Criteria for Siting Nuclear Power Plants

There have been some successful recent moves towards international uniformity in legislation for nuclear liability. However, there has been less success in obtaining uniform standards in the related field of reactor siting criteria and safety. Different approaches to safety and siting have evolved separately in the large industrial countries which have nuclear energy programmes. Many more nations, including developing nations, will have nuclear power programmes within the next decade and some uniformity in safety standards and siting criteria is highly desirable. There are two broad categories of national siting criteria: in one, sites are chosen on the basis of limiting reference doses used in conjunction with a maximum credible accident and in the other, sites are classified according to density of population. A suitable basis for uniformity can be found in criteria based on reference doses to the whole-body, thyroid and possibly total population. There is general agreement on the use of a whole-body reference dose of 25 rem which represents a fourth-order risk. This value also agrees with recommended action level doses. Thyroid reference doses up to 300 rem to adults are used. In this environment children would be exposed to a second-order risk of developing thyroid carcinoma. It is suggested that the thyroid reference dose should represent a risk to the individual equivalent to that of the whole-body .reference dose and should as far as possible be consistent with recommended action level doses. On this basis the thyroid reference dose should not exceed 50 rem to an infant. It is suggested that an accident based on the coincidental unrelated failure of not less than two systems (such as the primary-circuit piping and the emergency cooling system) be used in conjunction with the reference doses for assessing sites. (author)