ORNL-2106 - the Molten Salt Energy Technologies Web Site

TABLE 1.1.1. NaK PUMP SPEEDS AND
HORSEPOWER REQUIREMENTS
Main System Auxiliary System
Pump Power Pump Power
Speed Required Speed Required
(rpm) (hp) (rpm) (hd
1900
2300
2650
2800
3000
3200
3400
3500
27
42
61
72
87
102
118
127
1900
2300
2800
2950
3100
3250
3400
3550
7
14
26
31
37
41
46
55
rod in its fully withdrawn position. This places
the level of the sodium-free surface in the well
just a few inches above the top of the reactor
north head. The well extends up about 5 ft above
this level so as to place the control-rod drive
mechanism outside the reactor shield. The sodium
at and near the free surface must be cooled to
below 500OF to minimize the vapor pressure and
hence the diffusion and deposition of sodium vapor
on the components of the control-rod drive mecha-
nism, where such deposits might create operating
difficulties such as shorting of electrical circuits.
Tests have shown that sodium vapor evolution and
deposition are negligible at SOOF.
The lower portions of the sodium in the well
will be exposed to temperatures of about 12OO0F,
and therefore the cooling system includes con-
vection baffles to still the upper few inches of
the sodium and a water jacket around this baffled
sodium zone. As a precaution to ensure against
any possibility of water entering the sodium
chamber, the jacket will be a completely water-
tight assembly, An lnconel sleeve will be shrunk
over the outside of the control-rod well pipe to
form a double wall. Water will be circulated at
220 to 24OOF (sodium melts at 208OF) through the
nd will serve to remove heat or supply
PERIOD ENDlNG JUNE IO, 1956
heat as required by the condition of the reactor
system. No flow or pressure controls will be
provided other than an orifice in the water line,
designed to give a flow of 1 gpm.
The water-jacketed and baffled sodium zone will
be separated from the hot sodium in the lower well
by a solid lnconel plug inserted in the sodium as
a heat dam to keep the thermal gradient along the
lnconel well to a reasonable value from the thermal
stress standpoint. This lnconel plug is a din.-
high cylinder with a central hole drilled along
the cylindrical axis, through which the %-in.-dia
control-rod drive is free to move and position the
rod as required.
The effluent hot water from the jacket will pass
through an economizer, in which it will heat the
entering water stream. This will reduce the water
heating load and cool the effluent stream to prevent
flashing in the drain.
SODIUM SYSTEM STUDIES
R. 1. Gray
Recent tests showed that the flow resistance
in the annuli around the core in which sodium will
be circulated will be somewhat smaller than expected
with the spacers in place. This will effect
a slightly lower over-all pressure drop and more
nearly balanced flow between the cooling holes
and the core annuli. Pressure drop calculations
indicated the need for increasing the thickness
of the control-rod cooling annulus, in which sodium
will circulate, from 0.080 in. to about 0.125 in.
Stress calculations indicate the need for cooling
the top of the sodium expansion tank and for the
addition of a flexible bellows to the island sodium
inlet line (see previous section of this chapter on
"Applied Mechanics and Stress Analysis"). An
auxiliary sodium expansion tank of approximately
0.6 fta has been added to the system so that in
the event of a major reactor shutdown sodium can
be added as the sodium temperature is lowered
from 1200OF to 3Oo0F to avoid a loss of prime
in the sodium pumps (which would otherwise occur
at about 800OF).
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