ORNL-1771 - Oak Ridge National Laboratory

ased on low-density calibrating liquids, were
shifted by about 30%. This means that some of
the previously reported viscosity measurements are
about 30% high.
Because of significant improvements made in
fluoride preparation and handling, the mixtures
which are now being obtained from the Materials
Chemistry Division are extremely pure, and they
no longer cause the difficulties encountered in the
early stages of the project, such as fouling of
equipment and variations in physical character-
istics. No doubt some of the earlier viscosity
measurements were high because of the impurities
in the materials.
Thermal Conductivity
W. D. Powers
Reactor Experimental Engineering Division
The thermal conductivities of three solid fluoride
mixtures at normal temperatures were determined
by the transient cooling technique:
T hemal Conductivity
[E+u/hr.ft2 (OF/ft)l
NoF- KF-UF4 (46.5-24.0-27.5 0.7
mole X)
K F -L if -N oF-UF, (43.5-44.5- 2.0
10.9-1.1 miole %)
Li F-KF-UF4 (48.0-48.0-4.0 1.4
male %)
The thermal conductivity of solid LiF-KF-UF,
(48.0-48.0-4.0 mole %) was measured by the steady-
state flat-plate technique; a value of 1.5 Btuhr-ft’
(OF/ft) was obtained. The ratios of corresponding
I iquid to solid thermal conductivity measurements
for the fluoride mixtures studied to date are near
unity.
Electrical Conductivity
N. D. Greene
Reactor Experimental Engineering Division
The experimental current-potenti a I conductivity
cell has been successfully tested and stand-
ardized. The electrical conductivity of a KNO,
melt was determined to within a few per cent of
the values reported in the literature.
As predicted, the effects of polarization within
this cell were greatly reduced by the use of the
alternote meth~d.~ This reduction in the effect
PERIOD ENDING SEPTEMBER 70, 1954
of polarization was further substantiated by the
small observable increase of conductivity with
frequency in contrast to the usual large depend-
ence of conductivity upon frequency, as observed
in the low-resistance conductivity cell. The
measurements on KNO, were obtained during a
single run without the necessity of having to
replatinize the electrodes after each determination,
A refinement of this current-potential cell which
will permit measurements of greater accuracy is
now under way.
Preliminary measurements of several fluorides,
the conductivities of which were determined previ-
ously by an alternate method, were found to be in
good agreement within the inherent limitations of
accuracy. A summary of the preliminary nieasure-
nients of the conductivities of KF-LiF-NaF-UF4
(43.5-44.5-10.9-1.1 mole %), NaF-ZrF,-UF, (50.0-
46.0-4,O mole %), and NaF-ZrF4-UF4 (53.5-40.0-
6.5 mole %), as well as the measurements of
several other salts, has been compiled in a sepa-
rate report. 4
Vapor Pressure
R. E. Moore
Materials Chemi stry Divi sion
Vapor pressure measurements on the mixture
NaF-ZrF4 (25-75 mole %), which were begun last
q~arter,~ have now been completed. The method
and apparatus, originally described by Rodebush
and Dixon,‘ were discussed in previous reports.7fB
The data, given in Table 8.1, can be represented
by the equation
9368 t 10.57 ,
loglo P(mm Wg) = -- -
T(O K)
from which the calculated pressures and the heat
of vaporization (43 kcal/moie) were obtained. The
approximate I iquidus temperature, obtained from
3N. D. Greene, ANP guar, Prug. Rep. June 10, 1454,
ORNL-1729, p 100,
‘N. D. Greene, Measur~riicnts vf the Electrzcnl Con-
ducttvzty of Molten Fluorzdrs, ORNL CF-54-8-64 (to be
issued).
5R. E. Moore and C. J. Barton, ANP Quar. Prog. Rep.
June 10, 1954, ORNL-1729, p 101.
6W. H. Rodebush and A. L. Dixon, Phys. Rev. 26, 851
(1925).
’R. E. Moore and C. J. Barton, ANP Quar. Frog. Rep.
Sept. 10, 1951, ORNL-1154, p 136.
‘R. E. Moore, ANP Qunr. Prog. Rep. Dec. 10, 1951,
ORNL-1170, p 126.
129