ORNL-1771 - Oak Ridge National Laboratory

PERIOD ENDING SEPTEMBER 10, 1954
TABLE 6.7. EFFECT OF MIXTURES OF UF3 AND UF4 IN NaF-ZrF4 ON CORROSION OF INCONEL
THERMAL-CONVECTION LOOPS OPERATED AT A HOT-LEG TEMPERATURE OF 1 SOOOF
-____..__
Loop Total U U as UF3 Operating Metallographic Notes
No. (wt X) (wt %)
Time
(hr)
Hot-Leg Appearance Col d-L eg Appearance
-~
473 8.7 1.2 500 Moderate intergranular subsurface Occasional metal crystals
voids to a depth of 4 mils
491* 12.8 2.5 500 Moderate to heavy intergranular
subsurface voids to a depth of
7 mils
492* 14.2 1.8 2000 Moderate to heavy intergranular
subsurface voids to a depth of
15 mils
4 69 8.5 0 500 Heavy general attack and inter-
gganular subsurface voids to a
depth of 8 mils
462 13.9 0 500 Moderate to heavy intergranular
subsurface voids to a depth of
10 mils
~~
Deposit to 0.3 mil thick
Deposit to 1 mil thick
No deposit
Metallic deposit to 0.3 mil thick
.-
"These loops were filled from the same Latch of fluoride mixture, and the differences in uranium analysis cannot yet
be explained.
Two lnconel loops were operated for 500 hr with
NaF-KF-UF, to which UF, and UF, had been
added. Because of sampling and analytical dif-
ficulties, the relative amounts of UF, and UF, are
not known, but it appears that about one-third of
the uranium was present as UF,. One loop con-
tained a total uranium content of 10.4 wt %, and
after the test the hot leg showed light, widely
scattered attack to a depth of 1 mil (Fig. 6.16);
the hot-leg surface was quite rough. The other
loop contained 7.4 wt % uranium, and the hot leg
showed a void type of attack that varied from light
to heavy, with a maximum penetration of 2 mils;
again, the surface was rough. In both loops, a
layer was found in the cold leg but not in the hot
leg. These mixtures appear to be superior to the
ZrF,-base mixtures with UF, with respect to depth
of the subsurface void type of attack, and the hot-
leg deposit found with the UF3-bearing ZrF,-base
mixtures did not form. More work is needed to de-
termine whether the rough surfaces represent a
different type of attack and whether the cold-leg
deposits formed are NaK,CrF,, which would
interfere with heat transfer.
__
Fig. 6.16. Hot-leg Surface of lnconel Loop
After Circulating a Mixture of UF, and UF, (4.3 wt
% UF, and 6.9 wt % UF,) in NaF-KF-LiF (11.5-
42.0-46.5 mole %) for 500 hr at 1500°F. Etched
with modified aqua regia. 250X. Reduced 36%.
97