KR20170017699A - Passive cooling system of nuclear power plant using phase change material - Google Patents

Abstract

The present invention relates to a passive cooling system of a nuclear power plant using a phase change material, which includes: a pipe which includes an inlet part communicating with the inside of an object to be cooled, and a discharge part communicating with the outside, accommodates coolant inside/outside and transfers the coolant; an internal heat exchanger connected to a pipe provided inside the object to be cooled; and an external heat exchanger connected to a pipe provided outside the object to be cooled. The coolant is introduced into the object to be cooled through the inlet part, and is discharged to the outside of the object to be cooled through the outlet part, so the coolant circulates along the pipe inside and outside the object to be cooled and discharges the internal heat of the object to be cooled to the outside.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a passive cooling system for a nuclear power plant,

The present invention relates to a method for cooling an atmosphere or a fluid in a nuclear power plant such as buildings (containment buildings, spent nuclear fuel storage tanks) and equipment (reactor coolant system, driven auxiliary water supply, To a passive cooling system for securing safety of a nuclear power plant.

More specifically, a large amount of energy is generated at the time of a nuclear power plant accident / accident, and the objects such as buildings and equipment to be cooled for the safety of a nuclear power plant are converted into phase-change materials It is possible to maintain the integrity of the cooling object by effectively reducing the pressure and the temperature rise by passively, and by cooling the fluid in the system to continuously perform the function, it is possible to improve the safety of the nuclear power plant by using the phase change material And more particularly, to a passive cooling system for a nuclear power plant.

The autoclave coolant system functions to cool the core containing the fuel and to keep the core in a safe state from the viewpoint of safety.

On the other hand, if core cooling can not be performed smoothly in the event of nuclear power plant accident / accident, cooling function of core and reactor coolant system is very important for nuclear power plant safety because nuclear fuel cladding material is exposed and can be expanded to serious accident where core is melted.

The system for cooling the core and reactor coolant system includes a safety injection / stop cooling system for directly cooling the coolant into the reactor coolant system, and a cooler for cooling the core and the reactor coolant system indirectly by injecting an auxiliary coolant into the steam generator. And an auxiliary water supply system is provided.

In addition, the containment building contains reactor core, reactor coolant system and safety related systems / equipment inside, and reinforced concrete outer wall in the form of a cylinder and a round dome combined.

Here, 'containment' means to protect reactor core, reactor coolant system and safety related systems / devices from external impact, and to prevent leakage or leakage of radioactive material generated inside containment building in case of nuclear power plant incident / accident It is used as a means of blocking and it is the last barrier to prevent the leakage of radioactive material in the event of an accident / accident at a nuclear power plant.

Such a containment structure performs the above function, but if a serious accident occurs in which the nuclear core is melted due to the exposure of the fuel, and the integrity of the containment building is damaged, a large amount of radioactive material may leak outside the containment building and cause extreme damage.

Therefore, securing the integrity of containment buildings is very important for the safety of nuclear power plants.

In order to prevent the melting of the core and the integrity of the containment building in case of an incident / accident, the nuclear power plant is required to maintain a safety reactor coolant pressure meter Through the automatic operation of the interlocked safety injection system, the boric acid water flows into the reactor coolant system, and the containment building water spray system linked with the safety related containment building pressure meter is automatically operated to condense the steam inside the containment building, It is necessary to secure the integrity of the containment building by reducing the temperature and the temperature below the designed value and then to ensure the continuous cooling of the static cooling system and the containment building water spray system so that the core melting and the integrity of the containment building can be secured continuously.

In this case, if the amount of the intake water such as boric acid water flowing into the reactor coolant system is enough to cause natural circulation, the operation of the auxiliary water supply system can remove the heat of the core and the reactor coolant system through the steam generator, The level monitoring of the steam generator should also be maintained for the purpose.

However, if the volume of the reactor coolant system is not sufficient enough to cause natural circulation within the system, or if the water level monitoring function of the steam generator is lost or the water in the auxiliary water tank is exhausted, heat removal through the steam generator can be performed There is no limit.

In addition, the safety injection / stop cooling system and the containment building sprinkler system are designed to automatically operate the pumps and the automatic actuating valves and active devices connected to the safety related measurement devices, Is designed so that the manual operation can be performed by the action of the operator (operation of the hand number position).

Therefore, the supply of power is essential for the operation of these systems, the heat generated inside the containment building is transferred to the equipment cooling system through the stationary cooling / sprinkling heat exchanger, and the transferred heat is transferred to the equipment cooling seawater system through the equipment cooling water heat exchanger And the heat inside the transferred containment building is discharged through the equipment cooling seawater system to the sea where the final heat is removed.

In addition, the spent nuclear fuel stored in the repository of the nuclear power plant is continuously generated by the heat exchanger and the pump because the decay heat of the nuclear fuel product is continuously generated, and the decay heat transferred through the heat exchanger is the heat Lt; / RTI >

However, if the function of the equipment cooling system is lost due to the occurrence of a tsunami such as Fukushima, or the equipment cooling system is lost due to an accident such as an aircraft collision, etc., There is a problem in that the cooling function can not be performed since the heat can not be discharged through the quiescent cooling / sprinkling heat exchanger and the equipment cooling water heat exchanger and the decay heat of the nuclear fuel storage vessel can not be discharged to the sea of the final heat removal through the storage tank cooling heat exchanger .

In addition, since the systems include a plurality of active devices that require power supply, there is a problem that the storage building cooling function can not be performed even if an accidental loss such as an extraneous power loss or a complete power loss occurs.

For example, an accident at a nuclear power plant in Fukushima corresponds to a complete loss of power source accompanied by a loss of the final heat removal source.

An example of cooling the containment building is disclosed in Korean Patent Registration No. 10-1517449, which discloses a liquid metal impregnation system for cooling an outer wall of a reactor vessel.

FIG. 1 is a schematic view showing the construction of a conventional liquid metal impregnation system for cooling an outer wall of a reactor vessel, which comprises: a reactor vessel containing a core melt; A first reactor cavity (110) in which the first reactor cavity (110) is filled with liquid metal (111) circulating and supplied to the outer wall in contact with the outer wall; A second reactor cavity 120 disposed in a space surrounded by the partition walls of the first reactor cavity 110 and spaced apart from the partition walls of the first reactor cavity 110 and having cooling water 121 circulated therein in contact with the partition wall; And one side is disposed inside the first reactor cavity (110) and the other side is disposed inside the second reactor cavity (120), and one side and the other side are inserted into the first reactor cavity And a first heat pipe 130 provided in a communicated closed circuit structure for transferring the heat of the heated liquid metal 111 to the cooling water 121. The first heat pipe 130 is connected to the one- 110, and a portion disposed inside the second reactor cavity 120 are folded a plurality of times or a plurality of projections are protruded.

This conventional liquid metal impregnation system for reactor wall outer wall cooling uses thermal conductivity of the coolant made of the liquid metal 111 for cooling the outer wall of the reactor vessel to improve thermal stability, The heated heat of the liquid metal 111 introduced into the first reactor cavity 110 by the first heat pipe 130 arranged to span the interior of the second reactor cavity 120 And is transferred to the enclosed cooling water 121 so that the heated heat of the reactor vessel is cooled.

However, the above-described prior art generally requires a bulky first reactor cavity 110 and a second reactor cavity 110 to be accommodated therein so that the reactor vessel can be accommodated outside a reactor vessel having a two or three- It is necessary to provide the second reactor cavity 120 having a large volume to accommodate the containment structure, thereby occupying a large volume and increasing construction costs.

It is also positive that the liquid metal reservoir 112 is located above the reactor vessel so that the liquid metal 111 is provided to the interior of the first reactor cavity 110 by gravity, There is a problem that the liquid metal reservoir 112 needs to be installed at a higher volume than the reactor vessel having a size of a few layers of the building.

In addition, it is positively possible to operate the system even in the event of a loss of power in the power plant by adopting the gravity-type plugging system. However, when the liquid metal 112 stored in the liquid metal reservoir 112 is in a liquid state A separate heating device is provided in the liquid metal reservoir 112 to keep the heating device, and a separate power source is required to maintain the continuous operation of the heating device.

In addition, during the accident / accident of a nuclear power plant, a device for preventing the heating of the water entering the containment building by the fluid inside the reactor coolant system and the safety injection / sprinkler system is required and in the long term, the liquid metal application system for cooling the outer wall of the reactor vessel is continuously used There is a problem that the containment building integrity can not be guaranteed because the containment building temperature reaches 600 ° C.

Patent Registration No. 10-1517449 (April 28, 2015) Published Japanese Patent Application No. 10-2014-0000411 (Apr.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a power plant capable of generating a large amount of energy at the time of a nuclear power plant accident / accident, The use of phase change materials without the use of active equipment such as measuring equipment to monitor the condition of the safety system and the prevention of the loss of function of the safety system and the threat of building integrity, By effectively reducing the pressure and temperature rise of the cooling object by using passively, it is possible to maintain the soundness of the cooling object and to cool the fluid in the system to continuously maintain the function of the related system. Thus, the phase change material To provide a passive cooling system for a nuclear power plant.

In order to solve the above problems, the passive cooling system for a nuclear power plant using the phase-change material according to the present invention includes an inlet portion communicating with the inside of a cooling object and a discharge portion communicating with the outside, Piping; An internal heat exchanger connected to a pipe provided inside the cooling object; And an external heat exchanger connected to a pipe provided outside the object to be cooled. The coolant is introduced into the object to be cooled through the inlet portion and discharged to the outside of the object to be cooled through the outlet portion, And the heat of the inside of the cooling object is discharged to the outside while circulating the cooling water to the outside of the cooling object, thereby solving the technical problem.

The present invention has a remarkable effect that the heat inside the cooling object can be passively removed by using the phase change material.

Further, the present invention has a remarkable effect that the external atmosphere of the object to be cooled is used as the final heat eliminating source, so that it is possible to cool without external power without requiring separate operator measures such as supply of electricity or cooling water.

Further, according to the present invention, the cooling system fluid containing the phase-change material circulates in a natural convection flow by a remarkable density difference between phases generated at the time of phase conversion in the temperature range of the inside / outside of the cooling object, And has a remarkable effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing the configuration of a conventional liquid metal impregnation system for cooling an outer wall of a reactor vessel.
2 is a schematic view of a nuclear power plant passive cooling system using a phase change material according to the present invention.
FIG. 3 is a view showing an example in which the heat is raised in accordance with the temperature rise inside the cooling object in the passive cooling system of a nuclear power plant using the phase-change material according to the present invention.
FIG. 4 is a view illustrating an example in which a phase-change material in a solid state in a passive cooling system of a nuclear power plant using a phase-change material according to the present invention absorbs heat inside a cooling object in a liquid state and is discharged to the outside.

Advantages and features of embodiments of the present invention and methods of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

The present invention relates to an apparatus and a method for monitoring a state of a power plant which may be caused by a temperature increase and a pressure increase inside a cooling target as a large amount of energy generated during a nuclear power plant accident / In order to prevent the malfunction of the cooling object and the soundness of the cooling object in advance, it is necessary to use a phase change material to passively control the cooling object It is possible to effectively reduce the rise of pressure and temperature, to maintain the integrity of the building to be cooled, to cool the fluid in the system, and to continuously ensure the function of the related system. Therefore, the phase change material And more particularly, to a passive cooling system for a nuclear power plant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a passive cooling system for a nuclear power plant using a phase change material according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a schematic view of a nuclear power plant passive cooling system using a phase change material according to the present invention.

First, in the present specification, the cooling object 10 means a containment building, a nuclear fuel storage tank, a reactor coolant system, a driven auxiliary water supply or a driven auxiliary water supply tank provided in a nuclear power plant. In order to secure the safety of a nuclear power plant, Means a building or equipment that requires a function.

The passive cooling system of a nuclear power plant using the phase change material according to the present invention is a system in which the energy flowing into the cooling object 10 at the time of occurrence of an incident or accident of a nuclear power plant is discharged to the outside, (20), an internal heat exchanger (30), and an external heat exchanger (40) to prevent the loss of function of the safety system and the soundness of the building in advance. do.

2, the piping 20 includes an inlet 21 communicating with the interior of the object to be cooled 10 and an outlet 22 communicating with the outside, A part of the pipe 20 is provided inside the object to be cooled 10 and the other part is provided outside the object 10 to be cooled through the part 22 so that the pipe 20 is arranged inside the object to be cooled 10 And can communicate with the outside.

At this time, the inlet portion 21 is preferably installed at a position lower than the discharge portion 22 with respect to the cooling object 10 installed on the ground.

The coolant accommodated in the piping 20 is drawn into the cooling object 10 through the inlet 21 and is transferred to the internal heat exchanger 30 of the cooling object 10 to be cooled The heat generated in the cooling object 10 is transferred to the outside of the cooling object 10 through the discharge portion 22 and the energy inside the cooling object 10 is discharged to the outside atmosphere through the external heat exchanger 40 .

At this time, the pipe 20 is excellent in corrosion resistance, so it does not rust easily, and it has high durability and is not bent or crushed easily, has high abrasion resistance, excellent in low temperature characteristics, and has high fire resistance and heat resistance. And can be made of a material having high oxidation resistance and excellent workability and economy.

Depending on the design conditions, the pipe 20 may be made of stainless steel.

At this time, the coolant accommodated in the pipe is transferred to the inside of the cooling object 10 through the inlet portion 21, and the heat inside the cooling object 10 is taken away And is transferred to the outside of the cooling object 10 through the discharge part 22 to discharge the taken-out heat.

The coolant is a mixture of water and phase change materials.

The phase change material has a phase transformation temperature that is higher than the temperature of the object to be cooled 10 during the normal operation of the reactor and has a phase transformation temperature lower than the maximum temperature of the object 10 during occurrence of an event / accident and is stably mixed with water, The density of phases during phase transformation is large so that natural convection circulation can be actively performed, and the phase change latent heat can be made of a material having a high phase conversion so that the internal energy of the cooling object 10 per unit volume can be absorbed.

Depending on the design conditions, it may be made of various phase change materials in consideration of the individual requirements of the nuclear power plant and the characteristics of the power plant.

The phase change material absorbs the heat inside the cooling object 10 during the phase transition from the solid state to the liquid state and releases heat to the outside of the cooling object 10 during the phase conversion from the solid state to the liquid state.

That is, the coolant mixed with water and the phase change material is received in the pipe 20, is drawn into the cooling object 10 through the inlet 21, The cooling object 10 is discharged to the outside of the cooling object 10 through the discharge part 22 of the cooling object 10 and is conveyed to the inlet part 21 again along the pipe 20 provided outside the cooling object 10 to be circulated.

Further, the phase-change material is stably mixed with water, so that the phase-change material is smoothly conveyed even in a solid state.

For example, the phase change material may comprise SODIUM ACETATE TRIHYDRATE (CH ₃ CO ₂ Na ₃ H ₂ O).

SODIUM ACETATE TRIHYDRATE (CH ₃ CO ₂ Na ₃ H ₂ O) is a chemical name for sodium acetate trihydrate with a melting point of 58 ° C, a latent heat of 264 kJ / kg during phase conversion, a density of 1.45 kg / dm ³ , and specific heat is 2.79 kJ / kgK.

At this time, the coolant may be composed of 70 to 200 parts by weight of phase change material with respect to 100 parts by weight of water.

If the phase change material is less than 70 parts by weight (minimum weight part) based on 100 parts by weight of water, the degree of absorbing the heat inside the cooling object 10 is insignificant, When the phase change material exceeds 200 parts by weight (maximum weight portion) with respect to the part, the phase change material, which is a solid state at the time of phase transformation, is contained in the pipe 20 in proportion to water,

Therefore, in the passive cooling system for a nuclear power plant using the phase change material according to the present invention, the coolant made of water and phase change material is conveyed along the pipe 20 and is conveyed to the inside of the cooling object 10 through the inlet portion 21 The coolant is phase-transformed from the solid state to the liquid state in the internal heat exchanger 30 by the high-temperature heat inside the object 10 to be cooled, thereby absorbing the heat inside the object 10 to be absorbed. At this time, the coolant rises along the pipe 20 due to the buoyant force due to the remarkable density difference between the phases generated due to the phase change of the phase change material in the internal heat exchanger 30, and the flow due to the natural convection caused by the density difference .

The mixture of the phase change material and the water that has been phase-converted into the liquid state is discharged to the outside of the cooling object 10 through the discharge portion 22 while absorbing the heat and is transferred along the pipe 20 to the outside heat exchanger 40, The phase change material is phase-transformed from the liquid state to the solid state, coagulates and releases heat to the atmosphere, and the phase transition from the liquid state to the solid state causes a remarkable difference in density between the phases to occur again to accelerate the convection of the coolant, The coolant circulation speed is significantly increased.

The coolant, in which the phase-transformed solid phase-change material and the water are mixed while releasing heat, is conveyed along the pipe 20 and is conveyed again to the inlet portion 21 by natural convection circulation.

Through this process, the heat inside the cooling object 10 can be passively removed by using the phase-change material, the cooling function can be performed for a long period without any time limitation by natural convection, By utilizing the outside atmosphere of the object 10, there is an advantage that no operator action is required, such as the supply of electricity or cooling water, so that cooling can be performed without external power.

On the other hand, check valves 51 and 52 are provided on portions of the pipe 20 where the inlet 21 and discharge 22 are provided, respectively, outside the cooling object 10 .

The check valves 51 and 52 are valves that allow the fluid to flow only in one direction and not to flow in the opposite direction. The coolant contained in the pipe 20 circulates through the inlet 21 and the outlet 22 sequentially So that it can flow in one direction.

However, it is needless to say that the installation of the check valves 51 and 52 can be carried out only when necessary, since it may interfere with the flow of the coolant flowing passively.

Depending on the design conditions, a buffer tank 60 connected to the pipe 20 may be provided.

The buffer tank 60 is connected to one side or the other side of the pipe 20 so that the coolant accommodates the volume change generated during the phase change process and prevents impurities from flowing into the system. Further, when the pressure or the flow rate of the coolant accommodated in the piping 20 is changed suddenly, the function is performed so that it does not affect the other side or one side of the opposite side to which the buffer tank 60 is not provided.

At this time, the buffer tank 60 may further include a relief valve 61 and an air valve 62.

The relief valve 61 can prevent the systematic pressure from exceeding the design pressure by causing the fluid in the system to be ejected to the outside when the pressure inside the piping 20 and the buffer tank 60 becomes a predetermined pressure or more, To maintain the soundness of.

The air valve 62 allows the outside air to flow into the buffer tank 60 and the pipe 20, thereby preventing the negative pressure inside the system.

It goes without saying that, according to the design conditions, the gas discharge and the air inflow by the buffer tank 60 may be configured to check the pressure inside the pipe 20 and operate passively by the checked pressure value.

Accordingly, even when expansion or contraction occurs due to a phase change of the coolant conveyed along the pipe 20 to a liquid state, a solid state, or a gaseous state, a constant pressure can be maintained, So that cooling can be smoothly performed.

According to this configuration, the passive cooling system of the nuclear power plant using the phase-change material according to the present invention has an advantage that the heat inside the cooling object 10 can be passively removed by using the phase-change material.

Further, by using the external atmosphere of the cooling object 10 as a final heat removal source, it is possible to perform cooling without external power without requiring separate operation measures such as supply of electricity or cooling water.

Further, the coolant mixed with the water and the phase change material is circulated by the natural convection, so that the smooth transfer can be performed, and furthermore, the cooling can be performed for a long time without any time limit.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It can be seen that branch substitution, modification and modification are possible.

10: cooling object 20: piping
21: inlet 22: outlet
30: internal heat exchanger 40: external heat exchanger
51, 52: Check valve 60: Buffer tank
61: relief valve 62: air valve

Claims (9)

A pipe 20 including an inlet 21 communicating with the inside of the cooling object 10 and a discharge portion 22 communicating with the outside and having a coolant accommodated therein and being transported;
An internal heat exchanger (30) connected to a pipe (20) provided inside the cooling object (10); And
And an external heat exchanger (40) connected to a pipe (20) provided outside the object to be cooled (10)
The coolant
Is drawn into the cooling object 10 through the inlet portion 21 and discharged to the outside of the cooling object 10 through the discharge portion 22 so that the inside and the outside of the cooling object 10 , And the heat inside the cooling object (10) is discharged to the outside while being circulated to the cooling object (10).
The method according to claim 1,
The coolant
A passive cooling system for a nuclear power plant using a phase change material, characterized in that a solvent and a phase change material are mixed.
The method of claim 2,
Wherein the solvent is water,
The coolant
And 70 to 200 parts by weight of a phase change material based on 100 parts by weight of water.
The method of claim 2,
The phase-
(10) when the reactor is in a normal operation state and has a low phase transformation temperature at the maximum temperature of the object to be cooled (10) at the time of an event / accident and is stably mixed with water, And a phase change latent heat is high so that the internal energy of the cooling object (10) per unit volume can be absorbed. The passive cooling system of the nuclear power plant using the phase change material.
The method of claim 4,
The phase-
SODIUM ACETATE TRIHYDRATE (CH ₃ CO ₂ Na ₃ H ₂ O).
The method according to claim 1,
The pipe (20)
A check valve 51 for allowing a coolant to be conveyed along a pipe 20 provided outside the cooling object 10 to be drawn into the cooling object 10 through the inlet 21; And
And a check valve 52 for allowing the coolant to be conveyed along the pipe 20 provided in the cooling object 10 to be conveyed along the pipe 20 provided outside the cooling object 10 Characteristics of Passive Cooling System of Nuclear Power Plant Using Phase Change Materials.
The method according to claim 1,
A buffer tank 60 is further provided at a portion of the path of the pipe 20 where the discharge portion 22 is provided,
The buffer tank (60)
A relief valve (61) for discharging the gas inside the cooling object (10) to the outside; And
And an air valve (62) for allowing outside air to be drawn in. The passive cooling system of a nuclear power plant using the phase change material.
The method according to claim 1,
The pipe (20)
It has excellent resistance to corrosion and is resistant to rust. It has high durability. It does not bend or squeeze easily. It has high abrasion resistance, excellent low temperature characteristics, high fire resistance and heat resistance, can maintain strength even at high temperature, Wherein the phase change material is made of an excellent material.
The method of claim 8,
The pipe (20)
A passive cooling system for a nuclear power plant using a phase change material, characterized in that it is made of stainless steel.

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