TM-5-855-4
(9) The total utilization time is then t = 251 + 38 = 289 h if initially at 50 "F and 289 + 101 = 390 h if
initially at 32 "F. This shows that the operating time of a 40/60 iced reservoir is increased by 342 h and
increased by 241 h or 62 percent when compared to a water reservoir initially at a temperature of 32 "F that
has no ice.
5-6. Cooling towers.
a. General
(1) The cooling tower circulating water systems for hardened facilities will generally be of a
closed-loop design utilizing cooling towers, storage tanks, basins, pumps, filters, heat exchangers? and
The tower construction, heat sink storage tank size, and system
water treatment facilities.
configuration will be determined by the facility tactical operating scenario.
(2) Figure 5-1 depicts a hardened facility cooling water system with both hardened and
unhardened towers. Air for cooling towers located within areas protected by blast doors and blast valves
will be separate from air used in primary protected areas. The towers will be separate from air used in
primary protected areas. The towers will be surface mounted or protected below grade to escape the blast
wave. The towers will have sufficient elevations above the settling basin to permit gravity flow of cooling
water from the tower to the hardened basin.
(3) During normal operations, circulating water will be delivered from the cooling towers to the
settling basin and pumped through the various heat exchangers in the facility.
(4) During the attack period, cooling tower fans will be shut down. Valving will be arranged to
provide cooling water on a recirculation basis from the hardened heat sink storage tank with return back
to the heat sink storage tank. This will provide cooling water that is independent of the cooling towers to
meet attack mode heat rejection requirements.
(5) Prior to cooling tower startup following the attack period, towers and drain piping will be
flushed with water from the heat sink storage tank to remove major quantities of dust and dirt to prevent
plugging the system. All flushing water will flow into the dust disposal basin where it will be pumped by
sand pumps to a disposal area outside the power plant. The water discharged from the disposal basin will
be monitored by density meters. When the density reaches a predetermined level, the cooling towers will
be returned to service.
(6) The cooling tower circulating water discharge will then be diverted through 2 micron
polishing filters to remove excess dust and prevent fouling the heat exchangers. The dust removed by the
filters will be backwashes to the disposal basin and will be discharged by sand pumps to the disposal
.
area.
5-12
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