i — ———————————————————————————————— 
TABLE 6—How Gamma Radiation Affects Coal Tar Products * 
Characteristic Roofing pitch W.G. millwrap enamel 
Gamma dose, r 0 5 xX 108 0 tye. 1) 
Softening point (ASTM D836), °F — — 199 203 
Softening point (ASTM D61), °F 158 161 —_ — 
Penetration at 77° F, 100 gm, 5 sec, 
mm/10 5.5 5 9 8.5 
Penetration at 32° F, 200 gm, 60 sec, 
mm/10 0 0 1 1 
Penetration at 115° F, 50 gm, 5 sec, 
mm/10 84 70 26 24 
Ductility at 77° F, 5 em/min, em 67 17.5 2 2 
Ductility at 90° F, 5 cm/min, em — — — —_— 
0.08 1.04F 30.7 28.2 
Ash, % 
Pipeline enamel Waterworks enamel 
0 5 X 108 0 5 X 103 
192 197 237 248 
169 168 — = 
0 0 15 7.5 
0 0 5 0.5 
1.5 a) 31 22.5 
0 0 3 Io 
1.5 1 — == 
167.9 16.8 29 29 5 
* Test specimens supplied by the Barrett Div. of Allied Dye and Chemical Corp., Edgewater, N. J. 
+ Similar to ferric oxide residues, probably due to metallic contamination. 
a yaE EE EyE ESSE SSS SSSISS 
to the losses of 15-40% for Dowex A-1 
and Dowex 50. The variations in 
capacity loss demonstrate that radi- 
ation damage can perhaps be minimized 
with the proper choice of resin, pro- 
vided that the chemical stability of the 
resin is satisfactory (2). 
Decomposition of Dowex 50W resin 
by alpha bombardment is observed 
when Am2!! is isolated and concen- 
trated by cation exchange. During 
loadings of about 0.5 gm Am per liter of 
resin; darkening, presumably charring, 
of the resin bed is observed within 24 
hr (3). But this phenomenon does not 
deleteriously affect the cation-exchange 
procedure. 
Resin Capacity (%) 
Radiation Energy Absorbed 
(va. f= hr/gm) 
FIG. 4. Capacity loss of Dowex A-1 
anion-exchange resin (quaternary amine 
polystyrene) caused by Co®’ gammas 
FIG. 5 (right). 
Aqueous Solutions 
The chemical effects produced by 
ionizing radiations on aqueous solu- 
tions can be divided into two parts: (a) 
indirect action of H and OH radicals 
formed by water decomposition react- 
ing with solute particles and with one 
another, and (b) direct action of radi- 
ation on solute particles followed by 
chemical change. The primary mecha- 
nism of water decomposition is 
H.O > H + OH (1) 
2H.O 2. H, ae H,0, (2) 
The radicals H and OH are available 
for reaction with solutes or with one 
another to form H. and H.O». In 
“Bo 
= 
oO 
Resin Capacity (%) 
o 
° 
an 
o 
40 
Radiation Energy Absorbed (watt-hr/gm) 
Effect on Dowex 50 cation-exchange resin (sulfonated polystyrene) 
regions of low ionization density, most 
radicals react with solutes, while in 
regions of high ionization density, radi- 
cals recombine to form the products 
shown in Eq. 2. Since H, OH, H2O., 
and the intermediate perhydroxy radi- 
cal HO» are either strong oxidizing or 
reducing agents, oxidation or reduction 
reactions occur with many of the solutes 
present. In the direct absorption of 
radiation by the solute, oxidation or 
reduction results, since electrons are 
transferred or removed in the process. 
Chromium’! ions, for example, are 
reduced to trivalent chromium in acidic 
acetic acid-sodium acetate buffered 
solutions when subjected to intense 
gamma radiations. The reduction rate 
of a 0.5 M chromate solution buffered 
with 4.0 M acetate is 2.35 + 0.15 milli- 
moles/keal at pH 4 in a gamma field of 
about 10’ r/hr. The decomposition 
rate is reduced to 0.51 + 0.15 milli- 
moles/keal by the addition of 0.56 M 
sodium bromide as a “protector”’ (4). 
* * * 
The authors wish to acknowledge the assist- 
ance of the following in carrying out the 
radiation-damage test program for protective 
coatings and gaskets: A. J. Hotberg, Lion 
Oil Co., a division of Monsanto Chemical 
Co.; G. A. West, F. L. Rogers, G. R. Guinn, 
R. J. McNamee, Union Carbide Nuclear 
Co. (ORNL); M. Tyner, Jr., Univ. of 
Florida; J. N. Hunsberger of E. I. du Pont 
de Nemours & Co.; and the various com- 
panies that supplied specsmens. 
BIBLIOGRAPHY 
1, Ind. Eng. Chems 46, 2549 (1953) 
. G. I. Cathers, ‘‘ Radiation Damage to Radio- 
chemical Processing Reagents,’’ Paper 584, 
Geneva Conference on Peaceful Uses of Atomic 
Energy (1955) 
3. R. H. Rainey, ORNL, personal communica- 
tion (1956) 
4. R. L. Andelin, E. 
(1955) 
© 
L. Anderson, IDO-14347 
107 
