As with any other large industrial installation, a nuclear power plant, fuel cycle facilities and associated activities produce substantial non-radiological physical and chemical impacts on their surroundings during pre-construc­tion, construction, operation and dismantling. These impacts are generally considered in an environmental report, a licensing requirement in most countries. The USA NRC requirements are among the most developed regulations, and they also include economic and radiological impacts (NRC, 1984).

Nuclear regulatory authorities are not the only regulators intervening in this process; other local, regional and state authorities also participate in the review, generally in a coordinated manner, to verify compliance with other regulations on environmental protection, such as those related to air and water quality and on land use.

For non-radiological impacts, any environmental impact study starts by describing the affected territory and its current use, industrial and recrea­tional development; the surface and ground water hydrology and the use given to such waters; the meteorology and air quality, and the terrestrial and aquatic ecology, amongst the major aspects. With this knowledge, the impacts during pre-construction and construction activities are analysed, generally divided into three levels of significance: small, moderate, or large. For all these impacts, mitigation measures are also considered, though, in such an analysis, unavoidable adverse environmental impacts can be found for which no practical means of mitigation are available.

During pre-construction and construction activities, the major unavoid­able environmental impact would be the land to be occupied by the plant buildings and the land used temporarily for construction purposes; addi­tional land will also be needed to build new or widen existing roads and electrical energy corridors. The high energy intensity of nuclear power does not need additional land for storing new and used fuel, as is the case for fossil fuels (mainly coal). Considerations should also be given, among other things, to the use of water and construction materials; the effects that exca­vation and dewatering will produce on groundwater aquifers; the ecological impact on terrestrial and aquatic losses; and the increase of traffic and health effects due to fugitive dust, noise and transportation. The purpose of these considerations is to evaluate them and to define mitigation and con­trols aimed at lessening the adverse impacts.

The land used for buildings will be considerably improved by trees, gardens and lawns. When the plant ends its useful lifetime, decommissioning will restore the site and make it useful for other purposes (decommissioning is considered in detail in Chapter 24 of this book). The operation of nuclear power plants is very clean; negligible amounts of conventional pollutants are released and solid conventional waste is very limited. Non-radiological health impacts to members of the public, including etiological agents, noise, electromagnetic fields, occupational health, and transportation of materials and personnel are minimal and well controlled to verify compliance with applicable regulations.

During operation, the major non-radiological impacts are the use of water to cool the condenser and the effects that heat rejection produces in the affected water bodies. Nuclear power plants have a low thermal effi­ciency of about one-third; therefore two-thirds of the heat produced in the reactor core by fission is waste heat that has to be rejected to water bodies and eventually to the atmosphere. Some 5% of this heat is released within the plant itself; therefore some 62% of the generated heat has to be removed by the condenser water. Large quantities of water have to pass through the condenser to remove such heat, and the flow of water depends on the limit put into the outlet temperature; for a 10°C increase, in 1 GWe plant, some 45 m3/s is needed.

To achieve heat rejection, two types of systems have been developed. Once-through systems take water from a large water body and discharge it to the same water body at a higher temperature and at a different point. Only plants built in coastal locations and in the proximity of large rivers or lakes can use such systems. In closed circuit systems, the warmed water is cooled in a cooling tower or spray pond and recirculated through the con­denser. In this way, the waste heat is finally deposited into the air. Combinations of once-through and closed circuits are frequently found, the once-through systems being used when temperature limitations in the receiving water body can be complied with (mainly during the winter), and closed circuits otherwise.

Once-through systems may cause damage to living organisms in the water body as a result of changes in temperature, the impingement of larger organisms in the water-intake screens and the entrainment of smaller organisms that pass through the condenser. Deleterious effects may also be produced by the use of chlorine and biocides, by changes in the water quality, mainly oxygen content and increases in salinity. All these effects have the potential of introducing changes into the aquatic ecosystem; they should be known to verify compliance with environmental regulations.

A large variety of chemicals are added to wet cooling towers to control bacteria and prevent corrosion. Such chemicals might eventually be dis­charged to an adjacent water body when recirculation water retaining impu­rities is taken out of the tower; this is called a blowdown. Blowdowns have to be controlled and should not be discharged to public waters without treat­ment and control in accordance with regulations. Such chemicals may also escape to the atmosphere with small water droplets in the drift, i. e. steam released from the cooling towers; these chemicals will be deposited and will accumulate on surfaces near the plant. The effects of this have to be control­led; in modern cooling towers, drift is limited and the effects minimal.

Although non-radiological effects are well recognized, their study and quantification constitute the basis of their mitigation, until compliance with existing regulations. In general, nuclear power plants create a clean environ­ment with limited physical and ecological impacts.

2.7 Conclusions

The justification principle has not been systematically developed for appli­cation to nuclear power plants, fuel cycle facilities and related relevant activities, despite the fact that it is a key requirement in international and supranational regulatory activities. Only the UK has so far developed regu­lations and guidance for justification of nuclear energy, now being applied in the justification of some new nuclear designs. Other countries have devel­oped detailed regulations regarding environmental analysis which also include social and economic aspects and are close to justification exercises. Most frequently, economic advantages and benefits are the only basis for decisions.

The application of the justification principle, as defined in the IAEA Fundamental Safety Principles, and within a well-defined and complete process, will serve to present to society a valid account of the benefits derived from nuclear energy and the risks and detriments associated with it. These studies will facilitate public understanding and help in decision processes.

There are many examples regarding nuclear installations and relevant related activities where justification could provide valid insights to high — level decision-making processes. The elements to be taken into account, the justification process itself, the definition of a justification authority, and the value and limitations of the justification decision, all need to be defined formally. Valid tools are already available to define and quantify some of the key elements which are part of the justification equation; others need further research and development.