KR20130130994A - Nuclear reactor cooling system for emergency - Google Patents

Abstract

A nuclear reactor cooling system of a nuclear power generating facility includes an emergency core cooling system (ECCS) which performs a cooling operation by supplying cooling water to a nuclear reactor in an emergency and a solar hot water cooling unit which cools the nuclear reactor by supplying hot water heated by solar energy to the nuclear reactor in the emergency after a pressurizing process. [Reference numerals] (AA) Cool water

Description

Nuclear Reactor Cooling System For Emergency

The present invention relates to an emergency reactor cooling system, and more particularly, to a reactor cooling system capable of gradually cooling the reactor by supplying hot water heated by solar heat after pressurization to the reactor in emergency.

The core installed in the nuclear power plant is the center of the reactor, where the nuclear nucleus of uranium used as nuclear fuel in the core collides with neutrons, causing nuclear fission and energy is released, thereby heating the reactor coolant. High temperature treatment of the concentrated uranium powder to form a cigarette filter is a pellet used as a nuclear fuel in nuclear power plants. Fuel pellets are stacked in long cylindrical pipe tubes made of special alloys to make fuel rods, which are then bundled together to form a fuel assembly. This is nuclear fuel, and the core is the bundle of fuel rods, the reactor's nuclear fuel.

The nuclear fuel material is shaped into a cylindrical (pellet) plate or a hollow cylinder in the form of a metal, a metal alloy, an oxide, or the like, and is coated with an aluminum alloy, a zirconium alloy, a stainless steel, or the like. The core, which is the core of the reactor, consists of moderators to decelerate high-speed neutrons emitted from nuclear fuel into thermal neutrons, and coolants to remove the enormous heat generated by nuclear fission. The energy released by the nuclear fission chain reaction raises the core temperature, which can damage the reactor. To prevent this, the core is cooled by using a coolant. As a coolant, carbon dioxide and helium are used as gases, and hard water and heavy water are used as liquids.

Emergency Core Cooling System (ECCS) refers to a device that safely shuts down the core by supplying a large amount of coolant to the core when a loss of coolant accident (LOCA) occurs in a nuclear power plant. Under normal conditions, the coolant transfers heat out of the reactor, but if an accident occurs and the core cannot be cooled down, the fuel rod still has heat, and the nuclear fission product remaining in the fuel rod collapses even if the reactor is shut down. This is because the reactor can be core melted by dissipating heat. ECCS is therefore used after SCRAM (nuclear shutdown) to control the chain reaction. In general, reactors are shut down when ECCS is activated.

There are various types of reactors, such as pressurized water, boiling water, and high-speed growth furnaces. Each reactor is equipped with an appropriate ECCS. Nuclear power plants have several independent ECCS and are designed to cool the core with just one of the many. The ECCS system is usually powered by the power of the plant (while the generator is running inertia), and when the generator goes down, it acts as the emergency diesel generator of the plant.

1 schematically shows a reactor equipped with an ECCS.

In the case of an accident in which the piping of the primary coolant system in the reactor 10 is broken and the coolant in the core suddenly decreases (coolant loss accident), the ECCS 20 sends a large amount of the prepared coolant to the core to remove the remaining heat. This prevents the fuel from melting and safely stops the core.

However, ECCS in nuclear reactors raises questions about safety and utility.

"In July, Professor Hiromit Ino of Japan's University of Tokyo selected one of the most dangerous nuclear power plants in Japan and presented a scenario. When Genkai 1 was shut down due to an earthquake, emergency efforts were made to cool the reactor. The cooling system (ECCS) is activated, but this safety device is rather "a dagger": cracking or even exploding as a coolant is supplied to hundreds of degrees of reactor, as if a cold water is suddenly poured into a hot glass. It may be.

Concerns surrounding Busan Gijang-gun Gori 1, which has been controversial due to the recent power supply disruption, are similar to those of Genkai. In addition, Gori 1, which started commercial operation in Korea for the first time in 1978, received a 10-year license after extending its service life in 2008. Got into extra driving while. Life extension is to increase the service life through regular inspection when the design life of the nuclear power plant has expired.

The most important aspect of the life test is the durability of the pressure vessel surrounding the reactor. Pressure vessels weaken due to neutrons when exposed to radiation for a long time. There is no big problem during normal operation, but when the temperature drops sharply, the possibility of cracking becomes greater. -O

Second, cracks in the pressure vessel may occur when the emergency core cooling system is operated. When this device works, the reactor cools rapidly. At this time, the RTD is measured to find the possibility of cracking of the pressure vessel, and if it is higher than the standard value, the pressure vessel may break. "-Hankyoreh Shimbun, March 22, 2012, omitted below-

Korea cannot be free from nuclear safety issues, and as noted in the newspaper report above, an emergency core cooling system (ECCS) operated to cool the reactor in the event of a loss of coolant can pose a danger.

Ministry of Education, Science and Technology Notice No. 2009-37 "Criteria on the Performance of Emergency Core Cooling System in Pressurized Water Reactors" Article 3 No. 1 specifies the maximum temperature of cylindrical zirconium alloy cladding to be below 1204 ℃. In this case, the design temperature of the reactor coolant system is set at 650 ° F (343.33 ° C) .In view of these figures, if the coolant in the reactor is lost through a major disaster such as the Great East Japan Earthquake, the temperature inside the reactor may be lower than 343.33 ~. It can be expected to reach a range of up to 1204 ° C. If the coolant is suddenly supplied with coolant at a high temperature when the cladding at the reactor core is significantly high due to the loss of coolant, the core cladding and nuclear fuel rods and the combustible toxic rods that have become hot due to heat around the core, as pointed out by Professor Hiromit Ino University of Tokyo ( Burnable Poison Rod) may be damaged. The possibility of hot reactors cooling suddenly and causing brittle fractures cannot be ruled out. If the cladding material is damaged, the temperature rises above 1204 ° C., which is the upper limit specified by the Ministry of Education, Science and Technology, thereby further facilitating destruction of the reactor and related equipment. Supplying coolant to the reactor becomes more difficult and may eventually face the worst case of having to give up the coolant supply.

The present invention is to solve the conventional problems as described above, by providing a nuclear reactor cooling system capable of gradually cooling the reactor by supplying hot water heated by solar heat after pressurization to the reactor, by the emergency core cooling device It is intended to address the possibility of damaging the reactor and associated equipment when cooling the hot reactor with cold cooling water.

According to one aspect of the invention, in the nuclear reactor emergency cooling system of the nuclear power plant,

An emergency core cooling unit (ECCS) for cooling by supplying cooling water to the reactor in an emergency; And

An emergency reactor cooling system is provided, comprising: a solar hot water cooling unit for supplying hot water heated by solar heat after pressurization to a nuclear reactor in case of emergency.

The solar hot water cooling unit may include a pressurized pump for pumping water, a solar heater absorbing solar heat to heat water supplied from the pressurized pump, and a storage tank for storing the water heated by the solar heater.

The solar hot water cooling unit is an emergency generator for producing electricity to be supplied to a pressure pump, a power receiving facility for supplying electricity generated from an external power generation facility to the pressure pump, and receives the electricity from the emergency generator or the power receiving facility It may further include a motor for driving the pump, and a pressure adjusting unit for adjusting the discharge pressure of the pressure pump.

The solar hot water cooling unit may further include an internal combustion engine for driving the pressure pump.

The solar hot water cooling unit includes a bypass channel through which water heated in the solar heater bypasses the storage tank and is supplied to the reactor, and a first motor driving valve for opening and closing a channel connecting the solar heater and the storage tank; A second motor drive valve provided in the bypass channel to open and close the bypass channel, a cold water flow path for supplying cold water to the reactor, and a third motor drive valve provided in the cold water flow path to open and close the cold water flow path. It may include.

The solar hot water cooling unit may be disposed higher than the reactor so that the high temperature water may be introduced into the reactor by the head difference.

When the emergency core cooling unit (ECCS) can be operated, the reactor is initially cooled by the solar hot water cooling unit and then cooled by the ECCS, and when the ECCS cannot be operated, the hot water temperature is supplied while the temperature is lowered. The reactor can be cooled by the solar hot water cooling unit.

According to another aspect of the present invention, in the nuclear reactor emergency cooling method of the nuclear power plant,

Provided to the reactor in case of hot water heated by solar heat after pressurization, there is provided an emergency reactor cooling method characterized in that cooling the reactor by supplying while lowering the temperature of the hot water is lower than the reactor temperature.

The emergency reactor cooling method of the present invention can be generated when the reactor is cooled slowly by supplying hot water heated by solar heat after pressurization to the reactor in case of emergency, thereby cooling the high temperature reactor with cold cooling water by the emergency core cooling device. By addressing the potential damage of existing reactors and associated equipment, it is possible to safely and effectively cool down the reactor in an emergency.

1 schematically shows a nuclear reactor equipped with an emergency core cooling system (ECCS).
2 is a schematic diagram of an emergency reactor cooling system according to an embodiment of the present invention.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings.

2 is a schematic diagram of an emergency reactor cooling system according to an embodiment of the present invention.

As shown in FIG. 2, the emergency reactor cooling system of the present embodiment includes an emergency core cooling apparatus (ECCS) 100 for supplying cooling water to a reactor NR in an emergency in a nuclear reactor emergency cooling system of a nuclear power plant, and Solar hot water cooling unit 200 for cooling the reactor (NR) by supplying hot water heated by solar heat after pressurization to the reactor (NR) in an emergency.

In this embodiment, the emergency refers to a case where a coolant loss accident occurs due to damage of the reactor NR, the reactor coolant piping, or the like due to a very large disaster. An example would be an earthquake or tsunami exceeding the magnitude of the safety outage earthquake (SSE). The system of this embodiment is for safely cooling the reactor NR in such an emergency.

The solar hot water cooling unit 200 is a pressure pump 210 for pumping water, a solar heater 220 that absorbs solar heat and heats the water supplied from the pressure pump 210, and is heated in the solar heater 220. It may include a storage tank 230 for storing water.

The hot water described in the present embodiment refers to water in a superheated liquid state, wherein the superheated liquid refers to a liquid that does not vaporize and maintains a liquid state even when the temperature reaches a boiling point or more as the external pressure increases.

This is based on the following principle.

Boyle-Charles' Law defines Bohr's law that the gas pressure is inversely proportional to the volume when the temperature is constant, and Charles's law that the volume of the gas is proportional to the increase in temperature when the pressure is constant And the relationship between temperature, pressure, and volume at the same time.

This is expressed by the following equation.

In the above equation, k is constant.

Therefore, in order to satisfy the above equation, it can be seen that when the pressure rises, the corresponding temperature must also rise.

The boiling point of the liquid is the temperature at which the internal pressure of the gas and the external pressure become the same when the liquid evaporates. Applying this to the above equation, it is concluded that the boiling point of the liquid should rise when the external pressure rises.

The present invention utilizes the boiling point ascending principle by such a pressure rise. That is, by raising the pressure through the pressure pump 210 to increase the boiling point of the water, it is heated by the solar heater 220.

The solar heater 220 may be provided with a heat collecting portion and a heat storage portion, which absorbs sunlight and heats the pressurized water above the original boiling point through the heat medium therein to form hot water and uses it for cooling the reactor (NR). .

The degree of pressure rise by the pressure pump 210 may be determined in consideration of the desired boiling point rise effect, and may be selected from pressures below the critical point of the introduced fluid.

For example, when the introduced fluid is water, the critical point is 225.56 kgf / cm 2, 374.15 ° C., and high temperature water up to about 370 ° C. may be formed using the pressure pump 210 and the solar heater 220 of the present embodiment. In the case of seawater, considering the boiling point increase effect due to the molar concentration, it is expected to form hot seawater having a higher temperature.

In the present embodiment, in case of a coolant loss accident (LOCA), the high temperature water having a temperature similar to that of the reactor NR is supplied to the cooling water to prevent damage to the reactor NR, and then the temperature of the cooling water is gradually lowered. do. Given that the standard design temperature of the reactor coolant system of the Korean standard nuclear power plant is 650 ° F. (343.33 ° C.), it is possible to supply high temperature water of about 340 ° C. as the initial cooling water. Solar heater 220 is used. Boilers operating on fossil fuels such as diesel, kerosene, and coal in an emergency situation are likely to be difficult to supply fuel, and environmentally-friendly pollution is caused by the burning of fossil fuels.

Since the reactor NR should be continuously cooled without interruption in an emergency situation, the present embodiment includes a storage tank 230 in case that it is difficult to form hot water by solar heat, such as at night or on a cloudy day.

The solar hot water cooling unit 200 includes an emergency generator 240 for producing electricity to be supplied to the pressure pump 210, a power receiving facility 241 for supplying electricity generated from an external power generation facility to the pressure pump 210, and In addition, the motor 242 for driving the pressure pump 210 by receiving electricity from the emergency generator 240 or the power receiving facility 241 may further include a pressure control unit for adjusting the discharge pressure of the pressure pump 210. .

The power receiving facility is a device that converts electricity (high voltage electricity) supplied from an external power generation facility to low pressure to be suitable for operation of a load facility (pump, etc.), and may include a circuit breaker, a protection relay, a transformer, and a current transformer.

If the electric power can be supplied from the external power generation facility, the power receiving facility 241, otherwise the emergency generator 240 is driven by the motor 242, the pressure pump 210 operates. The rpm of the pump may be controlled through a pressure controller for controlling the discharge pressure of the pressure pump 210, and the pressure controller may be a motor inverter or a fluid coupling.

The solar hot water cooling unit may further include an internal combustion engine (not shown) for driving the pressure pump 210.

A small engine (not shown) such as an internal combustion engine may be connected to the pressure pump 210 to adjust the discharge pressure of the pump by adjusting the rpm of the engine.

This embodiment is an engine driven-pressure pump operated by a motor 242-pressure pump 210 driven by electricity supplied through an emergency generator 240 or a power receiving facility 241, an internal combustion engine (not shown). (Not shown) may include two types of pressure pumps. If necessary, it is also possible to have only one of two types of pressure pump, which is also included in the scope of the present embodiment.

The solar hot water cooling unit 200 includes a bypass channel 250 in which water heated in the solar heater 220 bypasses the storage tank 230 and is supplied to the reactor NR, and the solar heater 220 and the storage tank. The first motor drive valve 251 for opening and closing the waterway connecting the 230, the second motor drive valve 252 provided in the bypass waterway 250 to open and close the bypass waterway 250, and cold water reactor And a third motor driving valve 261 provided in the cold water flow passage 260 to be supplied to the NR, and provided in the cold water flow passage 260 to open and close the cold water flow passage 260.

Since the solar hot water cooling unit 200 is disposed higher than the reactor NR, hot water may be introduced into the reactor NR due to the head difference.

Since the solar hot water cooling unit 200 is prepared for an emergency in a nuclear power plant, the solar hot water cooling unit 200 is preferably disposed at a distance of 30 m or more above the ground of the power plant so as not to be damaged even by a disaster such as a tsunami. This allows the cooling hot water to be transferred to the reactor NR without a device such as a pump.

When the emergency core cooling unit (ECCS, 100) can be operated, the reactor NR is initially cooled by the solar hot water cooling unit 200 and then cooled by the ECCS 100, and the ECCS 100 cannot be operated. In this case, the reactor NR may be cooled by the solar hot water cooling unit 200 by supplying the high temperature water while lowering the temperature.

If the ECCS 100 can be operated, it is initially cooled with hot water, but gradually cooled by lowering the temperature of the hot water, and the reactor is sufficiently sufficiently that there is no possibility of damaging the reactor NR by the cold cooling water of the ECCS 100. When the temperature of the NR drops, the reactor NR is cooled through the ECCS 100.

When the ECCS 100 cannot be operated, after the initial cooling with high temperature water, the low temperature of the high temperature water is gradually supplied while the temperature of the reactor NR drops sufficiently. (NR) and cooled directly with cold water.

According to another aspect of the present invention, in the nuclear reactor emergency cooling method of the nuclear power plant,

The emergency reactor cooling method is characterized by cooling the reactor NR by supplying hot water heated by solar heat after pressurization to the reactor NR in an emergency, while lowering the temperature of the hot water having a temperature lower than the reactor NR temperature. Is provided.

As described above, the emergency reactor cooling method of the present embodiment gradually cools the reactor by supplying hot water heated by solar heat after pressurization to the reactor in case of emergency.

In the Great East Japan Earthquake and the Fukushima nuclear disaster, there was an accident in which the reactor coolant inside the reactor evaporated by the core heat and the core was exposed to the air.When the core was sprayed with super high temperature core cooling water without cooling the core, The ductility of the core disappears by shrinkage due to rapid cooling, and the core may become brittle and be destroyed. This embodiment allows the reactor to be cooled slowly by supplying hot water to the reactor in an emergency.

This prevents damage to the reactor and associated equipment that can occur when cooling the high temperature reactor with cold coolant by the emergency core cooling system, and enables safe and effective cooling of the reactor in an emergency.

In addition, the present embodiment absorbs the solar heat to generate hot water, unlike hot water boilers, such as diesel, kerosene, coal, etc. in the emergency, it is possible to reliably cool the reactor even when it is difficult to transport fossil fuels. And fossil fuel combustion to prevent environmental pollution.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Accordingly, such modifications or variations are intended to fall within the scope of the appended claims.

NR: reactor
100: emergency core cooling system
200: solar hot water cooling unit
210: pressure pump
220: solar burner
230: storage tank
240: emergency generator
241: Faucets
242: motor
250: bypass channel
251: first motor drive valve
252: second motor drive valve
260: cold water flow path
261: third motor drive valve

Claims (8)

In the reactor emergency cooling system of the nuclear power plant,
An emergency core cooling unit (ECCS) for cooling by supplying cooling water to the reactor in an emergency; And
And a solar hot water cooling unit configured to cool the reactor by supplying hot water heated by solar heat after pressurization to the reactor in an emergency. According to claim 1, The solar hot water cooling unit
A pressurized pump for pumping water;
A solar heater that absorbs solar heat and heats the water supplied from the pressure pump; And
And a storage tank for storing the water heated in the solar heater. The solar hot water cooling unit according to claim 2
An emergency generator for producing electricity to be supplied to the pressure pump;
A power receiving facility for supplying electricity produced at an external power generation facility to the pressure pump;
A motor that receives electricity from the emergency generator or the power receiving facility and drives the pressure pump; And
Emergency reactor cooling system further comprises a pressure regulator for adjusting the discharge pressure of the pressure pump. The solar hot water cooling unit according to claim 2
And an internal combustion engine for driving said pressure pump. The solar hot water cooling unit according to claim 2
A bypass channel through which water heated in the solar heater bypasses the storage tank and is supplied to the reactor;
A first motor driving valve for opening and closing a water channel connecting the solar heater and the storage tank;
A second motor driving valve provided in the bypass channel to open and close the bypass channel;
Cold water flow path for supplying cold water to the reactor; And
And a third motor driving valve provided in the cold water flow passage to open and close the cold water flow passage. 3. The method of claim 2,
The solar hot water cooling unit is disposed higher than the reactor, the emergency reactor cooling system, characterized in that the hot water is introduced into the reactor by the head difference. The method of claim 1,
When the emergency core cooling unit (ECCS) can be operated, the reactor is initially cooled by the solar hot water cooling unit and then cooled by the ECCS,
If the ECCS is unable to operate the emergency reactor cooling system, characterized in that for cooling the reactor by the solar hot water cooling unit by supplying while lowering the hot water temperature. In the reactor emergency cooling method of the nuclear power plant,
Cooling the reactor by supplying hot water heated by solar heat to the reactor in an emergency after pressurizing, while lowering the temperature of the hot water is lower than the temperature of the reactor temperature.

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