ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
26OOC and 8.9 x and 9.6 x lo’* at 450°C.
X-ray diffraction studies of the binary systems of
alkali fluorides with uranium trifluorides are
under way.
6. Corrosion Research
Studies of the corrosion of Inconel, type 316
stainless steel, Hastelloy B, and several special
alloys when exposed to the fluoride mixtures of
interest were continued through the use of thermal-
convection apparatus. In the studies of lnconel
loops containing UF, in alkal i-metal-base mixtures,
considerable difficulty was encountered in making
the mixtures, in controlling the total uranium con-
tent, and in determining the ratio of UF, to UF,.
Conflicting data were obtained, and efforts are
now being made to achieve better control of the
variables involved. An al kal i-metal-base mixture
containing UF, was also circulated in type 316
stainless steel loops, and, as in the lnconel loops,
considerable mass transfer occurred.
Thermal-convection loops constructed of Hastel-
loy B were operated with NaF-ZrF,-UF, (50-46-4
mole %), with NaF-KF-LiF (1 1.5-42.0-46.5 mole %)
containing 12 wt % uranium as UF, and with
sodium as the circulated fluids. The loops which
circulated the fluoride mixtures showed only small
amounts of corrosion - 1.5 to 3 mils. The period
of operation of the loop has not had a noticeable
effect on the corrosion; therefore it is felt that the
small amount of corrosion that occurs takes place
in a short time and may be a function of the condi-
tion of the original surface. The Hastelloy B
loops operated with sodium exhibited considerable
mass transfer. Since the loops were known to be
coveredwith an oxide deposit and were not cleaned
before they were filled, additional loops are to be
operated to determine whether the mass transfer
was caused by contamination. Loops constructed
of several modified Inconel-type alloys were
operated with NaF-ZrF,-UF,. The data obtained
from these loops indicate that reduction of the
chromium content of the alloy to 5% or less greatly
reduces corrosion.
Tests of the compatibility of sodium, bgryllium,
and lnconel in a system have indicated that at
13OOOF the flow rate of the sodiumand the spacing
between the beryllium and the lnconel are the con-
trol I ing factors. Beryl I ium surfaces exposed to
flowing sodium are unattacked, but surfaces ex-
posed to relatively stagnant sodium at 130OOF
show dissimilar metal mass transfer between the
beryllium and the Inconel. Tests are under way to
determine the minimum spacing that can be tolerated
between beryllium and lnconel when exposed to
slow-moving sodium.
Several type 304 stainless steel T-joints brazed
with experimental alloys prepared by the Wall
Colmonoy Corporation were tested in sodium and
in NaF-ZrF,-UF,. Most of the alloys had good
resistance to the fluoride mixture, but only the
10.2% P-13% Cr-76.8% Ni alloy had good resis-
tance in both sodium and the fluoride mixture.
Several T-joints of A-nickel were also brazed
with various alloys and tested in the fluoride
mixture NaF-ZrF,-UF, and in sodium hydroxide.
All the alloys tested had good resistance in the
fluoride mixture, except the 69% Ni-20% Cr-11%
Si alloy, whereas all the alloys had poor resistance
to sodium hydroxide, except the 82% Au-18% Ni
alloy,
The carbides of titanium, zirconium, chromium,
and boron were corrosion tested in fused fluorides,
in sodium, and in lithium. For the most part, these
carbides showed fair resistance in the various
media, except B,C, which was rather severely
attacked in sodium and in lithium. The aqueous
corrosion resistance of an 80% Mg-20% Li alloy
which has been proposed as a crew-compartment
shielding material is being studied. Dynamic
tests of the resistance of lnconel to attack by
rubidium are under way. Preliminary results
showed maximum attack in the hot leg to a depth
of 1 mil.
Previous tests on the mass transfer character-
istics of container materials in liquid lead indi-
cated that alloys in which intermetallic-compound
formation was possible showed a marked increase
in resistance to mass transfer as compared with
the pure components of the materials. Additional
tests of this hypothesis have now been conducted.
The work on fused hydroxides has centered on the
development of a systematic chemistry of these
substances. By an application of an acid-based
theory, at least 12 types of acid-base analog
reactions are predicted for the fused hydroxide
systems. Each of these types is briefly discussed
in the text. Work on the flammability of alkali-
metal solutions at high temperatures has continued,
and additional data have been obtained for bismuth-
rich alloys with sodium which provide a more com-
plete picture of the reactivity of this system. The
effect of water vapor on the reactivity of these
alloys has also been studied.