Risk-oriented comparative analysis focuses on energy- related severe accidents (some with extremely low probabilities) including fires, explosions, structural collapses and uncontrolled releases of toxic substances into the environment. A reasonably complete picture of the wide spectrum of health, environmental and economic effects associated with different energy systems calls for considering damages due to severe accidents as well as to normal operation.

Within the framework of the GaBE project comprehensive analyses are carried out on past and potential severe accidents in the energy sector covering full energy chains, including exploration, extraction, processing, storage, transport and waste management. Analyses cover technical aspects of severe accidents and thus primarily reflect an engineering perspective on the energy-related risk issues, though some social implications are also be touched upon. Damages cover fatalities, injuries and evacuees, releases of hydrocarbons, required clean-up of land and water and economic losses. Probabilistic Safety Assessment (PSA) is employed when past experience is either not sufficient or not representative. The results are based upon the database ENSAD (Energy-related Severe Accident Database) on energy-related accidents and an assessment of the corresponding externalities.

A detailed overview of the ENSAD database including methodology, implementation, structure and contents is available here .

ENSAD

In 1998 the Paul Scherrer Institute established the highly comprehensive database ENSAD that encompasses detailed information on severe accidents with emphasis on the energy sector. The detailed historical experience contained by this database was supplemented by probabilistic analyses for the nuclear energy chain to carry out a detailed comparison of severe accident risks in the energy sector. Since then regular updates and extensions have been performed to keep the database up to date and to broaden the spectrum of available analysis types.

Currently, energy-related accidents account for 6404 out of a total of 18'400 accidents stored in ENSAD. 3117 energy-related accidents were classified as severe with regard to the extent of damages and using the definition of severe accident established in this project. Besides chain-specific evaluations, selected aggregated accident indicators have been generated and compared. The approach used accounts for contributions from all stages of the analyzed fuel cycles. The comparison of different energy chains was based on normalized indicators combining consequences (e.g. fatalities) and product (GWeyr), and on the estimated accident-related external costs for selected technologies. In addition to aggregated indicators, frequency-consequence curves were also generated.

For selected results based on ENSAD click on the thumbnails below.

	Figure 1: Aggregated, normalized, energy-related damage rates
	Figure 2: Frequency-consequence curves for full energy chains in OECD countries
	Figure 3: Frequency-consequence curves for full energy chains in non-OECD countries

China Energy Technology Program (CETP)

The goal of the risk assessment activity within the China Energy Technology Program (CETP) was to provide a balanced perspective on the severe accident risks specific to China. The assessment addressed fossil energy sources (coal, oil and gas), nuclear power and also hydro power on a lower level of detail . This limitation is partially due to the focus of CETP on the Shandong Province, which lacks hydro resources, and partially due to the scarcity of relevant hydro data. However, there are strong indications that severe accidents at Chinese dams are subject to substantial underreporting.

The focus of the work was on historical experience of accidents and their applicability to China. For this purpose the ENSAD database was expanded by implementation of additional Chinese records. This was shown to be highly important for the Chinese coal energy chain, which exhibits very high accident fatality rates in comparison with other countries having large coal resources. For the nuclear chain the methodology of Probabilistic Safety Assessment (PSA) was employed in view of the extreme scarcity of historical severe accident events.

Examples of Risk Assessment results are provided in the CETP Guided Tour (go to: Technologies & Burdens / Accident Risks).

NewExt

During the European Research Project on “New Elements for the Assessment of External Costs from Energy Technologies” (NewExt) the ENSAD database and the analysis were much extended, not only in terms of the data but also in the scope of applications. The main objectives were: (1) to carry out comparative assessment of severe accidents in the energy sector, with the main emphasis on non-nuclear energy chains; and (2) to assess the external costs associated with severe accidents within the various energy chains. Thus, the results can support policy decisions and serve as an essential input to the evaluation of sustainability of specific energy systems. Lack of estimates of external costs of non-nuclear accidents was earlier identified as one of the major limitations of state-of-the-art of externality assessment. Uses of the database for engineering purposes are feasible but have not been pursued until now.

Damage costs and external costs of severe accidents in different energy chains were estimated, based on the unit cost values for the various types of consequences. Table 1 shows the results for immediate fatalities, obtained using historical experience in OECD and non-OECD countries. Since the costs provided in the table only cover immediate fatalities it is of interest to relate them to the accident damage costs based on Probabilistic Safety Assessment (PSA) for a Swiss nuclear power plant, which are dominated by the costs of latent fatalities. The mean value has been assessed at 1.2E-3 US-cents/kWhe, with 5-th and 95-th percentiles at 1.0E-4 and 3.8E-3 US-cents/kWhe. These results also include the damage costs of non-health effects (Hirschberg et al. 1998).

Table 1: Summary of full chain damage costs and external costs (€-Cents(2002)/kWh) of severe accidents with at least five immediate fatalities; the reference coal, oil and natural gas electricity generating plants have efficiencies of 41, 30 and 53%, respectively. (Value of a Statistical Life (central value) = 1.045 million Euro).

Available NewExt Reports:
Publishable NewExt Report (50 pages, 0.5 MB)
Final NewExt Report (333 pages, 3.6 MB)

Natural Gas Accident Risks

This study encompassed a primarily experience-based comparison of accident risks associated with the energy sector, with special emphasis on the natural gas chain. The results provide a broader perspective on the gas-specific risks, but this information is also of interest to various stakeholders beyond the gas sector.

The study utilized a hierarchical approach including (1) comparative analyses of different energy chains, (2) specific evaluations for the natural gas chain, and (3) a detailed overview of the German situation, based on an extensive data set provided by Deutsche Vereinigung des Gas- und Wasserfaches (DVGW). The inclusion of detailed accident statistics from a national industry association allowed a complete evaluation of severe and smaller accidents.

Severe accident indicators (≥5 fatalities) were not only calculated for OECD and non-OECD countries, but also for the EU15 and Central Europe countries, as the latter two subdivisions are of particular interest due to the scope of this study. Although the number of reported accidents in OECD countries is higher than in non-OECD countries (Figure 4a), the total number of fatalities is lower (Figure 4b ). Fatalities per accident were almost twice as high in non-OECD countries compared to OECD countries (Figure 4c). EU15 and particularly Central Europe showed an even better performance than the whole OECD. Concerning fatalities per GWeyr a similar pattern was observed (Figure 4d). Non-OECD countries exhibited the highest failure rate, followed distantly by OECD and EU15 countries. As before, Central Europe performed best with a fatality rate of 0.061 per GWeyr.

Figure 4: Number of (a) accidents, (b) fatalities, (c) fatalities per accident, and (d) fatalities per GWeyr for the natural gas chain, based on historical experience of severe accidents that occurred in the period 1969-2000. Results are given for OECD, EU15, Central Europe (CH, DE, NL, GB, BE, DK) and non-OECD.