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给科盲文革余孽老道说说放射性,U235的 放射性主要是阿尔法射线,连皮肤都穿不透
送交者:  2016年10月17日02:04:26 于 [世界时事论坛] 发送悄悄话

Radiation Basics

Radiation is energy given off by matter in the form of rays or high-speed particles. All matter is composed ofatoms. Atoms are made up of various parts; the nucleus contains minute particles called protons andneutrons, and the atom's outer shell contains other particles called electrons. The nucleus carries a positive electrical charge, while the electrons carry a negative electrical charge. These forces within the atom work toward a strong, stable balance by getting rid of excess atomic energy (radioactivity). In that process, unstable nuclei may emit a quantity of energy, and this spontaneous emission is what we call radiation.

For additional information, see the following topics on this page:

Physical Forms of Radiation

As previously indicated, matter gives off energy (radiation) in two basic physical forms. One form of radiation is pure energy with no weight. This form of radiation — known as electromagnetic radiation — is like vibrating or pulsating rays or "waves" of electrical and magnetic energy. Familiar types of electromagnetic radiation include sunlight (cosmic radiation), x-rays, radar, and radio waves.

The other form of radiation — known as particle radiation — is tiny fast-moving particles that have both energy and mass (weight). This less-familiar form of radiation includes alpha particlesbeta particles, andneutrons, as explained below.

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Radioactive Decay

As previously indicated, large unstable atoms become more stable by emitting radiation to get rid of excess atomic energy (radioactivity). This radiation can be emitted in the form of positively charged alpha particles, negatively charged beta particlesgamma rays, or x-rays, as explained below.

Through this process — called radioactive decay — radioisotopes lose their radioactivity over time. This gradual loss of radioactivity is measured in half-lives. Essentially, a half-life of a radioactive material is the time it takes one-half of the atoms of a radioisotope to decay by emitting radiation. This time can range from fractions of a second (for radon-220) to millions of years (for thorium-232). When radioisotopes are used in medicine or industry, it is vital to know how rapidly they lose their radioactivity, in order to know the precise amount of radioisotope that is available for the medical procedure or industrial use.

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Nuclear Fission

In some elements, the nucleus can split as a result of absorbing an additional neutron, through a process called nuclear fission. Such elements are called fissile materials. One particularly notable fissile material is uranium-235. This is the isotope that is used as fuel in commercial nuclear power plants.

When a nucleus fissions, it causes three important events that result in the release of energy. Specifically, these events are the release of radiation, release of neutrons (usually two or three), and formation of two new nuclei (fission products).

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Ionizing Radiation

Radiation can be either ionizing or non-ionizing, depending on how it affects matter. Non-ionizing radiation includes visible light, heat, radar, microwaves, and radio waves. This type of radiation deposits energy in the materials through which it passes, but it does not have sufficient energy to break molecular bonds or remove electrons from atoms.

By contrast, ionizing radiation (such as x-rays and cosmic rays) is more energetic than non-ionizing radiation. Consequently, when ionizing radiation passes through material, it deposits enough energy to break molecular bonds and displace (or remove) electrons from atoms. This electron displacement creates two electrically charged particles (ions), which may cause changes in living cells of plants, animals, and people.

Ionizing radiation has a number of beneficial uses. For example, we use ionizing radiation in smoke detectors and to treat cancer or sterilize medical equipment. Nonetheless, ionizing radiation is potentially harmful if not used correctly. Consequently, the U.S. Nuclear Regulatory Commission (NRC) strictly regulates commerical and institutional uses of nuclear materials, including the following five major types of ionizing radiation:

Penetrating Power of Radiation

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Alpha Particles

Alpha particles are charged particles, which are emitted from naturally occurring materials (such as uranium, thorium, and radium) and man-made elements (such as plutonium and americium). These alpha emitters are primarily used (in very small amounts) in items such as smoke detectors.

In general, alpha particles have a very limited ability to penetrate other materials. In other words, these particles of ionizing radiation can be blocked by a sheet of paper, skin, or even a few inches of air. Nonetheless, materials that emit alpha particles are potentially dangerous if they are inhaled or swallowed, but external exposure generally does not pose a danger.


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  愚蠢外行,核废料不是U-235,乏燃料里乏的是U-235  /无内容 - 道友 10/17/16 (104)
    当年切尔诺贝利核电站泄漏的核污染相当于原子弹的400倍  /无内容 - 道友 10/17/16 (94)
      整个又是扯蛋,那是过热爆炸,和储藏核废料一样吗?  /无内容 - x-file 10/17/16 (129)
        让无知文科生见识一下储藏核废料如何过热爆炸 - 道友 10/17/16 (159)
          蠢蛋,把半个世纪前的事情拿来,早变了,无知白痴 - x-file 10/17/16 (107)
            玻璃化只解决一部分问题,否则美国也不会再研究 - 道友 10/17/16 (118)
              那你还不如天天担心天上掉块陨石砸头上呢,  /无内容 - x-file 10/17/16 (124)
    结果20年后毛因当年接触放射性死于肺癌!  /无内容 - 道友 10/17/16 (95)
      文科把违反安全规定的蠢事那来秀脑残,可笑!  /无内容 - 道友 10/17/16 (92)
        放射性的东西进入空气,你说它能飞多远? - x-file 10/17/16 (114)
          你对放射性物质的理解局限在某种粒子上,真是无语了  /无内容 - 道友 10/17/16 (102)
            自己无知还说别人无知,还有比你这文科生更可笑的么?  /无内容 - 道友 10/17/16 (115)
              你不懂连百度一下什么是放射性污染都不会?  /无内容 - 道友 10/17/16 (102)
                你蠢的要命,污染的带有放射性物质的污染,不是射线的污染 - x-file 10/17/16 (116)
                  你终于搞明白放射性污染不是放射线了么? - 道友 10/17/16 (101)
                  我就知道你说不出来,多点炭你知道是在骗钱,核废料一样  /无内容 - x-file 10/17/16 (124)
                    原子弹,核电站,爆炸,那是因为放射性物质到处都有 - x-file 10/17/16 (131)
                      要不要脸,百度后才搞明白,还反问人家懂了么? - 道友 10/17/16 (109)
                        靠,放射性物质放桶里能飞出来吗?哈,蠢的要死。  /无内容 - x-file 10/17/16 (130)
                          没知识真可怕,老道告诉你放射性物质如何从桶里出来 - 道友 10/17/16 (128)
                            哈哈,蠢的,还中子。所以要放储藏场,不放停车场。  /无内容 - x-file 10/17/16 (108)
                      在中国原子弹试验场附近找个山,挖个洞,核废料放进去 - x-file 10/17/16 (125)
                        如你文科生所想,那么中国危险了 - 道友 10/17/16 (123)
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