2,830,873 United States Patent Office Patented Apr. 15, 1958

2 active, so that any recovery process must be capable of being carried out by remote control. Second, 2,830,873 and uranium are members of the rare earth FLUORDE voLATILITY PROCESS FOR THE family and, although they do not have identical charac RECOVERY OF URANUM 5 teristics, the chemical characteristics are sufficiently close Joseph J. Katz and Herbert H. Hyman, Chicago, and that it does increase the difficulty of separation of these Erving. Sheft, Oak Park, I., assignors to the United two elements by chemical methods. States of America as represented by the United States An ideal separation process for the recovery of ura Atomic Energy Commission nium from neutron-irradiated uranium would include the No Drawing. Application May 10, 1956 O following characteristics. The process should be one capable of continuous operation. The process must be Serial No. 584,153 one which can be operated by remote control because of 25 Claims. (CI. 23-145) the radiation hazards involved. Furthermore, it is desir able that the non-radioactive uranium be separated in an The present invention is concerned with the separation 15 early step of the process from the radioactive fission and recovery of uranium from contaminants by a halo products, so that the further processing of uranium may genation and volatilization method. The invention is par be carried on without the shielding required for process ticularly concerned with the recovery of uranium from . ing radioactive materials. The efficiency of the separa contaminants arising from the neutron irradiation of ura 20 tion of the uranium from the plutonium and fission prod nium. w - lucts must be very good. If complete separation of ura At the present time nearly all nuclear reactors employ nium, plutonium and fission products is not achieved in uranium in one form or another as the primary fuel, a single continuous process, it is desirable that the frac The employment of uranium as a nuclear fuel in reactors tions containing the plutonium and/or fission products has produced a great need for efficient methods for sepa should be in as small bulk as possible. Thus a plutonium rating uranium from contaminants. The uranium used 25 fraction or a fission product fraction having a large bulk in reactors must be very pure. Therefore it must be sep of materials added during the processing is undesirable. arated from contaminants native to uranium ores as well It is desirable that the uranium fraction be obtained as as those introduced in processing the ores. After the the metal or in the form of a compound such as uranium uranium is neutron-irradiated in a reactor for a period which can be readily converted to the metal. of time, it must be separated from the nuclear reaction 30 also may be used directly as the products. These include the fission products which are feed material in isotopic separation processes. the elements having atomic numbers 32 to 64, inclusive, It is an object of the present invention to provide a and if the isotope U238 is present, it will also include the Volatilization method of separating uranium from con higher actinide elements such as and pluto taminants. nium. There are also various additional uranium mix 35 It is an additional object of the present invention to "tures from which it is desirable to recover purified ura provide a method of recovering purified uranium from nium. For example, a great deal of neutron-irradiated neutron-irradiated uranium. uranium has been processed to remove the plutonium Other objects of the present invention will be apparent from the uranium without removing the fission products 40 from the description which follows. from the uranium. Therefore it is now desirable to sep In accordance with the present invention uranium con arate and recover uranium from this partially processed taminated with other elements, for example the radio uranium containing the fission products and various chem active fission products, may be conveniently recovered icals which were added during the plutonium removal from such contaminants by a process the initial step of process. 45 which comprises dissolving said contaminated uranium There are several factors which make the recovery of in a in the liquid phase. This dissolution uranium from neutron-irradiated uranium a particularly Step effects a partial phase separation of the uranium and difficult problem. The normal starting material for a sep certain contaminants. The uranium is converted to the ... aration process for the recovery of uranium from neutron halogen fluoride-soluble uranium hexafluoride compound irradiated uranium is a metal uranium slug which has 50 whereas the of certain contaminating elements been irradiated in a neutronic reactor for a sufficient time are insoluble in liquid halogen fluorides and the reaction to produce fission products, and plutonium. These fission rate of halogen fluorides with certain other solid ura products and plutonium are normally present in about 1. nium contaminants is sufficiently slower than the reac part fission products and 1 part plutonium per 1000 parts tion rate with uranium that substantial portions of these ... uranium. A successful separation process must separate 55 contaminating elements will remain as solids in the liquid the uranium from the fission products and plutonium so phase halogen fluoride. These foregoing solids are then that the recovered uranium has not more than 1 part of Separated from the solution by a distillation step, or other fission products in 109 parts of uranium and not more convenient method of separating solids from liquid, such than 1. part of plutonium in 108 parts of uranium. There as filtration, centrifugation, etc. The uranium hexaflu are two main factors which complicate recovery proc 60 oride (UF6) is then separated from the balance of the esses. First, these fission products are exceedingly radio impurities and solvent by one or more distillation steps, 2,880,873 3 4. as will be more fully described in the following para portant factor in the reactivity of these solutions towards graphs. other materials such as uranium. Some measure of the The use of the halogen fluorides as fluorinating agents reactivity may be correlated with the conductivity of in the liquid phase provides several advantages over the the halogen fluorides. The order of the conductivity of use of . A liquid phase fluorination greatly re various halogen fluorides is as follows: duces the corrosion of equipment that is found with gase ous fluorination. Hurthermore, the health hazard in the TABLE I fluorination of radioactive fission products or materials containing fission products by gaseous fluorinating agents Compound Conductivity at 25° is greatly reduced by the fluorination in the liquid phase. 0 C. (ohm-1 cm.-1) The halogen fluorides are extremely reactive with wa BrF3------8.0XO-3 ter so that every precaution must be taken in the proc IFs---- 2.3XO-5 ess to avoid bringing the halogen fluorides in contact BrFs------8.4X107 with any aqueous phase. The materials of construction ClF3------3X10-9 (at 0° C.) for reactors also must be selected with some care. It has been found, however, that such common metals as iron, nickel, aluminum and copper readily form co The reactivity of the halogen fluorides toward uranium herent protective films in the presence of halogen fluo masses is in substantially the same order. However, it rides which make their use as construction materials tnust again be emphasized that by suitably increasing the 20 temperature and pressure of the reactor in which distill for handling the liquid halogen fluorides practical. Of lation is carried out any of these halogen fluorides will these construction materials nickel and high nickel al dissolve uranium masses. loys appear to be least affected by halogen fluorides and One aspect of the present invention is concerned with accordingly are favored for reactor construction. Alu a method of increasing the rate of dissolution of uranium minum, however, is nearly as satisfactory from the cor and similar metals by the halogen fluorides, such as bro rosion standpoint, and much less expensive for use in mine trifluoride. It has been found that the rate of reactor construction. dissolution of uranium metal in pure trifluoride While the process of the present invention is particu is very slow at room temperature. It is believed that larly adapted to the recovery of uranium from con this is probably due to the absence of the bromine tri taminated uranium metallic masses, it may also be used fluoride system cations which are believed to be the to recover uranium from contaminated uranium con prime cause of the attack on the metal. However, where tained in other forms. Thus, any uranium salt or salf uranium is maintained in contact with mass may be dissolved by the present process by a suit for a substantial period of time, it is found that the slow able adjustment of reaction temperature and pressure. initial rate of reaction will be followed after a period by The present process is particularly applicable to the re a much faster rate of reaction between the uranium and covery of purified uranium from the uranium wastes bromine trifluoride. This may be due to the accumula which are by-products of the recovery of plutonium from tion of a substantial amount of bromine trifluoride sys uranium by precipitation processes. These wastes are tem cations in the solution as a result of the formation usually primarily in the form of uranium salts such as of bromine and bromine fluoride in the initial, or "incu uranyl ammonium phosphate containing 200-600 parts 40 bation' stage of the reaction. It has been found in the per million of radioactive fission products with respect to course of this invention that the rate of reaction of bro uranium content. The process is, of course, equally ap mine trifluoride can be greatly increased over that of plicable to the recovery of any uranium isotope or com the pure bromine trifluoride by the addition of a ma bination of isotopes. terial to the bromine trifluoride solvent which will pro The halogen fluorides which can be used as dissolving duce bromine trifluoride system cations in the solvent. agents in the present process include various fluorides Thus, the addition of, for example, approximately 10 which are liquid at or about room temperature. Chlo mole percent bromine to a bromine trifluoride solution rine trifluoride, which has a boiling point of 11.8° C., will result in the formation of a fluoride solvent which may be used in the present process. The chlorine tri has a greatly increased reactivity toward uranium. While fluoride may be maintained in the liquid state by suit greater or lesser amounts of bromine may be added to able adjustment of temperature and pressure of the re the bromine trifluoride, it has been found that the addi actor. The other halogen fluorides which are included tion of more than 10 mole percent of bromine does not within the scope of dissolving agents for this invention increase the reactivity rate over that obtained with a 10 include , bromine trifluoride, bro mole percent bromine trifluoride solution and that this mine pentafluoride, and . There are is about the optimum concentration. several factors, such as cost, stability, reactiveness, avail 5 The addition of halogen fluoride system acids to the ability, etc., which enter into the choice of a particular bromine trifuoride solvent will also cause the produc halogen fluoride agent to be used under specific circum tion of cations in the solvent. A halogen fluoride Sys stances. On the basis of these and other factors, chlo rine trifluoride, bromine trifluoride, and bromine penta tem acid hay be defined as a compound that is a good (30 fluoride ion acceptor. Thus, antimony pentafiuoride, fluoride have been found to be the most satisfactory when added to bromine trifluoride, will greatly improve halogen fluorides for use in the present process. Cf the reaction rate of the bromine trifluoride solvent to these three, bromine trifluoride has been found to be ward uranium. Other fluorine system acids, such as most suitable for the recovery of uranium from neutron niobium pentafluoride and tin tetrafluoride, may also be irradiated uranium metal, chiefly because of its greater 65 used to increase the cation concentration of the solvent. reactivity. The increase in reactivity of halogen fluoride solvents The reactivity of the halogen fluoride liquids apparent with uranium, attained by the addition of a substance ly depends upon self-ionization. This self-ionization capable of producing fluoride system cations in the Sys tends to proceed in each of the halogen fluorides via tem to the halogen fluoride solvent, is further illustrated the simultaneous gain and loss of a fluorine nucleus and by the following examples tabulated in Table II. In the attached electron pair. That is to say, every com these examples masses of metallic uranium of the Specified pound in the System may be regarded as a fluoride ion weight were reacted with various solvents under substan donor or acceptor (and usually both). The concentra tially similar conditions of temperature and pressure. tion of fluoride system cations such as Brit and BrF+ The comparative rates of penetration and dissolving times in bromine trifluoride solutions is apparently a very im 75 are shown. 2,830,873 TABLE II

Uranium Penetra- Incubation Dissolution , Total Dissolving mixture (g) Dissolved tion Time after Dissolution (g) (mm/hr) (hrs.) Incubation. Time (hrs.) (hrs.)." 37 g. of BrF3------. 7. 1.3 2.5 2.0 4.5 44.g. of BrF3, 9.4 g of Bra- 7.05 ... 4 K. 1 1.6 ... 6 8.2g.of BrF3, 37.5g. of Bra. 7.04 2.7 K. 0.9 0.9 34 g. of BrF3, 4 g. of SbF5. 7.05 12, 2 .1 0.2 0.2--

Aparticular embodiment of the present invention is the volatile material analyzed for plutonium. The results concerned with the recovery of uranium from uranium are shown in the table. masses containing other actinide elements such as plu tonium. Of particular interest is the recovery of uranium TABLE II from neutron-irradiated uranium metal slugs containing 15 plutonium and fission products. It has been found that Time Temp. BrF3 Other (Mole Wolatile Pu the dissolution of uranium masses in accordance with the Net Pu (mg.) (hrs.). (C.) (Mole Percent) (Percent) foregoing methods results in the production of the urani Percent) um fluoride species, uranium hexafluoride. It has also 4. 60 ------100 ClF3. 0.00

been found that the foregoing methods of dissolution of 2 120 ------100 BrFs---- 0.00 uranium masses containing plutonium result in the pro 22 90 0.012 duction of the nonvolatile lower plutonium fluorides, plu 72 35 <8. 0.25 90 S6. 00 tonium tetrafluoride and/or plutonium trifluoride pre 6 100 4.0 dominantly, but that a portion of the volatile plutonium 24 90 4.0 fluoride, , is also produced. Plu-: tonium hexafluoride is a volatile compound having a melt The method which has been found most suitable for ing point of 50.7° C. and a boiling point of 62.3. C. removing excess bromine and bromine monofluoride dur Thus it will be seen that plutonium hexafluoride has vir ing the dissolution of uranium metal containing plu tually the same volatility as uranium hexafluoride which tonium comprises the addition of fluorine during the reac has a sublimation point of 56.4° C. Accordingly, re 30 tion. The fluorine reacts with the bromine and bromine covery of pure uranium hexafluoride from uranium hexa fluoride to form bromine trifluoride, thus limiting the fluoride contaminated with any substantial amount of concentration of these substances in the reaction zone, plutonium hexafluoride would be very difficult by distilla and incidentally regenerating the bromine trifluoride used. tion methods. Since these reactions take place substantially quantita It is an object of this modification of the present inven 35 tively, the net reaction of the dissolving step is substan tion to provide a method of dissolving uranium material tially containing plutonium in a halogen fluoride solution with out forming any substantial amount of a volatile plu tonium fluoride compound. . . . Other regenerants than fluorine may be used. For ex In accordance with the present invention, it has been 40 ample, reacts at higher tempera found that uranium material containing plutonium may tures of the order of 150° C. with bromine and bromine be dissolved in a halogen fluoride, and particularly fluoride to produce bromine trifluoride. A chlorine tri bromine trifluoride, with the formation of a minimal fluoride regenerant is another alternative. amount of a volatile plutonium fluoride if the by-products An alternative method of limiting the bromine and of the reaction, and particularly bromine and bromine 45 bromine fluoride in the reaction zone during the dissolu monofluoride, are continuously removed from the reactor tion of uranium contaminated with plutonium comprises zone during the dissolution step. The bromine and the removal of these products by distillation or similar romine monofluoride reaction products can be removed methods. For example, a distillation tower can be added from the reaction zone by reacting them in the reaction to the dissolver with a constant takeoff of the light end zone with a suitable reactant, such as fluorine. Alterna 50 to a separate receiver. Since the bromine and bromine tively, they can be distilled from the reaction zone con monofluoride have much lower boiling points than ura tinuously, thus effectively removing them from the reac nium hexafluoride these will distill off without loss of tion zone. The bromine and bromine monofluoride form the uranium hexafluoride. Another method would be fluoride system cations in the bromine trifluoride solvent, by means of an inert gas sparge of the dissolution zone and it is believed that it is these cations predominantly 55 followed by a scrubbing tower to remove the volatile com which react with the plutonium to form plutonium hexa ponents of the sparge. In either method the final con fluoride. The limitation of these fluoride system cations densate could be treated with fluorine, bromine penta ... in the reaction zone will have a tendency to decrease fluoride or to regenerate the bromine the rate of dissolution of the uranium. This decrease in trifluoride for further use in the dissolver. rate of reaction, however, may be compensated for by 60 The choice of dissolution step of the process of the increasing the reaction zone temperature. It is desirable present invention depends upon whether plutonium is pres to carry out the dissolution step of this modification at ent in the uranium mass as has been pointed out. The a temperature of between approximately 100 and 160 Subsequent steps of the process, however, are the same, whichever dissolution step is used. ... C., and preferably about i30 C., in order to achieve a 65 If neutron-irradiated uranium is the starting material, : suitable uranium dissolution rate. . - the plutonium and a substantial portion of the fission The very considerable decrease in the production of products present may be separated from the uranium volatile plutonium fluorides obtained by employing the during the process of the dissolution step. Certain of the process of this modification of the present invention is fission products, such as zirconium and cerium, have very demonstrated in the examples tabulated in Table III. In 70 slow reaction rates with bromine trifluoride, so that these these examples pieces of plutonium wire were reacted fission products and contaminants may not be converted with various halogen fluoride solvents. The constitution to the fluoride form during the dissolution step. Other of the solvents and the conditions of the dissolutions are fission products and contaminants, such as the alkali shown in the table. Upon completion of the reaction the metal, cesium, and the alkaline earth, barium, form ex volatile material was separated from the residue and 75 tremely nonvolatile fluorides. Still other contaminants, 2,830,878 7 b 8 such as lanthanum and the other rare earths, form fluo The only fission product fluoride more volatile than ura rides nonvolatile and also insoluble in bromine trifluoride. nium hexafluoride which is present in substantial amounts Fission products of these types may therefore be readily in the solution of uranium hexafluoride after the cooling separated from uranium by dissolving the uranium in a time necessary to permit the radioactive decay of short halogen fluoride such as bromine trifluoride and then dis 5 lived fission products has elapsed is hexafluo tilling the volatile components of the dissolution mixture ride. The distillation of the light fraction from the from the dissolving chamber. The distillate from this uranium fluoride heavy fraction may be carried out either step will comprise the halogen fluoride dissolving agent in a batch still or in a continuous-process still. The still and all fluorides which are more volatile than the halo should be operated at such a temperature and pressure gen fluoride. It is therefore preferable that the halogen 0. that a solid uranium hexafluoride phase is not formed in fluoride be one which is less volatile than uranium hexa the still. It is desirable that the very volatile fission prod fluoride, such as bromine trifluoride. This halogen fluo uct fluorides such as be taken off ride will then remain as a solvent (or suspending agent) from the still overhead. The uranium hexafluoride for plutonium and fission product fluorides when the should be maintained in the still bottoms as a liquid, uranium hexafluoride is removed. This makes possible either by means of pressure during the distillation or the use of a continuous fractionation process for the dis dissolved in a suitable solvent, such as bromine trifluo tillation separation of uranium hexafluoride. if a solvent ride, less volatile than uranium hexafluoride. A buffer more volatile than uranium hexafluoride is employed, the zone may be formed between the major constituents, the uranium hexafluoride must be removed from a batch still, light elements at the top of the still and the heavy ele which is necessarily of fairly large capacity to accommo 20 ments at the bottom of the still. and date the large volume of uranium hexafluoride processed, bromine pentafluoride are suitable buffer zone constitu but which retains as a botton residue only the small ents. These constituents are likely to be present as a amount of plutonium and fission products deposited there result of the dissolution step operation, but additional on. The plutonium and fission products have been found amounts of these may be added if desired. When a batch to deposit on the surface of the reactor vessel requiring 2 5 still operating at atmospheric pressure is used, the ura a separate step to remove them which to some extent in nium hexafluoride cannot be separated from the more terferes with the continuity of the uranium distiilation volatile constituents if a liquid phase must be maintained operations. For this reason, bromine trifluoride is the at all times. Therefore, if a moderate pressure still is halogen fluoride which is preferred as the distiilation enployed, chlorine trifluoride may be added to the solu reagent in the treatment of neutron-irradiated uranium. tion to provide a considerable forerun of volatile material The dissolution may be operated as a continuous dis while remaining volatile impurities act as a solvent for solution process with the volatile materials being distilled the refluxing uranium hexafluoride when the still head therefrom. In this case, there should be a limited surface is below the triple point of uranium hexafluoride (64.02 to the dissolver and a provision for bottom takeoff of the C. at 1137 mm. Hg). insolubles in a slurry of the solvent. Alternatively, the 35 Following the separation of the light fraction, the final dissolution may be operated as a batch step. In this case, step of the uranium recovery process comprises a distill a container in the dissolver such as an aluminum capsule lation step to separate uranium hexafluoride from the could be used as a container for the plutonium and non solvent and the less volatile fission product fluorides. In volatile and insoluble fission products. Another alterna this step the residue from the light fraction still is again tive is a fluoride carrier for plutonium which can be in 40 distilled and the volatile uranium hexafluoride thus sepa cluded in the dissolving medium. Aluminum fluoride rated from the less volatile fission product fluorides and which is insoluble in bromine trifluoride is a satisfactory the bromine trifluoride solvent. Conventionai type dis reagent. The aluminum fluoride presents a large surface tillation apparatus may be used. Contrary to what for the adsorption thereon of the plutonium and the slurry might be expected from normal distillation experience in of the aiuminum fluoride containing adsorbed plutonium view of the fairly close ranges of some of the fission could be readily removed from the dissolver vessel and products, substantially complete decontamination from then dissolved in aqueous medium for further processing. the less volatile products is obtained in this step. This is In a concentration process for the concentration of the probably attributable to the fact that many of the fission plutonium the plutonium fluoride could also be removed product species form complexes with the bromine trifluo from the surface of a dissolver vessel by an aqueous wash 5 O ride solvent which are retained in the nonvolatile phase and the plutonium then concentrated from the wash. during the distillation step. Following the separation of the volatile fluorides from The bromine and bromine monofluoride side products the nonvolatile fluorides and other residue the next step of the reaction may be regenerated to bromine trifluoride in the present process can comprise the separation of the by contacting these products with fluorine. Similarly, the fission product fluorides which are more volatile than ura : 55 bromine pentafluoride may be reacted with bromine at nium hexafluoride from a heavy fraction comprising ura 150 C. to regenerate bromine trifluoride. The excess nium hexafluoride, the bromine trifluoride solvent, and bromine trifluoride and regenerated bromine trifluoride fission product fluorides which are less volatile than lira may then be recycled into the process. Should it for any nium hexafluoride. The volatile fission product fluorides reason be undesirable to recycle the laiogen halide into are those shown in the following table. 60 the process, the excess halogen halide may be contacted TABLE IV with a gaseous hydrogen halide such as hydrogen or hydrochloric acid to form water-soluble products. For Volatile fission product fiuorides example, when bromine trifluoride is treated with gaseous hydrochloric acid, the products are , bro Boiling Point (or Subl. Melting Point mine and chlorine, all of which are water-soluble. These Pt.) (o C.) (o C.) water-soluble products may then be treated with water to form solutions thereof. The smooth, nonvicient re action of these products with water is in sharp contrast with the violent reaction of water with the halogen halides. Now that the process has been described, it may be further illustrated by the following examples. in Ex ample is described a laboratory-scale test of the process "Triple point, 75 in which small-scale batch equipment was employed. 2,880,873 9 10 With laboratory equipment it is, of course, impractical first overhead cut comprised essentially 0.1 mole BrFs to obtain, both high yields and high decontamination and 99.9% of the tellurium originally present in the sam factors. However, the examples does illustrate the appli ple (as TeFs). A second fraction distillate taken over cability of the process to large-scale work. head comprised 49.9 moles of BrFs and 4.0 moles UFs. 5 This fraction was recycled for subsequent dissolution EXAMPLE I operations. The residue - which was removed from the bottom of the fractionation column comprised 46 moles UFs dissolved in 50 moles BrF3. This residue was in A 109 gram slice of a uranium slug which had been troduced into the product fractionation column. The irradiated in a nuclear reactor for 84 days and then O product fraction distilled from this column comprised 42 cooled for 70 days was contacted with 806 grams of inoles UF6 containing less than 0.01 moie BrFs, less than BrF3. The dissolver vessel, which was made of pre 0.01 mole BrF3, and less than 0.1% of the original telluri fluorinated nickel, was maintained at approximately um (as Tefs). The residue from this product fraction 135 C. 66 grams of fluorine was added to the reactor ation column, consisting of 50 moles BrF3 and 4 moles by bubbling it through the reaction mixture over the UFs, was recycled to the dissolving step. four-hour period which it took to dissolve the uranium While the process has been described primarily as ap slice. The radioactive fission products contained in the plied to the processing of neutron-irradiated uranium it slice amounted to a total of 1.1x106 millivolts of gamma is equally well suited for treating uranium-containing ores activity and 2x100 counts per minute of beta activity. or any uranium-containing intermediate products ob The gamma activity was measured with a high-pressure tained in the processing of ores including waste ma ionization chamber and vibrating reed electrometer. This terials. Thus, the so-called ore concentrates obtained instrument had been calibrated against a standard cobalt by ore dressing procedures have been successfully sub source and it was found that one rutherford (106 disinte jected to the process of this invention. Likewise, scrap grations/sec.) of Co60 activity (2 gammas/disintegration metal containing uranium, slag ob at 1.2 million electron volts) equaled 410 millivolts. The tained in the reduction of with mag predominant beta-emitters were tellurium, 2x108 counts/ nesium, and uranium tetrafluoride-containing materials min.; ruthenium, 2.5x109 counts/min.; and zirconium, have been found suitable starting materials for processing 2.3 x 109 counts/min. The dissolver solution, upon com according to this invention. pletion of the dissolution step, was distilled through a first The process can be applied to materials containing the column and a fraction collected containing UFs and BrF5. 30 uranium in relatively dilute form, such as to the above Additional BrFs was added to this cut and the mixture mentioned ore concentrates; however, it has been found distilled through a second column. The final cut actually advantageous in such instances slightly to modify the contained an appreciable amount of BrFs. It was found, process. It was found that a prefluorination step with however, that even with this laboratory technique decon hydrogen fiuoride at about 600 C. for the conversion of tamination factors of 105 for gamma and 10 for beta 3 5 the anions other than uranium to their fluorides and of the were obtained by the two distillation steps. The decon uranium to the tetrafluoride brought about a considerable ...tamination factor is defined as the ratio of impurity pres saving in the comparatively expensive bromine trifluoride; ent per unit weight before processing to that in the final a second fluorination step with bromine trifluoride ac product. . cording to this invention is subsequently used to convert The following example illustrates application of the 40 the uranium tetrafluoride to the hexafluoride. The bro ce present process, as a batch operation upon a pilot plant mine trifluoride preferably contains a small quantity of an scale, namely, 10 kilograms of neutron-irradiated ura acid ansolvide which is a substance capable of producing nium as the initial feed. fluorine-system cations in said solvent. An acid ansolvide 4.5 yields, either by direct dissociation or by interaction with EXAMPLE II the solvent, in this case, with bromine trifluoride, the cat ion characteristic of the solvent. BrFt, for instance, is a cation formed by dissociation of and characteristic Forty-two moles (10 kilograms) of neutron-irradiated to bromine trifluoride. Acid ansolvides, especially well uranium was introduced into a dissolver containing 420 50 suitable for the process of this invention are antimony moles (57.6 kilograms) of BrF3. The dissolver was oper pentafluoride, niobium pentafluoride and tin tetrafluoride; ated at 130° C. and the pressure rose as high as 3000. a quantity of about 5 mole percent in the mixture is opti mm. Hg during the dissolution. During the course of mal. the dissolution, 126 moles (4.79 kilograms) of fluorine In the following example a few runs are described gas, was bubbled through the dissolver liquid. Upon 55 which were carried out with such intermediate uranium completion of the dissolution of the neutron-irradiated ore materials. uranium a first distillation was made of the more vola tile products of the dissolution step. The distillate from : the first distillation comprised approximately 50 moles of EXAMPLE. I. BrF (8.75 kg.). 50 moles (17.6 kg.) of UF6, 50 moles 60 (6.85 kg.) of BrF3, and substantially all of the volatile Various ore products were heated overnight at 400° C. fission products although negligible amounts by Weight. to obtain materials of a uniform, low moisture content. A second cut was then taken from the dissolver by dis A mixture of bromine trifluoride and antimony fluoride, tillation, comprising 420 moles (57.6 kg.) of BrF3 and the latter present in the mixture in a concentration of 5 4 moles (1.4 kg.) of UF6. This was recycled for use 65 mole percent, was added to the ore material. Heating '' in subsequent dissolution cycles. The nonvolatile residues Was not necessary since the reaction with the bromine 8 from the dissolver, comprising insoluble fission product trifuoride is exothermic. The uranium hexafluoride fiuorides, approximately 7 grams, and PuF3, approxi formed was removed by distillation and the residue an mately 7 grams, were removed from the dissolver with 70 alysed for its uranium content. In the following Table an aqueous wash. The first distillate fraction taken from V the data and results of these runs are summarized. the dissolver was introduced into a light-fraction column For run No. 2 the two-step procedure was applied, the which was operated at atmospheric pressure and at a tem first step consisting of treatment with hydrogen fluoride perature below the triple point of UF6. Two distillation at 600 C. and the second step of treatment with the cuts were taken from this fractionation column. The 75. bromine trifluoride- mixture. 2,880,878 TABLE V

Composition, Percent Uretained in BrF3 con ore material sumption U-material Run Process Details after treatment expressed No. with BrF3- as cc.F. EIO U3O8 PbO SiO2 SO Misc. SbF5, percent (STP)|g. of orig. content U

1 Without preyious 0.07 419 Randore concentrate------70.7 ------2.65 2.90 1.14NO3-, 1.22 Fe, 2.80 hyrofluorina $9,10 Also, 2.82 2 After fluorination 0.0 138 3. with EIF at 600° Precipitate obtained as 25.58 33, 58 0.029 7.5 7.06 0.45W, 0.01 B, 2.9 Fe, 3 without previous 0.55 552 intermediate product 0.2MoC)3, 1.13 CaO. hydrofluorina during ore processing. tion. D0------35 21.1 0.02 5.84 29.07 0.23W, 0.0025 B, 1.3 Fe. 4 ----- do------0.8 767 This table shows that in all cases a good uranium 8. The process of claim 5 wherein the bromine and recovery was obtained and that by the prefluorination bromine monofluoride are volatilized as they are formed with hydrogen fluoride the process can be made more 20 by distillation prior to the volatilization of the uranium econotical since a snailer qilantity of the relatively ex hexafluoride. pensive bromine trifluoride is then required. 9. The process of claim 5 wherein aluminum fluoride In another instance a magnesium fluoride slag derived is added to the mixture as a carrier for the plutonium from the so-called bomb process, in which uranium tetra tetrafluoride formed. fluoride is reduced to the metal with magnesium, was re 25 10. A method of separating uranium from uranium-, acted with bromine trifluoride. The slag had been finely plutonium-, and fission-products-containing materials, disintegrated prior to fluorination. A yield of more comprising adding bromine trifluoride plus 10 mole per than 90% of the total uranium present in the slag was cent of bromine to said materials, adding chlorine tri obtained in the form of uranium hexafluoride. fluoride to the mixture thus obtained, slowly heating It is to be understood that the foregoing examples are 30 the mixture to a temperature of below 56° C. whereby merely illustrative of the present invention and are in fission product fluorides volatilize, raising the tempera no way to be construed as limitations thereon. It will ture to between 100 and 160° C. whereby uranium hexa be apparent to those skilled in the art that the general fluoride distills away from formed. procedure set out in the above description is susceptible 11. A method of recovering uranium from uranium of numerous modifications without departing from the containing material, comprising adding to the uranium spirit of the present invention. containing material bromine trifluoride and a substance This application is a continuation-in-part of our co Selected from the group consisting of bromine, antimony pending application Serial No. 358,984, filed on June pentafluoride, niobium pentafluoride, tin tetrafluoride, 1, 1953, now abandoned. and mixtures thereof whereby uranium hexafluoride is What is claimed is: formed. 1. A method of recovering uranium from uranium 12. The method of dissolving uranium which com containing material, comprising adding bromine trifluo prises adding to a bromine trifluoride solvent a member ride to said material, adding a substance selected from of the group consisting of bromine, antimony penta the group consisting of bromine, antimony pentafluoride, fluoride, niobium pentafluoride, tin tetrafluoride and mix niobium pentafluoride and tin tetrafluoride, heating the i 5 tures thereof, and treating uranium with the resultant mixture thus obtained to a temperature of from 100 to solution. 160° C. whereby uranium hexafluoride, bromine and 13. The method of dissolving uranium which com bromine monofluoride are formed and volatilized, and prises adding bromine to bromine trifluoride in quantity condensing the uranium hexafluoride. Sufficient to provide a mixture of bromine trifluoride and 2. The method of claim 1 wherein uranium is present O approximately 10 mole percent bromine, and contacting in metallic form and the substance is bromine. uranium with the resultant mixture. 3. The process of claim 1 wherein the uranium-con 14. The method of dissolving a uranium mass contain taining material contains the uranium in a diluted form ing as a contaminant plutonium whereby not more than and the material is contacted with hydrogen fluoride, about 0.23 percent of volatile plutonium compounds are prior to the addition of bromine trifluoride, whereby 5 5 formed, which comprises treating said uranium mass uranium tetrafluoride is formed. with bromine trifluoride while continuously eliminating 4. A method of separating uranium from plutonium the volatile reaction side products comprising bromine present in a uranium-plutonium-containing aggregate, and the lower bromine fluorides from the reaction zone. comprising adding bromine trifluoride to said aggregate, 15. The process of claim 14 wherein the reaction is furthernore adding a substance selected from the group 60 carried out at a temperature of 100-160° C. consisting of bromine, antimony pentafluoride, niobium 16. The process of claim 14 wherein the reaction is pentafluoride and tin tetrafluoride to said aggregate, carried out at a temperature of approximately 130° C. heating the mixture thus obtained to a temperature of 17. The process of claim 14 wherein the reaction side from 100 to 160° C. whereby uranium hexafluoride, bro products are eliminated from the reaction zone by re mine, and bromine monofluoride are formed and vola 65 acting said side products with fluorine. tilized away from plutonium tetrafluoride formed, and 18. The process of claim 14 wherein the side products condensing the uranium hexafluoride. are eliminated from the reaction zone by distillation of 5. The process of claim 4 wherein said substance is said side products. bromine and wherein it is present in an amount of about 19. The process of claim 14 wherein the side products 10 mole percent of the bromine trifluoride. 70 are eliminated from the reaction zone by sparging the 6. The process of claim 4 wherein the temperature reaction mixture with an inert gas. is approximately 130° C. 20. The method of recovering substantially decontam 7. The process of claim 5 wherein fluorine is added to inated uranium from neutron-irradiated uranium which the mixture and the bromine and bromine monofluoride, cCmprises dissolving said uranium in a bromine trifluoride as they are formed, are converted to bromine trifluoride. 75 Solvent while passing fluorine through said solvent where 2,880,878 13 14 by uranium hexafluoride, non-volatile plutonium fluoride, stituents of the reaction mixture more volatile than bro fission product fluorides, and bromine pentafluoride are nine trifluoride and a substantial portion of the bromine formed, distilling the uranium hexafluoride, fluorine, bro trifluoride from the reaction mixture thus separating the mine trifluoride, bromine pentafluoride and fission prod volatile uranium hexafluoride from the nonvolatile plu luct fluorides more volatile than bromine trifluoride from tonium compounds, condensing said distiilate, distilling the non-volatile plutonium fluoride and less volatile fis said condensate at a temperature and pressure just below sion product fluorides, condensing said distillate, then that at which uranium hexafluoride is distilled whereby distilling said condensate at a temperature below the dis the fission product fluorides more volatile than uranium tillation temperature of uranium hexafluoride whereby hexafluoride are separated from the residue, and then dis the fission product fluorides more volatile than uranium tilling and separately collecting the uranium hexafluoride hexafluoride are separated from a residue comprising a from the residue. LIranium hexafluoride dissolved in bromine trifluoride, 23. The process of claim 22 wherein the volatile bro and then distilling the uranium hexafluoride from said mine and bromine monofluoride removed from the re residue and separately collecting the uranium hexafluoride action zone are regenerated to bromine trifluoride with thus distilled. 5. chlorine trifluoride. 21. The process of claim 20 wherein aluminum tri 24. The process of claim 22 wherein the bromine and fluoride is present in the reaction zone during the dis bromine monofluoride removed from the reaction zone solution of the neutron-irradiated uranium to provide an are regenerated to bromine trifluoride with fluorine. inert carrier for the non-volatile plutonium fluoride 25. The process of claim 22 wherein the bromine and formed. 20 bromine monofluoride removed from the reaction zone 22. The process of recovering uranium substantially are regenerated to bromine trifluoride with bromine pen free of fission products and plutonium from a mixture of tafluoride. uranium, fission products and plutonium which comprises dissolving said mixture in a bromine trifluoride solvent References Cited in the file of this patent at a temperature of approximately 130 C. while continu 25 Emeleus: journal Chemical Society (London), part I, ously removing from the reaction zone the bromine and 1950, pages 164-168. bromine monofluoride formed, then distilling all con