JPS587960B2 - core spray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a core spray device, and particularly to a core spray device that is effective even in a steam atmosphere.

Boiling water reactors are equipped with a core spray device to cool the reactor core in the event of a loss of coolant accident.

A core spray device is comprised of a header provided above a core within a reactor pressure vessel, a number of spray nozzles provided in the header, and a cooling water supply pipe connected to the header.

The cooling water supply pipe has a pump and is connected to a condensate storage tank and a pressure suppression chamber in which cooling water is stored.

The pressure suppression chamber is provided to condense steam released into the dry well containing the reactor pressure vessel.

Different types of spray nozzles are provided to spray cooling water evenly over the reactor core.

FIG. 2 shows a conventional example of one type of spray nozzle provided in a header.

The nozzle body 2 of the spray nozzle 1 is attached to a header (not shown).

A baffle plate 3 is arranged at the opening of the nozzle body 2, and the baffle plate 3
is fixed to the nozzle body 2 by a mandrel 4.

An annular spout 5 is formed between the nozzle body 2 and the baffle plate 3.

Cooling water 6 supplied into the nozzle body 2 from the header becomes an annular cooling water flow 7 from an annular jet port 5 and is ejected upward from the reactor core.

This type of spray nozzle 1 may not be able to spray cooling water evenly in a reactor pressure vessel filled with water vapor due to a loss of coolant accident.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a core spray device that can evenly spray coolant.

A feature of the invention is that the spray nozzle is provided with a communication tube that communicates the inner region of the annular coolant stream ejected from the spray nozzle with the outer region of the annular coolant stream.

It has been experimentally confirmed that the spray angle θ of the annular cooling water stream ejected from the conventional spray nozzle 1 becomes narrower in a steam atmosphere.

The experimental results will be explained in detail below.

Figure 2 shows a conceptual diagram of a core spray system for a boiling water reactor.

The core spray system is one of the emergency core cooling systems that is activated in the event of a loss of coolant accident.

A reactor core 10 configured by loading a large number of fuel assemblies 9
is formed within a core shroud 8 located within a reactor pressure vessel (not shown).

The core spray device includes a ring header 11 disposed above the reactor core 10 in the reactor pressure vessel, a number of spray nozzles 1 attached to the ring header 11, and one end connected to the ring header 11 and the other end outside the reactor pressure vessel. It is composed of a cooling water supply pipe 12 connected to a condensate storage tank and a pressure suppression chamber.

In the event of a loss of coolant accident in a nuclear reactor, cooling water is spouted above a reactor core 10 from a large number of spray nozzles 1.

The broken line shown in FIG. 2 shows the shape of the cooling water jetted from the spray nozzle 1.

Since the core spray device is for maintaining core cooling in the event of a loss of coolant accident, the cooling water jetted from the spray nozzle 1 must be supplied to all fuel assemblies 9.

The mounting angle and number of the spray nozzles 1 are therefore determined in such a way that the cooling water is sprayed as evenly as possible over all the fuel channels 9.

Cooling water is spouted from the spray nozzle 1 after a coolant loss accident, and the atmosphere from which the cooling water is spouted is filled with water vapor.

Generally, the cooling water spouted from the spray nozzle 1 will flow in the direction shown by 7 in FIG. 1 unless there is a correlation with water vapor in the atmosphere.

This is because the flow inside the spray nozzle 1 is dispersed by the action of the baffle plate 30.

However, since the cooling water jetted above the reactor core 10 is usually in an unsaturated state, heat exchange occurs between the cooling water jetted from the spray nozzle 13 and the water vapor in the atmosphere.

Water vapor condenses on contact with cooling water. External region 1 outside the annular cooling water stream 7 emerging from the spray nozzle 1
In No. 3, even if water vapor condenses, the space volume is large, so the pressure reduction effect due to condensation is small.

On the other hand, the internal region 14 inside the annular cooling water flow 7 has a small space volume and is surrounded on all sides by a water film or a large number of water droplets, and the amount of water vapor supplied from the external region 13 is small, so that the water vapor is The decompression effect due to condensation increases.

That is, the pressure in the inner region 14 is lower than that in the outer region 13, and due to this pressure difference, the annular cooling water flow 7 is drawn toward the inner region 14, canceling out the cooling water dispersion effect by the baffle plate 21. .

For example, using spray nozzle 1 with a diameter of 1 inch,
An experiment was conducted in which cooling water at a temperature of °C was spouted into saturated steam at atmospheric pressure at a flow rate of 250 l/min, and the spray angle θ of the annular cooling water flow 7 sprayed water was 90° in air where the correlation with the atmosphere could be ignored. However, the result was that this angle θ was narrowed to 20°.

Thus, the spray angle θ of the annular cooling water stream 7 in water vapor
If the area becomes narrow, cooling water will not be sufficiently distributed locally within the entire core, and there is a possibility that the intended purpose of the above-mentioned core spray device cannot be achieved.

The present invention was made based on the above experimental results, and prevents the spray angle θ of the annular cooling water flow from decreasing in a steam atmosphere by communicating the external region and the internal region of the annular cooling water flow. It is.

A preferred embodiment of the present invention will be described below based on FIG.

The core spray device 15 of this embodiment is obtained by changing only the spray nozzle 1 of the core spray device shown in FIG. 2 to the spray nozzle 16 shown in FIG. 3.

The spray nozzle 16 includes a nozzle body 17, a baffle plate 18, and a communication pipe 20 having a through hole 21.

The baffle plate 18 is arranged at one opening of the flow path 23 in the nozzle body 17 , and an annular jet orifice 19 is formed between the nozzle body 17 and the baffle plate 18 .

The nozzle body 17 is attached to the ring header 11, and the other opening of the flow path 23 communicates with the inside of the ring header 11.

The communication pipe 20 is arranged within the flow path 23 and supports the baffle plate 18.

The outer diameter of the annular spout 19 is 1 inch.

In the event of a loss of coolant accident in a boiling water reactor, the cooling water in the condensate storage tank or pressure suppression chamber is guided into the ring header 11 by the cooling water supply pipe 12, and the spray nozzle 1
The annular cooling water flow 22 is ejected from the annular jet port 19 of No. 6 above the reactor core 10, which is a steam atmosphere.

FIG. 4 shows the spray angle θ of the annular cooling water flow jetted from the spray nozzle 1 and the spray nozzle 16 in relation to the spray flow rate of the cooling water.

Spray flow rate is expressed as a percentage of the rated spray flow rate.

Characteristic 24 in FIG. 4 shows the change in the spray angle θ at the spray nozzle 1, and characteristic 24 shows the change in the spray angle θ at the spray nozzle 16.

These spray angles θ are the results of an experiment when cooling water was jetted from each spray nozzle into a saturated steam atmosphere at atmospheric pressure.

In the spray nozzle 1, the spray angle θ decreases to 200 when the spray flow rate reaches about 50% of the rated value, and the spray angle θ does not increase even if the spray flow rate exceeds this value.

On the other hand, in the spray nozzle 16, the spray angle θ of the annular cooling water flow 19 corresponds to 90° until the spray flow rate reaches 130% of the rated value.

In the spray nozzle 16, the outer region 26 and the inner region 27 of the annular cooling water flow 19 are communicated by the through hole 21 of the communication pipe 20, and the water vapor in the outer region 26 is transferred to the inner region 27.
This prevents the internal region 27 from being depressurized and eliminates the reduction in the spray angle θ of the annular cooling water flow 22.

As a result, the cooling water sprayed from the core spray device 15 is effectively dispersed without being locally concentrated, so that the cooling water can be evenly sprayed above the core section 10.

A spray nozzle according to another embodiment of the present invention is shown in FIG.

The same components as the spray nozzle 16 are indicated by the same reference numerals, and only different parts will be explained.

The spray nozzle 28 differs from the spray nozzle 16 in that a long communication tube 29 having a through hole 21 is used, and the tip of the communication tube 29 is made to protrude from the baffle plate 18.

It goes without saying that it is best to position the open end 30 in the internal region 27 of the communication tube 29 on the central axis of the annular cooling water flow 22; An experiment was conducted to find the optimal point of distance.

That is, the distance L from the open end 30 of the communication pipe 29 to the baffle plate 18 was varied, and the spray angle θ of the annular cooling water flow 22 was measured.

Outer diameter D of the annular spout 19 of the spray nozzle 28 used
was 1 inch, the spray atmosphere was saturated steam at atmospheric pressure, and the spray flow rate was in the range of 170 to 250 l/min.

FIG. 6 shows the results of this experiment.

The distance L between the baffle plate 18 and the open end 30 is the distance L between the spray nozzle 2
It can be seen that the effect of suppressing the decrease in the spray angle θ of the annular cooling water flow 22 is remarkable in a range where L/D is 4 times or less than the diameter D of the annular opening 19 of No. 8, particularly in a range where L/D is 9 or less.

However, when L/D is larger than 14, almost no effect can be expected.

This is because, due to the effect of gravity, the spray angle θ of the annular cooling water flow 22 becomes smaller as the distance from the baffle plate 18 increases, and at a distance from the baffle plate 18, there are many sprayed water droplets in the center of the internal region 27. It's for a reason.

Even if water vapor is supplied into such a region from the open end 30, it will condense and become useless for maintaining the pressure in the internal region 27.

From the above results, in the example shown in FIG.
0 and the baffle plate 18 is 1 of the diameter D of the annular opening 19.
By making it four times or less, the spray angle θ of the annular cooling water flow 22 can be made larger than that of the spray nozzle 1.

Further, in the spray nozzle 28, the baffle plate 18 is supported by the communication pipe 29, so the structure is simple.

The spray nozzle 28 has an open end 30 with an annular cooling water stream 2
2, but even if it is offset from the central axis, if it communicates with the interior region 27, it is effective in maintaining the pressure in the interior region 27, and the spray angle θ of the annular cooling water flow 22 is reduced. can be suppressed.

FIG. 7 shows a spray nozzle 31 of a core spray device according to another embodiment of the present invention.

The spray nozzle 31 is provided with a large number of openings 33 on the distal end side of the baffle plate 18 of a communicating pipe 32 that attaches the baffle plate 18 to the nozzle body 17 .

In this case, it is necessary that the distance from the baffle plate 18 to the opening 33 provided at the position closest to the baffle plate 18 be 14 times or less, preferably 9 times or less, the diameter D of the annular opening 19.

Other embodiments of the spray nozzle are shown in FIGS. 8 and 9.

The spray nozzle 33 attaches a communication tube 34 to the baffle plate 18 in the radial direction of the annular opening 19 .

One end of the communication pipe 34 is attached to the nozzle body 17.

The core spray device provided with the spray nozzle 33 has the same effect as the embodiment described above, except that the structure of the spray nozzle 33 is slightly more complicated and the opening area of the annular opening 19 is slightly reduced.

According to the present invention, the coolant can be evenly distributed in the reactor core.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a spray nozzle provided in a conventional core spray device, FIG. 2 is a conceptual diagram of a core spray device for a boiling water reactor, and FIG. 3 is a spray nozzle provided in a core spray device of the present invention. A vertical cross-sectional view of the nozzle, FIG. 4 is a characteristic diagram showing the relationship between spray flow rate and spray angle, and FIG.
7 and 8 are longitudinal cross-sectional views of other embodiments of the spray nozzle, FIG. 6 is a characteristic diagram showing the relationship between ('I, /D) and the spray angle, and FIG. 9 is the same as that of FIG. It is a view taken along arrow IX-II. 9...Fuel assembly, 10...Reactor core,
11... Ring header, 12... Cooling water supply piping, 15... Core spray device, 16
, 28, 31, 33... spray nozzle, 18
... Baffle plate, 19 ... Annular opening, 2
0, 29, 32, 34...Communication pipe, 26...
...external area, 27...internal area.

Claims (1)

[Claims] 1. A header disposed above the reactor core within the reactor vessel;
A reactor core spray device comprising means for supplying coolant into the header in the event of a loss of coolant accident in a nuclear reactor, and a spray nozzle provided in the header and spraying the coolant in an annular shape above the reactor core. A core spray device characterized in that the spray nozzle is provided with a communication pipe that communicates an internal region of an annular coolant flow ejected from the spray nozzle with an external region of the annular coolant flow. 2. A header located above the reactor core within the reactor vessel;
means for supplying coolant into the header in the event of a loss of coolant accident in a nuclear reactor; a baffle plate provided in the header at an opening from which the coolant is spouted; A core spray device comprising a spray nozzle that sprays the coolant in an annular manner above the reactor core, wherein a communication pipe connects an internal region of the annular coolant flow sprayed from the spray nozzle and an external region of the annular coolant. is provided in the spray nozzle, and the baffle plate is supported by the communication pipe.