U.S. patent application number 15/535360 was filed with the patent office on 2017-11-09 for horizontal steam generator for a reactor plant with a water-cooled water-moderated power reactor and a reactor plant with the said steam generator.
The applicant listed for this patent is AKTSYONERNOE OBSHCHESTIVO "ORDENA TRUDOVOGO KRASNOGO ZNAMENI I ORDENA TRUDA CHSSR OPYTNOE. Invention is credited to Dmitriy Aleksandrovich LAKHOV, Aleksey Vladimirovich SAFRONOV.
Application Number | 20170321879 15/535360 |
Document ID | / |
Family ID | 55959896 |
Filed Date | 2017-11-09 |
United States Patent
Application |
20170321879 |
Kind Code |
A1 |
LAKHOV; Dmitriy Aleksandrovich ;
et al. |
November 9, 2017 |
Horizontal Steam Generator for a Reactor Plant with a Water-Cooled
Water-Moderated Power Reactor and a Reactor Plant with the said
Steam Generator
Abstract
This invention relates to electric power industry, and more
particularly to horizontal steam generators for nuclear power
plants with a water-cooled water-moderated power reactor (VVER) and
to reactor plants with a VVER reactor and a horizontal steam
generator. A reactor plant with a VVER reactor and a horizontal
seam generator, including a nuclear reactor with four circulation
loops, each comprising a steam generator with a horizontal bundle
of heat-exchange tubes divided into banks by means of inter-tubular
tunnels and connected to primary circuit coolant headers inside a
cylindrical pressure vessel with elliptical bottoms, a reactor
coolant pump, and a primary circuit coolant main circulation
pipeline.
Inventors: |
LAKHOV; Dmitriy Aleksandrovich;
(Podolsk Moskovskaya, RU) ; SAFRONOV; Aleksey
Vladimirovich; (Podolsk Moskovskaya, RU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AKTSYONERNOE OBSHCHESTIVO "ORDENA TRUDOVOGO KRASNOGO ZNAMENI I
ORDENA TRUDA CHSSR OPYTNOE |
Podolsk |
|
RU |
|
|
Family ID: |
55959896 |
Appl. No.: |
15/535360 |
Filed: |
December 9, 2015 |
PCT Filed: |
December 9, 2015 |
PCT NO: |
PCT/RU2015/000785 |
371 Date: |
June 12, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F22B 1/162 20130101;
F22B 37/228 20130101; F22B 1/023 20130101; F22B 37/002 20130101;
F22B 37/22 20130101; F22B 29/06 20130101 |
International
Class: |
F22B 1/02 20060101
F22B001/02; F22B 37/22 20060101 F22B037/22; F22B 29/06 20060101
F22B029/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2014 |
RU |
2014150427 |
Claims
1. A horizontal steam generator for a reactor plant with a
water-cooled water-moderated power reactor comprising a cylindrical
pressure vessel equipped at least with one feed water supply
connection pipe and one steam removal connection pipe, and two
elliptical bottoms, internals, primary circuit coolant inlet and
outlet headers connected to a heat-exchange tube bundle forming a
steam-generator heat-exchange surface, the heat-exchange tube
bundle being divided into banks by intertubular tunnels, wherein
distance S between the primary circuit coolant header centerlines
in the transverse direction of the steam generator pressure vessel
has been selected based on the following ratio: 0.4 .ltoreq. S D
vess .ltoreq. 0.6 , ##EQU00010## where D.sub.vess is the steam
generator pressure vessel inner diameter, and steam generator
length L.sub.v along the inner surfaces of the elliptical bottoms
has been selected based on the following ratio: L .kappa. = D head
+ 2 [ ( ctg ( .alpha. 2 ) - 1 sin ( .alpha. 2 ) ) ( B 1 2 + B 2 + (
.pi. D head 4 S head - 1 ) S h ) + ( .pi. D head 4 S head - 1 ) S h
1 sin ( .alpha. 2 ) + .DELTA. ] + H hes 10 6 .pi. d N tb ,
##EQU00011## where: D.sub.head is the coolant header outer diameter
in the drilled part, mm, .alpha. is the heat-exchange tube central
bend angle, deg., B.sub.1 is the width of the heat-exchange tube
central intertubular tunnel, mm, B.sub.2 is the width of the
heat-exchange tube intertubular tunnel opposite to the coolant
header, mm, S.sub.head is the heat-exchange tube circumferential
spacing on the outer surface of the coolant header, mm, Sh is the
spacing between heat-exchange tubes in the horizontal heat-exchange
bundle row, mm, H.sub.hes is the steam generator heat-exchange
surface area, m.sup.2, N.sub.tb is the number of steam generator
heat-exchange tubes, pcs., d is the outer heat-exchange tube
diameter, mm, .DELTA. is the distance from the outer heat-exchange
bundle tube to the steam generator bottom inner surface along the
longitudinal steam generator axis, in mm, wherein central
heat-exchange tube bend angle .alpha. and distance .DELTA. have
been selected from the following ranges:
90.degree..ltoreq..alpha..ltoreq.150.degree. and
300.ltoreq..DELTA..ltoreq.1000 mm.
2. A steam generator according to claim 1, wherein the
heat-exchange tube bundle is filled with heat-exchange tubes from
bottom upwards evenly with vertical gaps between adjacent tubes not
exceeding the vertical spacing of tubes in the bundle.
3. A steam generator according to claim 1, wherein the vertical
intertubular tunnel width is between 100 mm and 250 mm.
4. A steam generator according to claim 1, wherein the
heat-exchange tube bend at the point of connection to the coolant
header shall have a radius of at least 60 mm and, preferably, at
least 100 mm.
5. A steam generator according to claim 1, wherein the coolant
header drilling area shall exceed the area of the holes for
connection of heat-exchange tubes to the same by at least 20%.
6. A reactor plant with a water-cooled water-moderated power
reactor and a horizontal seam generator, including a nuclear
reactor with four circulation loops, each comprising a steam
generator with a horizontal bundle of heat-exchange tubes divided
into banks by means of intertubular tunnels and connected to
primary circuit coolant headers inside a cylindrical pressure
vessel with elliptical bottoms, a reactor coolant pump, and a
primary circuit coolant main circulation pipeline, wherein pressure
vessel bore D.sub.vess, distance S between the centerlines of the
primary circuit coolant headers in the transverse direction and
steam generator length L.sub.v along the inner surfaces of the
elliptical bottoms have been respectively selected based on the
following ratios: 0.148 D + 0.637 0.054 D 2 + 3.142 N tb S h S v k
.ltoreq. D vess .ltoreq. 1.827 H , 0.4 .ltoreq. S D vess .ltoreq.
0.6 , L .kappa. = D head + 2 [ ( ctg ( .alpha. 2 ) - 1 sin (
.alpha. 2 ) ) ( B 1 2 + B 2 + ( .pi. D head 4 S head - 1 ) S h ) +
( .pi. D head 4 S head - 1 ) S h 1 sin ( .alpha. 2 ) + .DELTA. ] +
H hes 10 6 .pi. d N tb , ##EQU00012## where: D is the rated steam
generator capacity, t/h, N.sub.tb is the number of steam generator
vessel heat-exchange tubes, pcs., Sv, Sh is the spacing between
heat-exchange tubes in vertical and horizontal rows of
heat-exchange bundle, respectively, mm, k is the arrangement
identifier of heat-exchange tube bundle in a bank (k=1 for in-line
arrangement and k=2 for staggered arrangement), H is the steam
generator vessel tube filling height, mm, D.sub.head is the primary
circuit header outer diameter in the drilled area, mm, .alpha. is
the heat-exchange tube central bend angle, deg., B.sub.1 is the
width of the heat-exchange tube central tunnel, mm, B.sub.2 is the
width of the heat-exchange tube tunnel opposite to the coolant
header, mm, S.sub.head is the heat-exchange tube circumferential
spacing on the outer surface of the coolant header, mm, H.sub.hes
is the steam generator heat-exchange surface area, m.sup.2, d is
the outer heat-exchange tube diameter, mm, .DELTA. is the distance
from the outer heat-exchange bundle tube to the steam generator
bottom inner surface along the longitudinal steam generator axis,
in mm, wherein heat-exchange tube bend angle .alpha. and distance
.DELTA. have been selected from the following ranges:
90.degree..ltoreq..alpha..ltoreq.150.degree. and 300
mm.ltoreq..DELTA..ltoreq.1000 mm.
7. A reactor plant according to claim 6, wherein the steam
generator and the reactor coolant pump are connected to the reactor
building walls by hydraulic snubbers.
8. A reactor plant according to claim 6, wherein the reactor
coolant pump is installed downstream of the steam generator along
the primary circuit coolant flow in the circulation loop.
9. A reactor plant according to claim 6, wherein the reactor
coolant pump is installed both on the hot leg and the cold leg of
the main circulation pipeline in the circulation loop.
10. A reactor plant according to claim 6, wherein two reactor
coolant pumps are installed in parallel on the cold leg of the main
circulation pipeline.
11. A reactor plant according to claim 6, wherein gate valves are
installed on the main circulation pipeline legs.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a US 371 application from
PCT/RU2015/000785 filed Dec. 9, 2015, which claims priority to
Russia Application 2014150427 filed Dec. 12, 2014, the technical
disclosures of which are hereby incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention relates to electric power industry, and more
particularly to horizontal steam generators for nuclear power
plants with a water-cooled water-moderated power reactor (VVER) and
to reactor plants with a VVER reactor and a horizontal steam
generator.
[0003] A steam generator is the most important element of the
reactor plant (RP) primary circuit of VVER nuclear power plants
(NPP). Steam is generated in it due to the heat produced in the
reactor, the steam is used as the turbine working medium for power
generation. In addition to steam generation, steam generators must
ensure reliable and continuous cooling of the reactor core in all
NPP operation modes.
[0004] During steam generator operation, highly radioactive primary
circuit coolant is pumped through it. For this reason, NPP steam
generators are installed inside the reactor building containment
and the containment dimensions are greatly influenced by the steam
generator dimensions.
[0005] Since the development of reactor plants for nuclear power
plants with water-cooled water-moderated power reactors (VVER), two
approaches to steam generator design have been developed: vertical
and horizontal steam generators. In the first case, a steam
generator has a vertical pressure vessel and vertical U-shaped
heat-exchange tubes embedded in a horizontal tube sheet. In the
second case, a steam generator has a horizontal pressure vessel and
horizontal heat-exchange tubes embedded in vertical inlet and
outlet headers of the primary circuit coolant. Currently, the both
design concepts have evolved into well-established but different
technological trends. The claimed invention relates to the
horizontal steam generator concept, to its application in reactor
plants in combination with VVER type reactors.
BACKGROUND OF THE INVENTION
[0006] According to the background of the invention, there are
different designs of horizontal steam generators with varying
reliability, dimensions, capacity, component density of
heat-exchange tube bundles, arrangement of internals, specific
amount of metal per structure, etc.
[0007] The steam generator disclosed in International Application
WO9320386 issued on Oct. 14, 1993, IPC F22B1/02, has a horizontal
pressure vessel and a horizontal heat-exchange tube bundle
installed in the same, the tubes are embedded in vertical inlet and
outlet headers of the primary circuit coolant. A feed water supply
device is located in the center of the heat-exchange tube bundle,
which results in a significant horizontal break in the steam
generator vessel filling with the heat-exchange surface. Low power,
increased specific amount of metal per structure and lower
durability of the reactor plant steam generator are the
consequences of insufficient steam generator pressure vessel
filling with heat-exchange tubes.
[0008] A horizontal steam generator is disclosed in Russian Utility
Model Patent No. 100590 issued on Dec. 20, 2010, IPC: F22B37/00.
The horizontal steam generator comprises a vessel with an
elliptical bottom welded to each end of the same, the bottom
comprises a ferrule with a flat lid with, according to the claimed
utility model, the ratio between the average ferrule height and
ferrule bore is between 0.1 and 0.9. This technical solution is
designed to reduce steam generator dimensions for facilitating its
delivery from the manufacturing plant to its place of assembly and
increasing the free space in the steam generator box. The
longitudinal dimension is reduced due to a shorter ferrule, but not
a change in the steam generator pressure vessel length, i.e. the
device does not reduce specific amount of metal per structure.
[0009] Foreign counterparts of VVER reactors manufactured in Russia
are PWR type reactors (pressurized water reactor). Reactor plants
with PWR type reactors are usually equipped with vertical steam
generators.
[0010] Unlike the above steam generators with a vertical pressure
vessel, horizontal steam generators have the following known
peculiar aspects resulting from their design:
[0011] moderate steam load allows to apply a simple separation
scheme while reliably ensuring the required water content of steam,
moderate medium flow rate in the secondary circuit eliminates the
vibration hazard in the heat-exchange tubes and other elements of
the steam generator, the vertical cylindrical inlet and outlet
headers of the primary circuit prevents accumulation of sludge
deposits on their surfaces and thus reducing the hazard of
corrosive damage of heat-exchange tubes in areas of their insertion
in the said headers, increased supply of water in the secondary
circuit increases reliability of reactor cooldown through the steam
generator in case the emergency feed water system is used, and the
accumulating capacity of such steam generator mitigates reactor
plant transient modes, the horizontal position of the heat-exchange
surface provides reliable natural medium circulation in the primary
circuit even when the water level is below the upper rows of
heat-exchange tubes, favorable conditions for primary circuit
coolant natural circulation in emergency conditions are provided,
convenient access to the heat-exchange tube bundle is provided for
maintenance and control both from the primary and secondary circuit
sides. There are no heat-exchange tubes in the lower steam
generator pressure vessel, where sludge may be deposited and
accumulate, therefore, in case of accumulation of corrosive
impurities in the lower part of the steam generator pressure
vessel, sludge can be flushed through the blowdown system and
nozzles.
[0012] According to the background of the invention, there are
inventions relating to the nuclear industry, including development
of horizontal steam generators based on vertical steam generator
engineering experience. For instance, U.S. Pat. No. 5,331,677
issued on Jul. 19, 1994, IPC: F22B37/00 discloses a reactor plant
equipped with a pressurized water reactor that includes a reactor,
a coolant pump with an inlet connected to an outlet of the reactor
vessel, a steam generator with an inlet connected to a
high-temperature pipeline at the outlet of the said pump and an
outlet of a low-temperature pipeline connected to an inlet of the
reactor vessel. The steam generator has a horizontally extended
vessel with a horizontal U-shaped heat-exchange tube bundle inside.
The heat-exchange tubes are inserted in a vertical tube sheet.
Application of a tube sheet in a horizontal steam generator design
has disadvantages due to high specific amount of metal per
structure, manufacturing complexity, complexity of provision of
leaktightness of the heat-exchange tube connection to the tube
sheet. Application of a tube sheet does not allow to install a
large number of tubes in such steam generator, as a result, they
are quite long. The design of the above steam generator is
approximately the same as the vertical steam generator design that
is positioned horizontally in the reactor plant. A special aspect
of the reactor plant is a small number of tubes in its steam
generators resulting from the fact that one tube sheet is installed
in the distribution chamber, i.e. the entire heat-exchange surface
is formed by single U-shaped tube loop. As a result, heat-exchange
tubes are long and their side walls are thin. This reduces the
operation reliability of the reactor plant as its steam generators
have a lower heat-exchange tube plugging margin and a higher
hydraulic resistance of the heat-exchange tubes on the primary
circuit side, which has an adverse effect on accident
propagation.
[0013] Radial arrangement of steam generators is another reactor
plant disadvantage resulting in increased reactor building
dimensions. This increases the complexity of the containment and
capital construction scope.
[0014] In terms of reliability and cost effectiveness, VVER-1000
reactors are well-proven at the existing nuclear power plants in
Russia and abroad. Naturally, reactor plant assemblies and parts
that require improvement are identified periodically in the course
of operation.
[0015] Thus, Russian Utility Model Patent No. 143541 issued on Jul.
27, 2014, IPC: G21C1/03 discloses a VVER-1000 reactor plant (RP)
with four primary circuit coolant circulation loops, each
containing a PGV-1000 steam generator and reactor coolant pump
(RCP). The RP primary circuit coolant circulation loop consists of
two parts. The first part is a hot circulation pipeline connecting
the RP and the steam generator, and the second part is a cold
circulation pipeline used to pump the primary circuit coolant from
the steam generator to the reactor with the RCP. The function of
each RP circulation loop is unconstrained transfer of the primary
circuit coolant through the steam generator and RCP from and to the
reactor. The main function of the steam generator is generation of
dry saturated steam due to heat transferred to the steam generator
from the nuclear reactor core by the primary circuit coolant. The
RP, steam generator and RCP are interconnected by means of a welded
pipeline with an inner diameter of 850 mm (DN850). The RP is
connected to the steam generator by the main circulation pipeline
with a vertical pipe bend with a radius of 1340 mm. Thermal
expansion and vibration of all primary circuit systems occurs under
the primary circuit water head. High temperatures and pressure of
the coolant affect pipeline bends and welded connections, which may
lead to their damage to the extent of cracking. In particular, the
utility model is designed to prevent a damage to weld No. 111 on
the circulation pipeline.
SUMMARY OF THE INVENTION
[0016] To solve the above problem, this utility model proposes
connecting the steam generator hot header and the hot circulation
pipeline via a small header such that the length of the hot
circulation pipeline from the lower end of the small header to the
hot circulation pipeline bend does not exceed 0.25 m and the length
of the cold circulation pipeline is designed to match the hot
circulation pipeline length.
[0017] Increased complexity of steam generator design and
manufacture is the disadvantage of this utility model. It is
suggested that an additional small header is welded to the main
outlet header by means of an extra welded connection, as it may not
be repaired, the operation reliability of the steam generator and
the reactor plant is decreased.
[0018] The purpose of the claimed invention is to improve the
performance of the reactor plant due to an increased number of
heat-exchange tubes in the steam generator pressure vessel without
a significant increase in its dimensions, with its possible
installation in the reactor building boxes with no increase in the
capital construction scope.
[0019] In addition, the steam generator heat-exchange tube number
is important for increasing the steam generator power to improve
steam parameters, in particular, pressure, which in its turn allows
to improve the reactor plant efficiency. Increase in the number of
heat-exchange tubes in the steam generator pressure vessel also
improves its durability, as in the event of a failure of one or
more tubes they may be plugged an the device operation may be
continued due to availability of additional heat-exchange tubes.
When the number of heat-exchange tubes in the steam generator
pressure vessel functioning as part of a reactor plant is
increased, the latter is cooled down more efficiently, i.e. the
critical heat flux ratio in the reactor core increases. Increase in
the number of heat-exchange tubes in the steam generator pressure
vessel also reduces the specific amount of metal per structure of
the vessel as the device capacity is increased in a smaller
vessel.
[0020] The technical result of the claimed invention application
consists in the increased heat transfer rate, reliability and
durability of the steam generator due an increased number of
heat-exchange tubes installed in the vessel with of serviceability
and ease of manufacturing of U-shaped tubes, and reduced specific
amount of metal per structure of the steam generator pressure
vessel provided at the same time.
[0021] The technical result of the claimed invention application
also includes increased reliability, durability and efficiency of
the reactor plant, reduced specific amount of metal per structure
of the reactor plant steam generators, and their ease of
manufacturing.
[0022] To solve the problem at hand, we claim a horizontal steam
generator for a reactor plant with a water-cooled water-moderated
power reactor comprising a cylindrical pressure vessel equipped at
least with one feed water supply connection pipe and one steam
removal connection pipe, and two elliptical bottoms, internals,
primary circuit coolant inlet and outlet headers connected to a
heat-exchange tube bundle forming a steam-generator heat-exchange
surface, the heat-exchange tube bundle being divided into banks by
intertubular tunnels, wherein distance S between the primary
circuit coolant header centerlines in the transverse direction of
the steam generator pressure vessel has been selected based on the
following ratio:
0.4 .ltoreq. S D vess .ltoreq. 0.6 , ##EQU00001##
where D.sub.vess is the steam generator pressure vessel inner
diameter, and steam generator length L.sub.v along the inner
surfaces of the elliptical bottoms has been selected based on the
following ratio:
L .kappa. = D vess + 2 [ ( ctg ( .alpha. 2 ) - 1 sin ( .alpha. 2 )
) ( B 1 2 + B 2 + ( .pi. D head 4 S head - 1 ) S h ) + ( .pi. D
head 4 S head - 1 ) S h 1 sin ( .alpha. 2 ) + .DELTA. ] + H hes 10
6 .pi. d N tb , ##EQU00002##
[0023] where: D.sub.head is the coolant header outer diameter in
the drilled part, mm,
[0024] .alpha. is the heat-exchange tube central bend angle,
deg.,
[0025] B.sub.1 is the width of the heat-exchange tube central
intertubular tunnel, mm,
[0026] B.sub.2 is the width of the heat-exchange tube intertubular
tunnel opposite to the coolant header, mm,
[0027] S.sub.head is the heat-exchange tube circumferential spacing
on the outer surface of the coolant header, mm,
[0028] Sh is the spacing between heat-exchange tubes in the
horizontal heat-exchange bundle row, mm,
[0029] H.sub.hes is the steam generator heat-exchange surface area,
m.sup.2,
[0030] N.sub.tb is the number of steam generator heat-exchange
tubes, pcs.,
[0031] d is the outer heat-exchange tube diameter, mm,
[0032] .DELTA. is the distance from the outer heat-exchange bundle
tube to the steam generator bottom inner surface along the
longitudinal steam generator axis, wherein central heat-exchange
tube bend angle .alpha. and distance .DELTA. have been selected
from the following ranges:
90.degree..ltoreq..alpha..ltoreq.150.degree. and
300.ltoreq..DELTA..ltoreq.1000 mm.
[0033] Possibility to install the maximum number of heat-exchange
tubes in the steam generator while ensuring serviceability,
reliability and heat transfer efficiency depends on selection of
the S distance between the centerlines of the primary circuit
coolant headers in the transverse direction of the steam generator
pressure vessel from the above empirical relation.
[0034] The reactor plant layout in the reactor building depends on
selection of the L.sub.v length as four large steam generators are
difficult to install within the limited containment space. In
addition, steam generator pressure vessel length L.sub.v selected
according to the claimed invention guarantees ease of manufacturing
of U-shaped tubes of the heat-exchange bundle making up the
heat-exchange surface of the steam generator, which is essential
for reactor plant integrity ad reliable operation.
[0035] According to the claimed invention, the steam generator
heat-exchange tubes bundle is filled with heat-exchange tubes from
bottom upwards continuously with vertical gaps between adjacent
tubes not exceeding the vertical spacing of tubes in the bundle.
The bundle is divided into banks by means of intertubular tunnels.
The vertical intertubular tunnel width is between 100 mm and 250
mm. Horizontal heat-exchange tubes are inserted in holes in
vertical headers of the primary circuit coolant. At the point of
connection to the coolant header, the heat-exchange tube bend shall
have a radius of at least 60 mm and, preferably, at least 100 mm.
To meet the coolant header side wall strength requirement, its
drilling area on the outer surface shall exceed the area of holes
drilled in it for heat-exchange tube connection by at least
20%.
[0036] In addition, the steam generator may include at least the
following internals: a feed water supply and distribution device
located above the heat-exchange tube bundle, an emergency feed
water supply and distribution device located in the steam space,
device for chemical reagent supply during steam generator flushing,
a submerged perforated sheet and an overhead perforated sheet.
[0037] The second object of the claimed invention is a reactor
plant with a water-cooled water-moderated power reactor and a
horizontal seam generator, including a nuclear reactor with four
circulation loops, each comprising a steam generator with a
horizontal bundle of heat-exchange tubes divided into banks by
means of intertubular tunnels and connected to primary circuit
coolant headers inside a cylindrical pressure vessel with
elliptical bottoms, a reactor coolant pump, and a primary circuit
coolant main circulation pipeline, wherein pressure vessel bore
D.sub.vess, distance S between the centerlines of the primary
circuit coolant headers in the transverse direction and steam
generator length L.sub.v along the inner surfaces of the elliptical
bottoms have been respectively selected based on the following
ratios:
0.148 D + 0.637 0.054 D 2 + 3.142 N tb S h S v k .ltoreq. D vess
.ltoreq. 1.827 H , 0.4 .ltoreq. S D vess .ltoreq. 0.6 , L .kappa. =
D head + 2 [ ( ctg ( .alpha. 2 ) - 1 sin ( .alpha. 2 ) ) ( B 1 2 +
B 2 + ( .pi. D head 4 S head - 1 ) S h ) + ( .pi. D head 4 S head -
1 ) S h 1 sin ( .alpha. 2 ) + .DELTA. ] + H hes 10 6 .pi. d N tb ,
##EQU00003##
[0038] where: D is the rated steam generator capacity, t/h,
[0039] N.sub.tb is the number of steam generator vessel
heat-exchange tubes, pcs.,
[0040] Sv, Sh is the spacing between heat-exchange tubes in
vertical and horizontal rows of heat-exchange bundle, respectively,
mm,
[0041] k is the arrangement identifier of heat-exchange tube bundle
in a bank (k=1 for in-line arrangement and k=2 for staggered
arrangement),
[0042] H is the steam generator vessel tube filling height, mm,
[0043] D.sub.head is the primary circuit header outer diameter in
the drilled area, mm,
[0044] .alpha. is the heat-exchange tube central bend angle,
deg.,
[0045] B.sub.1 is the width of the heat-exchange tube central
tunnel, mm,
[0046] B.sub.2 is the width of the heat-exchange tube tunnel
opposite to the coolant header, mm,
[0047] D.sub.head is the heat-exchange tube circumferential spacing
on the outer surface of the coolant header, mm,
[0048] H.sub.hes is the steam generator heat-exchange surface area,
m.sup.2,
[0049] d is the outer heat-exchange tube diameter, mm,
[0050] .DELTA. is the distance from the outer heat-exchange bundle
tube to the steam generator bottom inner surface along the
longitudinal steam generator axis, wherein heat-exchange tube bend
angle .alpha. and distance .DELTA. have been selected from the
following ranges:
[0051] 90.degree..ltoreq..alpha..ltoreq.150.degree. and 300
mm.ltoreq..DELTA..ltoreq.1000 mm.
[0052] To improve the seismic stability, the steam generator and
reactor coolant pump may be attached to the reactor building walls
by means of hydraulic snubbers.
[0053] To increase the cavitation margin by working chamber
temperature reduction, the reactor coolant pump may be installed
downstream the steam generator along the primary circuit coolant
flow in the circulation loop.
[0054] To improve the reactor plant operation reliability, two
reactor coolant pumps may be installed in each loop. That is, a
reactor coolant pump may be installed on both the hot and cold legs
of the main circulation pipeline in a circulation loop. Reliability
is increased by means of possibility of pump redundancy.
[0055] In another arrangement of the reactor plant, two reactor
coolant pumps of lower capacity may be installed in parallel on the
cold leg of the main circulation pipeline. This will allow to
reduce the pump dimensions, increasing the reliability margin and
improving reactor plant technical and economic performance.
[0056] In addition, provision may be made for gate valves on the
main circulation pipeline legs of the reactor plant. This would
allow to enhance the operation reliability of the reactor plant
making it possible to isolate the steam generator from the reactor
and perform repairs without shutting down the reactor plant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] The invention is illustrated by the following figures.
[0058] FIG. 1 shows a horizontal section of the containment with a
reactor plant installed in it.
[0059] FIG. 2 shows a horizontal section of the steam generator
pressure vessel.
[0060] FIG. 3 shows a horizontal section detail of the steam
generator pressure vessel at the point of heat-exchange tube
connection to the primary circuit coolant header.
[0061] FIG. 4 shows a cross-section of the steam generator along
the centerline of the primary circuit coolant inlet header.
[0062] FIG. 5 shows the heat-exchange tube staggered
arrangement.
[0063] FIG. 6 shows the heat-exchange tube in-line arrangement.
[0064] FIG. 7 shows a reactor plant (RP) primary circuit coolant
circulation loop with a reactor coolant pump (RCP) installed on the
cold leg of the main circulation pipeline (MCP).
[0065] FIG. 8 shows an RP primary circuit coolant circulation loop
with an RCP installed on the MCP cold leg and hot leg.
[0066] FIG. 9 shows an RP primary circuit coolant circulation loop
with two RCPs installed on the MCP cold leg.
[0067] FIG. 10 shows an RP primary circuit coolant circulation loop
with gate valves installed on the MCP cold leg and hot leg.
DETAILED DESCRIPTION
[0068] The reactor plant equipment, including steam generators, and
its safety systems shall be installed in the NPP reactor
compartment. The reactor compartment consists of a pressurized part
and unpressurized part. The primary circuit equipment and the
reactor are typically installed in the pressurized part.
[0069] FIG. 1 shows a horizontal section of containment 1 with a
reactor plant installed in it. The containment is designed as a
cylinder of prestressed reinforced concrete, its thickness, for
instance, for the VVER-1000 project, is 1.2 m, its inner diameter
is 45 m and height is 52 m.
[0070] A reactor 2 connected to steam generators 4 by means of a
main circulation pipeline (MCP) 3 is located in the central part of
the containment 1. Reactor coolant pumps (RCP) 5 are used to pump
the primary circuit coolant (pressurized water) from the steam
generators 4 to the reactor 2 and back through the MCP. To maintain
the pressure and compensate for coolant volume variation during its
heating or cooling, pressurizers 6 are additionally applied in the
reactor plant. As is shown in FIG. 1, the steam generators 4 occupy
a larger area than any other reactor plant equipment in the
containment. However, society development requires increased power
generation and increased reactor plant power from NPPs and,
therefore, increased an heat-exchange surface and dimensions of
steam generators, which can hardly be fit in reactor building boxes
already at this moment. Further increase of the area and size of
containments is uneconomical due to significant increase of the
scope and costs of NPP capital construction.
[0071] The claimed invention allows to increase heat transfer
intensity, reliably and durability of a steam generator by
increasing the number of heat-exchange tubes in its pressure
vessel, which allows to improve performance of the reactor plant
without any considerable increase in dimensions, making it possible
to fit steam generators in containment boxes of the specified
size.
[0072] The claimed horizontal steam generator 4 for a reactor plant
with a VVER reactor comprises a cylindrical vessel 7 equipped with
at least a feed water supply connection pipe 8 and a steam removal
connection pipe 9, two elliptical bottoms 10, internals, an inlet
header 11 and an outlet header 12 of the primary circuit coolant
connected to a heat-exchange tube bundle 13 making up a
heat-exchange surface of the steam generator, wherein the
heat-exchange tube bundle is divided into banks 14 and 15 by means
of intertubular tunnels 16. To solve the task at hand, distance S
(FIG. 2) between the centerlines of the headers 11 and 12 of the
primary circuit coolant in the transverse direction of the steam
generator pressure vessel 7 has been selected based on the
following ratio:
0.4 .ltoreq. S D vess .ltoreq. 0.6 , ##EQU00004##
where D.sub.vess is the steam generator pressure vessel inner
diameter, and steam generator length L.sub.v measured along the
inner surfaces of the elliptical bottoms has been selected based on
the following ratio:
L .kappa. = D head + 2 [ ( ctg ( .alpha. 2 ) - 1 sin ( .alpha. 2 )
) ( B 1 2 + B 2 + ( .pi. D head 4 S head - 1 ) S h ) + ( .pi. D
head 4 S head - 1 ) S h 1 sin ( .alpha. 2 ) + .DELTA. ] + H hes 10
6 .pi. d N tb , ##EQU00005##
[0073] where: D.sub.head is the coolant header outer diameter in
the drilled part, mm,
.alpha. is the heat-exchange tube central bend angle, deg.,
[0074] B.sub.1 is the width of the heat-exchange tube central
intertubular tunnel, mm,
[0075] B.sub.2 is the width of the heat-exchange tube intertubular
tunnel opposite to the coolant header, mm,
[0076] S.sub.head is the heat-exchange tube circumferential spacing
on the outer surface of the coolant header, mm. The above spacing
is measured as a distance from the center of one heat-exchange tube
to the center of its adjacent heat-exchange tube in a horizontal
row on the outer surface of the coolant header.
[0077] Sh is the spacing between heat-exchange tubes in the
horizontal heat-exchange bundle row, mm. The above spacing is
measured as a distance from the center of one heat-exchange tube to
the center of its adjacent heat-exchange tube in a horizontal row
on the outer surface of the coolant header as is shown in FIGS. 5
and 6.
[0078] H.sub.hes is the steam generator heat-exchange surface area,
m.sup.2. The steam generator heat-exchange surface area is measured
as a sum total of surface areas of the heat-exchange bundle
tubes.
[0079] N.sub.tb is the number of steam generator heat-exchange
tubes, pcs.
[0080] d is the outer heat-exchange tube diameter, mm.
[0081] .DELTA. is the distance from the outer heat-exchange bundle
tube 17 to the steam generator bottom 10 inner surface along the
longitudinal steam generator axis, in mm, wherein central
heat-exchange tube bend angle .alpha. and distance 4 have been
selected from the following ranges:
90.degree..ltoreq..alpha..ltoreq.150.degree. and
300.ltoreq..DELTA..ltoreq.1000 mm.
[0082] According to the claimed invention, the steam generator
heat-exchange tubes bundle 13 is filled with heat-exchange tubes
from bottom upwards continuously with vertical gaps b between
adjacent tubes not exceeding the vertical spacing of tubes in the
bundle, as is shown in FIGS. 5 and 6. Horizontal heat-exchange
tubes are inserted in holes in vertical headers 11 and 12 of the
primary circuit coolant. As is shown in FIG. 3, at the point of
connection to the coolant header, the heat-exchange tube bend shall
have radius Rh of at least 60 mm and, preferably, at least 100
mm.
[0083] The steam generator may include at least the following
internals: a feed water supply and distribution device 18 located
above the heat-exchange tube bundle 13, an emergency feed water
supply and distribution device 19 located in the steam space,
device 20 for chemical reagent supply during steam generator
flushing, a submerged perforated sheet 21 and an overhead
perforated sheet 22.
[0084] During steam generator 4 operation, the primary circuit
coolant is supplied from the reactor 2 to the steam generator inlet
header 11, distributed among the heat-exchange bundle 13 tubes and
flows through the same to the outlet header 12 transferring its
heat to the boiler water, i.e. the secondary circuit coolant
(medium) through the heat-exchange surface wall. Feed water is
supplied to the steam generator through the connection pipe 8 and
the feed water supply and distribution device 18 connected to the
same, making up the boiler water in the steam generator, and is
heated up by mixing with the steam-water mixture in it. Water
heated up to saturation is drawn into the steam generator
circulation circuit (secondary circuit). The secondary circuit
coolant boils on the steam generator heat-exchange surface and
moves up the circulation circuit riser sections. To separate water
from steam in the steam generator, a single-stage gravitation
settling separation is applied. Steam is removed from the steam
generator through steam tubes 9 in the upper part of the vessel
7.
[0085] Steam leaving the heat-exchange bundle 13 is compensated for
by means of water downward motion in the intertubular tunnels 16,
23 along the tube bank length, and in the gap between the steam
generator vessel and tube bundle.
[0086] The empirical formula ratio proposed for calculation of the
steam generator length Lv is based on the process requirements for
the heat-exchange surface tube bend near the steam generator
bottoms. The heat-exchange bundle tubes shall be U-shaped in three
bends. The angle of the central bend is between 90.degree. and
150.degree., and the distance between the heat-exchange bundle
outer tube and the inner bottom surface between 300 mm and 1000 mm,
which is essential in terms of the process and technical and
economic considerations. The preferable heat-exchange tube central
bend angle is 120.degree..
[0087] The formula 0.4.ltoreq.S/D.sub.vess.ltoreq.0.6 describes a
steam generator design with heat-exchange tube banks of almost the
same width. Provided that heat-exchange tube banks are equal in
width, when S/D.sub.vess=0.5, the largest number of heat-exchange
tubes can be fit in the steam generator, other things being equal,
which reduces steam generator pressure vessel specific amount of
metal per structure.
[0088] A steam generator may be assembled with a distance between
the headers in the transverse direction outside the specified
range, but the number of tubes in such steam generator will be less
than required for its efficient operation due to the fact that the
inner space of the vessel is not effectively used. Namely, if
distance S between the centerlines of the coolant headers in the
transverse direction is S.ltoreq.0.4D.sub.vess, a considerable
space in the central part of the steam generator adjacent to the
longitudinal section plane in the heat-exchange bundle area will
remain unfilled with heat-exchange tubes due to the reason
described below. To insert heat-exchange tubes in the coolant
header holes, they shall have specified bend radius Rh (FIG. 3),
and the length of a straight section at the end shall exceed the
depth of a hole in the header wall the tube is inserted in. In
addition, heat-exchange tube bend radii shall be at least 60 mm,
and preferably at least 100 mm to be inserted in the header
holes.
[0089] If distance S between the centerlines of the coolant headers
in the transverse direction is S.gtoreq.0.6D.sub.vess, a
considerable space in the peripheral part of the steam generator
adjacent to the vessel side walls in the area of the heat-exchange
bundle will remain unfilled with heat-exchange tubes for the above
reason, as to insert heat-exchange tubes in the coolant header
holes they shall have the specified bend radius, and the length of
a straight section at the end shall exceed the depth of the hole in
the header wall the tube is inserted in.
[0090] Manufacture of a steam generator with its vessel inner
diameter D.sub.vess, distance S between the centerlines of the
coolant headers in the transverse direction and length Lv (along
the inner surfaces of the elliptical bottoms) selected allows to
fit the largest number of heat-exchange tubes in the steam
generator pressure vessel of the selected size providing their
secure mounting, while obtaining steam with the required water
content in the vessel of the minimum diameter, and meeting the
requirements to the ease of manufacturing of U-shaped heat-exchange
tubes. Steam generator dimensions D.sub.vess are Lv are considering
its installation as part of a reactor plant in containment
boxes.
[0091] The reactor plant comprising the claimed steam generator is
shown in FIG. 1. It comprises a nuclear reactor 2 with four
circulation loops, each comprising a steam generator 4 with a
horizontal bundle 13 of heat-exchange tubes divided into banks 14
and 15 by intertubular tunnels 16 and connected to primary circuit
coolant headers 11 and 12 inside a cylindrical vessel 7 with
elliptical bottoms 10, a reactor coolant pump 5, and a main
circulation pipeline 3 of the primary circuit coolant, wherein
vessel 7 inner diameter D.sub.vess, distance S between the
centerlines of the primary circuit coolant headers 11 and 12 in the
transverse direction, and steam generator length Lv along the inner
surfaces of the elliptical bottoms 10 are selected, respectively,
by the following ratios:
0.148 D + 0.637 0.054 D 2 + 3.142 N tb S h S v k .ltoreq. D vess
.ltoreq. 1.827 H , 0.4 .ltoreq. S D vess .ltoreq. 0.6 , L .kappa. =
D head + 2 [ ( ctg ( .alpha. 2 ) - 1 sin ( .alpha. 2 ) ) ( B 1 2 +
B 2 + ( .pi. D head 4 S head - 1 ) S h ) + ( .pi. D head 4 S head -
1 ) S h 1 sin ( .alpha. 2 ) + .DELTA. ] + H hes 10 6 .pi. d N tb ,
##EQU00006##
[0092] where: D is the rated steam generator capacity, t/h,
[0093] N.sub.tb is the number of steam generator vessel
heat-exchange tubes, pcs.,
[0094] Sv, Sh is the spacing between heat-exchange tubes in
vertical and horizontal rows of heat-exchange bundle, respectively,
mm, as is shown in FIGS. 5 and 6,
[0095] k is the arrangement identifier of heat-exchange tube bundle
in a bank (k=1 for in-line arrangement and k=2 for staggered
arrangement),
[0096] H is the steam generator vessel tube filling height, mm, as
is shown in FIG. 4,
[0097] D.sub.head is the primary circuit header outer diameter in
the drilled area, mm,
[0098] .alpha. is the heat-exchange tube central bend angle,
deg.,
[0099] B.sub.1 is the width of the heat-exchange tube central
tunnel, mm,
[0100] B.sub.2 is the width of the heat-exchange tube tunnel
opposite to the coolant header, mm,
[0101] S.sub.head is the heat-exchange tube circumferential spacing
on the outer surface of the coolant header, mm,
[0102] H.sub.hes is the steam generator heat-exchange surface area,
m.sup.2,
[0103] d is the outer heat-exchange tube diameter, mm,
[0104] .DELTA. is the distance from the outer heat-exchange bundle
tube to the steam generator bottom inner surface along the
longitudinal steam generator axis, wherein heat-exchange tube bend
angle .alpha. and distance .DELTA. have been selected from the
following ranges:
[0105] 90.degree..ltoreq..alpha..ltoreq.150.degree. and 300
mm.ltoreq..DELTA..ltoreq.1000 mm.
[0106] To improve the seismic stability, the steam generator and
reactor coolant pump may be attached to the reactor building walls
by means of hydraulic snubbers 24.
[0107] FIGS. 7-9 show arrangement options of the proposed reactor
plant as exemplified by one of the four circulation loops, with the
MCP cold leg designated as item 25 and the hot leg as 26.
[0108] To increase the cavitation margin by working chamber coolant
temperature reduction, as shown in FIG. 7, the reactor plant 2
coolant pump 5 may be installed downstream the steam generator 4
along the primary circuit coolant flow in the circulation loop on
the MCP 3 cold leg 25.
[0109] In the other option shown in FIG. 8, to improve the reactor
plant operation reliability, two reactor coolant pumps 5 may be
installed in each circulation loop. That is, a reactor coolant pump
5 may be installed on both the hot leg 26 and cold leg 25 of the
main circulation pipeline in a circulation loop. Reliability is
increased by means of possibility of pump redundancy.
[0110] In another arrangement of the reactor plant, two reactor
coolant pumps 5 of lower capacity may be installed in parallel on
the cold leg 25 of the main circulation pipeline as shown in FIG.
9. This will allow to reduce the pump dimensions, increasing the
reliability margin and improving reactor plant technical and
economic performance.
[0111] In addition, provision may be made for gate valves 27 on the
main circulation pipeline legs 25 and 26 of the reactor plant as
shown in FIG. 10. This would allow to enhance the operation
reliability of the reactor plant making it possible to isolate the
steam generator from the reactor and perform repairs without
shutting down the reactor plant.
[0112] The reactor plant functions as follows.
[0113] The process flow diagram of the reactor plant is
double-circuit. The primary circuit is radioactive and located in a
containment 1, comprising a VVER water-cooled water-moderated power
reactor 2 and four circulation loops of the MCP 3, through which
the primary circuit coolant, pressurized water (160 kgf/cm.sup.2),
is pumped to a reactor core 2 by means of reactor coolant pumps 5.
Water temperature at the reactor inlet is approximately 289.degree.
C., and 322.degree. C. at the outlet. The water heated in the
reactor 2 is supplied to steam generators 4 through four MCP
pipelines 3. A steam pressurizer 6 maintains the pressure and level
of the primary circuit coolant.
[0114] The secondary circuit is non-radioactive, consists of an
evaporator and a feed water plant, a unit demineralization plant
and a turbine generator (not shown). The primary circuit coolant is
cooled down in the steam generators 4 transferring heat to the
secondary circuit water. The saturated steam produced in the steam
generators 4 is supplied to the turbine generator rotating the
power generator by steam removal connection pipes 9 and the steam
header.
Example
[0115] An NPP with a VVER reactor is constructed. To provide
reliable reactor cooldown, the steam generator shall have the
following parameters:
[0116] steam generator heat-exchange surface area H.sub.hes=6000
m.sup.2.
[0117] A steam generator with the following parameters has been
manufactured for the reactor plant:
[0118] steam capacity per reactor plant steam generator D=1500 t/h,
outer diameter of the primary circuit header in the drilled part
D.sub.head=1200 mm, width of the heat-exchange tube central tunnel
B.sub.1=200 mm, width of the heat-exchange tube tunnel opposite to
the coolant header B.sub.2=200 mm, outer heat-exchange tube
diameter d=16 mm, spacing between heat-exchange tubes in the
horizontal heat-exchange bundle row S.sub.h=24 mm, spacing between
heat-exchange tubes in the vertical heat-exchange bundle row
S.sub.v=22 mm, number of heat-exchange tubes in the steam generator
N.sub.tb=10,000 pcs, heat-exchange bundle arrangement identifier
k=1 for the in-line arrangement, steam generator vessel tube
filling height H=2300 mm,
[0119] According to the claimed invention, steam generator pressure
vessel inner diameter D.sub.vess is selected from the range based
on the following ratio:
0.148 D + 0.637 0.054 D 2 + 3.142 N tb S h S v k .ltoreq. D vess
.ltoreq. 1.827 H , 2825 mm .ltoreq. D vess .ltoreq. 4202 mm .
##EQU00007##
[0120] Distance S between the centerlines of the coolant headers in
the transverse direction is selected from a range based on the
following ratio:
0.4 .ltoreq. S D vess .ltoreq. 0.6 , ##EQU00008##
then 1130 mm.ltoreq.S.ltoreq.2521 mm.
[0121] Steam generator length Lv (along the inner surfaces of the
elliptical bottoms) is selected from a range based on the following
ratio:
L .kappa. = D head + 2 [ ( ctg ( .alpha. 2 ) - 1 sin ( .alpha. 2 )
) ( B 1 2 + B 2 + ( .pi. D head 4 S head - 1 ) S h ) + ( .pi. D
head 4 S head - 1 ) S h 1 sin ( .alpha. 2 ) + .DELTA. ] + H hes 10
6 .pi. d N tb , ##EQU00009##
at 90.degree..ltoreq..alpha..ltoreq.150.degree. and 300
mm.ltoreq..DELTA..ltoreq.1000 mm, then 13,790
mm.ltoreq.L.sub.v.ltoreq.16,807 mm.
[0122] If steam generator pressure vessel inner diameter D.sub.vess
is less than 2825 mm, then it will not be possible to securely
mount heat-exchange tubes in such seam generator by means of
spacing elements, therefore, there will be no space left for the
same, and thus the steam generator design reliability requirement
will not be met. A steam generator pressure vessel with an inner
diameter exceeding 4202 mm is uneconomical to install in a reactor
plant as it increases its specific amount of metal per structure,
while the water content of the steam generated and plant efficiency
are not improved, but the containment size is increased. The steam
generator contains the same heat-exchange surface, therefore, the
coolant remains within the same temperature range in the reactor
plant MCP. As a result, the critical heat flux ratio does not
increase in the core.
[0123] Steam generator length Lv (along the inner surfaces of the
elliptical bottoms) of less than 13,790 mm does not provide the
best performance of bending and fastening of U-shaped tubes in a
bundle as the tube bending angle exceeds 150.degree., and the
distance between the outer tubes of the bundle and the vessel
bottom is less than 300 mm, which prevents installation of a bundle
support.
[0124] Steam generator length Lv (along the inner surfaces of the
elliptical bottoms) of more than 16,807 mm is not reasonable, as an
increase in the steam generator pressure vessel length does not
improve steam quality indicators, such as dehydration, and the
heat-exchange surface area remains constant at 6000 m.sup.2 due to
the fact that the steam generator length is not increased due to a
greater number of heat-exchange tubes or heat-exchange surface
area, but by closer bending angles and excessive gaps between the
heat-exchange tube bundle and the steam generator bottoms. This
results in an increased specific amount of metal per structure of
the reactor plant steam generator without an increase in the
critical heat flux ratio in the core or improvement of steam water
content and pressure parameters in the steam generator, while the
containment size is increased without any positive technical effect
for reactor plant operation.
[0125] If distance S between the centerlines of the coolant headers
in the transverse direction of at least 1130 mm is selected, the
central part of the heat-exchange bundle of the steam generator
will not be filled with tubes. As to fasten a heat-exchange tube in
a hole in the primary circuit coolant side wall, its end shall have
a straight section with a length exceeding the depth of such hole.
If the condition is not fulfilled, then such heat-exchange tube
cannot be placed and fastened in the coolant header side wall hole.
Therefore, if the central part of the steam generator heat-exchange
bundle is not filled with tubes, it will not allow to provide the
specified number of heat-exchange tubes in the steam generator or
the specified dimensions of the heat-exchange surface, which will
compromise the performance indicators of the reactor plant.
[0126] If distance S between the centerlines of the coolant headers
in the transverse direction of more than 2521 mm is selected, then
it will not be possible to install the heat-exchange tube bundle
near the steam generator pressure vessel side wall, which will not
allow to provide the specified heat-exchange surface area and
performance indicators of the reactor plant.
* * * * *