A Story That Covers Almost A Century

This chapter concerns people and events in a story of radiation, radioactivity, and nuclear energy that covers almost a century.

The term radiation is generally used to denote the emission of any type of ray or particle from a source. If the radiation has sufficient energy to produce ions by either direct or indirect mean, it is called ionizing radiation. This book deals almost entirely with radiation of this kind. It originates in nuclear reactions and processes, appears in the form of cosmic rays, and is produced in laboratories by special devices.

Since the discovery of X-rays by Roentgen in 1895 and the identification of radiation from radioactive substances (alpha [α] and beta [β]-particles and gamma [γ]-rays), the inventory of radiation is gradually being extended. Dozens of types of nuclear and subnuclear particles are presently being produced artificially in laboratories at energies up to 10⁹ electronvolts or more, while cosmic radiation provides a variety of entities at energies up to 10²⁰ electronvolts.

Radioactivity is a property of nuclei to undergo a spontaneous disintegration accompanied by emission of radiations. The first radioelements were discovered by Pierre and Marie Curie in 1898. At present about 80 various radionuclides are known to occur in nature. Since the discovery of artificial radioactivity by Irène Curie and Frédéric Joliot in 1934, more than 2500 radioactive nuclides have been produced by man.

Energy released in a nuclear reaction involving the conversion of mass into energy is called nuclear energy. The fission of the uranium nucleus was discovered in 1939 and the first man-made nuclear reactor was put into operation in the United States in 1942, in Chicago. At the present time, there are more than 300 experimental nuclear reactors operating across the world and about 420 nuclear power plants furnish nearly 12 percent of the global output of electricity. Our era is also characterized by a prolific stockpile of nuclear weapons. Within only 4 decades following the explosion of the first atomic bomb in the desert of New Mexico (U.S.) in 1945, the world*s nuclear armament has been built up to a point sufficient to destroy not only our civilization, but also much of the Earth's capacity to support life.