JPS6235291A - Gas-water separator for nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a steam-water separator for a nuclear reactor suitable for a boiling water nuclear reactor, and particularly for discharging a separated liquid separated from a gas-liquid two-phase flow. This invention relates to a steam-water separator for nuclear reactors with an improved liquid discharge flow path.

[Technical background of invention]

Generally, in a boiling water reactor, the coolant is boiled by heat generated from a large number of fuel assemblies in the reactor core, and the coolant is combined into a gas-liquid two-phase mixed flow in an upper plenum above the core. , and is led to a steam separator to separate it into steam and liquid. The steam 11i11 separated here is stored in a dryer (steam dryer).
The liquid is then introduced into the reactor core to sufficiently remove moisture and sent to the turbine chamber, and the liquid is returned to the core from the lower plenum.

By the way, the gas-liquid separation performance of the steam/moisture 1111 device is mostly determined by carryover and key under.

In other words, if the separation of the gas-liquid two-phase mixed flow introduced into the steam-water separator is insufficient, part of the liquid becomes droplets and is discharged from the steam exhaust channel while remaining mixed with the steam. . Carryover represents the weight of the separated liquid discharged from the steam exhaust channel relative to the steam, and the larger the ratio, the more humid steam will be led to the dryer, and the dryer will be able to remove moisture sufficiently. If not, there is a risk of damaging the turbine W.

On the other hand, steam may form bubbles and flow out together with the separated liquid from the liquid discharge channel, and the ratio of the steam to the separated liquid is called carry under. Ki 1? A large leunder means that the fractionation efficiency of the pressurized water l1lff device is degraded, and there is also a risk that bubble-like steam may flow into the downcomer together with the separated liquid, causing cavitation in the recirculation pump or jet pump.

In other words, air moisture 1! As for lfi performance, the smaller the carryover and 1J lead-under, the better.

Up to now, numerous tests and analyzes of the characteristics of steam/moisture 1m vessels have been conducted both in foreign countries and in Japan, and have contributed to the design and improvement of steam/moisture 1m vessels. According to these, carryover and carryunder are mainly caused by the flow rate and steam weight ratio of the gas-liquid two-phase mixed flow flowing into the steam separator.
and the reactor water level, and these correlations are determined by the sixth
As shown in the figure.

Therefore, in the design of the steam/moisture TL vessel, it is necessary to
The shape and dimensions are selected in consideration of the characteristics shown in FIG. 6 from the phase mixing flow rate, quality, standard water level, etc.

The multiple steam/water separator assemblies configured in this way are
For example, in a boiling water nuclear reactor, as shown in FIG. 7, each steam/water 11 vessel assembly 2 is assembled into a steam/water separator 3 on a shroud head 1 with the upper ends of each steam/water 11 vessel assembly 2 aligned on the same plane. Since the shroud head 1 is placed on the head of the shroud 4 and is formed into an upwardly convex dome shape, the stand vibro connecting each steam separator assembly 2 and the upper plenum 5 is placed on the outer peripheral side. The pipe length is getting longer.

[Problems with background technology]

1 liter of conventional nuclear reactor steam moisture configured in this way
The lt device had the following problems.

(1) The inflow a of the gas-liquid two-phase mixed flow into each steam-water separator assembly 2 is not uniform, and the flow a into the steam-water separator assembly 2 disposed at the center on the shroud head 4 is uneven. The inflow population was
The number of items placed on the outer periphery also increases.

(2) The reactor water level existing in the gap between the two groups of 111tW air/moisture assemblies is not uniform, and the water level between the central parts is
higher than the water level between its outer peripheries.

FIG. 8 shows an example of an analysis of the flow velocity distribution of the gas-liquid two-phase mixed flow flowing into such a conventional steam-water separator 3 and the flow behavior within the upper brenum 5.

The arrows in FIG. 8 indicate the speed and direction of the flow in the upper plenum 5 and the stand vibro.

The reason why the flow rate decreases on the outer circumferential side as shown in Figure 8 is as follows.
The further the stand vibro is located on the outer periphery, the longer it becomes, resulting in a correspondingly larger pressure loss. Also, because the shroud head 1 has an upwardly convex dome shape, the flow toward the center inside the upper blenheim 5 increases. This is because

Furthermore, it is clear from measurement results using a full-scale test device that the reactor water level between the steam-water separator assemblies 2 is high at the center and low at the outer periphery.

The reason why the reactor water level has such a difference in height is thought to be as follows. The liquid separated by each steam-water separator assembly 2 is transferred to each liquid discharge channel of each steam-water separator assembly 2, to the gap between the two groups of steam-water separator assemblies, to the shroud 4, and to the reactor pressure vessel (not shown). It reaches a lower plenum (not shown) through each darankama formed by the inner wall. Since the gap between the two groups of steam-water separator assemblies is narrow, the flow path resistance is large and the water level is increased by the head loss. For this reason, the reactor water level is higher at the center than at the outer periphery.

Therefore, the inflow flow rate of the gas-liquid two-phase mixed flow is larger in the steam-water separator assembly 2 disposed at the center of the shroud head 4, and the water level around its periphery is higher, resulting in a large carryover. . On the other hand, since the inflow flow rate to the steam-water separator assembly 2 disposed on the outer periphery is small and the water level is low, the under temperature becomes large. For this reason, the conventional method of uniformly setting and arranging the specifications of the steam/water valve M unit based on the average inflow flow rate and standard water level makes it difficult to minimize carryover and carryunder for the steam/water separator as a whole. It was difficult.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a steam-water separator for a nuclear reactor that improves gas-liquid separation function with a simple configuration.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention reduces the flow path resistance of the liquid discharge passage of the air/water valve 1111t device assembly disposed in the center of the shroud head to the air/water valve disposed at the outer periphery of the shroud head. The feature is that the flow path resistance is smaller than the flow path resistance of the liquid discharge path of the separator assembly.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 shows a vertical cross section of a main part of a steam/water separator assembly 10 assembled in an embodiment of the present invention, in which an inner cylinder 12 and a swirl 1113 are placed in an outer cylinder 11 at a required interval. They are housed one after another and coaxially to form a triple cylinder. A guide vane 14 is connected to the lower end of the revolving l113, and the guide vane 14 communicates via a riser pipe 15 with a stand vibe installed on a shroud head (not shown). A two-phase mixed flow is introduced. Therefore, the gas-liquid two-phase mixed flow flowing into the guide vane 14 via the stand pipe and riser pipe 15 is given a rotational force here, and the rotating body 1
3, it spirals, and gas and liquid are separated by centrifugal action. Here, the separated vapor flows while swirling as shown by the broken line arrow in the figure, while the separated liquid becomes a liquid film along the inner wall of the rotating body 13 as shown by the solid line arrow in the figure. Rise upward.

The upper end of the revolving barrel 13 is connected to a steam exhaust passage 16 having a slightly smaller diameter than the revolving barrel 13, and a short tubular shape coaxially arranged with a required gap is set on the outer periphery of the lower end of the steam exhaust passage 16. An annular ring 18 is installed in the radial direction between the upper end of the tube 17 and the upper end of the inner cylinder 12, and an annular liquid inlet 19 is provided around the outer periphery of the lower end of the steam exhaust passage 16 to allow a liquid film to flow into the steam discharge channel 16. ing. The liquid inlet 19 is connected to the drain port 2 through a liquid discharge passage 20 in an annular space defined by the rotating body 13 and the inner cylinder 12.
1, and the reactor water W is overflowing to the height above the drain port 21.

An annular resistance ring 22 is fixed to the inner wall surface of the inner cylinder 12 at its axially central portion to prevent the separated liquid flowing down the liquid discharge channel 20 from flowing excessively.

The value of the flow path resistance of this resistance ring 22 is determined for each steam separator assembly 1 assembled on the shroud head (not shown).
0, the flow path resistance of the resistance ring 22 of the steam/water separator assembly 10 located centrally on the shroud head is different depending on the location of the steam/water separator assembly 10 located at the outer periphery of the shroud head. The flow path resistance is set to be smaller than the flow path resistance of the ten resistance rings 22.

FIG. 2 shows the correlation between the flow path resistance value of the resistance ring 22 and the carryover and the key 1v lead-under. FIG. 2 shows a curve that is almost the same as the relationship between the reactor water W and the leakage under and carryover shown in FIG. 6(A), and this can be considered as follows.

That is, when the water level of the reactor water W rises, the static pressure at the drain port 21 of the liquid discharge channel 20 increases by the amount of the head valve, so the flow rate of the separated liquid flowing in the liquid discharge channel 20 decreases.
The corresponding amount of liquid flows out from the steam exhaust channel 16 together with the steam. This is the reason for the increase in carryover.

Furthermore, if the flow rate of the separation liquid is reduced, the amount of air entrained therein is also reduced, resulting in a reduction in carry-under. Such a phenomenon also occurs by increasing the flow resistance of the liquid discharge flow path 20. Zunawara, resistance ring 22
If the resistance value of is increased, the flow rate of the separation liquid is decreased, so the carryover increases and the chitley under is decreased for almost the same reason as mentioned above.

Therefore, a resistance ring 22 with a small resistance value is provided in the liquid discharge passage 20 of the steam separator assembly 10, which is disposed in the center of the shroud head where the water level of the reactor water W is high. A resistance ring 22 having a large resistance value is provided in the liquid discharge channel 20 of the steam/moisture device assembly 10 which is arranged at the outer periphery with a low resistance.

According to this, it is possible to reduce the carryover of the steam/water separator assembly 10 in the central portion, and also reduce the key under of the steam/water separator assembly 10 in the outer peripheral portion.

This will be explained using FIG. 3 and mathematical formulas.

FIG. 3 is a schematic diagram showing the vicinity of the liquid discharge channel 20 of the steam/water separator assembly 1o. The pressure PA at point A at the upper end of the liquid discharge channel 20, and the pressure P at point B at the drain port 21.
8 is expressed as the following equation based on the law of conservation of momentum.

(PA+ρ1oL1)-PB...(1) ρ1:Liquid+J) Average density f of the fluid flowing through the outlet channel 20
: Friction coefficient Dll of the liquid discharge channel 20 : Hydraulic equivalent diameter Δ of the liquid discharge channel 20 : Channel area K of the liquid discharge channel 20 : Resistance value m of the resistance ring 22 : Fluid flowing through the liquid discharge channel 20 Mass flow rate q: Gravitational acceleration Also, the pressure P8 at point B is PB-Po+ρ2G12 (2
) Po : Pressure in the steam dome part ρ2 : Average density of the fluid existing in the 1 m gap between the steam and water separator assemblies 10 L2 : Water level from the water surface of the reactor water W to point B On the other hand, from the law of conservation of mass, Inflow flow lftm into the steam/water separator assembly 10
The following equation (3) holds true between 1n and m in equation (1) above.

X: Average steam weight ratio (quality) inside the rotating shell 13 Co: Carryover Cu: Killer under m10: Mass flow rate flowing into the steam/water separator assembly 10 From the above equations (1), (2), and (3) If the water level changes by ΔL2 and the flow rate changes by Δmin, the resistance ring 2
If the resistance value K of 2 is changed by [the following margin] ...... (4), the characteristics of the steam-water separator assembly 10 can be made equivalent to the case where the reactor water W level and its flow rate do not change. can do.

That is, if the inflow flow ff into the steam separator assembly 10
After standard conditions of 1m1n", quality X* and water level L2*, the dimensions and resistance values that minimize carryover and carryunder are 11* and K, respectively.
*, and the carryover and carryunder values at that time are Go'' and Cu'', respectively. In this case, depending on the position where the steam/water separator assembly 10 is disposed on the shroud head (assuming that it is r ml away from the center), each liquid discharge flow is adjusted so that the following equation (5) is satisfied. By adjusting the flow path resistance of channel 20, carryover and carryunder can be minimized.

K(r) x (min(r) −min">...
(5) FIGS. 4 and 5 respectively show other embodiments of the present invention, in which the resistance value of the resistance ring 22 of the liquid discharge channel 20 in the air/moisture 111fti1 assembly 10 is kept constant without changing. , no example is shown in which the flow path length J3 and the flow path area are changed depending on whether the shroud head (not shown) is placed in the center or on the outer periphery thereof.

As shown in FIG. 4 (Δ), the inner cylinder 12 of the steam separator assembly 1o is arranged in the center of the shroud head.
The length of the cylinder is made shorter than the inner cylinder 12 of the steam/water separator assembly 10, which is not shown in FIG. Road 20
The length of the flow path is shortened, and the flow path resistance is set to be low.

Further, as shown in FIG. 5(A), the liquid discharge channel 2 of the steam/water separator assembly 10 is disposed in the center of the shroud head.
The flow path area SA of 0 is made larger than the flow path area S of the steam/water separator assembly 10 disposed on the outer periphery shown in FIG. is set small.

〔Effect of the invention〕

As explained above, the present invention provides a rotating shell that separates gas and liquid by swirling a gas-liquid two-phase flow, and a liquid discharge that discharges the separated liquid separated by the rotating barrel from a drain port that opens into reactor water. A steam and water valve for a nuclear reactor in which a plurality of steam and water separator assemblies each having a flow path are assembled on a shroud head that curves convexly upward.
In a 1 liter vessel, the flow resistance of the liquid discharge passage of the steam separator assembly disposed at the center of the shroud head is equal to the flow passage resistance of the liquid discharge passage of the steam separator assembly disposed at the outer periphery. The flow path resistance was designed to be smaller than that of the

Therefore, according to the present invention, it is possible to reduce both the carry-over and carry-under of the entire steam-water separator assembled on the shroud head, and to improve the gas-liquid separation performance.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of a steam/water separator assembly incorporated in an embodiment of the present invention, and FIG. 2 shows flow resistance in a liquid discharge channel of the steam/water separator assembly, carryover and carry-over. A graph showing the general correlation with the under, FIG. 3 is a schematic diagram of the main part of FIG. 1, and FIG. 4 (A) and (B) show other embodiments of the present invention. FIG. 5 (△) (B), which is a schematic diagram showing a comparison between the center arrangement and the outer peripheral arrangement of the separator assembly, roughly shows another embodiment of the present invention. A schematic diagram comparing the central arrangement δ and the outer peripheral arrangement for a three-dimensional structure, and Figure 6 (A) (8) shows the correlation between carry-under and carry-over, and the reactor water level and the inlet flow ω of the liquid discharge channel. A graph showing the relationship, Figure 7 is a front view showing the assembly and arrangement of a general steam-water separator for nuclear reactors, and Figure 8 is a schematic diagram of the main parts showing the flow of the gas-liquid two-phase mixed flow in the upper blennium. It is. 10... Steam water separator assembly, 11... Outer cylinder, 12...
... Inner cylinder, 13 ... Swivel body, 14 ... Guide vane, 1
5... Riser pipe, 19... Liquid inlet, 20... Liquid discharge channel, 21... Discharge port, 22... Resistance ring, W
...Reactor water.゛Representative Patent Attorney Noriyuki Ken Yudo Hiroshi Mimata Flow path resistance direct firefly 2 Diagram center Outer periphery <A) ・(B) Sheep 4 Moon center Tato part (A) CB) $5 Diagram ( 13) )′[13jtf Brown 6 Fig.

Claims (1)

[Claims] 1. A swirling barrel that swirls a gas-liquid two-phase flow to separate gas and liquid;
A plurality of steam/water separator assemblies each having a liquid discharge channel for discharging the separated liquid separated in the rotating shell from a drain opening into the reactor water are assembled on a shroud head that curves convexly upward. In the steam-water separator for a furnace, the flow resistance of the liquid discharge passage of the steam-water separator assembly disposed at the center of the shroud head is determined by A steam-water separator for a nuclear reactor, characterized in that it is configured to have a flow resistance smaller than that of a liquid discharge flow path. 2. The steam separator assembly located at the center of the shroud head has a resistance ring in its liquid discharge passage whose flow resistance is higher than that of the liquid discharge passage of the steam separator assembly located at the outer periphery. A steam-water separator for a nuclear reactor according to claim 1, which is set to be small. 3. The axial length of the liquid discharge passage of the steam/water separator assembly located at the center of the shroud head is set to be shorter than that of the liquid discharge passage of the steam/water separator assembly located at the outer periphery. A steam-water separator for a nuclear reactor according to claim 1. 4. The steam/water separator assembly located at the center of the shroud head has a liquid discharge passage whose cross-sectional area is wider than that of the liquid discharge passage of the steam/water separator assembly located at its outer periphery. A steam-water separator for a nuclear reactor as set forth in claim 1.