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NOV 1 3 196, FFECTS OF G
OG EFFECTS OF GAMMA RADIATION ON CATION EXCHANGE RESIN IN
A FLOWING WATER SYSTEM •
utura, ne Árss
MASTER
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W. C. Yee and W. Davis, Jr.
+
Oak Ridge National Laboratory
Oak Ridge, Tennessee
-LEGAL NOTICE -
Momoport mo popard un account of Governoet sponsord work. Mether the valued
mens, mar the Commission, nor meg perman acting on baball of the Counselon:
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*Research sponsored by the U. S. Atomic Energy Commission under contract with the
Union Carbice Corporation.
Submitted for presentation at the American Nuclear Society Winter Meeting, San Francisco,
California, Nov. 30-Dec. 3, 1964.
Paper sponsored by ANS member, R. E. Blanco of Oak Ridge National Laboratory.
ABSTRACT
Prolonged exposure of cation exchange resin in the hydrogen form to gamma-radiation
and flowing water caused more drastic changes in the chemical and physical properties of
the material than has been reported by other investigators for resin exposed to like dosage
in a static system. After a dose of 0.75 x 109 rads in a dynamic system, the rate of loss of
strong-acid capacity was 20 to 25% per whr per gram of dry resin, compared with the 4%
and the 10 to 20% found by others for the static system. Also, de-craslinking of more than
4% of the resin matrix accompanied this loss of capacity, compared with the more moderate
de-crosslinking or even additional crosslinking reported for the static system.
Camma radiation also caused gas evolution, bead swelling, and produced a weak-acid
capacity in the resin equivalent to 3 to 5% of the original strong-acid capacity.
Decomposition products included soluble sulfuric, sulfonic, and oxalic acids, and
insolu s bits of resin. The G(-s) value was estimated to represent 1.0 to 1.2 otoms lost
per 100 ev of energy absorbed.
.
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Although ion exchange is widely used for decontaminating waste waters and
separating and purifying radioactive nuclides, the limitations imposed by radiation
damage to organic resins are poorly defined. Previously reported work has dealt with
resin exposed under a variety of conditions: the "bone-dry" state,'," the "moist,"
air-dried state, (2-0) and the completely wat, swollen stato. 1o.1 In addition, all
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reported exposures were made in quiet water, which permitted the accumulation
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** --. ...
min.:
of degradation products formed during irradiation. Changes induced under these cir-
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cumstances would not necessarily cpply to processing conditions where, typically, resin
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is submerged in a flowing aqueous stream which would remove some of the degradation
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products.
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The object of this work was to study the changes in resin properties under simulated
conditions of processing by exposing a fixed bed of cation-exchange resin to cobalt-60
.
...
...
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.
gamma radiation and flowing water.
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EXPERIMENTAL
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Materials.
The cation exchange resins Dowex 50W of 8%, 12%, 16% and 20%
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crosslinkage, and Amberlite 200, a highly ci'osslinked yet porous material (macroreticular),
were tested. Before irradiation, each sample was converted to the hydrogen form by treatment
with caustic, ethyl alcohol, nitric acid, and demineralized water in the usual way.
Procedure. In each experiment, 30 ml of resin in a stainless steel cylinder was inserted
0.012 watt per gram of dry rosin. The apparatus is sketched in Fig. I. Demineralized water of
.
22
ii
less than one micromho/cm specific conductance was pumpad downward through the resin
column at a linear flow rate of 1 cm/min (4 ml/min). The superficial holdup time of the
5
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INCLASSIFIED
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SEINE-FRITTED
GLASS DISK
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ASCARITE
TUBE
CONDUCTIVITY
CELLS
DYED
ANION
RESIN
COLUMNK
tro..aniveintest mot too. v:
ZERO-MAX
SIGMA PUMP
FLOW
METER
CATION
RESIN
COLUMN
DEMINERALIZED
WATER SUPPLY
.
.....
COBALT-60
..,
SOURCE
EFFLUENT
COLLECTED
Fig. 1. Flow Diagram of lon Exchange Resin Radiation Experiment.
3
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---...m..
..
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1
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water was estimated to be 7 min. Outside of the radiarion field and in sequence, the
colunin effluent was (1) passed through a sintered-glass disk to remove entrained particles,
(2) monitored continuously for pH and specific conductance, (3) passed through a dyed bed
of anion resin in the hydroxyl form to sorb radiation degradation products, and (4) finally
collected for analysis.
Analyses. The chemical and physical properties of the resin samples were measured
before and after exposure to radiation. Resin capacity was determined by titration to pH 7,
using a glass electrode, and by sulfur analysis. Water content was determined by removing
the excess water by centrifugation and then drying the resin that thus contained only interstitial
water; 12-hr in a vacuum oven at 50 to 60°C was sufficient. The collected effluent solution
of euch run was coricentrated about fiftyfold in an especially designed vacuum-distillation
system ) at 10 to 15°C. This concentrate and the caustic eluant from the dyed anion column
were analyzed by wet chemical and several instrumental methods in an attempt to identify
the products of resin degradation.
RESULTS AND DISCUSSION
Exposing the carion exchange resin to gamma-radiation changed both the chemical
and physical properties. After a dose of 0.75 x 10' rads (2 whr per gram of dry resin), Dowex 50W
resin lost 10 to 20% of its original weight and 40 to 50% of its strong-acid capacity, the less-
crosslinked resin losing more of each (Table 1). A weak-acid capacity of 3 to 5% of the original
strong-acid capacity was also acquired. After 3.9 ~ 10' rads, (10.6 whr per gram of dry resin),
the 8%-crosslinked resin lost more than 90% of its original weight and 98% of its strong-acid
capacity. The macroreticular resin, Amberlite 200, showed a 13% weight loss and a 43%
strong-acid capacity loss after 0.97 x 10"rads; this is comparable to the performance of a
conventional 160 or 20%-crosslinked Dowex 50W resin after an exposure of 0.75 x 10° rods.
.
Table 1. Prolonged Exposure of Cation Exchange Resins to Gomma-Radiation Causes Loss in Weight, Loss of Strong-Acid
Capacity, and produces Weak-Acid Capacity
Original Resin
Crosslinkage Strong Acid
Capacity
Mesh Size
(meq/dry g)
Gamma
Rodiation
Dose
(px 100%
and
Content
(wo %)
Exposed Resin
Weak-Acid
Capacity
(meg/dry g)
Mass
Loss
(wt %)
Streng-Acid
Capacity
(meq/dry g)
Sulfur
Conteni
(wt %)
GT-S)
atom lost
100 ev sorbed
4.80
15.4
3.18
0.25
Dowex 50W X-8
(20-50 mosh)
13.7
1.0
4.85
14.9
Dowex 50W X-12
(20-50 mesh)
3.38
4.81
0.02
15.5
Dowex 50W X-16
(20-50 mesh)
3.47
Dowex sow x-12 1.6
Dowex sow X-16 4.81
- 459
4.97
Amberlite 200 5.00
0.77
0.75
0.7
14.9
5.5
14.2
15.7
14.8
10
is
3.47
3.27
4.59
Dowex 50W X-20
(20-100 mesh)
14.2
3.27
129
4.97
15.7
1.88
Dowex 50W X-8
(20-50 mesh)
5.00
14.8
0.97
13
3.30
(16-50 mesh)
Only strong-acid capacity determined.
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A comparison of the capacity data of this work for Dowex 50W rosin with those
reported in me literature for comparable radiation dose indicates that the rate of loss
is greater when the solutions flow through the rosin bod. Utley) reported that the loss
rate for air-dried resin expaved in a static system was about 4% per whr per gram of dry
rosin for a dose of 0.9 x 10' rods. For resin submerged in a sealed tube of stagnant water
and exposed to 0.38 x 10' rads, Higging, reported a loss rate of 10 to 20% per wit per
gram of dry rosin. In the flowing-water experiments reported here, the capacity loss rate
was 20 to 25% por whr per gram of dry resin for an exposure of 0.75 x 10' rads.
Sulfur analysis of the resin samples exposed to 0.75 x 10° rads showed that 20 to 25%
more sulfur remained on the resin matrix thon would be indicated by the active sulfonate
groups as determined by titration (Table 1). On the basis of the sulfur analysis, the average
rate of loss of sulfur during exposure, G(-s), was estimated to be 1.0 to 1.2 atoms per 100 ev
of energy absorbed.
Gamma radiation darkened and swelled the resin beads. After 0.75 x 10' rads, the
increase in particle size of Dowex 50W resin beads varied inversely with the degree of
crosslinkage, ranging from a 25% increase for 8%-crosslinked resin to no detectable change
for the 20% resin (Fig. 2). Optical microscopy studies (10x) of the wet, swollen resin after
IN
exposure showed no fissuring or fragmentation similar to that reported for resin exposed in the
air-dried state. Despite the swelling, there was an overall 1 to 10% decrease in resin
5
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volume due to a 10 to 20% loss of weight.
mu
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Data on moisture content and capacity loss show that de-crosslinking of the resin matrix
occurred during exposure of the material in a flowing stream of water (Table 2). It was
TO
estimated that the number of interstitial water molecules retained per sulfonate (-SOZH)
group remaining on the resin after 0.75 x 10° rads averaged 120% greater than that for the
11
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23.
UWCL ASHFIED
ORMLOL toma mno
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ORIGINAL
... IRRADIATED
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DOWEX 50W *•8
(20.50 mesh)
0.76 X10 r.
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ORIGINAL
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படபடபடபடபடபடபடபடபடப


DOWEX SOW X-12
(20-50 mesh)
0.77 X10ºr
IIIIIIIIIIII
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PARTICLE SIZE , mm
to is
--
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ORIGINAL
• • IRRADIATED
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DOWEX 50W X-16
(20.50 mesh)
0.75 X 10ºr
لللللللللللللللللللللللا
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ORIGINAL
--- IRRADIATED
-
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DOWEX SOW X-20
(20-100 mesh)
0.77 X 10ºr
wei
PARTICLES OF SIZE LESS THAN THAT INDICATED, '%
-
Fig. 2. The Increase in Moon Particle Size of Wat, Swollen Resin was Most
Noticeable on the least (8%) Crosslinked Resin.
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1
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--...
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... .--.--
the new
MOT
Tablo 2. The Matrix of the Carion Exchange Rosin Dowex 50W Do-craslinks Whon Exposed
to Gamma Radiation in a Flowing Stream of Water
ORNL.LR. DWG ??
132
Woler Rotention
Water Content
Moleculo
Thoroolo
Crocslinkage Rodlollon Orom Mo Sirona Aold Copoally
ove to lower
Doro gram ury on (mog por dry gram 1.303 Group Croolinkage due to
Mark Sluelew 10° Innar Winot Talitatinal a n el of Oriminal Rain Irrallation
m 2.76 1.01 1.54 4.0 3.2 11.7 27.1
en 0.7 0.60 1.20 4.6 2.4 m2 20.
126
(20 mod
want 0.7 0.74 1.20 4,6 3,5 RO 20.5
(20- moto
am 0.93 0.72 . 3.J
12.2
120-100 mosh)
medioned in a co gommoadiation Mold of 0.017-0.013 woln per gram of dry moslim.
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per arampla, 1000 meter).
o per compra, 100-12..2m
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original materials. For unexposed resins, this ratio showed a maximum increase of only
30% for each 4% decrease in crosslinkage. The loss of polar sulfonate groups during
irradiation would tend to reduce the water content of the resin. Thus, the observed in-
crease in water uprake is attributed to decrosslinkage of the resin matrix of more than 4%.
Other investigators have reported both additional crosslinking and moderate decrosslinking
at comparable dosages for resin exposed statically in the air-dried state. Utley) found
additional crosslinking after 0.44 x 10' rads; that is, a decrease in the water retention ratio
of 16% for both 8- and 12%-crosslinked Dowex 50W rosin. Data reported by Fisherla) and
by Smith and Grohl show that de-crosslinking occurred in each of their experiments, the
ratio increasing about 40% after 0.22 x 10' rads for Amberlito IR-120 (8%-crosslinked cation

resin) in the former case and, in the latter caso, increasing 80% after 0.28 x 109 rads for
12%-crosslinked Dowex 50W. The greater increase in water retention fas high as 138%)
observed horo implies that de-crorslinking plays a major role in the damage reported for
resin used in radiochemical processing. Apparently, when a resin bed is exposed to both
gamma-radiation (from fission products) and to a flowing aqueous stream, the crosslinks are
severed, resulting in detrimental effects such as (1) resin dissolution and capacity loss and
(2) the introduction of soluble and insoluble contaminants into the eluted products.
The effluent of each of these experiments contained yaseous, soluble, and insoluble
products of resin decomposition. The gaseous and insoluble products were not identified,
.but ultracentrifuge and light-scattering studies did indicate that the solids suspended in
solution had a density of 1 and a molecular weight of several million.
The dissolved products were acidic, as shown by the continuously recorded pH and specific
conductivity data (Figs. 3 and 4) and included sulfato, sulfonate, and oxalate ions, as identified
>
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8.A
-
TE
2
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2
UWCL ASHPIED
ORAL L Rooma. 05715

-
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2
-"
Influent Liquids Deminerolizod Worer
pH > 6.5
micro mho
Specific Conductance simo
см
~ 4 ml/min (1 cm/min)
Crosslinkage: A • 8% Crosslinked, 20-50 mesh
B. 12% Crosslinked, 20-50 mesh
C. 16% Crosslinked, 20-50 mesh
D - 20% Crosslinkod, 50-100 mesh
-
-
-
-
-
-
-
-
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PH OF EFFLUENT
n
TRA
jou Jo
2-
$
*
*
*
ih:
1 750
do
00
OSUREME bratres
0.4 0.5 0.6 0.7 0.8 ola
GAMMA-RADIATION DOSE (rads x 100%
Fig. 3. The Acidity of the Soluble Products of Dowex 50W Resin Decomposition Decreases
with Increasing Radiation Dose.
.
*
TT 1
-
*
1
UNA ASHPIED
OH-LA-owa OSN4

Icm
· Oscio
SPECIFIC CONDUCTANCE OF EFFLUENTIIum
cm
Influent Liquid: Demineralized Water
pH > 6.5
Specific Conductonces, micro mho
~ 4 ml/min (1 cm/min)
Crosslinkage: A - 8% Crosslinked, 20-50 mesh
8 - 12% Crosslinked, 20-50 mesh
C • 16% Crosslinked, 20-50 mosh
D - 20% Crosslinked, 50-100 mesh
:
.
1
Gamma Rodralen Dose I radsxio
-1.
GAMMA-RADIATION DOSE (rads x 10-9
150*
.
*.
.
2
Fig. 4. The Specific Conductance of the Soluble Products of Dowex 50W Resin Decomposition
Docreases with increasing Radiation Doce.
CY
"
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---------
--------------
1
WE
8-8
.
.
.
E
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by wet chemistry and paper chromatography. A comparison of reportedly!) and
experimental specific conductance data indicates that the concentration of acid in the
is
.
offluent was about 10
m, in agreement with the observed pH data. Starting with a
maximum specific conductance of about 400 pmho/cm and a minimum pH of 2.7, the
acidity decreased with increasing radiation dose. About 75% of the solublo sulfur in the
offluont was in the form of sulfata.
ACKNOWLEDGEMENT
We are indebted to H. Kubota, W. R. Laing, 1. Willmarth, and J. S. Johnson for their
analytical and interpretive assistance, and to J. T. Roberts for his helpful discussions with us.
Our thanks go to Dow Chemical Company and Rohm and Hoas Company for supplying compli-
mentary samples of Dowex 50W and Amberlite 200 resins, respectively.
-
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2
.
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REFERENCES
1. K. A. Nater, Atoomenergie 4, 155 (1962).
2. S. A. Fisher, USAEC report RMO-2528 (1954).
3. R. E. Wedemeyer, Ph.D. thesis, Vanderbilt University (1953).
4. J. Payne, M.A. thosis, Vanderbilt University (1956).
5. J. W. Utley, Ph. D. thesis, Vanderbilt University (1959).
6. L. L. Smith and H. J. Groh, USAEC report DP-549 (1961).
7. I. R. Higgins, USAEC report ORNL-1325 (1953).
8. R. H. Stevens, USAEC report K-1594 (1964).
9. M. Hlasko and A. Salitowna, Bull. Intern. Acad. Polonaise., Classe Sci. Math Nat. 1035A,
189 (1935).
10. H. H. Jeffery and A. I. Vogel, J. Chem. Soc. 1932 , 400 (1932).
11. L. S. Darkin, J. Am. Chem. Soc. 63 , 1007 (1941).

FEL
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DATE FILMED
0 / 1865
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LEGAL NOTICE
Tt
The
1
2
**
This roport me proporod as un account of Govorament sponsored work. Noithor the Unitod
Blatos, por the Commission, nor any person acting on bosall of the Commission:
A. Makos any warranty or roprosentation, exprossed or implied, with rospoct to the accu-
racy, complotonesı, or usefulness of the information containod in this roport, or that the uso
of any information, apparatus, molhad, or procons disclosed in this roport may not Infringe
privately ownod rights; or
B. Assumos any liabiliuos with rospect to the use of, or for damago, rosulting from the
use of any information, apparatus, motbod, or process disclouod in this report.
As used in the abovo, “por son acting on behall of the Commission" Includes any em-
ployoo or contractor of the Commission, or omployuo of such contractor, to the extent that
such omployoo or contractor of tho Commission, or omployoe of such contractor preparos,
disseminates, or provides accoss to, any Information pursuant to his omployment or contract
with the Commission, or his omployment wils such contractor.
s
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