Note: Descriptions are shown in the official language in which they were submitted.
CA 02481522 2004-10-06
NUG~EAR P~WER PLANT
TECHNICAL FIEL~ OF INVENTION
The present invention relates to nuclear power plants. !Ulore specifically,
the
present invention relates to pressurized water reactor nuclear power plants
using
a steam cycle.
BACKGROUND OF THE INVENTION AND PRIOR ART
Pressurized water reactor (PWR) nuclear power plants are well known and
employ a steam generation cycle. A PWR nuclear power plant comprises a
PWR, a group of boilers, a steam turbine, a moisture separator, a steam
repeater, and a feedwater heating unit. A reactor coolant is a light water or
heavy water (in latter case a reactor is also known as a pressurized heavy
water
reactor (PHWR), represented by CANDU reactors). A reactor coolant circuit
consists of a reactor, primary side of boilers, and reactor coolant pumps. The
reactor coolant is pumped between fuel elements of the reactor absorbing a
heat
generated by fue! elements, and through the tube side of boilers releasing the
heat. A secondary circuit with light water as a working fluid) includes a
secondary side of boilers, a steam turbine-generator, a moisture separator-
reheater, a condenser, a group of feedwater heaters, a low pressure feedwater
pump, and a high-pressure feedwater pump. Saturated steam produced in the
boilers is delivered to the steam turbine-generator. Exhaust steam after steam
turbine is condensed in the condenser and condensate is returned to the
boilers
through the group of feed water heaters.
Nuclear power plants are described in the following patents granted in Canada:
1
CA 02481522 2004-10-06
1,223,488 Schluderberg
2,190,855 Tsiklauri
The patent No. 1,223,488 discloses a nuclear power plant having a reactor, a
steam generator, and a steam turbine. The steam generator consists of three
stages to improve a thermal efficiency of the steam cycle.
The patent No. 2,190,855 discloses a nuclear power plant having a reactor, a
steam generator, and a steam turbine. External source of steam is used to
improve the steam quality entering the low-pressure (LP) turbine. This
approach
allows to reduce the steam moisture content in LP turbine, reduce turbine
blade
erosion and improve efficiency of the steam cycle.
The prior art does not address an issue of power uprate of existing PWR
nuclear
power plants. Many of PWR nuclear power plants are presently being uprated by
increasing a reactor thermal output above previous licensing limits. Minor
increase can be accommodated by existing balance-of plant equipment. Larger
increases (extended power uprates) usually involve a replacement of boilers,
turbines, feedwater heaters, piping, or any combination thereof. A cost of
extended power uprate can exceed 1000 $IkW. in addition, the prior art does
not
address an issue of aging of steam generators when a reactor themlal power is
limited due to deteriorated condition of boilers thus reducing a turbine-
generator
output. Therefore it would be desirable to develop additional options for less
expensive power uprates andlor for refurbishment of nuclear power plant with
limited generation due to aging boilers.
The closest prior art (not published yet) is an application 2,454,559 NUCLEAR
P~WER PLANT, filed in Canada 2004101116 by the author of present application.
It discloses a nuclear power plant having a primary circuit comprising a PWR
and
a primary side of steam generators; and a secondary circuit comprising a
secondary side of steam generators, a steam turbine-generator unit and a feed
water heating unit. It also includes a lower pressure steam supply system
2
CA 02481522 2004-10-06
connected to consumers ofi lower pressure steam, all ofi them being in flow
communication with secondary circuit by steam and feed water connections.
These connections potentially afitect a reliability of reactor cooling systems
by
introducing additional elements having a higher than zero probability of
failure,
thus effecting a reactor safety. Therefore it would be desirable to develop a
nuclear power plant with reduced amount of direst connections between the
lower pressure steam supply system and the main steam cycle (secondary
circuit).
SUMMARY ~F THE INVENTION
The present application develops previously filed nuclear power plant
(application
(Canada) # 2,4.54,559 NUCLEAR P~llilER PLANT) fiurther lay arranging a tower
pressure steam nuclear steam supply system and its interconnections to the
consumers of lower pressure steam in a form of a third, independent circuit,
thus
minimizing connections to the second circuit (main pressure nuclear steam
supply system) by steam and feed water. The present invention provides a PWR
nuclear power plant having a main pressure nuclear steam supply system
(MPNSSS), a turbine-generator unit, and a lower pressure nuclear steam supply
system (LPNSSS). The MPNSSS comprises a pressurized water reactor, a
primary side of a group of main boilers, a reactor cootant pump, and a
secondary
side ofi one or of the group of main pressure boilers producing a main
pressure
steam and being connected to turbine-generator unit. The turbine-generator
unit
comprises a higher-pressure turbine, lower pressure turbine, and electrical
generator, a moisture separator-reheater, a condenser, and a fieed water
supply
unit. The feed water supply unit comprises lower and higher pressure feed
water
heaters, deaerator, lower pressure feed water pump (condensate pump), and
higher pressure feed water pump. The lower pressure feed water heaters use an
extraction steam of the steam turbine (not shown on the drawings) or lower
pressure steam produced by LPNSSS. aeaerator is a fieed water heater with
direct contact between the heating steam and the fieed water being heated.
3
CA 02481522 2004-10-06
Deaerator heats the feed water and removes non-condensable gases from the
feed water.
The LPNSSS is connected to reactor coolant circuit downstream of primary side
of main boilers. Steam produced by LPNSSS is used by lower pressure steam
consumers of nuclear power plant. These consumers include feed water
heaters, steam reheater of the moisture separator-reheater (MSR), lower
pressure turbine, a steam turbine driven feed water pump, a steam turbine
driven
condenser cooling water pump, a steam turbine driven condensate pump, and a
steam turbine drnren reactor coolant pump, power house heating system,
condenser air extraction system, and many other consumers of steam or heat
well known in power generation field. Using the lower pressure steam generated
by LPNSSS, these consumers increase the amount of main pressure steam
available for further expansion in main steam turbine or substitute the
electrical
power consumed of the pumps usually driven by electric motors. This results in
increase of the turbine-generator output and in increase of net electrical
output of
the nuclear unit (power plant).
The heat used by LPNSSS reduces the temperature of reactor coolant at the
reactor inlet, therefore allowing to increase reactor thermal power with the
same
reactor coolant flaw rate, the same pressure and same temperature at the
reactor coolant outlet. it will greatly simplify the licensing process for
reactor
power uprate and associated modifications. ~ansequently, it does not effect
the
operation of main steam boilers (temperature, pressure and flow rate of
reactor
coolant at the primary side inlet and outlet of main pressure boilers remains
as it
has been before the reactor uprate) and production (temperature, pressure and
flow rate) of main pressure steam remains the same, As a result, increased
reactor thermal output does not require modifications of the components of
secondary circuit, such as turbine, governing valves, feed water heaters, feed
water and condensate pumps, associated piping, or replacement of main
pressure boilers.
4
CA 02481522 2004-10-06
The LPNSSS can be represented by a lower pressure steam boiler, by heat
exchanger combined with steam separator and circulating pump, or by heat
exchanger combined with lower pressure steam boiler and circulating pump.
Reactor power and associated electrical generator output and net electrical
output of the nuclear unit (power plant) can be increased in accordance with
consumption of the steam generated by LPNSSS.
BRIEF DESCRIPTION (~F THE DRAWINGS
FIG. 1 is a schematic representation of nuclear power plant according to one
embodiment of the present invention and corresponding to the claims 1, 2, 3,
16,
and 22.
FiG. 2 is a schematic representation of nuclear power plant according to
another
embodiment of the present invention and corresponding to the claims 1, 2, 3,
16,
and 22.
FIG. 3 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 2, 3, 16,
and
23.
FIG. 4 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 2, 3, 16,
and
23.
FIG. 5 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 2, 3, 16,
and
21.
FIG. 6 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 2, 3, 16,
and
21.
CA 02481522 2004-10-06
FIG. 7 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 4, 8, 12,
17,
and 22.
FIG. 8 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 4, 8, 12,
17,
and 22.
FIG. 9 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 4, 8, 12,
17,
and 23.
FIG. 10 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 4, 8, 12,
17,
and 23.
FIG. 11 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 4, 8, 12,
17,
and 21.
FIG. 12 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 4, 8, 12,
17,
and 21.
FIG. 13 is a schematic representation of nuclear power plant according to the
embodiment of the present invention corresponding to the claims 1, 2, 3, 4, 5,
7,
8, 9, 11, 12, 13, 15, 1 fi, 17, 18, and 21.
FIG. 14 is a schematic representation of nuclear power plant acxording to the
embodiment of the present invention corresponding to the claims 1, 2, 3, ~, 7,
8,
11, 12, 13, 16, 17, 20, and 21.
s
CA 02481522 2004-10-06
Parts that are not essential to the invention and well known in power
generation
industry, such as feed water heater drains, various valves, boiler blowdown
system, control and instrumentation equipment, etc., are not shown.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1 of the drawings, a nuclear power plant comprises a main
pressure nuclear steam supply system (MPNSSS), a steam turbine-generator
unit, a lower pressure nuclear steam supply system (LPNSSS), and a consumer
of lower pressure steam represented by MSR 8 and feed water heater 15. The
MPNSSS comprises a pressurized water reactor 1, a primary side of a group of
four main boilers 2, a reactor coolant pump 3, and a secondary side of the
group
of four main boilers 2 producing a main pressure steam. The turbine-generatar
unit consists of a higher-pressure (HP) steam turbine 4 and a lower pressure
(LP) steam turbine 5 being shaft coupled with an electrical generator 6, a MSR
consisting of a moisture separator 7 and a two-stage steam reheater 8, a
condenser 9, and a feed water supply unit. The feed water supply unit
comprises
three lower pressure feed water heaters 12, a higher pressure feed water
heater
15, a deaerator 13, lower pressure feed water pump (condensate pump) 11, and
a higher pressure feed water pump 14. The lower pressure feed water heaters
12 use an extraction steam of the steam turbine (not shown on the drawing).
The LPNSSS is represented by first heat exchanger 16, steam separator 18 and
drain pump 19. The primary side of first heat exchanger 16 is connected to
reactor coolant downstream of primary side of main boilers 2. Due to lower
temperature of reactor coolant entering the LPNSSS than a temperature of
reactor coolant entering the primary side of main pressure boilers 2, the
pressure
of the steam produced by LPNSSS (in the range of 2.5 to 5.0 MPa, depending on
selected design parameters) is lower than the steam pressure produced by main
boilers (usually in the range of 4.5 to ~.~ MPa). Steam produced by LPNSSS is
used by lower pressure steam consumers of turbine-generator unit. These
consumers include the feed water heater 15, the steam reheater 8 of the
moisture separator and reheater unit (MSR), and LP turbine. lJsing the lower
7
CA 02481522 2004-10-06
pressure steam from LPNSSS, these consumers increase the amount of main
pressure steam available for expansion in the HP and LP steam turbine. The
extraction steam outlet of the steam turbine can also be used as an additional
steam consumer supplying additional steam to the steam turbine by bypassing
higher-pressure steam expansion stages (not shown on the drawing).
Introduction of additional Sower pressure steam flow from LPNSSS to LP turbine
inlet and substitution of the turbine extraction steam used by feed water
heater
15 and steam repeater 8, by the steam produced by LPNSSS, results in
additional amount of steam available for expansion in LP turbine, and
additional
electrical generator output. The heat used by LPNSSS (educes the temperature
of reactor coolant downstream of heat exchanger 16 and, acxordingly, at the
reactor inlet and does not effect the operation of main boilers 2.
The main boilers 2 produce the main pressure steam at saturation temperature
250°C and pressure 4.0 MPs, at the same time cooling the reactor
coolant from
300°C to 270°C. The main pressure steam is directed to the HP
steam turbine 4
and higher temperature steam repeater of the MSR 8. After expansion in HP
steam turbine 4, the moisture (in the range of 10 to 15~/0) from the main
steam
flow is removed in moisture separator 7. The steam is repeated in two-stage
steam repeater 8. The lower pressure steam repeater uses the steam produced
by LPNSSS, the higher-pressure steam repeater uses the main pressure steam
generated by main boilers 2. The drains of moisture separator 7 and steam
repeater 8 are returned to the steam cycle (not shown on drawing). After MSR,
the main steam is mixed with additional flow of lower pressure steam from
LPNSSS, continues its expansion in LP steam turbine and condenses in the
condenser 9. Condenser cooling water pump 10 supplies the ccmdenser 9 with
amount of water (from river, lake, sea, or cooling tower) sufficient to remove
a
latent heat of condensation of the steam discharged from LP turbine. Lower
pressure feed water pump 11 (condensate pump) returns the condensate to the
steam cycle througp the lower pressure feed water heaters 12, deaerator 13,
higher pressure feed water pump 14, and higher-pressure feed water pester 15.
8
CA 02481522 2004-10-06
The feed water heaters 12 and deaerator 13 use the turbine extraction steam to
heat the feed water. The feed water heater 15 uses the lower pressure steam
generated by LPNSSS.
The parameters of the steam cycle, temperatures and pressures of feed water
and reactor coolant are examples and are not intended to represent actual
design values. However, they are close to actual parameters of PHWR
(CANDU) nuclear power plant.
After separator 18, a water from the drain pump 19 outlet is returned to the
first
heat exchanger 16 water inlet. Reactor coolant at 270°C enters the
~PNSSS
through the first heat exchanger 16 reactor coolant inlet. The water, being
heated in the first heat exchanger 16, reaches the temperature close to the
saturation temperature or partly evaporates. The water leaves the first heat
exchanger 16 through the first heat exchanger water outlet at the temperature
in
220°C to 240°C range, from where it is directed to a steam
separator 18 water
inlet. The pressure in the steam separator 18 is equal or below saturation
pressure of the water at that temperature, for example, being in the range of
2.5
to 3.5 MPa. If the water partly evaporates in the first heat exchanger 16, the
steam separates from the water at saturation pressure. tf the water does not
evaporate in the first heat exchanger 1fi, the pressure in the steam separator
18
is being kept below the saturation pressure of the water entering the
separator;
therefore a part of the water evaporates. The steam separated from the water,
leaves the steam separator 18 at saturation temperature through a steam
separator steam outlet being a LPNSSS steam outlet. The water from steam
separator 18 returns by drawn pump 19 to the first heat exchanger 16 water
inlet
after being mixed with the lower pressure steam condensate coming from the
feed water heater 15 through the drain pump 2fi, and from the first stage
reheater
of MSR 8 through the drain pump 25. !f required, a part of the lower pressure
steam produced by LPNSSS is directed to the inlet of LP turbine 5. To
compensate for associated imbalance of water, appropriate amount of
9
CA 02481522 2004-10-06
condensate is returned to the separator 18 from condenser (not shown on the
drawing).
To balance the steam pressures between LPNSSS and lower pressure steam
consumers, well known in power generation industry means can be used, for
example, orifices, pressure control valves, etc. (not shown on the drawing).
If the lower pressure steam generation in the LPNSSS is in the range of
10°~ of
the main pressure steam generation, and assuming the reactor coolant flow rate
through the first heat exchanger 16 represents 25% of total reactor coolant
flow,
the reactor coolant temperature will be in the range of 255 to 260°C at
the first
heat exchanger 16 reactor coolant outlet. The lower pressure steam can be
produced at saturation temperature 240°C and pressure 3.3. MPa. The
lower
pressure steam is used by higher pressure feed water heater 15 (through
pressure control valve) and by first stage of steam reheater 8 of MSR. In
typical
steam cycle for aforementioned steam parameters, a total steam consumption of
higher pressure feed water heater 15 and first stage of steam reheater 8 of
MSR
represents about 7% of main steam flow rate. By substitution of the turbine
extraction steam by lower pressure steam from LPNSSS, the amount of main
pressure steam available for expansion in the main steam turbine would
increase
by about 7%. The turbine-generator output would increase by approximately 6%
with reactor thermal output increase of approximately 7.5%.
The steam inlet of LP steam turbine 5 can be used as an additional lower
pressure steam consumer. This results in additional net electrical generator
output increase of 2% or more, depending on installed capacity of LPNSSS. In
this case, the total turbine-generator output would increase by approximately
8°~
with reactor thermal output increase of approximately 10.5%.
Referring to FIG. ~ of the drawings, other cower pressure steam consumers are
shown. The reactor coolant pump 3, the lower pressure feed water pump
(condensate pump) 11, the higher-pressure feed water pump 14, and the
CA 02481522 2004-10-06
condenser cooling water pump 10 are shown being driven by steam turbine
drives 22, 33, 23, and 24 respectively, using the lower pressure steam from
LPNSSS. These steam turbine drives are of condensing type (as shown on FIG.
7) and provided with individual condensers 27, 34, 29, and 31 respectively,
and
associated condensate return pumps 28, 35, 30, and 32. As an option, steam
turbine drive exhausts can be connected directly to I_P turbine condenser 9
(not
shown on the drawing). Sackpressure type steam turbines can also be used as
steam turbine drives resulting in the reduced required size of steam piping
and
process simplfication by eliminating individual condensers. The reactor
coolant
pump 3, the lower pressure feed water pump (condensate pump) 11, the higher-
pressure feed water pump 14, and the condenser cooling water pump 10 have
electric drives (motors) in many cases and consume significant amount of
electrical energy generated by the turbine-generator thus reducing the overall
efficiency of the power plant. According to present invention, the electrical
consumption by these pump drives is substituted by mechanical energy
generated by steam turbine drives, thus increasing the net electrical output
of
nuclear power plant. Typically, the reactor coolant pump 3 (or group of pumps)
consumes about 4% of turbine-generator output, the higher pressure feed water
pump 14 (or group of pumps) consumes about 1 °/a of turbine-generator
output,
the condensate pump (or group of pumps) consumes about 0.3% of turbine-
generator output, and the condenser cooling water pump (or group of pumps)
consumes about 0.6% of turbine-generator output. As a result, the net nuclear
power plant electrical output can be increased by 5.9% by increasing the
reactor
thermal output by approximately 6.7% without any changes to existing secondary
circuit equipment (turbine-generator, feed water heaters, main boilers, etc.).
Nuclear power plant can utilize any combination of lower pressure steam
consumers shown on FIG.1 and FIG.7 with appropriate electrical generation
increase in the range from 0.3% to 14%, depending on selected combination and
ability of nuclear reactor to increase the thermal power (output).
11
CA 02481522 2004-10-06
Referring to FIG. 2 of the drawings, the nuclear power plant differs from the
one
shown on FIG. 1 by having a second heat exchanger 17 being connected in
parallel with the first heat exchanger 16 by reactor coolant. The first heat
exchanger 18 is used to heat the water before it enters the steam separator 1
~ of
LPNSSS. The second heat exchanger 17 is used to preheat the feed water
before it enters the main boiler 2 thus increasing the efficiency of main
steam
cycle by supplying the main boiler 2 with the feed water of higher temperature
and increasing the main steam pressure and main pressure steam generation
flow rate.
The nuclear power plant of FIG. differs from the one shown on FIG 2 by shown
lower pressure steam consumers. The reactor coolant pump 3, the lower
pressure feed water pump (condensate pump) 11, the higher-pressure feed
water pump 14, and the condenser cooling water pump 10 are shown being
driven by a steam turbine drive using the tower pressure steam from LPNSSS.
Referring to FIG. 3 of the drawings, the nuclear power plant differs from the
one
shown on FiG. 1 by the steam separator of LPNSSS being replaced by lower
pressure steam boiler 20. The water after the first heat exchanger 16 of
LPNSSS moves through the tubes of the lower pressure steam boiler 20, and
generates a lower pressure steam on secondary side of lower pressure steam
boiler 20. The water returns by the drain pump 19 to the first heat exchanger
16
feed water inlet. In this case, the lower pressure steam boiler 20 is not a
nuclear
class boiler.
The nuclear power plant of FIG.9 differs from the one shown on FiG 3 by shown
lower pressure steam consumers. The reactor coolant pump 3, the lower
pressure feed water pump (condensate pump) 11, the higher-pressure feed
water pump 14, and the condenser cooling water pump 10 are shown being
driven by a steam turbine drive using the lower pressure steam from LPNSSS.
12
CA 02481522 2004-10-06
Referring to FIG. 4. of the drawings, the nuclear power plant differs from the
one
shown on FIG. 3 by having a second heat exchanger 17 being connected in
parallel with the first heat exchanger 16 by reactor coolant. The first heat
exchanger 16 is used to heat the water before it enters the lower pressure
steam
boiler 20 of LPNSSS. The second heat exchanger 1 ~ is used to preheat the feed
water before it enters the main boiler 2 thus increasing the efficiency of
main
steam cycle by supplying the main boiler 2 with the f water of higher
temperature and increasing the main steam pressure and main pressure steam
generation flow rate.
The nuclear power plant of FIG.10 differs from the one shown on FIG 4 by shown
lower pressure steam consumers. The reactor coolant pump 3, the lower
pressure feed water pump (condensate pump) 11, the higher-pressure feed
water pump 14, and the condenser cooling water pump 10 are shown being
driven by a steam turbine drive using the lower pressure steam from LPB~SSS.
Referring to FIG. 5 of the drawings, the nuclear power plant differs from the
one
shown on FIG. 3 by LPI~SSS being represented by the lower pressure steam
boiler 20 being connected downstream of main boiler 2 primary outlet and
heated
directly by reactor coolant. In this case, the steam separator and the drain
pump
are not required. In this case, the lower pressure steam boiler 20 is a
nuclear
class boiler.
The nuclear power plant of FIG.11 differs from the one shown on FIG 5 by shown
lower pressure steam consumers. The reactor coolant pump 3, the lower
pressure feed water pump ~condensate pump) 11, the higher-pressure feed
water pump 14, and the cnder~ser cooling water pump 10 are shown being
driven by a steam turbine drive using the lower pressure steam from LP~tSSS.
Referring to FIG. 6 of the drawings, the nuclear power plant differs from the
one
shown on FIG. 5 by the lower pressure steam boiler 20 being connected to
reactor coolant header downstream of main boner primary outlets and heated
13
CA 02481522 2004-10-06
directly by reactor coolant. The lower pressure steam boiler 20 uses a part of
total reactor coolant flow; the other part of the flow goes through the bypass
(orifice 21 ) resulting in smaller required size of the lower pressure steam
boiler
20.
The nuclear power plant of FiG.l2 differs from the one shown on FiG 6 by shown
lower pressure steam consumers. The reactor coolant pump 3, the lower
pressure feed water pump (condensate pump) 11, the higher-pressure feed
water pump 1~., and the condenser cooling water pump 10 are shown being
driven by a steam turbine drive using the lower pressure steam from LPNSSS.
Referring to FfG. 13 of the drawings, the nuclear power plant represents a
further
development of the nuclear power plant shown on FIG. 6 and FiG.l2_ The
LPf~SSS provides the lower pressure steam to the steam turbine drives of
reactor coolant pump 3, Power pressure feed water pump (condensate pump) 11,
higher-pressure feed water pump 14, and condenser cooling water pump 10.
The steam reheater 8 of the moisture separator and reheater unit (IViSR) is
supplied by Power pressure steam directly from lower pressure boiler 20 sfeam
outlet. The steam turbine drives are represented by back-pressure steam
turbines. Exhaust of steam turbine drive 22 of reactor coolant pump is
connected
to the steam inlet of the feed water heater 15. ,~,dditionai connection to
condenser J is normaify not in ration and should be used in case of feed
water heater 15 unavailability, for example, due to condensate level control
problems. during nuclear power plant startup, etc. Exhausts of steam turbine
drives 23, 24., 33 are connected to the steam inlet of deaerator 1 ~ and to
the
steam inlet of LP turbine. This arrangement of lower pressure steam consumers
allows to use the energy of lower pressure steam more efficiently; energy of
steam expansion in the steam turbine drives and latent heat of condensation in
feed water heater 5 arid deaerator ~ .
The nuclear power plant of F1G. 1represents a further development of the
nuclear power plant shown on FiG. 8, FiG.l2, and FiG.l3. The ~.P~SSS
CA 02481522 2004-10-06
provides the lower pressure steam to the steam turbine drives of reactor
coolant
pump 3, tower pressure feed water pump (condensate pump) 11, higher-
pressure feed water pump 14, and condenser cooling water pump 1~. The
steam repeater 8 of the moisture separator and repeater unit ~SR~ is supplied
by lower pressure steam directly from lower pressure boiler 20 steam outlet.
The
steam turbine drives are represented by back-pressure steam turbines. Exhaust
of steam turbine drive 23 of feed water ump 14 pump is connected to the steam
inlet of the feed water heater 1 b. f~dditiona6 connection to condenser g is
normally not in operation and should be used in case of feed water heater 15
unavailability, for example, due to condensate level contra! problems, during
nuclear power plant startup, etc. Exhausts of steam turbine drives 22, 24, ~3
are
connected to the steam inlet of Ll~ turbine. This arrangement of lower
pressure
steam consumers alto to use the energy of lower pressure steam more
efficiently, the energy of steam expansion in the steam tc~rbine drives and LP
turbine and the latent heat of r~densatidn in f water heater 1~. .ddi*ional
cc~rrr~ections from tl~e exl'~austs of steam turbine drives ~, 4; 3~ carp t?e
made to
deaerator 13 and lower pressure f water heaters 'l2 knot shown on the
drawinos~.
(?n the drawings, the same numbers were assigned to similar nieces of
eauips~ent. for example. to each main boiler 2 of the group of 4; and to the
lower
pressure feed water heaters 12. The steam repeater of moisture separator and
repeater unit t~l~R is sho~rr~ having two repeat stases fro numbers to
different
stages are assig~aed ors the drawings). However. the nuclear power plant
implementing the present invention can have only one repeat stage. It will
result
in sli~ahtly Mower thermal efficiency of the steam cycle.
Terrr~ir~ology used in this application has the fallowina r~ear~inc~s. The
driere of a
laur~p is a source of mechanical energy (electrical motor= diesel. steam
enc~inea
pas turbine. steam turbine) used by the pump. The dri a care be directl~r
shaft
coupled with the pump. or through a transmission. gearbox. etc. The steam
turbine drive can be provided with separate condenser. or be connected to the
CA 02481522 2004-10-06
condenser 9 of steam turbine-generator. Another option is a back-pressure
turbine having a back pressure corresponding to the required steam pressure
for
feed water heaters, reheater of MSR 8 or steam pressure at LP turbine inlet.
Steam turbine drives of aforementioned pumps can a selected having different
back pressures to satisfy requirements for different lower pressure steam
consumers.
Flow communication means that the same fluid moves from first piece of
equipment (component, element) to second piece of equipment, or the same fluid
moves from its source to the first piece of equipment (component, element) and
to the second piece of equipment. It does not imply a direct connection by
pipes.
Other pieces of equipment (elements, components) can be installed between
those two pieces of equipment (for example, isolating valves, pressure control
valves, pumps, etc.),
Boiler is a heat exchanger having a primary and a secondary side. A heating
fluid (reactor coolant) moves through the primary side of the boiler (usually
through the tube side) and transfers the heat to the secondary side (usually
the
shell side). The secondary side liquid {feed water) boils producing a steam.
Part
of feed water is being removed from the boiler as a blowdown to reduce a
concentration of impurities in the boiler. Reactor coolant is a light or heavy
water
used to remove the heat from the reactor fuel and transfer it to the boiler.
Nuclear power plant comprises any amount of main boilers (one, two, four,
eight,
etc.). The boiler can have incorporated preheaters to heat the feed water to
the
temperature close to saturation temperature in the boiler by the heat energy
of
reactor coolant leaving the boiling zone of the boiler.
After LP steam turbine, the steam condenses in the condenser transforming into
the water, which is often called a condensate or, downstream of lower pressure
feed water pump (condensate pump), a lower pressure feed water. The same
condensate is traditionally called a feed water (higher pressure feed water)
downstream of higher pressure feed water pump.
16
CA 02481522 2004-10-06
Several preferred embodiments of the present invention have been shown and
described. t~owever~ it is apparent to those siCilted in the apt that many
changes
and modifications may be made without departing from the invention as it is
defined in the appended claims.
17
