1.   Low-level waste is primarily the product of industrial and medical use of radioactive substances.

2.   The activity of a radioactive substance is the number of nuclei Decaying per second.

3.   The original plan was to encase a small amount of a radioactive substance in a protective steel container.

4.   The half-life of a radioactive substance is the time interval taken for the radiant species present to lose half its radioactivity.

5.   Americium, a radioactive substance created by plutonium when it gives off its radiation, has already turned up in the river, she said.

6.   And in hundreds of cases, very small amounts of radioactive substances were fed to or injected into patients.

7.   And unlike most radioactive substances, it retains its potency for hundreds of thousands of years.

8.   Army regulations required medical screenings for soldiers exposed to radioactive substances, but the military failed to provide them.

9.   At least nine other patients at other universities and hospitals around the country received similar single injections of various radioactive substances.