KR20130104336A - Passive core cooling system - Google Patents

Abstract

PURPOSE: A passive core cooling system improves safety by measuring online the radiation of a reactor cooling water in real time. CONSTITUTION: A cooling water radiation measurement device (13) is installed on the exterior wall of a reactor container. The reactor cooling water radiation measurement device operates by an independent battery power. A pressure accumulator (11) has an opening and closing valve. An exhaust valve (12) is connected to a measured value signal of the reactor cooling water radiation measurement device. The exhaust valve operates by battery power.

Description

Passive Core Cooling System

 The present invention generally relates to a core cooling system, and more particularly, to configure the reactor core to be passively cooled without operator intervention by a reactor coolant radiometer operated by an independent battery in an emergency, thereby ensuring complete internal and external operation of the nuclear power plant. It relates to a new passive core cooling system that can properly cool down the reactor core in case of a power loss accident, thereby preventing serious accidents and contributing to mitigation.

In general, since nuclear power plants use fission energy despite high economic feasibility, securing safety is most important. Therefore, in order to secure safety, engineering safety facilities are installed multiplely and independently. However, engineering safety equipment may lose its function due to earthquakes or tsunamis exceeding design standards, and Japan's Fukushima nuclear accident in March 2011 is a typical example.

In the case of a nuclear power plant, if the coolant that lowers the temperature in the reactor is not properly supplied, the temperature in the reactor continues to rise due to fission energy. Accordingly, if the fuel is damaged, various radiation and radioactive pollutants that are harmful to the environment are spread to the surroundings. It can be very dangerous. Therefore, there is an urgent need for a device capable of adequately supplying cooling water to the reactor core in the event of a nuclear power plant accident due to natural disasters such as earthquakes or tsunamis, which can cause serious accidents.

On the other hand, in general, reactor coolant radiation measurements in nuclear power plants are normally measured by primary system coolant radioactivity measurement by means of sampling of reactor coolant in the downflow pipe of chemical volume control system, and secondary system is blowdown of steam generator. Due to the sampling of the secondary system coolant in the pipe, radioactivity is being taken off-line during normal operation.

In the event of an accident in a nuclear power plant, the leakage pipe and the steam generator outlet pipe of the chemical volume system are closed by the automatic operation of the valve installed in the pipe, so it is impossible to measure the radioactivity of the reactor coolant in the event of an accident.

As a result, current reactor designs do not provide for reactor coolant radiation measurements in real time at the time of an accident, and thus no radiometric information related to nuclear fuel damage and the resulting reactor core damage is being provided. In particular, in case of accidents that can cause serious accidents such as complete loss of power inside and outside of the nuclear power plant, safety system for active reactor cooling such as reactor coolant radiation measurement and pump and valve, which are important information of nuclear power plant safety, are completely operated. It did not, however, cause serious accidents such as core meltdown that occurred in March 2011 at the Fukushima nuclear accident in Japan. As such, the large-scale commercial nuclear power plants currently operating internationally can be said to have weaknesses in nuclear power safety that can cause serious accidents in case of complete loss of power in and out of the house.

After the TMI-2 nuclear accident in the United States in 1979, R & D and installation of passive safety systems for core cooling and core residual heat removal have been underway, and are currently being developed internationally with AP1000 and GE's SBWR in Westinghouse, USA. Passive core cooling and core residual heat removal safety systems are being introduced into small and medium-sized reactors. The passive core residual heat removal system currently being developed is mostly related to the passive residual heat removal system using the steam generator of the secondary system. The passive residual heat removal system using the steam generator of the secondary system may have insufficient measurement, operation, and performance necessary in case of complete power loss accidents.

Meanwhile, the passive core cooling system currently developed by NuScale Power and mPower in the United States utilizes the upper reactor exhaust valve and the reactor cooling pool to determine the measurement data and core cooling timing required in case of complete power loss accidents. And passive valve operation.

Therefore, it is necessary to improve the design and cope with serious accident management to prevent serious accidents and reduce accidents in case of complete loss of power in and out of the nuclear power plant or new nuclear reactor currently being developed. On-line real-time measurement of reactor coolant radiation using an independent battery in an accident and core damage using measured real-time radiation data, determination of core cooling timing, and installation of passive core cooling system, There is an urgent need to improve the safety of nuclear power plants to alleviate accidents.

The present invention is to solve the problems of the prior art described above and to add various other advantages, and in particular to improve the safety of nuclear power plants for the prevention of serious accidents and to alleviate accidents in case of complete power loss accidents inside and outside of nuclear power plants, independent of emergency The reactor coolant radiation meter, operated by an in-battery, is configured to cool the reactor core passively without operator intervention, so that the reactor core can be properly cooled in the event of a complete loss of power in and out of the plant. It is an object to provide a passive core cooling system that can contribute to mitigation.

This object is achieved by a passive core cooling system provided according to the invention.

The passive core cooling system provided according to an aspect of the present invention is a passive core cooling system for cooling a nuclear reactor, and in the case of a hot tube or an integral reactor connected between a reactor vessel surrounding a reactor core and a steam generator, an annular upper part annular shape A reactor coolant radiometer installed on an outer wall of the reactor vessel in the space and operable by an independent battery power source; A safety injection tank or an accumulator of an existing nuclear power plant emergency core cooling system, having an on-off valve connected to the measured value signal of the reactor coolant radiation measuring instrument and opening to operate when the measured value exceeds a set value; A reactor upper head exhaust valve connected to a measured value signal of the reactor coolant radiation meter, the on / off valve operative to open when the measured value exceeds a set value, the reactor upper head exhaust valve being operable by the battery power source; The steam discharged from the upper head exhaust valve of the reactor gathers in the reloading water storage tank in the reactor building to form a pipe, and is cooled by heat exchange with the tank cooling water, and then the upper portion of the safety injection tank or the accumulator through each pipe. In order to lower the water vapor or gas area or head, it includes pipes installed to be introduced into the safety injection tank or the primary system connection of the accumulator (low temperature pipe or direct reactor injection pipe) to be introduced into the reactor vessel.

In one embodiment, the radiation measurement signal measured by the reactor coolant radiation meter is received and processed, and as a result, the nuclear fuel damage and the resulting core damage is predicted and determined, the measured radiation measurement value exceeds the set value And a control means for controlling the opening of the safety injection tank or the accumulator by opening the signal to the reactor and the upper head exhaust valve of the nuclear reactor, and operating by the battery power source.

In another embodiment, the reactor coolant radiometer may measure the high energy gamma rays emitted from the outer wall of the upper annular space reactor vessel in the case of the hot tube or integral reactor.

According to the present invention having the above-described configuration, the reactor coolant radiation indicating the core damage caused by nuclear fuel damage in real time in case of complete power loss accident in the nuclear power plant and on-line is measured online in real time, and the information related to the criterion of the degree of nuclear reactor core damage is obtained. It provides in real time, and the safety of reactor through prevention of serious accident and mitigation of accidents by providing passive core cooling system by natural circulation in the situation where core cooling is impossible because active pump or valve does not operate due to complete loss of power inside and outside. Can improve.

The present invention can be installed by a simple design change to the currently operating nuclear power plant can be used to prevent serious accidents and accidents of the nuclear power plant during operation can significantly improve the safety of nuclear power plants at low cost.

In addition, the present invention has a remarkable effect of removing the existing active pumps and valves and designing the driven type to achieve the design simplification and cost reduction effect to improve the safety of the new reactor.

1 is a view schematically showing the overall configuration of a nuclear reactor nuclear reactor steam supply system with a passive core cooling system according to an embodiment of the present invention.
2 is a view schematically showing the configuration of a radiation meter in a passive core cooling system according to an embodiment of the present invention.
Figure 3 is a schematic diagram for explaining the operation of the passive core cooling system according to an embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with 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 is defined by the claims of the present invention.

In the following description of the present invention, 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.

Hereinafter, a passive core cooling system according to a specific embodiment of the present invention will be described with reference to the drawings.

A passive core cooling system provided according to an aspect of the present invention, in the event of an emergency situation such as nuclear fuel damage due to a complete loss of power in a facility such as a nuclear power plant, damages to the reactor coolant by means of batteries installed for emergencies. It is a core cooling system that measures radioactivity such as high energy audit ships emitted from fissile material generated from the reactor and passively supplies the coolant to the reactor core by natural circulation according to the measurement result.

This passive core cooling system is a passive core cooling system for cooling nuclear reactors of nuclear power plants. 1 schematically illustrates a reactor nuclear steam supply system including a system according to the present invention, a reactor vessel 10, a safety injection tank or accumulator 11, a reactor upper head exhaust valve 12, a reactor The coolant radiation meter 13, the reload water storage tank 14, the cold tube 15, the hot tube 16, the pressurizer 17, the steam generator 18, the reactor coolant pump 19, and the like may be provided. .

The reactor vessel 10 is provided with an inner container surrounding the core, and the nuclear fission reaction takes place. In a nuclear power plant operating normally, the reaction heat generated in the reactor vessel 10 increases the temperature of the cooling water, and the high temperature cooling water passes through the hot tube 16 and optionally passes through the pressurizer 17 and then is supplied to the steam generator 18. do. The high temperature cooling water introduced into the steam generator 18 is cooled after generating steam through heat transfer to the secondary side cooling water, and the generated steam may be supplied to a turbine or the like for generating electric power. The cooled coolant is then returned to the reactor vessel 10 via the low temperature pipe 15 by the reactor coolant pump 19 to circulate the coolant.

On the other hand, in the case of core damage caused by nuclear fuel damage in the reactor vessel 10 in an emergency such as when the internal and external power supply is completely lost, nuclear fission material from the core in the reactor vessel 10 is mixed with high temperature cooling water. As a result, radiation levels, such as gamma rays in reactor coolant, can rise.

According to the present invention, in the case of the high temperature tube 16 or the integral reactor, radiation such as gamma rays from the high temperature cooling water flowing in the reactor core upper annular space is independent by in-house AC power during normal operation and in case of complete loss of internal and external power. Measurement is made by the reactor coolant radiometer 13 operating by battery power.

The reactor coolant radiometer 13 is installed in the high temperature tube 16 connected between the reactor vessel 10 and the steam generator 18 surrounding the reactor core and in the case of an integral reactor, the reactor vessel outer wall of the upper annular space. Preferably, as illustrated in FIG. 2, the configuration may be enabled by an independent battery power source 20. When the reactor coolant radiation meter 13 is an integral reactor with the high temperature tube 16, it is preferable to measure the high energy gamma rays emitted from the outer wall of the core annular space reactor vessel.

2 illustrates the configuration of a reactor coolant radiation meter 13 that may be an on-line real-time reactor coolant high energy gamma ray radiation measurement equipment in the present invention. As illustrated in FIG. 2, the reactor coolant radiation meter 13 is a heat shield 131, a radiation source term 133, which is a measurement portion installed on the outer wall of the annular space reactor vessel in the core in the case of the hot tube 16 or the integral reactor. , A sensor unit consisting of a Ge-crystal 135, a preamplifier 137, a liquid nitrogen 139, and an amplifier 21, which is a control unit for processing a radiation measurement signal output by the sensor unit and controlling other components. ), A multi-channel analyzer 22, a computer (PC) 23, a data storage unit 25, a data display 24, and the like.

The reactor coolant radiation measuring instrument 13 may be operated by an on-site AC power source during a steady state operation of a nuclear power plant, or by a battery power source 20 in case of a complete power loss in and out of a nuclear power plant. In a specific embodiment, the reactor coolant radiation meter 13 may be installed as a plurality of reactors that independently operate at multiple positions of the outer annular space reactor vessel outer wall in the case of the reactor hot tube 16 or an integral reactor. This can increase the reliability of the instrument by providing two or more different reactor coolant radiometric data in real time.

The computer 23 of the control unit of the reactor coolant radiation meter 13 receives and processes the measured radiation measurement signal, and as a result predicts and judges the nuclear fuel damage and the core damage accordingly, and the measured radiation measurement value is When the set value is exceeded, it is a control means for controlling the opening of the safety injection tank or the accumulator 11 by sending an opening signal to the reactor upper head exhaust valve 12.

In the example shown in FIG. 2, the battery power source 20 provides not only the amplifier 21 but also all the power required for the sensor unit and the control unit of the reactor coolant radiometer 13. In addition, as will be described further below, the battery power source 20 operates to open the valves necessary for the spontaneous circulation of the coolant, such as the on / off valve of the safety injection tank or the accumulator 11 and the reactor upper head exhaust valve 12. Is also supplied.

If the reactor coolant radiation meter 13 is a hot tube 16 or an integral reactor in an emergency, the computer 23 measures this gamma ray from the outer wall of the central annular space reactor vessel and the measured value exceeds the set value. Receiving it is determined that the coolant should be put into the reactor vessel 10, it is possible to control the opening and closing valve of the safety injection tank or accumulator 11 and the reactor upper head exhaust valve 12 at the same time.

Alternatively, the on / off valve of the safety injection tank or accumulator 11 and the reactor upper head exhaust valve 12 are connected directly to the measured value signal of the reactor coolant radiation meter 13 so as to open when the measured value exceeds a set value. can do. As mentioned above, these on / off valves are operably connected to the battery power source 20.

According to the present invention, as illustrated in FIG. 1 and FIG. 3, the steam discharged from the reactor upper head exhaust valve 12 gathers into a header inside the reloading water storage tank 14 in the reactor building to form a piping and tank cooling water. After cooling through the heat exchange with the injection to the upper portion of the safety injection tank or accumulator (11) upper steam or gas area or head of the primary system connection of the safety injection tank or accumulator (low temperature pipe or reactor direct injection pipe) After that, pipes are installed to be introduced into the reactor vessel 10.

Accordingly, the steam of the high temperature and high pressure in the reactor vessel 10 may be discharged through the reactor upper head exhaust valve 12 and then cooled through heat exchange with the tank cooling water while passing through the reload water storage tank 14. . The low temperature coolant cooled in the reload water storage tank 14 is supplied to the safety injection tank or accumulator 11 or the safety injection tank or accumulator 11 through the respective pipes from the header, and then the reactor vessel 10. It may be provided internally to cool the core inside the reactor vessel 10.

As described above, according to the present invention, in the case of a complete loss of power in and out of a nuclear power plant, radiation such as nuclear coolant high energy gamma-ray from nuclear fission generating material due to core damage is real-time online using battery power. It provides a real-time reactor coolant radiation measurement equipment to measure the temperature, and determines the operating time of the passive core cooling system according to the measured radiation value of the real-time reactor coolant gamma ray, and provides a passive core cooling system which is a passive core cooling system that operates passively. do.

In addition, according to the present invention, in the case of an integral reactor and piping of each of the reactor high-temperature tubes, two or more real-time reactor coolant high energy gamma ray radiation measuring instruments operated by an independent battery power source may be installed on the outer wall of the core annular space reactor vessel. In this case, the real-time reactor coolant radiation measurement equipment can measure the reactor coolant high-energy gamma-ray radiation on-line by AC power during steady state operation and by battery power in case of complete loss of power inside and outside the plant. By using data such as nuclear reactor coolant radioactivity values and reactor pressure and coolant temperature that can be obtained from post-incident monitoring measurements, it is possible to determine and operate the core damage level and the operating time of the passive core cooling system.

The passive core cooling system of the present invention may use the safety injection tank of the emergency core cooling system in the case of the existing commercial water reactor. On the other hand, if there is no safety injection tank, a safety grade pressurized gas or pressurized steam accumulator can be used. Alternatively, the primary system connection of the safety injection tank or accumulator (low temperature pipe or reactor direct injection pipe) may be used.

According to the natural circulation circuits according to the invention, the steam from the reactor core flows out of the reactor vessel upper head exhaust valve 12 and then passes through the IRWST (reactor reload coolant storage tank) 14, whereby IRWST ( It is cooled by heat exchange with cooling water in 14). Then, the pipe may be introduced into the reactor vessel 10 after being injected into the safety injection tank or the accumulator upper gas or the vapor region through a rupture disk operating in a pressure difference along each pipe. Alternatively or additionally, to lower the head, a path is introduced into the reactor vessel 10 after being injected into the upper portion of the safety injection tank or the primary system connection (low temperature pipe or direct reactor injection pipe) of the accumulator 11. Can be.

Pipes with this route establish a closed natural circulation circuit connecting the core heat source with the IRWST heat sink and the safety injection tank or coolant from the accumulator. As a result, for example, an accident occurs where power is not normally supplied to a power plant, and when heat is continuously generated in the core, the steam generated by the generated heat is naturally cooled and the cooled water, that is, cooling water, is supplied to the reactor core. And naturally replenish the existing cooling water, allowing the reactor core to be passively cooled.

As described above, according to the present invention, the reactor core is configured to be cooled in a passive manner by the reactor coolant radiometer operated by an independent battery in an emergency, thereby reducing the reactor core in the event of a complete loss of power in and out of the nuclear power plant. It can be cooled appropriately to provide effects such as preventing serious accidents and contributing to mitigation.

10: reactor vessel
11: safety injection tank (or accumulator)
12: Reactor upper head exhaust valve
13: Reactor Coolant Radiation Meter
131: Lead shield
133: radiation source term
135: Ge-crystal
137: preamp
139: liquid nitrogen
14: Reloading Water Storage Tank
15: low temperature tube
16: high temperature tube
17 pressurizer
18: steam generator
19: reactor coolant pump
20: battery power
21: amplifier
22: Multi Channel Analyzer
23: computer
24: display
25:

Claims (3)

As a passive core cooling system for cooling nuclear reactors
In the case of a hot tube 16 or an integral reactor connected between the reactor vessel 10 and the steam generator 18 surrounding the reactor core, the reactor is installed on the outer wall of the annular space reactor vessel and operable by an independent battery power source 20. A reactor coolant radiation meter (13);
A safety injection tank or accumulator (11) connected to the measured value signal of the nuclear reactor coolant radiation meter (13) and having an on / off valve operable to open when the measured value exceeds a set value, and operable with the battery power source (20); Wow;
A reactor upper head exhaust valve 12 which is connected to the measured value signal of the reactor coolant radiation meter 13 and operates to open when the measured value exceeds a set value, and is operable by the battery power source 20; ;
The steam discharged from the upper head exhaust valve 12 of the reactor is cooled by heat exchange with the tank cooling water via the reloading water storage tank 14 in the reactor building, and then the safety injection tank or After being injected into the upper steam or gas area of the accumulator 11 or after being injected into the upper portion of the low temperature pipe or the reactor direct injection pipe that is the primary system connection pipe of the safety injection tank or the accumulator 11 to lower the head, Passive core cooling system, characterized in that it comprises a natural circulation circuit pipes installed to be introduced into the reactor vessel (10). According to claim 1, Received and processed the radiation measurement signal measured by the reactor coolant radiation meter 13, as a result of the prediction and determination of nuclear fuel damage and the core damage according to the result, the measured radiation measurement value is set value If exceeded, the control signal to open by sending an open signal to the lock valve of the safety injection tank or the accumulator 11 and the upper head exhaust valve 12 of the reactor, the control to be operated by the battery power source 20 Passive core cooling system, characterized in that it comprises a means (23). 3. The passive core cooling system according to claim 2, wherein the reactor coolant radiation meter 13 measures the high energy gamma rays emitted to the outer wall of the central annular space reactor vessel in the case of the hot tube 16 or an integral reactor. 4. .

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