Anthony Sanders, age 12, of Sioux City, Iowa, for his question:
What is uranium?
Uranium is the most important fuel used to produce atomic energy. This makes it the power source of the future when atomic energy will b e used to generate our electricity. It is also the servant of the research scientist and its usefulness in the medical profession has just begun. In pure form, uranium is a silvery white metal. When it zoomed to fame with the atomic age, prospectors went searching for it as they once searched for gold.
Experts have estimated the amount of uranium present in the earth’s crust to a depth of twelve miles. There may be ten thousand million, million tons of the precious element 10, followed by 15 zeros. This means that it is more plentiful than gold. However, it is much harder to find. In fact, the search for uranium turned out to be the most tiresome treasure hunt in history.
This is because uranium is sparsely scattered. There are traces of it in most granites, lavas and all other igneous rocks but, oh, such tiny traces. Perhaps these rocks will become useful ores when we have discovered better ways to extract their treasure. For the present, we must use ores rich in uranium. These deposits are few and far between.
The useful uranium ores at present are pitch blende, uraninite, carnotite, uranophane and autunite. A deposit of dark waxy pitch blende near Canada’s Bear Lake yields 10% uranium. A deposit of the same ore in the African Congo yields 50%. The biggest ore deposit so far found in the U. S. is in the Colorado Plateau. This ore is carnotite, a dark, greenish brown rock. It yields less than one per cent pure uranium but vast deposits of the ore make mining profitable. Other uranium ores are present in Massachusetts and the Carolinas.
A bar of silvery white uranium is by no means as calm as it looks. For it is a radioactive substance. Certain of its particles are breaking into smaller particles and giving off streams of radioactive energy as they do so. We have only recently discovered this amazing process and got a dim idea of how its tremendous energy can be put to work for us.
One small item provided the scientists with a calendar to help them date the age of the earth. Radioactive decay progresses at a certain rate. Nothing can slow it or speed it up. A radioactive particle breaks down into smaller particles in a series of stages. Each event takes just so long. The final stage is a special form of lead.
The amount of uranium once present in a rock sample can be determined by the amount of this lead, which is the end of the chain of events. The scientist compares the amount of lead with the amount of radioactive material in the rock. This tells him how long the radioactive decay has been in progress. With this information he can work back in geological time and tell when the rock was formed. This gives him an idea of the age of the earths crust.