DATA ACQUISITION

Impact assessment requires the collection of primary data on the physical inter-play between a given energy installation or system and its environment. These data include emissions and other releases, noise levels, etc. The pathway approach employed for site and technology specific studies, as well as generic data appropriate for other types of investigation are discussed.

1.1. Pathway method

For an energy installation (power plant, mine, refinery, a piece of end use equipment, etc.) at a given location, an impact analysis for the particular step in the energy conversion chain represented by the installation can be made according to the pathway method, as illustrated in Fig. 1. In principle, this method applies both to normal operation of the installation and to accident situations.

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Eg.:

emissions ->• dispersal - » level/concentration - » dose response valuation - » cost FIG. 1. Pathways for evaluating impacts [7].

The initiating step may be to calculate impacts in the form of emissions (e.g.

of chemical or radioactive substances) from the installation to the atmosphere, releases of similar substances to other environmental reservoirs, or emissions of noise. Other impacts could be from inputs into the fuel cycle (water, energy, materials such as chalk for scrubbers). In a life cycle analysis, the indirect impacts associated with the production of these inputs (typically at other sites, using other equipment) have to be enumerated, as well as the inputs to inputs, for as long as sig-nificant impacts are involved. Basic emission data are being routinely collected for power plants, whereas data for other conversion steps are often more difficult to obtain. Of course, emission data, e.g. from road vehicles, are available in some form, but they are rarely distributed over driving modes and location, as one would need in most assessment work.

The next step is to calculate the dispersal of releases in the ecosphere, for example by using available atmospheric or aquatic dispersion models. In the case of radioactivity, decay and transformation also have to be considered. For airborne pollutants, the concentration in the atmosphere is used to calculate deposition (using models for dry deposition, deposition by precipitation scavenging or deposition after adsorption or absorption of pollutants by water droplets). From this, the distribution of pollutants (possibly transformed from their original form, e.g. sulphur dioxide to sulphate aerosols) in the air and on the ground or in water bodies will be obtained, normally given as a function of time, because further physical processes may move the pollutants down through the soil (where they would eventually reach the ground-water or aquifers) or again into the atmosphere (e.g. as dust).

If the concentration of pollutants is given as a function of place and time, the pathway may be further expanded to include an impact on humans, such as by inges-tion of the pollutant. Rather large areas may have to be considered, both for normal

releases from fossil fuel power plants and for nuclear plant accidents (typically for a distance from the energy installation of 1000 km or more). Besides the negative impacts, there are of course positive impacts derived from the energy produced.

These impacts will have to be weighed against each other. In some cases, the com-parison is assisted by translating the dose responses (primarily given as number of cancers, deaths, workdays lost, and so on) into monetary values. This should only be done if the additional uncertainty introduced by monetizing is not so large that the evaluation of the monetized impacts becomes arbitrary. In any case, some impacts are likely to remain which cannot meaningfully be expressed in monetary terms.

1.2. Generic data

If the purpose of the assessment is to obtain generic energy technology evalua-tions (e.g. as inputs into planning and policy debates), one would try to avoid using data that depend too strongly on the specific site selected for the installation. These could be important impacts, depending on a specific location (involving, for exam-ple, special dispersal features, such as in a mountainous terrain) or a specific popula-tion distribupopula-tion (presence of high density settlements near the energy installapopula-tion studied). In policy discussions, these special situations should normally be avoided, whereas, in the case of actual site selection, unsuitable locations can be avoided if the planning area is sufficiently diverse.

Pure emission data are often dependent only on the physical characteristics of a given facility (power plant stack height, quality of electrostatic filters, sulphate scrubbers, nitrogen oxide treatment facilities, and so on), and not on the site.

However, the dispersion models are of course site dependent, but general concentra-tion versus distance relaconcentra-tions can usually be derived in model calculaconcentra-tions avoiding any special features of sites. As regards the dose commitment, it will necessarily depend on the population distribution, while the dose response relationship should not depend on this. As a result, a generic assessment can in many cases be per-formed, with only a few adjustable parameters left in the calculation, such as the population density distribution, which may be replaced by average densities for an extended region.

The approach outlined above will only serve as a template for assessing new energy systems, as the technology must be specified and usually would involve a comparison between state of the art, new technologies. If the impacts of the existing energy system in a given nation or region have to be evaluated, the diversity of the technologies in place must be included in the analysis, which would most likely have to proceed as a site and technology specific analysis for each piece of equipment.

In generic assessments, it is not only necessary to fix the technology and popu-lation distribution but also to assume a number of features of the surrounding society, inasmuch as they may influence the valuation of the calculated impacts (and in some

cases also the physical evaluation, e.g. as regards the preparedness of society to handle major accidents, which may influence the impact assessment in essential ways).