JP2000199797A - Steam separator for bwr - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress lowering of reactor pressure during a transition by extending tubing from a drain opening to a reactor liquid surface in a second stage, and constituting a flow passage in which drain does not come directly into contact with a steam dome. SOLUTION: When a transition phenomenon in which a reactor closing a main steam tube and a condensate tube scrams occurs, the steam separator 8 introduces rising gas-liquid two-phase flow into a cylinder after heating, and a swirl flow is given by a wing or the like. Thereby centrifugal force is produced, the liquid phase of large density is collected on the outer peripheral part of a swirl drum 102, separated from steam flowing in the center part in a pick-off ring 103, and drained through the drain passage 104 of the liquid phase and a drain outlet 105. Then, tubing 201 is extended to a reactor liquid surface from the drain outlet 105 in the second stage 102, drainage of subcooled water flowing therein is not directly heat-exchanged with the steam of a steam dome, and a heat transfer area is also markedly reduced. Thus, the lowering width of reactor pressure is also lessened, and pressure lowering is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam-water separator for a system for heating a liquid to generate steam, such as a nuclear reactor, and utilizing the steam for power generation and the like. The present invention relates to a BWR steam / water separator having an improved discharge channel for separated liquid.

[0002]

2. Description of the Related Art FIG. 5 is a longitudinal sectional view of a boiling water reactor (BWR) according to the prior art. Feed water flows from a feed water inlet 2 of the reactor pressure vessel 1, passes through a downcomer 3, and flows through an internal pump 4 to a reactor core 5. The water heated in the reactor core 5 passes through a standpipe 7 above the shroud head 6 and is separated into steam and water by a steam separator 8 and a steam dryer 9. And water flows to downcomer 3.

FIG. 6 is a longitudinal sectional view of a conventional steam separator. As described in JP-A-5-346483, a conventional steam-water separator has a structure in which after heating, a rising gas-liquid two-phase flow is guided into a cylinder and a swirling flow is provided by a spiral blade 101 or the like. Was. In this way, a centrifugal force is generated by the swirling flow, and a liquid phase having a high density is collected on the outer peripheral portion of the cylindrical revolving drum 102, and is separated from the vapor flowing through the central portion by the pickoff ring 103.

[0004] The liquid phase collected on the outer periphery of the revolving drum descends through a liquid discharge passage 104 provided on the outer periphery of the revolving drum, and is led to a recirculating liquid phase through an outlet 105 to a heating unit. It is discharged inside. As shown in FIG. 6, the steam separator 8 comprises three stages, a first stage, a second stage,
Called the third stage, three discharge ports 105 are also provided. The outlet 105 of the second stage was in direct contact with the steam in the steam dome.

[0005] The present invention is directed to a steam-water separator in the event of a transient event in which the reactor with its main steam pipe and water supply pipe closed is scrammed. FIG. 4 shows a phenomenon model according to the prior art.
In the prior art steam-water separator, unlike the saturated gas-liquid two-phase flow at the time of rated operation, the subcooled water single-phase flow flows in the transient state. The reactor water level also drops by about 1 m from the normal water level during the transient operation during the transient operation. The subcooled water that has flowed into the steam separator turns and is discharged in a spray form from the outlet 105 of the second stage.

[0006] The steam of the steam dome containing the steam separator 8 exchanges heat with the spray-shaped subcooled water in a region A surrounded by a dotted line, and condenses. As a result, the steam dome (reactor) pressure decreases. Another cause of the pressure drop is a phenomenon in which steam is drawn into a region B surrounded by a dotted line below the surface of the subcooled water due to drainage from the outlet 105 of the first stage (carry under), and the steam is condensed. . Due to the two phenomena of condensation heat exchange, the reactor pressure drops from the rated operating pressure of 70 atm to about 10 atm,
As a result, there is a disadvantage that it takes a long time to restart the reactor, and the conventional steam-water separator has not sufficiently considered the suppression of the reactor pressure drop during the transient.

[0007]

The above-mentioned known techniques have the following problems. In the prior art steam separator, the reactor pressure drops from 70 atm to about 10 atm during the transient, and as a result, it takes a long time to restart the reactor. Consideration on the suppression of reactor pressure drop at the time was insufficient.

[0008]

According to the present invention, a pipe is extended from the discharge port of the second stage to the reactor water level, and the drain directly contacts the steam dome. It is characterized by forming a non-flow channel. According to a second aspect of the present invention, a protruding plate is formed from a stand pipe below the outlet of the first stage.

In other words, according to the above-described means, the pipe extends from the second stage drain port 105 to the reactor liquid level, and the subcool water flows through the pipe, so that the subcool drain water directly exchanges heat with the steam dome steam. In addition, unlike the conventional spray heat transfer, the heat transfer area is significantly reduced. Therefore, the decrease width of the reactor pressure also becomes small, and the decrease in the reactor pressure is suppressed.

According to the second means, a protruding plate is formed from the stand pipe below the discharge port of the first stage. The upper portion of the protruding plate is in a state of saturated water, and the lower portion of the protruding plate is formed of saturated water. It is in the state of subcool water. Therefore, the inertia force of the drainage is reduced by this protruding plate, and the entrained steam does not enter the subcooled water region (region B in FIG. 4) below the protruding plate, and condensing heat transfer is reduced. The decrease width of the reactor pressure is also reduced, and the decrease in the reactor pressure is suppressed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described with reference to FIG.

FIG. 1 is a longitudinal sectional view of a steam separator according to an embodiment of the present invention. The present invention is directed to a steam-water separator when a transient phenomenon occurs in which a reactor in which a main steam pipe and a water supply pipe are closed has a scram.

As shown in FIG. 1, after heating, an ascending gas-liquid two-phase flow or a water single-phase flow is introduced into a cylinder to form a spiral blade 10.
The structure is such that a swirling flow is given by 1 or the like. By forming a swirling flow in this manner, a centrifugal force is generated, and a liquid phase having a high density is collected on the outer peripheral portion of the cylindrical swirling drum 102, and separated from the steam flowing through the central portion by the pickoff ring 103.
The liquid phase collected on the outer periphery of the revolving drum descends through the liquid phase discharge flow path 104 provided on the outer periphery of the revolving drum, and is discharged into the recirculating liquid phase guided to the heating unit via the discharge port 105. Is done.

As shown in FIG. 1, the steam separator 8 comprises three stages, which are referred to as a first stage, a second stage, and a third stage from the lower side, and three discharge ports 105 are also provided. The pipe 201 extends from the second stage discharge port 105 to the reactor liquid level, and the subcooled water flows through the pipe 201. Therefore, the subcooled drainage does not directly exchange heat with steam in the steam dome. In contrast, the heat transfer area is significantly reduced. Therefore, the decrease width of the reactor pressure also becomes small, and the decrease in the reactor pressure is suppressed. As a result, there is an effect that the time required from the scram of the reactor to the restart thereof is shorter than in the conventional case.

FIG. 2 is a vertical sectional view of a steam separator according to a second embodiment of the present invention. A protruding plate 202 is formed from a stand pipe below the discharge port of the first stage. Above the protruding plate 202 is a state of saturated water, and below the protruding plate is a state of subcooled water. Therefore, the inertia force of the drainage is reduced by this protruding plate, and the entrained steam does not enter the subcooled water region (region B in FIG. 4) below the protruding plate, and condensing heat transfer is reduced. The decrease width of the reactor pressure is also reduced, and the decrease in the reactor pressure is suppressed. As a result, there is an effect that the time required from the scram of the reactor to the restart thereof is shorter than in the conventional case.

FIG. 3 shows the result of calculating the pressure reduction effect of the reactor pressure of the present invention using the transient analysis code TRACG. As shown in FIG. 1, according to the present invention, there is an effect that it is ensured that the reactor pressure is suppressed to about 65 atm even during a transition.

[0017]

According to the embodiment of the present invention, since the pipe 201 is provided from the second stage discharge port 105 to the reactor liquid level, it is ensured that the reactor pressure is suppressed to about 65 atm even during the transition. Has the effect.

According to the second embodiment of the present invention, the projecting plate 20 is provided below the outlet of the first stage from the stand pipe.
2, the effect of ensuring that the reactor pressure is suppressed to about 65 atm even during a transition.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a steam separator according to one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a steam separator according to one embodiment of the present invention.

FIG. 3 is a graph showing a pressure reducing effect characteristic of a reactor pressure according to the present invention.

FIG. 4 is a longitudinal sectional view of a steam-water separator showing a phenomenon model according to the related art.

FIG. 5 is a longitudinal sectional view of a boiling water reactor according to the prior art.

FIG. 6 is a longitudinal sectional view of a steam separator according to the related art.

[Explanation of symbols]

1 ... reactor pressure vessel, 2 ... feed water inlet, 3 ... downcomer,
4 internal pump, 5 core, 6 shroud head, 7 stand pipe, 8 steam separator, 9 steam dryer, 10 main steam pipe, 101 spiral wing, 102
... revolving drum, 103 ... pick-off ring, 104 ... discharge channel, 105 ... discharge port, 201 ... pipe, 202 ... projecting plate.

Claims (2)

[Claims] 1. A structure for applying a swirling force to a gas-liquid two-phase flow, a swirling body in which a swirling force is applied to the gas-liquid two-phase flow, and a separated liquid separated by the swirling body to the swirling body. 3 to discharge outside
A steam-water separator having a discharge channel composed of a plurality of stages, wherein the discharge ports of the second and third stages of the discharge channel are in direct contact with the steam dome. A steam-water separator for a BWR, wherein a pipe extends to a furnace water level to form a flow path in which drainage does not directly contact a steam dome. 2. A structure for applying a swirling force to a gas-liquid two-phase flow, a swirling body in which a swirling force is applied to the gas-liquid two-phase flow, and a separated liquid separated by the swirling body. 3 to discharge outside
A steam-water separator having a discharge flow path composed of a plurality of stages, wherein the discharge port of the discharge flow path of the first stage of the discharge flow path is located below the reactor water level. A steam-water separator for a BWR, wherein a protruding plate is formed from a stand pipe.