diation dosages of about 10° roentgen. 
Since inorganic fillers often make or- 
ganic plastics more resistant to radi- 
ation, a 1 %-carbon-filled polyethylene 
was tested to compare this material 
with natural polyethylene. But no 
difference in stability could be detected. 
Corrosive gases. Corrosive gases 
evolving from gaskets during irradi- 
ation not only indicate deterioration of 
the gasket, but the gases also may dam- 
age flanges or other equipment. No 
evolution from Teflon is detected at 
radiation levels less than 10° r (see 
Fig. 1). The appreciable quantity of 
fluorine given off by the Teflon disks 
during the 30-day period after irradi- 
ation and the difference between the 
quantity of fluorine evolved from the 
disks and the molding powder show 
that released fluorine is accumulated 
within the specimen before diffusing 
through the surface. Data on halide 
evolution from polymonochlorotriflu- 
oroethylene and more complete data 
on changes in the physical properties of 
Kel-F are reported elsewhere (1). 
Flange corrosion. Figure 2 shows 
how these gases affect stainless steel 
flanges immersed in 50% HNO;. A 
light brown area is noted on the flange 
where the steel had been in contact 
with Teflon. Microscopic examination 
reveals masses of tiny pits; all other 
surfaces of the flange remain as 
bright as before the test. Control 
specimens of stainless steel in the 
gamma field (without contact with 
Teflon) were corroded by 50% HNO; 
atarate less than 1 mil/yr. No differ- 
ence could be detected between the 
corrosion rates of the control specimens 
with and without irradiation. 
Hycar, silicone rubber. As shown 
in Table 5, the elastomeric properties of 
Hycar and silicone rubber are stable at 
radiation levels not greater than 107 r. 
However, between 107 r and 108 r there 
are considerable changes in the proper- 
ties of both materials, largely embrittle- 
ment processes. After 10% r both types 
of silicone rubber deteriorate to a mate- 
rial with approximately the same me- 
chanical properties. 
Asphalts and Tars 
The need for a cheap method of in- 
definitely storing radioactive waste 
solutions resulting from the reprocess- 
ing of spent reactor fuels prompted an 
investigation of impervious lining 
materials for earthen basins. Asphalts 
and tars, because of cheapness and ease 
106 
TABLE 5—How Gamma Radiation Affects Gasket Materials 
Hardness 
Gamma Tensile strength Elongation 
dose (% 
(r) (108 pst) (% change) (%) (% change) (Shore) change) 
Silicone 12602 
0 0.277 58 62 
104 0.245 —12 50 —l4 65 4.8 
10° 0.260 — 6.1 62 6.9 66 6.5 
10° 0.282 1.8 25 =o 74 19 
108 0.151 —46 5 —91 95 53 
Silicone 12603 
0 0.555 36 84 
104 0.540 iL, 36 0 84 0 
108 — _— —- = 85 1.2 
107 0.528 — 4.9 25 —3l 87 3.6 
108 0.135 —76 5 — 86 86 2.4 
=—_—_~ —_— =—_—— —__. 
{ B A B B 4 B A A 
Hycar OR-25* 
0 2.74 2.26 275 «365 72 
104 1.88 2.33 —32 3.1 230 371 —16 1.6 77 6.9 
106 2.42 2.40 —12 6.2 255 358 -— 7 — 1.9 78 8.3 
107. 2.59 2.64 — 5 17 208 185 —24 —49 81 13 
108 1.63 2.04 —40 — 97 35 32 -87 —-9I1 92 28 
Hycar PA-21* 
0 teeta, ah aby¢ 190 145 7A 
104 1.29 1.40 — 5.1 —ll1 155 130 —18 —10 70 — 1.4 
10° 1.33 1.40 -— 2.2 —-11 150 130 —21 —10 73 — 2.9 
107): 11.838 1.88 -— 2.2 —12 135 106 —29 —27 72 14 
108 0.81 0.97 —40 —38 50 41 —74 —72 80 13 
* Two series of tests (A and B) were made with these materials. 
of application, were selected for tests 
of radiation damage and chemical 
resistivity. 
As shown in Fig. 3 and Table 6, 
asphalts and tars retain their ductility 
and are hardened (but not excessively) 
with increasing exposure up to 10° r 
total dose. From the slopes of the 
lines, there is evidence that excessive 
hardness may occur at 10!° r. 
Asphalts and tars evolve gases (prin- 
cipally hydrogen) during irradiation. 
The asphalt assumes a vesicular or 
honeycombed structure of individual 
cells that probably would not develop 
leaks in actual service. Irradiated tars 
exhibit this structure to a slight extent. 
Both are adequately resistant to neu- 
tralized radioactive wastes up to 200° F, 
but attack by acid wastes is severe. 
Thus, asphalts and tars (if a suitable 
cheap radiation-resistant reinforcing 
material for the tar can be found) can 
be used to contain radiochemical 
wastes in earthen basins if: (a) the total 
dose does not greatly exceed 10° r, (b) 
the wastes are neutralized, and (c) the 
temperature of the stored waste is 
not permitted to rise above 200° F. 
It is estimated that an earthen basin 
of 108 gal capacity can be constructed 
with a 19-in.-thick asphalt lining, cov- 
ered with 2 ft of compacted earth and 
complete with roof, for 3-5¢/gal of 
stored waste. 
lon Exchange Resins 
Preliminary work has established the 
order of magnitude of radiation damage 
to ion exchange resins as shown by a 
loss in capacity. While the capacity 
loss is possibly the most important fac- 
tor in the use of ion exchange resins for 
radiochemical processing at high activ- 
ity levels, other effects that must be 
considered include changes in the physi- 
cal and chemical character of the mate- 
rial. Figures 4 and 5 show the effect of 
Co® gamma rays on the capacity of 
Dowex A-1 anion exchange resin and 
on Dowex 50 cation exchange resin as 
a function of the energy absorbed. A 
third resin, Dowex 30, a sulfonated 
phenolic cation exchange resin, shows a 
capacity loss of only 1% per watt-hr of 
energy absorbed per gram as compared 
