ORNL-2106 - the Molten Salt Energy Technologies Web Site

Liquid (688 to 8986C)
I .
HT - H3Q°C = -8812 + 0.9249T - (24.62 x 10-5)T2
At 652OC
"q - "01
In these expressions
H = enthalpy in cal/g,
= heat capacity in cal/g-'C,
=+ = temperature in OC.
VISCOSITY AND DENSITY
5. 1. Cohen
cP = 0.9249 - (49.23 x lO")T
= 170
A study was made of the effect of fission
products on the viscosity of a fused fluoride
reactor fuel. The increase in viscosity as a
result of the presence of dissolved fission-product
additives was found to be less than 5%. The
formula for the fission-product additives was,
however, based on a much higher burnup rate than
would actually be encountered in the ART. The
formula called for an amount of LaF, (the com-
ponent used to represent all the rare-earth fluorides
formed by fission) that exceeded the solubility
limit in the fuel at temperatures below 800OC. It
is felt that the only serious possible problem that
might arise would be the precipitation of solids.
This problem is being investigated in solubility
studies on fission products in the reactor fuel
(see Chap. 2.3, "Chemical Reactions in Molten
Salts").
Interest in the fuel mixture NaF-KF-LiF-UF,
le prepared for these
centipoises at about
hese valws are in sa
revious data; the new
"S. I. Cohen, ANP Qum. Prog. Rep. Sept. 10, 1955,
ORNL-1947, p 156.
PERlOD ENDlNC JUNE 10, 1956
Measurements were also model5 on NaF-LiF-KF-
UF, (10.9-44.5-43.5-1.1 mole %). The viscosity
varied from 8.8 centipoises at about 500°C to
1.8 centipoises at about 8OO0C and may be
represented th'roughout this range by the equation
p - 0.0348e4265'T ,
where T is in OK.
A modest program has been initiated to measure
the physical properties of some fused chloride
mixtures. Two instruments have been designed
to study the viscosities of these materials. One
is a special Brookfield viscometer, which has a
spindle assembly that contains two large shear
surfaces. This increased shear is necessary
because of the low viscosity range in which this
class of materials falls. The other instrument is an
adaptation of the capillary viscometer currently
being used for fluorides. The principal modifi-
cation is the use of commercial hypodermic needles
for the capillary tubes. This affords a number of
advantages, such as ease of replacement and
interchangeability of needle sizes to cope with
different viscosity ranges.
A density measurement was made on one chloride
mixture, LiCI-KCI-NaCI (56-41-3 mole %), by using
the buoyancy principle with a balance and a
plummet. The density varied from 1.675 g/cm3
at 425OC to 1.50 g/cm3 at 77OOC and may be
expressed as
p = 1.885 - O.OOO5OT 8
where T is in "C. These values are in excellent
agreement with values obtained on very similar
mixtures by Van Artsdalen and Yaffe.I6
"S. 1. Cohen and f. N. Jones, Measurement o/ the
Viscosity of Compositions 12, 14 and 107, ORNL
CF-56-5-33 (May 98 1956).
"E. R. Van Artsdalen and I,
Chem 598 118-27 (1955).
S. Yaffe, 1. Phys.
23 1
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