INSAG has established four specific safety principles applicable to the siting of a NPP. They address the following issues: the external factors affect­ing the plant; the radiological impact on the public and the local environ­ment; the feasibility of emergency plans; and the ultimate heat sink provision (INSAG, 1999).

The principle for the external factors affecting the plant is formulated as follows:

Principle 1: The choice of site takes into account the results of the investigation

of local factors that could adversely affect the safety of the plant.

This principle recommends the identification of local factors which must be considered in the design of the plant. They are generally classified into two groups: natural events and those created by human activities. Among the first, the characterization of seismic events and geological, hydrological and meteorological extreme disturbances are the most relevant. Among the second, contaminations, explosions and deflagrations of flammable and toxic gas releases in the proximity of the plant are the major concerns. The studies are aimed at evaluating the expected frequency of these natural phenomena and human-induced acts as a function of their magnitude. The designers need the magnitudes and characteristic parameters of all these natural and human-induced events to be sure that they will be properly included in the design basis in such a way that the plant will cope with the phenomena under consideration.

The principle concerning the plant’s radiological impact on the public and the local environment is presented as follows: