Comparative Risk Assessment and the ENSAD Database
The energy sector including its complex and interdependent technical systems is both a critical infrastructure and key resource for the functioning of today’s society and economy. Therefore, the comparative assessment of accident risks is a key component in a comprehensive evaluation of energy security aspects and sustainability performance associated with our current and future energy system.

Accidents in the energy sector often affect people’s health and property, the supply of economic goods and services, and degrade ecosystems and their functions. Thus, the protection of critical infrastructure facilities in the energy sector is of paramount importance because a sufficient and continuous energy supply forms the backbone of today’s society and many of its products, which are relying on interrelated and interdependent information and communication technologies. As a consequence, the interest and demand for more and better data on the assessment of severe accidents has considerably risen because they are the basis for improved risk management and informed decision-making concerning the diverse safety, health and environmental problems.

Although accidents in the energy sector have been shown to form the second largest group of man-made accidents (after transportation), their level of coverage and completeness was not satisfactory because they were commonly not surveyed and analyzed separately, but just as a part of technological accidents (Hirschberg et al., 1998). The Paul Scherrer Institut (PSI) started a long-term research activity in the 1990s to close this gap and to enable a factual and appropriate treatment of accident risks in the energy sector. For this purpose, the Energy-Related Severe Accident Database (ENSAD) was developed, established and is continuously updated by the PSI. The focus of ENSAD is on severe accidents because they are most controversial in public perception and energy politics, even when the total sum of the many small accidents with minor consequences is substantial.

The consideration of full energy chains is essential because an accident can happen in any chain stage from exploration, extraction, processing and storage, long distance transport, regional and local distribution, power and/or heat generation, waste treatment, and disposal. However, not all these stages are applicable to every energy chain. For fossil energy chains (coal, oil, natural gas) and hydropower, extensive historical experience is contained in ENSAD. In the case of nuclear power, Probabilistic Safety Assessment (PSA) is employed to address hypothetical accidents. In contrast, consideration of renewable energy technologies other than hydropower is based on available accident statistics, literature review and expert judgment because of limited or lacking historical experience.

In the literature there exists no consensus definition of the term “severe accident”. Within the framework of PSI’s database ENSAD an accident is considered to be severe if it is characterized by one or several of the following consequences:
- at least 5 fatalities or
- at least 10 injured or
- at least 200 evacuees or
- extensive ban on consumption of food or
- releases of hydrocarbons exceeding 10,000 t or
- enforced clean-up of land and water over an area of at least 25km2 or
- economic loss of at least 5 million USD(2000).

Selected Results
Geographic distribution of fatalities in fossil and hydro chains for the period 1970-2008. Individual Admin1 units (e.g. state, province) are colored according to their total numbers of severe (≥5 fatalities) accident fatalities Countries, for which no severe accidents are recorded in ENSAD, are shaded in grey. Overall, severe (≥5 fatalities) accidents were recorded for 106 countries; however, associated numbers of fatalities were rather unequally distributed. The top ten countries in terms of fatalities accounted for 83% of all fatalities, whereas countries with cumulated fatalities between 100 and 1000 contributed another 15.1%, and the remaining countries with less than 100 fatalities each summed up to only 1.9%.

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Comparison of fatality rates and maximum consequences of currently operating large centralized and decentralized energy technologies. Fossil and hydropower is based on the ENSAD database (period 1970 to 2008); for nuclear PSA is applied; and for other renewable sources a combination of available data, literature survey and expert judgment is used. Note: RBMK = reaktor bolshoy moshchnosty kanalny,a boiling watercooled graphite moderated pressure tube type reactor; PWR = pressurized-water reactor; CHP = combined heat and power; EGS = Enhanced Geothermal Systems.

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Geo-referenced accidental tanker oil spills (≥ 700 t) for the period 1970-2004 are represented by different circle sizes corresponding to the respective spill volume. Regional differences in susceptibility to accidents were analyzed by ordinary kriging, resulting in a prediction map layer of filled contours. Spills of at least 100’000 t are also shown on the map (labels a–k).

The map allows the identification of several world regions that are most accident-prone to oil spills, both in terms of spill numbers and volumes: (1) the Northern European Atlantic and the Eastern Mediterranean; (2) the Gulf of Mexico, the Caribbean and parts of the Southern Atlantic; (3) the Persian Gulf and Arabian Sea; (4) the South China Sea, the Gulf of Thailand and the Strait of Malacca, and (5) around the Southern tip of Africa. Extremely large spills (≥ 100’000 t) also occurred predominantly in these regions, with exception of the Odyssey spill off Nova Scotia (Canada) in 1988.

Additionally, it was analyzed which spills occurred within the boundaries of the Large Marine Ecosystems (LME) of the world that are considered areas with highly sensitive ecosystems. Overall, 223 (44 percent) of the 508 spills considered occurred within LMEs, amounting to 49 percent of total spill volume. This considerable share emphasizes why many events with relatively small releases may still lead to disproportionately high ecological and socio-economic consequences. The major shipping lanes of worldwide oil transport often intersect with LMEs. Therefore, safer passage through LMEs is essential because they are predominantly on the continental shelf and so cannot be avoided when accessing coastal harbors.

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Main publications
2013

Eckle, P. & Burgherr, P. (2013) “Bayesian data analysis of severe fatal accident risk in the oil chain. Risk Analysis 33(1): 146-160. http://dx.doi.org/10.1111/j.1539-6924.2012.01848.x.

2012

Eckle, P., Burgherr, P. & Michaux, E. (2012) Risk of Large Oil Spills: A Statistical Analysis in the Aftermath of Deepwater Horizon. Environmental Science & Technology 46 (23), pp 13002–13008. http://dx.doi.org/10.1021/es3029523

Burgherr, P., Eckle, P., Hirschberg, S. (2012) Comparative assessment of severe accident risks in the coal, oil and natural gas chains. Reliability Engineering and System Safety, 105: 97–103. http://dx.doi.org/10.1016/j.ress.2012.03.020

2011

Burgherr, P. (2011) Accidents and risks (chapter 9.3.4.7). In: Sathaye, J., O. Lucon, A. Rahman, J. Christensen, F. Denton, J. Fujino, G. Heath, S. Kadner, M. Mirza,H. Rudnick, A. Schlaepfer, A. Shmakin, 2011: Renewable Energy in the Context of Sustainable Energy. In IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation [O. Edenhofer, R. Pichs-Madruga, Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel, P. Eickemeier, G. Hansen, S. Schlömer, C. von Stechow (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. URL: http://srren.ipcc-wg3.de/report

Burgherr, P., Eckle, P., Hirschberg, S. & Cazzoli, E. (2011) Final Report on Severe Accident Risks including Key Indicators. SECURE Deliverable n° D5.7.2a, SECURE project “Security of Energy Considering its Uncertainty, Risk and Economic implications”, Brussels, Belgium.
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Eckle, P., Cazzoli, E., Burgherr, P. & Hirschberg, S. (2011) Analysis of Terrorism Risk for Energy Installations. SECURE Deliverable n° D5.7.2b (confidential), SECURE project “Security of Energy Considering its Uncertainty, Risk and Economic implications”, Brussels, Belgium.
Download Executive Summary

2010

Burgherr, P., Eckle, P., Hirschberg, S. (2010) Severe accidents in the context of energy security and critical infrastructure protection. Proceedings of the European Safety and Reliability Conference, ESREL 2010., In: Reliability, Risk and Saftey: Back to the Future (Ale, Ben J.M., Papazoglou, I. A., Zio, E. (Eds.)), CD-ROM (ISBN 978-0-415-60427-7). CRC Press, Taylor & Francis Group, London, UK.

Burgherr, P., Eckle, P., Hirschberg, S. (2010) Security risks of critical infrastructures in the oil and gas sectors. International Disaster & Risk Conference (IDRC; Online), Extended Abstracts, 30 May – 3 June 2010, Davos, Switzerland. URL: https://www.conftool.com/idrc2010/

Eckle, P., Burgherr, P., Hirschberg, S. (2010) Comparative Analysis of Severe Accident Risk in the Fossil Energy Chains . International Disaster & Risk Conference (IDRC; Online), Proceedings with Extended Abstracts, 30 May – 3 June 2010, Davos, Switzerland. URL: https://www.conftool.com/idrc2010/

2009

Burgherr, P. & Hirschberg, S. (2009) Comparative risk assessment for energy systems: a tool for comprehensive assessment of energy security. In: Wiley Handbook of Science and Technology for Homeland Security (ed.-in chief Voeller J. G.), John Wiley & Sons Inc., Hoboken NJ, USA.

Burgherr, P. & Hirschberg, S. (2008) Comparative analysis of severe accident risks in the energy sector (App. 4). In Nuclear Energy Outlook 2008 (NEA). NEA/OECD, Paris, France.

2008

Burgherr, P. & Hirschberg S. (2008) A comparative analysis of accident risks in fossil, hydro and nuclear energy chains. Human and Ecological Risk Assessment, 14(5), 947 - 973.
Link

Burgherr, P. & Hirschberg S. (2008) Severe accidents in the oil chain with emphasis on oil spills. Strategic Insights, 7(1). 15 pp.
Link

Burgherr, P. & Hirschberg, S. (2008) Severe accident risks in fossil energy chains: a comparative analysis. Energy, 33(4), 538–553.
doi:10.1016/j.energy.2007.10.015

Burgherr, P., Hirschberg, S., Cazzoli, E. (2008) Final report on quantification of risk indicators for sustainability assessment of future electricity supply options. NEEDS Deliverable n° D7.1 – Research Stream 2b. NEEDS project "New Energy Externalities Developments for Sustainability", Brussels, Belgium.
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2007

Burgherr, P. & Hirschberg, S. (2007) Assessment of severe accident risks in the Chinese coal chain. International Journal of Risk Assessment and Management, 7(8): 1157-1175.
doi:10.1504/IJRAM.2007.015299

Burgherr P. (2007) In-depth analysis of accidental oil spills from tankers in the context of global spill trends from all sources. Journal of Hazardous Materials 140(1-2): 245–256.
Available at: Journal of Hazardous Materials 140(1-2)
Journal Website: http://www.elsevier.com/locate/jhazmat

2006

Burgherr P., Hirschberg S. & Grawe J. (2006) In welchem Umfang sind im Energiebereich während der letzten 30 Jahre schwere Unfälle aufgetreten? Energie-Fakten.de
Website: http://www.energiefakten.de

Burgherr P. & Hirschberg, S. (2006) Schwere Unfälle im Energiebereich. International Journal for Nuclear Power 51(4), 242-247.

Burgherr, P., Hirschberg, S. & Hardegger, P. (2006) Severe accident database ENSAD. PSI Annual Report 2006, Part Technology Transfer, pp. 78-79, Paul Scherrer Institut, Villigen, Switzerland.
PSI Scientific Report 2005: Volume 3 (Energy and environment, English)

2005

Energie-Spiegel No. 13 / May 2005

Burgherr, P. & Hirschberg, S. (2005) Severe accident database for comprehensive risk assessment in the energy sector. In Risk & Safety. Impacts on research and education (eds. Mock, R. & Birchmeier, J.), Step-Commerce AG / MAXIMA, Zürich.

Burgherr P. & Hirschberg S. (2005). Comparative assessment of natural gas accident risks. PSI Report No. 05-01, Villigen-PSI, January 2005.
Download PSI Report (2.4 MB)

Burgherr, P. (2005) Unfallrisiken im Energiesektor. Gas Wasser Abwasser gwa 9/2005, 683-693.
Website: http://www.gwa.ch

Burgherr, P. (2005) Unfallrisiken von Erdgas: eine umfassende Analyse. GWF - Gas/Erdgas 146(2005), Nr. 10, 574-581.
Website: GWF - Gas/Erdgas

Burgherr, P. & Hirschberg, S. (2005) Accident risks in the energy sector: comparative evaluations. PSI Annual Report 2004 / Annex IV, Paul Scherrer Institut, Villigen, Switzerland.

2004

Hirschberg S., Burgherr P., Spiekerman G. & Dones R. (2004). Severe accidents in the energy sector: comparative perspective. Journal of Hazardous Materials 111(1-3): 57-65.
Available at: Journal of Hazardous Materials 111(1-3)
Journal Website: http://www.elsevier.com/locate/jhazmat

Burgherr P. & Hirschberg S. (2004). Severe accidents in fossil energy chains: individual chain results and aggregated evaluations. In Spitzer C., Schmocker U. & Dang V. (Eds.), Proceedings of the 7th International Conference on Probabilistic Safety Assessment and Management (PSAM7 - ESREL'04), Berlin, Germany, 14-18 June 2004, Vol. IV, 2320-2325, Springer Verlag, London (UK).
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Hirschberg S., Burgherr P. & Hunt A. (2004) Accident risks in the energy sector: comparison of damage indicators and external costs. In Spitzer C., Schmocker U. & Dang V. (Eds.), Proceedings of the 7th International Conference on Probabilistic Safety Assessment and Management (PSAM7 - ESREL'04), Berlin, Germany, 14-18 June 2004, Vol. IV, 2314-2319, Springer Verlag, London (UK).
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NewExt (New Elements for the Assessment of External Costs from Energy Technologies) (2004): Final Report to the European Commission, DG Research, Technological Development and Demonstration (RTD).
Final NewExt Report (333 pages, 3.6 MB)

2003

Hirschberg S., Burgherr P., Spiekerman G., Cazzoli E., Vitazek J. & Cheng L. (2003). Comparative Assessment of Severe Accidents in the Chinese Energy Sector - China Energy Technology Program. PSI Report No. 03-04, Villigen-PSI, March 2003
Download PSI Report (1.7 MB)

Hirschberg S., Burgherr, P., Spiekerman, G, Cazzoli, E., Vitazek, J. & Cheng, L. (2003) Assessment of severe accident risks. In: Integrated assessment of sustainable energy systems in China. The China Energy Technology Program - A framework for decision support in the electric sector of Shandong province (eds. Eliasson, B. & Lee, Y.Y). Alliance for Global Sustanaibility Series Vol. 4, Kluwer Academic Publishers, Amsterdam, The Netherlands.
Available at: http://www.springeronline.com/sgw/cda/frontpage/0,11855,5-40356-72-33707785-0,00.html

2002 and before

Hirschberg S., Spiekerman G., Dones R. & Burgherr P. (2001) Comparison of severe accident risks in fossil, nuclear and hydro electricity generation", Invited paper, EAE 2001, International Conference on Ecological Aspects of Electric Power Generation, 14-16 November 2001, Warsaw, Poland.

Hirschberg S., Spiekerman G. & Dones R. (1998). Severe Accidents in the Energy Sector. PSI Report No. 98-16, Villigen-PSI, November 1998.
Download PSI Report (2.9 MB)
Download PSI Report Appendices (1.3 MB)

For a complete publication list of the Technology Assessment group click here

Contact persons
Dr. Peter Burgherr
Laboratory for Energy Systems Analysis
Paul Scherrer Institut
CH-5232 Villigen PSI
Switzerland

Phone: +41 (0) 56 310 2649
Fax: +41 (0) 56 310 2199
e-mail: Peter Burgherr