DE2644196A1 - STEAM GENERATOR - Google Patents

Description

Patent attorneys Dipl.-Ing. H. Weickmann, Dipl.-Phys. Dr. K. Fincke

Dipl.-Ing. R A.Weickmann, Dipl.-Chem. B. Huber

dJuMi

Case G-1073 8 Munich 86, den

PO Box 860820

MÖHLSTRASSE 22, CALL NUMBER 98 39 21/22

GENERAL ATOMIC COMPANY, 10955 John Jay Hopkins Drive, San Diego, California (U.S.A.)

Steam generator

The invention relates to a steam generator as used in connection with the generation of steam for driving Steam turbines is used. In particular, the invention relates to a steam generator specifically designed for use in connection with a gas-cooled nuclear reactor in a plant for the generation of electrical energy is suitable.

Since the emergence of power nuclear reactors are essential steps towards efficient and economic generation of electrical power from thermal energy derived from or generated by these reactors has been undertaken. An important factor in achieving this goal is the operation of such reactors at Temperatures high enough to allow direct generation of steam at temperatures and pressures, which are suitable for the operation of steam turbines with high performance or high efficiency. In this Connection haj: the current reactor technology to the Development of gas-cooled high-temperature reactors which, when used in conjunction with a suitable steam turbine

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system having the ability to generate electrical power in an amount and at such cost as it corresponds to the requirements of industrial utility.

In general, the reactor is in nuclear power plants in which gas-cooled high-temperature reactors are provided a pressure vessel enclosed through which a cooling gas, such as e.g. helium or carbon dioxide, is circulated so that it dissipates the thermal energy released by the reactor. The steam for the operation of the turbines is normally by heat transfer from the coolant to the fluid of a water / Steam system received. Conventionally, this heat transfer is carried out in a steam generator in which of Thermal energy dissipated from the reactor is used to generate superheated steam.

In such a system of gas-cooled reactor and steam generator, it is often desirable that gas only in one single pass through the steam generator before it is returned to the reactor. It is therefore important that the greatest possible amount of heat from the Gas is discharged so that maximum performance or maximum efficiency is achieved. However, it is It is also important that the gas flow is only subjected to the least possible restriction so that the work required for the Transporting the gas through the system must be kept to a minimum. In those cases where the steam generator in the same pressure vessel for a variety of reasons, including the reason of structural economy how the reactor itself is housed, it is also important that the dimensions of the steam generator be minimized are and that the steam generator or portions thereof through necessarily restricted openings in the container containing it is easily removable and replaceable

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or are. After all, it's for structural reasons Economics and the efficiency of the system necessary that the vapor pressure exceeds the pressure of the primary coolant, To limit the pressure build-up in the primary coolant in the In the event of a fault or break at the boundary between steam and primary coolant, large steam pipes end in or at the Wall of the reactor vessel, and these large steam pipes are connected via pipelines with heat exchanger bundles, with it the amount of leakage is limited or minimized.

. When the steam generator is housed in a special cavity inside a prestressed concrete reactor vessel is, the course of unheated pipelines leads from pipe connections to or in the wall of the reactor vessel to the ends of the tube bundles results in wasteful use of both "piping and volume" of the reactor vessel cavity. Accordingly, systems have been developed where crossover pipe connections between the low temperature and high temperature sections and the reheating sections as described above were used at their ends opposite the Steam / water pipe connections, so that in this way the general direction of water / steam flow was reversed and the lengths of unheated pipelines have been minimized.

A difficulty in designing steam generators of the type described consists in the fact that pipes in it of different Configurations and lengths often have different thermal expansion properties. Crossover Connections between pipes of different types must therefore allow a certain degree of thermal expansion. Around To make this possible, prior art designs have often been complicated and intertwined Requires arrangements of unheated pipe sections so that

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.in this way steam generator and reheater sections were connected in a large facility. This can be achieved by arranging thermal expansion devices at the crossings Complicated intertwining or intertwining eliminated and manufacturing timescales can become noticeable be reduced.

The shipping requirements may include the dimensions of a steam generator produced in a location that is remote from where it is to be installed. Lots of steam generator systems prior art therefore require a high level of on-site fabrication in an on-site facility Assembly, which increases their manufacturing times, especially when complex and intertwined Arrangement of pipes are applied. By arranging thermal expansion devices at the crossings for the purpose of completely eliminating the interweaving and achieving separate steam generator and reheater sections production at the construction site is minimized and shipping is made easier.

As a result, the invention is intended to provide an improved steam generator.

Furthermore, an improved steam generator is to be created with the invention, which is particularly suitable for use in a substantially cylindrical cavity in a pressure vessel.

In addition, the invention is intended to propose a steam generator that facilitates shipping and the production can be separated into parts.

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Finally, the invention provides a steam generator created in which the length of the pipelines running in unheated Sections and expansion zones used is minimized.

. To achieve this, internal Crossovers applied between sections of the steam generator and the reheater.

Further advantages and features of the invention will be explained below with reference to an in FIGS. 1 to 4 of the drawing Principle illustrated, particularly preferred exemplary embodiment explained in more detail; show it:

1 is a perspective view illustrating a steam generator constructed in accordance with the invention is with parts broken away;

FIG. 2 shows a view through the lower end of the steam generator along the section lines H-II in FIG. 3>

Fig. 3 is a plan view of the reheater section of the Steam generator, along the section line IH-III of Fig. 2; and

4 is a schematic diagram showing the general layout and coolant flow of the steam generator Fig. 1 illustrated

In very general terms, the steam generator according to the invention comprises a high temperature section 11 which is a plurality of elongated, substantially straight tubes 12 which are arranged parallel to one another so that they form an elongated tube bundle. An unheated feed water expansion pipe section 13 is provided with a low or Low temperature section of heated tubes 14 connected, which are substantially spiral-shaped and one annular Form tube bundle which is arranged coaxially to the high-temperature section. The axial dimension of the low temperature section is essentially smaller than that of the

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High-temperature section, and the low-temperature section is arranged toward one end of the high-temperature section, so that an annular space 15 is formed.

Reheater sections 16 and 17 are in the annular Space 15 arranged, each reheater section having a plurality of elongated, substantially straight Has tubes 18 which are arranged parallel to each other, so that they form an elongated tube bundle, the axial Length is substantially smaller than that of the high temperature section. The axes of the reheater sections 16 and 17 are aligned essentially parallel to one another and to the axes of the high-temperature section 11.

In operation, heated fluid is first applied across the tubes of the reheater sections 16 and 16 steered, then along the tubes of the high temperature section towards one end of the same, and finally over the spiral tubes of the low temperature section 14 in a direction parallel to the axis of the high temperature section and away from one end of that section.

Reference is now made in more detail to the figures of the drawing, in which part of a nuclear reactor system, constructed in accordance with the invention is shown. The nuclear reactor system has a prestressed Concrete pressure vessel 27, by a suitable device, which is not shown, within an associated Structure, which is also not shown, is carried or held. Prestressing tendons 29 extend axially through the concrete of the pressure vessel 27 which is generally cylindrical in shape. A plurality of annular recesses 31 is formed in the outer surface of the pressure vessel and serves to create circumferentially extending, take up bias tapes, not shown.

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The interior of the pressure vessel 27 comprises a main chamber 33 * in which a reactor core (not shown) is held will. The chamber 33 is provided with a liner 35 of suitable metal which is anchored to the concrete. Of the The core of the reactor is of the so-called gas-cooled type. There are appropriate Provisions for circulating a cooling gas, such as helium or carbon dioxide, over the not shown Reactor core hit, so that the temperature of the gas is increased. The gas is then passed through one or more heat exchangers or steam generators for the purpose of generating "water vapor." or other vapors for the operation of an electricity generating machine installation circulated. The recirculated gas is then returned to the core where it is reheated.

In the illustrated reactor system, the main chamber 33 is spaced from a plurality of circumferentially arranged chambers 37 surrounded, only one of these chambers is shown in the figures of the drawing. Each chamber 37 has a cylindrical shape and extends vertically within the reactor vessel with its axis parallel to the axis of the reactor vessel runs. A steam generator and a coolant circulator are provided in each of the chambers 37, as indicated at 39 in the drawing.

Coolant gas is supplied from the main chamber 33 to the chamber 37 through a horizontal conduit 43. The coolant is for the purpose of renewed circulation over or through the reactor core by a similar or similar horizontal Line, which is partially shown in Fig. 1 at 45, returned to the chamber 33. At the lower ends of the chambers Suitable closures (not shown) are provided for 33 and 37.

The chamber 37 is accessible from the lower end of the pressure vessel 27 through penetrations 47, as is best can be seen from FIG. Each penetration 47 is with one

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Metal liner 49 extending upwardly and attached to a metal liner 51 for chamber 37 is welded on. Each penetration 47 is by means of a concrete plug 53, which has an inner metal lining 55, closed and sealed. In the plug 53 are suitable penetrations for the entry of various water and steam lines, as will be explained below, are provided in the chamber 37, and these lines serve to convey water and to direct steam to the steam generator 39 and to remove it from this steam generator.

The reheater bundles or sections 16 and 17 of the tubes 18 are arranged towards the lower end of the chamber 37 and are supported by a suitable frame or a suitable frame of metal plates or the like (not shown) held. Above the reheater tube bundle is the Feedwater expansion pipe section 13 and above is the low temperature coiled coil pipe section 14 having a arranged annular shape. The section 14 is provided with a housing 59. The bundle 14 includes the economizer or feed water preheater, the evaporator and the initial Superheater sections of the steam generator.

The high temperature section or tube bundle 11, which comprises a plurality of elongated, straight tubes 12, is arranged in the space which is delimited by the annular tube bundle 14. A housing 61 surrounds the tube bundle 11. The housings 59 and 61 are held by a mounting flange 65 which is attached to the prestressed concrete container 27 is attached and extends into the chamber 37.

The annular space between the lower end of the housing 59 and the surrounding chamber lining 51 is blocked or locked by means of the annular fastening flange 65.

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Post-heating fluid is fed into the post-heating tube bundles 16 and 17 and discharged therefrom, namely through manifolds or pipe jackets 67. The reheating tubes of the hot and cold reheating tube sections are through hairpin-shaped crossover tubes, which are indicated generally at 69, connected to one another.

Feed water for the steam generator is supplied through feed water inlet pipes 71, which run upward through the space 15 and are connected to the tubes 14. A manifold or pipe jacket 73 connects the feed water to the pipes 71 · The outflow at the top of the bundle 14 goes zum.oberen end of the tube bundle 11 through crossover tubes 75, which are flexible to accommodate differences in thermal expansion between tube bundles 11 and 14. At the lower end of the tube bundle 11, superheated steam passes through an overheating manifold or an overheating tube jacket 77 off.

The incoming hot gas from the reactor core passes through line 43 into chamber 37. The hot gas is sent across the tubes 18 in the bundles 16 and 17, through jackets 78 (Fig. 3) · The gas is then towards the lower end of the space 15, and thereafter through the housing 61 along the tubes of the tube bundle 11 upwards. An inverted, cup-shaped gas flow baffle plate 79 is above the top of the housing 61 and forms part of the housing 59. The gas flows through the space between the upper open end of the housing 61 and the plate 79 therethrough and is then directed downwardly over the spiral tubes in tube bundle 14. After the gas over the spiral Tubes in the tube bundle 14 has flowed, it passes through passages 81 in the outer wall of the housing 59 and flows between the housing 59 and. the wall or the

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fit

clothing 51 of the chamber 37 upwards to the upper transverse line 45 after it has passed through the coolant circulator (not shown) has passed through.

In a practical embodiment of a gas cooled reactor system, each of the steam generators with integral reheaters of the type illustrated can be sized, for example, to have a heat capacity in the nominal range of '500 MW'. The steam generators can supply main steam and reheating steam to a conventional 165 bar / 510 C / 538 C reheater turbine generator set. The core coolant can be kept at a pressure of about 48 bar at full power conditions. Each primary coolant loop, which includes a steam generator with its associated helium circulator, can provide a pressure gradient sufficient to overcome the total pressure losses in the primary loop of about 1380 mbar, with from these losses 450 mbar are available to the steam generator under full load operating conditions. The steam generator according to the invention is therefore easily adaptable to considerations of optimization for the overall system, including such optimization conditions which include the dimensions of the pressure vessel and the containment building. Also, the steam generator can easily be assembled into units in the shop, which units can be shipped, either by barge or rail, in accordance with restrictions on the overall envelope line of the steam generator units.

To make shipping easier and to shorten production times, the steam generator can be installed after the Invention can easily be divided into two main sub-plants, namely in the main steam section and the overall reheater section. The U-tube reheater sections in combination with the spiral coiled economizer or feed water preheater, evaporator, preheater and

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the straight pipe end superheater are in accordance with
kept the requirements for a compact structure, and
they meet the requirements for minimizing the
unheated pipe surface to the greatest possible extent.

The crossover tubes 69 from the cold to the
are called legs of the reheater sections as well as the
Crossover tubes 75 are arranged internally within the active gas flow path and in this way absorb the necessary different thermal expansion between these two heating surface sections.

In particular, the generator according to the invention can be constructed with a casing which has a diameter of
4077 mm and a height of 18 644 mm. Since the steam and
Water lines are routed to the bottom of the pressure vessel and connections to the lower end of the steam generator are made through penetrations in the reactor vessel, the gas circulators can fill the entire pressure generator cavity above the generator.

The high pressure pipe jackets, the economizer inlet and
the superheater outlet can be fitted with integral damming / flow restricting cylinders that prevent consequential ruptures and excessive leakage of water into the primary
Prevent coolant in the event of a break in the steam or water pipes connected to the pipe jacket inside the pressure vessel.

When the main steam pipes 12 and 14 are essentially
are of the same length, they are always the same on the steam side
Flow distribution and corresponding uniform steam outlet temperatures ensured. This arrangement requires
Longitudinal tube spacing variations between individual rows of tubes of the spiral tube coils while maintaining a uniform height for all tube spirals. Of the

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Cross tube spacing is kept constant. The straight pipe end superheater 11 is arranged in a straight countercurrent to the coolant gas so that there is an equal flow of helium around each pipe, resulting in an irregular, circular pipe pattern.

To increase the operational stability, a pressure in the main steam section can be maintained during all boiling conditions which is close to full operating pressure. In order to meet the above requirements, the main steam section a portion of reduced diameter inlet piping between the feedwater pipe jacket and the economizer inlet exhibit. It can also include an enlarged diameter straight tube final superheater so as to be the ratio of inlet-to-outlet vapor pressure is obtained, as is necessary for the boiling stability.

Rotating blades, not shown, can be found on the reheater inlet and on the top of the steam generator be provided so that in this way a good gas distribution over the two reheater legs and at the inlet to the main spiral coil tube bundles will.

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Claims (11)

Claims ι 1 · '' steam generator, characterized by a high temperature section (11) which has a plurality of substantially straight tubes (12) which are parallel to each other and form an elongated tube bundle; a low temperature section (14) having a plurality of substantially helical tubes forming an annular tube bundle, which is arranged coaxially with the high temperature section (11), the low temperature section having an axial dimension which is substantially lower than that of the high temperature section, and wherein the low temperature section is arranged after one end of the high temperature section; a plurality of reheater sections (16, 17) each of which has a plurality of elongated, substantially straight tubes (18) parallel to one another and form an elongated tube bundle with an axial length substantially less than that of the high temperature section (11), the axes of the reheater sections being substantially parallel to each other and to the Axis of the high temperature section are aligned, and further wherein the reheater sections to the other end of the high-temperature section opposite to its mentioned one end towards which it is to be arranged the low temperature section is seconded; and a facility (78,61,59) for directing heating fluid initially across the tubes of the reheater sections (16,17), then along the tubes (12) of the high-temperature section (11) towards one end of the same, then over the spiral tubes of the low temperature section in a direction parallel to the axis of the high temperature section and runs away from one end of it. 2. Steam generator according to claim 1, characterized by an outlet line device (61) for the high temperature 709815/0329 cut (11) extending axially from the other end of the high temperature section, which is opposite to one end, and which extends parallel to at least part of the Reheater sections (16,17); and inlet conduit means (59) for the low temperature section (14) which parallel to the axis of the low-temperature section the other end of the high temperature section which is opposite to the one end and which is parallel to at least part of the reheater sections runs. 3. Steam generator according to claim 1 or 2, characterized by coaxial inlet and outlet line devices (78) for the reheater sections (16,17) extending axially from the same extends on the sides thereof and opposite the sides or opposite from the sides, namely after one end of the high-temperature section (11). 4. Steam generator according to claim 1, 2 or 3, characterized by a crossover device (75) for connecting the substantially straight tubes (12) of the high temperature section (11) and the substantially spiral tubes of the low-temperature section (12), this crossover device internally within the heating fluid flow path is arranged. 5. Steam generator according to one of claims 1 to 4, characterized by an additional crossover device (69) for connecting the essentially straight tubes (18) in one of the reheater sections (16) with essentially straight tubes Pipes (18) in the other reheater section (17), the additional crossover device internally within the flow path of the heating fluid is arranged. 6. Steam generator, in particular according to one of the claims 1 to 5, characterized in that it is in an essentially 70981S / 0329 264419b union cylindrical cavity (37) in a pressure vessel (27) and comprising: a high temperature section (11) having a plurality of elongated, im substantially straight tubes (12) which are parallel to one another and form an elongated tube bundle and substantially lie or are arranged along the axis of the cylindrical cavity (37); a low temperature section (14), having a plurality of substantially helical tubes that form an annular tube bundle that is coaxial to the high temperature section (11) is arranged, wherein the low temperature section has an axial dimension that is substantially is smaller than that of the high temperature section, and wherein the low temperature section is further after one end of the high temperature section is arranged to and an annulus (15) at the other end of the high temperature section leaves free, which is opposite to the one end, this annular space between the high temperature section and extending the wall of the cylindrical cavity (37); a plurality of reheater sections (16, 17), located in the annulus (15) with each of the reheater sections having separate inlet and outlet conduit means (67) has; and means (78,61,59) for directing heating fluid first transversely over the tubes of the reheater sections (16, 17), then along the tubes (12) of the high-temperature section (11) to the one End of the same to, then over the spiral tubes of the low temperature section (14) in a direction that is parallel is directed to the axis of the high temperature section and away from one end thereof. 7. Steam generator according to claim 6, characterized by an outlet conduit means (77) for the high temperature section, extending axially from the other end of the high temperature section (11) opposite to the one End lies, and which is parallel to at least part of the reheater sections (16,17). 709815/0329 8. Steam generator nach'Anspruch 6 or 7, characterized through inlet conduit means (59) for the low temperature section (14), which is parallel to the axis of the high-temperature section (11) as well as to the other end of the high-temperature section, which is opposite to the one end lies, extends. 9. Steam generator according to claim 6, 7 or 8, characterized in that that each reheater section (16,17) is of substantially cylindrical shape, the axis of which is parallel to Axis of the cylindrical cavity (37) is aligned. 10. Steam generator according to one of claims 6 to 9, characterized by a crossover device (75) to Connecting the substantially straight tubes (12) of the high-temperature section (11) and the substantially spiral-shaped Pipes of the low temperature section (14), this crossover device internally within the flow path of the heating fluid is arranged. 11. Steam generator according to one of claims 6 to 10, characterized by an additional crossover device (69) for connecting adjacent reheating sections (16, 17), with this additional crossover device internally is located within the flow path of the heating fluid