Tuesday, September 7, 2010

Protection From Radioactivity

Radiation hazard is a subject often approached from a highly emotional point of view, probably because radiation cannot be detected by the ordinary human sense. Protection against radiation is possible with insulation (dense concrete, etc), just as is presently done for hot stream pipes or dangerous electrical conductors.

Radiation is always present (background) and is released in substantial quantity by such processes as coal burning and ordinary mining. The international atomic energy agency (IAEA) notes that no serous radiation induced injury or radiation induced death has taken place at any nuclear power plant since the first nuclear power reactor went critical in 1956. this is a remarkable record considering that 274 nuclear reactors, representing 25000 reactor-years of operating experience, were in operation in 1982. coal mining, or even riding in an automobile, is far more hazardous than working in an nuclear establishment. More than 800 nuclear installations around the world have safeguard agreements with the IAEA. This is 98 percent of the nuclear installation outside the nuclear weapon states.

The contamination of gases, liquids and solid by substances emitting, alpha, beta and gamma radiation are all possible and must be guarded against. Shielding of only a fraction of an inch of ordinary material stops alpha and beta particles, but shielding against gamma radiation and neutrons requires massive quantities of dense materials such as heavy concrete, lead, steel, borosilicate glass, or around 7 m of ordinary water. Of course, shielding is not the only problem, containment must also be considered. Gases must not be allowed to escape, and active materials must remain isolated behind the shield in order for them to be effective.

96Sr and 137Cs (fission fragments) are troublesome because of their moderate these isotopes; biological concentration of mercury was the cause of Minamata disease, which led to the outlawing of mercury cell caustic-chlorine manufacture in Japan.

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