Severe Accidents in the Energy Sector

A comprehensive database on severe accidents, with main emphasis on the ones associated with the energy sector, has been established by the Paul Scherrer Institute (PSI). Fossil energy carriers, nuclear power and hydro power are covered in ENSAD (Energy related Severe Accident Database), and the scope of work includes all stages of the analysed energy chains, i.e. exploration, extraction, transports, processing, storage and waste disposal. The database has been developed using a wide variety of sources. As opposed to the previous studies the ambition of the present work has been, whenever feasible, to cover a relatively broad spectrum of damage categories of interest. This includes apart from fatalities also serious injuries, evacuations, land or water contamination, and economic losses. Currently, ENSAD covers 13,914 accidents, of which 4290 are energy related, and 1943 are considered as severe accidents. Significant effort has been directed towards the examination of the relevance of the worldwide accident records to the Swiss specific conditions, particularly in the context of nuclear and hydro power. For example, a detailed investigation of large dam failures and their consequences was carried out. Generally, while Swiss specific aspects are emphasised, the major part of the collected and analysed data, as well as the insights gained, are considered to be of general interest. In particular, three sets of the aggregated results are provided based on world wide occurrence, on OECD countries, and on non OECD countries, respectively. Significant differences exist between the aggregated, normalised damage rates assessed for the various energy carriers: On the world wide basis, the broader picture obtained by coverage of full energy chains leads to aggregated immediate fatality rates being much higher for the fossil fuels than what one would expect if power plants only were considered. The highest rates apply to LPG, followed by hydro, oil, coal, natural gas and nuclear. Generally, the immediate failure rates are for all considered energy carriers significantly higher for the non OECD countries than for OECD countries, while the internal ranking remains the same in both categories (with the important exception of hydro energy in OECD countries). This is valid both for the straight forward assessment as well as for the estimates employing allocation schemes, in which the trade based flows of fossil energy carriers between the non OECD and OECD countries are taken into account. In addition to the presentation of results of the aggregated energy chain specific values, frequency consequence curves are also provided. They reflect implicitly the above ranking but provide also such information as the observed or predicted chain specific maximum extents of damages. This perspective on severe accidents may lead to different system rankings, depending on the individual risk aversion. Finally, the limitations of the approach are discussed, and recommendations for future work are provided. (author) refs., 147 figs., 78 tabs.