ORNL-4191 - the Molten Salt Energy Technologies Web Site

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ORNL-DWG 67-31830
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INlTlAl SAMPI F WEIGHT io8789 g I
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SQUARE ROOT OF REACTION TIME (hr?
Fig. 13.8. Reaction of BF3 with Chromium Metol at
650°C.
CrF, * CrF,, were identified by petrographic tech-
niques. The material is currently being chemically
analyzed for boron.
Although these results are inconclusive with
respect to identification of the oxidation species
in the gas phase, they do illustrate that the direct
use of chemically pure, commercially available
HF3 in high-temperature systems will promote the
oxidation of nearly pure chromium. Further studies
will evaluate the effects of 3F3 concentrations on
oxidation rates and will investigate methods for
improving the purity of BF3.
13.5 COMPATlBlLlTY OF BF,
WITH GULFSPIN-35 PUMP OIL AT 150°F
F. A. Doss P. G. Smith
J. €1. Shaffer
The proposed use of a fluoroborate mixture as the
secondary coolant in the MSRE will require that a
covering atmosphere containing BF be maintained
above the salt in the pump bowl. Since 3F3 is
8
164
known to catalyze the polymerization of certain
organic materials, its effect on the lubricating
properties of the pump oil needs evaluation.
Although these effects will be observed directly
during the planned operation of the PKP-1 loop
with a fluoroborate salt mixture, a pieliminary experiment
is in progress to determine relative
polymerization rates of Gulfspin-35 oil under conditions
which can be related to actual pump operations.
The degree of polymerization should be
indicated by measured changes in oil viscosity
during the experiment.
MSRE-type pumps use a helium purge down the
pump shaft to isolate the luhricated parts of the
pump assembly from the gas environment of the
pump bowl. Previous tests on the prototype pump
loop, using 85Kr as an indicator, showed that this
isolation technique reduced the concentration of
pump bowl gases at the oil-gas interface to about
1 part in 20,000.* Accordingly, this current study
provides accelerated test conditions by contacting
the pump oil with helium containing about 1000
ppm of BF3 at a maximum operating temperature of
150OF.
Two experimental assemblies have been operated
concurrently to provide comparative data. In each
assembly, helium was bubbled at a rate of about
1 liter/min through 1.5 liters of pimp oil. The BF,
was introduced into the helium influent stream to
one experiment at a rate of about 1 cc/min. Samples
of the oil were drained from each experiment
periodically and submitted to the Analytical Cheniistry
Division for viscosity measurements. As
described in a later section, a continuous gas
analysis system was installed and calibrated by
A. S. Meyer, Jr., and C. M. Boyd of the Analytical
Chemistry Division. Concentrations of BF, in the
gas influent and effluent of the experiment are
recorded from the output signal of a thermal conductivity
cell. The light hydrocarbon content
(pioducts of oil polymerization) of the gas effluent
can also he monitored on a semicontinuous basis.
The results obtained through approximately 600
hr of continuous operation of the experiments are
illustrated in Fig. 13.9. Although some discoloration
of the oil exposed to BF, was noted, there is
no distinguishable difference in oil viscosity
between comparative samples. The increase in oil
viscosity (original value, 15.7 centistokes) during
'A. G. Grindell and P. G. Smlth, MSR Program Semi-
ann. Propr. Rept. July 31, 1964, ORNL-3708, p. 155.