Radiation protection and nuclear power plant safety
Release time:2024/4/12
Tourist volume:2614
Radiation exists throughout the entire universe. Radiation protection is an applied discipline that studies the protection of human and other biological populations from or to a lesser extent from radiation hazards. Radiation is divided into two categories: ionizing radiation and non ionizing radiation. α Radiation β Radiation γ Radiation, X-rays, protons, and neutrons belong to ionizing radiation, while infrared, ultraviolet, microwave, and laser belong to non ionizing radiation. In the field of nuclear energy, people are mainly concerned about the potential health effects of ionizing radiation and its protection. Ionizing radiation is commonly referred to as radiation or radiation exposure.
Throughout human history, humans have been exposed to natural sources of ionizing radiation, including cosmic rays and radiation generated by radioactive isotopes on Earth. In fact, radiation is everywhere, including food, houses, the sky, the earth, mountains, rivers, plants, and even people's bodies. The collective radiation dose received by humans mainly comes from natural background radiation (about 76.58%) and medical (about 20%), while the radiation dose generated by nuclear power plants is very small (about 0.25%). On a global scale, the average annual radiation dose of natural background radiation to individuals is about 2.4 millisieverts, with some regions having much higher levels of natural background radiation than this average.
The radiation exposure in the field of nuclear energy applications comes from various radioactive nuclides produced during the operation of nuclear power generation devices (such as nuclear power plants). Due to the presence of trace amounts of radioactive nuclides in coal, coal-fired power plants also emit radioactive substances into the environment during operation. In terms of radiation exposure, China's coal-fired power fuel chain (from mining to power generation) generates 50 times more radiation exposure to the public than nuclear power fuel chains of the same power.
On the basis of extensive theoretical and experimental research on the mechanisms of health hazards caused by radiation, people have established an effective radiation protection system and continuously developed and improved it. At present, the three principles of radiation protection commonly adopted internationally are: legitimacy of practice, optimization of protection levels, and personal dose limits. The legitimacy of practice requires that the benefits brought by any practice accompanied by radiation should outweigh the potential harm it may cause; The optimization of protection level refers to maintaining radiation hazards at a reasonable and feasible level as low as possible after considering social and economic factors comprehensively; The purpose of setting personal dose limits is to ensure that every member of society is not subjected to unreasonable radiation exposure. The international basic safety standards stipulate that the personal dose limit for public exposure is 1 millihertz per year, while the personal dose limit for occupational exposure is 20 millihertz per year.
Nuclear power generation is currently the most important way of peaceful nuclear energy utilization. Under normal operating conditions, the radiation dose generated by nuclear power plants to the surrounding public is much lower than the natural background radiation level. In China, national nuclear safety regulations require that the annual radiation dose generated by nuclear power plants to surrounding residents under normal operating conditions shall not exceed 0.25 millisieverts, while the actual radiation dose generated by nuclear power plants is far below this limit. A large amount of research and survey data indicate that the impact of nuclear power plants on public health is far less than some health risks that people often encounter in their daily lives, such as smoking and air pollution. Therefore, the environmental safety of nuclear power plants under normal operating conditions has been widely accepted by people.
The core of nuclear power safety is to prevent the leakage of radioactive fission products from the reactor into the surrounding environment. To this end, the security principle of multi-level defense in depth is adopted. In order to prevent the leakage of radioactive fission products in the reactor core, appropriate physical barriers are installed in the engineering. Nuclear power plants generally have three safety barriers, which are fuel element cladding, primary circuit pressure boundary, and containment.
As of the end of 2002, nuclear power plants worldwide had operated for a total of 10697 reactor years, with a total of two major accidents occurring, namely the Three Mile Island nuclear power plant accident and the Chernobyl nuclear power plant accident. On March 28, 1979, a serious accident occurred at the Three Mile Island nuclear power plant in the United States, causing a portion of the reactor core to melt and collapse. However, due to the pressure boundary of the primary circuit and the containment effect of the safety shell, the leakage of radioactive isotopes into the surrounding environment is minimal, and there is no harm to the environment and public health. Only three power plant staff members were exposed to radiation slightly above the quarterly dose management limit. Among the 2 million residents living within an 80 kilometer radius, the average radiation dose per person is lower than the radiation dose received by wearing a night light meter or watching a color TV for a year. On April 26, 1986, the Chernobyl nuclear power plant accident occurred in the former Soviet Union. This is the most serious nuclear accident in the history of peaceful nuclear energy utilization. Among nuclear power plant workers and accident responders, 28 people died due to receiving very high radiation doses. In order to prevent the public from being exposed to high levels of radiation, 116000 residents near the power plant were urgently evacuated. There are two main causes of the accident. One reason is that during the process of testing how long the generator rotor can continue to supply power based on its own rotational inertia under power outage conditions, the operating personnel seriously violated the operating procedures, cut off all safety control systems, and caused the safety protection system to fail to start. The second is that there are serious defects in the safety design of the reactor (pressure tube graphite moderated boiling water reactor). In April 1996, over 800 experts from 71 countries and 20 organizations held a meeting to evaluate the actual consequences of the Chernobyl nuclear power plant accident that occurred in the former Soviet Union 10 years ago. The evaluation results indicate that only 28 people died from radiation exposure among the staff and personnel assisting in handling the consequences of the accident ("cleanup personnel") at the nuclear power plant. More than 100000 residents evacuated from polluted areas and those still living in less affected areas have received doses similar or lower throughout their lives than those received from natural radiation sources.
In order to ensure the health and safety of the surrounding public in the event of a serious accident or a large amount of radioactive material leakage into the external environment, nuclear power plants must also develop emergency response plans and make corresponding emergency response preparations. Our country's nuclear emergency work implements a three-level management system at the national, provincial, municipal, autonomous region, and nuclear power plant levels, implementing the work policy of "being constantly prepared, actively compatible, unified command, vigorously coordinated, protecting the public, and protecting the environment".
With the deepening of research and the continuous accumulation of operational experience, the operational safety level of nuclear power plants will continue to improve, and advanced nuclear power plants in the future will have a higher level of safety.
Throughout human history, humans have been exposed to natural sources of ionizing radiation, including cosmic rays and radiation generated by radioactive isotopes on Earth. In fact, radiation is everywhere, including food, houses, the sky, the earth, mountains, rivers, plants, and even people's bodies. The collective radiation dose received by humans mainly comes from natural background radiation (about 76.58%) and medical (about 20%), while the radiation dose generated by nuclear power plants is very small (about 0.25%). On a global scale, the average annual radiation dose of natural background radiation to individuals is about 2.4 millisieverts, with some regions having much higher levels of natural background radiation than this average.
The radiation exposure in the field of nuclear energy applications comes from various radioactive nuclides produced during the operation of nuclear power generation devices (such as nuclear power plants). Due to the presence of trace amounts of radioactive nuclides in coal, coal-fired power plants also emit radioactive substances into the environment during operation. In terms of radiation exposure, China's coal-fired power fuel chain (from mining to power generation) generates 50 times more radiation exposure to the public than nuclear power fuel chains of the same power.
On the basis of extensive theoretical and experimental research on the mechanisms of health hazards caused by radiation, people have established an effective radiation protection system and continuously developed and improved it. At present, the three principles of radiation protection commonly adopted internationally are: legitimacy of practice, optimization of protection levels, and personal dose limits. The legitimacy of practice requires that the benefits brought by any practice accompanied by radiation should outweigh the potential harm it may cause; The optimization of protection level refers to maintaining radiation hazards at a reasonable and feasible level as low as possible after considering social and economic factors comprehensively; The purpose of setting personal dose limits is to ensure that every member of society is not subjected to unreasonable radiation exposure. The international basic safety standards stipulate that the personal dose limit for public exposure is 1 millihertz per year, while the personal dose limit for occupational exposure is 20 millihertz per year.
Nuclear power generation is currently the most important way of peaceful nuclear energy utilization. Under normal operating conditions, the radiation dose generated by nuclear power plants to the surrounding public is much lower than the natural background radiation level. In China, national nuclear safety regulations require that the annual radiation dose generated by nuclear power plants to surrounding residents under normal operating conditions shall not exceed 0.25 millisieverts, while the actual radiation dose generated by nuclear power plants is far below this limit. A large amount of research and survey data indicate that the impact of nuclear power plants on public health is far less than some health risks that people often encounter in their daily lives, such as smoking and air pollution. Therefore, the environmental safety of nuclear power plants under normal operating conditions has been widely accepted by people.
The core of nuclear power safety is to prevent the leakage of radioactive fission products from the reactor into the surrounding environment. To this end, the security principle of multi-level defense in depth is adopted. In order to prevent the leakage of radioactive fission products in the reactor core, appropriate physical barriers are installed in the engineering. Nuclear power plants generally have three safety barriers, which are fuel element cladding, primary circuit pressure boundary, and containment.
As of the end of 2002, nuclear power plants worldwide had operated for a total of 10697 reactor years, with a total of two major accidents occurring, namely the Three Mile Island nuclear power plant accident and the Chernobyl nuclear power plant accident. On March 28, 1979, a serious accident occurred at the Three Mile Island nuclear power plant in the United States, causing a portion of the reactor core to melt and collapse. However, due to the pressure boundary of the primary circuit and the containment effect of the safety shell, the leakage of radioactive isotopes into the surrounding environment is minimal, and there is no harm to the environment and public health. Only three power plant staff members were exposed to radiation slightly above the quarterly dose management limit. Among the 2 million residents living within an 80 kilometer radius, the average radiation dose per person is lower than the radiation dose received by wearing a night light meter or watching a color TV for a year. On April 26, 1986, the Chernobyl nuclear power plant accident occurred in the former Soviet Union. This is the most serious nuclear accident in the history of peaceful nuclear energy utilization. Among nuclear power plant workers and accident responders, 28 people died due to receiving very high radiation doses. In order to prevent the public from being exposed to high levels of radiation, 116000 residents near the power plant were urgently evacuated. There are two main causes of the accident. One reason is that during the process of testing how long the generator rotor can continue to supply power based on its own rotational inertia under power outage conditions, the operating personnel seriously violated the operating procedures, cut off all safety control systems, and caused the safety protection system to fail to start. The second is that there are serious defects in the safety design of the reactor (pressure tube graphite moderated boiling water reactor). In April 1996, over 800 experts from 71 countries and 20 organizations held a meeting to evaluate the actual consequences of the Chernobyl nuclear power plant accident that occurred in the former Soviet Union 10 years ago. The evaluation results indicate that only 28 people died from radiation exposure among the staff and personnel assisting in handling the consequences of the accident ("cleanup personnel") at the nuclear power plant. More than 100000 residents evacuated from polluted areas and those still living in less affected areas have received doses similar or lower throughout their lives than those received from natural radiation sources.
In order to ensure the health and safety of the surrounding public in the event of a serious accident or a large amount of radioactive material leakage into the external environment, nuclear power plants must also develop emergency response plans and make corresponding emergency response preparations. Our country's nuclear emergency work implements a three-level management system at the national, provincial, municipal, autonomous region, and nuclear power plant levels, implementing the work policy of "being constantly prepared, actively compatible, unified command, vigorously coordinated, protecting the public, and protecting the environment".
With the deepening of research and the continuous accumulation of operational experience, the operational safety level of nuclear power plants will continue to improve, and advanced nuclear power plants in the future will have a higher level of safety.
