ORNL-4191 - the Molten Salt Energy Technologies Web Site

in a silica tube. (The standard, KNO,, was contained
in a Pyrex beaker.) The voltage drop across
a resistor in series with the electrodes and electrolyte
was measured with an oscilloscope whose
vertical amplifier was provided with a calibrated
voltage offset. Bridge nieasurements also were
made with the same cell, using a General Radio
model 1650A impedance bridge" In order to improve
the sensitivity and reproducibility of the
measurements, a bridge was constructed with a
100-ohm Helipot to provide the ratio arms and with
a decade resistance box and variable parallel capacitance
in the balancing arm. An oscilloscope
served as the phase balance and null detector.
The preliminary results listed in Table 10.2 are
probably in error by 20 to SPh, the limiting factor
being the small cell constant in the initial experiments.
A new dipping cell has been constructed to provide
a cell constant of the order of 100 by in-
creasing the current path length through the elcc-
trolyte. In the new cell, the electrodes will enter
the melt through silica tubes of about 0.3 cm ID
and extending 3 cm below the surface of the melt.
The dependence of the measured conductivity on
the temperature and composition of the melts and
on frequency is under investigation.
Table 10.2. Electrical Conductivity of Molten
Fluorides and Fluoroborates
Conductivity Temperature Ternprrar''re
Coefficient
(ohm-'crn-'> ("C)
[( "C) - 'I
2LiF-BeF 1.5 650 1
LiF -ThF 2.0 65 0 3 x 10-3
NaRF 0.8 450
2 io-,