JPS6264989A - Steam separator for boiling water type 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 invention] The present invention guides the mixed flow of steam and water generated from the reactor core.

This invention relates to a steam-water separator for a boiling water reactor, which has a plurality of steam-water separators installed in a shroud head to separate steam and water, respectively.

[Technical background of the invention]

A plurality of conventional steam/water separators used in boiling water reactors are arranged in a shroud head portion, as shown in FIG. That is, a mixed flow of steam and water generated from the core 1 enters the upper plenum 2.

The water flows into the steam separator 4 through the stand pipe 3 that stands in the shroud head. The steam-water separator 4 has a structure as shown in FIG. Then, the swirling force is applied by the swirling blades 6, and the water rises inside the rotating Wi 47 while rotating in a spiral shape. At this time, the water with a large specific gravity is pressed against the inner wall of the rotating body 7 due to the centrifugal force. Since the steam with a small specific gravity flows through the center (core) of the swirl 1B17, steam and water separation is performed. A drain port 8 for discharging the separated water is provided above the rotating barrel 7, and water flowing along the inner wall of the rotating barrel 7 flows into the drain port 8, and the water flows through the rotating barrel 7 and the outer barrel. The water flows down the annular flow path 10 formed between the water and the water and is drained.

On the other hand, steam flowing through the center of the rotating shell 7 enters a steam outlet 11 above the rotating shell 7, passes through a steam exhaust pipe 12, and flows into a steam dome (not shown).

In the process described above, the mixed flow of steam and water is subjected to large flow resistance. In particular, pressure loss due to flow distribution when flowing from the upper plenum 2 into the standpipe 3 and pressure loss due to contracted flow.

The pressure loss when passing through the standpipe 3 and the pressure loss when passing through the swirl vane is large. If the pressure loss is large, the load on the recirculation pump will be large.

Furthermore, it is thought that the thermal-hydraulic stability of the boiling water reactor deteriorates because the natural circulation flow rate decreases when the recirculation pump is stopped. Therefore, the most important point in designing a steam/water separator is to reduce pressure loss as much as possible without impairing steam/water separation performance.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide a steam and water separator for a boiling water reactor, which reduces the pressure loss of the steam and water separator and reduces the load on the recirculation pump. It is about providing.

[Summary of the invention]

In order to achieve the above object, the present invention provides a steam-water separator for use in a boiling water nuclear reactor, in which the diameters of a standpipe, a riser connected to the standpipe, and a revolving barrel are made the same, and the diameter of the standpipe is made the same. Since the swirl vane is of a swirl type to give swirling force to the air-water mixed flow flowing in from the air-water mixture, it reduces the contracting flow pressure loss, the pressure drop of the stand pipe and riser, and the pressure drop of the swirl vane, and at the same time increases the swirling force. This improves separation performance.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of a steam separator according to an embodiment of the present invention. A plurality of steam/water separators 20 of this embodiment used in a boiling water nuclear reactor are arranged in a shroud head portion (not shown). The mixed flow of steam and water generated from the reactor core enters the upper plenum and enters the steam separator 20 through the stand pipes 21 arranged in the shroud head. The diameter of the swirling blade 23 is approximately the same as that of the riser 22 and the swirling barrel 24, and the swirling blade 23 is configured to have a swirl type, that is, to give a circumferential flow component to the axial flow, but not to give a radial flow component.

And stand pipe 21. The diameter of the riser 22 is approximately 20% thicker than that of a typical standpipe or riser used in a conventional boiling water reactor, and the diameter of the rotating shell is approximately 15% thinner. .

The mixed flow of steam and water flowing in from the standpipe 21 is
The riser 22, which is connected coaxially and with the same diameter as the standpipe, reaches the swirling blade 23, and is given a swirling force by the swirling blade 23 and ascends inside the rotating body 24 while rotating linearly.At this time, the specific gravity Large water rotates due to centrifugal force151
The steam that is pressed against the inner wall of the rotating shell 2 and has a low specific gravity is
Steam and water separation is performed in order to flow through the center (core) of 4. A drain port 25 for discharging separated water is provided above the rotating barrel 24, and water flowing along the inner wall of the rotating barrel 24 flows into the drain port 25 and is drained from the rotating barrel 24. The water flows downward through an annular flow path 27 formed between the outer cylinder 26 and is drained. On the other hand, the steam flowing through the center of the rotating shell 24 enters the steam outlet 28 above the rotating shell 24, passes through the steam exhaust pipe 29, and flows into a steam dome (not shown).

Next, it will be explained that pressure loss is reduced by using the steam/water separator molded as described above.

First, the contraction loss ΔPi when flowing from the upper plenum 2 to the standpipe 3. is given by the formula 0. Here, ζ: Contraction loss coefficient ρf: Saturated water density φ2: Two-phase pressure loss multiplication coefficient m: Flow rate A flowing into one steam-water separator Flow path area of Nistand pipe Note that Contraction loss coefficient ζ is It is a value of about 0.01 to 0.04 and does not depend on the flow path area A of the standpipe.

Now, assuming that the total number of steam-water separators is the same, the flow rate m flowing into each steam-water separator is the same. Also, the above ζ, φ,
Since ρ is also the same, the contraction loss Δ of the steam-water separator in this example is
Pγ□ and the contraction loss ΔP of a typical conventional steam/water separator? .

The ratio with is the following formula (■).

As shown by the above equation (2), in this embodiment, the total flow loss is approximately half. In the equation (2), the subscript N represents the steam/water separator of this embodiment, and the subscript 0 represents the conventional steam/water separator.

Next, the loss ΔPsR when passing through the stand pipe 3 and riser 5 is given by the following equation. Here, f: Wall friction coefficient L Sum of lengths of Nistand pipe and riser D Inner diameter of Nistand pipe and riser ρ: Average density of two-phase mixed flow g: Gravitational acceleration φf2: Two-phase friction pressure loss multiplication factor However Therefore, even if the diameters of the standpipe and riser change, the above f, L, and ρsag do not change, and ρf2 becomes slightly smaller as the inner diameter increases.

Therefore, in formula 0, the friction loss excluding the head ρwa-gL is reduced by about 40%.

Furthermore, the pressure loss of the swirl vane 6 is lower in the swirl type than in the conventional type.

On the other hand, the swirling body 7 becomes thinner by about 15%, but due to the swirling force of the swirling vanes 6, the two-phase mixed flow becomes a clean annular flow (a liquid film flows along the inner surface of the inner cylinder 7, and steam flows in the center). Therefore, the increase in frictional pressure loss is relatively small, about 25%.

When the above calculation was performed using a detailed analysis code and the pressure drop reduction rate of this example was investigated, the results shown in FIG. 2 were obtained.

It is clear from this that this example is effective in reducing pressure loss. Figure 3 schematically shows the increase in natural circulation and the increase in thermo-hydraulic stability margin. In Fig. 3, a is the natural circulation curve of a conventional nuclear reactor, b is a natural circulation curve of a nuclear reactor using the steam separator of the present invention, and C is a stability limit line. It can be seen that the natural circulation operation characteristics are improved in B compared to A.

Next, we will discuss the separation performance of the steam separator. Swirl blade 6
As a result of various experiments, it has been found that the swirling speed ω of a two-phase mixed flow is ωoc 1/rn (2), and n usually takes a value between 0.5 and 1.0.

Therefore, by making the rotating body 7 thinner, the rotating speed increases, so that the centrifugal force F=Mrω"QCMr"-" also increases the rotating speed fg
It can be seen that the thinner the A7, the stronger it is and the separation performance is improved.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to reduce pressure loss without impairing the separation performance of the steam separator, thereby reducing the load on the recirculation pump of a boiling water reactor and improving the natural circulation operation characteristics. It is possible to improve the reliability of boiling water reactors. Also a stand pipe,
Since the riser and rotating barrel have the same diameter, it is easy to manufacture the steam/water separator.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, FIG. 2 is a diagram showing the reduction rate of pressure loss, and FIG. 3 is a schematic diagram showing the increase in the amount of natural circulation and the thermo-hydraulic stability margin. FIG. 4 is a schematic diagram showing the arrangement of reactor internals of a conventional boiling water reactor, and FIG. 5 is a schematic sectional view of the steam-water separator shown in FIG. 4. 20... Steam water separator 21... Stand pipe 22... Riser 23... Swivel vane 24.
...Swivel body 25...Drain port 26...Outer cylinder 27...Annular flow path 28...Steam discharge port 29...Steam discharge pipe agent Patent attorney Noriyuki Chika 1q: Ni Table Dal＼
Text Figure 4 Figure 5

Claims (1)

[Claims] (1) In a steam separator used in a boiling water reactor, the diameters of the standpipe, the riser and the rotating barrel connected to the standpipe are approximately the same, and the diameter of the steam and water mixture flowing from the standpipe is A steam-water separator for a boiling water nuclear reactor, characterized by a swirl-type swirling vane for applying swirling force.