magnesium, they may contain compounds or metals of alloying elements, they may contain aft they may contain other additives. These compacts 15 are shown reacting and forming molten-uranium droplets 19 which fall into a molten-uranium region 21. Periodically, excess molten-salt-region material and molten-uranium-region material are removed, e.g., by ladling. Solid MgF2 may be floating on the molten salt.
Figure 2 again shows the glove box 5 with inert atmosphere 7. In this case the inert container 9 has been replaced by second inert container 29 which has an open bottom and by third inert container 31 which is shaped like a chemical beaker. Third inert container 31 holds molten uranium 33 which acts as a trap to hold up the molten-salt region 13. Again reactive compacts 15 are fed by feeder 17, and these compacts produce molten uranium droplets 19 which I
fall through molten salt-molten uranium interface 35, thereby forcing excess uranium out of the container lip 37.
Droplets of excess uranium 39 fall and form a billet 41 of uranium in billet mold 43. Excess molten salt 45, perhaps with MgF2 solid, discharges to waste container 47.
The system is heated by heaters 11; the furnace insulation is not shown, but the technology of heating and insulating furnaces is known to those versed in the arts.
Figure 3 shows the same second inert container 29, the same third inert container 31, and the same molten uranium 33 acting as a trap, all as in Fig. 2. However, the molten-salt region is now divided into two parts, a hot molten-salt region 51 and a cooler molten salt region 53, the latter region being below the melting temperature of uranium.
Reactive compacts 15 now fall into the cooler molten-salt region, form small crystals of solid uranium 55 which sink and form molten-uranium droplets of small size 57 which sink, cross the molten salt-molten uranium interface 35, and displace droplets of excess uranium 39. Excess molten salt 45 is discharged out the top. Heating is primarily by lower-position heaters as indicated by heater 11.
Figure 4 shows the system of Fig. 1 adapted for return of vaporized magnesium. A condenser 61, such as a heat pipe or a metal rod, condenses molten magnesium 63, which drips into a tube 65 which holds a column of molten magnesium 67 and stirrers 69. Operating the stirrers drives magnesium droplets 71 (or bubbles of magnesium vapor) into the molten-salt region 13 where the magnesium enters solution or reacts with uranium fluoride (not shown). Magnesium which does not dissolve recycles to the condenser 61.
Figure 5 again shows the system of Fig. 1 with cooled lZ4~Z~
upper region holding molten magnesium 75. Reactive compacts 15 or other forms of reactants fall through the molten magnesium 75 and start reaction before they reach the molten-salt region 13. The first uranium to fall is small crystals of solid uranium 55 which sink and form molten-uranium droplets of small size 57 which sink into the molten-uranium region 21.
g tusk for reacting uranium fluoride with magnesium to produce uranium.
Other aspects, advantages, and novel features of the invention will be set forth in part in the descriptions which follow, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The aspect and advantages of the invention may be realized and attained by means of instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method of the invention comprises:
providing a means for heating and containing molten salt, providing a substantially inert atmosphere within the said means for heating and containing molten salt, emplacing molten salt in the said means for heat-in and containing molten salt, thereby creating a molten-salt region, introducing uranium fluoride and magnesium into the said molten-salt region, allowing the said reaction of uranium fluoride with magnesium to take place, allowing the said uranium produced by the said reaction of uranium fluoride with magnesium to settle from the said molten salt, and independently removing the said uranium and the magnesium fluoride by-product of the said reaction of uranium fluoride with magnesium.
zap I
In a preferred embodiment, the reactants which form uranium, i.e., uranium fluoride and magnesium yin this case shown as compacts in the form of pellets) are dropped into a molten-salt region where the uranium product forms and set-lies into a molten-uranium region, and magnesium fluoride product dissolves into molten salt or forms a solid which can float on the molten salt.
In another preferred embodiment, compacts of uranium fluoride, magnesium, and Buff are dropped into a molten-salt region of uniform temperature where uranium product settles into a billet mold; meanwhile, excess molten salt is disk placed from its region and into a waste collector. Prefer-ably the molten salt has a eutectic temperature at least as low as 1150C.
In another preferred embodiment, compacts of uranium fluoride, magnesium, and Buff are dropped into a molten-salt region with cooled upper surface in which solid uranium product is formed, falls into a hotter region where it melts, and further falls into a molten-uanium region from which it displaces excess molten-uranium into a billet mold.
In another preferred embodiment, a condenser for trap-ping magnesium and dropping it to a return system is used to supply stirrers which pump magnesium into a molten-salt region where uranium fluoride is reduced.
In a final preferred embodiment, reactive compacts fall through magnesium floating on a molten-salt region.
In a still further aspect of the present invention in accordance with its purposes, the apparatus of the invention comprises:
a first containment means with at least one first entry means and, at lower elevation, at least one first .`_ ` I
I
11`
discharge means, molten uranium filling the said first containment means to the discharge elevation of the said first discharge means, a second containment means with at least one second entry means and, at lower elevation, at least one second discharge means, the said second discharge means being positioned within the said molten uranium and at an elevation lower than elevation of the said first discharge means, and the second entry means being positioned at a higher elevation than the said molten uranium, molten salt both at least partially filling the said second containment means and floating upon the said molten uranium, a means for introducing at least uranium fluoride and magnesium through the said second entry means and into the said molten salt, a means for collecting molten uranium which has formed in the said molten salt, has moved from the said molten salt, has passed into the said molten uranium, thereby passing through the said second discharge means and through the said first entry means, a means for discharging at least magnesium flu-oxide separate from the said first discharge means, and a means for providing an inert atmosphere in regions where reactants, i.e., uranium fluoride and magnesium, and the uranium product of the reaction, could be attacked by a reactive atmosphere.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in I
and form a part of the specification, illustrate various embodiments of the present invention and, together with the description, serve to explain the principles of the invent lion. In the drawings:
FIGURE 1 is a schematic illustration in cross section of an embodiment of an apparatus demonstrating the method - of the invention showing pellets of uranium fluoride together with magnesium dropping into a molten-salt region where the uranium product forms and settles into a molten-uranium region, and magnesium fluoride product dissolves into molten salt or floats.
FIGURE 2 is a schematic illustration in cross section of an embodiment of an apparatus demonstrating the addition of pellets containing uranium fluoride, magnesium, and Buff into a molten-salt region of uniform temperature above the melting point of uranium, where molten-uranium reaction product settles into a molten-uranium region and displaces excess molten uranium into a billet mold; meanwhile, excess molten salt is displaced from its region and into a waste collector.
FIGURE 3 is a schematic illustration in cross section of an embodiment of an apparatus demonstrating the addition of pellets containing uranium fluoride, magnesium, and Buff into a molten-salt region with cooled upper surface area in which solid-uranium reaction product is formed, falls into a hotter area where the solid uranium melts, then falls fur-then into a molten-uranium region from which it displaces excess molten uranium into a billet mold, which mold is not shown.
FIGURE 4 is a schematic illustration in cross section of a molten-salt region with magnesium condenser above for Sue returning magnesium which has vaporized, the magnesium being returned deep within the molten-salt region by stirrers.
FIGURE 5 is a schematic illustration in cross section of molten magnesium floating on molten salt so that restive compacts must fall through magnesium before whey enter a molten-salt region.
DESCRIPTION _ THE PREFERRER EMBODIMENTS
Among the preferred embodiments, Fig. 1 shows a glove box 5 with inert atmosphere 7 holding an inert-c~ramic container 9 and heater 11. Within the inert-ceramic con-trainer 9, there is a molten-salt region 13 into which react live compacts 15 fall as delivered by feeder 17. The molten-salt region 13 may vary in composition from about 60 mole percent of Buff with MgF2 and various impurities to about 40 mole percent of Buff. The compacts may be stoic-isometric mixtures of US and magnesium, they may contain compounds or metals of alloying elements, they may contain aft they may contain other additives. These compacts 15 are shown reacting and forming molten-uranium droplets 19 which fall into a molten-uranium region 21. Periodically, excess molten-salt-region material and molten-uranium-region material are removed, e.g., by ladling. Solid MgF2 may be floating on the molten salt.
Figure 2 again shows the glove box 5 with inert atmosphere 7. In this case the inert container 9 has been replaced by second inert container 29 which has an open bottom and by third inert container 31 which is shaped like a chemical beaker. Third inert container 31 holds molten uranium 33 which acts as a trap to hold up the molten-salt region 13. Again reactive compacts 15 are fed by feeder 17, and these compacts produce molten uranium droplets 19 which I
fall through molten salt-molten uranium interface 35, thereby forcing excess uranium out of the container lip 37.
Droplets of excess uranium 39 fall and form a billet 41 of uranium in billet mold 43. Excess molten salt 45, perhaps with MgF2 solid, discharges to waste container 47.
The system is heated by heaters 11; the furnace insulation is not shown, but the technology of heating and insulating furnaces is known to those versed in the arts.
Figure 3 shows the same second inert container 29, the same third inert container 31, and the same molten uranium 33 acting as a trap, all as in Fig. 2. However, the molten-salt region is now divided into two parts, a hot molten-salt region 51 and a cooler molten salt region 53, the latter region being below the melting temperature of uranium.
Reactive compacts 15 now fall into the cooler molten-salt region, form small crystals of solid uranium 55 which sink and form molten-uranium droplets of small size 57 which sink, cross the molten salt-molten uranium interface 35, and displace droplets of excess uranium 39. Excess molten salt 45 is discharged out the top. Heating is primarily by lower-position heaters as indicated by heater 11.
Figure 4 shows the system of Fig. 1 adapted for return of vaporized magnesium. A condenser 61, such as a heat pipe or a metal rod, condenses molten magnesium 63, which drips into a tube 65 which holds a column of molten magnesium 67 and stirrers 69. Operating the stirrers drives magnesium droplets 71 (or bubbles of magnesium vapor) into the molten-salt region 13 where the magnesium enters solution or reacts with uranium fluoride (not shown). Magnesium which does not dissolve recycles to the condenser 61.
Figure 5 again shows the system of Fig. 1 with cooled lZ4~Z~
upper region holding molten magnesium 75. Reactive compacts 15 or other forms of reactants fall through the molten magnesium 75 and start reaction before they reach the molten-salt region 13. The first uranium to fall is small crystals of solid uranium 55 which sink and form molten-uranium droplets of small size 57 which sink into the molten-uranium region 21.
Claims (10)
1. A method of reducing uranium fluoride to uranium by reaction with magnesium at near-atmospheric pressure comprising:
(a) providing a means for heating and containing molten salt, (b) providing a substantially inert atmosphere within the said means for heating and containing molten salt, (c) emplacing molten salt in the said means for heating and containing molten salt, thereby creating a molten-salt region, (d) introducing uranium fluoride and magnesium into the said molten-salt region, (e) allowing the said reaction of uranium fluoride with magnesium to take place, (f) allowing the said uranium produced by the said reaction of uranium fluoride with magnesium to settle from the said molten salt, and (g) independently removing the said uranium and the magnesium fluoride by-product of the said reaction of uranium fluoride with magnesium.
(a) providing a means for heating and containing molten salt, (b) providing a substantially inert atmosphere within the said means for heating and containing molten salt, (c) emplacing molten salt in the said means for heating and containing molten salt, thereby creating a molten-salt region, (d) introducing uranium fluoride and magnesium into the said molten-salt region, (e) allowing the said reaction of uranium fluoride with magnesium to take place, (f) allowing the said uranium produced by the said reaction of uranium fluoride with magnesium to settle from the said molten salt, and (g) independently removing the said uranium and the magnesium fluoride by-product of the said reaction of uranium fluoride with magnesium.
2. A method according to claim 1 in which the composition of the said molten salt comprises at least 50 percent by weight of halides of alkali metals, of alkaline earth metals, or of both.
3. A method according to claim 1 in which at least the top portion of the said molten-salt region is held at temperatures below the melting point of the uranium.
4. A method according to claim 1 in which the said uranium fluoride and the said magnesium dissolve at least partially in the said molten salt.
5. A method according to claim 1 in which the said molten salt has a eutectic temperature at least as low as 1150°C.
6. A method according to claim 1 in which the composition of the said molten salt is maintained substantially constant by additions of components of the said molten salt, thereby compensating for additions of magnesium fluoride introduced by the said reaction of uranium fluoride with magnesium.
7. A method according to claim 1 in which the said molten salt, being of density less than molten uranium, floats on molten uranium held in such configuration that the said molten salt acts as a trap to retain molten salt but pass molten uranium.
8. A method according to claim 1 in which at least some of the said uranium fluoride and the said magnesium are added as compacts.
9. A method according to claim 1 in which magnesium vaporized from the said molten-salt region is condensed and returned to the said molten-salt region.
10. An apparatus for reacting uranium fluoride with magnesium to produce uranium comprising:
(a) a first containment means with at least one first entry means and, at lower elevation, at least one first discharge means, (b) molten uranium filling the said first containment means to the discharge elevation of the said first discharge means, (c) a second containment means with at least one second entry means and, at lower elevation, at least one second discharge means, the said second discharge means being positioned within the said molten uranium and at an elevation lower than elevation of the said first discharge means, and the second entry means being positioned at a higher elevation than the said molten uranium, (d) a molten salt bath at least partially filling the said second containment means and floating upon the said molten uranium, (e) a means for introducing at least uranium fluoride and magnesium through the said second entry means and into the said molten salt, (f) a means for collecting molten uranium which has formed in the said molten salt, has moved from the said molten salt, has passed into the said molten uranium, thereby passing through the said second discharge means and through the said first entry means, (g) a means for discharging at least magnesium fluoride separate from the said first discharge means, and (h) a means for providing an inert atmosphere in regions where the reactants, uranium fluoride and magnesium, and the uranium product of the reaction, could be attacked by a reactive atmosphere.
(a) a first containment means with at least one first entry means and, at lower elevation, at least one first discharge means, (b) molten uranium filling the said first containment means to the discharge elevation of the said first discharge means, (c) a second containment means with at least one second entry means and, at lower elevation, at least one second discharge means, the said second discharge means being positioned within the said molten uranium and at an elevation lower than elevation of the said first discharge means, and the second entry means being positioned at a higher elevation than the said molten uranium, (d) a molten salt bath at least partially filling the said second containment means and floating upon the said molten uranium, (e) a means for introducing at least uranium fluoride and magnesium through the said second entry means and into the said molten salt, (f) a means for collecting molten uranium which has formed in the said molten salt, has moved from the said molten salt, has passed into the said molten uranium, thereby passing through the said second discharge means and through the said first entry means, (g) a means for discharging at least magnesium fluoride separate from the said first discharge means, and (h) a means for providing an inert atmosphere in regions where the reactants, uranium fluoride and magnesium, and the uranium product of the reaction, could be attacked by a reactive atmosphere.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000479831A CA1241201A (en) | 1985-04-23 | 1985-04-23 | Magnesium reduction of uranium fluoride in molten salts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000479831A CA1241201A (en) | 1985-04-23 | 1985-04-23 | Magnesium reduction of uranium fluoride in molten salts |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1241201A true CA1241201A (en) | 1988-08-30 |
Family
ID=4130332
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000479831A Expired CA1241201A (en) | 1985-04-23 | 1985-04-23 | Magnesium reduction of uranium fluoride in molten salts |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1241201A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108179432A (en) * | 2017-12-27 | 2018-06-19 | 中国科学院上海应用物理研究所 | A kind of electro-deposition method of uranium trifluoride |
-
1985
- 1985-04-23 CA CA000479831A patent/CA1241201A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108179432A (en) * | 2017-12-27 | 2018-06-19 | 中国科学院上海应用物理研究所 | A kind of electro-deposition method of uranium trifluoride |
| CN108179432B (en) * | 2017-12-27 | 2019-09-03 | 中国科学院上海应用物理研究所 | A kind of electro-deposition method of uranium trifluoride |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| SU1331435A3 (en) | Method and installation for production of rare high-melting metal | |
| CA1275811C (en) | Process for producing high purity zirconium and hafnium | |
| US2091087A (en) | Process for the production of pure beryllium | |
| US5082603A (en) | Method of treatment of high-level radioactive waste | |
| US4552588A (en) | Magnesium reduction of uranium fluoride in molten salts | |
| US2950962A (en) | Reduction of fluoride to metal | |
| US2782116A (en) | Method of preparing metals from their halides | |
| JPS61279641A (en) | Method for reducing chloride of zirconium, hafnium or titanium to metal | |
| CA1241201A (en) | Magnesium reduction of uranium fluoride in molten salts | |
| US4534792A (en) | Magnesium reduction of uranium oxide | |
| US3000726A (en) | Production of metals | |
| US4564507A (en) | Reductive decontamination of magnesium fluoride | |
| Moser et al. | Review of major plutonium pyrochemical technology | |
| US2890110A (en) | Production of plutonium from plutonium fluoride | |
| NO863742L (en) | ZIRCONIUM AND HAVNIUM WITH LOW OXYGEN AND IRON CONTENT. | |
| US4636250A (en) | Recovery of uranium alloy | |
| US5118343A (en) | Lithium metal reduction of plutonium oxide to produce plutonium metal | |
| US2830894A (en) | Production of uranium | |
| CA3090058C (en) | Continuous reprocessing of spent nuclear fuel | |
| US5104095A (en) | Apparatus for separating molten salt from molten salt or molten uranium or molten uranium alloy | |
| USH137H (en) | Process for reducing beta activity in uranium | |
| US4591382A (en) | Process and apparatus for recovering and purifying uranium scrap | |
| JP2003521583A (en) | Americium electrolytic refining | |
| Leland | Economically producing reactive metals by aerosol reduction | |
| RU2172787C1 (en) | Method of pyrometallurgical processing of wastes, depleted materials and used up articles |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |