the Molten Salt Energy Technologies Web Site

ANP PROJECT QUARTERLY PROGRESS REPORT
During this test there was no
indication of shaft seizing by the
seal. Spectrographic analysis of the
leakage showed the constituents to be
Co, U, Cd, Cr, Fe, K, Ni, and Si, as
w e l l as Na, U, and Zr. Chemical
analysis of the leakage indicated that
the Na, U, and Zr constituents were
present in very nearly the same
proportions as in the fluoride in the
system. A second test, with a similar
packing, in which the compression
member is spring loaded to keep tension
on the graphite at all times has been
in operation for approximately 350 hr
with only small leakage of solid
fluoride and with no operationa.1
difficulties.
Frozen-Lead Seal. A test, similar
to previous tests with sodium, was
conducted to determine the operating
characteristics of a frozen seal when
lead is used as the system fluid,
The equipment consisted of a chromeplated
stainless steel shaft rotating
in a finned sleeve in which the frozen
seal was formed. A pot to contain
the hot lead to supply t.he seal was
attached to the finned section. 'The
finned sleeve was provided with a
heater for melting out the frozen
seal in order to resume operation
after a shut-down. A portion of the
finned section was shrouded so that a
b1.ast of air could he directed across
the seal when required, This test
operated for a period of 526 hr with
leakage occurring when the finned
section temperature was permitted to
exceed 600°F. The lead temperature
in the pot was between 1000 and 1200"F,
and the system pressure was 8 psi.
Very smooth operation was experienced,
with no tendency toward shaft seizure.
The test was terminated when the seal
became too hot and caused an excessive
loss of lead. This test indicates
that a lead pump with a frozen-lead
seal. can be expected to give as satisfactory
performance as a sodium pump
with a f ro Zen -sodium seal
Frozen- Sod i u na Sea 1. Prelim in a ry
26
tests have been conducted to determine
the feasibility of using a frozen-
sodium seal for sealing a high-temper-
ature NaK pump. This design consists
of a heated annulus around the shaft
to which molten sodium is supplied
from an attached container. Sodium in
the annulus is kept molten at all
times. A coolant passage is located
on either side of the molten sodium
for freezing the sodium around the
shaft and preventing sodium leakage
from the annulus. The temperature of
the NaKFs reduced to below the melting
point of the sodium at the frozen
sodium-to-NaK interface. In the
initial tests, some difficulty has
been encountered with heat conduccian
by the solid shaft to the region of
the frozen-sodium seal that is suf-
ficient to melt out the sodium forming
the seal when the NaK bath is at
temperatures greater than 500°F;
however, it is expected that internal
cooling of the shaft w i l l eliminate
thi R di f ficult y.
These tests indicate that such an
arrangement w i l l satisfactorily seal
the rotating shaft of a NaK pump if
the temperature of the NaK at the
NaK-to-sodium interface is below the
melting point of the sodium and
sufficient internal cooling of the
shaft is provided to prevent the
melting of the frozen-sodium seal.
This design is being incorporated
into the pumps for the moderator-
cooling circuit of the ARE and also
in the pumps for the initial circu-
lation of NaK through the ARE fuel
circuit.
Bellows-Type of Valve Stem Seal
(G. M. Adamson, R. S. drouse, Metallurgy
Division). Two, 3-ply, Inconel
bellows 2 in. in diameter and 3 in.
long were examined for the Experimental
Engineering group. The bellows had
been fabricated at the Fulton Sylphon
Co. by using a special rolling technique.
The first one had been immersed in t;he
fuel mixture NaF-ZrF,-UF, (46-50-4
mole %) for 975 hr and the second one