LA-3562
c-49
0
(W-14 REPORT COLLECTION
REPF?CXXJCTiON
.
COPY
LOS ALAMOS
SCIENTIFIC
LABORATORY
of the
University of California
LOS ALAMOS
Distribution
s
NEW MEXICO
of Americium
Between
. Liquid Plutonium and a Fused Salt.
4 Evidence for Divalent Americium
.
UNITEDSTATES
ATOMIC ENERGY COMMISSION
CONTRACT W-7405 -ENG. 36
.
I—LEGAL
NOTICE
Thts report was prepared as an account of Government
sponsored
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with respect to the use of, or for damages reaulttng from the
uae of any information,
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Laboratory.
L
d
LA-3562
UC-4, CHEMISTRY
TID-4500
LOS ALAMOS
SCIENTIFIC
LABORATORY
of the
University of California
LOS
ALAMOS
.
NEW
MEXICO
May 17, 1966
Report
written:
Report
distributed:
December
1, 1966
I
Distribution
of Americium
Between
Liquid Plutonium and a Fused Salt.
Evidence
for Divalent Americium
by
L.
A.
J.
J.
J.
MuUins
Beaumont
A. Leary
..
—-,
-1-
.
*
ABSTRACT
The distribution
NaC1-KCl
containing
PuC13 mole fraction
consistent
range of 6 x 10-S to 2 x 10-2.
+
:
the temperature
kcal.
PUC13
(q
dependence
was obtained
The distribution
over a
data are
equation
:W(4)
=
salt phase
metal phase
-3.5
liquid Pu metal and a fused salt of
PuC13 has been studied at 698, 730, and 775°C.
with the following
Am (A)
From
of Am between
+
(Jq .
salt phase
metal phase
of the equilibrium
Amclz
constant,
a value of
for AH” for the above reaction.
ACKNOWLEDGMENTS
The authors
Johnson
for the Am,
G. M. Campbell
are indebted
to R. L. Nance for the PuCIS, to K. W. R.
to Group CMB-1
who assisted
for radiochemical
with the computer
,
●
-3-
analyses,
programming.
and to
.
*
CONTENTS
2!%2
Abstract
3
Acknowledgments
3
Introduction
7
Experimental
Equipment
Procedure
Preparation
7
,7
8
Results
of Materials
10
and Discus sion
10
References
19
Appendix
20
TABLES
1.
Distribution
of Am and Pu at 698°C.
11
2.
Distribution
of Am and Pu at 730°C.
12
3.
Distribution
of Am and Pu at 775°C.
13
4.
Equilibrium
Constants
at 73 O°C. for
Am +:
5.
Equilibria
Constants
Puclx
= Amcly
+ : Pu
15
for the Reaction
Am +:
l%cl~
= Amcl~ +:
-5-
Pu
18
ILLUSTRATIONS
EE!E!2’
1.
‘
Equipment
for Distribution
Plots of K’ /K;=
.
for the Stoichiometry
vs.
Studies
wt. % Pu in Salt, 730°C. ,
2.
PuC1l and AmCli through AmCIG
21
3.
PuC12 and AmCli through ~CIG
22
4.
PuCl~ and AmCll through AmCIG
23
5.
PuC14 and AmCli
24
6.
PuCl~ and AmCli through AmC16
25
7.
PuCIG and AmCli
26
through A.mCIG
through A.mCIG
-6-
INTRODUCTION
Americium-241
month as the result
Am in molten
into Pu at the rate of about 15 p. p. m. per
of (.3decay of Pu-241.
The chemistry
in liquid Pu, the Am is preferentially
the molten
of trace
amounts
of
Pu-molten salt systems has been discussed in earlier
(1, 2)
When PuCl~ is equilibrated at high temperature
with Am
publications.
dissolved
grows
oxidized
and concentrates
in
salt phase.
This report
equilibrium
summarizes
between
the results
of a study of the heterogeneous
Am and Pu in liquid metal-molten
salt systems.
EXPERIMENTAL
Equipment
The equipment
used for the distribution
The salt and metal phases
were
driven
furnace
tube which was heated by a Hevi-Duty
a stirrer,
sheaths,
The upper furnace
six sampling
a gas-vacuum
tube cover
The crucible
contained
tubes,
line,
two
Electric
and a motor
support
with a Brown Honeywell
by a Ta sheath.
immersed
Co.
tube furnace,
seals
and fittings
for
as thermocouple
The bottom furnace
were measured
The thermocouple
was controlled
by a thermocouple
-7-
steel
in the liquid metal phase and
recorder.
The temperature
which was activated
in a stainless
Temperatures
a fitting for an Ar line.
were recorded
rod.
1.
and were mixed by
Ta tubes which served
alumel thermocouple
Potentiotrol
was positioned
tube head contained
with a chromel
protected
is shown in Fig.
in a Ta crucible
a motor
Model M-5012.
Ta stirrer.
contained
studies
was
by a Wheelco
positioned
in the
thermocouple
well shown in Fig.
Ar which was purified
a U chip furnace
The atmosphere
1.
by passing
welding
in the furnace
tube was
grade Ar (99. 998% purity)
through
at 700°C.
Procedure
Approximately
700 g. of metal and 280 g. of salt were placed
Ta cup shown in Fig.
positioned
1 in. above the molten
during the sampling
into the melt.
stirrer
1 and heated to melting.
process,
the stirrer
phase.
The salt phase was sampled
to-3
The sample
temperature
p.s. i. g.
then raised
cases
The furnace
blank flange.
the mixing
process
The metal samples
in 4M
— HNO~ to remove
tube
were removed
All temper-
The tubes were
in freezing
or lower
temper-
was continued
for
After three salt and three
the furnace
was cooled
tube head was replaced
from
the
After temperature
in the furnace
to 480°C.
with a
at all times.
the Ta tubes and were pickled
salt prior to dissolution
-8-
the
The recorded
period.
of both phases
was maintained
any adherent
3 min.
tube which resulted
repeated.
and the furnace
An Ar atmosphere
Ni filter
was then set at a higher
had been taken in this manner
the metal and salt,
tube into the metal
temperatures.
kept at the same temperature.
was again established
metal samples
The
were taken at the same time.
are the equilibration
at least 1 hr. and the sampling
(+ O. 5°C. ),
sampled.
an evacuated
during this 3-rein.
into the cold zone of the furnace
ature or in some
were
to fill for approximately
as much as 4°C.
salt and metal samples.
equilibrium
of both phases
tubes were permitted
dropped
temperature
the Ta sampling
by lowering
and the
the salt through the Ni frit by pressurizing
Samples
atures listed in the tables
to freeze
lowering
changes
were lowered
temperature,
and the salt and metal phases
into the salt phase and filtering
furnace
temperature
at least 1 hr. at a constant
metal sample was taken by simply
tubes were
and thermocouple
was set at the desired
After
was stopped,
salt phase to minimize
and the stirrer
The controller
was activated.
The sampling
in the
in 6~ HC1.
The
(1) Metal phase
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(lo)
(11)
(12)
(13)
(14)
(15)
(16)
.
>
(17)
Salt phase
Ta crucible,
2-1/2 in. O. D. ,
2-7/16 in. I.D. , 3-1/4 in. tall
Ni crucible,
2-13/16 in. O. D. ,
2-11/16 in. I.D. , 9-1/2 in. tall
Thermocouple
well, 1/2 in. diam.
x 2 in. deep
Ta stirrer,
1/4 in. O. D. rod,
16 in. long, 3/4 in. diam.
impellers
spaced 1-1/4 in. apart
Ni adapter, 9/16 in. wide, 3/4 in.
long, 1/2 in. tall
Ni rod, 1/4 in. O. D“. , 10 in. tall
Ni filter tube for salt phase
samples,
5/16 in. O. D. , 1-1/2
in. tall, 5/16 in. I.D. , 1-1/4 in,
deep; frit dimensions
5/16 in.
O.D. , 1/16 in. thick
Ta rod, 1/8 in. diam. , 2-1/2 in.
tall
Ni rod, 1/4 in. diam. , 10 in.
long
Ta adapter tube, 3/8 in. O.D. ,
1/4 in. I.D. , 3 in. tall; milled
slot 3/16 in. wide, 2 in. tall
Ta sampling tube for metal phase,
1/4 in. O.D. , 1-1/2 in. long;
two milled slots 1/8 in. wide, 1/2
in. tall
Stainless steel furnace tube, 5 in.
O.D. , 4-3/4 in. I.D. , 20 in.
long
Stainless steel pedestal,
9 in.
tall
Stainless steel spacer,
4-1/2 in.
O.D. , 2-7/8 in. I.D. , 3-1/2 in.
tall
Ar inlet port
Fig.
1.
Equipment
10IF
7
9
10
3
5
for Distribution
-9-
6
—
-.
—
:---2%1
&
T
+’5
Studies
L
I
14
salt samples
were removed
as quantitatively
and were dissolved in 4~ HNO~.
(3)
radiochemically.
To conduct
an experiment
PuCl~ or AmCl~ concentration
the desired
The results
of approach
same results
Baker’s
pucl~.
from
the furnace,
tube head
with respect
and Pu and Am concentrations
when Am was transferred
from
from metal to salt phase).
. .
. . An equ.imolar
to
(i.e.
, the
salt to metal phase
Equilibrium
was
temperature.
mixture
of the salts was prepared
The PuC13 was prepared
by the hydrochlorination
by vacuum distillation
Ill . . . The Pu was electrorefined
RESULTS
The results
are given in Tables
of the distribution
grade metal.
of Am from
by the generalized
N~)
of Amz03 with La
AND DISCUSSION
experiments
at 698, 730,
and 775°C.
1, 2,, and 3.
The extraction
+
of
of the PuC13.
Am. . . The Am metal was obtained by the reduction
(4)
and distillation of the Am.
Am (1)
by
A. R. grade salts under vacuum.
PU2(CZ04)3, followed
(Pu phase,
or at a different
of Materials
NaC1-KCl.
represented
the Ni tubes
and the sampling
were shown to be reversible
in less than 1 hr. at a constant
Preparation
melting
temperature
the blank flange was removed
or when Am was transferred
achieved
at a different
of temperature
were obtained
from
and Am were determined
amount of salt or metal was added,
was installed.
direction
Plutonium
as possible
~ Puclx
x
(salt phase,
the metal into the salt phase can be
equation
(1)
N
Puclx
=
)
-1o-
Amcly
(salt phase,
(1.)
N
+
Amcly
x Pu (4).
x
) (Pu phase,
(1)
Nn)
,
/
Table
Distribution
Salt Phase
pU
in Salt,
wt.
%
2.14
2.20
2.29
2.61
3.04
5.44
5.62
6.08
6.76
9.78
11.20
I
of Am and Pu at 698°C.
- Equimol ar NaC1-KCl
PU
and ~
~
M.
in Salt,
% x 102
Containing
~
~.
in Metal,
% x 103
8.32
6,76
7.87
6.96
7.56
6.89
7.71
7.15
8.33
7.49
8.14
8.48
7.58
8.15
-11-
6,92
6.08
4.89
4.31
4.42
4.39
3.38
2.99
Table
Distribution
Salt Phake
Pu in Salt,
wt. %
2
of Am and Pu at 730°C,
- Equimolar ~aC1-KCl’ Containing
Pu and Am
,
Am in Salt,
wt. % x 102
Am in Metal,
wt. % x lo~
!
2.30
6.70
7.23
2.40
6.95’
7.57
2.66
7.’54
7.43
2.67
7.34
7.36
2.90
7.84 ‘
7.37
3,51
8;04
6.81
3.55
7.’99
6.84
3.72
8.26
6.35
4.78
12.0
8.41
5.52
8.28
4.84
5.66
7.58
4:83
5.88
8.06
4.86
6.06
7.99
4.83
7.01
6.78
3.72
7.80
8.64
4.40
8.13
7.58
3.96
8.22
8.88
4.71
-12-
Table
Distribution
Salt Phase
Pu in Salt,
wt. %
3
of Am and Pu at 775°C.
- Equirnolar NaC1-KCl
Pu and Am
b
in Salt,
wt. % x 102
Containing
Am in Metal,
wt. % x 103
2.15
6.53
8.34
2.28
6.57
8.17
2.51
7.20
7.42
2.56
6.83
7.44
2.58
6.85
7.34
3.76
10.7
9.05
3.88
10.2
9.01
4.56
11.7
9.38
5.27
8.00
5.40
5.78
7.11
4.68
5.89
5.02
3,73
5.98
7.29
4.70
7,81
7.36
3.89
8.56
6.96
3.82
-13-
The equilibrium
constant
N
for reaction
N;’$
‘Am
NY/x
Puclx
where N is the mole fraction
is essentially
y/x
yw
yAmcl
AmCl
K=
(1) can be written
y/x
‘Pucl
‘Am
and y is the activity
(2)
‘
x
coefficient.
The metal phase
pure Pu, so that N
PU=YPU=l”
The range of Am and AmCly concentrations
from -2 x 10-4 to -3
studied varied
x 10-4 for N*CI
and
Y
from-5
Therefore,
constant.
the activity
Further,
can be assumed
6
X
x 10-5 to-7x
10-s to 2
X
coefficients
to a first
to be nearly
10-2.
10-5 for Nh
.
of Am and AmCly
approximation
constant
should be essentially
the activity
coefficient
over the mole fraction
This is a reasonable
assumption
of PuClx
range studied,
since the activity
coefficient
of PuC13 has been shown to be constant in the LiC1-KCl system
.
over the PuC13 mole fraction range 6 x 10- 4 to 2 x 10-2. ‘5) Equation (2) can
therefore
be written
N
K’=~
‘Am
Amcl
NY/x
Puclx
With the aid of the IBM 7094 computer,
for each value of x and y from
Table 4.
In order
to observe
1 through 6.
which values
-14-
(3)
“
values
Typical
of K‘ were
results
calculated
are shown in
of x and y gave the most constant
.
Table 4
.
Equilibrium
Am+:
N X 102
Pucl~
Constants
at 7300C.
for
Puclx=Amcl
+~Pu
Yx
K’ x 102 for
x=3,
y=3
x=3,
y=2
0.658
4.03
0.755
0.688
3.83
0.727
0.764
3.82
0.751
0.767
3.74
0.737
0.836
3.67
0.744
1.02
3.36
0.729
1.03
3.29
0.716
1.08
3.50
0.774
1.41
2.99
0.721
1.64
3.10
0.788
1.69
2.77
0.711
1.76
2.82
0.733
1.82
2.73
0.718
2.13
2.60
0.720
2.39
2.49
0.719
2.50
2.35
0.689
2.53
2.29
0.674
-15-
the values
value of K’,
of K‘ for any particular
x, y set were normalized
by
.
dividing
each value of K’ by the maximum
value of K’ for that set.
ized values were then plotted as a function
A constant value of K’ would therefore
the y axis and would intersect
is sensitive
expected
PuC15-AmC15,
result
For example
PuC12-AmC12,
The same procedure
line plot parallel
to
The slope of the curve
almost
identical
PuC13-AmC13,
value of K’ was obtained
(x=6,
and(x=5,
y=4),
All previous
plots can be
PuC14-AmC14,
are given in the appendix.
data.
for the values
In all cases
the
(x = 3, y = 2),
y= 3).
studies
on this type of metal-salt
Pu is the only stable
measurement
at 730°C.
was used for the 698 and 775°C.
most constant
metric
Pu in the salt.
and PuCIG-AmCIG.
The 36 plots for the experiments
trivalent
in a sli’sight
the x axis at x = 1.0.
to the ratio of y and x.
for PuCll-AmCll,
of the weight percent
The normal-
Pu ion in equilibrium
system
have shown that
with Pu metal.
Potentio-
in LiC1-KCl
have shown that PuC13 is the only species
(5)
stable in the presence of Pu metal.
Anodic and cathodic efficiency
studies
(1)
in the electrorefining
process
have indicated that the electrode reactions are
~o
+
~+3
at the anode
(4)
pu+ 3 + l?u” at the cathode
and
In addition the phase diagram
for PU-PUC13
(6)
gives
.
(5)
no evidence
of a pu oxida-
tion state other than +3.
The only x, y set consistent
y=2.
Equation
(1) can therefore
Am ($ +:
with this information
be written
as follows
PUC13 (4) = Amc12 (4) + :PU(4
is the set x = 3,
for divalent
.
Am:*
(6)
.
*The conclusion that Am is present in the salt as divalent Am was first reported
by Leary and Mullins at the Symposium on Thermodynamics,
International
Atomic
Energy
Agency,
Vienna,
July 22-27,
-16-
1965. ‘7)
Values
775°C.
of K’ for reaction
are given in Table 5.
(6) for the experiments
The average
deviations
698°C. , +2. O% at 730°C.
, and +4. 1 % at 775°C.
the expected
deviation
experimental
AHO for reaction
(6) of -3.5
the presence
of divalent
Although all attempts
and
of K’ were *4.5%
These values
at
approximate
A plot of log K’ vs.
l/T
gives
a
kcal.
Since Am is the homolog
salts,
of 4%.
at 698, 730,
to prepare
of Eu and Eu is known to form
Am in the NaC1-KCl
divalent
salt is reasonable.
pure Am+ 2 compougds
~have been unsuccessful,
.,
the stabilization
of divalent Am in a CaF2 lattice has been postulated recently
(9)
by workers at the Lawrence Radiation Laboratory.
Single crystals of CaF2
containing
Optical
O. 1 - 0.2 wt. % AmF~ were reduced
absorption
disappearance
adsorption
spectra
of the crystals
electrolytically
at room temperature.
at 600°C.
.
showed the
of the Am+ 3 lines around 5000 ~ and the appearance
peaks which were attributed
to Am+ 2.
-i7-
of broad
(8)
?
.
Table
Equilibri
u.m Constants
5
for the Reaction
Am + : Pucl~ = Amcl~ + ; Pu
T$mp. ,
c.
K’ (Avg.
Dev. )
698
77.2
(+3.5)
730
73.0
(* 1.5)
775
67.6
(+2.8)
t
-18-
REFERENCES
1.
L. J. Mullins,
“Plutonium
Report
2.
Electrorefining,
LA-2666
L. J. Mullins,
Plutonium
Desigq
3.
K. W. R. Johnson,
Laboratory
J. A. Leary,
Laboratory
Chem. , @
7.
Plutonium
8.
Ener~,
9.
Geneva,
N. Edelstein,
of Divalent
of heri
Process
1759-1762
of Americium
LA-2992
CiLLmin
(1958).
Metal ~‘‘
(1963).
Properties
of Pu Compounds
Ag in LiC1- KC1 Eutectic,
“ Los Alamos
(1965).
“The Pu-PuCl~
!!Practical
Reactions
System, ” J. Inorg.
Atomic
P/833,
1955,
Nucl.
on Nuclear
Energy
Proc.
Intern.
f1 Symposium
Materials
Agency,
“Review
of Thermodynamics
1966,
of Americium
Conf.
on
and Atomic
Vienna,
Peaceful
to
Transport
Vol.
1, p. 462.
and Curium
Uses of Atomic
7, 355 (1956).
W. Easley
Americium
Application
at High Temperature,
and L. B. Asprey,
?’ Paper
Chem.
(1964).
International
Chemistry,
Report
LA-3399
with Emphasis
R. A. Penneman
Chem. , ~,
Pu Versus
L. J. Mullins,
Thermodynamics
~! Ind. Eng.
“Thermodynamic
J. A. Leary,
Process
in Solids,
I.
Report
103-105
J. A. Leary,
of Molten
1!Determination
?!PreParation
J. A. Leary,
K. W. R. Johnson,
Process,
Counting, “ Anal.
Scientific
G. M. Campbell,
Electrorefining
G. M. “Matlack,
from EMF Measurements
6.
Laboratory
, ~, 394 (1965).
by Gamma
Scientific
W. J. Maraman,
Scientific
!~Fused-Salt
by the LAMEX
M. S. Lew,
Los Alamos
5.
‘? Los Alamos
J. A. Leary,
and Develop.
J. Bubernak,
A. N. Morgan,
(1962).
and Its Alloys
Plutonium
4.
J. A. Leary,
and R. McLaughlin,
in CaF2 Crystals,
-19-
?!Formation
” J. Chem.
and Characterization
Phys. , ~,
3130 (1966).
.
#
.
APPENDIX
Plots of K’ /K;u
for the 730°C.
K’/K~=
.
distribution
.
as a function
experiments
of wt. % Pu in the salt phase
are given in Figs.
2 through 7.
is plotted on the x axis and wt. % Pu in the salt is plotted on the
y axis.
.
-20-
.
.—
—.
—
—.
— / /
-.
I
/
/
‘
/
1./1
—.
I
/
..
-P
g
G-
t?
_6J
{
G
z
I -–
-+F+--H’.
1. I
“ .l=la=Ln “
-21-
,
/
l.—
I
1
I
1
I
I
1
I
I
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