ORNL-1816 - the Molten Salt Energy Technologies Web Site

PERIOD ENDING DECEMBER 70,1954
TABLE 6.1. RESULTS OF INCONEL THERMAL-CONVECTION LOOP TESTS
OF NaF-KF-LiF (11.5-42-46.5 male %) WITH AND WITHOUT UF4
CIRCULATED AT A HOT-LEG TEMPERATURE OF 15OOOF
Period of
Test
Uranium
Content
Maximum
Attack
Meta I lographic Nates
(hr) (wt %) (mils) Hot-Leg Appearance Cold-Leg Appearance
500 11.9 11 Heavy, intergranular, subsurface voids Metallic deposit
500 12* 13.5 Heavy, general, intergranular, subsurface voids Metallic deposit
1000 12* 20 Heavy, general, intergranular, subsurface voids Metallic deposit
500 0 7 Moderate, general, intergranular, subsurface No deposit
voids
500 0 7.5 Heavy, general, intergranular, subsurface voids Thin deposit in one section
*Estimated; analyses not yet available.
same fluoride mixture without uranium was circu-
lated for 1000 hr without signs of plugging. The
hot leg of this loop showed heavy attack to a depth
of 10 mils, and some grains were completely removed.
Effect of Induced Potential
2
-
P
Welding rods for use as electrodes were attached
to the upper hot legs and lower cold legs of Inconel
thermal-convection loops that were operated to
determine the effect of a small induced emf on
corrosion. Battery chargers were used to apply
direct currents of 5.4 amp at 0.45 v. The loops
circulated NaF-ZrF4-UF, (50-46-4 mole %) at a
hot-leg temperature of 1500OF.
The direction of current flow was exDected to
have an effect on the attack, but no such variation
the small attack that occurs takes place in a fairly
short time and is a function of the conditioii of the
original surface.
The loops operated with sodium were known to be
covered with an oxide deposit and were not cleaned
before filling. Additional loops that were cleaned
with the use of dry hydrogen are now being operated.
Special Alloy Thermal-Convection Loolps
Several loops were fabricated from tubing of
modified Inconel specially drawn at Superior Tube
Co. from billets that were vacuum cast at ORNL.
The loops were standard size, but the tubing was
& in. in diameter with a 0.065 -in, ‘ wall rattier than
the standard 3/,-in.-IPS schedule-10 pipe; they were
filled with NaF-ZrF4-UF, (50-464 mole %) and
operated with a hot-leg temperature of ‘1500°F.
Some of these loops ruptured when attempts were
made to restart them after the two power failures.
The data obtained from these loops are given in
t a considerable
h of attack was found in both
loops in which the chromium content of the alloy
effect on c
that c i rcul at
fluoride mixtures, but there is some evidence that that usually found with Inconel.
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