[1]United States Patent Office 3@275,422 3,275,422 CONTINUOUS-GAS-PHASE VOLATILITY PROCESS George 1. Cathers, Knoxville, and Jmnes C. Miilen, Oak Ridge, Tenn., assignors to the United States of America as represented by the United States Atoniic Energy Commission No Drawing. Filed Aug. 14,1964, Ser. No. 390,278 11 Claims. (Cl. 23-325) The present invention relates to methods of processing reactor fuels and more particularly to improved volatility processes. Fused-salt fluoride volati@lity processes have been investigated for processing both heterogeneous and homogeneous irradiated reactor fuels. In the @case of heterogeneous fuels, as for example zirconium-clad uranium fuel elen-ients, the fuel element is dissolved with anhydrous hydrogen fluoride in a molten fluoride sa-It mixture, such as equimolar NaF-ZrF4 or NaF-LiFZrF4, at an elevated temperature of about 650' C., and the zirconium and uranium are thereby converted to their respective tetrafluorides, both of which are soluble in the fluoride salt. After dissolution the uranium is decontaminated from fission products by further oxidation of the uranium tetrafluoride to the volatile hexafluoride state by contact with elemental fluorine at 500' C. Further decontamination of the uranium hexafluoride product from trace fission products is accomplished by an absorptiondesorption cycle on sodium fluoride pellets at 100' C. and 400' C., with the purified uranium hexafluoride being collected in cold traps. For the homogeneous fuels, as for example LiF-BeF2-ZrF4 salt solvent containing minor portions of UF4, this same process may be employed except the hydrofluorination step. While the basic fluoride volatility process affords excellent nonaqueous processing of irradiated reactor fuels to recover the therein contained nuclear fuels, it is not without its drawbacks. Probably, the most serious hinderance to an otherwise highly effective process is the corrosion problem. As mentioned above, the fluoride salt mixture is maintained in a molten state within a suitable container while hydrogen fluoride gas is bubbled therethrough to dissolve the zirconium uranium alloy fuel elements. While these salts are not intrinsically corrosive, by the addition of hydrogen fluoride or F2 to the system at elevated temperatures, corrosive attack on the containment vessel becomes quite aproblem. This is especially true in batch-type operations. There the altemate contacting of the column walls by the molten salt and the flliorine at the liquid-gas interface caused by bubbling F2 through the melt results in severe corrosion of the column walls. Among the common structural metals, nickel and/or high-nickel alloys, i.e., Inconel, INOR-8, have probably been the most widely investigated and the high-n-ckel alloys, such as INOR-8, with their we@ll-known oxidation resistance and good mechanical properties at elevated temperatures, appear to be the most promising. However, even these metals undergo extensive corrosion when employed as the container for such molten salt processes. With such difficulties experienced with conventional structural materials, attention has recently been directed toward the refractory metals, such as tungsten, as -possible candidates for container materials. However, it is apparent that while such metals possibly experience less corrosive attack they are considerably more expensive than the conventional structural materials. In addition to the corrosive attack during the dissolution process, there are additional corrosion problems during the fluorination step,. In the past, one method of overcomin.a these probnted Sept. 27, 1966 2 lems has been to transfer the salt melt contain;ng the soluble uranium tetrafluoride to another vessel to carry out the fluorine sparging. For this nickel has been found to be a suitable structural material. However, certain problems attend manua-I transfer of the salt melt between successive steps of the @process. One prior art method attempted to alleviate the corrosion problems of such molten salt mixtures by dispersing the molten salt into droplets by passing the salt 10 through a spray nozzle and concurrently contacting the droplets with fluorine gas as they solidified and fell through an unheated tower. While this process aflorded some improvements over the basic volatility process, it fell far short of providing an operable process wherein 15 the @conversion of the uranium tetrafluoride was accomplished in a single pass and which was amenable to providi,ng a continuous process. Rather, it was found that the percent removal of uranium was so low that a multip-licity of spray towers would be required to avoid 20 an impractically high single-spray tower. Hence, the fluoride salt would have to be recyc@led through as many as four batch stages to achieve the uranium recoveries attained in the basic volatility process, i.e., better than 99%, in a single batch operation. 25 It is, therefore, a primary object of the present invention to provide an improved volatility process for treating reactor fuels. Another object is to provide an improved volatility process wherein both heterogeneous and homo,-eneous 30 irradiated reactor fuels may be processed. Still another object is to provide improved continuous gasphase volatility process for processing both heterogeneous and homogeneous irradiated reactor fuels. A further object is to provide an improved method 35 f-or recovering uranium and plutonium values from molten salts containing the same. Still a further object is to provide an improved fluoride volatility process wherein the corrosive attack on the container vessel is significantly lower than prior art meth40 ods. Another object is to provide a process which is especially adaptable for the efficient recovery of plutonium values from molten fluoride salts. Other objects and advantages of the present invention 45 will be apparent as the description proceeds. In accordance with the present invention, there is provided an improved method for the removal of neutronirradialed nuclear fuels from a fused salt mixture wherein said salt mixture is heated to a molten state, dispersed 50 into salt droplets and contacted with fluorine gas to convert said fuel values to the volatile hexafluoride state and thereby volatilize same, comprisin.- the steps of contacting said salt droplets with gaseous fluorine at a 55 temperature at least as great as the liquidus temperature of said salt mixture to thereby convert said fuel values to the volatile hexafluoride state and thereafter recovering said volatilized hexafluoride product. With the present process applicants have been able to 60 eflect b.etter than 99.9% ren-ioval of uranium values from an equim@olar NaF-ZrF4 salt mixture containing from 2.5 mole percent to 9 mole percent UF4 in a single 4 ft. long fluorinator column with relatively low corrosion of the nickel fluorinator as comp;ared to prior art processes. The present process is applicable to any,of the salt sol65 vents useful in volatility processes, as for example any of the alkali metal fluorides. Typical examples of such solvents include NaF-LiF, LiF-BeF2, NaF-ZrF4, and NaF-LiF-ZrF4- Of these equimolar NaF-ZrF4 or 70 NaF--LiF-ZrF4 salt mixtures have been successfully employed in the dissolution of heterogeneous irradiated reactor fuel elements, such as zirconium-uranium alloy ele-
[2]'-71 ments, and similarly KF-ZrF4 salt mixtures have recently been devised for the dissolution of aluminum-containing nuclear fuels. On the other hand, Li7F-BeF2-ZrF4 salt mixtures have been proposed as a solvent for a homogeneous reactor fuel. It is essential to the successful practice of the present invention to maintain the temperature of the fluorinator column at a temperature at least as high as the liquidus temperature of the salt solvent. In one prior art method a study was made as to the effect of increasing -the temperature at which the fluorination was achieved up to a point just below the liquidtis temperature of the salt on recovery of the fuel values. While it was concluded that as the temperature went up the percent removal of dissolved fuel values increase, it was found that at the same time the height of the column necessary to accomplish such a conversion becameinordina-tely large, so large in fact that for all practical purposes the process wasinoperable. Moreover, it was concltided that it would be highly deleterious to such a process to exceed the liquids temperature @of the salt due to the severe corrosion problem attendant with rendering the fused salt in a molten state throu.@hout the fluorination opera-tion. Applicants' have unexpectedly found that, contrary to the suggestions in this prior art, as the temperature exeeded the liquids temperature of the salt, the column height required for virtually complete fluorination of the therein contained reactor fuels -to the hexavalent state, instead of continuing to rise, dropped,off markedly to a very low height, in the ran.-e of from 2-4 feet. Furthermore, the corrosion of the contactor at these hi,-h temperatures was also unexpectedly low. While the mechanism by which the successful results are obtained in applicants' process is not completely understood, it is believed ascribable to the maintenance of the salt mixture in a molten state throughou-t the fluorination operation. This becomes especially convincing when, in contradistinction to the prior art assumption tha-t the conversion of the fuel values to the volatile hexafluoride state involved a surface reaction between the fluorine and the UF4, applicants have found that the conversion does not involve a si-irface reaction but rather that the fluorine enters @the drop before reaction occurs. This is substantiated by -the finding that, upon dropping a smah amount of salt mixture into the column, gas surges were observed immediately thereafter, indicating that the fluorine had been taken up without a balancing UF6 evolution. It may thus be seen that in such a process wherein the molten salt mixture undergoes solidifica-tion almost immediately after it enters the fluorination section, the resultinrecovery efficiency wiH be extremely low due to the formation of an outer crust in the m-olten drops as the drop pro.-ressively is cooled, thereby precluding or greatly retarding the diffusi-on of the fluorine into the respective drops and conjointly the diffusion -of converted UFc, out of the respective drops. In such prior art methods wherein the fluorinator column was maintained at a temperature below the liquidus point of the salt, solidification of the molten drops occured, thus greatly diminishin@ the recovery efficiency of the process. MoTeover, in the case of uranium values and probably other fuel also, this may be compounded by the fact that the mechanism by which UF4 is converted to UFf, by contact with fluorine gas is not a simple reaction of dissolved flu@orine reacting with UF4 with subseqiient evolution of UF6. Applicants have found that there possibly is -an interaction between the c>xidation states and the existence of several intermediate oxidation states (between +4 and +6). For this reason the diffusion is not simply of the species UF4 and F2, but involves interaction of the various oxida-tion state species -and carrying of the fluorine by uranium. This last facet is seen to effectively increase the solubility of fluorine, which is normally quite low, in the salt melt. Hence, it may be seen that, where -the molten salt droplets are permitted to solidify, forming an initial crust along the 3,275,422 4 outer surface of the respective drops, the increase in fluorine solubility by uranium carrying of the fluorine is greatly diminished due to such initial crust formation and thus significantly decreases the recovery efficiency. 5 In carrying out the practice of this invention, applicants have found various operating parameters which are preferred. As a preliminary step to the fluorination, the column is purged of any,air present. This may be done with any gas which do.-s not react with fluorine, such as 10 helium and, of course, it may be accomplished by flushing the column with fluorine gas itself prior to actual fluorination. In this respect helium may be introduced countercurrently to the fluorine fiow and serve as a blanket gas for the fluorinator column. During the fluorine flush 15 the column is brought up to the operating temperature. It will be apparent that the operating temperature of the fluorinator column may vary for the respective salt solvents employed. As previously mentioned it has been found that the fluorinator column must be maintained at 20 a temperature at least as great as,the liquidus temperattire of the salt and preferrably at a high temperature than the liquidus temperature of the salt. For example, where an equimolar NaF-ZrF4 salt (liquidus -temperature 510' C.) containing 2.5 mole p--rcent UF. is used it is preferred that 25 the iluorinator column be mai:ntained at a temperattire within the range of from 570'-650' C., the higher the better. Di-ie to th-- severity of corrosion of the fluorinator column at elevated temperatures (especially above 700' C.) and other deleterious effects, as for example high 30 vapor pressure of the salt constituents at such elevated temperatures applicants prefer that the temperature to which the fltiorinator collin-in is maintained durin.fluorination not exceed 700' C. The gaS flOW Tates of the fluorine and the belium (if 35 used) may be varied over a wide range. While large fluorine gas flow rates may be desired for certain purposes (as will hereinafter be explained in greater detail), the requirement of excessively large fluorine traps to recover the volatilzed fuel values, as well as the possibilities of 40 large-scale leaks and high entrainment losses, probably outweight a@iy advantages achieved thereby. Hence, fluorine gas flow rates of between the range of 100-200 ml./ min. have been found to be quite suitable for laboratory scale operations using a 3" column (2.7" I.D.). Similar45 ly, helium flow rates within the same range have been quite suitable. It is preferred that the fluorine gas be introduced countercurrently to the flow of molten salt droplets and in the case of a vertical fluorinator column it is preferred that the fluorine gas be introduced at the 50 bottom of the contactor. After the fluorinator colunin is purg,-d and brought up to temperature, the salt solvent is introduced into the column in dispersed droplet form, as for example by passing the molten salt through a spray nozzle. It will 55 be apparent that other conventional methods may be employed to effect dispersion of the molten salt into the column. For example, the fused salt may be crushed to a partciular particle size and dropped through a preheater section disposed adjacent to and integral with the 60 fluorinator section to convert the solid salt to a molten state immediately prior to entering the fluorinator seetion. Another embodiment may consist of heating the flsed salt to a molten state andthereafter passing the molten salt through a seive plate which has openings 65 that have been designed to provide a certai-@i droplet size. Where, as for example, a spray nozzle is employed care must be taken to insure that the salt droplets do not come in contact with the column walls. Hence, it may be seen that the droplet size should be as large 70 as possible to preclude contact with the column walls, as would ocetir if the drc>plets were on the order of a fine mist. In this respect molten salt droplets of less than 50 microns have been found to have a high rate of incidence with the contactor walls and accordingly 75 are not preferred. Particles within ihe ran.-c of from
[3]5 100-200 microns have little or no lateral movement during descent and in the case of a six foot contactor have freefall times of between 1.5-3.0 seconds. It will be apparent that the particle size, column diameter and height, fluorination temperatures, iand freefaff time may be vaiied to effect a particular result. In this respect, it may be seen that particles above 200 micron@s might be utilized but would require a longer column and/or a higher fluorination temperature (to insure that essentially all of the uranium was volatilized during descent). Moreover, it has been found that better than 99.9% uranium may be recovered from molten salt droplets of a particle size of about 200 microns and a fluorination temperature of about 700' C. Inasmuch as a practical upper fluorination temper,,iture has been found to be about 700' C.' it is, accordingly, preferred that the molten salt particles be within the range of from 100-200 microns. Furtherniore, it may be seen that it is generally desirable to keep the time of fall of the particles through the fluorinator section as short;as possible consistent with complete reaction. To illustrate, whereas particles less than 50 microns require 15 seconds to traverse a six foot column, particles within the range of 100-200 microns require only between 1.5 and 3.0 seconds to fall the same distance. As an additional precaution the spray nozzle should be designed to insure essentially no impin.-ment of the molten salt droplets upon the contactor wal@l, and thereby greatly reduce the corrosion of the contactor. The particular design of the fluorinator column is not critical. It will, however, be recognized that the column should be of s-ufficient length to provide, for a selected particle size range, maximum conversion of the fuel values. On a laboratory scale column heights of 2-6 feet have been found to be quite suitable. In this respect, it should be noted that @as the particle size of the salt solvent increases the column height will likewise increase. As a special point, where a preheater section is employed, a hei,@ht of ab,out 26" and a temperature of about 650. C. have been found to be quite sufficient to convert the fused salt droplets (100-200 microns) to a molten state prior to ingress into the fluorinator section. Any conventional heating means may be employed to maintain the fluorinator column at a temperature above the liquidus point @of the particular salt solvent employed. It will be appreciated, howe-ver, that, where countercurrent flow is used and a chilled collection pool is employed, special attention must be directed to providing suitable heatina means to partially offset those end effects, i.e., the cool end acting as a heat sink and gas streams entering both ends of the column. In any respect, it is important that whatever heating means is selected it be capable,of maintaining a,constant temperature within the fluorinator col-umn during operation. After the molten salt droplets have passed through the fluorinator section they are allowed to solidify and are collected in the bottom -of the column. UF6 will sorb on the solidified salt droplets, -and it has been found that in order to achieve high uranium recovery, the fluorinated salt droplets must be protected from UF6 sorption. Applicants have found that this may conveniently be achieved by providing -a chilled (O' C. or less) pool of a fluorocarbc)n compound,.such as perfluoro-1,3- dimethylcyclohexane (C8F,6), for the droplets to fall into. Other methods may equally be suitable such as providing an inert gas blanket or as mentioned hereinbefore providin.a sufficient countercurrent flow of fl-uorine gas to sweep the volatilized UF6 out -of the fluorinator @and bence preclude any UFG from contacting the solidified salt droplets. While the present invention has generaliy been directed to fluorination of uranium values from molten fluoride salts, it will be appreciated by those skilled in the art ,that it is equally applicable -to -other reactor fuels such as plutonium. As shown in the basic fluoride volatility process of spar-ging reactor fuels such as plutonium from 3,275,422 6 molten fluoride pools, an equilibrium condition exists wherein large amounts of fluorine are necessary to drive the equilibrium toward PuF6. Inasmuch as in the present process the ratio of fluorine volume to salt volume is very high, it may readily be seen that applicants' process may afford a highly efficient, non-corrosive method for recoverin.- plutonium values from molten fltioride salts. Of significance is the fart that, wh-.re both uranium and plutonium values are present in a given salt, the uranium 10 is almost @completely volatilized before the plutonium starts to be removed; hence, applicants' process might ideally be employed to not only volatilize valuable reactor fuel values from molten fluoride salts but also may provide other beneficial results in providing a convenient 15 manner in which such fuels may be separated from each other. Further illustration of the quantitative aspects and procedures of the present invention is provided in the fojiowing examples. Examples I-VII describe the basic pro20 cedure and technique used in carrying out a falling drop fluorination of NaF-ZrFIUF4 salt mixture utilizing 28", 44" and 56" fluorinator columns, and Example VIII demonstrates the applicability of the prese-nt invention to a quaternary salt NaFZrF4@-LiF-UF4- 25 EYAMPLE I A ternary alkali salt mixture having a composition of 48.75-48.75-2.5 NaF-ZrF4- UF4 (mole percent) was ground and sieved into various I>article size ranges. The 30 original uranitim concentration of the fused salt was determined by fluorometric analysis and the liquids temperature of the salt mixture was 510' C. A vertical, nickel fluorinator column (2.7" I.D.), consisting of a 42" preheater section and a 28" fluorination section was fitted 35 with a powder feeder at the top end and a collecting container at the bottom end and provided with five electrically heatp-d resistance furnaces with separate variac coiitrols. A helium gas source was connected to the top of the coltunn and a fluorine -gas source -to the bottom. Prelim40 inary to the actual fluorination, the entire column was flushed with helium for one bour and then the fluorination section was flushed with fluorine with an equal amount,of helium flowing through the preheater section. The flow rates of the fluorine and helium gases wcre 200 mls./min. respectively. 45 After the column was flushed with the process gases, it was brought up to operating temperatures and runs were made at 570' C. and 647' C. A five-gram sample of the respective particle size ranges was placed in the powder feeder and fed into first the preheater section, 50 which was maintained at a temperature of about 650' C., to convert the fused salt mixture into molten droplets. Then the molten droplets passed through the fluorination section of the colun-in converting the UF4 to UF6 with the 55 volatile UF6 product being carried out of the column by the fluorine gas stream. After passing through the fluorination section the solidified salt droplets were collected in the bottom -of the column in a stainlesssteel collection cup containing liquid perfluoro - 1,3 - dimethyleyclohexane (C8Flc,) which was maintained at about O' C. The solidi60 fied molten salt droplets were subsequently analyzed for uranium concentration by fluorometric -analysis. The results are shown in Table I below. Table I.-Falling drop fluorination 65 Tempera- Size range, Initial U Final U Percent U Run ture,' C. micr ons conc ., cone ., reco vered P.P. M. P.P.I n. - 1 ---- ---- 570 > 149 46,8 00 5,73 0 87.8 2 --- ----- 570 125- 149 46,8 00 3,02 0 93.6 70 3 --- ----- 570 105- 125 46,8 00 490 08.9 6 4 --- ----- 570 88- 105 46,8 00 220 99.5 5 ---- ---- 570 63- 88 46,8 00 230 99.5 6 --- ----- 647 > 177 38,2 00 429 98.9 7 ---- ---- 647 149- 177 38,2 00 183 99.5 8 --- ----- 647 125- 149 38,2 00 73 99.8 75 9 --- ----- 647 105- 125 38,2 00 64 99.8
[4]7 EXAMPLE II A falling drop fluorination of the ternary alkali salt mixture 45.5-45.5-9 NaF-ZrFI-UF4 (mole percent) was carried out in the apparati-is employed in Example I and the same analytical technique was used to determine the percent uranium recovery. The fluorinatioii temperatures were 574' C. and 660' C., respectively, and the liquidus temperature of the salt mixture was 550' C. The results are shown in Table II below. Table II Tempera- Size range, Initial U Final U Percent U Run ture,' C. microns cone., cone., recovered P.P.131. P.P.M. -- 1 -------- 574 > 177 210,000 10,700 94.9 2 -------- 574 149- 177 210,000 7,800 96.3 3 -------- 574 125- 149 210,000 8,300 06.0 4 -------- 574 105-- 125 210,000 2,100 99.0 5 -------- 574 88-105 210,000 800 99.6 6 -------- 574 <88 210,000 700 99.7 7 -------- 660 177-210 194,000 997 99.5 8 -------- 660 149-177 194,000 688 99.7 9 -------- 660 125-149 194,000 379 99.8 10 ------- 660 105--125 194,000 243 99.9 11 ------- 660 <105 194,000 206 99.9 E)CAMPLE III A falling drop fluorination of the ternary alkali salt mixture 48.75-48.75-2.5 NaF-ZrF47- UF4 (mole percent) was carried out usin.@ a 26" preheater section and a 44" fluorination section in the same manner as employed in Example I. The fluorination temperatures were 559' C. and 638' C., respectively. The results are shown in Table III below. Table III Tempera- Size range, Initial U Final U Percent U Run ture, C. microiis cone., cone., recovered P.P.M. P.P-M1 -------- 559 125-149 54,400 1,724 97.0 2 -------- 559 105-125 54,000 419 99.4 3 -------- 559 88-105 54,000 212 99.5 4 -------- 559 63-88 54,000 202 99.6 5 -------- 638 177-210 51,600 260 99.2 6 -------- 638 149-177 51,600 126 99.5 7 -------- 638 125-149 51,600 75 99.7 EXAMPLE IV A falling drop fluorination of the temary alkali salt mixture 48-48-4 NaF-ZrFr-UF4 (mole percent) w@as carried out in the same manner as and in the same apparatus employed in Example III. The liquidus temperature of the salt mixture was 515' C. The results are shown in Table IV below. Table IV Tempera- Size range, Initial U Final U Percent U Rui:i ture,' C. microns cone., conc., recovered P-P.M. P-P-M. 1 -------- 556 > 149 83,900 590 99.3 2 -------- 556 125- 149 83,900 2,190 974 3 -------- 556 105-125 83,900 590 99:3 4 -------- 556 88-105 83,900 290 997 5.... 556 63-88 83,900 190 99: 8 6 --------........................... 560 177- 210 84,000 4,500 94.6 7 --------........................... 560 149- 177 84,000 6,980 91.7 8 --------........................... 560 125- 149 84000 1,650 98.0 9 --------........................... 636 125- 149 84:800 414 99.94 10 ------- 636 105-125 84,800 1-9 99.99 11 ------- 636 88-105 84,800 9.7 99.99 12 ------- 636 63-88 84800 10.3 99.99 13 ------- 636 > 177 87:100 49 99.5 14 ------- 636 149-177 87 too 3 9Q.8 15 ------- 636 125-149 87:100 3 99.99 16 ------- 636 109@-125 87,100 1 99.99 EXAMPLE V A falling drop fluorination of the ternary alkali salt n-lixture 45.5-45.5-9 NaF-ZrFI-UF4 (mole percent) was 3,275,422 paratus employed in Example 111. The results are shown in Table V below. Table V Temi@lera- Size range, liaitial U Fin,,il U Percent U Run ture, C. inicrolis cone., cone., recovered P.P.M. P.P.M . 1 -------- 556 149- 177 170,000 21,900 87.1 2 -------- 556 125- 149 170,000 9,700 94.3 3 -------- 556 105- 125 170,000 2,700 98.4 10 4 -------- 556 88- 105 170,000 1,700 99.0 5 -------- 556 <88 170,000 1,800 98.9 6 -------- 640 149- 177 186,000 162 99.91 7 -------- 640 125- 149 186,000 65 99.97 8 -------- 640 105- 125 186,000 70 99.96 15 EXAMPLE VI A falling drop fltiorination of the temary alkali salt mixture 48-48-4 NaF-ZrF4:-UF4 (mole percent) was carried out in the same manner as employed in Example 20 I, using a 14" preheater section and a 56" fluorination section. The fluorination temperatures were 572' C. and 622' C., respectively. The results are shown in Table VI below. Table VI 25 Tem%era- Sizo range, Initial U Final U Percont U Run turo, C. inicroiis cone., colic., recovered P.P.M - P.P.M1 -------- 572 >210 83,700 3,740 95.5 30 2 -------- 572 177- 210 83,700 2,160 97.4 3 -------- 572 149- 177 83,700 680 99.2 4 -------- 572 125- 149 83,700 220 99.7 5 -------- 1 62" > 149 77,100 1,770 99.7 -149 77 6 6 125 1100 229 99.7 7 -------- 622 105- 125 77,100 82 99.9 8 -------- 622 88- 105 77,100 87 09.9 9 -------- 622 63- 88 77,100 54 99.9 35 10 ------- 622 53- 63 77,100 341 99.6 EXAMPLE VII A falfing drop fluorination of the temary alkali salt 40 mixture 48-48-4 NaF-ZrF4:-UF@ (mole percent) was carried oiit in the same manner as in Example VI. with the exception that the solidified droplets were not collected in a liquid fluorocar-bon pool but rather were exposed to the process gases. The results are shown in Table 45 VII below and in comparison with the results shown in Example VI demonstrate the necessity to protect the fluorinated salt droplets from UF6 sorption. Table Yll 50 Tempera- Size raiige, Iiiitial U Final U Percent U Run ture, ' C. microns cone., cone. , recovered p.p.ni. P.P.Ill. I -------- 560 > 177 87500 6,240 92.9 2 ------ 560 149-177 87:500 4,110 95.3 55 3 -------- 560 125-149 87,500 1,590 98.2 4 -------- 560 105-125 87,500 820 99.1 5 -------- 560 88-105 87,500 820 99.1 EXAMPLE VIII A fahing drop fluorination of a qtiaternary alkali salt Go mixture 31.66-31.66-31.66-5 NaF-Z@-1--4-LiF4-UF4 (MOIC percent) was carried out using a 42" preheater section a 28" fluorination section in the same manner as employed in Example 1. The liquidus temperature of the salt mixture was 460' C. The results a.-e shown in Table 65 VIII below. Table VIII Tempera- Size range, Initial U Fiii,,il U Percent U Run ture, I C. juicroiis colic., cone., recovered 70 P-p-la. P-P.MI -------- 563 > 149 124,000 4,800 96.1 2 -------- 563 125-149 124,000 366 99.7 3 -------- 563 105-125 124,000 122 99.9 4 -------- 563 88-105 124,000 52 99.96 5 -------- 563 63-88 124,000 37 99.97 carried out in the same manner as and in the same ap- 75
[5]9 It will be understood that while the present invention has been described herein by certain specific embodiments, it is not intended thereby to have the invention limited to the details given, inasmuch as many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof. W,ha,t is
