ORNL-4191 - the Molten Salt Energy Technologies Web Site

trap with self-resistance heating for fast heatup,
and a thermal conductivity cell with nickel filamerits.
Initial tests have revealed that the thermal
conductivity cell presently being used is too
sensitive to perturbat.ions in the carrier flow and
that the last traces of HF are desorbed too slowly
fiom corrimercial pelletized NaF. The use of
thermal conductivity cells of different geometry
and bet.ter flow-control. valves is expected to
eliminate the first of these problems. The second
problem will require further development studies to
delermine whether the slow desorption rate represents
an inherent property of the NaF or is a result
of impurities in the NaF. Other trapping materials
will also be investigated.
A special Monel valve has been made and will
be used in the remote HF measuring system. The
valve incorporates two valving systems in the same
metal body and will provide for the simultaneous
adsorption and desorption of HF from alternate
traps. Figure 14.1 shows a schematic of the flow
pattern. This arrangement will eliminate any dead
legs in the HF trapping system and will permit the
measurement of incremental quanfities of HF
evolved from one hydrogenation step in the W3'
transpiration experiment.
One addit.ional step is being taken with regard
to the computer program which is being used for
data a.nalysis. Due to equilibrium shifts of
oxidized and reduced species in the inolten fuel
salt. with temperature changes, the +
starting U3
concentration in the analysis sample at the temperature
of the initial hydrogenation steps will
necessarily be different frotn the U3+ concentra-
I
ORNL-DWG 67-YOO9
I VENT I HF
TRPP 1
THERMAL
CON DUCTlVlTY
CELL TRAP 2 ' H2 PURGE
U
Fig. 14.1. Schematic Flow Diagram of HF Trapping
System.
169
tion in the fuel in the reactor. The computer
program is presently being modified to take this
into account.
14.3 IN-LINE TEST FACILITY
J. M. Dale R. F. Apple
A. S. Meyer
Design work has beeii continuing with the as-
sistance of J. H. Evans 011 the experimental
molten-salt test loop whic-h will be used to eval-
uate electrometric, spectrophotometric, and
transpiration methods for the analysis of flowing
molten-salt streams. 'The operat ion of flow
equipment such as capillaries, orifices, and
freeze valves will duo br tested. A schematic
flow diagram of the proposed test loop is shown
in Fig. 14.2. T'ne first draft engineering drawings
have been completed, and it is planned to stdirt
construction of tile various components of the
system.
14.4 ELECTWQREDUCTlQN OF U
IN MOLTEN liF-SeF2-ZrFF4 AT FAST SCAN
RATES AND SHORT TRANSITION TIMES
D. I,. Manning GIeb ~amantov~
Controlled-poteiitial voltammetric and chrono-
potentiometric studies were carried out on the
reduction of U(IV) in molten LiF-I3eF ,-ZrF,
(65.5-29.4-5.0 mole %). The controlled-potential,
controlled-current cyclic voltammeter was con-
structed in the Instrumentation Group of the
Analytical Chemistry Division at OKNL. In the
controlled-potential mode, scan rates from 0.005
to 500 v/sec are available and cell currents to
100 ma can be measured. IE Lie controlled-current
mode, currents ranging from a few niicroamperes to
100 ma can be passed through the cell. The built-
in time base allows transition times from 400 sec
to 4 msec to be measured. The instrument can
also be operated in a potential-step mode for
chronoamperometric experiments. Readout of the
curves is accomplished with a Tektronix type 549
storage oscilloscope.
28'Analytical Methods for the Ln-Lint: Analysis of
Molten Fluoride Salts," Anal. Chrm. Div. Atin. f'ro&r.
fiept. Oct. 31, 19b6, OWL-4039, p. 18.
3~onsu~tant, Department of czhernistry, University of
Tennessee, Knoxvillt-.