KR20060098266A - Flow mixing header for an integrated reactor downcomer - Google Patents

Abstract

The present invention relates to an integrated reactor downflow channel, which consists of an annular cavity-type vertical grid structure installed in the downflow channel to solve the non-uniformity of the coolant core inlet temperature, which occurs when the steam generator cassette in some zones is not operated. It relates to a number of fluid mixing headers.

The present invention includes a main coolant pump installed at a high temperature portion on the outer periphery of the reactor, a plurality of steam generator cassettes installed at a rear end of the main coolant pump, and a downward flow passage installed between the steam generator cassette and the core inlet. To an integral reactor that permits no water supply to the water supply pipes of the some zones by output heat removal or residual heat removal operation accompanied by a residual heat removal system failure of the some zones after the shutdown of the reactor. In the flow mixing header having a rectangular cross-section, stacked in multiple stages installed in the downward passage, the inner and outer surfaces of each stage of the flow mixing header from the steam generator cassette to the core inlet Multiple inlet and outlet flow paths, each of which allows a mixed flow of It is characterized by.

Reactor, Downflow Channel, Mixing Head, Steam Generator Cassette, Core Inlet

Description

FLOW MIXING HEADER FOR AN INTEGRATED REACTOR DOWNCOMER}

1 is a schematic diagram schematically showing a separate reactor according to the prior art,

Figure 2 is a longitudinal sectional view schematically showing a general integrated reactor according to the prior art,

3 is a schematic diagram schematically showing a downward channel of an integrated reactor having an inner shield according to the prior art;

4 is a schematic diagram schematically showing a steam pipe and a water feed pipe of a CAREM integrated reactor according to the prior art;

5 is a schematic view showing the steam generator outlet temperature distribution during the residual heat removal system 1 train operation in a CAREM integrated reactor;

6 is a schematic diagram schematically illustrating a reactor including a flow mixing header and a peripheral device for a downward flow channel according to the first and second embodiments of the present invention;

7 is a perspective view showing a flow mixing header for the downcomer according to the first embodiment of the present invention,

8 is a flow passage conceptual diagram of a flow mixing header according to the first and second preferred embodiments of the present invention.

<Explanation of symbols for the main parts of the drawings>

21, 31: reactor pressure vessel, 22, 32: reactor core,

23, 33: steam generator cassette, 24, 34: downward flow channel,

25: internal shield, 35, 45: fluid mixture header,

36: outer cylinder, 37: inner cylinder,

38: inlet flow path, 39: exit flow path,

40: inner side, 50: outer side,

100, 200: reactor.

The present invention relates to an integrated reactor downflow channel, and more particularly, to an annular cavity type vertically installed in the downflow channel to solve the non-uniformity of the coolant core inlet temperature generated when the steam generator cassette of some zones is not operated. A plurality of flow mixing headers having a lattice structure.

In general, nuclear power plants usually consist of more than 100 individual functions. These are largely divided into nuclear steam supply systems centered on nuclear reactors, generator systems such as turbines that run steam generators, and other ancillary equipment. Hereinafter, in the present specification, the nuclear steam supply system is referred to as a primary side and the generator system as a secondary side.

A nuclear reactor is a device designed to be used for various purposes such as generating heat by artificially controlling the nuclear fission reaction of fissile material, producing radioisotopes and plutonium, or forming a radiation field, and is a key component of the primary side. to be.

FIG. 1 shows a conventional loop type pressurized water reactor (PWR) 100, which includes a reactor 120, a pressurizer 130, a steam generator 140, and a main coolant pump in a containment vessel 110. 150 are separated and they are each connected via a pipe. The steam turbine 160 receives steam from the steam generator 140 to turn the generator 170 to produce electricity.

2 illustrates a cross-section of an integral nuclear reactor with no pipes, unlike a separate nuclear reactor as described above. As shown in the integral type reactor 200, as long as the cyclers of the pressurizer 230, the steam generator 240, and the main coolant pump 250 constituting the nuclear steam supply system are the same as the reactor 220. Pressure vessels 210 are installed without pipes.

The coolant heated in the reactor is supplied to the main coolant pump 250, and then the coolant passes through the main coolant pump 250, and the flow direction thereof is changed downward to be supplied to the upper annular cavity of the steam generator 240. The coolant cooled by the heat exchange while passing through the steam generator 240 is supplied to the reactor 220 through the downward channel again.

The integrated reactor 200 as described above may basically eliminate the large coolant loss accident of the existing separate reactor. That is, it has the advantage of excellent safety, miniaturization, and economic efficiency.

3 is a cross-sectional view of an integrated reactor including a downward channel according to the prior art. As shown in the drawing, the reactor assembly includes main equipment such as a pressurizer (not shown), a steam generator cassette 23, and a main coolant pump (MCP, not shown) constituting the nuclear steam supply system as shown. Together, the reactor pressure vessel 21 is installed without a connection pipe. The coolant heated at the core of the integrated reactor is supplied to the MCP, and the coolant is supplied to the upper annular cavity of the upper side of the steam generator cassette 23 by changing the flow direction as it passes through the MCP. The coolant cooled by heat exchange with the secondary side while passing through the cassette 23 is supplied to the reactor core 22 through the sewer channel. Such integrated reactors can fundamentally exclude the loss of large coolant in the existing separate reactor. That is, it has the advantage of excellent safety, miniaturization, and economic efficiency.

As shown in FIG. 3, the downlink channel 24 according to the prior art has an inner shield 25 which is a plate-shaped steel structure for reducing the volume of the reactor vessel and reducing the neutron flux to the outside of the reactor pressure vessel in order to utilize space. It is installed continuously in the radial direction. As the temperature decreases as it passes through the steam generator cassette, coolant flows through the internal shield and into the core.

However, in the conventional reactor down water reactor having the internal shield 25, if the steam generator cassette of one or two zones is stopped, the temperature of the stopped steam generator cassette may increase greatly unless the steam and water supply pipes are properly arranged. Can be. In addition, since the coolant passing through the cassette does not have a circumferential flow component but mainly has a vertical flow component and flows into the core, when the steam generator cassette is partially stopped, a local temperature difference of the core temperature is large. A description is given below with reference.

This is undesirable for safe operation of the reactor and must be prevented and mitigated.

In the prior art, the nonuniformity of the coolant core inlet temperature, which occurs when the steam generator cassettes in some of these zones are not operated, has been solved by the complicated design of the routing of the zone water supply pipe and the zone steam pipe.

4 shows the routing of the zone water supply pipe 60 and the zone steam pipe 70 of CAREM, an integrated reactor under development in Argentina.

In this figure, in order to solve the nonuniformity of the coolant core inlet temperature generated when the steam generator cassette of some zones is not operated in a nuclear power plant equipped with an integrated reactor downflow channel without a flow mixing header according to the prior art. The routing of the designed zone water supply pipe 60 and the zone steam pipe 70 is shown.

The area supply pipe (60) and the area steam pipe (70) of CAREM are routed to uniformly reflect the effects on the steam generator cassette installed in the entire circumferential direction when some areas of the power conversion system or residual heat removal system fail. )do.

The zone water supply pipe (60) and the zone steam pipe (70) are classified as high-energy pipes and should be designed to meet the requirements of separate installation and physical barriers in preparation for virtual pipe break accidents. However, the area water supply pipe 60 and the area steam pipe 70 having complicated routing are difficult to design / manufacture / install to satisfy the high energy piping related requirements, causing an increase in manufacturing costs and safety concerns.

Figure 5 shows the steam generator cassette 23 outlet temperature distribution when the reactor is cooled using only one train of residual heat removal system in CAREM which is an integrated reactor. Although only one train is being operated, the temperature distribution is not biased to a specific quadrant of the reactor by the complexly arranged zone water supply pipe 60 and the zone steam pipe 70. That is, the quadrant is uniformly affected by the residual heat removal system.

However, in the CAREM of FIG. 5, it can be seen that temperature non-uniformity was alleviated but a completely uniform temperature distribution was not obtained. Furthermore, the high temperature and the low temperature still appear alternately in units of the steam generator cassette 23. In other words, the steam generator cassette 23 outlet temperature at which the water supply is supplied is high, while the steam generator cassette 23 outlet temperature is not low. As a result, the result shows that the problem of reduction of core critical heat flux and local temperature increase are not completely solved.

For this reason, there has been a constant demand for a uniform reactor inlet temperature during output operation or residual heat removal operation in isolation of some zones.

The present invention is to solve the problems as described above, by providing a plurality of flow mixing headers in a grid structure continuous in the vertical direction to the reactor vessel downflow channel by the zone isolation output operation and the residual heat removal system of two adjacent zones after the reactor shutdown. It can maintain the core inlet temperature uniformly during the residual heat removal operation with failure, reduce the critical heat flux of the core, prevent the local temperature rise of the core, and consequently the complex structure area used in the existing integrated reactor It is an object of the present invention to provide a flow-mixing header for an integral reactor for downcoming the reactor, which can greatly simplify the water supply pipe and the zone steam piping, thereby reducing the cost of constructing the nuclear power plant and improving safety.

In order to achieve the object as described above, the present invention, the main coolant pump is installed in the high temperature portion on the outer periphery of the reactor, a plurality of steam generator cassette installed in the rear end of the main coolant pump, the steam generator cassette is installed between the core inlet Water is supplied to the water supply pipes of the partial region by a residual heat removal operation including a downflow channel and an output operation in a state in which some sections of the steam generator cassette are isolated or a residual heat removal system failure of the partial sections after the reactor stops. An integrated reactor allowing unoperable operation, having a rectangular cross section and having a multi-stacked structure, which is installed in the downward channel, the inner and outer surfaces of each stage of the flow mixing header. There are a plurality of feeds that enable feedwater from the steam generator cassette to the core inlet. And it characterized in that the sphere flow path sphere and the outlet passage are each formed sphere.

The plurality of inlet flow paths are uniformly distributed on the inner surfaces of all the stages of the flow mixing header and the plurality of outlet flow paths are distributed only in a portion of the outer surface of each end of the flow mixing header, or the plurality of inlet The flow path sphere is distributed only to a certain portion of the inner side of each stage of the flow mixing header, and the plurality of outlet flow paths are evenly distributed on the outer side of all the stages of the flow mixing header.

Here, the predetermined portion is the following equation: circumferential angle = 360 ° / number of stages of the flow mixing header; It may be the angular portion of the circumference determined by. In addition, the predetermined portions may not overlap in the flow header of each stage.

In this case, when the flow mixing headers of the stages overlap each other, the inlet flow passage openings or the outlet flow passage openings are distributed on the circumference of the flow mixing header.

The number of flow mixing headers is set equal to the number of secondary steam / water supply zones or in multiples of two.

Hereinafter, with reference to the drawings will be described in detail a preferred embodiment according to the present invention. It is intended here that the scope of the invention is not limited to these embodiments. In addition, the same components generally refer to the same reference numerals in different drawings.

FIG. 6 shows two types of flow mixing headers 35 and 45 and peripherals in accordance with an exemplary embodiment of the present invention installed in the downcomer 34 of the SMART reactor as an integrated reactor.

6 (a) shows a flow mixing header according to the first embodiment of the present invention, and FIG. 6 (b) shows a flow mixing header according to the second embodiment. Here, the flow mixing headers 35 and 45 form a hollow quadrangle in cross section, and have a multi-stage structure in which a plurality of headers are stacked in a vertical direction.

Since all the coolant must flow in and out through the headers 35 and 45, upper and lower portions of the headers 35 and 45 may be formed by extending a portion such as the blocking unit 80. In addition, the present inventors have confirmed that the flow-mixing headers 35 and 45 replace the conventional inner shield 25, and the problem of radiation emission does not occur despite such replacement. In other words, the coolant in the header (35, 45) is a result of sufficiently blocking the radiation.

In the first embodiment of FIG. 6 (a), the core 32 is an energy production source for producing energy through a nuclear fission reaction, and the steam generator cassette 33 is a device for producing steam by transferring energy to the secondary side. The integrated reactor downflow channel 34 is composed of a flow mixing header 35 installed in multiple stages in the vertical direction, an outer cylinder 36 on the outside, and an inner cylinder 37 on the inside. The inner cylinder 37 provides a flow path for guiding the coolant discharged from the steam generator cassette to the flow mixing header 35, and the flow mixing header 35 guides in the direction to discharge the coolant introduced from the inner cylinder 37. The outer cylinder 36 guides the coolant discharged from the flow mixing header to the core. The same applies to the second embodiment of Fig. 6 (b).

In the first embodiment a plurality of circular inlet flow paths 38 are distributed throughout the inner face 40 of all of the flow mixing headers 35 and a plurality of circular outlet flow paths 39 are each of the flow mixing headers 35. Are installed on the outer side 50 of the range corresponding to one quadrant of each. On the other hand, in the second embodiment, the plurality of circular inlet flow paths 38 are distributed on the inner face 40 in the range corresponding to one quadrant of each flow mixing header 45 and the plurality of circular outlet flow paths 39 are It is distributed throughout the outer face 50 of all flow mixing headers 45.

In the present invention, the number of stages of the flow mixing header (35, 45) is stopped by the equilibrium of the coolant temperature of the side including the stationary steam generator cassette 33 and the coolant temperature of the opposite side including only the healthy steam generator cassette 33 It is configured to prevent the continuous temperature rise in the steam generator cassette (33). In this concept, the number of stages of the flow mixing headers 35 and 45 is set equal to the number of zones on the secondary side, or in multiples of two. For example, if the secondary steam / supply piping is divided into four zones, four or two drainage mixing headers are installed. It is also an effective way to increase the number of stages of the flow mixing header to enhance the flow mixing effect in the downcoming channel. However, the present inventors have constructed the optimized stage as described above in consideration of the manufacturability of the flow mixing header and the pressure resistance of the flow.

In the present invention, as shown in Figs. 6 to 8, the two types of flow mixing headers 35 and 45 installed in four stages on the assumption that the secondary steam / water supply pipe is divided into four zones will be described. It is.

FIG. 7 illustrates a three-dimensional flow mixing header 35 according to the first embodiment of the present invention. Although the three-dimensional illustration of the flow mixing header 45 according to the second embodiment is not shown separately, those skilled in the art can easily deduce from FIG.

FIG. 7 illustrates a state of the flow mixing header 35 installed in the downcoming channel 34 and an enlarged state of the fluid mixing header 35 taken out of the downcoming channel 34. In the present figure, the coolant uniformly introduced into all the headers through the plurality of inlet flow passages 38 distributed on the inner surface 40 of the flow mixing header 35 installed in the downward channel 34 is It is discharged to each quadrant in turn through a plurality of outlet flow paths 39 provided only in a portion corresponding to one quadrant of the outer face 50 of the header.

The distribution of the outlet flow path 39 is described in detail. In the four-stage flow mixing header 35, the 360 ° range of the circumference is divided by the number of stages of the header (ie, 4), and the header of each stage is 90 °. Each section of the range has an outlet flow path 39.

For example, the top header has an outlet flow passage 39 only in the first quadrant, the second header from the second quadrant, the third header from the third quadrant, and the bottom header from the fourth quadrant.

Therefore, the outlet flow path 39 in Fig. 7 is shown only in the range of the first quadrant of the top header and the fourth quadrant of the bottom header on the drawing. As such, it is preferable that the predetermined portions on which the outlet flow passages 39 are installed do not overlap each other so that the coolant is evenly discharged on all outer peripheries of the flow mixing header 35.

In this case, the four-stage flow mixing header 35 is fixed in the radial direction so that the flow mixing header 35 of each stage collects about 1/4 of the flow rate from each of the twelve steam generator cassettes 33. It is preferable to be inclined at an angle α (see Fig. 8). Such angle α is determined according to the number of stages of the downcomer 34.

Through such a flow mixing process in each header of the flow mixing headers 35 and 45, it is possible to equalize the temperature distribution of the healthy zone and the stationary zone even in a situation where water is not supplied to some zones. In addition, it has the effect of switching the discharge flow path of the steam generator cassette 33 discharged only in the downward direction to the existing CAREM and SMART research in the wall direction, thereby improving the flow mixing effect and mixing the low temperature and high temperature coolant flowing into the core. Can enhance the effect.

FIG. 8A shows the positions and flow paths of the inlet flow passage 38 and the outlet flow passage 39 of the first header above the flow mixing header 35 according to the first embodiment. Each header, labeled 1, 2, 3, 4 in FIG. 8 (a), only releases coolant to the 1, 2, 3, and 4 quadrants, respectively. The coolant flowing out of the steam generator cassette 33 into the inner cylinder 37 enters each flow mixing header 35, moves circumferentially, and is discharged toward the outer cylinder 36 through a portion of a specific quadrant range.

The flow paths 38 and 39 may have various shapes such as triangles and ellipses, but are preferably circular in order to facilitate the flow of the coolant. If the number and diameter are too small, the flow mixing effect increases but the pressure drop increases. Increases, causing an increase in the dose of MCP. On the other hand, if the number and diameter of the flow paths 38 and 39 are too large, the flow mixing effect may be reduced and the integrity of the structure may be weakened.

Therefore, the number, diameter, and distribution of the inlet flow passage 38 and the outlet flow passage 39 are determined so that the pressure drop through the header does not increase while the flow mixing effect is not reduced. Each header indicated by 2, 3 and 4 in FIG. 8 (a) has the same operating principle as the header indicated by 1 in FIG. 8 (a) and releases the coolant only in the 2, 3 and 4 quadrants, respectively.

As the second embodiment of the present invention, the flow mixing header 45 is similar to the first embodiment, and the flow path is shown in FIG. 8 (b) with the concept that the installation positions of the flow paths 38 and 39 are reversed. . When installing the flow mixing header 45 according to the second embodiment as shown in Fig. 8 (b), the steam generator cassette 33 through a plurality of circular inlet flow passage 38 installed in one quadrant of the inner surface 40 Coolant from one zone is introduced into one flow mixing header, and the coolant is uniformly discharged 360 degrees in all directions through the outlet flow passage 39. That is, the coolant flows into only the 1, 2, 3, and 4 quadrants of the headers indicated by 1, 2, 3, and 4, respectively, and the introduced coolant flows through the flow distribution process in the flow mixing header (45). Is emitted over 360 degrees on the outer periphery.

As described above, according to the first and second embodiments of the present invention, the coolant introduced from the inner cylinder over the entire circumferential range of the multistage mixing header passes through the mixing process in the flow mixing header to form the circumferential front of the mixing header. It is distributed to the outer cylinder side over the range. Through this flow distribution process, a uniform coolant temperature distribution of 360 ° symmetry can be obtained even in a case where the cassette of some zones is stopped. In addition, the flow mixing header according to the present invention has an effect of converting the discharge flow path of the steam generator cassette in the wall direction, thereby enhancing the flow mixing effect to enhance the mixing effect of the low temperature and high temperature coolant flowing into the core.

While the invention has been shown and described with respect to particular embodiments, it will be understood by those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the invention as indicated by the appended claims. Anyone can grow up easily.

According to the present invention having the above configuration, the water supply is not supplied to the water supply pipes of some zones by the residual heat removal operation accompanied by the residual heat removal system failure of two adjacent zones after the output operation or the reactor stop in a state in which some zones are isolated. Even under the circumstances, the circumferential flow generated in each flow mixing header can greatly increase the temperature uniformity at the core inlet, so that the inlet temperature of the core can be uniformly provided in the case of installing a downward channel without the flow mixing header. The need for zonal water supply pipes and zonal steam pipes with the complex routing required to make them is eliminated, resulting in reduced plant construction costs and improved reactor operating margins.

Claims (5)

A main coolant pump installed at a high temperature portion on the outer circumference of the reactor, a plurality of steam generator cassettes installed at a rear end of the main coolant pump, and a downward flow channel installed between the steam generator cassette and the core inlet, and a part of the steam generator cassette; In an integrated reactor that permits no water supply to the water supply pipes of the partial region by the residual heat removal operation accompanied by the residual heat removal system failure of the partial region after the output operation or the reactor stop in the state of isolating, As a flow-mixing header having a cross-section of the filling type rectangular shape, and stacked in multiple stages installed in the downward channel, On the inner and outer surfaces of each stage of the flow mixing header, a plurality of inlet flow passages and outlet flow passages for supplying water from the steam generator cassette to the core inlet are respectively formed. Mixed header. The method of claim 1, The plurality of inlet flow paths are uniformly distributed on the inner surfaces of all the stages of the flow mixing header and the plurality of outlet flow paths are distributed only in a portion of the outer surface of each end of the flow mixing header, or the plurality of inlet Flow passages are distributed only in a certain portion of the inner surface of each stage of the flow mixing header and the plurality of outlet flow paths are uniformly distributed on the outer surface of all the ends of the flow mixing header flow Mixed header. The method of claim 2, The portion is given by the formula: Circumferential angle = 360 ° / number of stages of flow mixing header; A circumferential angular portion determined by the unitary reactor downflow flow mixture header. The method of claim 3, And said predetermined portions do not overlap in the flow headers of the respective stages. The method according to any one of claims 1 to 4, And the number of the fluid mixing headers is increased to the same number or multiples of two as the number of secondary steam / water supply zones.

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