The 9.0 magnitude earthquake in Japan triggered a tsunami, resulting in hydrogen explosions in units 1, 3, 2 and 4 of the Fukushima Daiichi nuclear power plant one after another, producing nuclear leaks of varying degrees and raising concerns about nuclear radiation. So what exactly is nuclear radiation? What are the hazards? How should we deal with it? Radiation is a type of energy that travels in the form of waves, particles or beams of photons. Nuclear radiation is radiation that comes from the nucleus of an atom. There are three main types of nuclear radiation affecting human beings, namely alpha, beta and gamma rays. alpha and beta rays have large mass and charge, but they are weak in penetrating materials and can cause harmful internal exposure if they enter the human body. gamma rays are similar to x-rays, which are the most penetrating and the least protective, but they are less harmful than both alpha and beta rays for internal exposure. In fact, radioactivity exists everywhere in nature, and we are always receiving irradiation from natural background. There are two sources of natural radiation: one is radiation in the form of high-energy particles, which comes from outer space, collectively known as cosmic rays; the other source is natural radioactivity, that is, radioactive radiation that exists naturally in ordinary substances (such as air, water, soil and rocks, and even food). In addition, people in modern society will also be exposed to various man-made radiation, such as X-ray examination, nuclear examination, radiation therapy and other medical radiation, as well as travel by airplane, wearing luminous watches, watching TV, using microwave ovens and other living radiation, but the irradiation in life are trace amounts, will not cause harm to the human body, so people also ignore its existence. At present, it seems that the chances of the nuclear leakage accident in Japan affecting our country are extremely small, but we should still take precautions and acquire some basic knowledge to deal with it. Iodine protection can be implemented when an accident has or may result in the release of radioactive isotopes of iodine. When more serious nuclear contamination occurs, a certain amount of iodine tablets should be taken systematically for a certain period of time. The main component of iodine tablets is potassium iodide, which is a kind of stable iodine that can block the absorption of radioactive iodine by the human thyroid gland, so that the radioactive iodine can be quickly excreted from the body and achieve the effect of protecting the body tissues. However, iodine tablets can only block the absorption of radioactive iodine and have no effect on other radioactive substances. Is table salt useful for radiation prevention? The iodine content of iodized salt in China is 30 mg/kg. And the iodine content of iodine tablets is 100 mg per tablet. Therefore, prevention of radioactive iodine intake by consuming iodized salt is not possible. Eating iodized salt in excess without taking into account the actual situation and blindly is harmful to the body. If you have been exposed to radioactive substances, you can protect your organism or promote the discharge of radioactive substances through some foods, such as foods with strong antioxidant capacity, such as tomatoes, watermelon and other red fruits containing lycopene; foods rich in vitamins A, C, E and beta carotene, such as various kinds of beans, olive oil and sunflower oil; cruciferous vegetables such as mustard, cabbage and radish; fresh dates, oranges, kiwi and other fresh fruits; cod liver oil, animal liver; chicken, egg yolk; broccoli, carrots, spinach, etc. Foods rich in selenium, such as sesame, malt and astragalus; yeast, eggs, beer; seafood such as lobster and tuna; garlic, mushrooms, etc. Collagen-elastin-rich substances, such as spirulina, kelp, nori, skin and bone marrow of animals, etc. If you are inadvertently exposed to radiation, you should leave the radiation range immediately and change all your clothes immediately, put them in a sealed plastic bag, dispose of them properly and then take a thorough and comprehensive shower to clean them. We can try to analyze the current nuclear leak in Japan. The radioactive substances produced by this nuclear leak are mainly iodine 131 and cesium 137. If there is an outbreak of a large scale radioactive substance leak, then the nuclear power plant should be closed and cordoned off by all means, just like Chernobyl. So it is possible that radioactive dust and water vapor could enter the atmosphere, but it would not be long-term. However, radioactive dust and water vapor travels in the atmosphere with air currents, especially into the stratosphere, and can reach great distances. So it is normal for radioactive material to be measured in our country after the recent nuclear leak in Japan, but the amount is very slight. If a larger amount of contamination occurs, in addition to taking the above measures, on rainy days, try to avoid direct exposure to rain and minimize exposed body surfaces. During the contamination period, take a thorough bath every day after returning home. After the contamination period, if possible, go to the nuclear medicine department of the hospital to have a radioactivity test to ensure that no radioactive material remains in the body.