year” category, characterized by few immediate casualties of any type, by tens to hundreds of delayed health effects, and by hundreds of millions of dollars in property damage. Therefore, such cases should be considered as characteristic of “catastrophic” nuclear accidents. We infer that a similar type of reasoning may have guided the Nuclear Energy Policy Study Group in concluding that “the consequences of an extremely serious accident are not out of line with other peacetime catastrophes that our society has been able to handle….”75 Damages in the same range as those from dominant nuclear accidents have, after all, been experienced in other industries: refinery and chemical plant fires and explosions, airplane crashes, shipwrecks, and toxic chemical and metal releases.

The assumption implicit (if not explicit) in the reactor safety studies conducted so far is that the equipment and the people operating it and regulating its use behave approximately according to the conditions specified. Nevertheless, there may be shortcomings in the people and equipment. Mistakes, laxity, and incompetence can overcome technological barriers. In the nuclear power industry, as in any industry in which mistakes can have expensive consequences, human errors and inadequacies constitute a significant source of risk that is difficult to quantify. It would seem that the uncertainties in estimations of risk have themselves been underestimated by failing to take these factors into account.

On the other hand, human ingenuity eventually brought the two most serious nuclear power accidents (Brown’s Ferry and Three Mile Island) under control, and this quality has evidenced itself in the prevention and mitigation of many other incidents.

Thus, we find reason to assign an uncertainty to the possibilities calculated for nuclear power accidents, ranging higher or lower than those published, and note as a consequence the great value of maintaining as well trained a work force as possible for the design, construction, operation, maintenance, inspection, and supervision of nuclear power plants.


Safety of Other Reactors Fault-tree, event-tree analysis can also be applied to compare the risks of various reactor systems against one another. The analyses require information that has not yet been assembled for advanced converters or fast breeders: specific designs, recognized design criteria, and results of accident analyses.

The only document produced in the United States on the safety of LMFBR’s and available for study is the draft environmental statement for the Clinch River breeder reactor. Events that might lead to large-scale release of radioactivity to the public are the class-8 and class-9 accidents listed in Table 5–13.

Accidents that form the basis for the plant’s design are grouped in class



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