As of June 1977, the United States had some 232 nuclear power plants either planned or in operation, with a generating capacity estimated at about 321 million kilowatts. To date, the industrial world has spent over $200 billion in order to produce useful energy from nuclear fission. By all odds, civilian nuclear power is one of the largest technological ventures in history. To many, this massive effort is completely justified: No other single technology offers as much promise for satisfying world energy needs in the years ahead—particularly as fossil fuels dwindle and climb drastically in price. Yet to others, there is no single technology which raises such serious questions of risk to public health and safety.