A dirty bomb is an explosive designed to spread dangerous radioactive material over a wide area. When people hear "bomb" and "radioactive" in the same sentence, their minds jump to nuclear war pretty quickly. But it turns out that a dirty bomb's primary destructive power would probably be panic, not radiation damage.
A dirty bomb is much closer in power to an ordinary explosive than it is to the widespread destructive force of anuclear bomb．But the fear of contamination could be debilitating, in the same way that 2001'santhraxscare in the United States terrorized much of the American populace, even though only a few people were infected.
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In this article, we'll find out what dirty bombs are and what they do. We'll also explore what might happen if one actually went off in a public area, and consider some of the consequences of this sort of attack.
Conceptually, a dirty bomb (orradiological dispersion bomb) is a very simple device. It's a conventional explosive, such as TNT (trinitrotoluene), packaged withradioactivematerial. It's a lot cruder and cheaper than anuclear bomb, and it's also a lot less effective. But it does have the combination of explosive destruction and radiation damage.
High explosives inflict damage with rapidly expanding, very hot gas. The basic idea of a dirty bomb is to use the gas expansion as a means of propelling radioactive material over a wide area rather than as a destructive force in its own right. When the explosive goes off, the radioactive material spreads in a sort of dust cloud, carried by the wind, that reaches a wider area than the explosion itself.
The long-term destructive force of the bomb would beionizing radiationfrom the radioactive material.Ionizing radiation, which includes alpha particles, beta particles, gamma rays andX-rays, is radiation that has enough energy to knock anorbital electronoff of anatom．Losing an electron throws off the balance between the atom's positively charged protons and negatively charged electrons, giving the atom a net electrical charge (the atom becomes anion). The free electron may collide with other atoms to create more ions. (SeeHow Atoms Workfor more information on subatomic particles.)
If this happens in a person's body, the ion can cause a lot of serious problems, because an ion's electrical charge may lead to unnatural chemical reactions insidecells．Among other things, the charge can break DNA chains. A cell with a broken strand of DNA will either die or the DNA will develop a mutation. If a lot of cells die, the body can develop various diseases. If the DNA mutates, a cell may becomecancerous, and this cancer may spread. Ionization radiation may also cause cells to malfunction, resulting in a wide variety of symptoms collectively referred to asradiation sickness．Radiation sickness can be deadly, but people can survive it, particularly if they receive a bone marrow transplant.
In a dirty bomb, the ionizing radiation would come fromradioactive isotopes(also called radioisotopes). Radioactive isotopes are simply atoms thatdecayover time. In other words, the arrangement of protons, neutrons and electrons that make up the atom gradually changes, forming different atoms. Thisradioactive decayreleases a lot of energy in the form of ionizing radiation. (SeeHow Nuclear Radiation Worksfor details on radiation and radioactive isotopes.)
我们暴露于小剂量的电离辐射all the time -- it comes from outer space, it comes from natural radioactive isotopes, it comes fromX-ray machines．This radiation can and does cause cancer, but the risk is relatively low because you only encounter it in very small doses.
A dirty bomb would boost the radiation level above normal levels, increasing the risk of cancer and radiation sickness to some degree. Most likely, it wouldn't kill many people right away, but it could possibly kill people years down the road.
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