Chapter
3 Systems of PWR Nuclear Power Plants
The capacity of the waste gas compressor is based on such parameters
as the maximum displaced volume of cover gas from recycle holdup
tanks during the maximum letdown flow operation. The hydrogen
re-combiner gas compressor is sized to provide sufficient flow for
the control of hydrogen concentration at the hydrogen re-combiner
inlet. A typical gaseous waste disposal system has one or two waste
gas compressors, and one or two hydrogen recombiner gas
compressors; each is sized to process 68Nm3/h
of waste gas flow.
Hydrogen re-combiner and hydrogen separator
The
hydrogen re-combiner receives hydrogen waste gas sent by
the hydrogen re-combiner gas compressor, and converts hydrogen in
the waste gas into water vapor through its catalytic reaction with
oxygen. The hydrogen re-combiner is sized to process hydrogen waste
flows up to 85Nm3/ h, based on the capacity of the
hydrogen recombiner gas compressor (68Nm3/h).
The hydrogen separator
receives hydrogen waste gas sent by the hydrogen waste
gas compressor, and separates hydrogen from the waste gas by using
palladium alloy membrane cells; these membranes have excellent
hydrogen permeability. Separated hydrogen gas is reused for purging
the volume control tank cover gas, and the remaining radioactive
waste gases are stored in the hydrogen waste gas decay tank. The
hydrogen separator is sized to process hydrogen waste flow up to
4Nm3/h, based on
the actual process flow rate of 1.2Nm3/h.
(1) System composition and
function
The liquid waste disposal system collects liquid wastes from various
sources, and treats them separately according to their properties.
This system employs various devices such as filters, evaporators and
demineralizers to treat liquid wastes. Distillated water from
evaporators is either reused, or discharged to the sea, after being
monitored to confirm that the concentrations of radioactive
materials are sufficiently low. Based on the different properties of
the liquid wastes, the system is divided into three sub-systems,
i.e., a boron recycle system, a liquid waste processing system, and
a laundry and hot shower waste processing system. The components of
the liquid waste disposal system are shown in Figure 3.9.3.
The boron recycle system, the liquid waste processing system, and
the laundry and hot shower waste processing system are described in
the following subsections.
Boron recycle system
The boron recycle system collects part of the letdown flow from the
reactor coolant system and the water drain from drain lines in the
containment vessel, and stores them in the recycle holdup tank.
After these water quantities are de-gasified and evaporated by the
boric acid evaporators, both the concentrated boric acid solution
and the condensate are sent to appropriate tanks to be reused.
liquid waste processing system
Reactor
coolant
letdown
Reactor
coolant drain in containment
Reactor
coolant drain in aux. bldg.
Equipment
drain in containment
Floor
drain in containment
Reused
as primary makeup
water
Reused
as boric acid water
Equipment
drain in aux. bldg, —
Floor
drain in aux. bldg. __
Chemical
drain —
Laundry drain
—.
Toilet
drain —r
Shower
drain
—1
Acid
drain —
[Laundry
drain tank
SoEd
waste disposal system
Figure
3.9.3 Liquid waste disposal system
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Japan
Liquid Waste Disposal System
Hie liquid waste processing
system processes equipment drains, floor drains and chemical drains
using either a batch processing method or a separate processing
method. The liquid waste processing system shown in Figure 3.9.3,
is based on the batch processing method.
Using the batch processing method
which does not separate different kinds of drains, all liquid wastes
are collected together and stored in the liquid waste holdup tank.
The mixed drains are processed by a waste evaporator. The
evaporator condensate is discharged to the environment, and the
concentrated wastes left at the bottom of the waste evaporator are
pumped to a drumming facility. Using the separate processing method,
liquid wastes from different sources are divided into two
categories, clean and dirty. The clean wastes are almost as clean as
the reactor coolant, while the dirty wastes (which include floor
drains) are contaminated. Clean wastes and dirty wastes are
collected and stored separately in waste holdup tanks, and processed
by different waste evaporators. Condensate of the clean waste
evaporator is usually reused in the reactor coolant system, while
low quality condensate of the dirty waste evaporator is discharged
to the environment
Laundry and hot shower waste processing system
Hie laundry and hot shower
waste processing system collects and stores laundry wastes, toilet
wastes, and hot shower wastes into a laundry and hot shower tank,
and sends these wastes for their processing by either an evaporator
unit or a reverse osmosis unit. In addition to the three waste
processing systems described above, an acid treatment system is used
to treat strong acidic wastes generated in the chemical laboratory
of the power plant
(2) Components
Recycle holdup tank, liquid
waste holdup tank, and laundry and hot shower tank
The recycle
holdup tank receives
reactor coolant through a letdown bypass line and equipment drains
generated in the containment building and the reactor auxiliary
building. The design capacity of the tank is based on an
estimated volume of letdown water during plant startup and shutdown
operations. Tank water is processed by the boron recycle unit, and
the processed liquids are reused for the reactor coolant
system.
Hie liquid
waste holdup tank receives liquid wastes from equipment
drains, floor drains and chemical drains. The tank water is
processed by the waste evaporator.
The laundry
and hot shower tank receives
laundry wastes, toilet wastes and the hot shower wastes, and the
wastes are processed by either the evaporator or the reverse osmosis
unit
Boron recycle evaporator, waste evaporator package, and laundry and
hot shower processing unit
The boron recycle
evaporator evaporates and concentrates the liquid wastes
collected and stored in the recycle holdup tank, including the
reactor coolant flow-down through the letdown line. Both the
condensate and the concentrated boric acid solution generated in the
evaporator are pumped to different tanks in the CVCS, and then used
in the reactor coolant system again. The numbers and the total
capacities of the boron recycle evaporators are determined based on
a requirement that the unit, or units, should have sufficient
capacity to treat the estimated volume of liquid wastes generated
during the plant operations including the excess letdown of the
reactor coolant. Usually, one boron recycle evaporator with a
capacity of approximately 3.4m7 h
or 6.8m2 3/h satisfies this requirement
The liquid waste evaporator
package evaporates and concentrates liquid wastes
collected and stored in the liquid waste holdup tank. The waste
evaporator condensate is released to the environment after being
treated by a demineralizer, and the concentrated wastes accumulated
in the evaporator is pumped to a drumming facility and solidified
and packaged in drums. The numbers and total capacity of the liquid
waste evaporator packages are determined based on the requirement
that the total capacity of the unit, or units, should be at least
two times greater than estimated system loads, even under the
conditions of generating the maximum volume of wastes. Usually one
or
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