Nuclear power plants present a hazard to the health and safety of the public because they are subject to accident, such as an explosion, in which harmful substances called radioactivity could be released to the atmosphere as dust and expose a large population to lethal or injurious radiation. The source of this accident hazard is the nuclear reactor, which is the heart of the plant. It generates the nuclear energy for making electricity, and in the process, it also generates the radioactivity as a by-product. This radioactivity builds up in the reactor and is even used as fuel in the case of plutonium, which is perhaps the most potent of all radioactive substances. In order to assess the hazards of nuclear power plants, therefore, we must investigate the accident potential of the various nuclear reactors in use or planned for use. - Introduction.

Arguing that the accident risk of present-day nuclear power plants has not been scientifically established, a nuclear-reactor engineer assesses three major types of reactors being used and developed in the United States and explores the potential consequences of accidents.