ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
Three of the capsules were exposed to 1.1 x 1017
t,,,. Gray-green solid residues which filled as
much as 90% of the volume were found in all the
capsules. The residues in the capsules exposed
o a flux of 1.1 x 1017 analyzed 92% uranium, and
he residues in those exposed to a flux of 2.0 x
10'' analyzed 24% uranium. In the capsules given
e higher exposure, gas pressures of between 55
and 100 psi developed. Analyses of these gases
showed about 30% CF, and about 25% C,F,; the
remaining gas was unidentified,
MINIATURE IN-PILE LOOP
Bench Test
W. R. Willis
M. F. Osborne
H. E. Robertson G. W. Keilholtz
Solid State Division
irst successful bench test of the miniature
in-pile loop designed for insertion in a vertical
hole in the LITR included four freezing and melting
cycles in 260 hr of operation. The loop was oper-
ated at 1466OF. The linear velocity of the fused
salt circulated in the loop was between 3.3 fps
(as calculated from the flowmeter) and 3.8 fps (as
calculated from the pump speed); thus a Reynolds
number of about 3000 was obtained. Since it was
possible to freeze and melt the fused salt without
causing failure of the loop, it may be advisable to
fill the in-pile loop before it is inserted in the
reactor and then melt the fuel mixture after the
loop is in position. Since, during the bench test,
the flowmeter was found to be temperature sensitive,
the dependence of the measurement on the temper-
ature must be established.
The bench test was terminated because of a leak
in a collar that was welded over a joint in the fuel
tube. The two ends of the loop did not butt together
at this location, and the annular space thus formed
between the collar and the tube sections trapped
the fused salt in such a manner that expansion of
the salt caused the collar (not the weld) to rupture.
The metal collar stretched from 0.4 in. in diameter
to 0.5 in, before it ruptured, The salt from the
leak, which existed during operation for about 4
hr, showed a tendency to oxidize and to stick to
the lnconel surface rather than to flow rapidly down
the outside tube wall. Thus, a leak in the colder
portion of a loop that was operating in-pile would
probably not flow downward into the high-flux
region before a safety alarm from the released
radioactivity could scram the reactor.
A Delco motor from the group being used in bench
tests has been rebuilt to withstand radiation and
a higher temperature. The wire on both the rotor
and the stator was replaced with glass-insulated
wire, 411 paper was removed, and mica was used
in the commutator and in the rotor segments; glass
cloth yas used, where possible, for other insula-
tion. These changes required that the shaft as-
sembly be slightly modified to allow more space
for windings. The rebuilt motor was tested during
the bench test of the miniature loop, and it was found
to be satisfactory, In a comparison of the operation
of the rebuilt motor with that of the original motor
under no load and under load conditions, the rebuilt
motor was found to be slightly more efficient than
the original motor. Furthermore, since the rebuilt
motor can withstand a higher ambient temperature
and since for a given voltage it produces a higher
speed, higher fuel velocities can be obtained than
were possible previously.
Heat Transfer Calculations
M. T. Robinson
Solid State Division
E. R. Mann F. P. Green
R. S. Stone
Instrumentation and Controls Division
D. F. Weekes, Consultant
An extensive series of heat transfer calculations
has been carried out on the ORNL Reactor Controls
Computer in order to predict the thermal behavior
of a miniature in-pile circulating-fuel loop. The
derivations of appropriate differential equations
and the details of their solution are given in a
forthcoming report,2 The model finally adopted for
the calculations and for the in-pile loop is shown in
Fig. 9.2. It was assumed to be mounted in position
C-48 of the LITR, with the lower end at the location
of maximum thermal-neutron flux.3 The maximum
power density in the fuel in position C-48 was
assumed to be 540 w/cm3.
The computer results were obtained for a variety
of different flow rates of fuel (NaF-ZrF,-UF,,
53.5-40-6.5 mole %) and of cooling air expressed
as Reynolds number of the cooling air stream, Re,
or fuel stream, Re The heat transfer, y, that is,
f'
*M. T. Robinson and D. F. Weekes, Design Calculation
for Miniature Hi h Temperature In-Pile Circulating
Fuel Loop, ORNL-1888 (' in press).
3M. T. Robinson, Solid State Semiann. Prog. Rep.
Feb. 28, 1954, ORNL-1677, p 27.