JPH02120693A - Natural convection type boiling water nuclear reactor - Google Patents

Abstract

PURPOSE:To eliminate a conventional steam separator, to improve an operational characteristics of natural convection in a boiling water nuclear reactor and to improve its reliability as well by providing a plurality of domed porous plates which are placed above a riser. CONSTITUTION:During an normal operation of a nuclear reactor, cooling water being boiled at a reactor core 2 goes upwardly in a riser 3 and steam containing water drips is separated into steam and water respectively by porous plates 23 laminated manifoldly. The separated steam flows in a main steam pipe 10, flows into a turbine and works there. On the other hand, the separated water at a steam dryer 24 is introduced along the porous plates 23 to a drain pipe 26. This separated water and residual cooling water are mixed with cooling water which flows in through a feed water pipe 11, flows down in a down comer 4 and flows into the reactor core 2 again from a lower plenum. In this case, for the reason that a conventional steam separator is eliminated and steam separation is conducted by a steam dryer made of a manifoldly laminated porous plates having the same shape of a dome as a shape of an upper lid of a nuclear reactor pressure vessel, a pressure loss can be well diminished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a type of boiling water nuclear reactor (hereinafter referred to as BWR) in which a light water coolant is driven by natural circulation.

(Prior Art) A BWR boils light water coolant in a reactor core and sends the generated steam to a turbine outside the reactor to generate electricity. Conventionally,
Commercially available high-power types circulate this light water coolant within the reactor pressure vessel by force-driving multiple circulation pumps.

Recently, so-called small and medium-sized BWRs, which have relatively small power generating capacity, have been attracting attention. Also, this medium and small B
The attributes of WR are expected to have inherent security. At this time, it is considered that the coolant is naturally circulated within the reactor core only by the buoyancy of the bubbles generated by the boiling phenomenon, without using a circulation pump or the like, which is a dynamic device.

FIG. 4 is a schematic cross-sectional view of a conventional natural circulation type BWR, and the conventional example will be explained with reference to FIG. Reference numeral 1 in FIG. 4 is a reactor pressure vessel, and a reactor core 2 is disposed within this reactor pressure vessel 1. reactor core 2
An elongated riser (also referred to as a shroud) 3 is provided surrounding the reactor pressure vessel 1, and an annular downcomer 4 is formed between the riser 3 and the reactor pressure vessel 1. An upper plenum 5 is formed above the core 2, and a shroud head 6 is provided in the upper plenum 5.

A stand pipe 7 is connected to the shroud head 6, and a steam separator 8 shown in FIG. 5 is connected to the stand pipe 7. A steam dryer (dryer) 9 is provided above the steam separator 8 with a space provided therein. A main steam pipe 10 is connected to the side surface of the reactor pressure vessel 1 where the steam dryer 9 is located, and a water supply pipe 11 through which coolant flows is connected to the side surface where the stand pipe 7 is located. Although not shown, control rods and a control rod drive mechanism are provided below the core 2. Further, in the figure, reference numeral 12 indicates a gas-liquid two-phase interface boiled in the reactor core 2, and reference numeral 13 indicates bubbles or voids in the liquid.

Here, the coolant is caused to S* in the core 2, more gas-liquid two-phase flow is collected in the shroud head 6 and stand pipe 7, and the gas-liquid two-phase flow is guided upward by surrounding it with the cylindrical riser 3. The two-phase interface 12 is formed at a predetermined position of the gas-liquid separator 8.
form. A region of vapor flow will be generated above the two-phase interface 12, but after separating the gas and liquid in the gas-liquid separator 8 located at the upper end of the liquid level, the vapor is further dried in the steam dryer 9. let The highly dry steam thus dried is led to the turbine system through the main steam pipe 10 to generate electricity, and then condensed in the condenser, and this condensate is sent from the water supply pipe 11 to the reactor pressure vessel. Return to within 1.

On the other hand, the liquid separated by the steam/water separator 8 flows down the annular downcomer 4 as a circulating flow rate. Since the core 2 has a two-phase flow and the riser 3 has a single-phase flow, sharing the interface 12,
In this way, the difference in the amount of voids (bubbles) 13 inside and outside the core 2 increases the driving force accordingly, and the coolant can be driven by natural circulation. The steam/water separator 8 has a structure as shown in FIG. That is, the mixed flow of steam and water flowing from the standpipe 7 reaches the swirling blade 15 through the riser 14 connected coaxially and with the same diameter as the standpipe 7, and is given a swirling force by the swirling blade 15, causing it to spiral in a spiral pattern. At the same time, it ascends inside the rotating trunk 16. At this time, the liquid with a high specific gravity is pressed against the inner wall of the whirlpool WA1B due to centrifugal force, and the steam with a low specific gravity flows through the center (core) of the whirlpool #A16, so that steam and water separation is performed. A drain port 1γ for discharging separated water is provided above the rotating body 16. The liquid flowing along the inner wall of the whirlpool W416 flows into the drain port 17, and flows through the annular flow path 1 formed between the whirlpool barrel 16 and the outer cylinder 18.
9 and is drained.

On the other hand, steam flowing through the center of the swirling shell 16 enters a steam outlet 20 above the swirling shell 16, passes through a steam exhaust pipe 21, and flows into a steam dome (not shown).

(Problems to be Solved by the Invention) In the process described above, the mixed flow of steam and water is subjected to large flow resistance. In particular, pressure losses due to flow redistribution and pressure losses due to contractions when entering the standpipe 7 from the upper plenum 5.

The pressure loss when passing through the stand pipe 7 and the pressure loss when passing through the swirl vanes are large. When the pressure drop is large, the natural circulation flow rate decreases, which poses the problem of worsening the thermal-hydraulic stability of boiling water reactors.

The present invention has been made to solve the above problems, and serves as both a steam separator and a steam dryer to reduce pressure loss, minimize the reduction in natural circulation flow rate, and improve operational stability. The object of the present invention is to provide an improved natural circulation boiling water reactor.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a reactor pressure vessel in which a main steam pipe is connected to an upper end plate and a water supply pipe is connected to a side surface, and a reactor core disposed within this reactor pressure vessel. a riser surrounding the reactor core and extending to the vicinity of the location where the water supply pipes are connected; a steam dryer formed by stacking a plurality of dome-shaped perforated plates provided above the riser; Features: Cooling water heated in the reactor core, characterized in that it is equipped with a drain pipe that allows moisture separated in the steam dryer to flow down to a downcomer formed between the reactor pressure vessel and the riser. The water boils and rises in the riser as a gas-liquid two-phase flow containing voids, and the water vapor containing droplets is released from the gas-liquid two-phase interface and flows into a steam dryer made of a perforated plate where it becomes a gas-liquid two-phase flow. Separated.

The separated dry steam passes through a number of holes in the steam dryer and flows through the main steam pipe to the turbine. The vapor and liquid are separated in the steam dryer, and the condensed droplets flow down the drain pipe, flow through the downcomer, and flow into the lower part of the reactor core. The liquid that has entered the core is heated again in the core, forms a gas-liquid flow in the same manner as above, and is separated into gas and liquid in a steam dryer.

The steam heated in the core in this way passes through the perforated plate of the steam dryer and from the main steam pipe to the turbine, while the separated droplets naturally flow along the perforated plate through the downcomer and flow back into the core. It can be allowed to circulate naturally.

(Example) An example of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, a reactor core 2 is disposed within a reactor pressure vessel 1, and a long cylindrical riser 3 surrounds the reactor core 2.
is installed. An annular downcomer 4 is formed between the riser 3 and the inner wall of the reactor pressure vessel 1. The upper cover (end plate) la of the reactor pressure vessel 1 is formed into a dome-shaped curved surface, and the main steam pipe 10 is connected to the upper end of the upper cover 1a. Further, a water supply pipe 11 is connected to the upper side surface of the reactor pressure vessel 1 . Furthermore, at the upper part of the reactor pressure vessel 1, as shown in FIG. is installed. The end of the perforated plate 23 is fixed to the support plate 25.
5 is connected to a drain pipe 26. The open end of the drain pipe 26 is located inside the downcomer 4.

In addition, in this embodiment, the steam/water separator 8 shown in the conventional example shown in FIGS. vessel 24
The height is maintained to the extent that almost gas-liquid separation is achieved.

During normal operation of the reactor, cooling water boiled in the reactor core 2 rises in the riser 3, and water vapor containing droplets is separated into steam and water by the perforated plates 23 stacked in multiple stages. Ru. The separated steam flows through the main steam pipe 10 and flows into the turbine to perform work. On the other hand, the water separated in the steam dryer 24 is led to the drain pipe 26 along the perforated plate 23. This separated water and remaining cooling water are transferred to water supply pipe 1
Downcomer 4 mixes with the cooling water that has flowed in through 1.
It descends inside the reactor core 2 and flows into the core 2 again from the lower plenum.

According to this embodiment, conventional air and moisture! Remove the container and install a multi-stage dome-shaped perforated plate similar to the top cover of the reactor pressure vessel V1
Since steam and water are separated in a layered steam dryer, a large height can be secured from the gas-liquid two-phase interface to the steam dryer.

FIG. 3 shows another example of the steam dryer 24, in which a plurality of pockets 27 are provided in the perforated plate 23 to enhance the centrifugal effect. Note that, since the flow of water vapor tends to concentrate near the center, the distribution of pores can be changed so that the resistance is greater near the center.

[Effects of the Invention] According to the present invention, pressure loss can be reduced by omitting the conventional steam/water separator without impairing the properties of steam drying. Therefore, it is possible to improve the natural circulation operation characteristics of the boiling water reactor and improve its reliability.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view diagrammatically showing an embodiment of the boiling water nuclear reactor according to the present invention, FIG. 2 is a vertical cross-sectional view showing an enlarged main part of FIG. 1, and FIG. Another example of FIG. 2 is schematically shown [
4 is a longitudinal sectional view diagrammatically showing a conventional boiling water reactor of this type, and FIG. 5 is a longitudinal sectional view showing the steam-water separator in FIG. 4. 1...Reactor pressure vessel 2...Reactor core 3...Riser 4...Downcomer 5...Upper plenum 6...Shroud head 7...Stand pipe 8...Steam water separator 9 ... Steam dryer 10 ... Main steam pipe 11 ... Water supply pipe 12 ... Gas-liquid two-phase interface 13 ... Void. 15...Swirl blade. 17... Drain port. 19... Annular channel. 21... Steam exhaust pipe 22... Hole. 24...Steam dryer. 26...Drain pipe 27...Pocket 14...Riser 16...Swivel trunk 18...Outer cylinder 20...Steam outlet 23...Perforated plate 25...Support plate (8733) agent

Claims (1)

[Claims] A reactor pressure vessel with a main steam pipe connected to the upper end plate and a water supply pipe connected to the side, a reactor core disposed within this reactor pressure vessel, and a position surrounding this reactor core and connected to the water supply pipe. A riser that extends to the vicinity, a steam dryer that is formed by laminating a plurality of dome-shaped perforated plates provided above the riser, and a steam dryer that separates moisture from the reactor pressure vessel and the riser. A natural circulation boiling water nuclear reactor characterized by comprising a drain pipe that flows down to a downcomer formed between the two.