Bernice Kohn Hunt

“ Just suppose, the scientists thought, you could split a nucleus and its neutrons would come flying out—and each neutron would strike like a [Pg 34] bullet at another nucleus and make that one split? And all the new flying neutrons would split other atoms? This would be a chain reaction.
If man could produce a chain reaction, there would be such energy as the world never dreamed of! In many different countries, men thought, and dreamed, and worked—the search for the nuclear chain reaction was on! ”

“ Dalton said that all elements are made of atoms, and the atoms of any particular element are always the same. An atom of carbon is always like every other atom of carbon. And, Dalton went on, atoms of different elements have different weights. An atom of carbon weighs more than an atom of hydrogen. An atom of oxygen weighs more than an atom of carbon. ”

“ The last isotope has 142 neutrons and is uranium-234.
The heaviest part of any atom is the nucleus. Protons and neutrons are very much heavier than electrons. And then there is lots and lots of empty space. If the nucleus of the hydrogen atom (which has only one proton) were enlarged to the size of a tennis ball, the electron would be a half mile away!
A whole atom is so tiny that it is almost impossible to imagine anything so small. It would take 250 million of some kinds of atoms to measure one inch. But it would take fifty thousand times as many electrons to cover the same inch! ”

“ When the radioactive element that started giving up 100 particles a second gets down to losing only 50 particles a second, we know that half of its radioactivity has been used up. Radium has a half-life of 1,690 years. Uranium has a half-life of 4,500 million years!
Radioactivity is very interesting, but before we can understand its real importance, we must learn a little about energy.
To most of us, energy means "pep." To a scientist, energy means the ability to do work. Energy is not a "thing." ”

“ One of the hardest to solve is the radioactive exhaust that would come from the reactor. All of the waste products of an atomic furnace are highly radioactive and very dangerous to humans. They can cause serious injury or death. People have to be protected from radioactive materials by heavy shielding of concrete or lead. On a plane, of course, the weight of such a heavy shield would create a difficult problem. The shield would weigh more than the gasoline the atomic fuel replaced. ”

“ A carbon atom looks like every other carbon atom. But a hydrogen atom never looks like a carbon atom.
Atoms are like houses in still another way, too. Even though the building materials used in two houses or two atoms are the same, the finished structure of a house or an atom depends on the way the materials are arranged.
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If an atom could be made large enough for you to see, you might think you were watching a satellite (or a fleet of satellites) going around and around one or more planets.
an atom
The planet—or center of the atom—is called the nucleus. ”

“ You don't look anything like a scrambled egg, either—or a washcloth, or a refrigerator—but they are all made of atoms, too!
Atoms are everywhere, they are everything—and you should learn something about them because you live in the atomic age. ”

“ And that the electrons are very light? Well, the nucleus is so very, very heavy for its tiny size, that it cannot be compared to anything else in the world. If a nucleus were as large as a grain of rice, it would weigh two million tons! Nothing so small could weigh so much unless it were extremely tightly packed together. It takes a great deal of energy to pack anything that solidly.
By the middle of the 1930's, scientists were beginning to think about the huge amount of energy that would be released if the nucleus could be split. ”

“ 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. ”

“ When we burn wood for heat, we are using energy that the tree took from the sun. When we burn coal or oil, we are using the energy of sunlight that was stored many millions of years ago.
All of this energy is stored in the atoms of the wood, coal, or oil. But when we burn these materials for fuel, we release only the energy of the electrons. ”

“ A radioactive atom is really a temporary atom. It is unbalanced and shoots off parts of itself in order to become balanced. As the atom gives up protons, neutrons, and electrons, we say that it decays. ”

“ TINY ATOMS, BIG POWER
Atomic power has grown quickly since that day in 1942. Atomic power plants now make electricity to light large cities in many parts of the world.
Atomic power doesn't make electricity directly. It makes heat. The heat turns into steam. Then the steam turns turbines and the spinning turbines drive the generators which make electric current.
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Ordinary steam power plants depend on fossil fuels—coal, oil, or gas—to make heat. It has been figured out that if only coal were used for fuel, the world's supply would be used up in 350 years. ”

“ Only the U-235 can be used for the chain reaction. But when the flying neutrons from the U-235 strike the U-238, it turns into a new element, plutonium. Plutonium is a fine atomic fuel, just like U-235. In some atomic furnaces there is more fuel at the end of the reaction than the furnace had to start with! ”

“ Now it happens that carbon-14 has a very long half-life—about 5,000 years. So even if a plant or an animal has been dead for 25,000 years, there are still slight traces of carbon-14 left. By measuring the quantity with a counter and comparing it to the quantity in a living plant or animal of the same kind, scientists can tell the age of very old things. ”

“ Once these fuels are used up, there will be no way to replace them. There just won't be any more.
By the early years of the 1900's, some people were beginning to worry about fuel. There wasn't any shortage yet, and there wouldn't be for a long time. There were still new coal mines and new oil wells being discovered. But some day, the last one would be discovered, the fuels would be all used—and then what?
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As new industries developed all over the world, the need for power grew—and so did the worry. ”

“ Energy never disappears, but it can be changed from one form to another.
When you swing a bat and wallop a ball, part of the energy you use makes the ball whiz through the air. If you use energy to clap your hands, part of the energy is changed to sound, and you hear a noise. ”

“ The little satellites circling around the nucleus are always electrons.
Ordinary atoms always have the same number of protons as they do of electrons. This number is called the atomic number. No two elements have the same atomic number. It is the number of protons and electrons that tells us what kind of atom it is. When there are two protons in the nucleus and two electrons circling around it, we know that we have an [Pg 27] atom of helium. If it doesn't have two protons and two electrons, it isn't helium.
helium atom
A helium atom also has two neutrons in its nucleus. ”

“ There is the same big stack of atomic fuel—usually uranium—with control rods sticking out of holes in the fuel bars. Just like Fermi's pile, when the control rods are pushed in they soak up the flying neutrons and there [Pg 43] is no reaction. When the control rods are pulled out, the chain reaction takes place.
Pressurized Water Reactor
One of the curious things about a chain reaction is that it won't work if the neutrons are flying too fast. ”

“ There will be no worry about running out of fuel. Such things as head winds, long flights across water, and fuel leaks will no longer be threats to the safety of plane passengers. And when the shielding, problem is solved, instead of carrying 50 tons of gasoline, a big plane will be able to carry 50 tons more of people or cargo. ”

“ 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. ”

“ Atomic reactors are already in use on ships and submarines and they may soon be used for other types of transportation. Experiments have been made on atomic tractors which would pull long trains of sleds in the Arctic. ”

“ They named the new element radium.
The Curies and other scientists were very excited. Here were three elements—uranium, thorium, and radium—all giving off powerful rays. Where did the rays come from? Scientists were sure they could only come from the atoms of the elements themselves. But how could that be? There couldn't be anything smaller than an atom. Or could there? The scientists didn't know. It was a real mystery.
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4
WHAT'S IN AN ATOM? ”

“ These isotopes are called radioisotopes.
Some radioisotopes are made on purpose by putting certain elements into a reactor. But many radioisotopes are made in all atomic reactors as a natural product of the chain reaction. After the fuel has been used, the radioisotopes are removed from the ashes.
Most elements have at least one radioisotope and many have several. They have thousands of important uses and new ones are found every day.
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Geiger counter
There are a few properties of radioisotopes which make them useful. ”

“ 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. ”

“ They hit the new atoms at such great speed that they just bounce off and keep going. In order for the neutrons to do their splitting job, they have to be slowed down. Fermi used graphite bricks for this purpose. ”