ORNL-2106 - the Molten Salt Energy Technologies Web Site

ANP PROJECT PROGRESS REPORT
LOUVER CONTROL SIMULATION
i. M. Eastman' F. P. Creen
E. R. Mann
The ART simulator was used for further study
of the problem involved in closing the main heat-
dump louvers to prevent the fuel from freezing as
the result of a fast insertion of the control rod. Im-
proved transport-lag simulators were incorporated in
the system. The control technique to be used will
be that of closing the louvers to limit the minimum
NaK temperature.
Two louver-closing speeds have been found to
be necessary to keep the temperature of the NaK
returning from the radiator from dropping below the
fuel freezing temperature. One speed will auto-
matically close the louvers from the open position
to the 10% open position in 9 sec after a fast
control-rod insertion. With the louvers at the 10%
open position and with the four main blowers at
design point speeds, 15 Mw of power will be
removed.
The slow-speed louver actuators will operate on
a temperature signal from the radiator outlets.
When this temperature drops below 1O7O0F, the
slow actuator will start to close the louvers. The
slow actuator will be capable of closing the 10%
open louvers in 3 sec.
For the simulation study it was assumed that all
four blowers remained in operation, two being
supplied from the TVA circuit and two from the
diesel circuit. With the four blowers operating, a
fast control-rod insertion will automatically shut
off the power to one of the blowers on the TVA
circuit and one on the diesel circuit. A power
failure of either the TVA circuit or the diesel
circuit would then leave only one blower in opera-
tion. The NaK-temperature undershoots would then
be somewhat less, the overshoots somewhat more,
and the ultimate cooling rate lower. Although this
NaK-temperature limit system seems to be func-
tionally acceptable, the system will be further ex-
plored on the simulator. The fail-safe character-
istics are being studied, and modifications may &
made which will require further simulator work for
evaluation.
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'On assignment from Bendix Products Division.
1.3. ART INSTRUMENTS AND CONTROLS L)
E. R. Mann
C. S. Walker 8
LOUVER ACTUATOR
J. M. Eastman
Specifications for the louver actuators were
established that are based on the following safety
considerations: first, if the actuators should fail,
the louvers must lock into the position they are in
at the time of failure; second, the components
which are not considered to be of first-order re-
liability must be located in an area accessible for
repair without the NaK systems having to be cooled
or drained; and, third, the over-all system relia-
bility and dependability must be high. Since the
actuators and any locally mounted associated equip-
ment will not be accessible during the test, these
components must be of first-order reliability.
Hydraul ic-actuator cy1 inders were selected. They
will be operated in conjunction with spring-loaded
clamps arranged to grip the actuator-output shafts.
For steady-state louver conditions, both ends of
the actuator cylinder will be vented to the hydraulic
return, or drain. The louvers will be moved by
valving hydraulic pressure to either end of the
hydraulic cylinder. This pressure will be simul-
taneously vented to a piston which will release the
spring-loaded clamp. The rate of louver movement
will then be controlled by an orifice in the line
through which return hydraulic fluid will flow from
the cylinder to the drain.
The fast louver-closing rate will be obtained by
opening an orifice in parallel with the one used for
slow closing. The hydraulic pressure supply unit
is to be located in an area accessible for repair
work. Two pumps will be used that will operate
in parallel and be driven from different electric
power sources. They will be arranged so that one
can be repaired or replaced without interrupting
the fluid-pressure supply. Solenoid valves will be
used for control of the hydraulic fluid. When not
energized, these valves wi II hold the louvers fixed,
and they will be energized to move the louvers.
Low-viscosity hydraulic fluid and thin-plate
orifices will be usedso that the flow rates and the
corresponding louver-actuation rates wi II be rela-
tively insensitive to fluid temperature. Valves
and orifices will be located near the hydraulic-
power-supply unit in an area accessible for repair
work.
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