Page 36 - Curriculum Visions Dynamic Book

Nuclear accidents
A nuclear reactor produces the most concentrated radioactive materials in the world, and special precautions need to be taken to ensure safety.
The greatest danger is that the core may become overheated. This might happen if the cooling fluid is not circulating properly or if the control rods or control fluid are not adjusted properly so that too much power is released from the fuel rods. If the reactor gets too hot, the cooling fluid may boil. The bubbles in the cooling fluid are not effective at carrying away heat, so the reactor can then get so hot it begins to melt. Boiling fluid and lack of cooling water were the main causes of the disaster at Chernobyl (see opposite).
To prevent this scenario there are many safety devices that sense increases in temperature and shut the reactor down slowly and safely, as appropriate.
Three Mile Island
A number of releases of plutonium have given rise to great concern. One of the most widely reported occurred after an accident in 1979 on Three Mile Island near Harrisburg, Pennsylvania, where a nuclear
power station accident caused small amounts of plutonium to be released into the air and the water. The plant that caused the trouble has now been sealed up.
Radioactive watches
Women employed during the 1920s as painters of luminescent clock
dials were unwittingly exposed to radium from the paint as they licked their brushes. Many died, either from anaemia or from bone cancer, alerting doctors to the dangers
of radioactivity and subsequent radiation injury. Other types of life- threatening bone disease can be caused by overexposure to X-rays.
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