Content area
Full Text
Since the terrorist attacks of September 11, Americans have had to learn to discriminate between real and imagined risks in many areas. When it comes to domestic nuclear terrorism--a subject that has been touched recently by highly speculative journalism--making that distinction requires knowing some nuclear fundamentals.
Based on science, what should Americans worry about? Is radiation always dangerous? How do we protect ourselves? Could terrorists unleash a Chernobyl on our soil? Could nuclear waste dumps or power plants be transformed into atomic weapons? Could terrorists make a "dirty" bomb capable of widespread contamination and deaths from radiation? Could they steal an American nuclear weapon and detonate it?
The Energy Department's nine national laboratories have begun an extensive review of counterterrorism, including the vulnerability of U.S. nuclear sites and materials. Some findings may remain undisclosed for security reasons; others may be made public-soon, one hopes. Meanwhile, here are some basics.
Radiation
Radioactive materials contain unstable atoms, radionuclides, that emit excess energy as radiation, invisible but detectable by instrument. Some atoms lose their energy rapidly; others remain dangerous for thousands, even millions of years. Certain forms of radiation are more hazardous to humans, depending on the type of particles emitted.
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), composed of scientists and consultants from 21 nations, provides comprehensive evaluations on sources and effects of radiation as the scientific basis for estimating health risk. UNSCEAR's reports are almost universally considered objective and reliable. It recently listed annual average exposures per person worldwide.
Natural background radiation: 240 millirem worldwide (300 millirem in the United States).The earth's core is a natural reactor, and all life evolved within a cloud of radiation stronger than background radiation is today. Cosmic rays, sunlight, rocks, soil, radon, water, and even the human body are radioactive-blood and bones contain radionuclides. Exposure is higher in certain locations and occupations than in others (airline flight personnel receive greater than average lifetime doses of cosmic radiation).
Diagnostic medical radiation: 40 millirem (60 millirem in the United States). This is the largest source of manmade radiation affecting humans. Other common manmade sources include mining residues, microwave ovens, televisions, smoke detectors, and cigarette smoke-a pack and a half a day equals four daily chest x-rays.