A. ALONSO, Universidad Politecnica de Madrid, Spain

Abstract: This chapter describes the technical requirements to be considered in the selection of a site for a nuclear power plant. The design and operation of the nuclear power plant depend on the site characteristics; the site-derived risks have to be considered in the plant design basis, and the site itself has to bear the risks and detriments coming from the plant. The design has to cope with expected extreme natural phenomena and combinations of those, as well as human — induced events, without impairing the operational safety of the plant. The site has to provide needed requirements such as rejected and decay heat sinks, availability of electrical power supplies, good communications and effective emergency management, including the evacuation of nearby residents.

Key words: site evaluation, site seismicity, extreme meteorology, ultimate heat sink, population density, site parameters, human-induced events.

18.1 Introduction

Site selection for nuclear power plants (NPP) requires the analysis of a set of diverse parameters which are divided into the following five groups: [102] materials. These conventional factors, although relevant, for NPP site selec­tion are not developed further. Some of these elements are considered in the chapter on site and supporting facilities in the IAEA ‘Milestones’ docu­ment (IAEA, 2007a).

Site characteristics which may impact plant safety are essential in the safe design of the NPP. Extreme meteorological conditions, such as hurricanes, tornadoes and heavy rain, hail or snow falls and lightning may produce floods and impair plant accessibility; floods can also be produced by large tides in combination with heavy rain in estuarine waters or by rupture of up-river dams; earthquakes and the ensuing tsunamis may produce damage to buildings and external facilities as well as violent floods in coastal sites. All these events require buildings, water intake structures, external water tanks, electrical grids and electrical transformers to be protected by design. These aspects will be considered in depth.

Man-made external activities offer risks to the safety of the plant. Large explosions and toxic releases in the vicinity of the plant produced, for example, in the transportation of liquefied natural gas or other explosives or gaseous toxic substances by road, rail or waterways have to be avoided and the consequences to the plant mitigated by design. Proximity to har­bours, airports and military installations should also be avoided as they represent a risk to the safety of the NPP. These hazards are also considered in detail.

Extreme natural events, such as the impact of large meteorites, massive volcanic activity or pandemics are not generally considered. There should also be protection against sabotage, but this matter is not considered in this chapter, as it is not site dependent and it is generally prevented by security measures.

The NPP creates risks and detriments to the surrounding population and the environment that have to be previously analysed. The impact of radioac­tive releases during normal operation requires meteorological and hydro­logical dispersion parameters. The transport of contaminants along the terrestrial and aquatic food chain pathways needs to be considered. Demographic parameters are needed to assess the potential doses that dif­ferent population groups may receive and the performance of epidemio­logical studies to determine any potential radiation effects. These risks and detriments are considered.

A major consideration is the protection of the population in case of accidents with radiological effects. The site conditions should facilitate the evacuation of the affected population, the establishment of decontamina­tion and receiving centres and the medical treatment of potential exposures. Population distribution, communication and evacuation routes are relevant aspects of site evaluation. The site requirements for an effective nuclear emergency plan are emphasized.

Most countries have regulated that any major industry or activity has to analyse the environmental impact it may produce. A major environmental impact of the NPP is due to the rejection of heat required by the second law of thermodynamics. The thermal efficiency of NPPs is about one-third, therefore two-thirds of the heat generated has to be rejected to an ultimate heat sink, which could be the atmosphere through different types of cooling towers, or large water bodies such as big rivers, natural or artificial lakes, or the sea in coastal sites. Cooling towers release large amounts of steam to the atmosphere with minor meteorological impacts on the surroundings, and heat rejected to water bodies, causing even small temperature increases, may produce substantial variations in the life and development of aquatic organisms. NPPs also produce chemical impacts, mainly in water bodies; production and releases of conventional waste; an increase in light and heavy traffic, mainly during construction; and a substantial aesthetic impact, mainly if using large cooling towers. These impacts are not considered in detail in this chapter. Such aspects are described in Chapter 8.

All the effects named above require specific studies and consideration. In this chapter safety parameters will receive more attention. The basic scientific basis will be exposed and references to applicable International Atomic Energy Agency (IAEA) standards will be introduced to serve as additional information.