ORNL-TM-11792.txt

ORNL/TM-11792

Chemical Technology Division

REACTION OF URANIUM OXIDES WITH CHLORINE AND CARBON OR
CARBON MONOXIDE TO PREPARE URANIUM CHLORIDES

P. A. Haas
D.D. lLee
J. C. Mailen

Date Published — November 1991

Prepared by the
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37831
managed by L
MARTIN MARIETTA ENERGY SYSTEMS, INC. © 7~
for the
U.S. DEPARTMENT OF ENERGY
under contract DE-AC05-840R21400

 

 

i VA, SAE rear g &S5, Wy o= o
ST TR e e
et L -.v_.);':g y ]1} Y Bl BAS e e el L L
“EE IR g B T iR g e g o
T T B D i - T
. i:tr"';;t:fi'{?;- L iryr e e

 

 
 
DISCLAIMER

This report was prepared as an account of work sponsored
by an agency of the United States Government. Neither
the United States Government nor any agency thereof, nor
any of their empioyees, make any warranty, express or
implied, or assumes any legal liability or responsibility for
the accuracy, completeness, or usefuiness of any
information, apparatus, product, or process disclosed, or
represents that its use would not infringe privately owned
rights. Reference herein to any specific commercial
product, process, or service by trade name, trademark,
manufacturer, or otherwise does not necessarily constitute
or imply its endorsement, recommendation, or favoring by
the United States Government or any agency thereof. The
views and opinions of authors expressed herein do not
necessarily state or reflect those of the United States

Government or any agency thereof.

 

 
DISCLAIMER

Portions of this document may be illegible
in electronic image products. Images are
produced from the best available original
document. |

 

 
31
3.2
33
34
3.5
3.6

   

CONTENTS

INTRODUCTION . ... ittt et ie i rseraanaenannenns
2. EXPERIMENTAL APPARATUS AND PROCEDURES .................

3. RESULTS .. i i it ittt eatasansenaanaonns

REACTIONS OFCHLORINE ...... .. i iiiieiieaaes
UTILIZATION OFCHLORINE ...... . it
EFFECTS OF URANIUM OXIDE PROPERTIES .................
REDUCTIONS BY CARBON ... ...ttt iiiieneenn
REDUCTIONS BY CARBON MONOXIDE ...............oolss
VOLATILIZATION AND CONDENSATION OF URANIUM

CHLORIDES ... ittt iiieiiaentetnaneaanaaaeans

37 PRELIMINARY RESULTS WITH A LARGER REACTOR AND

BOTTOM CONDENSER. . .+« e oo oo e e e e

4. CONCLUSIONS - oo oo
5. REFERENCES - ..o e
APPENDIX - - o oo e e
A, THERMOCHEMISTRY . .. eo e e e e e e e e

B. INDIVIDUAL TEST RESULTS . .. uonttere e

C. EQUIPMENT DETAILS AND CALIBRATIONS . ...cueueuvunnnn..

iil

 

 
 

 
10.

11.

12.

13.

14.

TABLES

Chlorination test parameters and conditions ........... ... .. .ot 11
Chlorination test results .. ... ii ittt eennennaereeenns 14
Changes in process conditions and results .......... ... ... oLt 18
Changes in apparatus and procedures . .........c.cciiiiiieiiiiiia 19
Chlorination test material balances: chlorine ............... ... ... ... 20
Chlorination test material balances: catbonandoxygen ................... 21
Chlorine losses versus Cl, feed rates using carbon black at ~730°C .......... 23
Properties of uranium oxide, UO,-C, and carbon feed solids ....... e 24
Gas flows and uranium volatilization .............. . it 29
Thermochemical data ..........ouiiiiiiiieiieiieonnnennaennenns 44
Heats of formation for U-O-Cl compounds at 298°K  ..................... 45
Free energies of formation for U-O-Cl compounds at 900°K (627°C) ......... 45
Vapor pressure eqUations ... ......eeenioriactaatii e 47
MS-22 gas flow calculations from totalizer readings ....................... 53

 

 
 

 
FIGURES

Conversion reactions for U-O-Clcompounds  .......... .. ...t 4
Phase diagram for UCL,-UO, ...... . ittt 5
Chlorination reactor (4-cmID) ....... ... . .o 7
Photograph of reactor as removed after MS-8 ............. ... ..ol 8
Chlorination reactor (68-mm ID) with bottom condenser .................. 33
Vapor pressures of uranium chlorides .......... .. ... oo 48
CO, concentrations during MS-22 ........ ... .. it 52

vii

 

 
ABSTRACT

The preferred preparation concept of uranium metal for feed to an AVLIS
uranium enrichment process requires preparation of uranium tetrachloride
(UCl,) by reacting uranium oxides (UO,/UQ,) and chlorine (Cl,) in a molten
chloride salt medium. UOQ, is a very stable metal oxide; thus, the chemical
conversion requires both a chlorinating agent and a reducing agent that gives
an oxide product which is much more stable than the corresponding chloride.
Experimental studies in a quartz reactor of 4-cm ID have demonstrated the
practicality of some chemical flow sheets.

Experimentation has illustrated a sequence of results concerning the

chemical flow sheets. Tests with a graphite block at 850°C demonstrated
rapid reactions of Cl, and evolution of carbon dioxide (CO,) as a product.

Use of carbon monoxide (CO) as the reducing agent also gave rapid reactions
of Cl, and formation of CO, at lower temperatures, but the reduction
reactions were slower than the chlorinations. Carbon powder in the molten
salt melt gave higher rates of reduction and better steady state utilization of
ClL. Addition of UO, feed while chlorination was in progress greatly
improved the operation by avoiding the plugging effects from high UO,
concentrations and the poor Cl, utilizations from low UO, concentrations. An
UO, feed gave undesirable effects while a feed of UO,-C spheres was
excellent. The UO,-C spheres also gave good rates of reaction as a fixed bed
without any molten chloride salt. Results with a larger reactor and a bottom
condenser for volatilized uranium show collection of condensed uranium
chlorides as a loose powder and chlorine utilizations of 95-98% at high feed
rates.

 

1. INTRODUCTION

The feed for an Atomic Vapor Laser Isotope Separation (AVLIS) process for uranium
will be uranium metal.! The principal production of uranium metal for nuclear fuel cycles has
previously been by batch metallothermic reductions of uranium fluoride (UF,) using
magnesium or calcium metal. If this batch metal production were used for a large AVLIS
enrichment plant (=10* ton Ufyear), the costs of the hydrogen fluoride (HF) feed, the
calcium or magnesium feed and the disposal of magnesium fluoride (MgF,) or calcium fluoride
(CaF,) wastes would be major parts of the total uranium enrichment costs. Alternate
processes for preparation of uranium metal from UCI, allow recycling of Cl, from electrolytic
cells.? The products of uranium ore refineries are uranium oxides— most commonly UO;. The
objective of this AVLIS development program was to determine practical process conditions
for efficient production of UC], from uranium oxides.

 

 
There is extensive background literature on the production of UCI, based on reaction
of carbon tetrachloride with uranium oxides.> Such a process was used at Oak Ridge for
producing calutron feed material. Despite this previous experience, a process based on the
use of CCl, would not be desirable for the proposed continuous metallothermic reduction
process in which chlorine values are recycled because of both the risks associated with CCl,
and the fact that recycle of chlorine values would require process equipment for CCl,
synthesis. Such difficulties could be avoided with a process involving direct reaction of
chlorine, carbon and/or carbon monoxide, and uranium oxides.

A search of the technical literature did not reveal any report of the preparation of pure
UCl, from uranium oxides, Cl,, and C or CO. Canning demonstrated nearly complete
utilization of Cl, for up to 90% chlorination of impure uranium oxides,* as a first step of an
overall process for producing purified metal. He sparged Cl, through a graphite diffuser into
molten KCI-NaCl to which he fed the impure oxides. After chlorination, the molten salt
mixture was treated with magnesium metal for reducing uranium compounds and electro-
refined to improve the metal purity. Lyon reported rapid reaction of uranium oxides with
chlorine in molten NaCl-KCl at 850°C to produce UO,Cl,°> Gens studied the volatilization
of uranium chlorides from nuclear fuels and also found the formation of some nonvolatile
UO,CL,* Gibson reported complete chlorination of UQ, using a block of carbon and Cl, in
KCl-NaCl at 860°C as a first step in a process for producing purified UO,.” These results,
along with those using CCl, rather than Cl,, report chlorination of uranium oxides and
removal of oxygen as CO or CO.,.

The use of published thermochemical data for uranium oxide, oxychloride, and chloride
compounds is a first step for identifying probable reactions for the desired chemical
conversion. However, there are several reasons for uncertainties for such predictions.
Uranium chemistry is complex with stable valence states of 3, 4, 5, and 6. Oxides, one or
more oxychlorides, and chlorides have been identified at most of these valence states. The
volatility of the chloride compounds increases with valence state while chemical stability
decreases. All of the compounds have large negative heats and free energies of formation;
hence, calculation of free energies of reaction generally involves the inherent uncertainties
of small difference of large numbers. A detailed compilation of available thermochemical data
for the various uranium oxide, oxychloride, and chloride compounds is presented in the Appendix.

Evaluation of this body of data leads to the following general findings:

 
® At a given valence state, the oxychlorides are more stable than the chlorides.
® At a given valence state, the oxides are more stable than the chlorides.

e All additions of chlorine to oxides or oxychlorides of lower valence [less than U(VI)] are
favorable to give oxychlorides of higher valance.

e The oxychlorides can be formed both by direct reaction of chlorine and by reaction of an
oxide with a chloride. |

e  Production of UCI, requires a reducing agent whose oxide product is much more stable than
the chloride; that is, it does not react with uranium chlorides. Carbon and carbon monoxide
meet this criteria. Hydrogen does not and the oxide (water) reacts with uranium chlorides
to produce HCL
Figure 1 presents a summary of the expected thermochemistry of the uranium oxide,

oxychloride, and chloride compounds at various uranium valence states. The phase relationships

between tetravalent uranium oxide and chloride are shown in Fig. 2.2 The phase diagram shows
that there are three stable compounds over the entire range of composition—UCl,, UOC],, and

UO,. There is a eutectic reaction between UCI, and the intermediate compounds, UOCI,(UCl,

+ 50 mol % UO,). The melting point of pure UC], is 590°C. A minimum melting point of

545°C occurs at the eutectic composition of UCl, + 6.9 mol % UO,. A maximum solubility of

about 13 mol % UO, in molten UC], is reported at 810°C. At temperatures from 810 to 855°C

UCl, vapor is in equilibrium with solid UOCl,. UOCI, decomposes at 855°C. At higher

temperatures, vapor and solid UO, are in equilibrium. The reasonably high solubility of UQ, in

molten UC], over the temperature range of 545 to 810°C suggests a desirable precondition for
achieving rapid rates of reaction between chlorine, carbon/carbon monoxide, and UG, dissolved
in molten UCl,.

The present investigations were carried out to characterize the production of UCI, by a
direct carbochlorination of uranium oxides in a molten salt medium and to identify the optimum
conditions for accomplishing the conversion in the most economic fashion. Variables that have
been considered include the physical and chemical characteristics of the oxide feed material, the
use of carbon versus carbon monoxide as a reductant, the physical characteristics of carbon

reductants, the effects of feed rates, and the effect of temperature.

 

 
 

ORNL DWG 891A-10

VALUES IN PARENTHESES: MINUS FREE ENERGY OF REACTION, 900 K,
kJ/equiv MULTIPLIER OUTSIDE PARENTHESES: EQUIVALENTS/REACTION,

 

 

  
 

 

 

 

URANIUM 0/U, ATOM/ATOM
VALENCE
0 1 2 3
u(o) U U U
+3/,Cl, +1/20,+1/2Cl,
3(233) 3(260)
+1/202—C|2 +0 +8/0
______> 6
u(in) UCI3\ 5(20) UO({ 4(233) 195(187)
+'%4Ci, +C0O-CO, +4Cl, +C0O-CO,
95 —2(48) 120 -2(8)
+1/202—C|2 +1/202-"C|2 '
_—.....’
+ 15l + 140l +15cl +2/3C0-%/3C0,
14 100, 0. -\ %(52)
\
+Y20,-Cly +120,-Cl>
_—_> ___>
u(v)  UCls— a0 UOCls 5 U0 Cl +C0—CO;
2(71)
+1/4C[z
1, (100)
+1/2C| +C0-CO, +1/2C|2 + V50, —-3/4Cl '
o -2(11) 20 1,[(U0, ) ,Cl4] ——%63%—2»’/3[0308]
+"4Cly +'/60 4
'/,(110) —%4(8)
U(Vl) +1/202—C12 +V202—C|2 +1/202—C|2
—_— —_— —_—

Fig. 1. Conversion reactions for U-O-Cl compounds.

 
 

 

 

 

 

 

 

| Wt %
99 97 95 90 85 .
TPl Py 1 ol P |
900 ) Vopor + U0, —
800 810° _|
©00 —
\
-
S00H -
|
|
400H —
|
300 +_ UC|4 ss + UOCIZ —
I
|
2001 =
100 S| -
=
ol 1 o104 ovor o1 ot
| 19 i S
UCIa 2 6 o 8 O U0, —
Mol %

Fig. 2. Phase diagram for UCl,-UO,.?

 

 
2. EXPERIMENTAL APPARATUS AND PROCEDURES

The experimental system was assembled from small flowmeters, 0.25-in. OD metal tubing
and fittings, and quartz or borosilicate glass components fabricated by the Oak Ridge National
Laboratory (ORNL) glass shop. For hot chlorine gas, the materials of construction were

borosilicate glass for up to 450°C and quartz for the chlorination reactor up to 900°C. For
chlorine gas at room temperature, Monel, Teflon, and Viton rubber were also used with some

stainless steel for short time periods. Apparatus after the Cu-foil trap for Cl, was mainly
stainless steel and plastic.

A diagram of the apparatus as used for Tests 5 to 18 is shown in Fig. 3 The initial
arrangements as used for Tests 1 to 4 were described with the preliminary results.> The
quartz reactor was 4-cm 1D, 69-cm long, with a closed bottom and a 65/40 ball-joint socket
at the top end (Fig. 4). The mating half of the ball joint had the fittings for all connections,
including a gas sparger and the gas outlet. The initial charge was loaded into a quartz crucible
of 3.2-cm ID, which was lowered on to a small pad of quartz wool on the reactor bottom.
The initial reactor was fabricated with a quartz jacket for cooling from 38 to 53 cm above the
bottom end. A simple borosilicate glass sleeve with "O" rings was used for air cooling after
the initial unit. The gas sparger and the thermowell or UO, feed line were installed through
the reactor cap using slip-fittings ("O" rings or Viton rubber sleeves) to allow length
adjustments.

The apparatus and procedures allowed three different material balances for each test.
The weight balances were probably the most accurate but gave only the overall run material

balances. The weight measurements were:
1. The weight loss by a CuO reactor indicated the oxygen used to oxidize CO to CO.,.

2. The weight gain in a final Ascarite absorber showed the CO, that was produced from
CO.

3. The weight gain for the first Ascarite absorber showed the CO, in the gas leaving the
chlorination reactor.

4. ‘The weight gain by the Cu-foil trap showed the Cl, in the gas leaving the chlorination
reactor.

5. The weight gain by all reactor components equals the Cl, reacted plus the solids feed
minus the C or O as CO, or CO, shown by a, b, and c. (Note that these quantities must
allow for whether the oxidation reaction is C to CO,, C to CO, or CO to CO,.)

 

 
 

‘(d] wo-§) 1030831 UONRULIONY) "¢ ‘T

 

 

 

 

Y

1SNVHX3
QOOH

90 L —v086

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

     

 

Y3ILINONYNA
dILIAN
183t L
] 1w _
¥ )
o 3
2
v
| N
1] :
n
4
- [3ovnanid]
704 N VUI
’ . i -
o]

 

SHILIAMOTS SSYAN 94 0oL 14
SYALINVLIOY 9¥ Ol 1Y

OMa INYO

 

 

 

 

 

 

 

 

xr
e——

o N

02

 

 

 

 

 

 

 

 
 

 

'8-SIN 191JE PIACWIAL SE 1070831 JO ydesSoroyq p Sy

 

 
The second material balances were from gas flow rates times concentrations. The

concentrations and flows were:

NN R WD

100% N, for diluent gas feed,

100% N, for wet-test meter flow out,

100% Cl, for Cl, feed,

100% CO for CO feed,

in-line CO, measurement for gas out of the Cu-foil trap for Cl,,
in-line CO measurement for gas out of the first Ascarite absorber, and
the N, content of the gas out of the first Ascarite is 1 minus CO.

The third, and generally least accurate material balances, are from differences in flow

rates. These differences are:

el

reactor out minus Cu-foil trap out is the Cl, that leaves the chlorination reactor.
Cu-foil trap out minus the first Ascarite out shows the CO, absorbed.

the first Ascarite out minus the wet-test meter shows the CO oxidized to CO, and
absorbed on the final Ascarite.

the Cl, feed, plus the N, feed, plus the CO feed, plus CO, or CO from C in the charge,
minus the reactor out indicates the Cl, reacted with the charge.

The results found in the literature provide little information for selection between the

chlorination process alternates. The reducing feed when using Cl, might be:

P

massive carbon or graphite blocks as reported,

carbon particles or powder,

carbon particles or powder mixed with uranium oxide powder and compacted, or
CO gas.

Any of the final three alternatives appear better than the massive blocks with respect to

the reactivity, cost, and ease of replacement when consumed. Further, the reaction medium

might be predominantly:

1. inert, low melting chloride salts,

2. uranium chlorides,

3. a fixed bed of uranium oxide-carbon granules or chunks, or
4. a fluidized bed of uranium oxide and carbon solids.

The phase diagram (Fig. 2) for UO,-UCI, shows formation of UOC], with all liquid for

up to 7 mol % UQ, at the melting point of UCl,. This solubility of UO, in molten UdCl,

appears to be a desirable condition for easy and rapid chlorination and reduction reactions.

 

 

 
10

The chlorination condition of greatest interest for the AVLIS feed process was to react
UQ, and Cl, in a molten sait medium. Chlorination studies were planned for these conditions,
and the selection of other conditions proceeded as follows:

1. The first tests were with a block of carbon for diffusers as favorably reported by
Canning* and Gibson.’

2. After good reaction of Cl, and formation of CO, were demonstrated with the carbon
diffusers, CO was tested as a more practical reducing agent.

3. After results with CO showed that the reduction reactions were much slower than the
chlorination reactions, carbon powder was used to determine the effects of this reducing agent
as compared to CO.

4. Since high UQO, concentrations resulted in sparger plugging problems and low UQO,
concentrations gave poor utilizations of Cl,, the experimental apparatus was modified to allow
UO, feed while chlorination was in progress.

5. Tests were made with ball-milled UQ, powder and with UQO,-carbon black spheres for
comparison with the UQO, spheres and the petroleum coke first tested.

6. Comparison tests were made with UQO, spheres as feed and with a fixed-bed of UO,-
carbon black spheres without any molten salt.

7. The experimental apparatus was then modified to use a larger reactor with a bottom
condenser.

The first four experimental tests were previously reported.’ After eighteen tests

(including the initial four) in a small apparatus, the equipment was modified to provide a

larger reactor and a more useful condensation arrangement for product vapors.

3. RESULTS

Eighteen experimental tests were made in a quartz reactor of 4-cm ID and were directed
toward the molten salt chlorination of uranium oxide. Three tests were not completed as
planned because of failure of reactor components. One test was to check the procedures and
material balances without chlorination. The remaining fourteen gave useful chlorination

results. The test conditions are summarized as a tabulation (Table 1).

 
1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 2o 0 8L0 8t°0 8L'0 £8°0 wo 9¢°0 o v, 06°1.2-60 s
0 670 0 Lo 80 8L°0 80 ¥00 $T0 O olL 06-5¢-60 \4)
0] s810 0 0L0 LLO 8L0 Tl 000 620 o 089 06-L0-60 tl
089
0 Lo 0 +9°0 LLO 8L'0 0Tl 00 y1°0 ) L9 06-¥0-60 7l
069
0| 9500 0 A 0 0 L90 0 70 o SL9 06-TC-80 Dl
0 0 0 0 0 0 L90 0 Yo o $t9 06°12-80 il
0 0 0 0 ¢ 0 L90 0 yeo JUON $t9 06-0T-80 Vil
089
0 0 0 Al 0 0 LSO 200 0 ) <o 06-£1-80 0l
0 0 0 t¥'0 0 0 L90 910 6C'0 %) S 06-10-80 6
089
0 0 $50 60 0 0 0 810 LT0 0D 9 06-¥0-90 8
0 0 90 950 €50 Y50 0 o 0 0o §49 06-$1-50 L
0 0 70 £1'0 0 0 0 0 0 1000 059 06-01-50 9
0 0 0 0 0 0 0 0 0 0D 059 06-80-50 S
0 0 1£°0 $E0 0 0 0 1o 21°0 00 LY 4 06-12-t0 v
. 06L 06-T2-10
0 0 € B 0 0 0 1o 800 0D 059 68-11-T1 £
0 0 0 LYo 650 90 | 4 ¥0'0 0 1puyd 00L 68-50-0! <
anyde1n
0 0 0 910 0 9%0 e 900 9100 Japunfo 058 68-21-60 1
aydeln
1011
o| ‘on 0D % JoppeN | 108N D ‘on "on wode (.) soNp 'oN
Jupnpoy ainesadway 1S9L 159 SN
(jow) aaperoduwsa) e padyg (jows) 283ey2 femug 20 1In,]

 

 

 

 

 

 

 

SUONIPUOD pue s1ojowered )s0) UonRULIO) °T 9jqe],

 

 
12

 

"Pa3J U JIB|q uoqled ‘adieyd Ul 9X0D WIND(0NI],
"}orjq UOQIED),
2400 WNDJ0A ],
"PAINSEINU JON,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 0 0 Y0 £0 £0 L7 90 v'Z e} 069 16-11-90 1€
0| to1 0 182 £0 £0 LT 10 02 D sZL 16-50-90 0€¢
0 0 80 69'0 £0 £0 0l ££°0 61 IS 8LL 16-62-S0 6T
o t61 0 op'p £0 £0 't o> 0z D 8LL 16-¥1-S0 8
0 0 0 990 £0 £0 'l 0£0 8l D 8LL 16°10°50 7z
o| sol 0 L0°E £0 £0 862 020 ¥l D vLL 16-¥2-90 9
szo | 90 0 L6’ £0 £0 002 $1°0 71~ 2 LLL 16-€0-$0 T
LLL
| 0 8¢ €0 £0 002 sI'0 960 D 8EL 16-92-£0 e
cLlom 0 Lt 120 120 e $1'0 gl e 1£L 16-91-10 €2
SIL
seo | 1L0 0 $T 120 120 Ly $T'0 Lt 9 ¥69 16-€0-10 w
669
0{ 90 0 I't 0 0 (A 50'0 £1 O LL9 06-81-21 12
o wo 0 99°0 0 0 Sy $I°0 'l O 569 06-90-C1 0z
0 0 0 0 0 0 0 0 0 QUON $L9 06-82-11 6l
YASNIANOD WOLLOE “HOLDVHY MHDUVT OL AHONVHD WALSAS HOLOVAY
0 0 0 0L'0 0 0 vl PE'0 0 2D 00L 06-90-11 81
o| 1o 0 SE0 801°0 SZI'0 60 700 860 S 089 06-0¢-01 L1
$L9
€1 | 1€0 0 8L'0 801°0 STI'0 0 +0°0 ST0 D soL 06-91-01 91
1Y
5| on ) 10 0 e | GDIN D ‘on DN ade .) sep 'ON
Supapay amnjeradwy 199, 1591 SW
(low) ameradway 1e poag (jow) 231eyd jemu 0RUIN
(ponuguoa)
SUONIPUOS pue s1ojowered Js9) uoneUuloD I JqEL

 

 
13

The progress of the chlorinations was indicated by the measurement of gas flow rates and
concentrations during the tests. The overall or average results are shown by the material
balances from reactor and trap weights after cool down to room temperature. Some results
for the useful chlorination tests are tabulated (Table 2). Additional details by test numbers
are in the Appendix. Each individual result can be interpreted in a number of ways since the
overall process reactions result from a number of multiple step reactions.

Conclusions for important process parameters are discussed as separate sections. In
general, a specific conclusion cannot be proven by one test result. Instead, the test results
(Table 2 and the Appendix), along with thermochemical data, must be considered as a whole
to justify the conclusions. Rapid reaction rates and removal of oxygen as CO or CO, were
demonstrated in the first four experiments as previously reported.” The results of these initial
tests are included in the tabulations, but the details in the initial report® are not repeated.

The test conditions (Table 1), and the brief tabulation of results (Table 2) do not clearly
show how the process conditions, apparatus, and procedures were changed between
experiments. Some of the most important changes in process conditions and the results are
listed in Table 3. Important changes in apparatus and procedures, and the corresponding
results are in Table 4. The material balances tabulated for chlorine (Table 5) and oxygen and
carbon (Table 6) are averaged values with more weight to the more accurate mass

measurements.

3.1 REACTIONS OF CHLORINE

All of the chlorination studies were done with uranium oxides and the reducing agent in
the reactor at temperature when the chlorine flow was started. All tests show that the initial
reactions of chlorine go very well without any significant concentration of chlorine in the exit
gases. This was true when the initial charge contained melts of UCl,, MgCl,-NaCl or MgCl,-
LiCl, UCl,-MgCl,-NaCl], or a fixed bed of UO,-C particles. The reaction rates for chlorine
can be much higher than the rates of reduction indicated by CO or CO, flows. This result,
thermochemical data, and some melt analyses indicate that the chlorine reacts by "oxidizing"
U(IV) to higher valances; that is, the chlorine adds to the U(IV) compound to give U(vl)
or perhaps U(V) compounds. Reaction of Cl, with UO, or oxychlorides is more favorable
than reaction with UCl, to give UCL or UCl,. After U(IV) oxides or oxychlorides are

depleted in concentration, UC, is reacted to give UCl; or UClI; that are much more volatile.

 

 

 
14

Table 2. Chlorination test results

 

Overall/average Cl, reacted
MS Furnace run result® (%)  UO, feed
test temp. Cl,feed O,in UO, atom Cl

 

No. (°0) reacted evolved mol UQ, Principal conclusions and results
1 850 ~50 ND? ~3.0 UO,+Cl, + graphite - CO,+UCl,+UO,ClL.
2 700 ~50 ND small  Most of Cl, reacted with Monel sparge tube.
3 650 ND ND small UQ;+CO - UO,+CO,. Severe plugging of
790 ND ND ND  sparger (perhaps UOCI,). Nearly all of uranium

volatilized out of crucible.

4 625 42 40 2.8  Consistent material balances, gas flow rates
and gas concentrations. Condensed solids
were predominantly UCl, while charge was
half UCl, and half oxychlorides.

5 650 ~ - — Quartz reactor broken.
6 650 0 — 0 Operator qualification completed.
7 655 38 <10 23  UO,+CL+CO - UOLCL+CO with little

removal of O as CO, Apparently UCl, is
necessary for reduction by CO.

g 645 30 55 28  The results of MS-4 were duplicated with good
- 680 material balances. The rate of CO, evoluation
showed little variation with temperature, Cl,
rate, and sparger immersion. Complete plug

by condensed solids.
9A 645 40 70 2.5  The C gave CO, without any detectable CO.
9B 645 0 0 Condensed solids plug of same appearance as

MS-8. Leaks at the in-reactor sparger
coupling resulted in low CL, utilizations.

10 645 36 >100 42  Condensed solids plug of same appearance
as 680MS-8 and MS-9. Total material balalnce
for MS-9 and MS-10 indicates complete
conversion of UO, to UCI,.

11A 635 No condensed UCI, without gas sparge.

 
15

Table 2. Chlorination test results
(continued)

 

 

 

Overall/average Cl, reacted
MS Furnace ___run result® (%) UO, feed
test temp. Cl,feed O,in UO, atom Cl
No. (°CO) reacted evolved mol UO, Principal conclusions and results

11B 635 Low UC], volatility in agreement with UCI, vapor
pressure without Cl,.

11¢ 635 40 >80  ~5.0 The feed of uranium oxide spheres into the UClL,-C

690 with Cl, gives an immediate evolution of CO, that
peaks in a few minutes.

12 635 65 115 4.6 The rates of CO, evolution and the utilization of

680 Cl, increased as the oxygen inventory was increased
by successive additions of uranium oxides. A 50%
increase in Cl, rate gave a 20% increase in CO,.
A 45°C higher temperature gave 60 to 80%
increases in CO,.

13 680 60 100 4.0 At 680°C, some point utilizations of Cl, were
100% and average values for 30 to 60 min were
80%.

14 710 92 102 4.0 Excellent Cl, utilization and conversion without
excessive volatility of uranium.

15 745 63 106 3.9 Same type of plug as observed for 100% UCI, in
MS-8, -9, -10, and -11.

16 705 92 115 42 Flow rates showed =99% utilization of Cl, until end

675 of test when oxides were depleted. At 705°C,
about 10% of the oxygen evolution was as CO.
This decreased to a low value at 675°C. Carbon
black is more reactive than coke.

17 680 65 145 3.8 UO, feed gives more complex reactions than UO,.
Uranium is more volatile with UO, feed. Cl,
utilization is lower.

18 700 88 120 3.8 UO,-carbon black gel spheres react well without
molten salt. Typical dark plug of condensed solids
stopped run while CO, rate was still high.

Reactor System Changed To Larger Reactor; Bottom Condenser
19 675 Mechanical and thermal performance of new

components are good.

 

 

 
16

Table 2. Chlorination test results
(continued)

 

Overall/average Cl, reacted
MS Furnace ___run result® (%) UO, feed
test temp. Cl,feed O,in UO, atom Ci
No. (°C) reacted evolved  mol UQO, Principal conclusions and results

 

20 695 &5 117 4.9 About 0.17 mol condensed U collected as powder.
Deposits on quartz wall above furnace and inside
insulation below furnace.

21 677 94 107 5.0 0.77 mol condensed U collected as powder.
699 Condensed U on vessel walls was about 0.59 mol

or ~40% of volatilized U. Good operation except
for two feed-line (UO,) plugs.

22 694 82 120 4.4 Cl, utilization near 100% for 1 h. When Cl,

715 utilization decreased, addition of 2 g C-black (48 g
C-core in charge) doubled CO, evolution. N,
purge eliminated UQO, feed plugs. Different UO,
feeds showed same reaction rate.

23 731 72 75 34 Quartz crucible cracked — probably during heatup.
A quartz baffle above crucible prevented UCI,
deposits in top of reactor.  Other results
compromised by cracked crucible.

24 138 95 130 43 Reduction rate equaled chlorination rate.

777 CO, rate = 0.5 Cl, rate = UO, feed rate; 141 g in
product jar. Rates of reaction determined by Cl,
feed rate without effects from temperature or the
amounts of UO, or C inventory.

25 777 92 140 4.5 The MS-24 results confirmed with doubled UO,
(0.60 mol/h) and Cl, (1.25 mol/h) feed rates.
Condenser cross section plugged by dense solids.

26 774 92 120 4.4 The MS-24 and MS-25 results confirmed at higher
UO, and Cl, feed rates; 329 g in product jar or 67
mol % of UO, feed.

27 718 95 160 4.2 Material specimens exposed for 6 h. Cl, utilization
and percentage collection of product solids about
same at the low rate and five times higher rate.

28 718 93 120 4.3 The MS-24 to MS-26 results confirmed at flow
rates up to 2.8 mol/h Cl, feed. Continuous feed
for UO, demonstrated, but plugs in feed line were
troublesome. Reactor cross section plugged above
condenser.

 
17

Table 2. Chlorination test results
(continued)

 

Overall/average Cl, reacted
MS Furnace __ run result® (%) UO, feed
test temp. Cl,feed O,in UO, atom Cl
No. (°C) reacted evolved  mol UO, Principal conclusions and results

 

29 778 98 145 4.2 Material specimens exposed for 6 h with CO in the
sparger gas. Cl, utilization and product collection
results of MS-27 were confirmed. Thermowell in
melt shows salt temperatures of about 730°C.

30 725 97 125 4.4 Good Cl, utilization at lower temperatures, salt
temperatures of about 650°C. High N, flow to
sparger gave high U vaporations at lower melt
temperatures; 73% of condensed U in product jar.

31 690 97 110 3.4 Short period of Cl, flow did not complete
conversation of UO,. Cl, utilization good at melt

temperature of 645°C. Dip samplers demonstrated
removal of samples of melt.

 

®ND - not determined (measured).

 

 

 
 

 

"AnieIoA
n 19ySy pue uoneznn %D Jamo] Juipnput
$190]J0 PRIUBMUR [RISAS ‘UONIBal XIidiwoo IO

109132 1231¢]
s1 awn dwes 1e uonppe [DeN-YIDFW Ing (Amejoa
(1 Taso] Ajqeqoid) YD Jo suoneziin 191 Yony

"Do01L 10 $89
1e sgnyd 9jqonis ou ‘) Jo ANIRIOA JoMO] YININ

18

-aInssaxd odea ‘1DN
UM JUaRITe Ul ‘IS ST [] JO UOHBZNEIOA

‘11 JO uonez|nejoa ON

‘uaf8£xo Jo _m.onE

areidwod 20w ‘suoneznn 4y (10ysiy) Jenag
‘suonezZInn

4D pood nq ‘0D 10 FQD AGrINIAP ON
"sonel

onfon udy e 18eds Jo Suiddnyd v1asag
‘uonnjoas Q) Jo selel Ieysiy yony

‘sanesadwa) Jamof 18 10D Jo uonnjoaq

Auo L1

[A!

€T TT
L1oel

Aluo g11

Auo V11
6

Aluo ¢
Auo T

oh oD

t

‘on Jo 20eid ut “ON JO pIdd

voneiado Suunp 0N Jo paag

"o J0J WANIp B S8 213093 [DeN-IDIN

(%D oN) #81eds *N yim *'1on

a81eds sed noyim DN

02 Jo 20eid ur sajonted 9302 WN|ONdJ

"o noynm Jaw [DeN-08W 10 DITIDSN

(1DEN-IDIT-4D3 I ou)
[es apuIofyd Ajuo ay se PN

Jopunks anydead pauuy Jo aoerd ui JueIPNPal 0D

 

23ueyo woly nsay

a8ueyo i 3893 18T

a8uey)

 

§}jnsoJ pue sUONIpuod ssaoold ul saguey)

"¢ S[qE],

 
19

Table 4. Changes in apparatus and procedures

 

Results from change

 

First test
Change with change
Cu foil trap for Cl, in place of 3
thiosulfate scrubbers.
In-line measurement of CO, and 3
CO concentrations.
Monel sparger for Cl, feed. 2 only
Open end to perforated sparger; 4
perforated sparger to open end. 10
Shop calibrations of flow meters. 9
Long crucible with top extending 9
above insulation.
Long quartz sparger without coupling 10
in reactor.
Feed of UQ, particles during 11C
chlorination.
Larger reactor and bottom condenser. 19

Good measurement of amount of
Cl, trapped; better operation of Ascarite
traps for CO,.

Real-time indications of the rates of reaction.

Cl, reacted with Monel, then bypassed
without reaction.

Not imtl))ortant to plugging; a 45° cut open
end is best.

Much better accuracy for Cl,, CO, CO
rates from flow differences; better material
balances from flow rates and concen-
trations, However, calibrations change
with exposure to Cl,.

Allows easy removal of condensed solids or
return to charge by melting.

Eliminated leaks and coupling failures as
cause of low Cl, utilizations.

Much better operation with respect to Cl,
utilization, sparger plugging, and reduced
volatility of U.

60% of condensed U as powder on the
bottom.

 

 

 

 
20

 

"UOTIZNUIOUO0D SN MO sed soredipul D4,
"SO1B1 MO[J Bl $IOUDIDJJIP SIIBINPUI (Qx,
*SIUILIINSEINU JYdl1oMm SOIBIIPUI IM,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

L1 £L L9 w 89T 87 €7 L0T 91 L0 SL'O €T
T 98 8 8 6£T 897 Wt 1€ 86’1 LEO vr'0 w
vz 98 6 89'C 897 0€T 8€0 L1'0 12
6 80°¢ 787
LT 18 98 990 89°0 $S'0 £1°0 600 0z
gl 8 L8 98 oL0 090 SL'0 £5°0 90 L0'0 960°0 81
9] 0s 89 69 9¢'0 9¢'0 SE0 810 V20 810 1o LY
1T ¥6 6 6 9L'0 8L0 080 €L°0 vL'0 8¥0°0 7900 91
7T ) £9 86 wo LLO 080 €50 0S°0 020 0£'0 Sl
A/ $6 16 16 1L°0 8L0 Lo vL'O 90 00 790°0 ¥1
02 £9 SS 9¢ 1.0 1L0 690 S0 8€°0 LT0 10 €1
¥ €L £9 9 ¥9'0 L90 £9°0 6¥0 or'o 810 £2°0 Al
LT oy Sy o¢ £€°0 0£0 8¢0 10 L1'0 810 120 o1l
97 ve 9¢ 8¢ LYo o SY'0 S10 91°0 620 620 V0!I
01 6¢ 8¢ vt £°0 9’0 or'o 600 s1°0 v1°0 $T0 6
A 61 0g €y 901 6L'0 98°0 0z 92'0 650 09°0 8
[~ pI 8¢ 8t 950 050 950 L0'0 170 €70 SE'0 L
160 poInsEdW JON | SE 137 $€0 | pomseawoN | 1€0 S60°0 10 $T0 070 v
D: pa3) pue ad M a4 oM
(10wy/j0w) dd m M den oy | DO podg ad WM 101083y | 10eoy | denn) den n) ‘ON
panedl *oNfo (%) wonezpnn ' (tow) ¥1D 110, (1ow) 10npord D o

 

 

 

 

 

QULIO[YO :SPOUE[RQ [ELIDJBW 1$9) UONRULIO[YD °C d[qe],

 

 
 

21

"§91R1 MO[J Ul SIOUIISJIP soredipul (d,
“SIUOWIINSEIW 1YTIom SIIBDIPUT 1M
“UONBIIUIOUOD SOW mO[) sed $a1ed1put D,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8v0 SL 180 L60 $60 0 SO0 <00 200 0 €C
§S°0 0c1 171 STl 60’1 0 0 <00 0 0 [é
poInsesul
10 001 €01 88°0 £0'1 0 00 10N 100> 0 1Z
wo ril LT0 yZ0 ¥eo0 0 0 0 100> 0 474
LSO 0ct sy S0 8¢0 S0'0 600 900 L00 0 .wfi
1 ori1 LT0 12°0 L0 00> 0 0 100> 0 Ll
sS0 0zl 8t’0 Iv°0 144" 90°0 00 00 €00 0 91
€50 o1l 070 €20 820 0 0 0 100 0 ST
LvO 001 LT0 £€0 ye0 painseail JON 0 0 0 0 14!
€S0 001 910 S1°0 170 100> 0 0 0 0 tl
L0 ort 970 ¥20 1€°0 palnseaul JON 0 0 100 0 Cl1
80 00Z~ 90°0 <10 ¢10 0 0 0 0 0 11
6’0 00C~ 110 1o 10 0 0 0 0 0 Vo1
90 oL LOO 600 010 palnseaul 10N 0 0 0 0 6
80 ss a0 €20 070 a0 S0 LE0 LE0 6v°0 8
1'0> o1~ 0~ 100 00 950 L0 ¥9°0 L90 680 L
80 )4 ¥80°0 LLOO 980°0 poInseawt JON veo o 120 £C0 v
(jowy/[our) no JIM IM M
poedI 49 uodkxo *ory | G WOl | D WoId | °sqe woid -] WwoIg S wold | 'sqewoly | Ond wolj (jour) ‘ON
Ano Q) JO 120194 D 4q 1S9,
(four) 10 QD (four) 1030831 JO MO 0D P39} 0D

 

 

 

 

 

 

uoFAxo pue UoqIed :$OUR[Eq [RIIDIEW )53 UOHEUMIOYD ‘9 dJqBL

 

 

 
 

22

than UCl,. This operating condition results in large losses of Cl, to the off-gas. Either the
completeness of reaction of Cl, is limited by a less favorable equilibrium or the UCls or UCl
decomposes as the vapors cool to give condensed UCI, and Cl,. Operation with UO; as the feed
instead of UO, also gave higher volatilities of uranium and larger losses of Cl,. This result also

indicates that U(IV) oxides or oxychlorides are very helpful to high utilizations of chlorine.

3.2 UTILIZATION OF CHLORINE

High utilization of chlorine required a good inventory of U(IV) oxides and oxychlorides in
the reactor charge. The initially charged UO, supplied this inventory so that chlorine utilizations
were always high when the chlorine feed was started. Continued high utilizations with complete
chlorination required the reduction of U(VI) back to U(IV) at rates that prevented depletion of
U(IV). Continued high utilizations were demonstrated using carbon as the reductant and reactor
temperatures of =2670°C.

The minimum conditions to assure high chlorine utilizations for steady-state operation were
not clearly determined. The following conditions gave poor chlorine utilizations of <70% (i.e.,
more than 30% of the feed chlorine was trapped from the exit gas (see Table 5).

1. All tests with CO as the reductant. (The best combination of higher temperatures and an
optimum continuous feed of UO, might give higher chlorine utilization using CO.)

2. All tests with reactor temperatures near 630°C.
3. All operation with low concentrations of oxygen in the reactor charge. The limit on oxygen

concentration depends on the Cl, feed rate and the concentration and reactivity of the

carbon. Melts as low as 2 mol % oxides—98 mol % chloride can give good chiorine

utilizations, but there is not enough information to determine limits. Because of this effect,
operation at conditions intended to complete the conversion of UO, to UC], gave higher
chlorine losses to the off-gas.

When chlorine utilizations were good, the Cl, removed in the Cu trap was only a small
percentage of the total gas flow. The calibrations of the two flow meters changed continually,
and calculations of flow differences using separate calibrations of the two meters did not give
useful measurements of the small Cl, losses. Finally, the whole run Cl, losses measured by the
Cu trap weight gain were used to calculate meter factors that match the whole run flow
differences to the Cu trap result. These meter factors gave much more consistent results for the

short period Cl, losses. Some results from the large reactor tests using carbon black (all melt

depths of 7 to 10 cm) show Cl, losses of 2 to 4% for a range of Cl, feed rates (Table 7).

 
23

Table 7. Chlorine losses versus Cl, feed rates using carbon black at ~730°C.

 

 

Test Cl, feed Cl, losses

period (cm®/min) (%)
27 43 2.6
24A 230 1.8
24B 230 4.3
25A 460 2.9
25B 460 33
26A 635 2.2
26B 770 4.3
28A 622 3.3
28B 838 4.0
28C 842 34
28D 1032 4.5
28E 1026 6.8

 

The higher losses near the end of test MS-28 may have resulted from an unintended
depletion of the UQ, inventory. After the UO, feed was ended, the appearance of high Cl,
losses and the sharp decrease in CO, concentration indicated only 2 to 3 min (12 to 18 g of
UO,) before the inventory was grossly depleted. |

These results show little variation in chlorine losses for a wide range of UO, and Cl, feed
rates. Using carbon black at 730°C allowed high rates of reaction, but the CI, losses remained

=>2% at the most favorable conditions.

3.3 EFFECTS OF URANIUM OXIDE PROPERTIES

The feeds to an AVLIS plant will be uranium ore concentrates from refineries. Since
a representative sample or a specification of typical properties was not available, the
chlorination tests were made with several uranium oxides available at ORNL. Some
measurements for these materials are in Table 8.

Results of chlorination tests indicated that the chlorination reactions are simpler and
operation is better if the feed is predominantly UO, instead of higher oxides. The U(IV) is

favorable to formation of UCI, while U(VI) allows excessive vaporizations of uranium as UCl.

 

 

 
 

24

Table 8. Properties of uranium oxide, UO,-C, and carbon feed solids

 

 

Surface Bulk Particle
area density size

Nominal composition Description (m%g) (g/em?) (um)
UQ, Ball-milled powder 0.102 4.90 20—150°
UoQ, UOQ, gel spheres in H, to 740°C 7.37 1.3 300500
UO,-C UO,-C gel sphere in Ar to 740°C  30.52 0.80 400—800
C/U = 4.2 atom/atom
C Petroleum coke 1.34 1.15 50—400°
C C-black for UO,-C spheres 96.0° 0.2° 0.03"
C Compacted C-black granules c 0.68 100—-1000°

 

*Some finer particles.
*Manufacturer’s data.
“Probably ~ 100 m%g and 0.03 xm true basic particle size.

This effect has been reported for chlorinations using CCl,, COCl, and other chlorination

agents. The additions of uranium oxide feeds generally gave bursts of gas pressure that were
largest for UQ,, smaller for U;O4, and smallest for feed that was nearly UO,. Most of these
chlorination tests have been with UO, feed even though the usual uranium ore concentrates
are UO,. Test MS-17 was made using a feed of UO, spheres to the UCl,-carbon black charge
remaining after test MS-16. The test was carried out to observe the UO;-melt reactions and
the chlorination reactions separately by adding the UO; without Cl, feed, and then starting
the Cl, after the UO;-melt reactions approached completion. The simplest and best result
would be the reaction of UO, and carbon black to give UO,, and then the same chlorination
behavior after Cl, flow was started as for UO, feed. However, the reactions observed for UO,
are much more complicated and less desirable than the simple reactions just mentioned. It
appears the UQ; also reacts with UC], to form oxychlorides and that the U(VI) feed yields
more UCI, than U(IV) feed. It is not certain exactly which reactions occur, but the observed

results include the following:

 
25

1. The amount of CO, evolved before the start of Cl, flow was <15% of the total
oxygen added as UO; (or about 40% of the oxygen for reduction to UQO,).

2. The amount of CO, evolved after the start of Cl, feed was much more than that for
UO, and confirms that more than 85% of the oxygen introduced as UO; remains in the melt
without reacting with the carbon until Cl, is fed.

3. The chlorine utilizations were only in the 50 to 70% range, while.chlorine utilizations
for the same conditions with UO, would have been =90%.

4. A plug of condensed uranium chlorides plugged the crucible cross section at the end
of the test. This amount of condensed uranium chlorides was not expected based on results
with UO, feed at similar conditions.

The chlorination reactions did not show any dependence on the physical properties of
the uranium oxide feeds. The reactions of the uranium oxides with UCIl, were rapid so that
the availability of oxychlorides for oxidation by Cl, and reduction by C or CO did not vary with
the physical properties of the uranium oxide feed. During test MS-22, batches of the ball-
milled UO, of low-surface area and the uranium oxide gel spheres of high-surface area were
alternated as feeds without any detectable differences in results. For either feed, the effects
of the addition peaked as quickly as the feed addition was completed; both uranium oxides
were available for reaction without any significant delay. The UCl, reacts with UO, to give
UOCI,, while higher oxides probably give mixtures of UOCI, and UO,Cl,.

The carbon and oxygen balances (Table 6) and the CO, collected per mol of Cl, reacted
show consistent effects. The early tests with CO were commonly ended by reactor plugs
before oxygen removal was complete. The extra oxygen in U;0, or UO; as compared to UQO,
was noticeable. Exposures to air during shutdowns resulted in extra oxygen and loss of

chlorine from the reaction of UCl, with water vapor.

The material balances as compared to the amounts of UO, feed commonly showed
CO,/UO, larger than 1 mol/mol, and Cl,/UO, larger than 2 mol/mol. The excesses over the
stoichiometric amounts would be expected from reactions of UCl, with water vapor during
handling or from water, hydrocarbon, or oxygen impurities in the feeds. Any water in the
feeds during chlorination would give both CO, and HCI that would collect on the first Ascarite

trap, in addition to the CO, from chlorination of UQ,.
The effects of other impurities in the uranium oxide or the carbon have not been studied.

Logically, some impurities would accumulate in the chlorination reactor melt. Other impurities

would form volatile chlorides and be transferred with UCI, to the uranium metal product or

transferred to the waste purge streams.

 

 

 
 

26

3.4 REDUCTIONS BY CARBON

Use of carbon as the reducing agent has important advantages over the use of CO. An
excess of carbon remains in the melt ready for later use while an excess of CO separates and
is lost to the exit flow of gases. The excess CO results in a toxic and flammable waste gas.
~The CO can react with excess Cl, to give COCl, (phosgene), which is more toxic than Cl,
alone. Carbon feeds are easily stored and are commercially available in several forms while
a large feed of CO would require special preparation or storage facilities.

The chlorination behavior using C and CO appears to agree with two thermodynamic
concepts. An excess of solid carbon has an activity of one for chemical equilibriums. The CO
is always diluted by other gases and has activities of less than one for atmospheric pressure.
The free energies of formation for CO, and two molecules of CO are equal at 700°C.
Because of the activities mentioned above and kinetic effects, some CO is possible from use

of carbon at temperatures below 700°C.
The chlorination reactions in this study have shown better utilizations of chlorine and

higher rates of reaction with carbon as compared to CO. The best steady-state utilizations of
Cl, were 30 to 40% with CO feed, but Cl, utilizations were 290% for complete tests using

carbon with some steady-state periods near 100%. Temperatures of =>670°C were necessary
for high Cl, utilizations using petroleum coke. The higher reactivity of carbon black was most

clearly demonstrated during test MS-22. When the reactions appeared to be near steady state
with 48 g of petroleum coke in the melt, an additional 2 g of carbon black was added. The
rate of CO, formation doubled and the utilization of Cl, returned to nearly 100%. The peak
in CO, evolution agreed with the amount of carbon black. A later addition of 2 g of
petroleum coke did not give any noticeable change in CO, rate.

Another indication of the more rapid reaction of carbon black as compared to the
petroleum coke is the more rapid decrease in CO, evolution after the Cl, feed is stopped.
With melt temperatures over 700°C and carbon black, the CO, rate decreases almost
immediately and rapidly. With petroleum coke, the CO, evolution may taper off over a 20 or
30 min period. This difference indicates that the petroleum coke results in a much higher
inventory of U(VI) [or U(V)] that reacts with the coke over the 20 to 30 min period.

Rapid formations of CO, during chlorination were demonstrated with three types of
carbon. A petroleum coke was used in the form of free-flowing, granular particles that were

easy and clean to handle and feed. The frozen charge after cool down showed a floating bed

 
27

of salt-wetted coke particles. Carbon black dispersed in UO, gel spheres provided fine carbon
particles of high surface area and very intimate mixing with the UO,. The frozen change after
cool down did not show any separation of carbon in the melt or as dust above the melt (the
UQ, dissolved in UCl,). Test MS-1 was made at 850°C with a finned graphite cylinder as the
source of carbon. The formation of CO, with little CO in spite of the 850°C temperature
indicates a limited availability of carbon for reaction. Graphite shapes are not a practical
carbon source for a production process. Either the petroleum coke or the carbon black mixed
with UQ, appear more practical. The carbon black gives high reaction rates at lower
temperatures, otherwise, the choice probably depends on convenience of use, significance of
impurities, and costs rather than the suitability of the compound as a reactant. A fine, dusty
carbon black powder by itself might cause feeding problems, but carbon black is available as

compacted granules.

3.5 REDUCTIONS BY CARBON MONOXIDE

The use of CO has the advantage of providing a highly pure reactant that is easily
metered and fed. Excess reactant is easily separated from the reactor charge or from
condensed products. However, these advantages are much less important than the high rates
of reduction and the other advantages of carbon. With reduction by CO, utilization of
chlorine was high for a short period only until U(IV) oxychlorides were mostly oxidized to
U(VI). This condition gave much higher volatilities of uranium and poorer utilizations of Cl,.
It cannot be determined whether the chlorine escaped from the melt as Cl, gas or as UCl,,
The result was mostly condensed UCl, and losses of Cl, to the trap, but the UCl; might
decompose to UCl, and Cl, in the condenser. This type of mechanism is discussed more
completely in Sect. 3.6. From 75 to 90% of the CO feed left in the exit gases without reacting
(Table 6). The limitation of CO can be summarized as follows:

Using CO, the rate of reduction is lower, and it is difficult to avoid a charge that

is highly oxidized by the Cl,. This scenario is unfavorable with respect to chlorine

utilization and the high volatility of uranium as UCl,. With C as the reductant and

good (high) concentrations of oxychlorides, the reduction reactions are much faster

than reduction by CO so that the charge has higher concentrations of U(IV). This

situation is favorable to good utilization of Cl,. The lower U(VI) concentrations

using C allow higher temperatures without excessive uranium volatility. The higher

temperatures tend to give higher rates for both the chlorination and reduction
reactions.

 

 

 
 

28

One test to expose materials of construction (MS-29) used both carbon black in the melt
and CO with the Cl, gas feed. There was no detectable reaction of CO; all the reduction was
apparently accomplished by the carbon black. The exit flow of CO did not vary for three Cl,
feed rates (including no Cl, feed).

3.6 VOLATILIZATION AND CONDENSATION OF URANIUM CHLORIDES

During chlorination tests, major fractions and sometimes essentially all of the uranium
is vaporized from the crucible and condensed outside the furnace. Examination of the
condensed solids by X-ray diffraction shows the lines of UCl, only without any known lines
of other uranium compounds. The published data indicate that the volatilities of uranium
oxides and oxychlorides are negligible at the chlorination temperatures. However, the
observed amounts of condensed solids are too large to agree with the vapor pressure of UC],
(Appendix).

The vaporization behavior of UC, in the reactor without chlorine gas is consistent with
the UCI, vapor pressure. There was no detectable condensed uranium from molten UCI,
without a sparge gas (Test MS-11A). This fact indicates that a thermal convection cell is not
a controlling means of vapor transport. With a nitrogen sparge, the amount of condensed
uranium is small in approximate agreement with the vapor pressure of UCl, at the test
temperature (Test MS-11B). With Cl, feed, the amount of condensed uranium is about five
to ten times that calculated from the temperature and saturation of the noncondensable gases
with UC], vapor (test 11C and others) (Table 9).

The uranium condenses outside the reactor furnace and gives deposits of two distinctly
different visual appearances. Both deposits show X-ray diffraction lines for UC], only. The
quartz reactor walls inside the furnace remain transparent and free of deposits throughout the
chlorination tests. After a sparge flow is started, a haze of fine powder deposits on the quartz
walls above the insulation. This deposit becomes opaque immediately above the insulating
blocks in a short time and decreases in thickness to a partly transparent film in the cap. This
type of deposit remains loose and powdery and can be discharged from a tilted reactor by
moderate tapping or jolting. The color of the solids is the greenish-black of UCI, with some
yellow-green tints for the deposits farthest from the furnace.

The other type of condensed solid is distinctly different in properties and appearance.

This type of deposit forms the first 2 in. outside the reactor heated zone. The color is dark

 
 

29

N o3ind ourp paoj ton Juipnpug,
-soanjesndwo) sovUIng oY) URY) JOMO] D,0Z INOQR 210M $2INJEIDUWD)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

291eyn D1LINJ0E 1SOW PIIDPISUCD soouE(eq [eLIEWw 1YTom iim Po1aojos sMol YD pie 40D ‘QD tuonnjoad Q) 10 pud [nun podj i) Jo 1els Wol) smo)j Sen,
0 19°0 ST S0 SLO 00°1 1€L X4
89°0 {(58°0) (SS°P) 00 ov'o S1'Y SIL
890 yeo 08’1 YA oro STl v69 (44
t0'1 669
o1~ 2o 0s'l oga L10 t0'1 LL9 1
870~ ¥80°0 6v°0 910 600 70 <69 0z
S0 €10 - LTl vLO 800 S0 00L 81
SI'0 LO0 . ¥6'0 960 . o _ 9’0 089 Ll
o000~ 600 o'l 50 200 N4 SL9
900~ 600 o'l 50 900 SY'0 SOL 91
<10 17°0 p0'1 90 0£'0 870 SrL S1
SO0~ 890°0 60’1 69°0 900 ye0 01L vl
00~ 200 w0l 50 ot 0z’o 089 tl
100~ 1000~ 60’1 9¢°0 €70 0£0 089
100~ 1000~ 60’1 960 70 0t’0 L9 4!
tl'0 00 90'1 190 €0 10 069
£10 2200 901 19°0 £e'0 (441 $t9 ort
€10~ 0r0'0 £6'0 0S0 670 ¥1'0 089
£1'o~ L70°0 €60 050 LYAY Y10 Sv9 Vo1
€10~ wo 9’0 1o $T0 oro Y9 6
124V €10 tL'l Lo 980 090 089
Pyo !0 L'l Lo 980 090 S¥9 8
9000 S000 Lyl 120 950 oLo $S9 L
00 0o 190 1'0 0zo 1£°0 $79 y
"puG-2UOU
(jouw) (jow) Je10L IN D 0D+ 0D (.) ‘ON 159,
PIsUOpUC) Jodea "N almesadwoy
wniuer) poenoled (jow) 219101 JO N0 SMOY] ooeuIn,g

 

 

 

 

 

 

 

 UOHEZI[IE[OA WNIUEIN PUE SMO[J SeD) "6 9[qeL

 
 

30

black-purple with a mirror surface against the quartz wall and coarse crystals on the inside of
the reactor. These solids can completely plug the cross section to completely block gas flow.
The deposits are dense and strong and fix the gas sparge tube in place so it cannot be
withdrawn. The plugs can be broken into chunks by rodding and removed without breaking
the quartz reactor. Removal of chunky deposits leaves a clean quartz wall while the powdery
deposits of the other type do not.

Both types of deposits are found for all chlorination tests, but their rates of accumulation
differ. A photograph for MS-8 shows both types of deposits and an almost complete
vaporization of uranium compounds out of the crucible and heated zone (Fig. 4). The green-
black powder deposits accumulate at moderate rates that increase with temperature in
reasonable agreement with the vapor pressure of UCl,. The dark, dense solids have highly
variable rates of accumulation. The high rates occur at conditions that give higher losses of
chlorine to the Cu trap in the off-gas cascade. The tests with CO as the reductant were most
commonly ended by plugs of dark, dense deposits that restricted the gas flow before the
intended run plan was completed. Some tests with carbon as the reductant were ended with
only thin layers of the dark deposits on the quartz walls. The thin-layer result occurred only
when the Cl, flow was stopped as soon as the off-gas flow rates indicated increased Cl,
removal in the Cu trap.

The vaporization and condensation behavior is consistent with the following explanation.
The vaporization of the uranium occurs as both UC, and UCl,. With an excess of carbon and
oxychlorides in the charge, the steady-state concentration of U(VI) is low and the amount of
UC] vaporized is small. The chlorination gives an "oxidation" of U(IV) to U(VI). If the
conditions for the reduction reaction are less favorable, the steady-state concentration of
U(VI) and the amount of UCI, vapor increase. Conditions that lower the rate of reduction

and thus increase the vaporization of UCl, are:

1.  CO as the reductant (CO is less effective than carbon);

2. low concentrations of oxychlorides (inadequate UQ, feed) as C or CO cannot reduce
UCl, to U(1V); and

3. lower temperatures as the rates of reduction are more temperature dependent than the
rates of chlorination.

 
31

The vapor pressures of both UCl, and UCl, increase with temperature. Nevertheless,
the dark plugs of condensed solids were formed at some tests below 650°C while other tests
at higher temperatures gave much less dark solids.

The experimental data do not explain how the UC], vapor results in the deposit of dense
UC], solids. The thermochemical data indicate that a large partial pressure of Cl, is required
to keep UC], stable. Therefore, the UCl; might decompose to UCl, and Cl, as a surface
catalyzed reaction. As an alternate explanation, the dark deposits may result from
condensation at higher temperatures and higher UCI, concentrations while the powdery solids
form at lower temperatures and lower UCl, concentrations.

The weight material balances for the large (68-mm-ID) reactor tests have given ten good
measurements of uranium chloride vaporization for a range of conditions. The observed
amounts of condensed solids have been compared with the calculated rates of UCI,
vaporization. These calculations assume a UCI, vapor pressure given by an ideal melt of
nonvolatile carbon solids and molten MgCl, and NaCl with the remainder of the charge as
UCl,. The N, sparge to the crucible and the CO, product are saturated with UCl, vapor at
the melt temperature and composition. The results show agreement with the calculated results
for the effects of temperature (i.e., UCl, vapor pressure), the effects of MgCl,—NaCl as
nonvolatile diluents, and the effects of N, sparge gas flow rates. However, the relative
oxidation-reduction of uranium salts in the melt is also very important. The amounts of
uranium vaporized compared to the calculated amounts of UCl, vapor without consideration
of this factor have been as follows:

a. For no Cl, flows or for very small Cl, flows with good charges of carbon black, the
experimental amounts have been less (80 to 100%) than the calculated amounts.

b. For the high Cl, and UO, feed rates with good charges of carbon black, the
experimental amounts have been 100 to 150% of the caluclated amounts.

¢. For useful Cl, flow rates and petroleum coke in the melt, the experimental amounts
were about 300% of the calculated amounts.

d. Some tests in the small reactor system with CO as the reducing agent showed 500 to
1000% of the calculated amounts.

Chemical analyses of the deposited solids give little additional information. The UC], is

so reactive with water vapor (to form HCI) that sampling and analyses without oxygen

contamination is extremely difficult. Reaction with O, to release Cl, is also possible, but the

 

 

 
 

32

rates are low below 100°C. As previously mentioned, x-ray diffraction shows lines for UCl,
only without any lines for other uranium compounds. The chemical analyses for chlorine, total
uranium, and U(IV) (Appendix B) showed small amounts of U(VI) and more chlorine than
needed for UC],, but not enough to give all UCl, and UCI,. It is believed that the difference
is oxygen from reaction with water vapor during removal and sampling. In summary, the
chemical analyses can be explained by deposits that are mostly UCl, with a small amount of
UCI and a small amount of reaction with water vapor to form oxychlorides before analysis.

Several of the plugs of dark, dense solids were melted and drained to the charge in order
to allow continued chlorination. This operation was only possible when a tall crucible was
used with the top extending above the insulation so the dark solid formed inside the crucible.
The melting was done by either lowering the reactor into the furnace or by increasing the

furnace temperature to over 800°C (this high temperature was necessary to give >600°C in
the insulation above the furnace). A supplementary heater was procured for occasional use

in melting plugs, but its use was not tested.

3.7 PRELIMINARY RESULTS WITH A LARGER REACTOR AND BOTTOM

CONDENSER

After Test MS-18, the chlorination reactor was replaced with a reactor of larger (68-mm)
diam designed to give a downflow of vapor and an additional flow of nitrogen diluent gas to
a condenser at the bottom of the unit. The salt charge was in a crucible of 5.6 cm ID. The
schematic flow sheet (Fig. 5) shows only small changes from that for the 4-cm diam reactor,
but some flowmeters and reactors in the exit gas train are also larger. This larger system was
operated to provide information on the condensation behavior of the uranium chlorides. The
test conditions and results are included in the tabulations for the small reactor (Tables 1
through 6).

Tests MS-20 and MS-21 were with a charge of UCl, and C (petroleum coke particles)
and UO, feed. Test MS-20 with 0.21 mol of UO, and moderate Cl, rates showed a steady
accumulation of very dark gray-green solids falling to the bottom of the condenser chamber.
Removing the bottom cap dropped 58 g of solids into a plastic sack (0.15 mol UC], and an
estimated 0.02 mol remaining in the condenser). Test MS-21 was made with 80 g/h of UQ,

 
 

33

"JOSUSPUOD WONOq Yum ((] ww-g9) 103108l uoieuloy) s S

 

 

 

 

-t

CNOAn

l

 

Y [ 3OVNENS

1SNVHX3
dooH

L0¥1—-¥06 OMO INHO

> —13Mm

d313N
1S3l

 

 

 

00
_m— vall

oA —+—1w

4ILINONVYIN

 

%09

104 D

m van
[3ovnEnd]
1
o

SYILINMOTd SSYAN 94 OL 4
SHILIAVIOY 94 O1 |

 

 

 

 

 

431714

 

o\

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A201
334

 
34

feed and gave 236 g of solids in a collection bottle below the condenser (0.62 mol UCl,). The
test went well with the exception of two plugs of feed lines for the UO, feed. The average
Cl, utilization was 95% even though the chlorine feed was twice continued until the CO,
showed a significant drop off from depletion of oxide from the charge.

After Test MS-21, the crucible was removed and the apparatus cleaned to obtain weight
material balances for MS-20 and MS-21 together. The measured MS-20 and MS-21 results

arc:

1.47 mol UCI, in the initial charge;

4.5 mol C (petroleum coke) in the charge;
1.19 mol UO, fed to crucible;

1.27 mol CO, on traps;

2.8 (weight) or 3.3 (feed flowmeter) mol total Cl,;

0.26 mol Cl, on Cu-foil trap;

>90% Cl, utilization;

0.77 mol UC], into product receivers;

0.38 mol UCI, released from the reactor walls by a wiper blade treatment;
0.09 mol UCl, remained on reactor walls;

0.12 mol UCI, deposits on cap, sparger tube, and feed tubes; and

~ 1.3 mol UCl, in the crucible after MS-21.

This discharge of UCI, powder as noncaking, flourlike particles shows a partial
demonstration of the pilot plant product collection concept. Over 60% of the vaporized
uranium discharged in this way, and 40% deposited on the apparatus walls. Part of the
deposits were hard, dark, and difficult to loosen from the quartz wall. The 1.27 mol CO,
compared to 1.19 mol UO, shows the effect of oxide impurities, water, or incomplete

reduction of uranium oxides to UQ,.
Test MS-22 was like test MS-21 with the following changes:

additional charge to give about 10 cm depth of melt in the crucible;

addition of MgCl, and NaCl to give a charge composition (before reaction of UCI, with
UO,) of 1.7 mol UCl,, 0.21 mol MgCl,, and 0.21 mol NaCi;

a large purge flow of nitrogen to the UO, feed line and a reduced nitrogen purge flow
into the reactor top; and

several different UO, feeds to observe the differences in exit gas rates and composition
vs the feed characteristics.

 
35

Test MS-22 gave results that are favorable with respect to steady-state operation. The
chlorine feed was maintained for 4 h at 0.01-mol Cl,/min and an overall chlorine utilization
of 82%. Flow differences indicate an initial chlorine utilization of near 100% for 1 h. After
the flow differences showed a decrease in chlorine utilization, a feed addition containing 2 g
of carbon black gave a short period of doubled CO, evolution and a return to near 100%
chlorine utilization. These increases indicate that the conversion was limited by the reaction
of the petroleum coke and that the addition of 2 g of carbon black to the charge containing
48 g of petroleum coke more than doubled the rate of the reduction reaction. After the
chlorine utilization had again dropped, an additional 2 g of petroleum coke did not yield a
significant change (<10%) in the rate of CO, evaluation. The nitrogen purge to the UO, feed
line eliminated the plugs or deposits that occurred in Test MS-21 without a purge. There was
no observable difference in reaction results for dense UO, of low surface area (ball milled),
as compared to porous UQO, of high-surface area (gel process spheres). The condensed
uranium was again divided about 60% as discharged powder and 40% as deposits on the
reactor walls in agreement with tests MS-20 and MS-21 results. The moles of condensed
uranium was 65% of the feed UO, as compared with about 115% for Tests MS-21 and MS-22.
The lower amount of uranium vaporized agrees with previous results showing less volatility of
uranium with MgCl, and NaCl in the charge. The deposit of dense dark crystals on the
reactor wall at the low end of the furnace was much smaller for Test MS-22.

Test MS-23 was intended to test a more steady-state operation using a combination of
UO,-C spheres and UO, powder to give a feed UO,/C ratio of 1 mol/mol. Test MS-23 run
schedule was completed as planned with the exception of a severely restricted gas flow inside
the quartz reactor just after the chlorine feed was shut off. A quartz baffle with nitrogen flow
to the reactor top completely eliminated the deposition of condensed uranium above the
furnace. The total UO, added and reacted (0.15 mol prerun and 0.96 mol at temperature) was
greater than any of the previous tests. The quartz crucible probably cracked during heatup
and leaked part of the charge into the bottom region of the reactor. The frozen melt probably
obstructed the vapor flow to the condenser and affected the other test results.

Tests MS-24 through MS-30 were intended to provide information important to the
design of pilot-plant chlorination equipment. A series of tests were completed to determine
results for short-term steady-state operation with increasing rates of UO, and Cl, feed (see
Table 7). The Cl, feed rates were up to 770 cm*/min (34 mmol/min) for test MS-26, and

 

 

 
 

36

1030 cm®min (46 mmol/min) for test MS-28. Test MS-28 demonstrated a continuous screw
feeder for UO, powder, while all previous tests were run with periodic batch additions of UO,,.
The primary objective of tests MS-27 and MS-29 was to expose three proposed materials of
construction (carbon composites) to the chlorination reactor conditions. The MS-27 and MS-
29 results also give chlorine utilizations at low chlorine feed rates for comparison with the
higher rates. The vaporization and condensation behavior of the uranium chlorides was
observed for a wide range of Cl, feed rates and some variations in the gas and vapor flow
configurations. The most favorable reaction conditions of carbon black in the melt and melt

temperatures over 700°C were used, with the exception of a lower temperature for MS-30.
Many of the MS-24 — MS-30 results are included where appropriate in Sects. 3.2 — 3.5.

The tests of material specimens were part of a larger investigation and are reported
elsewhere.’

A primary criteria for design and operation of the larger reactor system was to provide
a separate condensation and measurement of the condensed uranium compounds. The
simplest model for the vaporization behavior is that the gases leaving the melt are saturated
with UCI, at the melt temperature. The results for MS-4 through MS-18 commonly show
much larger amounts of volatilized uranium—often five to ten times the amounts calculated
from the UC], vapor pressure. These results are discussed and an explanation suggested in
Sect. 3.6. The results for MS-20, -21, and -22 with petroleum coke show condensed solids
about three times the amounts calculated from the vapor pressure of UCl,. The utilizations
of Cl, and the results from a small addition of carbon black in MS-22 indicate a need for

better reductions of U(VI) [or U(V)] to U(IV). By using carbon black in melts at >700°C,
the amounts of condensed uranium were much closer (typically 120%) to that calculated for

the UCI, vapor pressure. The high chiorine utilizations (see Sect. 3.2) are consistent with this
change in vaporization behavior.

Discharge and collection of a UCl, powder are highly desirable to avoid the problems
from deposition of UC], solids or the problems of collecting a UCl, liquid product. The
proposed plant concept is to use a quench gas recycle to produce solids below the UCI, triple

point of 15 mm Hg, 590°C. Our reactor system does not allow the large gas flows necessary
for a valid test of this concept. The MS-20 to MS-30 results show 48 to 73% of the

condensed uranium as powder into the product jar and 27 to 52% deposited on the system

walls. The two most important effects on how the condensed solids collected appeared to be:

 

*To be issued as an AVLIS program milestone report approximately September 1991.

 
37

1. Turbulence in the condenser results in deposit of condensed UCl, on the walls and
reduces the fraction that discharges to the product jar. A quench gas inlet into the
condenser gave poor results.

2. More dilution of the UCI, vapor increases the fraction of solids discharged, but the
dilution must be done without turbulence in the condenser. The highest Cl, feed rates
gave the highest UCl, vapor concentrations (230 mm of Hg calculated) and deposits that
completely closed the condenser cross section.

4. CONCLUSIONS

High rates of chemical reaction and good utilizations of Cl‘2 were demonstrated for
reaction of UQ,, Cl,, and C to produce UCIl,. A molten salt medium containing UCI, allows
dissolution of UQ, by the reaction UO, + UCl, - 2UOCI,, and this is favorable to high rates
of reaction. Starting with UQ, dissolved in UCl,, the initial rates of reaction of chlorine can
be very high with low concentrations of chlorine in the exit gas. The rates of reduction
reactions to remove oxygen as CO, or CO control the overall rates of UCl, formation. With
carbon black in a melt at about 730°C, the rates of CO, evolution matched the Cl, rates for
Cl, feed rates up to 0.046 mol/min in a crucible of 5.6-cm ID.

Less favorable conditions for reduction give lower utilizations of Cl, at steady state and
greater volatilization of uranium—probably as UCl; or UCl;. Carbon black gave practical rates

of reaction and good results for melt temperatures down to 645°C. Petroleum coke of low-
surface area gave poorer results at 730°C than carbon black at 645°C. With CO as the
reducing agent, the steady-state utilizations were <40% for Cl, and 10 to 25% for CO.

The uranium oxide should be reduced to approximately UO, before use as chlorination
feed. The results indicate that the chlorination reactions are simpler and operation is better
for UQO, as compared to U0, or UO,;. A test with UO, feed gave lower chlorine utilizations
and much more condensed uranium than for UO, feed at similar conditions. The physical
properties of the UQO, feed do not appear to be important; UO, feeds of low- and high-surface
areas did not show any detectable differences in results.

The amounts of condensed uranium were compared with calculated rates of UCI,
vaporization. The calculations assume that the N, sparge to the melt and the CO, product are
saturated with UCl, vapor at the melt temperature and composition. The results showed

agreement with the calculated results for the effects of temperature (i.e., UCl, vapor pressure),

 

 

 
 

38

the effects of MgCl,-NaCl as nonvolatile diluents, and the effect of the N, sparge gas flow
rate. However, the relative oxidation-reduction of uranium salts in the melt is also very
important. The experimental amounts were from 80 to 150% of the calculated amounts with
good reducing conditions (carbon black or no Cl,), but were from 300 to 1000% of the
calculated amounts for chlorinations with petroleum coke or CO reducing agents.

The experimental system used here did not allow a valid duplication of a pilot-plant
collection system for UCI, vapors. From 48 to 73% of the condensed solids were collected
as a powder in a product jar below the condenser; the other 27 to 52% deposited on the
apparatus walls. The deposits on the walls were partly powder and partly dark, dense
crystalline solids that formed more rapidly when the Cl, feed rate exceeded the rates of
reduction reactions. Examination of both types of solids by X-ray diffraction shows the lines
of UCI, only without any lines of other uranium compounds. Chemical analyses for uranium
and chlorine indicate mostly UCI, with small amounts of UCl,, and probably some oxychlorides
from reaction with water vapor during sampling.

Control of the UO, feed rate to the chlorination melt is very important to dependable,
steady-state operation. A deficiency of UO, results in poor utilizations of Cl, and much higher
(excessive) volatility of uranium. The UO, feed reacts rapidly with UCl, to give UOC,, which
has a limited solubility in the molten chloride salts. Excessive UO, can solidify the charge so
that the gas flow is obstructed or channels with poor contact. Carbon particles are wetted by
and remain suspended in the melt; a wide range of carbon black inventories is acceptable.
When the reduction conditions are favorable, all reaction rates are determined by the Cl, feed
rate.

Overall, good results were demonstrated for the chemical reactions to produce UCI, from
UO,, Cl,, and carbon black. This result is much different than the results of an earlier study
to prepare uranium metal by electrolysis of UQ, dissolved in fluoride salts. There, chemical
reactions other than the desired ones always resulted in reductions of UF, in addition to UO,
and in low current efficiencies. The engineering problems for UC], preparation (materials of
construction, process control, UO,-C, and Cl, feed procedures, UCl, condensation and
removal) can be addressed in pilot-plant systems with confidence in the chemical flow sheets

for the process.

 
10.

11.

12.

13.

14.

39

5. REFERENCES

Phillip G. Sewell and Norman Haberman, "AVLIS Program Powers Ahead in the United
States,” Nucl. Eng. Int., October 1988.

Lawrence Livermore National Laboratory and Martin Marietta Energy Systems, Inc.,
"Selection of an AVLIS Uranium Feed Process for Large-Scale Demonstration,” 1.-12038,
September 1990.

Joseph J. Katz and Eugene Rabinowitch, The Chemistry of Uranium, McGraw-Hill, 1951.

R. G. Canning, "The Production of Uranium Metal Powders by Electrolysis in Molten
Chlorides," Australian Atomic Energy Symposium - 1958, June 1958.

W. L. Lyon and E. E. Voiland, The Preparation of Uranium Dioxide from a Molten Salt
Solution of Uranyl Chloride, HW-62431, October 1959.

T. A. Gens, Laboratory Development of Chloride Volatility Processes for the Recovery of
Uranium Directly from Spent Rover Fuel or from its Combustion Ash, ORNL-3376, June
1963.

A. R. Gibson et al., "Processes for the Production of Uranium Oxide,” U.S. Patent
3,117,836, January 14, 1964.

Y. M. Sterlin and V. V. Artamonov, cited by E. M. Levin and H. F. McMurdie, Phase
Diagrams for Ceramists: 1975 Supplement, The American Chemical Society, Columbus,
OH, 1975, p. 396.

J. C. Mailen et al., Laboratory Studies of the Production of Uranium Chlorides from
Uranium Oxides, ORNL/TM-11609, Oak Ridge National Laboratory, October 1990.

M. W. Chase et al., JANAF Thermochemical Tables, Third Edition, American Chemical
Saciety, American Institute of Physics, and National Bureau of Standards, 1986.

M. H. Rand and O. Kubaschewski, The Thermochemical Properties of Uranium
Compounds, Interscience Publishers, 1963.

E. H. P. Cordfunke et al., Thermochemical Data for Reactor Materials and Fission
Products, Eur.-Contractno., ETSN-0005-NL, 1988.

David Brown, "Compounds of Uranium with Chlorine, Bromine, Iodine," Gmelin
Handbuch der Anorganischen Chemie, Vol. C9, 1979,

Josef Krahe and Franz Miiller, "Zur Thermochemie der Stoffsysteme U, Th, Pa, C, O,,
CL," Institute fiir Chemisehe Technologie - Jul 565 - CT, December 1968.

 

 

 
41

APPENDIX

A. THERMOCHEMISTRY

 

 
43

A. THERMOCHEMISTRY

The use of thermochemical data does not identify the probable reactions with any certainity
or degree of confidence. There are several major causes of uncertainty. Uranium chemistry is
complex with stable valences of 3, 4, 5, and 6, and with stable oxychlorides. UO,Cl, and UOCI,
are well-known compounds and others are possible. All the possible products must be
considered. The uranium chlorides are more volatile with increasing valence, but UCl; and UCI,
are less stable with increasing temperature and decreasing Cl, partial pressure. All the uranium
compounds have large heats of formation, and calculating the free energy of these reactions
usually results in a small difference from two large numbers. Small percentage uncertainties for
the large numbers give large uncertainties for the differences.

Thermochemical data (Table 10) can be used to make calculations for chlorination reactor
conditions.'®!? A temperature of 700°K (427°C) is about the lowest temperature of interest for
practical rates of reaction, and the 1100°K (823°C) is above the boiling point of UCl; and is
near the highest practical temperature. The relationships between the different U-O-Cl
compounds can be illustrated by a matrix listing‘ (Tables 11 and 12).

Data are available for heats of formation at 298°K for all the compounds (Table 11). The
free energies of reaction of 900°K are more useful for the calculations (Table 12), but the data
are much less complete. Table 12 shows estimated values for some of the compounds and one
of several different published values for UO,Cl,.

Tables 11 and 12 appear to show that the oxychlorides are more stable than either the
chlorides or oxides. The free energies of formation show that either the U(VI) chloride or oxide
are easily reduced to the corresponding U(IV) compounds, but the U(VI) oxychlorides are more
difficult to reduce to U(IV) compounds. Since the oxychlorides are probable intermediates for
conversion of uranium oxides to uranium chlorides, a conversion may appear favorable overall,
but one of the steps involving an intermediate may be much less favorable. For example,

consider the following:
UO, + 2C + 2Cl, -» UC], + 2CO.

At 900°K, AG = -246.5 kJ, but individual steps show:

UO, + Cl, » UOClL, AG =-1742;
UO,CL, + C » UOCL + CO, AG = 13.6;
UOoCl, + Cl, - UOCI, AG = -119.8; and
UOCl, + C - UC], + CO, AG =341.

 

 

 
44

Table 10. Thermochemical data

 

 

 

 

Melting Boiling Free energy of formation, -AG® Ref.
point point (kJ/mol) No. for
Compound (°K) (°K) 700°K 900°K 1100°K data
172. 238 0 0 0 10
Cl,
CCl, 250. 350 -1.7 -28.3
COodl, 169. 281 187.1 177.8
CO, 216. 195 (subl) 395.4 395.7
CcO 74. 81 173.5 1914
C, — >4000 0 0
Udl,, 1115 — 741.8 699.1
UuodCl - - ~T715. —
UCl, 863. 1065 847.8, 794.5,
UuoCl, a — 943 900
U0, 3150 - 963.5 930.8
UCl 600 800 845.3 ~780
UOC], - — - —
UO,Cl — — — —
1/3[U304] d-1300 — 1038.0 998.1
UCl, 452 ~550 841.3 789.3
UQod, ~ —
UO,Cl, >1050 1130 1105
UO, a — 1043.0 992.9

 

*Decomposes.

 
45

Table 11. Heats of formation for U-O-Cl compounds at 298°K

- AHP° in kJ/mol U

Reference No.: See Table 1 for Compounds

 

Valance All Cl One O Two O >Two O
0 U U U U
0 0 0 0
3 Ucl, UOdl
893.32 947.3
4 UCL, UOC, Uo,
1051.4 1087.8 1083.7
5 UCl UOodC, UO,Cl
1094.1 1185.7 1188.3
5.33 (U0,),Cl, U,;04
or 5.5 1202.5 1191.2
6 UCl, UOC], Uo,Cl, UO,
1132.6 1238.5 12473 1225.9

 

*Values of 860 to 880 kJ/mol are also reported.

Table 12. Free energies of formation for U-O-Cl compounds at 900°K (627°C)

 

- AG in kJ/mol U
Valance All Cl One O Two O >Two O
0 18] U U U
0 0 0 0
3 UCl, UoCl
699.1 ~ 780 est.
4 UCL, UOd, Uo,
794.5 900.2 930.8
5 UCl, UOdl, UO,Cl
780 ~ 1000 est. ~ 1000 est.
5.33 (U0,),Cl; U304
or 5.5 ~ 1050 est. 998.1
6 UCI UOCI, UO,Cl, U0,
789.3 ~ 1020 est. 1105 992.9

 

 

 
46

These numbers indicate that the reactions could stop at UO,Cl, or UOCI,. If using CO to give
CO, as the product is considered, then the two reduction reactions change to:
UOoCl, + CO - UOC], + CO, AG = 0.5 and
Uuod, + CO - UCl, + CO,, AG =21.2.
The uncertainties for A(G® values of UO,Cl, and UOC], are probably larger than either of the

above AG values, so it is difficult to determine whether the reactions are thermodynamically
favorable. The more favorable calculation for CO as compared to C may also be misleading.

The C would be present as a solid with an activity of 1, while CO would be mixed with other
gases and would have a lower activity for 1 atm total pressure.
Many of the reactions to change between the U-O-Cl compounds are shown in Fig. 1.

Large values for the negatives of the free energies of reaction (kJ/equiv at 900°K) show
reactions that are thermodynamically favored. Negative values in Fig. 1 indicate that the

reactions are not thermodynamically favorable. The data for the oxychlorides are uncertain and
values ranging from -20 to +20 kJ do not justify predictions. The formation of UCls and UCl;
appears to require excesses of Cl, and will not be complete. Otherwise, all additions of Cl, are
favorable and oxychlorides should add chlorine to give UO,Cl, or UOCI,. The reduction of UO,
or U,O; to UO, by CO are highly favorable. The reduction of UOCIL; by CO to give UCl; is
very unfavorable. The other three reductions of oxychlorides by CO give free energies of
reaction that are too near zero to justify predictions. A practical preparation of UCl, probably
requires that the reductions of UO,Cl, and UOCI, are possible as they would otherwise
accumulate as stable products. Some additional possible reactions not shown by the diagram
include:

udl, + U0, -» 2U0Cl, AG = -74.7kJ;

UCLs + UO,Cl - 2UO0CL;, AG = ~-220 kJ;

UCl + UO,(Cl, - 2U0Cl,, AG = ~-145 kI,

ucl, + U0,Cl, -» 2U0CL,;, AG = -100 kJ;

UCl, + UO, - UOCl, + UCl,, AG = -179 kJ; and

UCk + UOCl, -» UOC], + UCl,, AG = -125KkIJ.

The first five reactions indicate that the uranium chlorides will react to give oxychlorides.

Krahe listed vapor pressure equations as shown in Table 13.* Calculated values from these

equations are shown as Fig. 6 The decomposition of UCls (or UCl) into Cl, and UCl, must also

be considered as the UCI or UCl, are only stable when excess Cl, is present.

 
47

Table 13. Vapor pressure equations®

 

 

Temperature
Compound A -B -C (°K)
UcL (s) 19.224 15,760 3.02 298 - 1110
UCk (1) 24.044 14,340 5.03 1110 - 1950
uay, (s) 20.329 11,350 3.02 298 - 863
ucy, () 26.079 9,950 5.53 863 - 1062
UCk (s) 21.810 7,450 4.03 298 - 600
uc (1) 26.027 6,210 6.29 600 - 800
Uc (s) 22.317 4,765 5.03 298 - 453
ucy (1) 26.120 4,060 - 7.04 453 - 650

 

alcz»gp,m,,,=A+B/I‘+ClogT

 

 
ORNL DWG 81A-~-11

1000 . | , | , ,
800

600
400

 

200 | UClg

100 | UCls
80

60 |
40

 

20 A mp: 179°C
A mp: 590°C

VAPOR PRESSURE (mm Hg)

A mp: 327°C

UCls
4T >800°C |

 

 

 

2 i 1 ] i I 1

100 200 300 400 500 600 700 800

TEMPERATURE ( °C)

Fig. 6. Vapor pressures of uranium chlorides.

 
49

B. INDIVIDUAL TEST RESULTS

Some detailed results are given here as examples of the experimental studies. Some

tests are not mentioned to minimize duplication or for the following reasons:

® MS-1, MS-2, MS-3, MS-4—details are in a preliminary report.?

® MS-5, MS-9B—mechanical failures; therefore, no useful chlorination results.

® MS-6, MS-19—training and calibration tests without any uranium or salt charge.
e MS-11A, MS-11B—volatility tests without chlorine feed.

B.1 MS-8

Test MS-8 was made with a charge of 103.5 g UCl, and 50.0 g of UQO, and other
conditions similar to MS-4. The Cl, flow was started with an estimated sparger immersion
of half of the melt depth as greater immersions resulted in zero gas flow. A good flow of
CO, was indicated in 10 min in agreement with the system holdup times. This CO,
evolution peaked in 30 min and tapered off to about half the peak value by 60 min. The
CO, evolution rate continued for 3 h with only small effects from increased immersions of
the sparger, a 30°C temperature increase, and changes in Cl, feed rate. After 4 h of Cl,
feed, the chlorination reactor plugged and would only pass about 20% of the intended gas
flow even though the feed gas pressure was increased to 6 psig. Disassembly of the cold
system showed a complete closure of the reactor cross-section by a dark crystalline dome of
solids above the furnace, but below the cooling jacket (Fig. 4). The sparge tube and the
thermowell were frozen in position by the solids. The upper half of the solid deposits were
a loose powder instead of dense crystals. The crucible and reactor bottom only contained
a few crumbs of solids.

A simple plug flow of gases that are saturated with UCl, cannot account for the
transfer of uranium solids. The total amount of gas feed was about 1.6 mol to give a
calculated UCI, concentration of 20 to 25 mol % in the vapor. The UCI, vapor pressures

are reported to be 60 and 110 mm Hg at the two run temperatures of 650 and 680°C.
The rate of CO, evolution showed little variation with run variables (temperature,

sparger immersion, Cl, flow rate, crucible charge depletion). The CO rate was approximately

constant throughout the test.

 

 
50

The results of the MS-8 material balances are:

Weight measurements show:

Feed UCl, 103.5 g, 0.272 mol U, 0.544 mol Cl..
Feed UO,  50.0 g, 0.185 mol U, 0.370 g-atom O,.
Cu Trap 42.2 g Cl, or 0.592 mol Cl,.

1st Ascarite 8.7 g CO, or 0.198 mol CO,.

CuO -5.9g O, or 0.369 g-atom O,.

2nd Ascarite 16.2 g CO, or 0.368 mol CO, or Co.

Chlorination 15.3 g weight gain or 18.7 g Cl, (allowing for O, loss)
Reactor to give 0.264 mol Cl, reacted.

Gas flow rates times concentrations show:

About 0.45 mol CO feed (vs 0.57 mol CO, on Ascarite traps),
About 0.9 mol C}, feed (vs 0.86 volume from weights),

0.23 mol CO, (vs 0.20 on trap), and

0.45 mol CO (vs 0.37 on trap).

Differences in flow rates show:

0.42 mol CO, a good check;

0.22 mol CO,, a good check;

0.68 mol CO + CO,, a reasonable check; and

From 0 to 0.6 mol Cl, to CU trap, depending on which flow measures are used.

Chemical analyses of product samples show:
97.2% of feed uranium,

110% of calculated Cl,, and

19% of calculated O,.

 

 

Calculated compositions of:
Dark crystalline Powdery
solids, mol % solids, mol %
udi, 93.8 81.4
Uo,Cl, 0.9 10.8
UClg 5.3 7.8

Examination of the two solids by X-ray diffraction show only UCl, with no indication
of other uranium compounds.

 
51

B.2 MS-22
Material was added to the crucible removed after MS-21 (541.7 g of charge, 7-cm
depth) as follows:

20.0 g MgCl,,
12.0 g NaCl,

12.0 g C (petroleum coke),
60.0 g UO, (ball-milled powder), and

42.5 g UCl, (the condensed MS-21 wall deposits).

The reactor furnace was controlling at 685°C at 10:30 a.m., but the sparger appeared
to show solids and signs of plugging when lowered to less than 2 cm from the crucible

bottom. The Cl, flow was started at 10:55 and 20 g batches of UQO, feed added at 11:35 and
at 15-min intervals thereafter with some omissions. The sparger was lowered to the crucible
bottom at 11:18 a.m. with no signs of solids or plugging. The evolution of CO, is shown by
the recorder chart for the CO, concentration '(Fig. 7) and were confirmed by post-run gas
flow calculations (Table 14). After 1 h with little or no flow differences for flows in and out
of the Cu trap for Cl,, these flows appeared to show chlorine losses. At 13:10, 10 g UO,
— 2 g carbon black was added. This resulted in a very high rate of gas evolution that
overpressurized the gas train and showed about triple the previous CO, rate. This high rate
decreased back to the base rate in about 20 min. The remaining UO, feed additions and
an addition of 2 g of petroleum coke were completed without any noticeable effects on the
CO, concentrations or rates. About 45 min after the last UO, feed, the CO, rate decreased
sharply and the Cl, losses increased, indicating a depletion of oxide from the charge. The
Cl, feed was stopped and the CO, rate decreased to a low value in about 30 min.
After cool down, the weights showed:

+31.2 g or 0.44 mol Cl, on the copper trap;
+47.9 g or 1.089 mol CO, on the 1st Ascarite;

~0 g or ~0 mol CO oxidized by the CuO;
+0.8 g or 0.018 mol CO, from CO on the second Ascarite trap;

134.1 g or 0.353 mol UCI, powder in the product jar;

66.1 g or 0.174 mol UCI], collected by scraping the reactor walls;
0.29 g or <0.001 mol UCl, on the filter;

838.4 g of charge in the crucible as about 10.5 cm depth of melt; and

37 g or 0.097 mol of UCI, collected by washing the reactor, the cap, sparger, and feed
line.

 

 

 
 

CLOCK TIME, h AND min

52

ORNL DWG 91-405

 

 
  
  
   
    
  
 
   

N,FEED 270 ¢cm3¥min
THROUGHOUT

STARTED 10 g UO,-2 g CARBON

 

30 40 50 60 CO, CONCENTRATION, %

 

«— SPARGER DOWN 3 ¢m (TO BOTTOM)

F1515
«— Cl, FEED OFF
p
—1.0 g U0 ,-0.2 g CARBON BLACK
- 1445 = 2
b a5 <«— 10th UD, FEED (20 g)
- «— 2 g PETROLEUM COKE
<—9'" YO, FEED (20 g}
L 1345 «—8'" UO, FEED (20 g)
. «— 7" YO, FEED (20 g)
2 1515 <«—— COMPLETED
! | | |
0 10 20
-
5'" U0, FEED (20 g)
- 1245 N
«— 4'" U0, FEED {20 g)
| | | 1| 1 _
0 30 68 118% 180 270 405 CQ, cm®/min
1215
<— 3" U0, FEED (20 g)
L1145 "« 2% UO, FEED (20 g)
<—— 1"'U0, FEED (20 g)
- 1115

 

Cl, ON AT 1055 218 cm>/min
/MS-ZZ 60 g UO, 50 g C{COKE) IN CHARGE

Fig. 7. CO, concentrations during MS-22.

 
53

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(uww/ o)
(unu £$7) 211 79¢ - €LE (unw £T) L1T 0LT $9¢T S9C moy Ay
sed JnJj
08L'LT - 0I¥'E - $09'tS 000901 | 089€0T |  089°€0l 0} PaNAII0D
950°8E 9EL'TPT v10'y 0sL'svl $90't9 000901 | 089601 |  089°€0l 16€ unJ 20UM
1£€1
015'T 06¥'11 09§ 050'C1 006'1 01Z‘8 0666 086'8 €0S1 330 D 9¢ Syl
0cT'E 0L9'6 008 0Ly 01 £8L'S 0L0'9 01€9 0SH9 €2 eyl
091'y 0Z0'€1 T8¢ 0LSEl 0r1's 02’6 0£8°8 0988 $p33J ‘0N OML 7€ 00v1
oTL'y 062C1 ) C8T 2l ovs'L 001'8 0128 oL1'8 $P33J ‘0N oML Ot otel
0sS'1 0SLE 0 00L°€ 0L0'C 000~ 0EY'T 00Z'T 6 12€1
0L0'Y 015’6 ove 0SL'6 orE'S 00S'S~ 008'S ovv's $S0] sed “0-“0N 1T ootl
ort'y oLYCl OLL €l or6'L 001°8 08C'8 0£0'8 $pa3J ‘0N oML 0t 0gCl
020°S 0L9°ZI 09 0El'El 00S'L 099'L 065 L 089'L P33 ‘0N MO 67 1021
0897 056'C1 0sy 00v'€1 020'8 081°'8 0£0'8 0.7'8 $pa3J ‘0N oML 1€ 0El1
0€L'1 0£S'S 0 ory's 0L8'E orl'y 0l6€ 008’ <1 SITL
0001 00L'S 0 or9's 018°¢ 089'y 066'€ 00L'Y <1 0011
0§ OvE ¥ 0 oved 0LT'l 00S'¥ 010'% 06C ¥ §SO1L o D S SpOT
0921 0.T'8 0 000'8 0 026'L 056'L 010°L D oN 0 101
0£¢C 0£0°0T 008 0£8°0C 0 000°t! 0SE8I 00861 dmesf] St 0060
- o'l - L1’ 121 0z’ 10°1 00’1
00 + 00 nd uo )
159} 1om ‘0D + 00 +°N S-Wd 90 + %00 + 00 +°N ‘0 02 +°N ‘N ‘N
snurw - S-WA snui WA WA 1-Wd 9- WA TIWd | 1591 M S)UAWWOD fifi_v salun 301D

 

$10)0B] J3)dUl pue ‘sed ‘SI9PW

 

 

AINb3 N JO (WD “SmOf sed paiegnofe)d

 

 

 

 

s3urpeal 19z1je)0) wolj suone[noes moy sed ZZ-SW v1 Sl9EL

 

 
 

54

The flowmeter totalizer readings and the average of pre- and post-run calibration factors
were used to calculate flows for fourteen intervals (Table 14). There were some losses of
gases to allow breakup of a cake on the top of the 1st Ascarite absorber at 12:10 p.m., and
from the overpressurization at 1:10 p.m.

B.3 MS-28

Test MS-28 was made using a continuous feeder for UO, powder and Cl, feed rates of
620, 840, and 1030 cm®/min. This feeder is a glass and Teflon unit with a screw of Teflon
flights inside a glass tube and a closed, gas-purged hopper. The screw uses an O-ring seal and
gives controlled and reproducible powder feed rates using a variable-speed drive motor. The
powder bridged in the hopper above the screw several times, but the bridges were casily seen
through the glass and were broken by moderate taps on the hopper wall. Feed was
interrupted twice by plugs at the end of the feed tube in the chlorination reactor. These
plugs were hard, tight solid cylinders in the last 0.5 cm of the feed tube and appeared to result
from reaction of condensed UCl, with UO,. After the second plug, the feed tube end
position was changed to about 1 cm into the crucible instead of 4 cm; the test was then
completed without further feed difficulty. The tube end was partly restricted by solids when
removed after cooldown.

Test MS-28 was made in three parts as a result of the two replacements of plugged feed
lines. Nitrogen purge gas was lost during these replacements and through a leak early during
the test, but all other material balances were excellent. The weight balance showed 0.1% loss,
and the weights were confirmed by the flow rates times concentrations and by the flow
differences. The overall results included:

U0, feed 521 g (1.93 mol)
Product jar 390 g (1.03 mol)
Reactor wall deposits 432 g (1.13 mol)

Cu trap 22.0 g (0.310 mol Cl,)
Other traps 103 g (2.34 mol CO,)
Total Cl, feed 316 g (4.46 mol Cl,)

Average Cl, utilization 93.1%

The reactor wall deposits included a nearly complete closure of the reactor cross-section by
deposits between 2 and 5 cm below the bottom end of the furnace. This is inside the end
insulating brick and just above the cooling jacket. The deposits were about 50% removed as
powder by moderate scraping, 35% hard, dense chunks removed with difficulty, and 15% as
thinner films removed by water washes. The product jar collection was 53% of the UO, feed
or 48% of the condensed solids.

 
55

C. EQUIPMENT DETAILS AND CALIBRATIONS

This equipment used quartz as the material of construction for hot chlorine gas. The
components in contact with chlorine gas at room temperature were also selected to avoid
excessive corrosion. Otherwise, the system was a series of small, special chemical reactors and
commonplace types of laboratory flowmeters, temperature measurements, and control
instruments.

C.1 Flow Control and Measurement

Feed flows of gases were set manually using needle valves and variable area flowmeters
with ball floats. The primary flow measurements for material balances were the totalizer
readings from Hastings mass flowmeters. One-time readings of indicators were not accurate
for material balances because of delayed effects of both melt and gas inventory changes, a
resonance-type oscillation of exit gas flows, and drifts of feed flows between flow adjustments.

The flowmeters were calibrated with N, having one primary calibration at the ORNL
instrument shop, and secondary calibrations against the wet-test meter just before or after
experimental tests. The Hastings mass flowmeters exposed to Cl, (F1, F4, F5) showed
continuing changes in calibration. The long-term change was to require an increasing
multiplier to convert the indication to a true flow, but there were also some short-term
decreases in multipliers. The calibrations remained linear; the multipliers were time
dependent, but not flow dependent. The manufacturer’s factors were used to convert the
indicated nitrogen flows to other gases. These were the following (air = 1.00) for the mass

flowmeters.
Gas Conversion Factor
N, 1.02
CO 1.00
CO, 0.73
Cl, 0.85

The material balances were based on the N, equivalents being additive. For example,
a combined flow of one liter each of N,, CO,, and Cl, would show as 1(1.02/1.02) +
1(1.02/0.73 + 1(1.02/0.85) = 3.60 L on the totalizer.

The variable area flowmeters were convenient for short-term adjustments of feed gas
rates. Their point indications had the same limitations as the mass flowmeter indications, and
were of limited usefulness in two other ways. The ball flows gave very non-linear flows and
did not give simple factors to convert for different gas compositions. The meters were
frequently fouled or "sticky" from chlorine corrosion products or solids entrained in the exit

gases.

 

 

 
C.2 Product Gas Reactors and Traps

Reaction and removal of individual components of the product gases by fixed beds of
solids was the basis for all three types of material balances. The weight changes of the fixed
beds showed the amounts of material reacted. The removal of individual components resulted
in flow differences that were a measure of the amount and also allowed use of CO, and CO
concentration measurements. The reactors were designed to minimize the total weights in
order to give weight material balances to 0.1- or 0.01-g precision using laboratory balances.
Attempts to use liquid scrubbers for the initial tests® were troublesome and unsatisfactory.

The Cl, leaving the quartz reactor was trapped by copper foil in a Pyrex tube inside a
furnace at 375 to 435°C. The reaction was visible as a sharp interface with plug flow, but the
products at higher Cl, rates collected as solidified melt on the bottom wall of the tube.

The CO, in the gas leaving the copper foil trap was collected by Ascarite II (8 to 20
mesh) in standard laboratory Drierite reactor units at ambient temperature. The reaction was
observed to show a sharp interface by appearance and by heat generation. At high CO, rates,
the Ascarite II became hot at the reaction interface and tended to soften and cake with high
resistance to gas flow. This plugging was only a minor problem for the 4-cm chlorination
reactor but resulted in serious flow interruptions for the 68-mm reactor. A 9.5-cm ID
Ascarite absorber was then used without further difficulty.

The CO was oxidized to CO, using a packed bed of CuO wires in a Pyrex tube in a
furnace at 425 to 480°C. This reactor gave a sharp reaction interface by appearance and no
problems. The CO, from oxidation of CO was absorbed with a similar reactor and results as
for the CO, leaving the copper foil trap for Cl,.

 
57

ORNL/TM-11792
Dist. Categ?g UC-501

hemistry)
INTERNAL DISTRIBUTION
1. D. H. Andrews 27. G. W. Parker
2. J.T. Bell 28. J. A. Pashley
3. W. Fulkerson 29. A. S. Quist
4. R. K Genung 30. M. H. Randolph
5-9. P. A Haas 31. J. E. Vasgaard
10. H. W. Hayden 32. R. L. White
11. W. H. Hermes 33. K-25 Records Dept.
12. J. R. Hightower 34. Enrichment Technol.
13. K. H. King-Jones 35. Cen. Research Library
14. F. E. Kosinski - 36. ORNL Y-12 Tech. Library
15-19. D.D. Lee 37-38. Document Ref. Section
20. L. A. Lundberg 39. Lab Records, ORNL RC
21-25. J. C. Mailen 40. ORNL Patent Section
26. J. R. Merriman
EXTERNAL DISTRIBUTION
41.  Office of Assistant Manager, Energy Research and Development, Oak Ridge
Operations, P. O. Box 2001, Oak Ridge, TN 37831
42-53.  Office of Scientific and Information Center, Department of Energy,
P. O. Box 2001, Oak Ridge, TN 37831
54. 1. C.Hall, U.S. Department of Energy, P. O. Box 2001, FEDERAL, Oak Ridge,
TN 37831
55. 1. D. Hughlett, U.S. Department of Energy, P. O. Box 2001, DNTNCON,
Oak Ridge, TN 37831
56-60. N. Habermann, U.S. Department of Energy, Washington, DC 20585
61.  J.T. Early, Lawrence Livermore National Laboratory, P. O. Box 808, Livermore,
CA 94550
62. R. W. Feinberg, Lawrence Livermore National Laboratory, P. O. Box 808,
Livermore, CA 94550
63. J. A. Horton, Lawrence Livermore National Laboratory, P. O. Box 808,
Livermore, CA 94550
64-160.  Given distribution as UC-501, Nuclear Energy (Chemistry).