Hormesis U.: A Review

Before leaving dear old Hormesis U., here is a short review to see if you've got a handle on the curriculum. You should know...

• Elements are identified by the number of protons in the nucleus (atomic number).
• Isotopes of elements have different numbers of neutrons (n + p = atomic weight).
• Atoms of some isotopes are stable, while others are radioactive and, over time, will disintegrate (decay) into other elements of a lower atomic number.
• Alpha and beta particles have a short range (a few inches and a few feet respectively).
• Gamma rays and X-rays can penetrate several inches of steel or feet of concrete.
• The half-life of a radioactive isotope is the time it takes half of the original amount to decay; after thirty half-lives the original amount is considered to be gone.
• The longer the half-life, the lower the activity of an isotope.
• A curie is 37 billion becquerels.
• A pCi is a picocurie and is equal to one-trillionth (10^-12) of a curie.
• Absorbed doses of radiation are measured in rads or grays; 100 rads equal 1 gray.
• Biological doses are measured in rems or sieverts; 100 rems equal 1 sievert.
• The absorbed dose and the biological dose are the same for gamma and X-rays. 
• A fatal acute dose is about 4 sieverts or 400 rems (50% fatalities in thirty days) when received in a relatively short time (a few days or less).
• Radiation sickness occurs at about 1 sievert or 100 rems (50% of those exposed over a short time). 
• Doses below 1 sievert or 100 rems (100,000 millirems) have no immediate biologic effects but are generally thought to increase the risk of cancer in the future.

Thanks for your attendance at Hormesis U. No doubt you'll find the rest of the information on radiation hormesis much more understandable now than when you were a mere freshman. Oh, and be sure to send in your contribution to the Alumni Fund.