KR20110008950A - Emergency core cooling water safety injection tank for nuclear reactor - Google Patents

Abstract

PURPOSE: An emergency core coolant safety injection tank is provided to smoothly switch a great amount of coolant which is required for an initial state and a little amount of coolant which is required for a middle/last phase by including an opening and closing part. CONSTITUTION: A tank main body(120) stores a coolant and nitrogen gas. A flux control part(140) controls the discharging rate of the coolant. The flux control part comprises a flow controller(142) arranged in the lower side of the tank main body and a large flux amount inlet tube(144). An opening and closing part(160) are composed in order to seal the opening(144b) of the large flux amount inlet tube. The opening and closing part comprises a buoyancy water case(164) and a sealing plate(166).

Description

Emergency core cooling water safety injection tank for nuclear reactors

The present invention is an emergency core coolant safety injection tank for a nuclear reactor, and more specifically, an accident in a safety injection tank used to rapidly fill a large amount of cooling water (emergency core coolant) to a reactor vessel in the event of a large coolant loss of a PWR reactor. It relates to a safety injection tank for emergency core coolant for nuclear reactors, which converts the initial required large flow rate and the required small flow rate in the middle and second half of the accident.

A general pressurized light-water reactor is a facility that operates nuclear fuel, a high radioactive material, as an energy source, and it can be designed, constructed, and operated to secure safety as there is a possibility that it may lead to a large disaster involving many casualties in case of an accident. Each 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 adopted as a standard at the time of design certification and evaluation of reactor design and construction license. Large Break Loss-of-Coolant Accident (LBLOCA) due to Double Ended Guillotine Break (CBLOCA), which shows the highest fuel cladding temperature at the time of an accident, is considered an important criterion. 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 reactor core cooling is maintained.

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 in a certain period of the initial accident, and then In recent years, a passive flow control type safety injection tank has been developed in which a passive flow controller for supplying a relatively small amount of cooling water for a long time is installed.

As shown in FIG. 1, the driven flow controller 40 is installed in the lower space inside the safety injection tank, and the emergency core coolant discharge pipe is connected to the center of the lower surface of the safety injection tank, and the upper surface of the flow controller 40. The central portion is provided with a large flow rate inflow pipe extending vertically to a predetermined height, and the upper surface side edge is provided with a plurality of small flow rate inlets 42.

When the water level inside the safety injection tank is high, the driven flow controller 40 has a large amount of emergency because the internal cooling water flows into the emergency core coolant discharge pipe through both the low flow rate inlet 42 and the large flow rate inlet 44. The core cooling water can be supplied to the reactor core, and from the moment when the water level inside the safety injection tank gradually decreases and reaches the height of the upper end of the large flow inflow pipe, the coolant flows into the small flow rate inlet 42 only so that a relatively small amount It controls the flow rate so that the coolant can be supplied. The driven flow controller 40 has a characteristic of controlling the discharge flow rate by using a change in the vortex strength in the vortex chamber in the flow controller 40.

Examples of the driven flow-controlled safety injection tank according to the prior art as described above are "Safety Injection System to Nuclear Reactor" of Korean Patent Application No. 2000-3774, and "accumulator" of Japanese Patent Application Laid-open No. Hei 4-328494. ) "

In the driven flow rate control type safety injection tank, as shown in FIG. 2, since the water level in the large flow inlet pipe is kept lower than the level in the safety injection tank after the flow switching, even in a condition where the level of the coolant in the safety injection tank is sufficiently high. The flow path is opened because the cooling water in the flow inlet pipe is exhausted. Accordingly, the nitrogen gas filled in the upper portion of the safety injection tank is introduced into the flow controller 40 through the large flow inflow pipe and is discharged early with the emergency core coolant flowing through the small flow inflow pipe.

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

As an example of the improved prior art for preventing premature leakage of the upper portion of the safety injection tank, as shown in FIG. 3, by installing a sealing plate 66 having a lower density than water on the large flow inlet pipe, At the beginning of the safety injection tank operation, the closing plate 66 is raised by buoyancy to open the large flow inlet 84, and after the flow switching, the closing plate 66 is lowered by gravity to open the large flow inlet 84. More recently, a flow-controlled safety injection tank with a gas leak prevention mechanism for preventing gas leakage through a large flow inlet pipe has been developed.

An example of a driven flow control type safety injection tank having a gas leakage preventing mechanism according to the related art as described above is described in Korean Patent Publication No. 2005-0009401, "Next-generation safety injection tank having a gas leakage preventing device for a driven flow control mechanism." Is well represented.

As such, in order to have buoyancy in the high concentration boric acid in the safety injection tank, the specific gravity of the sealing plate 66 should be designed / manufactured to be sufficiently lower than the boric acid. Low specific gravity materials are not commonly used in nuclear power plants because they cannot guarantee sufficient material integrity such as structural strength.

Accordingly, there is uncertainty about whether the sealing plate 66 will maintain buoyancy characteristics without external deformation and material change over the life span of the nuclear power plant for 40 to 60 years.

If the safety injection tank is operated when the buoyancy characteristic of the sealing plate 66 is lost, a large amount of emergency core coolant is much smaller than required for cooling the reactor core since the large flow inlet is sealed from the beginning of the accident. Only can be supplied.

In this case, it can develop into a very fatal accident situation that cannot be compared with the uncertainty of the analysis and prediction results caused by premature leakage of gas above the safety injection tank.

Therefore, when developing a device for preventing the early leakage of the upper portion of the safety injection tank, there is a need to provide enough emergency core cooling water for cooling the reactor core even when the operation fails.

The present invention has been made to solve the above problems, it is possible to prevent the early leakage of the upper gas of the safety injection tank, and also in the case of failure of operation of the gas leakage prevention device sufficient amount of cooling water required for cooling the reactor core The objective is to provide an emergency core coolant safety injection tank for nuclear reactors supplying oil reactors.

Emergency core cooling water safety injection tank for a nuclear reactor according to a preferred embodiment of the present invention, the cooling water and nitrogen gas is accommodated, the tank having a cooling water discharge pipe 122 connected to the reactor in the lower portion in order to achieve the above object Main body 120; A flow controller 142 disposed below the tank body 120 and having a lower portion communicating with the coolant discharge pipe 122 and having a small flow rate inlet 142a formed at the upper portion thereof, and a lower portion thereof having an upper portion of the flow controller 142. A flow rate control unit 140 extending upwardly and having an upper end portion 144a bent to have a large flow rate inflow pipe 144 having the opening portion 144b directed downward, thereby controlling the discharge amount of the cooling water; And a buoyancy bucket having buoyancy for the cooling water being fastened to one end of the lever 162 installed on the large flow inflow pipe 144 and the lever 162 so that the large flow inflow pipe 144 is disposed between both ends. 164, and a sealing plate 166 coupled to the other end of the lever 162 and linked to the vertical movement of the buoyancy bucket 164 according to the cooling water, when the buoyancy bucket 164 is lowered It includes; opening and closing portion 160 is configured to seal the opening 144b of the large flow inlet pipe 144 is raised by the sealing plate 166.

At this time, the buoyancy bucket 164, the coolant inlet 164a is formed in the uppermost part from the center of rotation of the lever 162, the lower portion of the coolant in the nearest portion from the center of rotation of the lever 162 It is preferable that the outlet 164b is formed.

In addition, the present invention in order to block the falling of the closing plate 166, the fastening portion of the opening 144b of the large flow inlet pipe 144 and the lever 162 to the large flow inlet pipe 144. To be disposed between, the blocking member 180 installed in the large flow inlet pipe 144; preferably further comprises.

In addition, the buoyancy bucket 164 and the sealing plate 166 is preferably made of stainless steel.

The emergency core coolant safety injection tank for a reactor according to the present invention has an opening / closing part driven by gravity and buoyancy, so that a large amount of coolant is rapidly added to a reactor vessel in the event of a large coolant loss of a pressurized water reactor reactor. In the safety injection tank used to fill the flow rate, the large flow rate of coolant required at the beginning of the accident and the coolant flow rate of the coolant required in the middle and second half of the accident can be smoothly converted.

Here, through the configuration of the opening and closing portion, it is possible to prevent the early leakage of the upper portion of the safety injection tank.

In addition, by passively controlling and supplying the cooling water required for nuclear reactor core cooling in the event of a large coolant loss accident, the safety injection system can be simplified through more efficient use of the cooling water.

In addition, there is a great uncertainty about the interpretation and prediction of the progress of large-scale coolant loss accidents by preventing the early leakage of the upper part of the safety injection tank by the passive method using natural phenomena without using any active control method. It can solve the problem.

Furthermore, by maintaining the opening of the large flow inlet pipe even in the event of malfunction of the upper nitrogen gas pre-leak prevention device in the safety injection tank, the nuclear reactor core, which could be caused by the prior art, is seriously damaged. It has an effect that can further enhance the performance safety of the driven flow-controlled safety injection tank having a gas leakage prevention device.

The following cooling water refers to emergency core cooling water required for reactor core cooling in the event of a large coolant loss.

4 is a schematic view showing that the coolant contained in the emergency core coolant safety injection tank for a nuclear reactor according to a preferred embodiment of the present invention is discharged, Figure 5 is a view showing the upper portion of the emergency core coolant safety injection tank for the reactor of FIG. 6 is a view showing the sealing plate sealing the opening of the large flow inlet pipe in the emergency core coolant safety injection tank for the reactor of Figure 4, Figure 7 is a buoyancy bucket in the emergency core coolant safety injection tank for the reactor of Figure 4 It is a figure which shows that the opening part of a large flow inflow pipe is reopened with water level fall.

Referring to the drawings, the emergency core cooling water safety injection tank for the reactor of the present invention is a tank main body 120, the flow control unit 140 for controlling the flow rate of the tank body 120, the flow control unit 140, the coolant is accommodated It includes an opening and closing unit 160 for opening and closing the large flow inlet pipe (144).

The tank body 120 has a cooling water is accommodated therein, the nitrogen gas having a suitable pressure is filled in the upper portion outside the space in which the cooling water is accommodated.

In addition, the tank body 120 has a cooling water discharge pipe 122 connected to the reactor at the bottom.

The coolant of the tank body 120 is discharged through the coolant discharge pipe 122 in the reactor in an emergency, and the nitrogen gas serves to maintain an appropriate pressure for the discharge of the coolant.

The flow controller 140 includes a flow controller 142 disposed in the tank body 120 and a large flow inflow pipe 144 coupled to the upper portion of the flow controller 142.

The flow controller 142 is disposed on the lower side in the tank body 120, the lower portion is connected to the cooling water discharge pipe 122 forms a structure.

In addition, the flow rate controller 142 has a low flow rate inlet 142a formed at an upper portion thereof, and when the coolant level in the tank body 120 falls below the opening 144b of the large flow inlet pipe 144, the low flow rate inlet ( It is introduced into the interior through only 142a, the introduced cooling water is discharged through the cooling water discharge pipe 122.

The flow rate control unit 140 configured as described above functions to adjust the discharge amount of the cooling water.

On the other hand, the opening and closing portion 160 is provided with a lever 162 installed in the large flow inlet pipe 144, and a buoyancy bucket 164 and a sealing plate 166 mounted to both ends of the lever 162, respectively.

The lever 162 is configured in the large flow inlet pipe 144 so that the large flow inflow pipe 144 is disposed between both ends.

That is, the lever 162 is fixed to the large flow inlet pipe 144 vertically disposed on the flow controller 142 of the flow control unit 140 so as to be rotatable, and both ends are interposed between the large flow inflow pipe 144. It can be configured so that the position of the buoyancy bucket 164 and the sealing plate 166 on each side can be maintained.

In addition, the buoyancy bucket 164 is fastened to one end of the lever 162 has a certain degree of buoyancy with respect to the cooling water.

In the buoyancy bucket 164 as described above, a coolant inlet 164a is formed at a part farthest from the center of rotation of the lever 162, and a coolant outlet 164b is located at a part closest to the center of rotation of the lever 162 at the bottom. ) Is formed.

Accordingly, the cooling water of the tank body 120 is introduced into the buoyancy bucket 164 through the cooling water inlet 164a, and flows out of the buoyancy bucket 164 through the cooling water outlet 164b. The cooling water outlet 164b of the present invention has a small diameter suitable so that the cooling water inside the buoyancy bucket 164 is gradually discharged.

In addition, the coolant inlet 164a and the coolant outlet 164b allow the buoyancy bucket 164 to communicate with the outside so that the pressure inside / outside the buoyancy bucket 164 is the same, thereby preventing the deformation of the buoyancy bucket 164. do.

The sealing plate 166 is fastened to the other end of the lever 162 is configured to interlock with the vertical movement of the buoyancy bucket 164 according to the cooling water.

Here, the sealing plate 166 is raised upward by the buoyancy bucket 164 at one end as the lever 162 rotates around the position where the lever 162 is fastened to the large flow rate inlet pipe 144, and thus the large flow rate inflow pipe ( It is configured to seal the opening 144b of 144.

The buoyancy bucket 164 and the sealing plate 166 of the opening and closing portion 160 is configured as described above so that the load is greater than the sealing plate 166 when the inside of the buoyancy bucket 164 is filled with cooling water. In addition, it is preferable that the load of the sealing plate 166 is 130% or more.

In addition, the buoyancy bucket 164, when the coolant level in the tank body 120 is above the buoyancy bucket 164 and the sealing plate 166 and the coolant is filled in the buoyancy bucket 164, buoyancy is sealed plate 166 The thickness and volume are configured to be greater than the buoyancy of At this time, the net load of the buoyancy bucket 164 is preferably less than 50% of the net load of the sealing plate 166.

In addition, the buoyancy bucket 164 and the sealing plate 166, the center of rotation of the lever 162, that is, at both sides of the fastening portion of the lever 162 to the large flow inlet pipe 144 so that the above conditions are satisfied. It may be appropriately positioned along the lever 162.

When the buoyancy bucket 164 and the sealing plate 166 configured as described above are located in the cooling water, that is, the buoyancy bucket 164 is filled with the cooling water, and the cooling water level is the buoyancy bucket 164 and the sealing plate 166. In the higher case, since the sealing plate 166 has a larger net load than the buoyancy bucket 164 in the cooling water, as the sealing plate 166 descends, the opening 144b of the large flow inlet pipe 144 opens. Stay intact.

When the buoyancy bucket 164 and the sealing plate 166 is located above the cooling water level because the cooling water level is lowered in the above state, since the sealing plate 166 has a smaller load than the buoyancy bucket 164 filled with the cooling water, The buoyancy bucket 164 descends and the sealing plate 166 rises to seal the opening 144b of the large flow inflow pipe 144.

At this time, the opening 144b and the sealing plate 166 of the large flow inlet pipe 144 may prevent nitrogen gas in the tank body 120 from flowing into the opening 144b of the large flow inlet pipe 144. Of course, the opening plate 144b is completely sealed by the sealing plate 166.

Thereafter, as the cooling water in the buoyancy bucket 164 is drained, the sealing plate 166 is lowered again when the load of the buoyancy bucket 164 becomes smaller than the load of the sealing plate 166.

At this time, the buoyancy bucket 164, the load of the buoyancy bucket 164 to maintain the state larger than the load of the seal for a period of time longer than about 150 seconds, which is the estimated low-capacity operation time of the safety injection tank closed plate during the low-flow operation period In order to prevent 166 from falling, the size of the cooling water outlet 164b is preferably formed as an appropriate size.

The lowering of the sealing plate 166 prevents the sealing plate 166 from closing the opening 144b of the large flow rate inlet pipe 144 for a long time, thereby preventing the sealing plate 166 from opening the opening 144b. Prevent it from sticking.

In addition, the present invention further includes a blocking member 180 to block the lowering of the sealing plate 166.

The blocking member 180 is disposed between the opening 144b of the large flow inlet pipe 144 and the fastening portion of the lever 162 with respect to the large flow inlet pipe 144. Is installed.

Such a blocking member 180 blocks the lowering of the closing plate 166 at a certain level, which is the closing plate 166 is rotated down to position the buoyancy bucket 164 beyond the large flow inlet pipe 144. Prevents rotational movement to the side.

On the other hand, the buoyancy bucket 164 and the sealing plate 166 of the present invention is preferably made of stainless steel, the inner diameter, height, wall thickness of the buoyancy bucket 164 is 600mm, 500mm, 5mm, the sealing plate 166 ), The diameter and thickness are preferably 500 mm and 60 mm.

In this case, the loads of the buoyancy bucket 164 and the sealing plate 166 submerged in the coolant are about 43 kgf and 110 kgf, respectively, and the load in the nitrogen gas where the buoyancy is lost due to the coolant level gradually decreases, respectively, about 187 kgf and 125 kgf, respectively. Becomes Furthermore, when the cooling water in the buoyancy bucket 164 is drained by about 45% under a nitrogen gas environment, the loads of the buoyancy bucket 164 and the sealing plate 166 become equal.

In addition, the length of the lever 162 is preferably about 1100mm, the material is preferably stainless steel excellent in rigidity and corrosion characteristics.

Furthermore, the support structure for the rotation center axis of the lever 162 is fixed to the large flow inflow pipe 144 and the inner wall of the tank main body 120 to sufficiently endure the load of the buoyancy bucket 164 and the sealing plate 166. do.

Let us look at the operation sequence of the emergency core coolant safety injection tank for a reactor of the present invention configured as described above.

First, before the safety injection tank is operated, the cooling water level is higher than the height of the large flow inflow pipe 144, and the inside of the buoyancy bucket 164 is filled with the cooling water.

Although the load of the buoyancy bucket 164 in the full water level is greater than the load of the sealing plate 166, the buoyancy bucket 164 submerged in the coolant receives a buoyancy greater than that of the sealing plate 166, thereby providing a net of the buoyancy bucket 164. The load is smaller than the closing plate 166. Accordingly, the buoyancy bucket 164 is raised and the sealing plate 166 is lowered so that the opening 144b of the large flow inflow pipe 144 is kept open.

When the safety injection tank is operated, the level of the coolant gradually decreases to reach the upper portion of the buoyancy bucket 164. After this, the buoyancy received by the buoyancy bucket 164 decreases, so that the increase in the net load of the buoyancy bucket 164 is greater than the increase in the net load of the sealing plate 166, so that the water level decreases so that the buoyancy is completely lost. The buoyancy bucket 164 is lowered and the sealing plate 166 is raised.

Therefore, the opening 144b of the large flow inflow pipe 144 is sealed by the sealing plate 166 to prevent premature leakage of the upper nitrogen gas in the safety injection tank.

Thereafter, as time passes, the coolant in the buoyancy bucket 164 is gradually discharged through the coolant outlet 164b so that the total load of the buoyancy bucket 164 is reduced, and the load of the buoyancy bucket 164 is closed plate 166. At the time of becoming smaller, the sealing plate 166 is lowered again.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

1 and 2 is a schematic view showing that the cooling water contained in the driven flow rate safety injection tank according to the prior art is discharged.

3 is a view showing the operating principle of the sealing plate for the large flow inlet of the safety injection tank having a conventional gas leakage prevention device.

4 is a schematic view showing that the cooling water contained in the emergency core coolant safety injection tank for a nuclear reactor according to a preferred embodiment of the present invention is discharged.

FIG. 5 is a view illustrating an upper portion of the emergency core coolant safety injection tank for the reactor of FIG. 4.

6 is a view showing that the sealing plate seals the opening of the large flow inlet pipe in the emergency core cooling water safety injection tank for the reactor of FIG.

7 is a view showing that the opening of the large flow inlet pipe is reopened in accordance with the water level decrease in the buoyancy bucket in the emergency core cooling water safety injection tank for the reactor of FIG.

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

120: tank body 122: cooling water discharge pipe

140: flow control unit 142: flow controller

142a: small flow inlet 144: large flow inlet pipe

144a: upper portion 144b: opening

160: opening and closing part 162: lever

164: buoyancy bucket 164a: cooling water inlet

164b: cooling water outlet 166: airtight plate

180: blocking member

Claims (4)

Cooling water and nitrogen gas is accommodated, the tank body 120 having a cooling water discharge pipe 122 connected to the reactor in the lower portion; A flow controller 142 disposed below the tank body 120 and having a lower portion communicating with the coolant discharge pipe 122 and having a small flow rate inlet 142a formed at the upper portion thereof, and a lower portion thereof having an upper portion of the flow controller 142. A flow rate control unit 140 extending upwardly and having an upper end portion 144a bent to have a large flow rate inflow pipe 144 having the opening portion 144b directed downward, thereby controlling the discharge amount of the cooling water; And A buoyancy bucket having buoyancy for the cooling water is fastened to one end of the lever 162 installed on the large flow inlet pipe 144, the lever 162 so that the large flow inflow pipe 144 is disposed between both ends ( 164, and a sealing plate 166 coupled to the other end of the lever 162 and linked to the vertical movement of the buoyancy bucket 164 according to the cooling water, when the buoyancy bucket 164 is lowered An opening and closing unit 160 configured to lift the sealing plate 166 to seal the opening 144b of the large flow inflow pipe 144; Emergency core coolant safety injection tank for a reactor comprising a. The method of claim 1, The buoyancy bucket 164, Cooling water inlet 164a is formed in the uppermost part from the center of rotation of the lever 162, the cooling water outlet 164b is formed in the closest portion from the center of rotation of the lever 162 Emergency core coolant safety injection tank for nuclear reactor. The method according to claim 1 or 2, In order to block the lowering of the closing plate 166, it is arranged between the opening 144b of the large flow inlet pipe 144 and the fastening portion of the lever 162 to the large flow inlet pipe 144, Blocking member 180 is installed in the large flow inlet pipe (144); Emergency core cooling water safety injection tank for a reactor further comprising. The method according to claim 1 or 2, The buoyancy bucket 164 and the sealing plate 166 is a safety core injection tank emergency reactor coolant water, characterized in that the material is stainless steel.

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