JPH046496A - Spontaneous circulation type boiling water reactor - Google Patents

Abstract

PURPOSE:To reduce a pressure loss and thereby to lessen reduction of a spontaneous circulation flow rate and to improve safety of operation by a method wherein a steam-water mixed liquid produced from a core is made to meander several times by porous cylindrical bodies and led to a steam dome in the upper part of a reactor pressure vessel. CONSTITUTION:A curved blind plate 22 and porous cylindrical bodies 23 are provided between the upper part of a shroud 17 and a steam dome 18, and the porous cylindrical bodies 23a to 23e being different in the inside diameter are disposed in a plurality of layers in the axial direction concentrically, while each of the cylindrical bodies 23a to 23e is provided with a number of channel holes 24a to 24e. In a normal operation, cooling water boiling in a core 14 rises through a rise part 15. Water vapor containing a liquid droplet running out of a liquid surface flows laterally since the dome-shaped blind plate 22 is provided above, and it is separated into steam and water until it flows to the steam dome 18 through the cylindrical bodies 23 provided in a plurality of layers.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is a natural circulation type boiling system which is an improved steam and water separator for separating the combined temperature of air and water generated from a reactor core into steam and water, respectively. Regarding water reactors.

(Prior Art) A plurality of conventional steam/water separators 4 used in a boiling water nuclear reactor are arranged in a head portion 26 of a shroud 25, as shown in FIG. That is, a mixed flow of steam and water generated from the reactor core 1 enters the upper plenum 2, passes through the stand pipes 3 standing in the shroud head portion 26, and flows into the steam separator 4.

The steam/water separator 4 has a structure as shown in FIG.
The mixed flow of steam and water flowing from the standpipe 3 reaches the swirling vane 6 from the riser 5, which is connected coaxially and with the same diameter as the standpipe 3, and is given a swirling force by the swirling vane 6, and as it swirls in a spiral shape. It ascends inside the rotating trunk 7. At this time, water with a high specific gravity is pressed against the inner wall of the rotating body 7 by centrifugal force, and steam with a low specific gravity flows through the center (core) of the rotating body 7, so that steam and water separation is performed.

A drain port 8 is installed above the rotating body 7 to drain the separated water. The water flowing along the inner wall of the rotating body 7 flows through the drain port 8 and flows into the rotating body 7 and the outer cylinder 9.
The water flows above the annular flow path 10 formed between the first and second channels. On the other hand, the steam flowing through the center of the rotating body 7 enters the steam exhaust r'-1111 knee above the rotating body 7.
Steam 1 flows into a steam dome (not shown) via an outlet pipe 12.

(Problems to be Solved by the Invention [7]) In the process described in 1-1 below, the mixed flow of steam and water is subjected to large flow resistance. In particular, the pressure loss caused by current distribution when flowing from Brenna As 2 to 3, the pressure loss caused by contraction, the pressure loss when passing through stand vibe 3, and the swirling vane. The pressure loss during operation is large. If the honeycomb loss is large, the natural #M recirculation flow rate decreases, which poses a problem in that the thermal-hydraulic stability of the boiling water reactor deteriorates.

The present invention has been made to solve the problems mentioned above.
Its purpose is to serve as both a steam separator and a steam dryer.

It is an object of the present invention to provide a natural circulation type buttonic water type raw-L reactor 4 which is designed to reduce pressure loss, minimize the reduction in natural circulation current, and improve operational stability.

[Structure of the invention]

(Means for Solving the Problem 1) The present invention provides a nuclear reactor vessel (1), a reactor core arranged therein,
The shroud surrounding this reactor core [1] and this shroud 1
- inside the ii In a low water separator used in a natural circulation nuclear reactor consisting of a connected lower blennium, a dome-shaped blind plate is installed between the lower part of the head plate of the reactor pressure vessel and the sealing part of the reactor pressure vessel. The T side of the peripheral part of this blind plate and the T side
hi The feature is that a plurality of porous cylindrical bodies are stacked on top of each other, and the holes of each of the porous cylindrical bodies are arranged in a staggered pattern.

In addition, the cylindrical body is also characterized in that the hole diameter of each cylindrical body stacked in multiple layers is large in the hand saw and gradually becomes smaller as it goes toward the front side. ) The present invention has the above-mentioned structure for the upper part of the reactor pressure vessel of the Jt7" reactor pressure vessel, so that the mixed flow of steam and water generated from the reactor core does not meander around the porous cylinder several times, and then the upper part of the reactor pressure vessel It will lead you to the steam dome. As a result, steam and water are efficiently distributed, the steam flows into the steam dome 11, and the droplets flow into the downcomer.

In this gas-liquid separation process, the mixed flow of steam and water that is generated in the reactor core during normal operation can be separated into steam and water, respectively, in order to reduce pressure loss.

(Example) With reference to FIGS. 1 and 2, implementation of a natural circulation boiling water type f-reactor according to the present invention will be described.

In FIG. 1, a reactor core 14 is disposed within a reactor pressure vessel 13, and the reactor pressure vessel
an elongated cylindrical shroud l formed between the rising part 15 and the downcomer from which the coolant falls;
'7 is set with the core 14 as the base point. A steam tom 18 is inserted between the upper head plate 13a that closes the first end of the reactor pressure vessel 13, and the drain J at J. The steamer in 18 is sent from a main steam pipe 19 to a turbine (not shown). After finishing its work in the turbine, water is condensed in the steam condenser, and the coolant flows from the water supply pipe 20 into the reactor pressure vessel 13.9 This coolant flows from inside the reactor pressure vessel 1:3 into the downcomer 16. flows down and flows into the reactor core 14 through the groove 1 nosum 21.

Shroud 17 (7) , , , , ll:. A curved blind plate 22 and a porous cylindrical body 23 are provided between the steam dome 18 and the steam dome 18. The porous cylindrical body 23 is partially enlarged in FIG. Una structure number: 7.

That is, the porous cylindrical bodies 2:bi have different inner diameters.

23b, 23e, 23d, 2 buttons are arranged concentrically in multiple layers in the axial direction, and each cylindrical body 2
3a=・23e is a device in which a large number of flow passage holes 24a□24e are provided. In FIGS. 1 and 2, the solid line arrow - indicates the flow of coolant, and the dashed line arrow → indicates the flow of steam. Each flow is shown below. Next, the operation of the natural circulation boiling water reactor in the above embodiment will be explained.

During normal operation, cooling water boiled in the core 14 ascends the rising section 15, and water vapor containing droplets that has flowed out of the liquid surface Q is disposed of in a lateral direction due to the dome-shaped blind plate 22 installed above. The water is separated into steam and water before flowing into the steam dome 18 through the porous cylindrical body 23 arranged in multiple layers. Specifically, as shown in FIG. 2, the mixed liquid at temperature of air and water first passes through the channel hole 24a of the porous cylinder 23a. Channel hole 2
The steam/water mixture that has passed through 4a collides with the wall of the next porous cylindrical body 23b, and the steam falls upward and the droplets fall downward and are separated. The separated vapor and droplets collide with the steam/water mixture flowing in from another channel hole 24a, and enter the next channel hole 24b.

Furthermore, it collides with the wall of the porous cylindrical body 23c, and steam and water are similarly separated. By repeating these actions, steam and water can be efficiently separated. In addition, due to the natural circulation operation characteristics, the rate of rise of the steam-water mixture is slower than in conventional boiling water reactors, so even such a simple structure can perform the functions of steam-water separation and steam drying.

In this example, the pore diameters of each porous cylinder were made to be the same size, but as shown in FIG. In order to improve the water separation effect, the diameter of the channel hole 24 of each porous cylindrical body 23 of the plurality of layers may be made larger toward the bottom and gradually smaller toward the top.

〔Effect of the invention〕

According to the present invention, during normal operation, pressure loss can be reduced by eliminating the conventional gas-liquid separator and steam dryer without impairing the performance of the 5-gas water separator. The natural circulation operation characteristics of water reactors can be improved, and reliability can also be improved. Further, the reactor internal structure can be simplified and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of a natural circulation boiling water nuclear reactor according to the present invention, FIG. 2 is an enlarged vertical cross-sectional view of section A in FIG. Side view seen from 8 directions in the figure,
FIG. 4 is a side view showing a conventional boiling water reactor from the core to a steam separator, and FIG. 5 is a longitudinal cross-section showing the steam water separator in FIG. 13...Reactor pressure vessel 14...Reactor core 15...
Rising part 16...Downcomer 17...Shroud 18...Steam dome 19...Main steam pipe 20...Water supply pipe 21...Lower plenum
22... Blind plate 23. 23a-23e... Porous cylindrical body 24, 24a-24e... Channel hole agent Patent attorney Noriyuki Ken Yudai, 3 Flash

Claims (1)

[Claims] A reactor core disposed within a reactor pressure vessel, a shroud surrounding the reactor core, a rising portion for cooling water and steam located above the reactor core inside the shroud, and a reactor core disposed within the reactor pressure vessel; In a natural circulation boiling water reactor comprising an annular downcomer formed between and a lower plenum connected below the downcomer, there is a gap between the lower part of the upper head plate of the reactor pressure vessel and the rising part. A dome-shaped blind plate is provided, and a plurality of layers of porous cylinders are stacked between the lower side of the peripheral part of the blind plate and the inner wall of the reactor pressure vessel, and the holes of each of the porous cylinders are arranged in a staggered manner. A natural circulation boiling water reactor that is characterized by