This chapter contains introductory discussions of the following topics:

• Natural and anthropogenic sources of ionizing radiation in the environment

• Ways in which both stable nuclides and radionuclides can be used as tools to study processes that occurred in the paleoenvironment, to determine the age of materials as old as the earth, and to serve as tracers to study physical, chemical, and biological processes

• Utilization of nuclear fission as an energy source that does not generate large quantities of CO2, SO2, or NO* by the combustion of carbon-containing fuel, but does generate radioactive waste

• Production, testing, and proliferation of nuclear weapons

• Nature and management of radioactive waste

• Hazards, benefits, and regulation of sources of ionizing radiation

• Accidents that have resulted in the release of radionuclides into the environment

Because certain health effects of ionizing radiation (e.g., cancer) are characterized as having no threshold dose, so that their probability increases with cumulative dose of radiation, it is important to consider all sources, internal and external, that could contribute to the dose received by an individual member of the population.1 In the course of daily living, a person may encounter many sources of ionizing radiation in both the indoor environment (e.g., in the home, workplace, and medical and dental facilities) and the outdoor environment (the atmosphere, hydrosphere, biosphere, and lithosphere). Therefore, in this chapter "environment" will mean the total or extended environment (outdoor plus indoor). The total environment is dynamic. Changes, both short-term and long-term, are made by nature with some assistance from the inhabitants of this planet. The inhabitants may thoughtfully or emotionally perceive the changes (especially those discussed in this chapter) as good or bad with respect to the quality of life at the present or in the future or they may simply find them acceptable without evaluation.

Inasmuch as the topics covered in this chapter require use of the concepts, definitions, terminology, and mathematical relationships specific for nuclear chemistry, a knowledge of the material in Chapter 13 is assumed.

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