Part 7

When ancient writings about Biblical times, called the Dead Sea Scrolls, were found, they were wrapped in linen. The linen, made from the fibers of the flax plant, was tested for carbon-14. It was found to be about 2,000 years old. The same method has been used to find the age of ancient wood, leather, cloth, bones--and even mummies!

Radioisotope tracers have been of great benefit to farmers. Mixed with fertilizers, they can be followed with a Geiger counter to see just how the plant uses the fertilizer and how fast. Tracers have shown how certain feeds make animals grow fatter. They help in the study of milk production by cows, egg production by chickens, and growth of wool on sheep.

Perhaps the most important of all tracer uses is in medicine. Radioactive iodine, or iodine-131, is used to find diseases of the thyroid gland. The patient swallows a small dose of the tracer and a counter shows how fast it is taken in by the thyroid gland. This shows how active the gland is. Tracers also help to find brain tumors. And they can be used to follow the circulation of the blood. If an artery is blocked, a person may die because his blood can't circulate. A counter can find the trouble spot and help save a life.

Radioisotopes which are used as medical tracers are not harmful to the body. They are carefully selected to have a very short half-life. Their radioactivity is gone before it can do damage. Also, they are used in tiny quantities.

While radioisotopes do wonderful jobs as tracers, they can do some other very interesting things, too. Let's see what some of them are.

ATOMS TO CHANGE ATOMS

When the rays of a radioactive substance strike the atoms of another substance, they may cause changes. We call the exposure to rays irradiation (ir-rade-ee-AY-shun). One of the changes caused by irradiation is called ionization (eye-on-i-ZAY-shun).

Radioisotopes do many important jobs for us by irradiation. In industry, certain petroleum and other materials are changed by irradiation into special fuels, oils, and even synthetic rubber.

Irradiation is used to improve the quality of plastics and to vulcanize rubber. It used to take several hours to vulcanize with heat. A few minutes of irradiation does the same job.

The food industry has begun to experiment with irradiation as a new way to sterilize food. Items which normally spoil quickly, such as hamburger, sausage, cheese, and bread, are exposed to radiation. The rays destroy all of the bacteria that cause food to spoil. The food is immediately sealed in airtight plastic bags. It will remain perfectly fresh for months--or even years. This process may make the canning or freezing of food completely unnecessary.

Even foods which generally keep well, such as onions or potatoes, can be helped by irradiation. The treatment kills any insects that might be in the sack, and also keeps the vegetables from sprouting. A treated potato will keep for a very long time. A number of experiments have been done with potatoes. Before long you will probably see irradiated potatoes for sale in your market.

Irradiation can even improve food crops and other plants while they are still being grown. Changes caused by the rays have already created new and better varieties of corn, peanuts, and oats. The same dose of irradiation works in another way, too--it kills the insects which damage the crops.

Irradiation used in certain medicines can destroy a patient's diseased tissue. Many forms of cancer are treated by this method. In some cases, the patient is injected with a radioisotope. In other cases, he is just exposed to its rays, which are projected from a special machine. Sometimes, tiny bits of isotope, called seeds, are actually placed directly in the cancer. Other patients are asked to drink the isotope in a special preparation called a "radioactive cocktail."

Besides their many uses as tracers and irradiators, isotopes have great value as substitutes for expensive X-ray machines. The rays can pass through many materials and, by making a picture on a film underneath, can show differences in thickness or other flaws. Some of the materials that are inspected this way are sheet metal, paper, rubber, and plastics. Also, piston rings for auto engines, and airplane engine valves.

Doctors, too, can use radioisotopes instead of X rays. An X-ray machine is a huge piece of equipment which needs a special room and costs thousands of dollars. A radioisotope machine is about the size of a large can of fruit juice and weighs only ten pounds. It can be carried about easily and is most valuable in an emergency or at a place where there is no X ray available.

These are only some of the things that atoms can do for us. Atomic energy is still young. In the years to come, there will be many changes. During your lifetime, the peaceful atom should make the world an easier, healthier, happier place!

APPENDIX

Some other important atomic pioneers:

Chadwick, James: Discovered the neutron in 1932.

Joliot-Curie, Irene and Frederic: Daughter of Marie and Pierre Curie, and her husband. Were the first to make artificial radioisotopes in 1933.

Rutherford, Ernest: Worked out the nature of radioactivity in 1902, discovered the nucleus of the atom in 1911, and split the first atom in 1919.

Soddy, Frederic: Discovered isotopes in 1910.

Urey, Harold: Discovered hydrogen's heavy isotope, deuterium, in 1932.

GLOSSARY

AEC Atomic Energy Commission (U.S.) All atomic energy in the United States is under the control of the AEC. The Commission is in charge of the sources, manufacture, and uses of all fissionable materials. It has important programs of research, building, training, and information.

artificial A chemical element that does not exist in element nature but which can be made in an atomic reactor.

atomic An atomic reactor. furnace

canal A tank of water which is used to hold dangerously radioactive materials in order to protect workers.