[1]Words appearing in SMALL CAPITAL LETTERS are defined in the Glossary beginning on page 49. [2]The process of natural radioactive decay is described in the Appendix beginning on page 52. [3]The U. S. War Department program during World War II that developed the first nuclear weapons.
[4]Drawn to scale, the whole age of man is represented by less than the width of the line.
[5]For more information on the structure of atoms, see Our Atomic World, a companion booklet in this series.
[6]From the Chart of the Nuclides, prepared by David T. Goldman, Knolls Atomic Power Laboratory, August 1964.
[7]This decay process proceeds in a series of steps, during which 6 alpha particles and 4 beta particles are emitted. (See Appendix.) [8]Named after their creator, John Napier, a Scottish mathematician (1550-1617), who also invented the decimal point.
[9]It is difficult to determine the half-life of ¹?C exactly. In the early days of ¹?C dating, in order not to delay continued work, an arbitrary value of 5568 years was chosen and this value is still used in calculations.
[10]This means that uranium decays through successive steps in which the entire series emits eight alpha particles. (See Appendix.) [11]Remember, this enormous period of time is a measure of the rate of spontaneous fission, not of the age of ²³?U.
[12]The rhenium-osmium scheme is shown below the dotted line because the method is still in an early experimental stage and its general utility is not yet established.
[13]For more on this family of elements, see Rare Earths, The Fraternal Fifteen, a companion booklet in this series.
[14]For a fuller explanation of the fission process, see Our Atomic World, another booklet in this series.
[15]Neutrons that have had their speed reduced by passing through a moderator (graphite, for example) which is built into every reactor to accomplish this very thing. For more about how this is done, see Nuclear Reactors and Research Reactors, companion booklets in this series.
[16]Note that some radionuclides sometimes decay by one method, sometimes by another. For example, 98.8% of the nuclei of actinium-227 emit a beta particle to form thorium-227; the remaining 1.2% emit an alpha particle to form francium-223; both of these daughter products decay to radium-223.
[17]Some of the protactinium (0.12%) changes by an intermediate step, known as isomeric transition, in which its nucleus shifts to a lower energy state. The process does not alter the remaining parent-daughter progression in the series.
[18]Undergoes both alpha and beta decay, in definite proportion of decay events, as shown.
This booklet is one of the “Understanding the Atom” Series. Comments are invited on this booklet and others in the series; please send them to the Division of Technical Information, U. S. Atomic Energy Commission, Washington, D. C. 20545.
Published as part of the AEC’s educational assistance program, the series includes these titles:
- Accelerators
- Animals in Atomic Research
- Atomic Fuel
- Atomic Power Safety
- Atoms at the Science Fair
- Atoms in Agriculture
- Atoms, Nature, and Man
- Careers in Atomic Energy
- Computers
- Controlled Nuclear Fusion
- Cryogenics, The Uncommon Cold
- Direct Conversion of Energy
- Fallout From Nuclear Tests
- Food Preservation by Irradiation
- Genetic Effects of Radiation
- Index to the UAS Series
- Lasers
- Microstructure of Matter
- Neutron Activation Analysis
- Nondestructive Testing
- Nuclear Clocks
- Nuclear Energy for Desalting
- Nuclear Power and Merchant Shipping
- Nuclear Power Plants
- Nuclear Propulsion for Space
- Nuclear Reactors
- Nuclear Terms, A Brief Glossary
- Our Atomic World
- Plowshare
- Plutonium
- Power from Radioisotopes
- Power Reactors in Small Packages
- Radioactive Wastes
- Radioisotopes and Life Processes
- Radioisotopes in Industry
- Radioisotopes in Medicine
- Rare Earths
- Reading Resources in Atomic Energy
- Research Reactors
- SNAP, Nuclear Space Reactors
- Sources of Nuclear Fuel
- Space Radiation
- Synthetic Transuranium Elements
- The Atom and the Ocean
- The Chemistry of the Noble Gases
- The First Reactor
- Whole Body Counters
- Your Body and Radiation
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