KR20050009401A - Safety injection tank with sealing device for passive type fluidic device - Google Patents

Abstract

PURPOSE: A safety injection tank for a passive type flow controlling apparatus is provided to prevent a gas leakage without using an active control method by using a gas sealing device. CONSTITUTION: A safety injection tank includes a passive type flow controlling device having an emergent furnace cooling agent injection tube, a plurality of low level inducing tubes, and a high level inducing tube(20). The high level inducing tube includes a flange portion(25) which is extended to have a predetermined outer diameter in a direction horizontal to a radius direction thereof. The safety injection tank further includes a plurality of sealing plate guiding bars(30), a fluid guiding cylinder(40), a sealing plate(50), a plurality of spacing hooks(60), and a fluid blocking plate(70). The sealing plate guiding bars are extended from an edge of the flange portion to a predetermined height. The fluid guiding cylinder includes a penetration hole(35). The sealing plate includes guiding holes in a number equal to that of the sealing plate guiding bars. The spacing hooks are inserted to an upper portion of the sealing plate guiding bars. The fluid blocking plate blocks a direction flow through the penetration hole while maintaining a predetermined spacing from an upper portion of the fluid guiding cylinder.

Description

SAFETY INJECTION TANK WITH SEALING DEVICE FOR PASSIVE TYPE FLUIDIC DEVICE}

The present invention relates to a safety injection tank for storing emergency core coolant to be injected into the reactor in an emergency, and more particularly, a passive flow rate for supplying a large amount of coolant at the beginning of an accident and then supplying a small amount of coolant for a long time. In the next-generation safety injection tank equipped with a control mechanism, a passive flow rate that is mounted on the top of the injection pipe constituting the driven flow control mechanism prevents gas from leaking through the injection pipe when the flow rate is changed from the high flow rate to the low flow rate due to the water level drop. The present invention relates to a next-generation safety injection tank having a gas leak prevention device for regulating mechanism.

A general pressurized water reactor reactor is a facility that operates nuclear fuel, which is a high radioactive material, as an energy source.Therefore, there is a possibility that it can lead to a catastrophic disaster involving many casualties in the event of an accident. Every step must pass very strict safety standards.

As an example related to safety standards, the performance and safety verification of the reactor cooling system, which is conventionally employed in a PWR reactor, is performed during the design certification of the reactor and the reactor design and construction license examination by an institution such as the Korea Institute of Safety and Technology (KINS). Large Break Loss-of-Coolant Accident (LBLOCA) is an important criterion that is adopted as a criterion at the time of evaluation, due to Double Ended Guillotine Break (LBLOCA), which exhibits the highest fuel cladding temperature in the event of an accident. It is evaluated by standard. Here, the main evaluation criteria are whether the maximum fuel cladding temperature in the event of an accident is kept below the regulated value and whether the core is cooled.

In order to satisfy this criterion, the PWR reactor has an emergency core cooling water injection pipe for injecting cooling water in an emergency, and a safety injection tank connected to the emergency core cooling water injection pipe so that the low temperature pipe of the reactor normal cooling system is broken. The cooling water supplied through the low temperature pipe does not reach the core and is prepared for an accident such as an instantaneous break at both ends of the low temperature pipe discharged out of the cooling system through the break.

The general safety injection tank is for storing the coolant to be used in an emergency separately, and the coolant to be discharged through the emergency core coolant injection pipe is filled with high-pressure nitrogen to maintain the inside of the safety injection tank at a high pressure. The coolant stored in the safety injection tank is supplied to the reactor through an emergency core coolant injection pipe connected to the reactor in case of an accident where the reactor core cannot be cooled through the normal cooling system and used to cool the reactor core.

As an example according to the conventional technology improved in a general safety injection tank, in order to more efficiently use the emergency core coolant in the case of a large coolant loss accident of a nuclear power plant, a large amount of coolant is supplied at a certain period of the initial stage of the accident. In recent years, the next generation safety injection tank with a passive flow control mechanism for supplying a relatively small amount of cooling water for a long time has been developed.

As shown in FIG. 1, the driven flow rate regulating mechanism 10 is installed in a lower space inside the safety injection tank, and the emergency core coolant injection pipe 5 is connected to the center of the lower surface side and has a plurality of low water levels at the edge. Inlet pipe 15 is provided, and has a high water level inlet pipe 20 extending vertically from the upper surface side center to a predetermined height. If the driven flow rate control mechanism 10 has a high water level in the safety injection tank, the cooling water flows into the emergency core coolant injection pipe 5 through both the low water level inlet pipe 15 and the high water level inlet pipe 20. To allow a large amount of coolant to be supplied, and from the moment when the water level inside the safety injection tank is gradually lowered to reach the height of the top of the high water inlet pipe 20, only the coolant is introduced into the low water inlet pipe 15. It controls the flow rate so that a relatively small amount of coolant can be supplied.

Examples of the next-generation safety injection tank according to the prior art as described above are described in "Safety Injection System for Nuclear Reactors" in Korean Patent Application No. 2000-8774, and "Accumulator" in Japanese Patent Application Laid-open No. Hei 4-328494. It is well represented.

In order to improve the efficiency of emergency core cooling water, the next generation safety injection tank is preferably designed such that the flow rate conversion ratio defined as the ratio of the cooling water supply flow rate in the initial zone of the accident to the cooling water supply flow rate in the late zone is above a certain standard. . As a method of increasing the flow rate conversion ratio, a method of relatively reducing the total flow resistance through the high water level inlet pipe or relatively increasing the total flow resistance through the low water level inlet pipe may be used.

However, as the flow rate conversion ratio increases, the level drop width inside the high water level inlet pipe increases more at the time of the flow rate conversion, when the safety injection tank level reaches the top of the high water level inlet pipe. Therefore, as shown in Figure 1, the gas filled in the upper portion of the safety injection tank, even in the condition that the level of the coolant stored in the safety injection tank is sufficiently high, the emergency core flows through the high water inlet pipe through the low water inlet pipe It will be released early with cooling water.

The early leakage of the gas above the safety injection tank as described above has a problem that causes very large uncertainties in the analysis and prediction results of the progress of the large coolant loss accident of the reactor.

In order to solve the problems of the prior art as described above,

An object of the present invention is to provide a gas flow prevention device for the passive flow control mechanism for passively opening and closing the high water level inlet pipe in accordance with the water level so as to have a high flow rate conversion rate and at the same time to prevent the early discharge of the gas filled in the safety injection tank It is to provide a next-generation safety injection tank equipped.

1 is a schematic diagram showing a gas leakage process at the flow rate switching point of the next-generation safety injection tank according to the prior art,

Figure 2 is a schematic diagram showing a next-generation safety injection tank having a gas leakage prevention device for the driven flow rate control mechanism according to the present invention,

Figure 3 is a cross-sectional view showing a gas leak prevention device for the driven flow control mechanism mounted on the next-generation safety injection tank according to the present invention,

Figure 4 is a longitudinal cross-sectional view showing the operating principle of the next generation safety injection tank before operation or in the initial operation state according to the present invention,

Figure 5 is a longitudinal sectional view showing the principle of operation after the flow switching time of the next-generation safety injection tank according to the present invention.

* Description of the symbols for the main parts of the drawings *

5: Emergency core coolant injection pipe 10: Passive flow control mechanism

15: low water inlet 20, 20 ': high water inlet

25: flange portion 30: sealing plate guide rod

35: through hole 40: flow guide cylinder

50: sealing plate 55: guide

60: gap ring 70: flow blocking plate

75: gap 80: annular gasket

85: retaining nut 100: gas leak prevention device

The present invention for realizing this,

Next-generation emergency core cooling water inlet pipe is connected to the center of the lower surface side, is provided with a plurality of low water level inlet pipe at the edge, and a passive flow control mechanism having a high water level inlet pipe vertically extending from the upper surface side center to a predetermined height In the safety injection tank,

The high water level inlet pipe having a flange portion extending from the upper end to have a predetermined outer diameter in a horizontal direction;

A plurality of sealing plate guide rods extending vertically up to a predetermined height from a plurality of positions of the edges of the flange portion having the same center distance and equal circumferential intervals;

A plurality of through holes formed at corresponding positions in a state where a lower portion of the through hole has a radius smaller than the center distance at a central portion of the horizontal upper surface, and the center of the through hole is located on the central axis of the high water inlet pipe; A flow guide cylinder coupled to the top of the sealing plate guide rod;

It is formed with a diameter smaller than the inner diameter of the flow guide cylinder, and provided with the same number of the guide plate and the sealing plate guide rod formed at a corresponding position, and moved up and down by external force in the state constrained by the plurality of sealing plate guide rod Sealing plate made;

A plurality of gap rings respectively fitted on the plurality of sealing plate guide rods protruding to the combined flow guide cylinders; And

A center is located on the central axis of the high water level inlet pipe, and is coupled to the upper portion of the plurality of sealing plate guide rods in which the gap rings are fitted through coupling holes formed at corresponding positions, respectively, and a predetermined gap with the upper surface of the flow guide cylinder. It provides a next-generation safety injection tank having a gas leak prevention device for the passive flow control mechanism, characterized in that it comprises a gas leak prevention device comprising a; flow blocking plate for blocking direct flow through the through hole in the state maintained therein. .

In addition, the bottom of the sealing plate is installed so that its center is located on the central axis of the high water inlet pipe, characterized in that it further comprises an annular gasket which is in contact with the flange when the sealing plate is lowered.

In addition, the flow guide cylinder is characterized in that it is formed so as to have a top and bottom width so that the height of the lowest end is located below the height of the flange portion of the high water inlet pipe.

BEST MODE Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. For reference, the same reference numerals are given to the same components in all the drawings including the prior art drawings.

Gas leak prevention device 100 for the driven flow rate adjustment mechanism according to a preferred embodiment of the present invention, as shown in Figure 2, the high water level inlet pipe (10) of the driven flow rate adjustment mechanism 10 is mounted to the lower portion of the next-generation safety injection tank ( 20) If the cooling water level inside the safety injection tank is higher than the upper height of the high water level inlet pipe 20 is mounted on the upper end, the high water inlet pipe 20 is maintained in an open state so that the coolant can be emergency core coolant injection pipe (5). And the high water inlet pipe 20 is closed in the safety injection tank when the flow rate is changed to the point where the coolant level inside the safety injection tank reaches the top height of the high water inlet pipe 20. The gas is prevented from being discharged to the emergency core cooling water injection pipe 5 through the high water level inlet pipe 20.

In the passive flow control mechanism 10, as in the case of the next-generation safety injection tank according to the prior art, the emergency core cooling water injection pipe 5 is connected to the lower surface side center, and a plurality of low water level inlet pipes 15 are provided at the edges. It is provided with a high water level inlet pipe 20 extending vertically from the upper surface side center to a predetermined height.

However, as shown in Figure 3, in order to install the gas leak prevention apparatus 100 according to the present invention, the passive flow rate control mechanism 10 according to the present invention is radially horizontal at the upper end of the high water level inlet pipe 20 It is provided with a flange portion 25 extending to have a predetermined outer diameter.

Referring to FIG. 3, the gas leak prevention apparatus 100 according to the present invention includes a high water level inlet pipe 20 having a flange portion 25 as described above, and a plurality of sealing plate guide rods 30. ), The flow guide cylinder 40, the sealing plate 50, the gap ring 60 and the flow blocking plate 70.

The sealing plate guide rod 30 is fixed to the edge of the flange portion 25, and the center distances defined by the distances from the central axis of the high water level inlet pipe 20 are all the same, and the lower portions at a plurality of positions equally spaced in the circumferential direction. Is provided in a form extending in the vertical portion up to a predetermined height in a fixed state. Such a sealing plate guide rod 30 is firmly welded to the flange portion 25 of each lower end, thereby stably supporting the gas leakage preventing device 100 integrally.

The flow guide cylinder 40 is fixed to the upper end of the sealing plate guide bar 30, the through hole 35 is formed to have a radius smaller than the center distance of the sealing plate guide bar 30 in the center of the upper surface of the lower open and horizontal And a sealing plate guide rod formed at a position corresponding to the position of the sealing plate guide rod 30 in a state where the center of the through hole 35 is located on the central axis of the high water inflow pipe 20. It is coupled to the sealing plate guide rod 30 through the same number of coupling holes (30). In addition, the flow guide cylinder 40 is preferably formed so as to have a top and bottom width so that the height of the lowermost end is lower than the height of the flange portion 25 of the high water level inlet pipe (20).

The sealing plate 50 is made of a material having a lower density than water while having rigidity, such as low density polyethylene, and is formed with a diameter smaller than the inner diameter of the flow guide cylinder 40, and also the position of the sealing plate guide rod 30. And a closed plate guide rod 30 and a same number of guide holes 55 formed at a corresponding position in one-to-one correspondence with an external force in a state in which horizontal movement is constrained by a plurality of sealed plate guide rods 30. It moves up and down. Here, the guide hole 55 of the sealing plate 50 is sufficiently larger than the diameter of the sealing plate guide bar 30 so that the guide plate 55 may be smoothly raised and lowered without being caught by the sealing plate guide bar 30. It is desirable to be large.

The gap ring 60 is fitted to each of the plurality of sealing plate guide rods 30 protruding to the upper surface side of the flow guide cylinder 40 in a state where the flow guide cylinder 40 is coupled to the sealing plate guide rod 30. As it loses, it is also provided in the same number as the sealing plate guide rod 30.

In addition, the flow blocking plate 70 is made of a material having excellent corrosion resistance and high rigidity, such as stainless steel, and has a center thereof located on the central axis of the high water inlet pipe 20. Through the coupling hole formed in the position corresponding to the one-to-one position is respectively coupled to the top of the sealing plate guide rod 30 in the state where the gap ring 60 is fitted to the upper surface of the flow path guide cylinder 40 and a predetermined gap 75 It serves to block direct flow through the through hole 35 in a state of maintaining.

On the other hand, the gap ring 60 is made of a thickness of about 2mm, so that the gap 75 is formed between the upper surface of the flow guide cylinder 40 and the bottom surface of the flow blocking plate 70, the flow blocking as described above The pressure balance between the inside and the outside of the gas leakage preventing device 100 is achieved through the gap 75 formed in the state in which the direct flow through the through hole 35 of the flow guide cylinder 40 is blocked by the plate 70. To help.

As described above, the fixing nut 85 is fastened to the upper end of each sealing plate guide rod in the coupled state to the flow blocking plate 70 to firmly fix the gas leakage preventing device.

In addition to the above configuration, the gas leakage preventing device 100 according to the present invention is installed on the bottom surface of the sealing plate 50 so that its center is located on the central axis of the high water level inlet pipe 20, and the sealing plate 50 descends. It is further provided with an annular gasket (80) in contact with the flange portion (25). The annular gasket 80 is made of a material having excellent adhesion, such as silicon, and provides improved airtightness when the sealing plate 50 descends and comes into contact with the flange portion 25, thereby enabling more effective gas leakage prevention. Let's do it.

Hereinafter, the operation of the next-generation safety injection tank having the gas leakage preventing device 100 according to the present invention will be described.

As shown in Figure 4, in the pre-operational stage, the next-generation safety injection tank according to the present invention is always kept in a state filled with the appropriate amount of emergency core coolant, and also is kept in a pressurized state by being filled with compressed nitrogen in the upper portion . When the density of the sealing plate 50 is about 925kg / m 3 when the density of the sealing plate is made of low density polyethylene, it is lower than the density of the emergency core coolant stored in the safety injection tank, so the sealing plate 50 acts by the density difference in this state. As a result of the buoyancy which rises, the edge portion always remains in a position just below the flow blocking plate 70 in contact with the upper surface of the flow guide cylinder 40, thus maintaining the high water level inlet pipe 20. It keeps the flow path open.

When the operation of the safety injection tank starts, a large amount of emergency core coolant flows into the high water inlet pipe 20 in the open state along with the low water inlet pipe 15 provided in the driven flow control mechanism 10. A strong flow field from the top to the bottom is formed in the space above the inlet pipe 20. However, the direct flow blockage by the flow blocking plate 70 prevents the flow pressure caused by the flow field from being transmitted to the sealing plate 50, so that the buoyancy force still floats on the sealing plate 50 even during operation. The state is maintained and thus the flow path open state is maintained. In other words, if there is no flow blocking plate 70, the flow pressure from the top to the bottom may dissipate the buoyancy so that the closing plate 50 may descend in the initial stage of the safety injection tank to close the high water inlet pipe 20. , Through the flow blocking plate 70 will be able to solve this problem.

On the other hand, in the initial stage of operation of the safety injection tank, as shown in Figure 4, the flow guide cylinder 40 serves to change the flow direction of the emergency core coolant flowing into the high water inlet pipe 20 from the bottom up In addition, the buoyancy due to the strong flow pressure acting from the bottom up is additionally formed in the closed plate 50 together with the buoyancy due to the density difference. Therefore, until the water level of the next-generation safety injection tank reaches the top of the high water level inlet pipe 20, the sealing plate 50 is always kept floating above the high water level inlet pipe 20, the emergency inside the safety injection tank The core coolant is to be smoothly discharged through the high water inlet pipe (20).

When the level of the safety injection tank reaches the level of the sealing plate 50 that is maintained above the flow guide cylinder 40 due to the continuous injection of emergency core coolant, the water level is continuously lowered. In addition, the sealing plate 50 is also lowered by gravity.

Then, as shown in Figure 5, from the moment the water level of the safety injection tank reaches the height of the upper surface of the flange portion 25 provided in the high water inlet pipe 20, the emergency core coolant is no longer under the sealing plate (20) Since there is no buoyancy due to the difference in density disappears, the sealing plate 50 is in contact with the flange portion 25 of the high water level inlet pipe 20 and at the same time the flow path through the high water level inlet pipe 20 is further closed. Since the emergency core cooling water does not flow into the high water inflow pipe 20, the buoyancy due to the flow pressure is also eliminated.

As a result, the sealing plate 50 is lowered by the water level drop and gravity to stop at the flange portion 25 of the high water level inlet pipe 20, and in this state, the ring having excellent adhesion to the bottom surface side of the sealing plate 20 is provided. The gasket 80 is in contact with the surface of the flange portion 25 to completely close the flow path through the high water inlet pipe 20 to maintain the airtight, so that the gas of the upper part filled early through the high water inlet pipe 20 Will be completely suppressed.

Thereafter, the emergency core coolant inside the safety injection tank can be supplied to the reactor via the emergency core coolant injection pipe (5) only through the low water inlet pipe (15), which reduces the amount of cooling water supply compared to the initial accident due to the increase in flow resistance. This means that cooling water is supplied for a relatively long time, and the rate of water drop decreases.

In the above process, the gas filled in the upper portion of the safety injection tank through the gap 75 formed between the flow blocking plate 70 formed by the gap ring 60 and the upper surface of the flow path guide cylinder 40 flows into the flow path. By flowing into the guide cylinder 40, a vacuum is prevented from being formed between the sealing plate 50 and the flow blocking plate 70 positioned inside the flow guide guide cylinder 40, and at the same time, pressure balancing between the inside and the outside is prevented. As a result, the sealing plate 50 can be immediately lowered as the water level is lowered.

In addition, the sealing plate guide bar 30 in the lowering process serves to guide the lowering plate 50 to the center point of the high precision inlet pipe 20 to accurately descend.

The next-generation safety injection tank equipped with the gas leakage preventing device for the driven flow control mechanism according to the present invention as described above is purely passive by natural phenomena such as buoyancy and gravity, in order to eliminate operator intervention and increase the reliability of operation. Works.

That is, when the next-generation safety injection tank is operated due to a large loss of coolant accident at the nuclear power plant, the level of the safety injection tank is higher than the height of the upper part of the high water level inlet pipe 20 at the initial stage of operation, so that the buoyancy due to the density difference and the flow pressure is increased. As a result, the sealing plate 50 is maintained in an injured state, and thus the high water level inlet pipe 20 is kept open so that the emergency core coolant is introduced through the high water level inlet pipe 20 so that a large amount of emergency core cooling water is introduced. It can be released smoothly.

On the other hand, after the flow rate change point, which may be defined as the time when the water level of the safety injection tank reaches the height of the flange portion 25 of the high water level inlet pipe 20 due to the continuous water level drop, the sealing plate 50 is Loss of buoyancy and at the same time hermetically close the high water level inlet pipe 20 by gravity, thereby completely preventing the leakage of gas filled inside the safety injection tank through the high water level inlet pipe 20.

By providing a next-generation safety injection tank equipped with a gas leakage preventing device for the driven flow control mechanism according to the present invention as described above, even in a condition that can achieve the high flow rate conversion ratio required for emergency core coolant injection in case of accident, Early leakage of gas above the safety injection tank after flow switching can be prevented by passive methods using natural phenomena without using any active control methods. That is, the gas in the upper part of the safety injection tank leaks in advance even if the level of the coolant stored in the water is sufficiently high, which may cause a great uncertainty in the analysis and prediction results of the progress of the large coolant loss accident. It can be solved.

In addition, it provides a wider range of design variation that enables the design of a more advanced next-generation safety injection tank with a higher flow rate conversion ratio compared to the next-generation safety injection tank according to the prior art, so that a large amount of coolant loss in a nuclear power plant is caused. In this way, more efficient use of emergency core cooling water can be provided to further enhance the safety of nuclear power plants.

While the invention has been shown and described in connection with specific embodiments, it is conventional in the art that various changes, modifications and variations are possible without departing from the spirit and scope of the invention as indicated by the appended claims. Anyone with knowledge of this will easily know.

Claims (3)

Next-generation emergency core cooling water inlet pipe is connected to the center of the lower surface side, is provided with a plurality of low water level inlet pipe at the edge, and a passive flow control mechanism having a high water level inlet pipe vertically extending from the upper surface side center to a predetermined height In the safety injection tank, The high water level inlet pipe having a flange portion extending from the upper end to have a predetermined outer diameter in a horizontal direction; A plurality of sealing plate guide rods extending vertically up to a predetermined height from a plurality of positions of the edges of the flange portion having the same center distance and equal circumferential intervals; A plurality of through holes formed at corresponding positions in a state where a lower portion of the through hole has a radius smaller than the center distance at a central portion of the horizontal upper surface, and the center of the through hole is located on the central axis of the high water inlet pipe; A flow guide cylinder coupled to the top of the sealing plate guide rod; It is formed with a diameter smaller than the inner diameter of the flow guide cylinder, and provided with the same number of the guide plate and the sealing plate guide rod formed at a corresponding position, and moved up and down by external force in the state constrained by the plurality of sealing plate guide rod Sealing plate made; A plurality of gap rings respectively fitted on the plurality of sealing plate guide rods protruding to the combined flow guide cylinders; And A center is located on the central axis of the high water level inlet pipe, and is coupled to the upper portion of the plurality of sealing plate guide rods in which the gap rings are fitted through coupling holes formed at corresponding positions, respectively, and a predetermined gap with the upper surface of the flow guide cylinder. Next-generation safety injection tank with a gas leak prevention device for a passive flow control device, characterized in that it comprises a gas leak prevention device comprising a; flow blocking plate to block direct flow through the through-hole in the state. The method of claim 1, A gas leak for the driven flow regulating mechanism is further provided on the bottom of the sealing plate so that its center is positioned on the central axis of the high water level inlet pipe, and further includes an annular gasket contacting the flange part when the sealing plate is lowered. Next-generation safety injection tank with prevention device. The method of claim 1, The flow guide cylinder is a next-generation safety injection tank having a gas leakage preventing device for a driven flow rate control mechanism, characterized in that the lowermost height is formed so that the height of the lower end is located below the height of the flange portion of the high water inlet pipe when mounted. .