Radiation safety and protection

Nuclear safety: there is no improper radiation hazard. 1n the nuclear facilities and activities, the facilities and activities are fully protected, and there will be no improper radiation hazards to the staff, the public and the environment. 1ncluding nuclear facilities safety, nuclear material safety, criticality safety, radiation safety, radioactive waste safety and nuclear power plant safety

radiation protection: also known as health physics or radiation safety. Science and technology to prevent harmful effects of ionizing radiation on human beings. The applied disciplines of the Department of radiation protection, as the basic disciplines, mainly include: radiation dosimetry, radiobiology, radioecology, radiation shielding, radiation detection, etc; 1t also involves nuclear engineering, meteorology, geology and hydrology, industrial safety, law, education and practical psychology. Radiation protection includes: Principles and objectives of radiation protection; Radiation protection methods: radiation monitoring technology; Radiation protection evaluation and radiation accident emergency. Radiation protection principles and objectives are the basis and starting point of radiation protection; The protection method is the measure that must be taken in order to achieve the protection goal and implement the protection principle; Monitoring technology is the means to test whether the protection method achieves the intended purpose; Protection evaluation is to comprehensively analyze and study whether the protection facilities and methods are in line with the principle of radiation protection optimization and the way to further improve the protection situation

external irradiation: external exposure to human body. X-ray γ Penetrating radiation such as rays and neutrons can cause harm to the whole body or organs of human body. The weak penetrating radiation β Because of its low penetration rate, X-rays only cause damage to the superficial skin and the lens of the eye. 1n general, α Radiation does not cause external exposure to skin, liver and gallbladder. The three principles of time, distance and shielding are usually adopted in the protection of external radiation, that is, controlling the exposure time, increasing the distance from the radiation source and returning enough thick shielding material between the person and the radiation source. For penetrating radiation, it is difficult to shield and easy to cause large dose of radiation. β Bremsstrahlung can be produced by the interaction between ray and matter, so we should pay attention to the shielding of bremsstrahlung. According to the exposure level and its time distribution, all kinds of exposure can be divided into two types. The first type is continuous or intermittent low dose rate and low dose level continuous irradiation; The second type is short-term irradiation with medium or high dose rate and high dose level. According to the size and uniformity of the irradiated parts, there are also differences between total body irradiation and local irradiation, and between uniform irradiation and non-uniform irradiation. Generally speaking, high dose rate whole body irradiation is the most harmful. Low dose of continuous radiation will not immediately affect people’s health, but may induce random effects

internal exposure: internal exposure refers to the exposure of radionuclides entering the body as radiation sources. Radionuclides can enter the human body through inhalation, ingestion, skin or wound. Radionuclides entering the human body are transferred in the body and are constantly reduced due to excretion and radioactive decay (see Figure). The harm of internal irradiation is related to the way, type, physical and chemical form, intake of radionuclide and the metabolic law of this element in the body. Special attention should be paid to the protection of radionuclides with long half-life, slow excretion rate and high toxicity. Different from external irradiation, for internal irradiation, all the energy of weak penetrating radiation can be deposited in the body. 1nternal radiation is continuous in time, so the absorbed dose, equivalent dose and effective dose are used to measure the internal radiation dose. The diagnosis of nuclear medicine in which radionuclides are introduced into the body, the intake of natural radionuclides or radionuclides produced by human activities, and the occupational work will cause internal radiation. The basic principle of internal radiation protection is to prevent or reduce the entry of radioactive substances into the body, and to prevent the possible entry of radionuclides into the body

radiation shielding: radiation shielding is the full name of ionizing radiation shielding. Between the source of ionizing radiation and a certain area irradiated by it, the radiation level in this area can be reduced by using materials that can weaken the radiation. Radiation shielding is a comprehensive subject. 1t involves the interaction between radiation and matter in nuclear physics, health physics, material science and structural engineering. From the specific work content, it includes the determination of radiation source characteristics, selection of shielding materials, calculation of radiation attenuation, shielding heating, experimental shielding, process design of shielding structure and optimization analysis. At present, the shielding science of medium and low energy radiation sources, including radioisotope sources, various kinds of medium and low energy accelerators, X-ray generators and nuclear reactors, is fully mature. As for high-energy particles, such as the shielding of proton accelerator, a large number of secondary radiation, such as nucleon meson cascade, are involved. Due to the complexity and diversity of the process, there are not enough credible experimental data about the differential characteristics of hadron nucleus interaction, so the semi empirical method still plays an important role in the calculation. The radiation protection during space flight is different from that on the ground in many ways, because cosmic ray particles include protons, electrons, electrons, electrons, electrons and so on α Particles, lithium, beryllium, etc. have energies ranging from several keV to several thousand GeV. The fluence rate of charged particles in space varies strongly in space and time, and the secondary radiation generated in the shell and structural parts of spacecraft and human tissue should also be considered. Because the radiation changes with space and time, the radiation weight factor also changes. 1n addition, if we want to adopt a much higher dose limit than the ground occupational exposure in space flight, we must carefully estimate the possible radiation risk

radiation monitoring: radiation monitoring is used to evaluate and control radiation or radiation exposure of radioactive substances, and analyze and interpret the measurement results. 1n order to evaluate the effect of the practice with radiation or the facilities producing radiation on people, it is necessary to estimate the amount of radiation hazard equal to the effective dose and equivalent dose. However, these quantities can not be measured directly, so they must be estimated according to a certain model according to other quantities that can be measured directly or indirectly. The results of radiation monitoring are indispensable data for estimating the radiation dose to the staff and the public, confirming the safety procedures of the workplace and the environment, conducting radiation safety assessment and radiation protection optimization analysis, and also the basis for taking radiation protection and safety management measures. These data can also be used to confirm the problems existing in operation or equipment defects, find out the signs of accidents, so as to take timely preventive measures to prevent the occurrence of major accidents. According to the nature and purpose of radiation monitoring, radiation monitoring can be divided into routine monitoring, task related monitoring and special monitoring; According to the monitoring objects, it can be divided into place monitoring, environmental monitoring, effluent monitoring and personal monitoring. For all practices and facilities with radiation, routine and emergency monitoring plans should be formulated according to specific conditions. The usual routine test plan should include the following contents: (1) monitoring type, purpose and requirement( 2) The amount of radiation that needs to be measured directly or indirectly, the amount to be estimated and its estimation model( 3) Corresponding radiation management standards and implementation limits( 4) Measurement scheme, including measurement methods, measuring instruments and equipment used( 5) Measurement frequency( 6) Requirements for measurement records, preservation and destruction of records( 7) Procedures for reviewing and revising the monitoring plan( 8) Monitoring quality assurance measures

radiation injury: the harmful effects of various types and procedures caused by ionizing radiation. Radiation can cause various damage effects on human body at molecular, subcellular, cellular, tissue and organ levels. Among them, the light ones have no obvious effect on life activities or only have some functional changes, the heavy ones cause reversible or irreversible damage, and the serious ones cause death. Clinically, the observable radiation damage is collectively referred to as radiation induced diseases. These diseases can appear in a few days or weeks after irradiation, which is called early effect. They can also appear in half a year, which is called late effect. Radiation damage can occur in the subject itself, which is called somatization effect. 1t can also occur in the offspring of the subject, which is called heredity effect. According to the concept of modern radiation protection, radiation damage can be divided into deterministic effect and stochastic effect. Deterministic effect refers to the effect that the severe procedure and probability of occurrence change with the irradiation dose. There is a dose threshold, and the irradiation dose can be controlled below the threshold to prevent its occurrence, such as acute and chronic radiation sickness caused by whole body irradiation, skin, eye lens and other damage effects caused by avoiding part irradiation. Random effect socializing refers to the effect that the probability of occurrence (in rather than severe procedures) changes with the radiation dose, and there is no dose threshold

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