Concept 1, ionizing radiation: is a kind of radiation produced by having enough energy to make electrons leave the atom. A kind of radiation originates from some unstable atoms, and these radioactive atoms (meaning radionuclides or radioactive isotopes) release secondary and high-energy light quanta (gamma rays) from the nucleus in order to become more stable. The above process is called radioactive decay. For example, the natural nuclides uranium, radon, radium, Q, etc., which exist in nature. Atomic fission, etc., which exists in human activities and in nuclear reactors in nature’s activities, likewise releases ionizing radiation. In the decay process, the main products of radiation are α, β and γ rays. x-rays are another kind of radiation caused by the outer electrons of atomic nuclei. Shandong Institute of Occupational Health and Occupational Disease Prevention and Control, Occupational Disease Section, Li Man 2, alpha particles: alpha particles are positively charged high-energy particles, they are usually emitted by some heavy atoms (uranium, radium) or some artificial nuclides. It loses energy rapidly after passing through the medium and can be blocked by a thin sheet of paper and cannot penetrate very far. However, in penetrating into the tissue (even if it can not penetrate deeply) can cause damage to the tissue. α particles are usually completely absorbed by the outer layer of necrotic skin of the human body, and the radioactive isotopes released from them do not pose a danger outside the human body, however, they will be very dangerous once injected or inhaled into the human body. 3, beta particles: beta rays are a negatively charged, high-speed operation, released from the radioactive decay of nuclide particles. Humans can be exposed to beta rays from man-made or natural sources. It is more penetrating than alpha particles, but causes less damage over the same distance. Some beta rays can penetrate the skin and cause radioactive damage. But once it enters the human body causes more harm. beta rays can be abated by external clothing, blocked or completely blocked by a few millimeters of aluminum foil. 4, γ particles: the same as visible light, X-rays, γ rays is a kind of light quantum. In the process of radioactive decay γ rays are released along with α and β rays. They are neither charged nor mass, but have a very strong penetrating power. Natural nuclide 40 potassium and artificial nuclide 239 plutonium and 137 cesium are the main source of γ rays in the environment. γ rays can easily penetrate the human body, which is very harmful to the human body, several feet thick concrete walls can block γ rays. 5. X-rays: X-rays are high-energy quanta of light produced by the interaction of charged particles with matter. x-rays have many similar properties to gamma rays, but they have different origins. X-rays have atomic internal cause, lower than γ-ray capacity, so the penetrating power is less than γ-ray. x-ray machine in daily life is often used in medicine and industry. Due to its wide range of uses with it, X-rays are the largest source of man-made radiation. A few millimeters thick lead is capable of blocking X-rays. Radiation sources 1.Natural radiation: Humans mainly receive natural radiation from nature. It comes from the sun, cosmic rays and radionuclides that exist in the earth’s crust. Radon overflowing from underground is another important source of natural radiation. Cosmic rays from space include energized light quanta, electrons, gamma rays and X-rays. The main radionuclides found in the earth’s crust are uranium, Q and other radioactive substances. They release alpha, beta and gamma rays. 2.Artificial radiation: radiation is widely used in medicine, industry and other fields. Artificial radiation is mainly used in medical equipment, research and teaching institutions, nuclear reactors and their auxiliary facilities; it is also widely used in people’s daily life, such as luminous watches, glazed ceramics, artificial dentures, smoke detectors, etc.