CA2224116A1 - Zirconium and hafnium separation in chloride solutions using continuous ion exchange chromatography - Google Patents

Abstract

A method and system for improved ion exchange chromatographic elemental separations of zirconium and hafnium elements and also, if desired, separations of the isotopes thereof from crude zirconium minerals by using improved crude aqueous zirconium (also containing hafnium) chloride feedstock solutions, aqueous chloride eluant solutions, cationic or anionic exchange resins, and reduced ion exchange chromatographic operating temperatures. The method and system of the invention provides improved crude aqueous zirconium chloride feedstock solutions by carbochlorinating zircon sand and hydrolyzing and dissolving the chlorination products under controlled conditions to substantially eliminate cross-polymerization of the carbochlorination products, which undesirably yield inseparable zirconium and hafnium co-polymers during hydrolysis, by inhibiting the hydrolysis exotherm and/or the free acid generation during hydrolysis.

Description

ZIRCONIUM AND HAFNIUM SEPARATION IN CHLORIpE SOLUTIONS USING
CONTINUOUS ION EXCHANGE CHROMATOGRAPHY
la; Meld of the Invention:
The inve~on generally relates to the field ei~I a~ isotopic separation processes, and more particularly relates to a method and system for corainuously.
partially or compleoelY, separating zirconium (Zr) and hafnium (Hf) etemeats from S cnrde zirconium minerals in order to provide clear grade zirconium metal and nuclear grade hafnium moat. The invention also relates to a method and system for contimiously, partially or completely, sepataring zirconiunn and hafnium isotopes from either crude zirconium mi~ral5 or from separated and purifiod solutions of zirconium and hafnium obtained from an elemental separation thereof in order to prov idc isotopically enriched clear grade zirconium metal and hafnamn meal.
Even more particularly, the invention relates to improved zirconium aril hafnium ~parsdon ud purification processes whereby zirooniutn and hafnium arc s?~rata~ in a single operation using continuous ion exchatge chmtn~-ttography by using chloride based sohrtiom having a reduced conceaaation of rclativcly iasrpatablc co-1S polymers of zirconium and hafnium as the feed phase, chloride based cluaat solntior~
as the mobile phase, and either cationic or anionic exchange rtsi~as as the stationer phase. Cbno~matographic proressing of zirconium in order to minimize its thermal nteutron c~aua cross-section through alteration of its naNtally occurting state enhanccv the utility of zirconium as a fiat rod cladding material for nuclear reactun C'hromstogtaphic processing of hafnium in order to ma~cimiu its thermal ncutn~n capocte cross-section through alteration of its naturally ocauring state enhances rhc utility of hafnium as a comroi rod material for nuclear reactors. 'The method and sysmnn of the invention accordingly irnpmves the stability of zirconium and hafnium as itmetaal materials of constivction for nuclear reactor:.
2. Hgolc~e~ou~ o a lm~eemivn:
s zirconium metal has historically been used primarily as an internal tnsrerial of coastrucci~on for nuclear reactors, for imtana) as claddings for uranium oxide nuclear foci rods. Cladding of nuclear fuel rods. the primary end) provides as outer merallic J~ Y ~8 ~ ~kar fuel clement which serves, inter ells) to prevent corrosion of the fissionable nuclear fuel and release of fission prodtxxs iron the coolant loop. Other attracxive applications for zirconium metal are in the fabrication of corrosion-resistant ch~emi~l process hardware and advanced ceramics as oxides.
Puticularly) materials for use in nuclear reactors are selected for their cbetma!
neutron capture crass-sections, along with other ptopatia. Zirconitua is selectfld in tmclear application for) among other properties) its tow average thermal neutron capriut cross-section (appmx. 0. I8 bats), good ductility, good r~ista~e to radiation damage, a~ excellent cortasioa resistance in pressurized hot water of umperawres up to about 350~C. The naturally occurring isotopic disuibution of zirconium bas a low average thermal aeuzmn capaFre cross-section which is desirable for vermin nuclear reauor materials. The naturally occurring isotopes of zirconium arc gives is Table t .
Ta_. bl~l Naauallv Ocautine Zirconium Iaotaoea Thermal Naraon Cz~s je crane Cross-Sacnn. Burn I10'" m'~
z.~ s F.ss o.03 Zs Zra' 1F.31 1.14 2r'~ 17a9 0.21 Zr" 1728 0.0S5 Zr" 2.76 0.020 Howsvcr) there bas beers a continuing ins in reducing the tendency of ~clcar grade zirconium to absorb thermal ncutrom do to its cortctmination by neutron opaque ha~nitnn. The more transparent the internal materials of construction of a nuclear nor are to these tbertnal neutror~) the more efflciendy the tluclear reactor will ftmction since a certain number of these thermal oa~anns are required to sustain the truaon ui~ggend fission reactions. Accordingly) it is desirsbk to redone the tbamal aaia~on capatre cross-section of the internal maoerials of construction of a ntrclar Tractor) such as zirconium.
F~riy efforts at reducing the thermal r~n~oa calmuz emss-section of zirconium were dirxted to separating zim~tdum from hafnium) which by the way are the most cliff curt elemems of the periodic table to separate. The two ekmencs, zirconium and ha~n) occur together naturally, but hafninmt has a sully Larger thermal t>etmon capuure cross-secxion (almost 600 times that of zin~ium). Naturally ocatrring crude zirconium minerals coruain typically about 1 to 5 ~ hafnium. Thus the separation of zirconium from hafnium allows for the production of nuclear grade zirconium with a lower average tZ~errnat neutron capture cross-section by the eUpoination of ha~ium.
Commercial prac~es curreruly available for the pt~uction of mielear grade zirconium are variations of solvent extraction processes wherein zircon sand is IS canvertod to zirconium oral as a result of a somewhat involved series of steps. This extraction prooass reqaires the use of organic solvents) usually luxotr or mahyl isobutyl icttone (MIBK), and various aqt:eous solutions) including thiocyaaic acid and hydtnchloric mid. Ha~ium, which is chemically similar to zirconium) must be separaaed from the zircoaaum. Solvent extraction requires a series of separate extraction steps along with separate separation columns. 'Ibe zirconium, organic solvent and thiocyanate recovered from the hafnium separation steps are usually subject to additional processing to make sure that as much zirconium is recovered from the ~~ ~ perk-The zirconium ultimately t~ecovered from most solvent extraction processes is ~S in the form of pure zirconium oxide (ZrO:). In tl~ commonly used tormomerrial gr~, the zirconium oxide is ttben chlorinared to form zirconium ceaachloride (Zst'1~, which is purif~d a~ then subjected to KroU r~On to produce zirconium metal suitable for tutciear applicatiotu_ 'the aqueous and organic liquids used in the ptvc~ typically include waste metals and other materials that must be properly discarded. O~ of the methods of treating these liquid wastes is to place them in holding ponds for fugue treatment and remediation. Eiowever) this is increasingly becoming an unacceptable waste management solution, particularly since federal and state laws relating to land ban chcmic~ls and waste disposal have booome more stringent.
The solvent extraction proccsscs effectively separate zirconium from hafnium to produce zirconium of the quality required for use in nuclear reactors and elsewhere in the nuclear industry. However, the increasing concern exprcssed by the public, the scientific community and the regularity agencies regarding the waste generated by solvent extraction proccsses has lead the nuclear industry to explore altennativc zirconium production methods which do not present the same waste management IO concerns.
Other zirconium and hafnium separation processes in addition to the aforementioned solvent extraction prop have been proposed. An ion exchange process for separating zirconium and hafnium is described in U.S. Patent No.
2,546,953 to Street. In U.S. Patent No. 2,546,953, Street discloses an ion exchange I S separation process wherein mixed oxy-chlorides of zirconium and hafnium are passed through a cationic exchangc resin and then recovered with hydrochloric acid.
This processcs, however, fails to produce a highly pure zirconium and presents waste mana;ement concerns. In particular, this process genezates liquid waste which requires proper disposal.
20 Recent effort tv minimize organic wastes have proposed aqueous techniques for the separation of zirconium from hafnium and also for the potential separation of zirconium and hafnium isotopes therefrom by using continuous) steady-state, ion exchange chromatography in a continuous annular chromatograph (CAC) as taught in, for example, U.S. Pat. Nos. 5,023,061 (Snyder, et aL), 5,024,749 (Snyder, e_t al.), 25 5,Q98,676 (Lee, gt ate, 5,110,5b6 (Snyder, gl ~), 5, l12,493 (Snyder, et al _) ) and 5,174,971 {Snyder, el ~.
'These cited patents teach continuous methods and systems for simultaneously separating and purifying zirconium from hafnium andlor potentially simultaneously isolating the fairly abundant low thermal neutron capture cross-section isotopes of 30 zirconium and the high thermal neutron capture cross-section isotopes of hafnium in a single operation. While each of these teachings are technically feasible) optimization of the process for greater efficiency, lower waste generation, and lower costs cannot be adducal therefrom. What is needed is a method and system for chromatographically separating zit~conium from hafnium in 2c single operation using optimizod processing parameters which provide for commercially important operations.
Commercially acceptable zirconium and hafnium separations in a CAC using aqueous chloride based feodstock solutions (obtained from aqueous hydrolysis of the carboehlorination products of zircon sand), aqueous chloride based eluant solutions) and cationic or anionic exchange resins have proved to be elusive. Zirconium product purity of less than 50 ppm Hf in Zr, zirconium product concentrations of greater than 15 g!1 Zr, and product yields of about 909b have been unobtainable using conventional chloride based solutions in the CAC.
The conventional crude chloride feedstock solutions typically used to support continuous ion eacchange chromatographic Zr and Hf processes) as taubht in the above cited patents, are those obtained from dissolving halogenatea crude aircon, ice, zirconium tetrachloride (ZrCI~) and hafnium tetrachloride (I~fCI~) in aqueous solution at room temperature to produce a solution of zirconium ions and also some hafnium ions amenable to ion exchange chromatographic separation techniques. Crude zirconium which also contains about 1 to 5 96 hafnium is commercially obtained by chlorinating crude arson sand (ZrSiO,) in the presence of a carbon source, such as coke, at temperatures of about 1000~C and separating the reSUlting zirconium tetrachloride (ZrCiJ fraction (which also contains HfCI,) from the resulting silicon tetrachloride by a differential condenser. The zirconium fraction typically contains a natural distribution of zirconium isotopes in the form of zirconium tetrachloride and also contains hafnium tetrachloride. Both compounds are then readily hydrolyzed in aqueous solution at room temperature to yield crude zirconium oxychloride (ZrOG7~
and also hafnium oxychloride (HfOCI~ which) in turn, further dissolves or dissociate in aqueous solutions to yield crude feedstock solutions of zirconium and hafnium ions) g_g., ZrOz+ and HfOz' (canons)) or ZraCldZ' and HfOCI,'' (anions), eic. These aqueous ionic feedstock solutions are then suitable for use in an ion exchange chromatographic process for the separation of elemental zirconium from elemental hafnium and for the separation of zirconium isotopes therefrom to produce nuclear grade materials.
F~Ioweves, it is difficult to separate effectively and isolate nuclear grade zirconium from hafnium ) and also to effectively separate and selectively isolate the low neutron capture cross-section isotopes of zir~nium or the high neutron capture cross-section neutron isotopes of hafnium from a feedstock of ionic zirconium compounds and hafnium compounds obtained from aqueous hydrolysis of a mixture of crude ZrCis and HfCla. The aqueous hydrolysis reaction of crude ZrCI, and HfCl,, typically performed at ambient starting temperatures, which is used to form the conventional aqueous metal complexed chloride feedstock solutions to support a continuous, sieady-state, ion exchange chromatographic separation of zirconium from hafnium and/or separation of zirconium isotopes or hafnium isotopes, is a highly exothermic ruction.
Moreover, the hydrolysis exotherm tends to drive a cross-polymerization side reaction between the resultant ZrOCIZ and HfOCIz to form co-polymers thereof) which are hi ;hly undesirable. These cross-polymerization side reactions tend to form inseparable zirconium and hafnium co-polymer complexes. And, these inseparable zirconium and hafnium co-polymer complexes, once formed, impair the separation of the zirconium and hafnium, and the separation of isotopes thereof, which consequently diminishes the overall quality of the resultant nuclear grade zirconium and hafnium materials.
What is n~ded is an improved method and system for continuously separating and purifying, partially or completely, zirconium from hafnium) and also) if desired, for continuously and selectively, partially or completely, separating isotopes of zirconium arid hafnium, by using improved aqueous chloride-based feedstock solutions and eluant solutions, and improved operating conditions to support continuously operating, steady-state, ion exchange chromatographic separation techniques) while inhibiting the formation of inseparable zirconium and hafnium co-polymer complexes during aqueous feedstock preparation and also during chmmatographic processing of the feedstock solutions to improve the overall quality of the resultant nuclear grade zirconium and hafnium materials in terms of product concentrations, purifies) andlor yields, and while also eliminating organic reagents and Liquid waste discharges.

?-Accordingly, the present invention addresses design improvements in order to improve the overall Quality of the resultant nuclear grade materials in terms of: greater purifications, greater concentrations, greater yields, greater' efficiencies) simpler process designs, lower operating costs) tower waste generations, and others.
S 3. Summary of the Invention:
It is an object of the invention to provide an improved continuously operating, steady-state, ion exchange chromatoDraphic method and system for the separation and purification of crude zirconium into zirconium and hafnium fractions andlor into distinct isotope fractions thereof which yield improved separations of zirconium and ZO hafnium, and, consequently, yield improved nuclear quality zirconium and hafnium metals, while also reducing the waste generation and operating costs of prier methods and systems.
It is a further object of the invention to provide an improved method and system far the separation and purification of airconium from hafnium using continuous, steady-15 state, ion exchange, chromatographic separation techniques based on chloride solutions by using improved aqueous zirconium (also containing hafnium) chloride feedstock solutions as the feed phase and aqaeous chloride eluant solutions as the mobile phase, and separating the materixts on either cationic or anionic exchange resins as the stationary phase.
20 It is another object of the invention to provide an improved method for the preparation of crude aqueous ionic zirconium and hafnium chloride feedstack solutions for introduction into a continuously operating, steady-state, ion exchange chromatographic method and system to support the separation of crude zirconium into zirconium and hafnium fractions andlor into distinct isotope fractions therefrom which 25 yield improved concentrations, purifies and yields of nuclear grade zirconium and hafnium.
It is a feature of the invention to control the hydrolysis exvtherm andlor the free acid generation during the preparation of the crude aqueous ionic zirconium and hafnium chloride feedstock solutions which are ultimately fed into a continuously 30 operating, steady-state, ion exchange chromatographic separation column to eliminate the cross-polymerization reactions of zirconium and hafnium and to yield nuclear quality zirconium and hafnium. Otherwise inseparable zirconium and hafnium co-polymers and inordinate wastes will be formed. Iiistoricalty, aqueous ionic zirconium chloride feedstock preparation conditions have impaired the chromatographic separations of zirconium from hafnium.
In one aspect, the invention resides in an improved continuous method and system for separating and purifying zirconium from hafnium with a substantial reduction in the formation of zirconium and hafnium eo-polymers and a substantial improvement in the product concentrations, parities) and yields, which is characterized by: (A} preparing a crude aqueous chloride feedstock solution of zirconium and IO hafnium ions as the feed phase with a substantial elimination of cross-polymerization of zirconium and hafnium side reactions; (B) loading the feed phase of the aqueous chloride feedstock solution of zirconium and hafnium ions W a continuously operating, steady-state, ion exchange chromatographic column containing an ion exchange resin as the stationary phase, such as either cationic or anionic exchange resins;
(C) feeding an aqueous chloride eluant solution as the mobile phase, such as HCI) to the column to elute the feedstock solution from the ion exchange resin; and, (D) separately collecting a substantially pure zirconium fraction, a substantially pure hafnium fraction and at Ieast two waste fractions. The method and system can also further be characterized by: (E) separately processing the zirconium fraction and the hafnium fraction to produce nuclear quality zirconium and hafnium metal; (F) volume reducing the waste fractions for disposal; (G) recycling the eluant solution for reuse in step (C);
and, (H) optionally recycling a mixed zirconium and hafnium fraction for reuse in step (B). The method and system of the invention can also further be characterized by: (I) separately processing the separated and purified zirconium fraction and hafnium fraction of step (D) to produce isotopically enriched nuclear quality zirconium and hafnium.
It is preferred that the zirconium and hafnium separations are conducted in a continuous annular chromatograph (CAC) device which operates in a continuous and steady-state manner. It is also preferred that the zirconium and hafnium separations are carried out at a reduced temperature of about 0~C to 5~C to additionally improve the zirconium and hafnium separation kinetics.

_ g_ In another aspect) the invention resides in an improved method for the preparation of crude aqueous ionic zirconium and hafnium chloride feedstock solutions with the substantial elimination of inseparable zirconium and hafnium co-polymers which are used to support ion exchange chromatogxaphic processing. The improved feEdstock solutions can be prepared by at least three alternative methods, which are characterized by either: {A) (i) chlorinating zircon sand (ZrSiOJ in the presence of carbon, such as coke, at about 800~C to l200~C, to produce a crude zirconium tetrachloride (ZrCI~ fraction which also contains hafnium tetrachloride (HfCI,) fraction and a silicon tetrachloride (SiCI,) fraction; (ii) selectively isolating the ZrCI~/FifCI~
fraction from the SiCl4 fraction; (iii) partially hydrolyzing the crude ZrCI,/HfCI, fraction in water (HZO~ at a reduced temperature of about 10~C to 25 ~C to produce an anhydrous zirconium oxychloride (ZrOCI~ which also contains hafnium oxychloride (HfOCI~ fraction and a HCI fraction; {iv) selectively removing the HCl fraction for reuse; (iv) completely dissolving the ZrOCIzIHfOCh fraction in water or aqueous acid, such as HCI, to form the aqueous chloride feedstock solution of zirconium and hafnium ions; {8) (i) chlorinating zircon sand in the presence of carbon, such as coke, at about 800~C to 1200~C to produce a crude ZrCI,/HfCI, fraction and a SiCI< fraction;
('u) selectively isolating the 2rCI,IkIfC)~ fraction from the SiCI, fraction; and, {iii) hydrolyzing the crude ZrCI,IHfCiQ fraction with ice (H~O~), preferably in the form of crushed ice, at a temperature of about O~C to 10~C to form the feedstock solution of zirconium and hafnium ions; or, (C) (i) chlorinating zircon sand in the presence of carbon, such as coke, at about 800~C to 1200~C to produce a crude ZrCI,/HfC1<
fraction and a SiCIQ fraction; (ii) selectively isolating the ZzCI~IHfCI, fraction from the SiCl4 fraction; (iii) subliming the ZrCI,IHfCI, fraction at a temperature of about 200~C
to 450~C and a pressure of about S to 25 psi to form a ZrCI,IHfCl4 vapor fraction; (iv}
partially hydrolyzing the ZrCI,/HfCI, vapor fraction with steam (HZ04,,) to from a ZrQCIz/HfOCIz vapor fraction and an HCI vapor fraction; {v) removing the HCl vapor fraction for reuse; (vi) condensing the ZrOGh/HfOCIZ vapor fraction to an anhydrous ZrOCII/HfOCIz aqueous fraction; and, (vii) completely dissolving the ZrOCIi/HfOCIz fraction in water or aqueous acid ) such as HCI, to form the feedstock soiution of zirconium and hafnium ions.

- 1~ -4_ grief I~SCri~tion of th v~,in~.s:
There are shown is the drawings certain eztmplary embodiments of the invernion as presently p~efernd. It should be understood that the inveraioa is not limimd to the embodiments disclosed as exaaipks, and is capable of variation within the spirit and scope of the appe~ed claims. In the drawings, FIGURE 1 is a schematic flow diagram of the zirconium and hafnium separation me~Od a~ system of the invcntioa;
FIGURE 2 is a vertical sectional view of a cotrtinuotis annular clmomatograph device used in the zirconitun and hafnium separation rnechod and sy~em of the imrention; and) FIGURE 3 is a petsp<xtivc view of a continuous anzatiar chromatograph device with a portion in section to show the annular chromatographic separation column used is the zirconium and l~nm separation method and system of the invemion.

S.,~p~ of the Pczfrrred Embodiments of the inveation_~_ The invention provides both the procxssing method and sysuem for the contiaarous) steady-state) separation and purification of the elm zirconitua (Zr) and hafnium (Hf) from crude zirconium minerals containing hafnium impurities in a single procedure pc~efaably in a cotuinttous arumlar chmraatogtaph (CAC) device, which does nac substantially gena~ate inseparable complexes of zirooniaraz and hafnium as a by_ pox) and which also improves separation kinetics) and reduces amounts of waste generation. 'The resultant separated and purified zirconium and hafnium products from the and system of the invention can then be used as itucleat grade zirconium and hafnium materials of construction for nuclear reacoors. 'The rrsuIta~
separated and purified zireoni~mm a~ hafnium products can also be used, if desired) to support further separation processing into their i~ividual isotopes. either performed concurrently in the same procedtut or subsequently in another operation) to provide isotopically tmrclear grade zirt:oniuw a~ hafnium tnatcrials of consauction for nuclear 13 reacxota.
'ire earlier noentioned U.S. patenrs) namely U.S. Pat. Nos. 5.023.061:
5,024,T49; 5,09$,b76; S,110,566; 5.112.493: and) 5,174,9T1, teach technically fete txhniques and equipmatt for chromatographxatly separating zirconium from hafnium using a contim:aus annular chrotnatograph (CAC) in a single) continuous.
shady-srace) operation, all of these disclosures being incorporated by reference herein in theft entireties. 'Ihe primary focus of these refetns~s. however, was the cbrom~ooperation itself with only passing attention being paid to the fecdscock pcetu arid optimiTatlon techniques. Despite the technical and economic success of this art) the ci~romatographic separation ptnc~es for zirconium and hafnium separations require more derailed attention to fecdstock salutian p:rpararioas in order to achieve process opdmimcion, cost rrdrrctioa) waste ceduaroa and 5ystemat~c.
repro~eible and reliable operations for producing nuclear quality materials.
In these earlier efforts of chromatographic processing in a CAC, the invcntots ato use pure, as well as mixed. chloride-based systems by generally: t ~ ~
feeding aqueous crnde Zirconium chloride feedscoch solution of dissoivcd art!
dissociated ZxOCI= (which also contained HtnCt,) derivod from the aqueous hydtolycr.

of a cacbochlorination ptodtrct of crude zircon sand; (H) feeding chloride eluanc solutions of HCI or HC10,) as well as tan~hlotide ehraat sohrtions of HZSO,) H,P~O, or HNO~, to the CAC to elute the feedstxk solutions from the ion exchange rtsiu:
and) (C) recovering the separated anti purified zirconium and hafnium product fry S urd waste products ftvm the CAC for further processing into tbcir nspearve metals.
However. as described about) cttese prior methods were accompanied by the production of inseparable zirconium and hafnium co-polytaer complexes as by-products of the separation processes, which redtxed the ovetaE! quality of the resultant nuclear grade taaoerials. Once formed) tta~ inseparable complexes traded to contaminate the zitnoliium product wave front exiting the CAC which eot~queatly diminished the overall quality of the resultant nuclear grade material as well as its yield.
In fiu~r detail. the prior taethods for preparing the crude aqueous chloride ( feodsroclc solutions of xitt:otsittm and hafnium ions of step {A) which have been found t0 have drawbacks bnt which have been used to support coatirntous) steady-watt, ion excha~e chromatographic separations of zirconium from hafnium in a CAC weir by:
{i) halogtnaring, e~, chlorinating, crude zirconium minerals. for instance.
crude zircon (ZrSiOa, which typically contain a natural distribWtioa of zirconium isotopes and also 1 ro 5 ~ hafnium c~aminatioa as will as other transition metal and radiochemical imptuiries. ~ the pie of a carbon source) c_g" pttroletntn cokt, at tempcratturs of about 800~C t0 1200~, typically about 1000~ (Otherwise known as the carbochlorinatioa of crude zirconium minerals): (ii) separating the resultant crude zirrvnium r~eotachloride (ZrCla fraction which also coatxins hafnium oetrachlor~ide (HfCI,) fivat the tesni~c silicon tetrachloride fraction (SiCla) typically is a di$eteatisI coarser; (iii) partially 4ydrolyzmg with water the scparaoed ZrCI,IHfCI, fracxion by begi~izag at a starting solution temperature of about 25~C (but a:
the hydrolysis traction grvceeds, the hydrolysis reatxion exotherm drives tlx solution tempaanue up to about 100~C or greater along with the acid generation rate) chaeby causing cross-polymeriution side reictiorts) to yield an aqueous solution of zirzonium oxychlotide (ZrOCI,) which also cotatains hafnium oxythtoride (HfrDCI~ and excess frte acid hydrogen ions and HCl in Solution: (iv) separating the HCI by-product.
typically in an HCl absorber; and. t~) complctdy dissolving tire Za~OCI,IHPOCI.

friction in water of aqueous acid solution to yield the aque~s ionic c4loride feedstock solution. In the feedsZOCk solutions) a lower acid conoentracion tends to form zirconium canons, whereas a higher acid coition ocnds to form zirconium anions.
Alternatively) the crude Z.t~I,/HflCL could be dissolved directly in a single step, S hpa~ever, the ai~senx of HCl in the two-step process increases the solubility of zirconium in water, to allow the production of higher feedstocJc zirconium eoatioas. These converaional crude feaistock solutions am then injated into the ion exc)rangc column of the CAC with ehiaat solutions to support the separation and puriftcatian of zirconium from hafnium at room tetapecature.
Historically) therefore, in order to form the chloride f~dstock solutions of ionic carapovnds of crude zirconium which also conrains crude hafnium, the zirconium tsir'a~chioride and hafnium tetrachloride fraction from the carbochlvrination of tltt crude zirconium minerals are hydrolyzed starting at room tempemritre (approx. ZS
~C), but once the hydrolysis reaction begins) the hydrolysis exotbum drives the solution tempetat<tres up to about 100~C or greater along with the free acid (H') generation rate) to yield an aqucaus ionLC solution which also contains insrparable zirconium and ha~ium ca-polymers, and which corufy are lost for use as a feedstock for the separation process. The usable as well as the unusable co-Qolymrxized poztiotts of the fe~tock solutions are then cam~entionally feel typically at ro~rt tempcrantre (a~rox_ 25~C) to a continuous. s~Y-~. ion exchange chrornaiographic tohunn containing cationic or anionic ion exchange resins) preferably in a continuous annular chromatograph (CAC) also typically operating at room temperaDure (approx. 35 ~C>.
along with an acpteotts acid ehtanr solution for elunoo of the separated zirconium and hafnium fractions iron distinct product strtatns for isolation.
However, the inventors have discovcrai that by using these converuional methods) as gezxrahy taught in the earlier U. S. patents hertimbove. ttte separated ~clcar grade zirconium product fraction purity is marred by incomplete separation and irrluSion of hafnium with the zirconium which undesirably aloens the thermal neutron abs~bing properties of the nuclear grade zirconium. This has led the invetuors so study the faduock prtparaiion methods and chemical and thermodyttamie mechanisms therefore) sure the getrration of substantially pwe hafnium-free zirconium vs exu~e~y desirable for ulatnau use as a r>uclcar grade m:tetial or if desired for use as a fcodstock to support further zirconium isotope stparation.
The rnetbad and system of the invention provide fot the conthttuxrs, steady-state) ion exchange ci>rOmatogtaphic separation of zirconium froth hai;nitun and opdonaily isotopes thereof, in a CAC using pure chloride-bawd systems, while simultaneously intu'biting the production of irreparable zirconium and haf~ ~.
polymer complexes, therzby improving the quality of the resultant nuclear grade cnacerial. '1'11e improvements can be rraliud in one instance by controlling tire exotherm and free acid generation typically associaotd with the preparation of conventional cnrde zirconiuBt oxychloride (ZtOCir} also canuirting hafnium oxychlotide (HfOCI~ feedatock solutions. The improvemems can ae realized in another instance by rEdtrcing the chromatographic processing taaperatures.
These, in f tum, reduce or eliatinate the cross-polymerization side trxtioas of zirconium and The method and the systttn of the present imezf~ particularly rprovcs contitttu~us, steady-state, ion exchange chromatographic serration of (1.) elemental xinconium and hafnium and/or (2. ) isotepes thereof from the hydrolyzed crude carbochiorination prod of zircon or other zirconium minerals by using chloride chemistry for the separations) by improving the crude zirconium feednock solution pttpatattion conditions to inhibit the formation of zitconiurp and hafnium co-polymers during hydmiysis and also during chromatographic processing, a~ also by improving other chromatographic processing conditions to smprove the separation kinetics) which results overall in unproved separaciotu of zirconium and hafnium with reduced waste generation and reduced operatie~ costs over prior methods and systems. The ts'xthod and system of the inve~rion is preferably used to getxrate substsrztiahy hafnium-free nuclear grade zirrAnittm for nuclear applications znd alto used to generate dally hafnium-fife zirconium feedstocl6 to support zirconium isotope separation to generate strbstaatially hafnium-free isotopically enriched nuclear grlde zirconium.
In thueir studies) the inventors have discoverod that the aqueous hydrolysis reaetio~ of crude zirconium tetrachloride and also hafnium tetrachloride to yield a separable feedstock sohrtion of ions. gg. Zrfl'- and HFO'= (carious) or Z.rOCI,Z- a~

-IS-Hf OCI,=' unions), ctc. , are slow to come to equilibrium and prodtxe t) ice.
, a rise and fall in temperattuzr of the reactive system over tip reaction time.
As a consequence, some of the zirconium and hafnium compounds in aqueous sohttion are txvss-polymerized to yield inseparable iircotuum and hafnium complexes which ara not S amenable too ion exchange chroiaatogi~phic sepanaons. thereby resulting in incomplete acparation arnd hahnit>m contamination in the zirconium firactionaixd proddtbcc_ Moreovet, the inventors have discovered that in addition to the hydrolysis exa<berm.
the presetrce of ftre hydrogen ions (H') or free acids gexracai during the aqueous hydrolysis reactions lead to accelerate and catalyze the cross potymcriation of zirconium and hafnium and also tend to cause ptrmatme elution (or leakage) of the zitronium or hafnium fractions once loaded in the concitruous ~n exchange chrnmatograph column. The generation of free acid is also ittcreaxd as the exothcrm inr;teases the remperatutt: of the hydrolysis solution.
The hydrolysis reactions of tI~ crude zirconium and hafnium earbochlorination pzod~s to produce a fetd~oclc solution of ions to load to the tan cachange chromatographic sclraration cohtmrt are believed co be reprcsenLed by F.quadons ( i ) and (2)) a~ the cross-polymerization reaction of the resultant oxychlorides of Equations (1) and Cl) is believed to be cotxepcuaily rzpreseated by Equation (3).
Z.tt'l,W + H20 !" ZrOCt~"~, + 2H'"o) + 2CI't,~ + heat ( t ) HfC~,~ + H=O ~ HfOCI_"~, + 2H'"v + 2Cft"~ + heat (?) H' ZrOCI,~,o + HfOCI~,~, ~ cZr-Hf~,~ polyt~r compkat (3) The dissolution, r~,,~., dissociation, traction can be represe>~d by Equacioa (4).
ZcOCiu,~ + Hf~OCI."~, ~r ionic dissociation (4l The crass polymerintion side reaction represented by Equation (3) is undrsirabic but rtadity occurs in convern~onal the foodstock preparations of ionic aqueau chloride solutions of zireoaium t also containing bafuium) usod to support continuous ion exchange chromacognphtc Kparatioa technique for the separdcion of zirconium from hafnium andlor of isotopes thereof . Whertas, the method and system of the invention substantially reduces or climtnatcs cross-polymerization side reaction and the_ formation of ia~eparable zacoaitun and hafnium co-polymer oompleacs in solution) prior to and during continuous ion exchange chromatographic separaaoa operations) especially when performed in a continuous a~ulu chromatograph (CAC) a~ in a single operation.
Raferriag now to the drawings, FIGURE 1 is a schematic flow dial of cbe method and system of the present invention for the separation of zirconium from with substantial efiminarion of the cross-polymerization reaction of zirconium and hafnium which forms generally inseparable Zr-Hf co-polymtrized by-products.
As st>awn, crude zircon sand (IO) (ZrSi4J which also contaira haf~m, typically abotu 1 to 5 96 hafnium, is fed to a c6lotinator ( 12) and chlorinated to yield zirconium tertachl(ZrCI,) snd also hafnium teuachtot7de (Hf~CCI,) fraction and silicon tarachloride (SiCla fraction in the presence of a carbon source ( 14), ptrftrably coke.
and chlorite (CIA gas (1~ at a tcmperanrrr in the range of about 800'C to I100~C.
A carbon:zircon sad ratio of about 21:79 parts is preferred. A gasepus steam ( I 8i exits the chlocinuor (12) co~irdag both the ZtCI,JHf~I, and SiCI, fractions and is seiaaveiy condensed in a condenser (20). The selective coation produces two sneams) SiCI, by product fraction (22) and a crude Z.rC141Hf~Cl, fraction (24). The combined ZrCI,/Hf~CI, product fraction (24) is processed further to form a ctucic zirconium chloride-basod feedstoeic sotutaon which is ultimately chromacographica)!y pio~d and d loan zirconium and hafnium metals) and also optionally further separated into zirconium isotopes and hafnium isotopes) to produce high quality nuclear grade materials.
In the ~ present invention, the hydrolysis of the crude carbochlorinatcsl ZrCI,/HfCI, fi9caon (Z4)) according to the hydrolysis reaccion$ as represented by Equations (1) and (2) above, is carefully controlled to subsnmiahy reduce the formation of inseparable zirrotium and hafnium co-polymer cotttplexes as tepresenc~l by Fqt:atlon (3). The cxotherms produced during the hydrolysis reactions along with the fete acid (H') hydrolysis by-product and to drive the cross-polymerization of lhr oxyehtorides of zireonatm a~ hafnium produced during hydrolysis. The ccuJc ZrCI,/HfCI, fraction (24) is) therefore, hydrolyzed under controlled conditiotu wh~h either eliminate the hydrolysis exothetm andlor elimutate the hydrolysis free acid t t! ~ S

1~ -by-prodprx) thereby, in both castes) prevetuing or in~itiag cross-polymerization of harm and zirconium into inseparable compkxes, and in the lacer case also prcvenwig Premature eltuion in the separation cohtmn.
In a first alternative processing method of the invctuion that is used to produce t5e crude aqueous zitconitun eampiexed chloride fe~ocic solutions to support the condatmus ion exchange chromatographic separstioa of zirconium from hafnium, the etude Zt~h/Ht~l, fraction (24) is hydrolyzed with controlled cooling in a two-step aqueous Phase raechod to substantially eliminates both the hydrolysis exocherm and the caratyticaily effecxive free acid (H' ) which both tee to drive the cross polymerization c~actioa of the zircoaittm-hafnium oxychlotide hydrolysate. While previous attempts were trade to use a two-step hydrolysis process as described particularly in U.S. Pat.
No. 5.1I2,493 (Srrydtr. ~ ~.) which targets the reduction of free acid to improve the zirconium sohtbility, a chilled dissolution was neither contemptared nor suggested.
sittoe it was desirable to drive up the temperantrc of flee feodstock solution during the hydrolysis operation in order to use a hot feedstoelc solution during chromatographic processing to futiher improve the solubility of the zirconium a~i not allow cryst$iliTation of the zirconium out of the f~tock solution_ The inventors, however.
ssuprisingly and un~pe~y discovered now that controlling the tempetantre is the da~inant variable in obtaining desirable foedstocic solutions far chromatographic Z0 processing and improving the chromatographic separations.
In tht fast step of this enzbodirnent, excess ZiCI,IHf~CI, fraction (24) is directod in the presence of starved amounts of water (H~On,) (26) to a hydrolysis reactor (28).
such as a turbuiiztr. The hydrolysis tractor (28) 'ss preferably operated at a conu~olled low tempaaritre of about 0~C to 110~C. more preferably about i0~C to 25~C, to remove the heat generaood during the exothermic hydrolysis reaction. Cooling of the hydrolysis reactor (28) can be performed either through an external refrigeration jacket (tat st~ovvn) or the injection of contact refrigerants trot shown), suc4 as super-cooled water, CUz (cooled gas or liquid). N, or U.. The lowering of the temperature anti eontimtal ceawvai of heat substantially eliminates the hydrolysis exotherm which tends to alive the cross-poly~rirstion reaction and productiotl of zituotuum and hafnium co-polymeta.

- I$ -itt the first partial hydrolysis step) a hydrochloric acid (HCl) st'nam (30) by-product is driven off and a crude zirconium oxychloride (ZrOCI~ which also cotttaims hafnium oxychloride (Hf~OCI.,~ (otherwise ZrOCisIHf~OCI~ fraction (32) is provided.
The HCl by-product sttram (30)) which is anhydrous HCI) is direcoed to an HCI
absxba~ (34) and can be scored for reuse 'sn the invention such a: for ux as the ehtanc solution. The absence of HCl also increases the solubility of zirconium in water) tar aitowirtg for higher zircouitur! conxatratiom in the feedstock solution.
1n the accord step of this first alternative embodimem, the partially hydrolyzed crude ZrOChlHhOCh sttx~ (32), which is anhydrous ZtOC>:IHPOCIz, is direucd to a f~COCk solution tank (36), where substantially complete dissohuion and dissociation of the crude ?.tOCiZ/HfaCl: fraction (32) in the prese~ of water (38) or aqueous act, such as HCI, ocetnrs. The acid smngdr during dissohttion dictates wlttther a sohttion of zirconium canons or zirconium anions is prod~d. Zero or low acid coaaotss typically product solutions of Zt0'= and Hf0+r caziom, whereas high acid eonee~ions typically product solutions of ZrOCI,~ and HI~IOCI,~ anions.
The foedstock solution tank (3~ is preferably operaoed at controlled temperature of about 0~C to IIO~C) more preferably about 10~C to 25~C) to yield an aqueous chloride feedstock sohttion (40) of ionic compounds of zirconium and hafnium ions which is suitable for use as rise feed phase for a conzimrouzly operating, steady~statc, ion exchange chromatographic separation column such as a CAC device. Cooling of ctu feedsoock solution talc (36) can be performed eic>1er through an external refrigeration jacket (not shown) or the injection of contact refrigerants (not shown)) such as super-cooled water, CO= (cooled gas or liquid). N= or 0,_. The lowering of the oemperacure of the feedstock solution tank (36) and continual removal of hat substantially eliminates any hydrolysis exotherm and also can provide a cooled aqueous chloride feedstock sohuion to the chromatographic column to improve the separation kinetics-The aqueous chloride-based feedstock solution (40) is aceoctfingly provided with substantial elimination of the formation of zirconium apd hafnitmm co-polytacrs. This results from removing the hydrolysis exothertn and HCl prior to complete dissolution to substantially eliminate the presence of heat and free acid (H+) fraud by the hydrolysis reactions which catalyze atd acce1aste the cross polytaerizatio~n rte) The absence of HCl also incrtasts the solubility of zirconium in avatar.
In a snood alternative mahod (as shown by dotted lines to the left of the first altartative method in Figute 1), the etude ZtCI,lHfCh fraction (24) is lrydrotynod and dissolved with cooling in a one-step direct aqueous phase hydrolysis process to substantially eli~ate the hydrolysis exochcrm which tends to drive tlx cross-polyma~ization inaction. This second alternative axtlmd is the preferred method for the fadsmclc prc~ratiott. in this direct hydrolysis alternative embodimem) the crude ZrCI,/HtCt, faction (24) is directed to a hydrolysis in~ador (4Z) in the prextre of water (44) (HZO~ in the form of crushed ire at a centpaarure of about O~C to 5~C.
preferably about slightly above O~C. The crushed ice (4.4) is. therefore, used as the hydrolysis reagem. The hydrolysis reactor (42) can also be further coolod to maintain a tempaaaue of about 0~C to 10~C, preferably 0~C to 5~C, by either an czteraal refrigeration jacket (not shown) or by the injection of contact refrigerants) e,g;) super-i5 cooled H20) COi (cooled gas or liquid)) NZ or OZ. Ftsttha, in this sa~ond alternadvc emboditnerlt) an ionic aqueous chloride-based fcedstnck solution (4~ of zircoohtm and hafnium ions are produced at a tndtsad temperaourc to substantially elm the hydrolysis exotham. The feedstoek solution (46) is then directed to a feedstock sohttion Cask (3b) which holds the crude aqueous chloride fe~stock solution (40) used rn support chromatographic processing. 'The feeascock solution (40) can also be combizxd with acid such as HCI. 'lbis embodiment is more desirable sirxc although free acid (H') is present in the ion exchange chromatographic feeduock solution (40) which can have catalytic effete on the cross-polytneriz'aaon of zirconium and hafnium is the separation column, the oemperature impact on the cross-po~lymerirtciott ceacavns is found to domitnte.
In a third altamrive mahod (as shown in dotted lines to the right of the first alta~oative method in Figure 1), the crude ZaCI,/FifCl, fraction (24) is hydtolyzed with steam (water vapor) ip a two-step vapor phase method to subs~atially eliminate the free acid (H') catalyst which reads to catalyze the cross poIpmerization reaction of the zirconium-had oxychloride hydrolysatc. and which also leads to cause preananrre elution of the zirconium or hafnium product fraction in the separation column.
In the first step of this third altanuive embodimetu) the ZrCI,/HfCI, (24) is directed ro a sublimation reactor (48) where it is caused to sublime oo its vapor phase n a tanperature of about 300~C to 500~C, preferably abotu 330~C to 450~C) and a reactor pressure of about 5 to 35 psi. prcfaably 10 to 20 psi. lherafter, the ZrCI,IHfCI, vapor (SO) is dirt to a hydrolysis reactor (52) where it is partially hydrolyzed in the prexnce of water vapor (steam) (54) at a temperature of about 100~C to 300~C, preferably about 100~C to 200~C, and a pzessure of abort 5 to 35 psi, preferably about to 20 psi. Act HCl by-ptnduct stszam (30) is driven off and a crude ZrOCI,/HfCCI_ gas fraction (5$) is cooled and coed in a cond~scr (60) co anhydrous 10 ?iOCI_IHfDCts fraction (62). The ZiOCI_IHfnCI= fraction (62) it then directed to a feedscock soh~on tank (3G) where substantially coatpkte dissolution of the crude ZsOChIHPOCIZ fraction is achieved in the presence of water (38) or aqueous acid such as HCI, to yield a entire aqueous chloride-based feedstock solution (40) of zirconium a~ hafnium ions used to support chroa>acographic processing. This embodimeru IS subs~ally eliminates the presence of frx acid (H') which wends to catalyze the Zr-Hf cross-polymerization n:actians and also tends to cause premature ehition of the Zr or Hf ~oduct frscaom in the separation column. Also) since the molecules of ZtCI, and HtCI, are hydrolyzed in the vapor pbax, they are far less liicety to cross-polymerize during hydrolysis. Accordingly. only weak physical associat~n bonds are formed during condeasatian which are easily broken during dissolution and chromaDOgraphic processing.
'Ibe cznde zirconium-hafnium hydrolysate chloride feedstoelc solution (40) pz~ared by either of these duee alternative methods, which all inhibit the formation of zirconium and hafnnum co-polymers. is fed to a cot~tou~sly and steady-state opera4ng ivn exchange chromatographic scparatioa coh~mn (64), preferably a condntious annular chmmatograph (CAC) device. An aquootts dusttt sohition stream (56~, which is preferably as aqueous acid solution, most przfcrably HCI, as will be described in d~il hereiabeiow) is dirccced to the CAC device (64). The zirconium-hafnium feedatock solution (40) is separatod therein into distinct zueonium product ftactions (68) and hafnitttn product fractions 1701 which are also separated and purified of other metal eontamirants, specifically. navy and transition mexal wastes (72) and radioactive m~aat wastes (7~). 'Typically) the transition mewl co~a~inants such as A1, Fe) etc., which ocnu catiottically in the fadstock wlution) and the radioctaxnicai contaminants such as the actinides, which occur anionicalty izi the feedsooclc sohuioa) will gcnaate two separate waste fracaoas) thereby decreasing the waste volume and cling the fonrtatioa of a3ixed wastes for (processing. The heavy and transition zn~als typically do not fot~n complexes which irueract with the ion exchange resins as strongly as the zirconium and hafnium complexes conxque>u1y wash through the chtomaoographic cohrt:ln, while the radiachernical contaminsntc do complex soarewlrat with tine exchange rains and need to be eluted off the chtoraatographic coluflap.
The aqueous zirt:onium product frauion (68) is the dtrecuad first to a zirconium concentrator {76) where it is evaporated and then to a spray roaster (78)) which is prefetrtbty treated by a gas hornet {80~. 'The zirconium prvduet fraction {68) is spray roasted to a substantially pure zirconium oxide {ZrOr) product (78). Tfre ZrO._ (78) is then chlotittated (not shown in the process schematic of Ftg. 1) and subsequently rto nuclear grads zirconium natal.
'The aquoous hafnium product fraction (~0) is subje~d to the same ptoccssing a the zirconium fiction {68). The aqueous hafnium ftactiotr is first conctntrated in a concentrator {84) and then spray roasted in a spray roasttr {8~) which is prcferalstv heated by a gas hornet {88). to produce a substaiuially port hafnium oxide tHiO.~
product (9Q)) The HfOi product (90) is then chlorinacad (not shown ins the process schemao~c of F'~g. 1) and subsequanly reduced to nuclear grade hafnium mesa(.
The aqueous zirco~niwa product fraction (68) and the aqueous hafnium product fraction C70) prior to product recovery steps can be further used if desired as feedsco~l solutions Lo support isooopic chromatographic praccssing in either the same or separatr operation. An inheres result of a resolution of ctle isotopes of a zirconitutr is an efficient separation of hafnium from zirconium. Another inlrcratt result of this isotopes resohrtioa is the efFtcient separation of the heavy and tran~sitioa moral cot~inancs oral radiochemical contaminants from not only the iirronium alai hafnium but also t'tr~m each other.

The aqueous heavy arid transition metal waste fracdoa (72) and the aqueous radiochemical waste 6action (74) arE subjected to volume red~rion (tbt shown in the process schematic of Fig. I ) and can be disposed of as dry solids. T6e disposal of these waste materials as solids is substantially easier than their Qisposai as aqueous or organic liquids. Moreover. they are inherently from each other by the chromatograph so additional processing to separate the heavy and transition moat wastes and radiochemical wastes is not required, thus the disposal of tl>ese two classes of wastes less burdensome. This capability provides an additional waste The acid ett>a~ (6~ can be recycled in a t~ecyck lip (92) after it has born passed through the CAC (64). This acid eiuant is recycled through as acid absorber such as the HCl absorbs (34). In addition) acid, typically HC1) from the zirconium conc:enaator (76) sad spray roaster (78) and the hafnitun oo~rator (84) and spray roaster 86 is diresud along acid recycle line (94) to the HCi absorber (34).
The HCl acid eh>aat is stored in an acid feed storage tank (9b) from which it is pumped back to the contimtaus annular cbromatograph t64) along an eluaai supply lip (66).
Some acid is typically generated by the present process) usually in the fiorm of HCI.
Some of the chlorine supplied to the chioriaator ( 12) will react with the zircon sad and coke to form the SiCI, by-product (22). The remainder of the CI= forms hydrochloric acid !98) which may be c~tbitbed with the acid eluant and usod in the chromatographic separation. Sure all barren acid eluant streams are recycled directly to the chroaratograph, there are no aqueous wastes to be discharged.
It is pnfarod that the feed phase (40)) i.e.) the crude aqueous chloride feedstock soh>tion of zirconium and hafnium ions) have a concentration of crude zirconium and hafniupa as high as is compatible with the solubility under the anticipated operating conditions, i,~, close to tht solubility limit. The natural consequence of ion exchange chrou>atographic separation is a dilution of the concentration of the products being separated info distinct product fractions. Thcttfotr) the overall efficiency of tht process and particularly a minimization of the cfforu nuded to recover the desired product fraction is best served by using as high a concentration as possible in the f~dstoclc solution vvithotit creating an undue risk that zirconium will precipitate out dtui~ the separation process. It is preferred to use a zirconium concttar~ttron in the feed phase of about 50-200 gll) preferably about 130 to I40 gll. The solubility of zitconittm at 25~C in water is about 130 g/1 or greater and h125 w10 HCI is about 20 g11 or less. The zirconium solubility, however, drops steeply with increasing HCl oo~nc~rations) and ranges from about 200 g/1 at 2N HCI to IO g/1 a 6N HCl at 25 ~C.
Accordingly, lesser amottnu of HCl provide for higher conct~ations of zirconium in the feedsoock solutivus.
It is preferred to effect elel Zr am! Hf separations in at Least one first ctaomatogtaphic cohtmn using the aqueous chloride feedstock sohuions of zirconium and hafnium ions as described above and, if desired, then effect isotopic separations in at least one subsa~em chromatographic cohimn using a tefmcd aquoous feedstock solution obtained from the Orst column.
It is ptzfetred that the mobile phase or ehiant be any aquoaxs acid solution cable of solvating the zircotmrm ions such that they ran be ehtted down the column.
This mobile phase or eluam is a fluid capable of displacing the zirconium ions from their ionic association with the stationary phase. It is ptzferred w use aque~s chloride solutions as the eluant) sia;e chloride feedstock solutions mixed with other acid chemistries can tasult in additional waste lion and additional processing to separate ttte mixed chloride and other acids for recycle. It is most ptzferred to use an aqueous solution of hydrochloric acid (HCl) although other acids such as petchloric acid (HC10~, sulftutic acid (H=SO~. nitric acid (HNO,) or the like may also be used.
The drawbacks of using mixed chloride feeduock solutions) and sulfate eluant sohuions, are furor explored in co-pcnding U.S. Patent Application Serial No.
01,,-, now U.S. Percent No. _,- -, of inventors C.H. Byers) W.G. Sisson.
T.S. Snyder, R.J. Heleski. T. L. Francis. and U. P. Nayak, which is entitled Zirconium and Ha~'nuwt Separation In S~elfate SoGuio~es Using Continuous lon Exchange Chromatogrraplry, the disclosure being irscorporatrd by reference herein in its entirety .
The acid saengrh of the eluant needed is dependent on the naaue of the ions.
either or anzo~. Since the zirconium solubility drops very steeply with izanrasing HCI concxtnradons, ehtant concentrations should be from about 2N to 4_5N
HCI, more preferably from about 2.5N to 3.0N HCI. Etuant cott~tion5 greater rhea about 4. SN HCl are not especially ptefarod due to the tow solubility of zirconium. Also, eluanc eoncenuatiom less than about 2.0N HC1 sre not capecaally preferred due to high tzu~ion time in the chromatographic cohrmn as we4 as high product dilution with eluaat in order to elute the product from the column, which both increase ptrecovery costs. Tire precist acid s, however, will depend upon the tenure of the active groups of the stationary phase and the ehtant acid species. h is also possible to use water as the eluant) since it will form a amre dilute solution of the feed phase as it passes down the column.
The preference for a hydrochloric acid (HCl) ehtarx is based on both its advaatagews chernicat a~ tr$asport interactions with 6a~un and zitronium and its coanpatibiiiry with the crude aqueous chloride fxdstock solutions of zirconium and hafnium ions which reduces waste generation. The separation of zirconium from Im5>ium and the separation of the isotopes therzof is particularly efficient with HC1 as the eluant) indicating that it promotes an optimum balttnoe Of affini~cy to and release from the stationary phase ion exchange rain beads. Sire the fecdstoclc is obtained by chlormatiag arvon sand and hydrolyzing the msuitant tea~chlotidcs into oxychtviides. they are) of course) highly compatible with hydrochlotk acid.
The mobile phax can also inchtde other additives such as crown ethers) chelants, and the lilac which can amplify the elution mechanism. The mobile phase is also preferably recycled and for reuse.
Also. axotding to the feedstock preparative scheme as fully described hereinabove, the removal of the excess (H' ) fru acid io~a during the feed preparation hydrolysis reactions advantageously allows clue feedstock sohuion of ions to load in the contii~ously operating ion exchange chromacographie cohunn without prennature elution (or leakage) of the xirconiutn or hafnium ft~actioc~s due to the pr~~ce of free acid in t4e feedstock solution.
It is preferred thu ssationary phase be arty cationic ion exchange resin with an affinity far arconium dons in the feedstock solution) typically in the form of Zr0=' and HfO~' or the lr7oe. It is preferred that the cationic exchange resift be capable of displaying a very strong affinity for zirconium callous. Ptafetnd cationic exchange resin can be based on active groups of carboxylic. sulfonic, phosphoaic acids, in the hydrogen form, or the tike and include mnf~ and strong acid ctsins, for example.
Dowex SOW-X8 resin sold by lbw Chemical Corporation) or t6c tilte. The stationary phase can also be any aaiotdc ion exchange resin with an~ affinity for z~ot>i~m anions in the feedstock solution) typically in the form of ZrOCI,~- and Hf~10C1,~- or the likt_ Preferred aaiocric exrdrrage resins can be based ozi active groups of quaternary ammonium or amino groups or the lixe) in the chloride form, a~ include weak and sarong base resins. The use of anionic exchange resist tends to es~ce the separation since in this case chloride ions, not hydrogen ions, art the ettrmc species.
ltefereucc can be made W Perry's Chenricat Engineers Hartdbaolc) McGraw Hill Publishing Co..
NY, NY, 6th edition (1984), pp. 16-1 to 16-48 including Tabk 16-4 for a description of cationic aril anionic exchange resins suitable foe use in the method and system of the invention, this disclosure being hereby incorporated by referttxe herein.
It is also prefezred that the ssatiorrary phase have a moaodisperse disuibution of spherical parricles with an avenge particle size of less than about 10 microns, preferably less that abotu 1 micron. h is further preferred flat the stationary phase have a high ionic capacity per unit volume) preferably beg about 0.01 to O_5 niilliequivaknzs pee milliter.
The effective cohnnn height should be suff'rcietu to allow significant resolution of the hafnium and zirccmium into distinct product fractions. If desired, the effective column height ttlay be it'rcreased to allow sigtiifecant resolution of various isotopes of the element of irt, zircortittm or hafnium. irno distinct product fractious.
Ttu resolution is preferably sufficient to yield art element or isotope purity at least of about SO% ( pr~cferably in excess of about 9096 . nfore preferably at least about 98 % . It is preferred. to have zit~coninm prtconccntntion greater than about 10 gll, preferably g:eater rhea about 15 gli) more preferably between about 20 to 190 gll exiting the chr'vmatographic cotttmn is the Zirconium product fraction. It ~ further preferred to attain a product purity of less than 100 ppm hafnium is the urcouiurrl product fraction) preferably less ttraa 50 ppm. It is preferred that this resolution be effected in a single pass through the column. The effectwe sotumn height aid foe a given resolution can be esdmnated from an application of the Kremser-Brown Sounders equation.
to eaapirical data on the separation capacity of a given feeduock, ion accW rage resin, eltrant) and flow conditions.
A theoretical separation factor alpha, ore) is used to defiae the ability to separate the variws elements and isotope. This factor c~ is itself defined by the following formula for the binary case:
~ = (Y~(1-Y))~(x(1-x)) where y is the molar coixxatration of the elar~t or isotope iz< the product rich 6raction ( "treads") is thu eletnera or isotope) and x is the molar cone~ation of the same elematt or isotope in the product pool fraction ("tails") m that eletacnt or isotope. Theoretical stage separation factors) a" are coavenieady evacuated on 25 to 100cm test cohratm) with a 25cm column being preferred. T~ preferred feedstocks.
eittants, ion e~tchangt ttsins atd conditions should have a separation factor of about 1.001 to 1.5, preferably about 1.03 to 1.10. The effective cohann for the desired separa:ioa is then deoermined by estimating the number of theoretical stages.
1S N) required of 25 cm each in latgth by the following fonz~:
N = In allrt a,.
The effective cohtmn height can be vertical but it can also have ocher orien~dons. what is important is the effective path over which the mobile phase travels. It is preferred that the path be provided is such a way that the chromatographic sepzrariOn calf be operated contitntously. Presetntly) there is ram coaveni~t ~niqtu available for instantaneously sensing the concentration of the product fracdoru. Thus, there is a preference for a continuously operating metlxxt which has reached steady-state so that a particular product fraction reproducibly has a certain product distn~ution. If the ion exchange chromatogaphic separation m effected in a discontinuous or batch manner. random variations betwreen runs may make it diflicttlt to reproducibly collect product fractions wine the same product distributt~~n from run to tun. For ia~tance, if a single verrical coluttm is Loaded in a batch manner the elutnon time of the product fraction rich is a particular prod<ux may vary from run to rue due to random variables difficult to conuol such as feedstock concentrauvn flttcarations, etc.

It is t~rrther prcferrcd according to the method and system of the invention to optimize the separation idnetics through control of the f~OOCk solution) eiuant solution andlor cinoulatpg:aphic cohuaa temperature during ion exchange chromatographic operations. As shown in Table 2. airconium and hafnium separation Macs are temperature dependent with a n~~mtm separation factor alpha obtained between about 0"C and S~C. Thus by controlluzg the cohimn temperature) and/Cr the feedstocJc and eluant solution taazperatura, the present invention tends to optimize the separation of zirconium from hafnium. Moreover, controiling the column temperature will tetyd to reduce any cross-polymeriution of the zircvnitnn and hafnium which may also occur in the separation cohunn during ion exchange chromatographic operations.
Ta 1e ~
Z'~roonium and Hafnium Sepuu~a Ki~etics au Dower SOW-X8 Cationic Exchsaat Resin Run Tea~p_ Alpha f'cf 3.16 15 3.l0 4.5 4.38 o s.as ZO -5.3 5.32 Referring again to the dtawings, FIGURES : and 3 show a the continuous aluntlar chromatograph (CAC) (64) preferred for use in the method and system of the pr~s~ invention, A detailed description of the materials of construction, design. and operatic of a CAC can be found in the earlier mentioned U.S. patents which are 25 incorporated by reference herein in their entireties. A particularly preferred continuously operating chromatognph is the continuous annular chtomatograph devuoped by Oak Ridge National laboratory.
Such a CAC device (64) comprises two concentric cylinders ( 100) and ( 10'_ ~
which define an ansxtlar column ( I04) which is rotated about an axis ( 106) of tir cohttnn {104). 'Ibe annular column ( 104) includes a stationary phase material.
such as ion exchange resin beads ( 108), packed between the two concentric cyli~clen ' (I()~ atyd (102) of differing diameters with vertical axes to form the annular column For ease of illustration, the ion exchange resin beads ( 108) are shown as only partiatla filling the ar>nular cohrmn (104). One or more fudstock ports (110) is provided at a given angular position which supplies a fudstock solution to the ion exchange resin beads (108) which arc packed in the anmtlar column (104). One or more eluant pore ( 112) are provided at some angular offset from the feedstock port ( 110) which supplies an ehiant to a layer of glass beads ( 114) which sit atop the t~esin beads ( l08). it is preferred to place a layer of glass beads ( 114) above the stationary phase material, and to feed the eluant on the top of the glass bead layer while feeding the crude aqueous.
chloride-based zirconiumlhafnium feedstock (40) directly to the top of the stationary phase to prcvcrg any undesired mixing effxts.
i0 The CAC chrotnatograph (64) also i~iudes a number of product delivery ports ( i 16) set at different aagular positions which can be set arbitrarily to accommodate particular operating conditions. Each product port ( 116) collects an elution volume containing a distinct product fraction which has had a ~rticular tESideace time in the annular column (104) of the chromatograph (64). T'6e CAC (64) is operated by rotatiag tire angular column (104) packed with ion exchange resin beads ( 108) by a mornr (not shown) at a constant speed so than arty vertical segment of the annular bed is above a particular feed product collection port (116) at a given time after this ~nr has hem loaded with etude aQue~s) chloride-based zirconiumlhafrlium fcedstock (40) and eluant (66) solutions. Thus, each product collection port (116) has an angular position which corresponds to a particular elution time for a particular rate of rotation of the stationary phase resin beads (I08) and for a particular flow rate through the stationary phase.
The flow rate through the stationary phase ( 108) is controlled by the pressure drop across the effective height of the stationary phase and the physical characteristics of the stationary phase) ice., particle size and packing void volume. This pressure drop may be provided by the hydrostatic head of the fcedstock and eIuurt. bar it v preferably providod by pressurizing the device. The pressure rtquirtd to achieve a particular flow rates is governed by the Mature of the stationary phase i_e_, its packing.
average particle size and particle size distribueion) _ The smaller the average panic le size of the resin beads making up the stationary phast) the larger the pressure drop t~equired to obtain a particular flow rate over a particular effective height will be Howvever) the separarion factor for arty given theoi stage is improved as the average particle size of the t~esin beads is decreased. Thus, the effxtive height need to effect a given degree of separation is decreased as the separation capacity of a unit leagtb (or theoretical stage height) is increased by decreasing the average particle size of the t~esin beds.
A short residence time in the chromatograph allows an increase in the zirconium and hafnium concentration in the product elution volumes. In general, the longer the residence time in the chcnrnatogtaph is, tlu more "bad spreading' occurs.
"Hand sprr~ding' is a term of art used in this context to describe the phenomenon that can be observed when the longer the residence time is) the larger the proportion of the total elution volume which contains sottte of the desired product. To obtain all or a certain percentage of this product fraction, it is neressaty to collect a vohrme of eluant which increases with residence time. Thus, the net effect of band spreading is to dilute the zitrotrium ami hafnium metal con~ration in the product fractions.
The flow rate across the effective height of the stationary phase ( 108) and the romtioaai speed of the stationary phase should be coordinated so chu a particular produu fraction always elutes at the same angular position ate) consequently, is always delivered to the same producx collection port ( 116).
It is preferred that the chromatograph be operated in a displacement mode whet~ein no more than about 5 percent, more preferably no more than about 1 percent of the effective column height, is loaded with feedstoclc solution before elution is inrtiaaed. The angular displaxrnent betwoen the feed port and the eluant port and the speed of rotation of the at>twiar bed are coordinat4d so that the tiube interval between losdirtg and elution is just sufFcient for the desired degree of pe~oetration.
The telt;tioaship between the time for loading and the depth of penetration is in turn governed by the flow rate through the annular bed.
Tire displactmem may be effected by either an isocratic or a gradient supply of ehsant. In the former case, the eluant can simply be supplied from a single port while in the inner eras, several percs at successively greater angular displacements from the feed poll are utilized. In the gradient mode, elution under the influence of the initial eluant is permitted to proceed until some separation has been effecttd, and iherr e>uanc _3a_ with a higher conxatration is wpplied. This increases the migration spend down the column and minimizes the range of elution volumes or times over which a gives component or product tiracdon will exit the column or, id other words, this procedure minimizes the band spreading. Further, by cooling the chromatographic cohtmn as well as the faodstack andlor eittant solutions, and waiting ttt>ill the zirconium and ttafnixmt wave frotus are sufficiently separated prior to gradient injection, the pr~exnce of a high free acid tai') catxetueatian from the elttant does trot induce cross-potyinerization of tile Zirconium and hafnium in ctte column and further improves xparation .
Decreasing the elution volumes by gradient elution or by other mearu increases the coition of the product in the product fraction. Product ca~enu~ations greater than about 2glt, pccfet3bly greater than about 20 gli) especiatiy between about 20 and 70 g/l are preferred. It is prcferied to maximize the cottcetttration of product because the total volume of fluid to be proressed will be reduced. This allows a reduction in the overall size of the system with a consequent reduction in capital sad operating expenses. However) pt~ctical considerations) such as sohtbiIity limits, will coastrain the maximum concentrations obtainable.
The flow rate down the chromatogcapb is governed by the presserrc drop from the top to the bottom of the chrnmatograph anti the nature of the sutianary phase, The smaller tht average panicle size of the resin beads malting up the stationary phase is.
the higher the pt~we drop that is required to obtain a given flow rate. 'Ibis relationship is also aff~ by the particle size distribution of these resin beads. There is, however) a maximtmm attainable flow rate for any given t~esin stationary phase which cannot be exc:ceded by tfx application of additional pres~u~c. The suppliers of such resins race them in terms of flow rate per gwen pressure drop and tttaximtun attainable flow rare.
It is preferred to use a stationaw phax which will permit flow t7ues between about 2 a~ 80, mozc preferably betty ern atxmt 3 and 20 gallons per minite per square foot of cross sections! sera (between attc~ut 1. 36x t0'' and 5 .43xI0~ztn'lsee. more preferably between about 2.04a10'' and t z6x tOrm'Ixc per squats meter of ctosc sectional area). There is a relationship txtween the achievable flow rates and the ef~xtiv~ chromacograph colutnu height needed for a given degree of pt:rity.
Foc a given system of stationary phast and eluaat, the theoretical stage separation facoor, as.
of the stationary phase will increase as the average particle size of the t~esin beads of ttrc stationary phase decrease. However, as this particle size dues) so does the flow capacity of the stationary phase. Thus) there is an inverse relationship bccween a, and the flow capacity. A higher flow cafe will require a greater effective column height to achieve the same degree of separation or product fraction purity _ Fur~trmore) tbetz; is the additional constraint that the prcssitrt required to achieve the desired flew rate should not exceed the capability of available pumps, seals aai fend tubing. The roquired pressure is a function of both the presseuz drop needed per unit of effective height and the total effective height requited for the desired degree of separation Thus, as the flow capacity of the scativstary phase is increased by ;t cbrauuge in iu physical co~guration and, conseqcxntly) its thevr~iall stage separation faaor. a,. is decreased) tbx required effective height and the required overall pressure IS drop are both iacrra~d. On the ocher hand) as the cbeoretieal stage separaoon factor.
a" is incr~d by a chapge in the resin bead size distributyon so that the flow capacity of the stationary phase is decreased) the pressure drop for a given effativ~
height m in~ed. A pteferrod pttrssure drop of less than about 2759 kPa (400 psi), morn especially between about 345 and 1042 kPa (50 and ISO psi). is preferred.
Thus) to obtain a system with a commercially practical capacity) it is r>,ecesun to use a stationary phase which wilt simultaneously display both a reasonahlr theoretical stage factor) a" and a reasonable flow talc per unit of effective height wneh a reasonable pm~tlre drop. This can be achieved by an a~ro~priate selection of hcnh the capacity of the stationary phase resin attd eluant.
h is preferred that several product collection ports be used to collect a particular product faction. This is alccotnplished by closely spacing these collection ports so that they mere than span the angular range of rotation that cotnspo~s to the elution t~m~
interval of that particular fraction. but do not extend to angular positions at which am sib portion of air otter product iracnon is expected to elute. Of course, tht~
red that the ehnion time intervals of different product fractions do not substarmr!!.
overlap. That is, the alpha (a~ values should exceed 1) and should preferablyx .n the ran~~ of about i .Ol to 1.10) for all specks. This atramgetneru tends to insure that minor fluctuations in the steady-state elution behavior which would cause a slight advancement or retardation of the elution time of the desired ptndtret fraction will rant result in any toss of this fraction.
As the chzomatograph rotates contirruousty, the ptvduct fractions in the feed are separated so that try are angulariy displatxd from the feed iNet. The four product fractions of primary eo~ern are the zirconium fraction, the hafnium fraction) the heavy and transition metal waste fraction) attd the radiochemical waste fraction. An additional ptndrrct fraction also rzpresenu any miscellaneous product prrsent in the feed solution which can be recycled to the column for lttrther processing. The separated product fractions are collected in the collection vessels attd procGSSed further a5 desctibed about.
Only a single continuous anmtiu chromatogreph has been described is conpection with the presort ptboess. However) nay number of continuous annular IS chromatographs may be employed in the prr~srnt procccs. For exatr~le) two or chrre such chrannato~aphs may be effectively used. Each chmmatograph urm would requite a supply of zireonium/hsfnium feed and would produce the product fractions described Table 3 below xe forth purely exemplary and ~n-limiting chromatographic operating conditions for ach~wing the efficient and effective sepuation and purification of zirconium a~ hafnium in accordarxe with the method and system of the present irtvetuion. Other ezaatples and variatiotu will be appareru from a co~ideration of the specihcatio~ or from practice of the invention.

_ Tabk 3 Hf Ions1 g Feed Phase (?x and rwo-step Patvat p~,~ Hydoiysis 0C so lI0C 10C o0 25C

One-SaeP Di~eu Hydrot~is oc m loc cc~d loe~ oc t,o sc vapor i~x H~oaysi~

laoC o0 300c 100C o0 3aoC

co~rarioon so to ioo ga too to ioo ~l sold For Catioas Waoes Water HCl I Acid Concentndon 0 to bN 0 w 2N
S

Hcl Hcl Acid Couceaintioo 0 to 5N 0 00 2.5N

Stationary Phase e Itrsio) (Ion Exchtna Type Sao Acid or weal -1 gtwR

acid Ca>;onic 'Ex~

Resin:

sao~ au~ ~ w~ -1 gin Base Anionic Excltaaae R~

P~arncle Sift Mean Ol w 50Q microns < 100 microns Distribution Polydispax a Mottodisperse Mo Arbitrary Spherical Mobile Pbaae (Eluaat) Wzcer HCl HCI

Acid Coaceatradoa 1.0 to SN !.5 0o Z.SN
for Zr Elneion !.5 to 5N
for Ht F~on F3a~pa Mode Gradietu and Gradie~

tsocratiC

D~ssolotion Te~xaatre0C to 25'C 0'C w S'C

and Operating Ttxopenwre _ Industrial Amlicabil~ty The process of r>x present icrvention will find its primary application in the production of nuclear duality zirconium and hafnium t>'>enls and isotopicahy enriched zirconium and hafnium metals for nuclear reactor conswction maoerials whcn is is desired co employ a simple) iow cost process for the xparation and purification of zirconium and ha&tiinm and isotopes thereof.
The invention having bean disclosed in connection with the foregoing variations and examples, additional variations and examples will flow be apparent t0 persons spilled in tt~e art. The invention is not intended to be limited to the variations and examples specifically mentioned) and accordingly reference should be made to the appended clams, to assess the spirit and scope of the invention in which exclusive rights are claimed.

Claims (20)

1. A continuous method for separating and purifying zirconium and hafnium, which comprises:
(a) preparing an aqueous feedstock solution of zirconium and hafnium ions;
(b) loading the feedstock solution to a continuous ion exchange chromatographic column containing an ion exchange resin;
(c) feeding an aqueous eluant to the column to elute the feedstock solution from the ion exchange resin; and, (d) separately collecting a substantially pure zirconium fraction, a substantially pure hafnium fraction and at least one waste fraction;
characterized in that the temperature of the feedstock solution in (a), both during preparation and any subsequent storage thereof prior to loading to the chromatographic column in (b), is controlled to inhibit cross-polymerization of zirconium and hafnium.

2. The method of claim 1, in which step (a) further comprises:
(i) chlorinating zircon sand in the presence of carbon to produce a crude ZrCl4 and HfCl4 fraction;
(ii) partially hydrolyzing the crude ZrCl4 and HfCl4 fraction with water (H2O~) at a temperature of about 10°C to 25° to produce a ZrOCl2 and HfOCl2 fraction and HCl fraction;
(iii) removing the HCl fraction for reuse;
(iv) dissolving the ZrOCl2 and HfOCl2 fraction in water to form the feedstock solution of zirconium and hafnium ions.

3) The method of claim 1, in which step (a) further comprises:
(i) chlorinating zircon sand in the presence of carbon to produce a crude ZrCl4 and HfCl4 fraction;
(ii) concurrently hydrolyzing and dissolving the crude ZrCl4 and HfCl4 fraction with crushed ice (H2O~) at a temperature of about O°C to 5°C to form the feedstock solution of zirconium and hafnium ions.

4. The method of claim 1, in which step (a) further comprises:
(i) chlorinating zircon sand in the presence of carbon to produce a crude ZrCl4 and HfCl4 fraction;
(ii) subliming the ZrCl4 and HfCl4 fraction at a temperature of about 200°C
to 450°C and a pressure of about 5 to 30 psi to form a ZrCl4 and HfCl4 vapor fraction;
(iii) partially hydrolyzing the ZrCl4 and HfCl4 vapor fraction with steam (H2O.omega.) to from a ZrOCl2 and HfOCl2 vapor fraction and an HCl vapor fraction;
(iv) removing the HCl vapor fraction for reuse; and, (v) condensing the ZrOCl2 and HfOCl2 vapor fraction to an anhydrous ZrOCl2 and HfOCl2 fraction;
(vi) dissolving the ZrOCl2 and HfOCl2 anhydrous fraction in water to form the feedstock solution of zirconium and hafnium ions.

5. The method of claim 1, in which said continuous ion exchange chromatographic column of step (b) is a continuous annular chromatographic column.

6. The method of claim 1, which further comprises:
(e) separately processing the zirconium fraction and the hafnium fraction to produce nuclear quality zirconium metal and hafnium metal;
(f) volume reducing the at least one waste fraction for disposal; and, (h) recycling the eluant for reuse in step (c).

7. The method of claim 1, in which the ion exchange resin is cationic or anionic exchange resin.

8. The method of claim 1, in which the aqueous acid eluant comprises HCl.

9. The method of claim 1, which further comprises:
(e) separately processing the separated and purified zirconium fraction and hafnium fraction to produce isotopically enriched nuclear quality zirconium and hafnium by repeating steps (a) to (d) independently for each zirconium fraction and hafnium fraction.

10. The method of claim 1, which further comprises operating the column of step (b) at a temperature of about 0~C to 5 ~C.

11. A continuous method for separating and purifying zirconium and hafnium, which comprises:
{a) preparing an aqueous chloride feedstock solution of zirconium and hafnium ions;
(b) loading the aqueous chloride feedstock solution onto an ion exchange resin contained in an ion exchange chromatographic column of a continuous annular chromatograph;
(c) feeding an aqueous chloride eluant onto the ion exchange resin to elute the feedstock solution along the ion exchange chromatographic column of the continuous annular chromatograph;
(d) continuously rotating the continuous annular chromatograph during steps (b) and (c) while the aqueous chloride feedstock solution and the aqueous chloride eluant diffuse through the ion exchange resin;
(e) separately collecting a substantially pure zirconium fraction, a substantially pure hafnium fraction, and at least two waste fractions at collection locations on the continuous annular chromatograph angularly displaced from each other;
(f) separately processing the zirconium fraction and hafnium fraction to produce nuclear quality zirconium metal and hafnium metal; and, (g) recycling the aqueous acid eluant for reuse in step (c);
characterized in that the temperature of the aqueous chloride feedstock solution in (a), both during preparation and any subsequent storage thereof prior to loading to the chromatographic column in (b), is controlled to inhibit cross-polymerization of zirconium and hafnium.

12. The method of claim 11, which further comprises:
(h) repeating steps (a) to (g) to produce commercially useful quantities of zirconium and hafnium product fractions.

13. The method of claim 11, in which step (a) further comprises:
(i) chlorinating zircon sand in the presence of carbon to produce a crude ZrCl4 and HfCl4 fraction;
(ii) partially hydrolyzing the crude ZrCl4 and HfCl4 fraction with water (H2O(I)) at a temperature of about 10~C w 25~C to produce a ZrCl2 and HfOCl2 fraction and HCl fraction;
(iii) removing the HCl fraction for muse;
(iv) dissolving the ZrOCl2 and HfOCl2 fraction in water to form the feedstock solution of zirconium and hafnium ions.

14. The method of claim 11, in which step (a) further comprises:
(i) chlorinating zircon sand in the presence of carbon to produce a crude ZrCl4 and HfCl4 fraction;
(ii) concurrently hydrolyzing and dissolving the crude ZrCl4 and HfCl4 fraction with ice (H2O(~)) at a temperature of about O~C to 5~C to form the feedstock solution of zirconium and hafnium ions,

15. The method of claim 11, in which step (a) further comprises:
(i) chlorinating zircon sand in the presence of carbon to produce a crude ZrCl4 and HfCl4 fraction;
(ii) subliming the ZrCl4 and HfCl4 fraction at a temperature of about 200~C
bo 450~C and a pressure of about 5 to 30 psi to form a ZrCl4 and HfCl4 vapor fraction;
(iii) partially hydrolyzing the ZrCl4 and HfCl4 vapor fraction with steam (H2O(~)) to from a ZrOCl2 and HfOChl2 vapor fraction and an HGl vapor fraction;
(iv) removing the HCl vapor fraction for reuse; and, (v) condensing the ZrOCl2 and HfOCl2 vapor fraction to an anhydrous ZrOCl2 and HfOCl2 fraction;
(vi) dissolving the ZrOCl2 and HfOGl2 anhydrous fraction in water to form the feedstock solution of zirconium and hafnium ions.

16. The method of claim 11, which further comprises operating the continuous annular chromatograph of step (b) at a temperature of about O~C to 5~C.

17. The method of claim 11, in which the aqueous chloride eluant comprises HCl.

18. The method of claim 11, in which the zirconium fraction collected in stop (c) has a concentration of greater than about 10 g/l, a purity of less than 100 ppm Hf in the zirconium product fraction, and a yield of greater than about 50%.

19. The method of claim 18, in which the method is performed in a single pass through the continuous annular chromatograph of step (c).

20. The method of claim 11, in which the zirconium fraction collected in step (e) has a concentration of greater than about 15 g/l, a purity of less than about 50 ppm Hf in the zirconium product fraction, and a yield of greater than about 90%.