Chemical problems in stable isotope separation

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MDDC 1087



UNITED STATES ATOMIC ENERGY COMMISSION







CHEMICAL PROBLEMS IN STABLE ISOTOPE SEPARATION


by
Arthur J. Miller
Boyd S. Weaver



Tennessee Eastman Corporation


Technical Information Division, Oak Ridge Directed Operations
Oak Ridge, Tennessee


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This document consists of 8 pages.
Date Declassified: May 23, 1947


This document is for official use.
Its issuance does not constitute authority
for declassification of classified copies
of the same or similar content and title
and by the same authorss.






I









CHEMICAL PROBLEMS IN STABLE ISOTOPE SEPARATION


By Arthur J. Miller and Boyd S. Weaver


The Development Division of the Clinton Engineer Works-Tennessee Eastman Corporation has
for more than a year utilized the electromagnetic method for separating the naturally occurring
isotopes of elements other than uranium. In this program the Division's Chemical Laboratories have
been engaged in preparing charge materials for the electromagnetic units, recovering, chemically
purifying, and analyzing the separated isotopes, chemically reconditioning the units, and preparing
mass spectrometer charges from the isotope concentrates for determinations of isotopic abundance.
To date, 19 elements have been processed and concentrates of 63 different isotopes made available
to the nuclear physicists and chemists of the Manhattan Project. Most of these isotopes are stable
or not radioactive. The concentrates are listed in Table 1. Isotopes of several of the 19 elements
and those of silicon, zirconium and antimony are in various stages of chemical purification.

'In dealing with charge materials for the electromagnetic separators, there are several factors
taken into account. Of considerable importance is the question as to whether the use of a given
material will supply fundamental information concerning electromagnetic operations. Next, for some
elements, it must be decided whether it would be advisable to prepare, at considerable expense,
compounds capable of satisfactory performance in existing unit'types or whether to modify equipment.
Problems in chemical reconditioning of the units such as toxicity of the charge, explosion hazards,
and corrosion of the units must also be considered.
Regardless of how these decisions are made, the charge material chosen is supplied conforming
as closely as possible to the following specifications:
1) That it can be volatilized at a controlled rate.

2) That it contains a minimum of impurities that will volatilize.
3) That it contains a minimum of impurities that will ionize.

4) That it contains a minimum of impurities whose isotopes are isobaric with those to be
collected.

To recover isotope concentrates as more or less pure chemical compounds of known composition
is an exercise in chemical ingenuity for each element. The problem generally resolves itself into one
of economically isolating minute quantities of the isotope from large amounts of other materials. The
extent of recovery is usually determined by balancing the cost of charge material and isotope sepa-
ration against recovery cost. For example, if 99.9% can be obtained with one-tenth the effort of
recovering the remaining 0.1% the processing will likely cease at such a point. Therefore, it is the
continuous responsibility of the chemists to devise low cost methods which provide a maximum of
recovery.

The chemical purity achieved is often influenced by the end usage planned for the individual con-
centrate. One requirement always considered is the necessity of minimizing impurities that contain
isobars of the element in order tW obtain a satisfactory isotopic analysis in the mass spectrometer.
Typical spectrographic chemical analyses are shown in Table 2.

The mass spectrometer charge usually consists of a portion of the isotope concentrate converted
to a compound suitable for spectrometer operation. To carry out the synthesis without loss of valuable

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material or contamination with undesirable impurities is another major chemical problem with each
element encountered.
Interest in most of the stable isotopes is still mainly confined to the field of nuclear research.
However, simplification and increased availability of methods for determining isotopic abundance
would make them invaluable as tracers in chemical experimentation.
The future program as outlined by Dr. C. E. Larson, Director of the Development Division, calls
for the eventual concentration of the isotopes of additional elements including those of the rare earths.


Spectrometer
charge






Charge
salvage


CHEMICAL
LABORATORIES


------------
Unit charge Prep-
aration
Chemical purification
Chemical analysis
Chemical
reconditioning
Mass spectrometer
charge preparation




Isotope
concentrates



I,


Unit
charge

Isotope
concentrates





Charge
salvage


Electromagnetic
separation
of
isotopes


MANHATTAN DISTRICT RESEARCH DIVISION
ISOTOPE BRANCH


Figure 1. Material flow in isotope separation.


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MASS SPECTROMETER
LABORATORY


-------------



Determination of
isotopic abundances








MDDC 1087


Table 1. Isotopic concentrates.

Abundance in Natural
concentrate abundance
Element Isotope (%) (%)


93.91
67.76
99.89
99.91
*

*

*1
*
*
*
*
*
*


99.93
0.16
88.36

99.95
99.97
*
*

73.76
98.80
88.59
61.0

55.47
42.85
61.06
83.03
98.41
98.70
98.62
97.42
21.10
56.13
73.01
69.63
22.0
*
*


N6.51
94.40
87.10


7.5
7.5
92.5
92.5

98.9
1.1

77.4
77.4
11.5
11.5
11.5
11.1
11.1
11.1

93.38
0.012
6.61

96.96
96.93
0.15
2.06

4.49
83.76
9.43
2.30

6.04
6.04
6.04
6.04
91.57
91.57
91.57
91.57
2.11
2.11
2.11
2.11
0.28
0.28
0.28

67.4
67.4
26.7
26.7


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MDDC 1087


Table 1. Isotopic concentrates. (Continued)

Abundance in Natural
concentrate abundance
Element Isotope (%) (%)


78.83
34.42
94.25
67.99
85.10
64.20

97.0
99.35
93.81
*
*
*
*
*



*
*

*
*


92.07
74.68
*
*
*
*
*


88.96
90.26
*
92.16
*
*

*
*


99.56
*
*
*


1.2
1.2
3.8
3.8
U.68
O.b8

70.13
70.13
29.87

50.9
27.3
3.9
17.4
0.5

48.0

50.6
49.4

0.56
9.86
82.56

22.0
9.4
16.1
16.6
9.65
24.1
9.25
9.25

51.9
51.9
48.1
48.1

1.4
13.0
12.3
28.0
7.3

4.5
95.5

1.1
5.5
6.8







MDDC 1087


Table 1. Isotopic concentrates. (Continued)
Abundance in Natural
concentrate abundance
Element Isotope (%) (%)

Pb 204 7.8 6.7
Pb 206 75.67 23.6
Pb 207 61.55 22.6
Pb 208 92.10 52.3

*Isotopic abundance not obtained to date.


Table 2. Chemical purity of typical concentrates.
Impurity Mrs Ca40 Cu"S Cu Zn" Cd"4 In"i

Ag N.D. N.D. 0.04% 0.06% <0.04% N.D. <0.04%
Al < 0.04% N.D. N.D. N.D. N.D. N.D. 0.08%
As N.D. --- N.D. N.D. N.D. ----
B N.D. N.D. N.D. N.D. N.D. N.D. N.D.
Ba --- N.D. --- --- --- --- ---
Be N.D. N.D. N.D. N.D. N.D. N.D. N.D.
Ca N.D. N.D. N.D. N.D. N.D. N.D.
Cd N.D. N.D. N.D. N.D. N.D. N.D.
Co N.D. N.D. N.D. N.D. N.D. N.D. N.D.
Cr N.D. N.D. N.D. N.D. <0.15% N.D. N.D.
Cu 0.04% N.D. <0.04% < 0.04% < 0.04%
Fe 0.08% 0.08% < 0.04% 0.04% N.D. N.D. 0.08%
In N.D. N.D. N.D. N.D. N.D. N.D.
K --- N.D. -- --- --- ---
Li N.D. N.D. N.D. N.D. N.D. N.D. N.D.
Mg 0.04% < 0.02% < 0.02% <0.02% N.D. 0.02%
Mn N.D. N.D. N.D. N.D. N.D. N.D. < 0.04%
Mo N.D. N.D. N.D. N.D. N.D. N.D. N.D.
Na < 0.08% N.D. N.D. N.D. N.D. N.D. N.D.
Ni N.D. N.D. <0.08% N.D. N.D. N.D. N.D.
Pb N.D. N.D. N.D. N.D. N.D. N.D. N.D.
Pt < 0.15% --- N.D. N.D. N.D. --- ---
Rb --- N.D. --- --- --- --- ---
Si 0.05% 0.05% <0.05% 0.05% <0.05% < 0.05% 0.31%
Sn N.D. N.D. N.D. N.D. N.D. <0.08% N.D.
Sr -- N.D. N.D. N.D. N.D. N.D. <0.11%
Ti N.D. N.D. N.D. N.D. N.D. N.D. N.D.
V N.D. N.D. N.D. N.D. N.D. N.D. < 0.08%
Zn N.D. N.D. N.D. N.D. 0.15% N.D.
Zr -- N.D. N.D. N.D. N.D. N.D. N.D.

N.D. Not detected spectrographically
< Detected but below limit of determination
--- Not determined


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MDDC 1087









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