Putting nuclear in its place

26 October 2004

Opponents have suggested that with fuel and disposal, nuclear is far from CO2-free. Lifecycle assessment disputes this finding.

The World Energy Council (WEC) included lifecycle assessment (LCA) of various energy production forms in its work programme 2002-2004. The objective was to identify existing LCA studies performed in the last 10-15 years, review them and prepare an easily understood compilation report.

WEC did not aim to compare total costs (including all identified externalities) because LCA has a more limited scope than environmental impact assessment. However, it took into account the whole energy production chain from exploration and extraction to processing, storage, transport, transformation into secondary fuels and final use.

WEC noted that the main difference between electricity and normal bulk commodity production is that the supply and consumption of electricity must be balanced at each point in time. So all generation options may not be true alternatives for a specific purpose. Some plants are suitable for baseload operation, while others are used for peak production. Intermittent plants need backup either from storage or from a different type of plant.

In electricity generation systems the system characteristics play an important role in making decisions on new plant investment. The grid capacity, existing backup arrangements, type of loads and several other factors all need to be taken into account. In some cases, co-production of power and heat may be feasible. In open electricity markets, the cost of alternative supply is important.

In larger production systems, the addition of one large plant affects the system characteristics in a minor way, whereas adding a similar plant in a smaller system can have a major impact on the operation of the generation system. Customers normally purchase their electricity through a distributor providing a mixture from all operating plants in a system. The environmental characteristics of the electricity used are determined by the system and vary with time. These variations cannot be included in an LCA comparing different production alternatives.

Furthermore, various energy production options can have different types of impacts: greenhouse gas effects and hypothetical accidents, for example. Comparing these types of impacts has significant uncertainties, and makes transparency still more important.

WEC identified the following lifecycle stages:

  • Fuel preparation: exploration/ prospecting of fuel resources, fuel resource extraction and processing, including transport.
  • Infrastructure: construction of power plant, including exploration/prospecting of ores, minerals, extraction of ores and minerals, material manufacture, production of components, construction and deconstruction of vehicles and roads, transport.
  • Operation: including normal malfunctions, production of operational chemicals, incineration of operational waste, disposal processes, handling of fuel residues, equipment and transport.
  • End-of-life processes: including incineration of waste and disposal.
  • Background infrastructure: for construction and decommissioning.
  • Transmission/distribution: including infrastructure, maintenance and network losses.

The Figure presents a comparison of greenhouse gas emissions of fossil, renewable and nuclear energy systems. It has been adapted from the presentation of the results of the Comparative Assessment of Energy Sources Programme performed between 1994 and 1998 and organised by the International Atomic Energy It also shows the effect of certain emission control technologies (CO2 sequestration, low NOx burners and selective catalytic reduction. Renewable and nuclear energy systems are shown at an expanded scale in the diagram on the right hand side.

The different energy options differ in the nature and scale of their environmental impacts. The Table below illustrates relative characteristics of various primary energy sources relating to certain key factors which play a vital role in decision-making and which in most cases are covered in LCA studies.

With a multitude of different fuels and so many technologies for transforming these fuels into electricity, assessing the environmental impacts of all fuel-technology combinations is not an easy task. It is made even more complicated by the fact that the impact of a given plant varies with its environment. The environmental impact of a plant located far from populated areas is very different from those of a similar plant located in a densely populated area. This may be reflected in the way the emissions of these plants are regulated. The level of accepted environmental impacts may differ in different parts of the world, resulting in unequal levels of emissions. Local geographical and meteorological conditions also have an effect on the level of concentration a given gaseous release will cause.

With fossil fuels, the main environmental burden originates at the power plant. The contribution of upstream stages constitutes at most about 10-15% of the total emissions.

The environmental burden from hydropower, solar power and wind has a different character. As these systems create practically no emissions during operation, the emissions result from the construction stage. The power production systems themselves occupy or may inundate large land areas or require damming waterways, causing people to be relocated. The visual impacts of these electricity options may be significant but are not easily quantified or assessed.

Questions pertaining to energy accessibility (related to the direct costs of energy), energy availability (related to the security/reliability dimension) and energy acceptability (environmental externalities) form a framework for decision-makers by means of which the relative merits of different options must be gauged. LCA can assist in questions related to environmental impact, but only a subset of these impacts is normally included in an LCA. It can also be argued with reason that some of these externalities cannot be covered by the LCA method – or any other analytical method – but must be dealt with in the political process.

WEC warned that LCA techniques are far from comprehensive. LCA focuses on what can be readily analysed, but it is not very helpful for criteria which cannot be easily quantified. Differences in social value systems between countries are not reflected. It is uncertain whether a value can be placed on aesthetics or other qualitative externalities.

There is research, some of it already incorporated in LCA, that does attempt to quantify such externalities, for example through willingness to pay to avoid them. Some effects, such as biological diversity, are much harder to define since we do not know what they are, how to measure them, how they are affected by different power generation or transportation fuelling options or how to measure the changes in biodiversity caused by those impacts.

Technology developments that may significantly change lifecycle impacts are not taken into account, since the assessment is static and does not reflect dynamic system evolution. Publicly available LCA databases on energy systems often do not include up-to-date, transparent data on new, decentralised renewable power generation systems.

Given the ever-increasing importance that these technologies are expected to assume in the future, this must be seen as a serious shortcoming. Furthermore, the little data currently available are often very general and do not account for the fact that the performance of these systems changes significantly as a function of the geographic and climate conditions under which they operate.

Another aspect seriously limiting the applicability of LCA data for energy modelling, planning and policymaking purposes is that many databases have been developed without the option of future updates. The rapid technological development that pervades today’s energy sector is rendering many of these databases obsolete. Hence many important policy decisions and modelling results risk being based on data that – in spite of their apparent robustness – is often inaccurate or outdated.

It is important to remember that LCA is a tool to better inform decision-makers and should be included with other decision criteria, such as cost and performance.

Finally, it must be remembered that ‘politics will decide’ how and to what extent environmental impacts are ultimately incorporated into economic decisions.

Author Info:

Based on the report ‘Comparison of Energy Systems Using Life Cycle Assessment’, published by the World Energy Council, 5th floor, Regency House, 1-4 Warwick Street, London W1B 5LT, UK


Relative features of primary energy sources in view

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