PRESSURIZERS
DOE-HDBK-1018/2-93
Miscellaneous Mechanical Components
A dynamic pressurizer must be connected in the system to allow a differential pressure to exist
across it. The bottom connection, also called the surge line, is the lower of the two pressure
lines. The top connection, referred to as the spray line, is the higher pressure line. Differential
pressure is obtained by connecting the pressurizer to the suction and discharge sides of the pump
servicing the particular system. Specifically, the surge (bottom connection) is connected to the
pump's suction side; the spray line (top connection) is connected to the pump's discharge side.
A basic pressurizer is illustrated in Figure 15.
The hemispherical top and bottom
Figure 15 Basic Pressurizer
heads are usually constructed of
carbon steel, with austenitic stainless
steel cladding on all surfaces exposed
to the reactor system water.
The pressurizer can be activated in
two ways.
Partially filling the
pressurizer with system water is the
first.
After the water reaches a
predetermined level, the heaters are
engaged
to
increase
water
temperature. When the water reaches
saturation temperature, it begins to
boil.
Boiling water fills the void
above the water level, creating a
saturated environment of water and
steam. The other method involves
filling the pressurizer completely,
heating the water to the desired
temperature, then partially draining
the water and steam mixture to create
a steam void at the top of the vessel.
Water temperature determines the
amount of pressure developed in the
steam space, and the greater the
amount of time the heaters are
engaged, the hotter the environment
becomes.
The
hotter
the
environment, the greater the amount
of pressure.
Installing a control valve in the spray
line makes it possible to admit cooler water from the top of the pressurizer through the spray
nozzle. Adding cooler water condenses the steam bubble, lowers the existing water temperature,
and reduces the amount of system pressure.
ME-05
Rev. 0
Page 32
