TABLE 4—How Gamma Radiation Affects the Physical Properties of Organic Gasket Materials 
Breaking energy 
Gamma dose Specific gravity Tensile strength Shear strength Elongation (ft-lb per in. H.0 absorbed Haze Hardness 
(108r) (qm/em’) (103 ps7) (108 ps7) (%) of notch) (%) (%) (Rockwell R) 
Polyethylene 
0 0.914 1.56 1.89 325 11.2 0.026 172 —8.5 
1 0.920 1.64 1.81 28 5.6 0.035 1.83 14.3 
i) 0.921 1.90 1.91 U6 2.9 0.027 98 49.2 
Polyethylene, 1% carbon filled 
0 1.59 1.76 450 10.3 —6 
5 1.65 2.09 10-30 3.1 34 
10 1.80 2.15 10-30 2.9 66 
Polystyrene 
0 1.049 4.64 5.9 0.75 0.45 0.054 12.5 124 
0.01 4.2 5.5 0.78 0.29 124 
0.1 5.4 6.1 1.03 0.23 124 
1 1.051 3.3 5.6 0.45 0.30 0.089 8.3 122 
10 1.053 5.0 5.6 0.99 0.19 0.089 14.2 121 
Teflon 
0 2.14 3.76 3.01 175 2.65 0.0053 5.5 
1 2.21 Failed 0.483 Failed 0.37 0.014 14.6 
10 2.19 Failed 0.094 Failed 0.30 0.345 
Kel-F 
0 2.55 3.41 264 
0.01 2.40 3.65 230 
0.1 1.67 1.85 73 
1 Failed Failed Failed 
In most cases the greater stability of the process of its contamination. and then the solution was analyzed for 
coatings on concrete may be attributed 
to: (a) the greater chemical resistance 
of concrete to attack by gaseous and 
liquid decomposition products from the 
coating, and (b) the absorption of these 
products in the porous concrete struc- 
ture. In the case of vinyl coatings, the 
chemical attack that takes place is 
from halide acids. 
Of the 23 mounted coatings tested, 
only four polymer-base types did not 
fail at the maximum doses used: fu- 
ranes, epoxys, silicone-alkyds, and one 
modified phenolic specimen. Fight 
coatings that exhibit radiation stabil- 
ity, plus three examples of low-irradi- 
ated vinyl coatings and one neoprene- 
base coating, were tested for chemical 
stability and decontaminability after 
irradiation. 
Table 3 shows that six of the irradi- 
ated coatings are not resistant to the 
organic solvent hexone. In addition, 
several lacking solvent resistance also 
do not resist either acids or a base. 
Two other coatings, the vinyl-based 
Amercoat-33 and Corrosite-22, show 
good decontaminability but fail at 
higher gamma doses (2.4 & 108 r). 
The silicone-alkyd coating is difficult to 
decontaminate on concrete and fails 
on a steel-panel surface during 
Two types of coatings, one each of 
the furane-based and epoxy-based coat- 
ing (Alkaloy-550 and Epon-395), show 
excellent chemical resistance and de- 
contaminability. The other two coat- 
ings of similar polymer base, Duralon- 
36 and Epon-1001, both lack solvent 
resistance after irradiation. 
Gasket Materials 
Gasket materials were irradiated in 
leakproof containers lowered into a 
vessel surrounded by Co® slugs. 
Radiation intensity varied, but only 
the total dose of each specimen is re- 
corded in Table 4. 
In early tests, corrosive gases con- 
taining fluorine were detected being 
evolved from irradiated Teflon. Tests 
were made to determine the quantity 
of fluorine evolved from Teflon disks 
(1 in. dia., 1g in. thick) and Teflon 
molding powder during irradiation, the 
quantity of degraded fluorine within 
the irradiated disks that was released 
during the 30-day period immediately 
after irradiation, and the effects of 
these gases on stainless steel flanges 
carrying 50% HNO; solutions. To 
measure the quantity of fluorine 
evolved, the specimens were immersed 
in a NaOH solution during irradiation, 
fluoride content. No attempt was 
made to determine in what compounds 
the fluorine was evolved. 
In many cases only one reading could 
be obtained from each specimen; so 
several specimens were necessary for 
each series of tests. Since perfectly 
uniform specimens could not be ob- 
tained, only changes in properties that 
are greater than the variations in the 
specimens could be detected. 
Results. The most evident observa- 
tion is the difference between the radi- 
ation stability of halogenated polymers, 
Teflon and Kel-F, and nonhalogenated 
polymers, polyethylene and polystyrene 
(see Table 4). Both Teflon and Kel-F 
evolve corrosive gases and are degraded 
completely by irradiation to 108 r, while 
polyethylene and polystyrene appear 
very resistant to irradiation to and 
beyond this level. 
Polyethylene, polystyrene. The 
only major difference between the be- 
havior of polyethylene and polystyrene 
is the marked increase in the hardness 
of polyethylene after irradiation. 
Polystyrene is the most resistant gasket 
material tested and probably would be 
satisfactory for use at radiation levels 
up to 10°r. But the rate of hardening 
of polyethylene may limit its use to ra- 
105 
