CN114914002A - Passive heat export system of direct current steam generator - Google Patents

Abstract

The invention relates to a passive heat exporting system of a once-through steam generator, which comprises a condenser arranged in an air cooling tower, wherein the first end of the condenser penetrates through the air cooling tower and is connected to a steam outlet of the steam generator through a steam pipeline, and the second end of the condenser penetrates through the air cooling tower and is connected to a water inlet of the steam generator through a water supplementing pipeline; the water replenishing pipeline is provided with a water replenishing tank, and the second end of the condenser is connected into the water replenishing pipeline and communicated with the water replenishing tank. The invention adopts air cooling and passive design to continuously derive the heat of the circuit after an accident; the problem that an active waste heat discharging system is complex in design and multiple in supporting systems is solved, the required supporting systems are reduced, the problem that a large water tank needs to be arranged at a high position outside a containment of a secondary side passive waste heat discharging system adopting a water cooling scheme is solved, the problem of water replenishing after an accident is solved, the large water tank does not need to be arranged at the high position outside the containment, and the requirement of water replenishing in a long-term stage after the accident is effectively reduced or eliminated.

Description

Passive heat exporting system of once-through steam generator

Technical Field

The invention relates to the field of nuclear power plant equipment safety, in particular to a passive heat exporting system of a direct current steam generator.

Background

During normal operation, heat generated by the core is carried away by the steam generator. When accidents such as water supply pipeline breakage or steam pipeline breakage happen, a waste heat leading-out device is needed to continuously lead out heat of a loop.

For a traditional nuclear power plant adopting an inverted U-shaped steam generator, an active waste heat discharge system is generally adopted, or a secondary side passive waste heat discharge system adopting a water cooling scheme is adopted. For an active waste heat discharge system, in order to meet the requirement of heat conduction after an accident, a series of support systems such as an emergency diesel engine and the like need to be configured. For the secondary side passive waste heat removal system of the water cooling scheme, the condenser is immersed in the condensate water tank, and when the heat of the primary loop passes through the steam generator to heat the water of the secondary loop, a large amount of steam is generated by the secondary loop and enters the condenser under the action of natural circulation driving force to transfer the heat to the water in the water tank. The water tank volume is often very big, and the evaporation of absorbing heat through the water in the water tank is finally leading-in to final heat trap atmosphere with a return circuit heat to satisfy the demand that the heat was continuously derived after the accident. In order to meet the requirement of natural circulation, a large water tank is usually required to be arranged at a higher position outside a containment, and great challenges are provided for arrangement and support of the water tank; meanwhile, when water in the large water tank is gradually evaporated, the water tank is also required to be supplemented with water through a water supplementing pipeline.

Moreover, when the secondary side passive residual heat removal system is only relied on, in order to meet the requirement of heat removal of a primary circuit, a larger condenser capacity is needed.

For the design of a nuclear power plant adopting a direct-flow steam generator, when a passive waste heat discharge system is adopted as a means for guiding out waste heat, the volume of the two loops is smaller, the heat exchange capacity of the steam generator is far higher than that of a condenser of the passive waste heat discharge system, and after the passive waste heat discharge system is started, the pressure and the temperature of the two loops are continuously increased. In order to prevent the pressure of the two loops from rising to exceed the design pressure, the design pressure of the two loops needs to be at least increased to the saturation pressure corresponding to the highest temperature of the primary loop in the transient process, or the heat exchange capacity of the passive waste heat discharging system is improved.

Disclosure of Invention

The invention aims to solve the technical problem of providing a direct current steam generator passive heat exporting system which is convenient in design, safe and reliable, aiming at least one defect of the prior art.

The technical scheme adopted by the invention for solving the technical problems is as follows: constructing a direct-flow steam generator passive heat exporting system, comprising a condenser arranged in an air cooling tower, wherein a first end of the condenser penetrates through the air cooling tower and is connected to a steam outlet of a steam generator through a steam pipeline, and a second end of the condenser penetrates through the air cooling tower and is connected to a water inlet of the steam generator through a water supplementing pipeline; and a water replenishing tank is arranged on the water replenishing pipeline, and the second end of the condenser is connected into the water replenishing pipeline and communicated with the water replenishing tank.

Preferably, the water inlet end of the water replenishing tank is connected with the second end of the condenser, and a check valve for preventing water in the two loops from flowing backwards is arranged between the water outlet end of the water replenishing tank and the water inlet of the steam generator.

Preferably, the steam pipeline comprises a first steam pipeline and a second steam pipeline which are communicated with each other;

the steam outlet of the steam generator is connected to a steam turbine of a nuclear power plant through the first steam pipeline, and the first end of the condenser is connected to the first steam pipeline through the second steam pipeline.

Preferably, one end of the first steam pipeline, which is far away from the steam outlet of the steam generator, is provided with a first isolation valve.

Preferably, one end of the second steam pipeline, which is far away from the condenser, is provided with a second isolation valve.

Preferably, the once-through steam generator passive heat deriving system further comprises at least one set of steam release modules, and the steam release modules are arranged on the first steam pipeline.

Preferably, the steam release module comprises a steam release pipe and a steam release regulating valve arranged on the steam release pipe.

Preferably, the steam release module further comprises a steam release isolation valve disposed on the steam release conduit and between the steam release regulating valve and the first steam conduit.

Preferably, the steam release module further comprises a silencer disposed on an end of the steam release pipe remote from the steam release regulating valve.

Preferably, a third isolation valve is arranged between the check valve and a water inlet of the steam generator.

The implementation of the invention has the following beneficial effects: the invention adopts air cooling and passive design to continuously lead out the heat of the circuit after an accident; the problems that the active waste heat discharging system is complex in design and multiple in support systems are solved, and the support systems required by design are effectively reduced; meanwhile, the problem that a secondary side passive waste heat discharging system adopting a water cooling scheme needs to be provided with a large water tank at a high position outside a containment vessel and the problem of water supplement after an accident are solved, the large water tank does not need to be arranged at the high position outside the containment vessel, and the requirement of water supplement at a long-term stage after the accident is effectively reduced or eliminated.

Drawings

The invention will be further described with reference to the following drawings and examples, in which:

FIG. 1 is a schematic diagram of the DC steam generator passive heat removal system of the present invention;

fig. 2 is a schematic structural diagram of another embodiment of the present invention.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, it is to be understood that the orientations and positional relationships indicated by "front", "rear", "upper", "lower", "left", "right", "longitudinal", "lateral", "vertical", "horizontal", "top", "bottom", "inner", "outer", "leading", "trailing", and the like are configured and operated in specific orientations based on the orientations and positional relationships shown in the drawings, and are only for convenience of describing the present invention, and do not indicate that the device or element referred to must have a specific orientation, and thus, are not to be construed as limiting the present invention.

It should also be noted that, unless expressly specified or limited otherwise, the terms "mounted," "connected," "secured," "disposed," and the like are to be construed broadly and encompass, for example, fixed connections as well as removable connections or integral parts; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. When an element is referred to as being "on" or "under" another element, it can be "directly" or "indirectly" on the other element or intervening elements may also be present. The terms "first", "second", "third", etc. are only for convenience in describing the present technical solution, and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated, whereby the features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

It should be noted that, in the embodiment of the present invention, the first end of the condenser 2 refers to an end near the upper side of the air cooling tower 1 in fig. 1, and the second end of the condenser 2 refers to an end near the lower side of the air cooling tower 1 in fig. 1.

As shown in fig. 1, the invention constructs a direct current steam generator passive heat export system, which comprises a condenser 2 arranged in an air cooling tower 1, wherein the condenser 2 is used for exporting waste heat during the whole accident; a first end of the condenser 2 penetrates through the side wall of the air cooling tower 1 and is connected to a steam outlet 31 of the steam generator 3 through a steam pipeline 100, and a second end of the condenser 2 penetrates through the bottom of the air cooling tower 1 and is connected to a water inlet 32 of the steam generator 3 through a water replenishing pipeline 200; the water replenishing pipeline 200 is provided with a water replenishing tank 4, and the water replenishing tank 4 is used for maintaining the minimum water quantity required by the natural circulation of the two loops; the second end of the condenser 2 is connected to the water replenishing pipeline 200 and is communicated with the water replenishing tank 4. In some embodiments, multiple condensers 2 are arranged in one air cooling tower 1 to achieve good waste heat removal effect.

Further, the water inlet end of the water replenishing tank 4 is connected with the second end of the condenser 2 to receive water obtained by condensing steam through the condenser 2; a check valve 5 for preventing the water of the two circuits from flowing backwards is arranged between the water outlet end of the water supplementing tank 4 and the water inlet 32 of the steam generator 3.

Further, the steam pipe 100 includes a first steam pipe 101 and a second steam pipe 102 which are communicated with each other; the steam outlet 31 of the steam generator 3 is connected to the nuclear power plant steam turbine 300 through a first steam pipeline 101, and the first end of the condenser 2 is connected to the first steam pipeline 101 through a second steam pipeline 102;

further, a first isolation valve 6 is arranged at one end of the first steam pipe 101 away from the steam outlet 31 of the steam generator 3, and the first isolation valve 6 is also called a main steam isolation valve and is used for main steam isolation.

Further, a second isolation valve 7 is arranged at one end, away from the condenser 2, of the second steam pipeline 102, which is connected with the first steam pipeline 101; and a third isolating valve 8 is arranged between the check valve 5 and the water inlet 32 of the steam generator 3. In normal operation the second 7 and third 8 isolation valves are isolated from the steam generator 3 and open when required. In the flow direction of steam and water, the inlet and outlet are for passive heat removal systems, the inlet corresponding to flow to the condenser 2 and the outlet corresponding to flow out of the condenser 2, so the second isolation valve 7 can be referred to as an inlet isolation valve and the third isolation valve 8 can be referred to as an outlet isolation valve.

As shown in fig. 2, further, the once-through steam generator passive heat deriving system further includes at least one set of steam releasing modules 9, and the steam releasing modules 9 are disposed on the first steam pipe 101. Specifically, the steam release module 9 is disposed on the bypass between the first isolation valve 6 and the second isolation valve 7, and it is understood that the steam release module 9 may be additionally provided according to actual conditions. When an accident that waste heat needs to be led out occurs, in the short and medium stages of the accident, the steam release module 9 is used for leading out partial waste heat, the waste heat of the reactor core is taken away in a mode of combining the steam release module 9 and the condenser 2, and the pressure of the two loops is prevented from exceeding the design pressure; in the long-term phases of the accident, the steam release module 9 is taken out of operation as the demand for heat removal decreases.

Further, the steam releasing module 9 comprises a steam releasing pipe 90 and a steam releasing regulating valve 91 arranged on the steam releasing pipe 90, the steam releasing regulating valve 91 is used for regulating the flow of the direct current steam generator passive heat exporting system of the present invention, when the pressure of the steam generator 3 is relatively high, the opening of the steam releasing regulating valve 91 is increased, and accordingly the flow is also increased; when the pressure of the steam generator 3 is low, the steam release adjustment valve 91 is also adjusted to be small accordingly, and is maintained at a certain opening degree when the isolation valve is closed. Further, the steam release module 9 further comprises a steam release isolation valve 92 disposed on the steam release pipe 90 and located between the steam release regulating valve 91 and the first steam pipe 101, and the steam release isolation valve 92 is used for isolating the steam release module 9 from the steam generator 3 during normal operation and automatically opens when conditions are met. Further, the steam release module 9 further includes a silencer 93 provided on an end of the steam release pipe 90 remote from the steam release adjustment valve 91 for preventing noise.

Specifically, in the present embodiment, the steam outlet 31 of the steam generator 3 passes through a first steam pipeline 101 and connects the first isolation valve 6 to the nuclear power plant steam turbine 300, and two branches are provided on the first steam pipeline 101, wherein one branch is connected to the steam release module 9; the other branch is connected with a second isolation valve 7 and is sequentially connected with the condenser 2, the water replenishing tank 4, the check valve 5 and a third isolation valve 8 to the water inlet 32 of the steam generator 3 through a second steam pipeline 102.

The specific application of the invention is illustrated as follows:

(1) and when the engine runs normally;

when the unit is in normal operation and no accident occurs, the heat generated by the core is taken away by the feed water-steam of the steam generator 3. At the moment, the passive heat exporting system is in a standby state, the inlet isolating valve and the outlet isolating valve are closed, and the water level in the water replenishing tank 4 is maintained at a rated water level; the steam release isolation valve 92 is in a closed state.

(2) When an accident occurs;

a. a short-term and medium-term post-accident stage;

when an accident occurs and heat generated by the reactor core cannot be taken away through the feed water-steam of the steam generator 3, the heat of the primary loop cannot be effectively led out, the reactor is triggered to stop through the state parameters of the primary loop and the secondary loop, then the steam turbine 300 trips, and the pressure of the secondary loop begins to rise at the moment.

When the pressure of the secondary loop rises to the starting setting value of the steam release module 9, the steam release isolation valve 92 is opened to prevent the pressure of the secondary loop from exceeding the design pressure, and the steam release module 9 can meet the requirement of the overpressure protection of the secondary loop.

The system automatically opens the inlet isolation valve and the outlet isolation valve based on the associated protection signal. In order to prevent the phenomenon of air hammer after the valve is opened, a design scheme that an inlet isolating valve is opened firstly and an outlet isolating valve is opened after a certain time delay is adopted in the design, and meanwhile, the inlet isolating valve and the outlet isolating valve adopt slow-opening valves meeting the opening time requirement.

Under the action of gravity, water in the water replenishing tank 4 enters the steam generator 3, and steam is generated after heat of the primary loop is absorbed. The steam produced is partly discharged directly to the environment via the steam release module 9, and the remaining steam is passed via the second steam line 102 into the condenser 2, condensed in the condenser 2 and subsequently into the make-up water tank 4. The capacity of the condenser 2 should be sufficient to continuously dissipate the heat of the primary circuit. The water content in the water replenishing tank 4 can meet the requirement of establishing natural circulation after the passive residual heat removal system is put into operation under the condition that the steam release module 9 is started. Air enters the air cooling tower 1 from the bottom of the air cooling tower 1, absorbs heat and flows upwards, and then enters the environment. In this case, the heat of the primary circuit is taken away by the combination of the discharge of steam by the steam release module 9 and the condenser 2, while the pressure of the secondary circuit can be prevented from exceeding the design pressure.

b. A post-accident long-term stage;

as heat is further removed, the pressure in the two circuits begins to drop gradually. When the two-circuit pressure is lower than the closing pressure of the steam release module 9, the steam release isolation valve 92 closes. At this time, the heat of the primary circuit is continuously taken away by the condenser 2.

For designs with multiple steam generators, several of the rows of passive heat removal systems can be isolated as needed during the long term post-accident phase.

After an accident, the heat of a loop can be continuously and effectively led out by reasonably designing the discharge capacity of the steam release module and the heat exchange capacity of the condenser, the reliability of the system in operation after the accident is ensured, and the safety and the economy of the nuclear power station are improved.

The invention adopts air cooling and passive design, meets the heat output requirement, reduces the dependence on a support system and reduces the support system required by the system compared with an active waste heat discharge system; a large water tank does not need to be arranged at a high position outside the containment, so that the requirement of water supplement in a long-term stage after an accident is effectively reduced or eliminated; and through the mode that steam release system and condenser combine, can prevent that two return circuit pressure from surpassing design pressure, reduced the heat transfer area of single-row condenser and the capacity requirement of condenser, be favorable to the miniaturization of design.

It is to be understood that the foregoing examples, while indicating the preferred embodiments of the invention, are given by way of illustration and description, and are not to be construed as limiting the scope of the invention; it should be noted that, for those skilled in the art, the above technical features can be freely combined, and several changes and modifications can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention; therefore, all equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims (10)

1. The direct-current steam generator passive heat exporting system is characterized by comprising a condenser (2) arranged in an air cooling tower (1), wherein a first end of the condenser (2) penetrates through the air cooling tower (1) and is connected to a steam outlet (31) of a steam generator (3) through a steam pipeline (100), and a second end of the condenser (2) penetrates through the air cooling tower (1) and is connected to a water inlet (32) of the steam generator (3) through a water supplementing pipeline (200); be provided with moisturizing case (4) on moisturizing pipeline (200), condenser (2) second end access moisturizing pipeline (200) and with moisturizing case (4) intercommunication.

2. The direct current steam generator passive heat removal system of claim 1, wherein the water inlet end of the water supply tank (4) is connected to the second end of the condenser (2), and a check valve (5) for preventing the water in the two circuits from flowing backwards is disposed between the water outlet end of the water supply tank (4) and the water inlet (32) of the steam generator (3).

3. The once-through steam generator passive heat removal system according to claim 1, wherein the steam conduit (100) comprises a first steam conduit (101) and a second steam conduit (102) in communication;

the steam outlet (31) of the steam generator (3) is connected to a nuclear power plant steam turbine (300) through the first steam pipeline (101), and the first end of the condenser (2) is connected to the first steam pipeline (101) through the second steam pipeline (102).

4. The once-through steam generator passive heat removal system according to claim 3, characterized in that the end of the first steam conduit (101) remote from the steam outlet (31) of the steam generator (3) is provided with a first isolation valve (6).

5. The once-through steam generator passive heat removal system according to claim 3, characterized in that the end of the second steam conduit (102) remote from the condenser (2) is provided with a second isolation valve (7).

6. The once-through steam generator passive heat removal system according to claim 3, further comprising at least one set of steam release modules (9), the steam release modules (9) being arranged on the first steam pipe (101).

7. The once-through steam generator passive heat removal system according to claim 6, characterized in that the steam release module (9) comprises a steam release conduit (90) and a steam release regulating valve (91) arranged on the steam release conduit (90).

8. The once-through steam generator passive heat removal system according to claim 7, characterized in that the steam release module (9) further comprises a steam release isolation valve (92) disposed on the steam release conduit (90) and between the steam release regulating valve (91) and the first steam conduit (101).

9. The once-through steam generator passive heat removal system according to claim 8, characterized in that the steam release module (9) further comprises a silencer (93) disposed on an end of the steam release conduit (90) remote from the steam release regulating valve (91).

10. The once-through steam generator passive heat removal system according to claim 2, characterized in that a third isolation valve (8) is provided between the non-return valve (5) and the water inlet (32) of the steam generator (3).

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