"China's "advanced advantages" of nuclear power have obvious features in terms of technological maturity and project construction level, and have absorbed domestic and international experience feedback, and the safety level is better than that of existing international nuclear power plants of the same kind."
After the Fukushima nuclear accident, due to the prudent attitude and the principle of safety first, the deployment of nuclear power “four countries†should be born. The executive meeting of the State Council requires immediate organization of comprehensive safety inspections of China’s nuclear facilities, effectively strengthens the safety management of the nuclear facilities currently under operation, comprehensively reviews the nuclear power plants under construction, and strictly approves new nuclear power projects.
On the fifth day of the accident, China deployed nuclear power safety inspections. In more than 9 months, comprehensive safety inspections were conducted on 41 nuclear power plants under construction, nuclear power units under construction, 3 nuclear power units to be built, and all civil research reactors and nuclear fuel cycle facilities. The sensitivity of the reaction, the degree of attention, and the speed of start-up are rare in the world.
“The results of the inspection are gratifying.†A few days ago, Ye Qichen, an academician of the Chinese Academy of Engineering, the chief designer of the Qinshan Phase II project, an expert advisory committee of the National Defense Science and Technology Industry Bureau, and a member of the Nuclear Safety Experts Committee, said in an exclusive interview, “Prevention against similar Fukushima Nuclear accidents have short-term, medium-term, long-term plans and corresponding countermeasures, and each nuclear power plant has targeted improvement measures."
“The Fukushima nuclear accident should be a mirror of our improvement.†At the same time, he believes that the development of nuclear power is China’s strategic choice, but safety is the life of nuclear power. China’s nuclear power must achieve long-term and sustainable development, and nuclear power development must be Advance safely and efficiently.
China's operating nuclear power plants are generally safe, and nuclear safety supervision is in place. After the Fukushima nuclear accident, China immediately launched a nuclear safety inspection. In the process, what are the major problems found?
Qiqi Ye: The overall conclusion of China's nuclear power integrated safety inspection is: China's nuclear safety standards fully adopt the safety standards of the International Atomic Energy Agency, and the nuclear safety regulations and standards system is in line with international standards. Civil nuclear facilities have fully demonstrated the external events such as earthquakes and floods in the site selection. Nuclear power plants have been effectively managed in all aspects of design, manufacturing, construction, commissioning and operation, and their overall quality has been controlled.
The main problems discovered during the inspection were: the flood control capability of individual NPPs did not meet the new requirements, the seismic capability of individual civil research reactors and nuclear fuel cycle facilities did not reach the new standard, and some NPPs did not establish procedures for the prevention and mitigation of severe accidents. Relevant departments and enterprises on these issues have quickly organized rectification and have achieved initial results.
"Looking Hope": How to understand and absorb lessons learned from the nuclear accident at Fukushima for China's nuclear power security?
Ye Qichen: It can be seen from the Fukushima nuclear accident that the following improvement measures should be taken, including: strengthening the waterproof and inundation measures of nuclear power plants during extreme natural disasters; increasing emergency water recharge measures during extreme natural disasters; based on the reliability of existing power supplies , increase temporary power supply in case of power outages in the event of extreme natural disasters; increase emergency monitoring devices for spent fuel pools; increase hydrogen monitoring and control facilities in emergency situations; ensure emergency control centers can stay in extreme natural disasters Sex; emergency radiation environmental monitoring and improvement to ensure the reliability of monitoring during extreme natural disasters; establish early warning of external disasters and formulate disaster prevention plans; formulate guidelines for severe accident management, guidance for extreme disaster mitigation and other measures.
China learned lessons from the Fukushima nuclear accident. According to the different levels of construction of nuclear power plants under construction, corresponding measures have been taken to prevent the potential safety hazards caused by extreme natural disasters.
"Looking Hope": What are the aspects of the "advanced advantage" of China's nuclear power?
Ye Qichen: At present, China's nuclear power generation units mostly use new models from the 1990s onwards, known as the second generation of improved type, and the technical level has reached the international advanced level. The basic realization of independent design, independent manufacturing, independent construction and independent operation, built a complete nuclear fuel supply system. The safety performance of the power plants in operation and construction is greatly improved, core damage probability (CDF), radioactivity early release probability (LERF), and radioactivity release probability (LRF) are close to three generations of safety technology. The annual load factor of the nuclear power plant in operation reaches 85% 90%, which is basically the normal operation except for the time for changing the fuel.
The operation of nuclear power plants is generally safe and nuclear safety supervision is in place. Preventing similar Fukushima nuclear accidents has short-, medium-, and long-term plans and corresponding countermeasures; each nuclear power plant has targeted improvement measures. All nuclear power generators operate at the international level.
At present, there are 15 nuclear power generating units that have been put into operation in the mainland of China. There have never been operational incidents of international nuclear event classification (INES) grade 2 or above, and there have never been incidents that cause pollution or harm to people or the environment. . The level of the radiation environment around the nuclear facilities has always remained within the natural background fluctuation range. Although the number of nuclear power generating units in operation in China has continuously increased, the number of operational incidents has shown an overall downward trend.
The construction of nuclear power plants is progressing well and safely with quality control. The "advanced advantage" of China's nuclear power has obvious features in terms of technological maturity and engineering construction level. It has absorbed domestic and international experience feedback, applied new achievements in current scientific and technological development, and adopted a series of improvements in design and improved The safety level is better than that of existing international similar nuclear power plants. At the same time, the localization rate of the equipment reached 80%, and the construction quality was strictly controlled.
"The most stringent safety measures must be taken"
"Looking Hope": What are the specific requirements for ensuring nuclear power plants and environmental safety?
Ye Qiyi: There are three basic requirements: First, the safe shutdown of reactors. Once the reactor fails, the reactor will stop. If there is an accident, there is still a nuclear reaction, thermal conductivity will not come out, and the accident will get bigger and bigger; the second is to ensure that the reactor residual heat is exported. The nuclear power plant is different from the thermal power plant. There is no energy to stop the burning of the thermal power plant. The maximum latent heat is there. The nuclear power plant still has some waste heat, which is about 6% of the original power, and it declines to 1% 2% in one day and 3 million kilowatts of thermal power. The 6% of the nuclear power generating units are equivalent to 180,000 kilowatts, which is quite a large number. Therefore, these energy must be derived. Third, the radioactive containment is included. If these three principles are followed, even if any accident occurs, it will not affect the environment.
"Looking Hope": What are the specific security measures adopted in China's nuclear power design?
Ye Qichen: Nuclear power design must adopt the most stringent safety measures. Anti-earthquake design: The site must be far away from faults, have the ability to resist safety shutdown earthquakes, and its annual probability of surpassing is 0.01%. The foundation of the factory building should be placed on the bedrock. The design of China is like this. The design of Japan is very controversial. The east coast of Japan happens to be at the junction of Asia and the Pacific. The Japanese also admitted that a nuclear power plant should not be built here. Americans said that there must not be a nuclear accident like the Fukushima Daiichi nuclear power plant in the United States.
In terms of flood prevention requirements: Within one hour of the earthquake damage at the Fukushima Dai-ichi nuclear power plant, the safety protection system and emergency power supply are working properly. If there is no tsunami, there will be no nuclear accident at the Fukushima Daiichi nuclear power plant. We see that Units 5 and 6 have no problem. In the reference plant plane, the emergency power supply is not problematic for flooded units, and flooded units are problematic, so we have to consider external flood event combinations. Including the highest astronomical tide, probably the largest storm surge (typhoon), tsunami, sea level rise, storm floods, broken dyke upstream, and wave effects, the probability of surpassing is 0.1%, making the plant floor higher than the benchmark flood level, ie dry site. What is a dry site? It is in front of the largest flood that it cannot be flooded.
Power reliability: Two main plant transformers for each unit, supplying power from the main network; one dedicated back-up power supply and two standby plants; two nuclear-grade emergency diesel generators providing emergency power; An additional diesel generator provides backup emergency power.
Anti-explosion measures: A hydrogen concentration measuring device is provided to monitor the hydrogen concentration; a mobile hydrogen complex device is provided, and a non-active hydrogen complex device is added so that hydrogen recombination can be performed at any time.
To prevent the overpressure failure of the containment: Set up a containment filtration and discharge system to filter out radioactive impurities, aerosols, and elemental iodine, and then filter through the metal wool to discharge it into the atmosphere to prevent overpressure of the containment vessel and to avoid environmental pollution.
To prevent overpressure of pressure vessels and high-pressure melt-reactors: Set a pressure regulator to quickly relieve the pressure of the pressure vessel under severe accident conditions.
In addition to these measures, a bulk water injection system is now being developed to prevent the core melt from leaking out of the pressure vessel.
To achieve a safe and efficient development of nuclear power, "Viewpoint": The choice of nuclear power technology line is a topic of debate. What are the major considerations in the selection of China's technology route?
Ye Qichen: China's long- and medium-term nuclear power development plan (2005-2020) has identified "adhere to the development of millions of kilowatts of advanced pressurized water reactor nuclear power plant" and "in accordance with thermal neutron reactors - fast neutron reactors - controlled nuclear fusion reactor three steps" The nuclear power development strategy will enable China to realize the autonomy of advanced PWR nuclear power project design, equipment manufacturing, engineering construction and operation management as soon as possible, and form a comprehensive capacity for the construction of Chinese brand advanced nuclear power plants in batches to realize the leap-forward development of nuclear power technology. World advanced level of nuclear power.
At present, the technical route for the development of nuclear power in China mainly includes several aspects: First, it continues to adhere to the PWR type route; secondly, it uses three generations of advanced PWRs as the basis for the serialization of China’s nuclear power generation units; and thirdly, it builds a proper batch of second generations. The improved PWR units are the third-generation advanced nuclear power technology tracking and researching other reactor types, and the fifth is tracking the research and development of the fourth-generation nuclear power technology and reactor type.
"Looking Hope": In the technical line just mentioned, PWR has been mentioned many times. What are the special considerations?
Ye Qichen: China's rigs that have been built and operated in the past 30 years, except for two heavy water reactors, are all PWR units. At present, the basis for establishing nuclear power technology, manufacturing, and operation in China is also pressurized water reactors. Continuing to adhere to the PWR route is most beneficial to the sustainable development of China’s nuclear power.
From a safety point of view, PWR nuclear power plants have four barriers, and nuclear fission products are fixed within these four barriers.
First, uranium dioxide pellets can contain 98% of fission debris and fission products; after nuclear fission, uranium atoms split into two fragments and two to three neutrons. These two fragments are radioactive and emit radiation like alpha ray, beta ray, gamma ray, etc. After fission, the fragments will not overflow in the uranium dioxide pellets, the pellets will not melt, radioactive fragments will remain in the In the uranium dioxide pellets, uranium dioxide itself plays a role in containing fissile fragments, but fission products are random, 2% may be gaseous, 98% fission products are solid, and the gaseous state may run. come out.
Second, the zirconium cladding tube encloses the fuel and the fission products. There is a small space inside. There is a spring in the space. The gaseous fissioners gather at the top and are stored. The shell tube is not broken and the gas will not come out. .
Third, the pressure boundary can contain radioactive high temperature and high pressure coolants. The water within the pressure boundary works at 150 atmospheres. Leakage is not allowed during the work process because the coolant water is radioactive. When the nuclear power plant was put into operation, it was tested at 219 atmospheres, 1.33 times the actual pressure, and no leakage was guaranteed.
Fourth, the containment can withstand external damage, such as tornadoes, aircraft impacts, etc., and can prevent radioactive leakage in case of a serious accident. The inner surface is lined with a 6 mm thick steel lining and welded together. The outside is 1 meter thick prestressed reinforced concrete and is closed during operation.
"Looking Hope": At present, the world's third-generation nuclear power generation of pressurized water reactors is mainly built in China. What has been the improvement in its safety? What are the characteristics?
Ye Qichen: At present, the world's third-generation nuclear power plants under construction are mainly AP1000 and EPR. The third-generation PWR nuclear power plants have altogether 8 units under construction worldwide, and China accounts for 6 units. China is in a leading position. The AP1000's four nuclear power plants are all built in China. The EPR nuclear power unit under construction has a total of four units, one in Finland and still not completed; one in France and two in Taishan, China. At present, Taishan EPR project has been successfully constructed, and No. 1 machine has been hoisted into a full-scale installation stage. It may exceed the progress of French unit engineering.
The AP1000 features passive safety systems, severe accident prevention and mitigation, double containment, full digital instrumentation and advanced control rooms, and modular construction. Its passive safety systems include passive safety and passive residual heat discharge systems, multistage automatic pressure relief systems, and passive containment cooling systems. The design of this system enables the treatment and mitigation of design basis accidents and ultra design basis accidents, and the derivation of post-accident decay heat without depending on the active equipment attached to the power system, and at the same time, the atmosphere becomes the final heat sink without accidental conditions. It is necessary to pump cooling water to remove the heat released during the accident. For the prevention and mitigation of serious accidents, the flooding technology of the reactor cavity, the hydrogen ignition in the containment vessel, and the hydrogen complex system were mainly used.
EPR features high power (1500MWe1700MWe), 4-channel safety system, severe accident prevention and mitigation, fully digital instrumentation and advanced control room, and modular construction. EPR reduces the probability of core melting to 10-6/year or less, and can mitigate the consequences of accidents in the event of a serious accident, without causing radioactive contamination of the environment. Effectively eliminate the environmental impact of radioactive accidents.
AP1000 and EPR nuclear power generation units are nuclear power generators of the new generation developed internationally in the 1990s. From the design stage, they fully considered the prevention and mitigation of serious accidents, and the design safety level was further improved. China is currently digesting and absorbing the three generations of nuclear power technologies it has introduced, developing new three-generation models based on its own experience, and forming the capacity to build large-scale, advanced Chinese nuclear power plants. This will be more conducive to China's nuclear power security, efficient and orderly development.
After the Fukushima nuclear accident, due to the prudent attitude and the principle of safety first, the deployment of nuclear power “four countries†should be born. The executive meeting of the State Council requires immediate organization of comprehensive safety inspections of China’s nuclear facilities, effectively strengthens the safety management of the nuclear facilities currently under operation, comprehensively reviews the nuclear power plants under construction, and strictly approves new nuclear power projects.
On the fifth day of the accident, China deployed nuclear power safety inspections. In more than 9 months, comprehensive safety inspections were conducted on 41 nuclear power plants under construction, nuclear power units under construction, 3 nuclear power units to be built, and all civil research reactors and nuclear fuel cycle facilities. The sensitivity of the reaction, the degree of attention, and the speed of start-up are rare in the world.
“The results of the inspection are gratifying.†A few days ago, Ye Qichen, an academician of the Chinese Academy of Engineering, the chief designer of the Qinshan Phase II project, an expert advisory committee of the National Defense Science and Technology Industry Bureau, and a member of the Nuclear Safety Experts Committee, said in an exclusive interview, “Prevention against similar Fukushima Nuclear accidents have short-term, medium-term, long-term plans and corresponding countermeasures, and each nuclear power plant has targeted improvement measures."
“The Fukushima nuclear accident should be a mirror of our improvement.†At the same time, he believes that the development of nuclear power is China’s strategic choice, but safety is the life of nuclear power. China’s nuclear power must achieve long-term and sustainable development, and nuclear power development must be Advance safely and efficiently.
China's operating nuclear power plants are generally safe, and nuclear safety supervision is in place. After the Fukushima nuclear accident, China immediately launched a nuclear safety inspection. In the process, what are the major problems found?
Qiqi Ye: The overall conclusion of China's nuclear power integrated safety inspection is: China's nuclear safety standards fully adopt the safety standards of the International Atomic Energy Agency, and the nuclear safety regulations and standards system is in line with international standards. Civil nuclear facilities have fully demonstrated the external events such as earthquakes and floods in the site selection. Nuclear power plants have been effectively managed in all aspects of design, manufacturing, construction, commissioning and operation, and their overall quality has been controlled.
The main problems discovered during the inspection were: the flood control capability of individual NPPs did not meet the new requirements, the seismic capability of individual civil research reactors and nuclear fuel cycle facilities did not reach the new standard, and some NPPs did not establish procedures for the prevention and mitigation of severe accidents. Relevant departments and enterprises on these issues have quickly organized rectification and have achieved initial results.
"Looking Hope": How to understand and absorb lessons learned from the nuclear accident at Fukushima for China's nuclear power security?
Ye Qichen: It can be seen from the Fukushima nuclear accident that the following improvement measures should be taken, including: strengthening the waterproof and inundation measures of nuclear power plants during extreme natural disasters; increasing emergency water recharge measures during extreme natural disasters; based on the reliability of existing power supplies , increase temporary power supply in case of power outages in the event of extreme natural disasters; increase emergency monitoring devices for spent fuel pools; increase hydrogen monitoring and control facilities in emergency situations; ensure emergency control centers can stay in extreme natural disasters Sex; emergency radiation environmental monitoring and improvement to ensure the reliability of monitoring during extreme natural disasters; establish early warning of external disasters and formulate disaster prevention plans; formulate guidelines for severe accident management, guidance for extreme disaster mitigation and other measures.
China learned lessons from the Fukushima nuclear accident. According to the different levels of construction of nuclear power plants under construction, corresponding measures have been taken to prevent the potential safety hazards caused by extreme natural disasters.
"Looking Hope": What are the aspects of the "advanced advantage" of China's nuclear power?
Ye Qichen: At present, China's nuclear power generation units mostly use new models from the 1990s onwards, known as the second generation of improved type, and the technical level has reached the international advanced level. The basic realization of independent design, independent manufacturing, independent construction and independent operation, built a complete nuclear fuel supply system. The safety performance of the power plants in operation and construction is greatly improved, core damage probability (CDF), radioactivity early release probability (LERF), and radioactivity release probability (LRF) are close to three generations of safety technology. The annual load factor of the nuclear power plant in operation reaches 85% 90%, which is basically the normal operation except for the time for changing the fuel.
The operation of nuclear power plants is generally safe and nuclear safety supervision is in place. Preventing similar Fukushima nuclear accidents has short-, medium-, and long-term plans and corresponding countermeasures; each nuclear power plant has targeted improvement measures. All nuclear power generators operate at the international level.
At present, there are 15 nuclear power generating units that have been put into operation in the mainland of China. There have never been operational incidents of international nuclear event classification (INES) grade 2 or above, and there have never been incidents that cause pollution or harm to people or the environment. . The level of the radiation environment around the nuclear facilities has always remained within the natural background fluctuation range. Although the number of nuclear power generating units in operation in China has continuously increased, the number of operational incidents has shown an overall downward trend.
The construction of nuclear power plants is progressing well and safely with quality control. The "advanced advantage" of China's nuclear power has obvious features in terms of technological maturity and engineering construction level. It has absorbed domestic and international experience feedback, applied new achievements in current scientific and technological development, and adopted a series of improvements in design and improved The safety level is better than that of existing international similar nuclear power plants. At the same time, the localization rate of the equipment reached 80%, and the construction quality was strictly controlled.
"The most stringent safety measures must be taken"
"Looking Hope": What are the specific requirements for ensuring nuclear power plants and environmental safety?
Ye Qiyi: There are three basic requirements: First, the safe shutdown of reactors. Once the reactor fails, the reactor will stop. If there is an accident, there is still a nuclear reaction, thermal conductivity will not come out, and the accident will get bigger and bigger; the second is to ensure that the reactor residual heat is exported. The nuclear power plant is different from the thermal power plant. There is no energy to stop the burning of the thermal power plant. The maximum latent heat is there. The nuclear power plant still has some waste heat, which is about 6% of the original power, and it declines to 1% 2% in one day and 3 million kilowatts of thermal power. The 6% of the nuclear power generating units are equivalent to 180,000 kilowatts, which is quite a large number. Therefore, these energy must be derived. Third, the radioactive containment is included. If these three principles are followed, even if any accident occurs, it will not affect the environment.
"Looking Hope": What are the specific security measures adopted in China's nuclear power design?
Ye Qichen: Nuclear power design must adopt the most stringent safety measures. Anti-earthquake design: The site must be far away from faults, have the ability to resist safety shutdown earthquakes, and its annual probability of surpassing is 0.01%. The foundation of the factory building should be placed on the bedrock. The design of China is like this. The design of Japan is very controversial. The east coast of Japan happens to be at the junction of Asia and the Pacific. The Japanese also admitted that a nuclear power plant should not be built here. Americans said that there must not be a nuclear accident like the Fukushima Daiichi nuclear power plant in the United States.
In terms of flood prevention requirements: Within one hour of the earthquake damage at the Fukushima Dai-ichi nuclear power plant, the safety protection system and emergency power supply are working properly. If there is no tsunami, there will be no nuclear accident at the Fukushima Daiichi nuclear power plant. We see that Units 5 and 6 have no problem. In the reference plant plane, the emergency power supply is not problematic for flooded units, and flooded units are problematic, so we have to consider external flood event combinations. Including the highest astronomical tide, probably the largest storm surge (typhoon), tsunami, sea level rise, storm floods, broken dyke upstream, and wave effects, the probability of surpassing is 0.1%, making the plant floor higher than the benchmark flood level, ie dry site. What is a dry site? It is in front of the largest flood that it cannot be flooded.
Power reliability: Two main plant transformers for each unit, supplying power from the main network; one dedicated back-up power supply and two standby plants; two nuclear-grade emergency diesel generators providing emergency power; An additional diesel generator provides backup emergency power.
Anti-explosion measures: A hydrogen concentration measuring device is provided to monitor the hydrogen concentration; a mobile hydrogen complex device is provided, and a non-active hydrogen complex device is added so that hydrogen recombination can be performed at any time.
To prevent the overpressure failure of the containment: Set up a containment filtration and discharge system to filter out radioactive impurities, aerosols, and elemental iodine, and then filter through the metal wool to discharge it into the atmosphere to prevent overpressure of the containment vessel and to avoid environmental pollution.
To prevent overpressure of pressure vessels and high-pressure melt-reactors: Set a pressure regulator to quickly relieve the pressure of the pressure vessel under severe accident conditions.
In addition to these measures, a bulk water injection system is now being developed to prevent the core melt from leaking out of the pressure vessel.
To achieve a safe and efficient development of nuclear power, "Viewpoint": The choice of nuclear power technology line is a topic of debate. What are the major considerations in the selection of China's technology route?
Ye Qichen: China's long- and medium-term nuclear power development plan (2005-2020) has identified "adhere to the development of millions of kilowatts of advanced pressurized water reactor nuclear power plant" and "in accordance with thermal neutron reactors - fast neutron reactors - controlled nuclear fusion reactor three steps" The nuclear power development strategy will enable China to realize the autonomy of advanced PWR nuclear power project design, equipment manufacturing, engineering construction and operation management as soon as possible, and form a comprehensive capacity for the construction of Chinese brand advanced nuclear power plants in batches to realize the leap-forward development of nuclear power technology. World advanced level of nuclear power.
At present, the technical route for the development of nuclear power in China mainly includes several aspects: First, it continues to adhere to the PWR type route; secondly, it uses three generations of advanced PWRs as the basis for the serialization of China’s nuclear power generation units; and thirdly, it builds a proper batch of second generations. The improved PWR units are the third-generation advanced nuclear power technology tracking and researching other reactor types, and the fifth is tracking the research and development of the fourth-generation nuclear power technology and reactor type.
"Looking Hope": In the technical line just mentioned, PWR has been mentioned many times. What are the special considerations?
Ye Qichen: China's rigs that have been built and operated in the past 30 years, except for two heavy water reactors, are all PWR units. At present, the basis for establishing nuclear power technology, manufacturing, and operation in China is also pressurized water reactors. Continuing to adhere to the PWR route is most beneficial to the sustainable development of China’s nuclear power.
From a safety point of view, PWR nuclear power plants have four barriers, and nuclear fission products are fixed within these four barriers.
First, uranium dioxide pellets can contain 98% of fission debris and fission products; after nuclear fission, uranium atoms split into two fragments and two to three neutrons. These two fragments are radioactive and emit radiation like alpha ray, beta ray, gamma ray, etc. After fission, the fragments will not overflow in the uranium dioxide pellets, the pellets will not melt, radioactive fragments will remain in the In the uranium dioxide pellets, uranium dioxide itself plays a role in containing fissile fragments, but fission products are random, 2% may be gaseous, 98% fission products are solid, and the gaseous state may run. come out.
Second, the zirconium cladding tube encloses the fuel and the fission products. There is a small space inside. There is a spring in the space. The gaseous fissioners gather at the top and are stored. The shell tube is not broken and the gas will not come out. .
Third, the pressure boundary can contain radioactive high temperature and high pressure coolants. The water within the pressure boundary works at 150 atmospheres. Leakage is not allowed during the work process because the coolant water is radioactive. When the nuclear power plant was put into operation, it was tested at 219 atmospheres, 1.33 times the actual pressure, and no leakage was guaranteed.
Fourth, the containment can withstand external damage, such as tornadoes, aircraft impacts, etc., and can prevent radioactive leakage in case of a serious accident. The inner surface is lined with a 6 mm thick steel lining and welded together. The outside is 1 meter thick prestressed reinforced concrete and is closed during operation.
"Looking Hope": At present, the world's third-generation nuclear power generation of pressurized water reactors is mainly built in China. What has been the improvement in its safety? What are the characteristics?
Ye Qichen: At present, the world's third-generation nuclear power plants under construction are mainly AP1000 and EPR. The third-generation PWR nuclear power plants have altogether 8 units under construction worldwide, and China accounts for 6 units. China is in a leading position. The AP1000's four nuclear power plants are all built in China. The EPR nuclear power unit under construction has a total of four units, one in Finland and still not completed; one in France and two in Taishan, China. At present, Taishan EPR project has been successfully constructed, and No. 1 machine has been hoisted into a full-scale installation stage. It may exceed the progress of French unit engineering.
The AP1000 features passive safety systems, severe accident prevention and mitigation, double containment, full digital instrumentation and advanced control rooms, and modular construction. Its passive safety systems include passive safety and passive residual heat discharge systems, multistage automatic pressure relief systems, and passive containment cooling systems. The design of this system enables the treatment and mitigation of design basis accidents and ultra design basis accidents, and the derivation of post-accident decay heat without depending on the active equipment attached to the power system, and at the same time, the atmosphere becomes the final heat sink without accidental conditions. It is necessary to pump cooling water to remove the heat released during the accident. For the prevention and mitigation of serious accidents, the flooding technology of the reactor cavity, the hydrogen ignition in the containment vessel, and the hydrogen complex system were mainly used.
EPR features high power (1500MWe1700MWe), 4-channel safety system, severe accident prevention and mitigation, fully digital instrumentation and advanced control room, and modular construction. EPR reduces the probability of core melting to 10-6/year or less, and can mitigate the consequences of accidents in the event of a serious accident, without causing radioactive contamination of the environment. Effectively eliminate the environmental impact of radioactive accidents.
AP1000 and EPR nuclear power generation units are nuclear power generators of the new generation developed internationally in the 1990s. From the design stage, they fully considered the prevention and mitigation of serious accidents, and the design safety level was further improved. China is currently digesting and absorbing the three generations of nuclear power technologies it has introduced, developing new three-generation models based on its own experience, and forming the capacity to build large-scale, advanced Chinese nuclear power plants. This will be more conducive to China's nuclear power security, efficient and orderly development.
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