ORNL-1771 - Oak Ridge National Laboratory

ANP QUARTERLY PROGRESS REPOR7
Effect of Zirconium Hydride Additions to Fuel
Various amounts of zirconium hydride were added
to NaF-ZrF,-UF, (50-46-4 mole %) as a means of
reducing the UF, to UF,. The hydride was added
to small portions of fluorides taken from the same
original batch, and filters were used when the
smal I batches were transferred to lnconel thermal-
convection loops. The data from loops operated
with these batches of fluoride mixture are given in
Table 4.8. Layers were found in the cold legs of
all loops to which the ZrH, additions had been
made. The data show that to obtain sufficient
reducing power by the addition of ZrH, to eliminate
corrosion it may be impossible to prevent the loss
of some uranium both in the treatment pot and in
the loop.
Effect of Uranium Concentration
Two loops were operated with a high-purity NaF-
ZrF,-UF, (53.5-40-63 mole %) mixture, This mix-
ture is comparable to the one to be used in the
ARE and has a higher uranium content than the
mixture normally used in thermal-convection loop
tests. The heavy hot-leg attack in both loops was
of the usual subsurface-void type with a maximum
penetration of 10 mils. This is slightly deeper
than the 6 to 8 mils found with the lower uranium
content mixtures. Thin metal lic-appearing loyers
were found in the cold legs of both loops. The
results obtained with these loops confirm those
found previously with similar, but impure, mixtures.
Effect of lnconel Grain Size
lnconel pipe was annealed at two temperatures to
provide specimens with different grain sizes. A
98
Loop
NO.
469
ZrH2
Added
( w
series of loops fabricated from the annealed pipe
was filled from the same batch of NaF-ZrF,-UF,
(50-46-4 mole %) and operated for 500 hr at 1500°F.
Two loops were made from pipe annealed at 2100°F
that had a grain size of 1 to 1\ gr/in., at 100 X,
while the loop fabricated from as-received lnconel
pipe and the one fabricated from pipe annealed at
1600°F contained about 6 gr/in.2. Very little dif-
ference in hot-leg attack was found in these loops.
Those with the larger grains may have had slightly
deeper attack, but the attack was heavier and more
general and the deep penetrations were concentrated
into fewer boundaries.
FLUORlDE CORROSION OF HASTELLOY 6
IN THERMAL-CONVECTION LOOPS
G. M. Adamson
Meta I I urgy Div is ion
Loops fabricated from both as-received and over-
aged Hastelloy B were operated satisfactorily.
The operating mortality rate has been reduced from
90% to 0% in the last group of four loops. The
increase in hardness during operation is not so
great in the loops constructed with over-aged
material as in the loops constructed with as-
received material, but, with proper care, the loops
of as-received material can be operated.
Very little attack was found in a loop which
circulated NaF-ZrF,-UF, (50-46-4 mole %) for
1000 hr at 1500°F. The attack appeared as a few
voids to a maximum depth of 1 mil, with possibly
some increase in surface roughness. Most of the
surface roughness was present in the as-received
tubing, as shown in Fig. 6.17.
TABLE 6.8. EFFECT OF ZrH, ADDITIONS TO NaF-ZrF4-UF4 (50-46-4 male %)
CIRCULATED IN INCONEL THERMAL-CONVECTION LOOPS AT 1H)O"F FOR SO0 hr
Hot-Leg Attack
.~~ .~ ~ _ _
............... ~.~ ..........
Heavy general attack and intergranular voids to a depth of 8 mils
Uranium Content (X)
Before Test After Test
459 0.2 Moderate to heavy attock to a depth of 6 niils 8.6 a. 5
470 0.5 Light to moderate attack to a depth of 3 mils 7.5 7.1
440 0.9 Thin hot-leg deposit; no attack 5.4 5.1
471 2.0 Hot-leg layer to 1 mil thick; no attack 4.0 4.0
___
8.5
a. 8