JPH0684803B2 - Steam generator for nuclear power plant - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to the field of steam generators for commercial nuclear power plants, and more particularly to an apparatus for preventing vibration of heat transfer tubes of steam generators. More specifically, a device for eliminating a gap between a heat transfer tube of a steam generator and a vibration-proof rod arranged between columns of the heat transfer tube, thereby preventing vibration of the heat transfer tube during operation of the steam generator. It is about.

Description of the Prior Art Nuclear power plants have been safely producing power for many years. The operating principle of such a commercial nuclear power plant is well known. When the core containing the fissile fuel reaches criticality, it produces heat. In the field of pressurized water reactors, this heat is taken up by the reactor coolant, which consists of water. This water reactor coolant also acts as a nuclear moderator. The nuclear moderator is a material that heats fast neutrons in order to increase the possibility that neutrons further cause fission and sustain the nuclear reaction.

The heat generated in the core is transferred to the reactor coolant as it passes through the core. The reactor coolant then transfers the absorbed heat to another medium consisting of water, which is then converted to steam. After this, the steam is used for power generation by a conventional steam turbine power generator.

Reactor coolant transfers its heat to a secondary medium in a steam generator specially designed for the field of nuclear power generation. The structure of such a nuclear steam generator is well known in the art. Generally, a steam generator has a plurality of small diameter heat transfer tubes housed in a pressure resistant vessel in a manner such that heat transfer generates steam and promotes steam generation.

In particular, some nuclear steam generator constructions have a barrel that consists of an elongated circular cylinder with fixed spherical ends. A number of U-shaped heat transfer tubes oriented along the longitudinal axis of the barrel are arranged in the lower portion of the body of the steam generator. This lower part has a lower end, that is, a bottom end, to which a generally hemispherical water chamber is connected. The water chamber is divided by a partition into a first half, commonly known as the hot leg, and a second half, commonly known as the cold leg. Hot reactor coolant from the reactor is introduced into the steam generator and introduced into the hot leg through the primary coolant inlet nozzle. After this, the reactor coolant flows from the hot legs into the receiving ports of the plurality of U-shaped heat transfer tubes, passes through the heat transfer tubes, and then flows through the cold legs. Finally, the reactor coolant exits the steam generator through the primary coolant exit nozzle.

The part of the steam generator mainly containing the tube bundle of the U-shaped heat transfer tubes and the water chamber is commonly referred to as the evaporator part. In addition, the steam generator has a steam drum portion located at the upper end of the cylindrical barrel of the steam generator. A steam separator is arranged in this steam drum portion. The water supply flows into the steam generator through an inlet nozzle arranged in the upper part of the cylindrical body. This water supply is sprinkled, mixed with the water withdrawn by the steam separator and then travels down an annular flow path surrounding the tube bundle. The feedwater then reverses direction and flows upwardly outside the heat transfer tubes in the tube bundle, where it absorbs heat from the reactor coolant flowing in the heat transfer tubes. The absorbed water causes the feed water to boil and generate steam. The steam generated by the boiling water rises into the steam drum section. Then, after the steam separator takes out the water contained in the steam, the steam flows out from the steam generator through the steam outlet. After this, the steam flows to a steam turbine that is connected to the generator. The steam from the steam turbine is then condensed and carried through another path to the steam generator for continued flow cycling.

The heat transfer tube is supported at its open end by the usual method in which the open end of the U-shaped heat transfer tube is seal-welded to the tube sheet which is arranged transversely to the longitudinal axis of the steam generator. It A series of tube support plates arranged in spaced apart relationship are provided along the portion of the heat transfer tube to support the straight portion of the heat transfer tube. The upper tube support assembly is used to support the U-shaped portion of the heat transfer tubes in the tube bundle. The upper tube support assembly comprises a plurality of retaining rings arranged in spaced relation to each other on the outer circumference of the tube bundle.

The retaining ring, like the tube support plate, is oriented substantially transverse to the longitudinal axis of the steam generator. The shape of each retaining ring is substantially elliptical and matches the outer shape of the tube bundle at a particular position on the retaining ring. Therefore, the size of the ellipse of the retaining ring becomes smaller toward the upper end of the tube bundle. Therefore, the uppermost retaining ring is relatively small because the shape of the bundle is located at the top of the bundle, where the shapes of the bundle rapidly converge.

Each of the retaining rings is connected to a plurality of anti-vibration bars, which are generally located between each row of U-shaped sections of the heat transfer tube. In some steam generators, the anti-vibration rods consist of V-folded rods so that there is an angle between them.
The legs of the book are formed. The V-shaped anti-vibration rod is inserted between successive rows of heat transfer tubes of the steam generator. The V-shaped ends of the vibration-proof rods are inserted between the heat transfer tubes, and the free ends of the vibration-proof rods are welded to opposite sides of a suitable retaining ring. In this way, each heat transfer tube in the tube bundle is supported by the vibration-proof rod at a plurality of positions at regular intervals along the length of the curved portion, that is, the U-shaped portion. This arrangement provides linear support while still allowing feed water to flow around and between the curved portions of the heat transfer tubes of the steam generator. In other words, the anti-vibration rod provides support but does not substantially obstruct the flow of feed water.

The anti-vibration rod is made to prevent excessive vibration of the individual heat transfer tubes in the entire tube bundle. It is well known that the vibration is caused by the flow of water and steam passing through the heat transfer tube. Vibrations induced by such flow can damage the heat transfer tubes. Also, the U-shaped portion of the tube bundle is adversely affected by vibrations, and its curved shape makes it very difficult to provide sufficient support to eliminate flow-induced vibrations. Is well known. Furthermore, it is well recognized that current hydraulic and dynamic response techniques do not allow the exact root cause of vibration to be determined and cannot be completely eliminated. Accordingly, mechanical means have been attempted to completely or at least substantially eliminate the problem of vibration. Although the advent of anti-vibration rods or similar techniques greatly reduced the magnitude and presence of vibrations, they did not completely eliminate damaging vibrations.

The mechanical appearance of the curved or bent portion of the heat transfer tubes in the tube bundle constitutes a major obstacle to mechanical solutions to this problem.

The U-shaped heat transfer tube in the tube bundle has a dimensional tolerance regarding its outer diameter. There is also vibration due to the elliptical shape of the heat transfer tube resulting from bending. Further, the spatial relationship between adjacent heat transfer tubes changes even within set design limits. Therefore, there are dimensional tolerances even for the small spaces between the heat transfer tubes of the steam generator. There are also dimensional tolerances with respect to the outer diameter of conventional vibration-proof rods, as described above, which are generally rectangular rods. The anti-vibration rod may be constructed of square, oval, or other shapes of uniform or non-uniform cross section. However, even if a special shape is selected, there are dimensional tolerances related to the size of the vibration-proof rod. These dimensional tolerances and dimensional differences combine to prevent removal of the gap between the anti-vibration rod and the heat transfer tube of the steam generator.
Of course, any gap is not preferable because it allows the heat transfer tube to vibrate and allows the relative movement between the heat transfer tube and the vibration-proof rod. Relative motion can cause the heat transfer tubes of the steam generator to wear and then break. Many attempts have been made in the past to minimize this gap. Unfortunately, however, reducing the size of the gap only reduces the scale of the problem, it does not eliminate it.

Japanese Unexamined Patent Publication No. 61-122495 discloses a new method for removing a gap between a heat transfer tube of a steam generator and a vibration-proof rod. The publication proposes a method of expanding a hollow vibration-proof rod at a proper position between columns of heat transfer tubes of a steam generator in order to remove a gap due to a difference in size. While such a method is clearly a step in the right direction, it also has limitations. Such a method is difficult to use with steam generators already in operation. That is, since such a steam generator may have radioactivity or is actually present, it is necessary to install it underwater using a remote control jig, and the space between the adjacent heat transfer tubes is the steam generator. This is because it changes further due to the accumulation of deposits due to the operation of. In this expansion-based method, it is also difficult to control the expansion in order to obtain the final adjusted clearance. Then, another member or device for preventing vibration of the heat transfer tube of the steam generator and relative movement between the vibration-proof rod and the heat transfer tube of the steam generator is required.

Therefore, an object of the present invention is to provide a steam generator provided with a device for preventing vibration during operation of a heat transfer tube of the steam generator.

Another object of the present invention is to provide a steam generator capable of substantially eliminating any gap between the vibration-proof rod and the heat transfer tube of the steam generator.

Another object of the present invention is to provide a steam generator equipped with a vibration-proof rod that can be easily attached to a steam generator that is already in operation and may have inorganic substances adhering to the heat transfer tubes of the steam generator. To provide a container.

Yet another object of the present invention is to provide a steam generator with a vibration-proof rod that can be easily attached to a steam generator that has already been operated and may be radioactive.

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a body and a plurality of heat transfer tubes having a substantially U-shaped outer shape in which a series of tube rows are vertically arranged in the body. A heat transfer tube adapted to heat feed water flowing around the outer periphery of the heat transfer tube by the flow of hot reactor coolant in the heat transfer tube, and the heat transfer tube as a result of operation of a steam generator Steam for nuclear power plants comprising a flexible vibration-proof rod arranged between adjacent rows of tubes so as to substantially eliminate any gaps between the adjacent heat transfer tubes so as to prevent vibration of the tubes. In the generator, each of the flexible anti-vibration rods comprises two flexible spacing straps interconnected by ribs at longitudinally spaced locations, the flexible spacing bars being in the gaps between each row of tubes. The ribs of the anti-vibration rod have the flexibility resistance in the gap between the adjacent rows of tubes. The flexible vibration-proof rods are disposed substantially in the center of the ribs between the ribs in the longitudinal direction, and the flexible vibration-proof rods have a plurality of U-shaped portions at the ends of the flexible vibration-proof rods. It is characterized in that it is attached to a holding ring arranged so as to surround the outer periphery of the heat transfer tube, and is attached to the holding ring between the tube rows.

Various other objects, advantages and features of the invention will be apparent to those skilled in the art from the following description in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made to the drawings in which the same or corresponding parts are designated by the same reference numerals throughout the drawings, and in particular in FIGS. Represented by To the extent that the steam generator is described and explained in the description of the prior art above, its description and description of operation also applies to the following examples.

Nuclear steam generator 10 comprises a substantially cylindrical barrel having an upper portion 11 and a lower portion 12. A hemispherical head, or water chamber 13, is sealingly attached to the lower portion 12 and another head 14 is sealingly attached to the upper portion 11. A tube bundle 15 of U-shaped heat transfer tubes is represented in the lower part 12. One open end of the tube bundle 15 is
It communicates with the hot leg 16 and the primary coolant inflow port (inlet nozzle) 17 in the water chamber 13. The other open end of the tube bundle 15 communicates with the cold leg 18 and the primary coolant outlet (outlet nozzle) 19 in the water chamber 13. The partition wall 20 separates the primary coolant inlet port 17 and the primary coolant outlet port 19 from each other. Further, the partition wall 20 separates the hot leg 16 and the cold leg 18 in the water chamber 13. Therefore, the hot reactor coolant flows into the steam generator 10 via the inlet nozzle 17, enters the tube bundle 15 through the hot leg 16 and flows out through this tube bundle 15. The cooled coolant then passes through the cold leg 18 and exit nozzle to continue the flow cycle.
It flows out from 19 and is returned to the reactor.

The lower part 12 of the steam generator 10, which mainly comprises the tube bundle 15 and the water chamber 13, is called the evaporator part. The upper part 11 of the steam generator 10 is commonly referred to as the steam drum part, which has a steam separator 21. The feed water enters the steam generator 10 through the inlet nozzle 22 and is fed into the steam separator.
Mix with the water removed by 21. The water supply flows downward in an annular flow path around the tube bundle 15 and is guided into the tube bundle 15 at the bottom thereof. Then, the mixed water of this water supply and recirculation water is
The water flows upward through the tube bundle 15, where the mixed water is heated by the water flowing in the electric heating tubes 25 of the tube bundle 15 and boils. The steam generated by the boiling water supply rises into the steam drum portion 11, where the steam separator 21 takes out the water contained in the steam, after which the steam exits via the steam outlet nozzle 23. Go. The steam then flows to a steam turbine (not shown) and is then returned to the steam generator to continue the cycle.

The U-shaped heat transfer tube 25 is supported in the form of a tube bundle 15 by a series of support plates 26 along the longitudinal direction of its straight line portion. The bent or U-shaped portion of the heat transfer tube 25 is supported by an assembly of retaining rings 27a, 27b, 27c. Each retaining ring is generally circular or elliptical in shape, with retaining ring 27b smaller than retaining ring 27a and then retaining ring 27c smaller than retaining ring 27b. A plurality of sets of flexible vibration-proof rods 28 are arranged between adjacent rows of the U-shaped heat transfer tubes 25. One such set of vibration-proof rods 28 is the second
As clearly shown in the figure, another continuous set of similar anti-vibration bars 28 are placed before and after the set shown. Each anti-vibration rod 28
a, 28b, and 28c are V-shaped and have different groove angles, and both ends of each have a corresponding retaining ring 27.
It is fixed by welding or the like to the symmetric points of a, 27b, and 27c that face each other. FIG. 2 shows a schematic cross section of the tube bundle 15, where the vibration-proof rods 28a, 28b, 28c are arranged so as to support the U-shaped portion of the heat transfer tube 25 (in particular, the rows and columns of the heat transfer tube 25). Array).

A portion of the flexible anti-vibration rod 28 disclosed by the present invention is shown in FIG. The cross section of the vibration-proof rod 28 is shown in FIG. The vibration-proof rod 28 may have a square or rectangular sectional shape as a whole. Anti-vibration rod 28
Is provided so as to penetrate the vibration-proof rod 28 along the longitudinal axis of the. In this way, the flexible support plate 31 (separation strap) is formed on each support side of the vibration-proof rod 28. The thickness 32 of the support plate 31 and the length 33 of the groove 30 can be variously changed so that the flexibility of the support plate 31 has a required degree.
In addition, as will be explained more fully below, the overall spring rate of the vibration-proof rod 28 when the vibration-proof rod 28 is installed to support the heat transfer tubes 25 of the steam generator as shown in FIG. That is, the thickness 31 can be varied along the length 33 of the groove 30 to obtain the compliance factor (not shown).

The ribs 34 are provided at the ends of the grooves 30 in a direction crossing the support plate 31 and in a direction crossing the longitudinal axis of the vibration-proof rod 28. The rib 34 prevents the support plate 31 from being deformed at that position. Further, the rib 34 is a suitable member for limiting the length 33 of the groove 30.

The anti-vibration rod 28 may be formed from a single solid elongated rod having a machined hollowed groove 30 and a rib 34 of unholed portion. Alternatively, the support plate 31 and the rib 34
May individually be welded together to form the shape shown in FIGS. 3 and 4. Further, the two support plates 31 and the one cylindrical rib may be welded to each other.

The spring rate of the groove portion between the continuous ribs 34 of the vibration-proof rod 28 is determined by appropriately adjusting the thickness 32 of the support plate 31 and the length 33 of the groove 30 in the transverse direction of the heat transfer tube 25 of the steam generator. It is designed to be smaller than the rate. Further, the elastic deformation of the vibration-proof rod 28 at the position of the heat transfer tubes 25 in the same row and adjacent to the load applied by the heat transfer tubes 25 provided between the adjacent heat transfer tubes 25 is minimized. From need to groove 30
Limited to a length of 33. However, the actual spring rate of the anti-vibration rod 28 relative to the spring rate of the heat transfer tube 25 is one factor consisting of a series of coupled spring rates of the anti-vibration rod 28 in successive rows on each side of the heat transfer tube 25 in question.

FIG. 5 schematically shows one of the arrangements of the vibration-proof rods 28 placed between successive rows of heat transfer tubes 25. Row 1, row 2 and row 3 comprise successive rows of heat transfer tubes 25 of the steam generator. Columns 1 to 6 consist of adjacent columns of heat transfer tubes 25 in each row of heat transfer tubes 25. The numbers in the rows and columns have no meaning other than that they are consecutive. Anti-vibration rod 28 ', 28 ", 28
Are arranged so that the ribs 34 in successive columns of the vibration-proof rods 28 alternate. Thus, the rib 34 ″ is aligned with the groove 30 ′ and the longitudinal center of the groove 30. Such an arrangement offsets the effect of the stiffness of the rib 34 on the spring rate of the vibration-proof rod provided by the heat transfer tube 25. For example, in the heat transfer tubes 25 in columns 2 and 3, the spring rate R ″ of the short length portion of the support plate 31 ″ between the contact point S and the rib 34 ″ of the heat transfer tube 25, the contact point T and the rib 34 ′ are provided. Will receive an effective spring rate R consisting of the spring rate R'of the long length of the support plate 31 'between. Since the effective continuous spring rate is always less than the smallest individual spring rate in that continuous spring rate, the combined spring rate R is less than either spring rate R ', R ". The smallest spring rate (of plate 31 ') is heat transfer tube 25
Since it is considerably smaller than the spring rate of the cut part of
Will not be subject to a large or damaging load.

The arrangement shown in FIG. 5 does not limit the invention. Many other arrangements are possible with alternative lengths 33 of groove 30 and are intended to be within the scope of this invention. In particular, the present invention may be used in combination with the vibration-proof rod of the inflatable type as shown in the above-mentioned JP-A-61-122495. In this case, the expansion of these vibration-proof rods presses the heat transfer tube to bring it into contact with the support plate 31 of the present invention. Further, in addition to achieving the primary objective of substantially eliminating any gap between the vibration isolator and the heat transfer tubes of the steam generator, the present invention provides for the accumulation of deposits as a result of the operation of the steam generator. It will also be appreciated that the effect of load on the heat transfer tubes is substantially canceled.

[Brief description of drawings]

1 is a partial sectional perspective view of a nuclear steam generator having a U-shaped bent heat transfer tube to which the vibration-proof rod of the present invention is applied, and FIG. 2 is an upper portion of the steam generator of FIG. FIG. 4 is a schematic explanatory view of the vent portion of the heat transfer tube and a typical installation position of the vibration-proof rod of the present invention, taken along the axial direction, and FIG. The figure is the third
FIG. 5 is a sectional view of the vibration-proof rod taken along line 4-4 in FIG. 5, and FIG. 5 shows a method of installing the vibration-proof rod according to the present invention between rows of heat transfer tubes of a steam generator. FIG.
In the drawing, 10 ... Steam generator, 11 ... Upper part of body 12 ... Lower part of body, 15 ... Tube bundle 25 ... Heat transfer tube, 28 ... Vibration-proof rods 27a, 27b, 27c ... Holding ring 30 ... Groove, 34 ... Rib 31 ... Support plate (separation strap)

Front Page Continuation (72) Inventor Thomas Arthur Pittard Clearview Drive, Greensburg, PA, Pennsylvania, USA 1331 (72) Inventor Normal Landlet Singleton McAlister Drive, Pittsburgh, PA, USA 121 (56) Bibliography Showa 57-172204 (JP, U) Showa 53-160857 (JP, U)

Claims (1)

[Claims] 1. A heat transfer tube having a body portion (11, 12) and a plurality of heat transfer tubes having a substantially U-shaped outer shape which are arranged vertically in a series of tube rows in the body portion (11, 12). The heat transfer pipe (25) adapted to heat the feed water flowing around the outer circumference of the heat transfer pipe (25) by the flow of the high-temperature reactor coolant in the heat transfer pipe (25), and steam generation. The adjacent heat transfer tubes (2) to prevent vibration of the heat transfer tubes (25) as a result of the operation of the heat exchanger.
In a steam generator for a nuclear power plant comprising a flexible vibration isolator (28) arranged between adjacent rows of pipes for substantially eliminating any gaps between them, said flexible Each of the vibration-proof rods (28) is composed of two flexible spacing straps (31) connected to each other by ribs (34) at longitudinally spaced locations, and the flexible strips are provided in the gaps between the rows of tubes. The ribs (34) of the flexible vibration-proof rods are arranged substantially at the center in the longitudinal direction between the ribs (34) of the flexible vibration-proof rods in the gap between the adjacent tube rows. The flexible vibration-proof rod (28) is a holding ring arranged at the end of the flexible vibration-proof rod so as to surround the outer circumference of the heat transfer tubes (25) in the U-shaped portion of the heat transfer tube (25). (27a, 27b, 27c) attached to the retaining ring (27a, 27b) between the tube rows.
b, 27c) mounted on a steam generator for a nuclear power plant.