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ANP PROJECT QUARTERLY PRQGIXSS HEPORT
TABLE 11.9. RESULTS OF TEmPERATURE-DERENDENCE TESTS OF TYPES 304 AND
316 STAINLESS STEELS EXPOSED IN NaOH FOR 100 HOURS
_.___ ...... ~ ^._... _____ _-- ___ ......... -
.- ~ ____ _ _ _ _ ____
MATERIAL
TEMPERATURE ( OC)
METALLOGRAPHIC NOTES
. ._ _._.
Type 304 stainless steel
Type 316 stainless steel
- .....--- ~-
3 50
450
5 50
6 50
3 50
4 50
5 50
weight and dimensional changes listed
in the following:
BEFORE TEST AFTER TEST
Length, in. 0.486 0.413
Width, in. 0.263 Q. 207
Thickness, in. 0.269 0.213
Weight, g 1.5254 0.6882
Metallographic examination of the
Inconel tube used in this test revealed
a 4 to 10-mil oxide layer.
Nickel in NaOH Under Hydrogen
Atmosphere. Maintenance of a hydrogen
pressure from an external source has
been shown to minimize corrosion and
mass transfer of nickel in NaO11.
Maintenance of an atmosphere of hydrogen
in components of a high-temperature
reactor would introduce a number of
problems; however, the prospect of
containing hydroxides in this fashion
has appeared sufficiently promising to
justify systematic study of this
possi bil i t y.
In the experiments, sodium hydroxide
containing less than 0.1% Na,CO, and
less than 0.1% H,O was used, and all
handling of the material was conducted
in a dry box that could be evacuated
and flushed with pure, dry helium. The
142
No attack
No attack
_.__.__.._I
Light intergranular penetration
of 1.2 to 1 m il
Unattacked material decreased
from 34 to 24 m i l s
No attack
No attack
Intergranular attack of 1 t o 2
mi 1 s
metal to be tested was heated for 30
min at 800°C in pure flowing hydrogen
and subsequently handled so that the
inner surface of the tube was exposed
only to pure helium before the corrosion
test. The hydrogen used in these
experiments was purified by passage
through a "Deoxo" catalytic mass. The
water was removed by liquid-nitrogen-
cooled traps and by magnesium per-
chlorate.
In one type of test, the movement
of hydroxide was achieved by thermal
convection in a single 1/2-in.-dia
tube inclined at 45 deg and heated to
800°C at the bottom. A temperature
gradient of about 200°C was maintained
between the top and bottom of the
hydroxide that filled the 18-in. tube
to a depth of about 12 inches.
Tubes of nickel were placed in an
outer jacket of stainless steel designed
to contain the furnace assembly so that
the hydrogen can bathe the outside
walls as well as the contents of the
tubes and were exposed to sodium
hydroxide for 48 hours. Figure 11.6
indicates the great difference in the
behavior of nickel inNaOH when hydrogen
instead of helium is used in tests of