Note: Descriptions are shown in the official language in which they were submitted.
Tlle present invention relates to methods for reducin~ zirconium
by a reductant metal such as aluminunl which is more economical than the
prior art methods.
The usual naturally occurring mineral from which zirconium is
obtained is zircon, which is Zr02.Si02 (usually also containing about 2%
Hf02.Si02 by weight). In the usual process for obtaining zirconium in its
metallic form, the zircon ore is first chlorinated to obtain ZrC14, for
example, by ~he following reaction:
(1) ZrO2-SiO2 + 3C * 4C12 ~ ZrC14 + SiC14 + 2C0 + C02
The zirconium tetrachloride is then reduced by a reductant metal,
usually magnesium. A typical reduction reaction is as follows:
(2) ZrC14 + 2Mg 7~ C Zr + 2Mg C12
This reduction reaction is usually effected in a Kroll furnace,
in which an excess of magnesium, typical~ly about 80% more than is needed
to complete the reduction, must be provided, and in which the reaction
products (zirconium, magnesium, chloride, and the excess magnesium) are
mixed after the reaction, and must then be separated.
This is obviously a rather expensive method of reducing zirconium
from its ore, and those skilled in the art have frequently searched for an
alternate method which is both practical and less expensive. For example,
since magnesium is a relatively expensive metal, the use of other less
expensive reductant metals have been proposed.
One inexpensive reductant metal which has been considered is
aluminum. ~lowever, if aluminum is used in the Kroll process described
above, the following reaction occurs
! (3~ ZrC14 * (4/3 + x) Al --~ 4/3 AlC13 * ZrAlx
; where ZrAl is a series of intermetallic compounds ranging from ZrA13 to
'~
'' '
,'; ''
.: . : . :
:L~8~75
Zr3AI~ all of which have strong intermetalLic bonds. The rcsu:Ltant product
is thus unllsabIe for one of the primary applications of zirconium, cladding
for fuel rods in nuclear reactors, because of this high aluminum contaminat-
ion. A typical specification for such zirconium allows no more than 75
parts per million aluminum.
Another metallic reduction process for reducing oxides using ~-~
aluminum as the reductant metal is the thermite processO Such a process
is used, for example~ in reducing niobium by the following reaction:
(4) 3Nb205 + lOAl -;~ 5A1203 + 6Nb
The thermite process is particularly attractive for many
applications because, once the reaction is started, it generates a
sufficient amount of heat to be self-sustaining. However, if the thermite
process is used with zirconium, the following reaction occurs:
(5) (4 ~ 3x)Al + 3Zro2 -~ 2A1203 + 3ZrAlx
Again, the zirconium-aluminum intermetallic reaction product
results in this process being unusable for zirconium. Because of the ;
known reactions described in equations (3) and (5) above, it has been .
widely accepted in the art that aluminum cannot be used as a reductant
metal to recover zirconium. See, for example, Warren Bo Blumenthal,
The Chemical Behavior of Zirconi=, which is the leading general reEerence
on zirconium and its properties.
It is accordingly an object of the present invention to provide
an improved method of reducing zirconium.
It is another object of the present invention to provide an
improved method of reducing zirconium which can utilize a reductant metal
such as aluminumO
It is still another object of the present invention to provide an
improved method for reducing zirconium using aluminum as the reductant
metal and in which the resultant zirconium is not contaminated by aluminum.
: :
. ~.~, -,~ - - . . . . . - - , :
z~
~ ri~1y stated, and in accordance with the pres~nt invention, a
method ~f producing nuclear grade zirconium from a zirconium compound is
provided, comprising the steps of preparing a fused salt phase including the
- 7irconiuD~ con~ound to be reduced, and contacting the fused salt phase with
a molten metal phase which comprises alumlnum and zinc. The desired
reduction is effected by mutual displacement, with aluminum ~eing transported
rom the molten metal phase to the fused salt phase, replacing zirconium in
the salt, while zirconium is transported from the fused salt phase to the
molten metal phase. The fused salt phase and the molten metal phase are
then separated, and the solvent metal and zirconiwn are separated, such as
by distillation.
For a co~plete understanding of the invention, together with an
appreciation of its other objects and advantages, see the following detailed
description of the invention and o the attached drawings~ in which:
Figure 1 is a block diagram of one embodiment of the invention,
and illustrates the principles of the invention;
Figure 2 is a block diagram of a second embodiment of the
invention;
Figure 3 is a block diagram of a third, and the presently
preferred embodiment of the invention; and
Figure 4 is a block diagram of a modification of a portion of
the embodiment of Pigure 3.
Th~ present invention achieves reduction o zirconium by a
reductant metal such as aluminum by mutual displacement, without the above-
described problems by first dissol~ing the reductant metal in a suitable
metal solvent prior to contacting it with the molten or fused salt which
contains the zirconium ions to be reduced. The molten metal phase is then
stirred vigorously with the fused salt phase to entrain the f~sed salt
phase in the molten metal phase. I~ has been found that this causes the
, . . .
~ 3
,,"~0
27~j .
mLY~ure to approach equili~rium in less than five minutes with suf~icient
a~itation, and somet~les in less than one minuteO The mixture is then
allowed to settle~ and the fused s~lt phase rises essentially entirely to
the top of the mi~ture~ while the molten metal phase :ls beneath the fused
salt phase. The fused salt phase can then be poured off or siphoned off,
or the molten metal phase can be removed through a suitable tap or like
in the bottom of the container in which the reaction has then occurred.
If desired~ the molten metal phase may again be subjected to
the same process a second time to remove more of the reductant metal from
the molten metal phase, and the entire process may be repeated in as many
cycles as desired to achieve the desired purity of zirconium. The solvent
metal is then separated from the zirconium in any suitable manner, such as
, , .
by distillation or sublimation.
The solvent metal is a metal which has the following characteristics.
First, of course, it must be a metal in which both zirconium and the
;I reductant metal are soluble to at least a significant extent. The boiling
temperature of the solvent metal must be such that, in the range of operat-
ing temperatures of the reaction, both the solvent metal and the fused salt `;
phases are in their liquid phases. The solvent metal should be a metal
which is relatively easy to separate from zirconium once the reaction is
complete. The solvent metal must be less electropositive than zirconium
and hafnium, so that it does not replace zirconium and hafnium in the salt
phase. Final b, it is preferable that the metal have the greater affinity
for zirconium than it does for aluminum, so that the aluminum atoms in
the metal phase are more available for reaction with the zirconium ions ;
in the salt phase to enter into the mutual displacement reaction~ In
practice it has been found that the best metal for use as a solvent metal -~
~ ~,
is zinc, although other metals, such as cadmium~ lead, bismuth, copper,
and tin may also be used as the solrent metal.
- 4 -
,.
.
~B~2~7~
~ pI` in~ary characteristic of the reductant metal is that it is
more electropositi-ve than zirconiwn, so that it can replace zirconium in
the salts, thereby reducing it to its metallic stage. Another important
characteristic of the reductant metal is that it has less affinity for
solvent metal, which is preferably zinc, than zirconium has for zinc, so
that no alloy of the reductant metal and zirconium is formed; instead,
zinc forms an alloy with zirconium and rejects the reductant metal. Also,
of course, it is important that the reductant metal and the salts which
it subsequently forms after the reduction reaction be liquid at the
temperatures at which the reaction is occurring. The preferred reductant
metal is aluminum, since, as is shown in the equations below, the objection-
able aluminum-zirconium reactions described above do not occur in the method
of the present invention, and thus the economies of using aluminum as a
reductant metal can be realizedO However, those skilled in the art will
readily recognize that other reductant metals, such as magnesium sodium
and calcium could also be used in a similar methodO
The characteristics of the salt are as follows: First, the
cation in those portions of the salt which are not a zirconium salt should
be more electropositive than zirconium so that it will not be reduced by
the reductant in the metal phase. Preferred cations are the alkali elements~
preferably sodium and potassium~ the alkaline earth elements~ the rare
earth elements and aluminum. The anions in the salt are preferably halides
or complexes of halides and the cations given above~ so that the salts
are halide salts As is explained in more detail below, the preferred
halides are chlorides and fluorides, with the advantages of each being set
forth oelow.
As is set forth below, the zirconium salt which is present in
the process is usually ZrC14 or ZrF4~ and by providing chloride or fluoride
salts, this allows the formation of ZrCl or ZrF anions, whose va]ence
- S -
'
Z75
is a function o~ ~. The usual such anions formed is ZrF7 ~ ZrC16 ~ or
ZrF6 . These compl~xed anions reduce the vapor pressure of the zirconium
salt to an acceptable :Level at the temperatures at which reduction is
effected.
The melting point of the salt must be below the boiling point
of the metal used as a solvent for the zirconium, in order that both the
salt and the metal may be in the liquid phase at the same ti~e. As is well
` known to those skilled in the art, the melting temperature of the salt, ; -
` as well as the viscosity of the salt~ can be changed by mi-xing various
salts. Thus, it is frequently useful to add an additional salt such as sodium
; chloride to the salt phase to reduce the melting temperature of the salt
and lower the viscosity of the salt.
; ., .
-~ As was noted above, it has been found that the best salts to
use are either an all-chloride salt system, a chloride-fluoride mixed
salt system, or an all-fluoride salt system. The all-chloride salt system
has the advantage of being easier to contain. As is well known to those
skilled in the art, if a fluoride is present in the fused salt phase,
this can lead to difficulties in containment, since the molten fluoride
tends to enter into many undesired reactions with either the container
material or any other materials present in the system. The disadvantages
of the all-chloride salt system is its tendency to form lower valence
chlorides such as ZrC12, the tendency of ZrC14 to volatize from the salt,
and also the tendency of the zinc metal to interact with the zirconium and
....
hafnium salts and enter into the salt phase.
In contrast to this, the chloride-fluoride salt system has a
low vapor pressure~ very slight interaction of zinc with the salt phase,
- and a much reduced tendency to form lower valent zirconium compounds in
the salt phase. The all-fluoride salt phase has the advantages of the
chloride-fluoride salt syste~ and can be used if a zirconium fluoride salt
- 6 -
., ~ .
.. , . . . , . ~
~8~Z'75
is made from th~ ore. However, ;n an aLl ~luoride salt phase system,
carc must be tal~cn in selecting -the concentration of the salt. Aluminum-
~luoride compounds are present as reaction products after the reduction
reaction, and these con~po~Lnds tend to be either very volatile or do not
melt at the reaction temperature unless the salt system is carefully chosen.
The container in which the reaction is carried out must be
carefully chosen so that it will contain the materials of the reaction
at the temperatures at which the reaction is occurring, while not itself
entering into the reaction. A number of different material have been
tried for the container, and it has been found that the preferred containers
are formed from graphite or carbon.
~ aving described the general parameters of the present invention,
let us now consider a specific example of the use of the process to effect
reduction of zirconium.
Figure 1 shows a block diagram of a process for reducing
zirconium in accordance with one embodiment of the invention. In Figure 1,
a reductant metal input lOg a salt input 12 and a solvent metal input 14
are provided to a suitable container in which the desired reduction is to
be effected. The reductant metal input, of course~ is preferably aluminu~.
This metal is provided to a reduction stage 16, along with a salt component
; which might be a mixture of zirconium tetrachloride, which is the zirconium
compound to be reduced, and potassi~l chlorideO Approximately ten moles
of potassium chloride are used for each three moles of zirconium tetra~
; chloride. A portion of the potassium chloride and the zirconium tetra- ;
chloride, when melted, undergoes the following reaction~
(6) ZrC14 -~ 2KCl = K2ZrC16
Typically, a sufficient amount of solvent metal, preferably
~ zinc, is provided to the reduction stage 16 to provide approximately
i twelve weight percent zirconium at the conclusion of the operation. As is
., ' ~:.
:; . . . , - . . . :. .
~L~8~ 5
~escribed below, this zinc input need only be supplied on the initial run,
SillCe thereafter it is recovered and returned to the reduction stage 16
for subsequent runs.
typical charge to the red~ction stage 16 is as follows:
TABLE 1
Input ~omponent Weight
~rC14 100 lb.
KCl 96 lb.
Al 13.9 lb.
Zn 334 lb.
The mixture is then heated to about 900C and is stirred
` vigorously to cause the now molten metal phase to entrain the now fused
or molten salt phase. At this time, in accordance with the present invent-
.:
ion, the aluminum in the metal phase reduces the zirconium in the salt
; phase by the following reaction:
(7) 4KCl -~ 3K2 ZrC]6 ~ 4Al ~O 4KAlC14 ~ 6KCl -~ 3Zr
l As was noted in the description of the desired characteristic
; of the salt above, the excess KCl is provided to reduce the vapor pressure
of the ZrC14 at the temperatures at which the reaction occurs
~ . .
This vigorous mixing is continued for five minutes to one-half
hour, and the mixture is then allowed to separate by settling~ with the
molten salt phase~ now containing the aluminum salt~ rising to the top
and the molten metal phase~ now containing the zirconium metal, settling
to the bottom. After separation by any desired manner, the salt phase is
taken to the stage 18 to recover the salt for subsequent use, if so deslred.
The metal phase component is taken to a distillation stage 20
at which the zinc metal is distilled from the zirconium and is again
available to be returned to the reduction stage 16 for a future Feduction
reaction such as is described above~ Prior to such distillation~ the metal
-- 8 --
~ . - . - . . ... .
%~5
pha~e cont ins th~ following components:
TABIE 2
Component Weight
334 lb.
Zr 35.2 lb.
Al .035 lb.
The zirconium metal is now available at the zirconium output
stage 22, and again consists of sponge metal.
Figure 2 shows a block diagram of a second embodiment of the
present invention. The process sho~m in Figure 2 is essentially the
same as that shown in Figure l~ except now, at the reduction stage 16,
after the initial heating and mixing described above is completed~ and
after the salt phase is remo~ed from the container in which the reduction
; stage 16 is effected, the metal phase is retained in the reduction stage 16
and approximately sixteen pounds of potassium chloride is added to the
container. This salt-metal mixture is then again heated to approximately
900 C, and an oxidizing gas 24, such as two pounds of Cl2 is passed into
the metal~ reacting with the zirconium and aluminum in the metal phase to
form zirconium and aluminum chloride salts which are absorbed into the salt
phase. The two phases are then again well mixed, and the process is completed
in the manner described above. It has been found that this two-stage
process results in a zirconium metal output having an alumin~m content of
less than 40 parts per million.
In the embodiment of Figure 2, rather than using chloride gas
as the oxidizing agent~ any suitable material can be injected directly
into the mixture to form a zirconium salt to provide a second stage of
; the desired displacement reaction to separate the aluminum from the metal `~
phase into the salt phase. For example, zinc chloride has been successfully
:,:, ~
used, and in some instances, it is desirable to inject a zirconium salt such ~-~
~ 9 -
:'
27 ~ !
as ~irconium -tetrachloride directly into the mixture for the second stage
of separation.
The for~going description of the parameters of the present
invention and the description of Figures 1 and 2 have illustrated the
principals upon ~hich the present invention is based. The presently
preferred embodiment of the invention is a somewhat more complex process
than the relatively simple processes of Figures 1 and 2, and comprises a
complete process for obtaining zirconium in which the input material is a
raw zircon ore and finished~ high purity zirconium is obtained as the OlltpUt
product. Figure 3 is a block diagram of that complete process/ and
discloses the presently preferred embodiment of the invention.
In Figure 3, the input materials to be processed are zircon ore,
which is ZrO2.SiO2 containing relatively low levels of HfO2.SiO2, and
sodium silicof]uoride (Na2SiF6). These inputs are represented by the
blocks 30 and 32 respectively in Figure 3. These materials are supplied
. . .
to an ore cracking stage 34, in which the following reactions occur: ;
(8) Na2siF6 + Zr2-Si2~i~ Na2ZrF6 ~ 2SiO2
: , :
) 2siF6 + Hf2-Si2 ~ Na2HfF6 + 2SiO
Typically, the ore cracking stage 34 is effected in an indirectly
fired kiln at a temperature of approximately 700 a for appro~imately one
hour.
The output product is removed from the klln, and the Na2ZrF6 and
Na2HfF6 are leached from the SiO2 and crystalized from the leach liquor.
This is in itself a good purification step for the zirconium, and removes
the zirconium from most of the other împurities which may be present in
the ore other than hafniumO
The Na2ZrF6 and Na2HfF6 are then supplied to a reduction and ~ -
sepsration stage 36, in which they are dissolved in a solvent metal such
-- 10 --
'.
. .. . . . . .
'7~
as zinc, as was described above in conne~tion with Pigu~es 1 and 2. An
aluminum reductant l~al input 38 is also supplied to the reduction and
separation stage 36. In the reductant and separation stage 36, the zinc,
aluminum and Na2ZrF6 and Na2HtP6 ar~ heated to a ten~erature of approximately
900C, at which the entire mixture is molten, and the molten liquids are
s~irred vigorously, ~s in ~igures 1 and 2 above. A* this time, the following
reactions occur:
Zn
(10~ ~ F6 1 4Al --~ 4[(Nar:)l 5-AlF3] ~ 3Zr
and
Zn
(11) 3Na2H~F6 ~ 4Al --~ 4~(NaP~1 5.AlF3] + 3Hf
. :
In the preferred embodiment of the invention, approximately 85%
to 95% enough aluminum to complete the above reactions is supplied to the
reduction and separation stage 36, so that practically all of the aluminum
present enters the salt phase and some Na2ZrP6 is left in the mixture.
It has been previously discovered that any hafnium metal which was formed in
accordance with equation ~1) above displaces a zirconium ion in the salt by
the following reaction:
(12~ Na ZrF ~ Hf ~ Na HF6 + Zr
After vigorous stirring, the mixture is allowed to settle, and
the salt phase is removed from the metal phase, in the manners described
; above. The now separated metal phase is then again ~aken to a distillation
phase 40, at which the z.inc is distilled from the zirconium. The zinc
can then be returned for reuse in the reductlon and separation stage 36.
Virtually pure zirconium is now available at the zirconium output 42.
The following Table 3 shows the input materials, ancl output
product (zirconium sponge) achieved in five typical runs in accordance
,
~ with the process just described.
." v
2~Si
Tl~BLE 3
INPUT ~IATE RIAL ZIRCONIUM OUTPUT
Na2ZrF6 ~ ~5 lb-
Na2Hf~6 - o7 lb
Zn -230 lbo 24~2 lbo
Al - 9.6 lb.
Na2ZrF6 - 85 lb-
Na2HfF6 ~ 0-7 lb.
Zn -231 lb. 24 ~ 3 lb~
Al - 9.6 lb.
-. 10
,, ,_ . ,", ,_ _ , . _ ~ . . _ . . , _
Na2ZrF6 - 85 lb~
Na2HfF6 ~ -7 lb-
Zn -236 lb. 24.9 lb.
Al - 9.8 lb.
._ . _ .. . . . ~ ., .
Na2ZrF6 - 85 lb-
Na2HfF6 ~ 0-7 lb-
Zn -235 lb. 2407 lbo
Al - 9.8 lb.
~ . _ . _ _
Na2ZrF6 - 85 lb-
Na2HfF6 ~ 0-7 lb.
20 Zn -235 lb. 24.7 lb.
Al - 9.8 lb.
In accordance with another of the features of the present
invention, when the salt phase is removed from the reduction and separation ~;~
stage 36 after completion of the reactions described above, it is taken `~
to a salt processing stage 44. At this time, the salt phase is again a
mixture of (NaF)l 5-AlF3, Na2ZrF6 and Na2HfF6, but is considerably richer
in hafnium than was the input salt to the reduction and separation stage
360 At the salt processing stage 44, these salts are again melted and
- 12 -
,
~8~2~i
mL~ed ~ith a molten ~inc bath, and a reductant met~l such as al~inum
is ~g~in provided to the bath. Now, however, in contrast with the reduction
and separation stage 36 described above, a sufficient amount of aluminum
is provided to complete the reactions of equations (10) and (11) above
for the entire salt phase. After this reaction is completed7 the now
virtu~lly pure molten (NaF)l 5-~1F3 is removed from the molten metal phase,
and these materials are provided at the outputs 46 and 48 respectively of
Figure 30
The salt (NaF)l 5AlF3, which may be termed a pseudocryolite,
is itself a desirable product which can be sold to the aluminum industry,
' and thus the only salt by-product of the process of Figure 3 is itself
usefulg and not a waste product. Similarly, in the metals output 48,
the zinc can again be distilled off and reused in the process~ leaving
' only the hafnium, zirconium and slight amounts of aluminum as output metals
from this part of the process. If desired, these metals may be returned
to the reduction and separation stage 36 to further extract any zirconium
` in this metal. In any event, in a typical such process, the amount of
output metal left at the stage 48 is only approximately 5% of the available
metals which was in the zircon ore at the input stage 30.
If even higher separation factors of zirconium from alumin~
and hafnium are desired, in the embodiment of Figure 3, the reduction
and separation stage 36 may also be "fluxed" in the manner descri'bed in
Figure 2 above. If this is desired, the presently preferred manner to do
this is to inject a quantity of ZnF2 into the zinc-zirconium molten metal
after the salt phase has been removed from the metal phase. At this time,
the following reaction occurs~
(13) 2ZnF2 + Zr ~ ZrF4 + 2Zn
The zirconium tetrafluoride so formed then reacts with any
remaining alumin~ and hafnium in the metallic phase in accordance with
275
the following eqnatio~l:
~143 ZrF -~ ~If-` HfF -~ Zr
If ~his second stage of separation is desired, it is the
presently preferred practice to provide enough zinc fluoride to oxidize
- about 2% of the 3irconium in the metal phase. Thus~ in the quantities
.
given in the examples of Table 3 above, it is preferred to use about 1.1
lbs of ZnF2 for this fluxmg operation, if it is to be effected. If an
excess of ZnF2 is provided, it results in a higher aluminum and hafnium
removal, but a~ the expense of a loss of a greater amount of zirconium.
Similarly, if less ZnF2 is used~ a lower hafnium removal is achieved, but
a greater quantity of zirconium remains in the metallic phaseO
It is noted that, in contrast to the processes described in
- Figures 1 and 2 above, in the presently preferred embodiment described in
, .
Figure 3, no excess salt such as potassium chloride, or sodium fluoride
is provided into the reaction at the separation stage. As was described
above~ the embodiment of Figure 3 results in the formation of the pseudo
cryolite salt (NaF)l 5-AlF3. If an excess of sodium fluoride were provided
in thisphase of the reaction, the resultant salt would be ordinary cryolite,
or ~NaF)3 AlF3, which does not melt until a temperature of 1000 a, which
,- .
~ 20 is above the boiling temperature of the zinc-zirconium metal mixture.
; Those skilled in the art will further recognize that the
; embodiment of Figure 3 also reduces ha~nium metal from a hafnium compound
in the same manner as zlrconium is reduced. Thus~ the method can be used
to reduce hafnium, and is a superior reduction method than the prior art
methods of reducing hafnium.
Figure 4 is a block diagram of a modification of the method of
Figure 3, and shows a two stage counter-current reduction process to ~
'
reduce the levels of aluminum and hafnium even lower in the zirconiumO
In Figure 4, the reduction and separation stage 36 is divided
- 14 -
~:~ , : . . , .- .
into two stages, designatcd 36a and 36b. In an initial run, first stage
36~ is supp]ied an initial charge of Na2ZrF6, also containing Na2HfF6,
aluminum and zinc, and the reaction occurs as described in ~igure 3 above.
After the reaction is completed, the salt output is taken to the salt pro-
cessing stage 44, described above, and the metal phase is taken to the
second stage 36b of the reduction and separation stage.
The metal phase at this point might typically contain about 1000
to 1500 parts per million aluminum and 500 parts per million hafnium
(both expressed as a function of zirconium only). These levels are too
high for nuclear grade zirconium. In second stage 36b, the metal phase is
mixed with the salt input from ore cracking stage 34, and the mixture is
again heated to about 900C and stirred vigorously. At this time, the
following reactions again occur:
(15) Na2ZrF6 ~ Hf ~ Na2HfF6 ~~ Zr
and
~16) 3Na2zrF6 ~ 4A1 ~ 4[ (NaF) 1 50AlF3~ ~ 3Zr
These reactions at this time reduce the levels of both hafnium
and aluminum in the metal phase to less than 100 parts per million, again
expressed as a function of zirconium only. Now, the ~xture is allowed to
settle and is separated, as before. The metal phase is taken to the dis-
tillation stage 40, where the zinc is distil]ed off and returned to the
first stage 36a of the reduction and separation stage, and the new high
purity zirconium is taken to the zirconium output stage 42. The salt
phase (which was hardly changed in second stage 36b, since only low levels
of hafnium and aluminum were available there to react with the Na2ZrF6) is
taken to the first stage 36a of the reduction and separation stage, where
new aluminum and zinc from the distillation stage are again provided.
Thus this modification of the process, which may now be termed
a two stage counter-current reduction and separation process, provides
. . . , , . - .,, : . ~: . :,
high purity z:ircon:ium without the use of the fluxing step described in
Fi~lre 2 above.
While the invention is thus disclosed and several embodiments
are described in detail, it is not intended that the invention be limited
to these shown embodiments. Ins~ead, many modifications will occur to
those skilled in the art which lie within the spirit and scope of the in-
vention. It is thus intended that the invention be limited in scope only
by the appended claims.
. , .
''~ . : '.'
,. .
- 16 -
