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after the l00hr test. The extent of the decarbu-
rization of the AIS1 1043 steel was greater in the
Armco iron container than in the stainless steel
container. Furthermore, sufficient nickel mass-
transferred to the surface of the steel specimen
in the stainless steel container to cause a phase
transformation to a depth of 2 to 4 mils, but the
amount of nickel that mass-transferred did not seem
to increase appreciably in comparison with the
amount transferred during the 100-hr test. Photo
micrographs of the as-received and as-tested AIS1
1043 steel specimens are shown in Figs. 3.2.18
and 3.2.19.
RARE-EARTH OXIDES EXPOSED TO STATIC
SODIUM IN INCONEL CONTAINERS
W. H. Cook
In considering rare-earth oxides as possible
control rod materials for the ART, sodium was
suggested as a heat transfer medium for cooling
the control rod material, and it was proposed that
lnconel be used as the container material for the
sodium and the rare-earth oxides, Tests were
therefore conducted to investigate the corrosion
PERlOD ENDING JUNE 10, 1956
resistance of the rare-earth oxides to sodium and
the effects, if any, on the lnconel containers.
One specimen of Sm203 (density, 5.88 g/cm3;
apparent porosity, 25.4%) was tested for 1000 hr
in static sodium at 1500'F in an lnconel capsule.
Two specimens from a body of a mixture of rare-
earth oxides (density, 6.58 g/cm3; apparent po-
rosity, not determined) were tested similarly, one
for 500 hr and the other for lo00 hr. The body,
fabricated from a commercially available powder
known as Lindsay Mix, obtained from the Lindsay
Chemical Co., had the composition 63.8 wt %
Sm203-26.3 wt % Gd203-balance primarily other
rare-earth oxides.
The results of the tests indicated negligible
corrosion attack by the sodium on the three speci-
mens and their lnconel capsules in lo00 hr, but
there may have been some reduction in their
strengths. The weight and dimensional changes
of the three specimens were all positive, as would
be expected with porous materials, and were less
than 0.5%. The original buff colors of the speci-
mens changed to gray black, but this was the
only macroscopically visible change. It was fwnd
Fig. 3.2.18. Specimens of AIS1 1043 Steel (a) in the As-Received Condition and (b) After Exposure to
Sodium in an Armco Iron Container for 400 hr at 1830'F. Etched with 4% picral. 200X. Reduced 10.5%.
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