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原文传递 Comprehensive Assessment of Energy Systems Severe Accidents in the Energy Sector

题名：	Comprehensive Assessment of Energy Systems Severe Accidents in the Energy Sector
作者：	Hirschberg S., Spiekerman G. and Dones R.
关键词：	energy；sector；systems；assess；ssme；ompr；ever；ident；cide；comp
摘要：	This report addresses one of the major limitations of the current comparative studies of the environmental and health impacts of energy systems, i.e. the treatment of severe accidents. The work covers technical aspects of severe accidents and thus primarily reflects an engineering perspective on the energy-related risk issues. The assessments cover fossil energy sources (coal, oil and gas), nuclear power and hydro power. The scope of the work has not been limited to the power production (conversion) step of these energy chains but whenever applicable also includes exploration, extraction, transports, processing, storage and waste disposal. In relative terms more resources were allocated to the analysis of energy chains that currently dominate the Swiss electricity supply, i.e. hydro and nuclear power. With the exception of the nuclear chain the focus of the work has been on the evaluation of the historical experience of accidents. For hypothetical nuclear accidents the probabilistic technique has also been employed and extended to cover the economic consequences of power reactor accidents. Nevertheless, the report includes a detailed discussion and evaluation of the consequences of the Chernobyl accident. Within the present work 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). ENS AD (Energy-related Severe Accident Database), which covers all stages of the analysed energy chains, has been developed using a wide variety of sources. This includes among others: major commercial and non-commercial accident databases, journals, newspapers, technical reports, encyclopaedias, relevant books and conference proceedings, and inputs from numerous direct contacts with pensons and organisations being in a position to provide crucial information on past accidents. Currently, ENSAD covers 13,914 accidents, of which 4290 are energy-related. Applying the definition of a severe accident, used in the present work, 1943 severe energy-related accidents are stored in ENSAD. Accidents with at least five fatalities form the largest group (846). Due to the use of a variety of information sources ENSAD exhibits in comparison with other databases a much more extensive coverage of the energy-related accidents. Furthermore, the coverage is well balanced with respect to countries and regions where the accidents took place. 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. This includes a study of the dependency between the frequency of dam failures on the one hand, and the types of dams and their purposes on the other. Generally, while Swiss-specific aspects are emphasised, the major part of the collected and analysed data, as well as the insights gained, arc considered to be of general interest In particular, three sets of the aggregated results of the evaluation of the past experience are provided, i.e. one based on world-wide occurrence, one valid for OECD countries, and one for non-OECD-countries. The generic results obtained for OECD are for the purpose of this report considered to be representative for Switzerland. For fossil fuels allocation schemes were developed, taking into account the flows of these carriers between OECD- and non-OECD-countries. The evaluations of severe accident frequencies and their consequences were first carried out for each energy carrier covered in this work. These results were then used for comparisons between the various energy sources. The comparisons concern the electricity sector, although within the gas chain also the Liquid Petroleum Gas (LPG) is included. The results were normalised on the basis of energy production by means of each of the sources covered. 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. It is, however, acknowledged that the completeness and consistency of the coverage of these categories varies significantly between the different sources. Informed decisions should be taken in full knowledge of the technical estimates of risks. Being aware of the risk aspects which do affect the socio-political side of the matter, efforts were here directed towards addressing such features of energy-related severe accidents as: delayed effects, the chance of a large number of people being affected and the uncertainties involved in the assessment. While a variety of damage categories were considered and analysed the conclusions cited in this summary are primarily based on fatality rates. First, the statistical records on fatalities are most complete; second, the fatalities associated with large accidents are regarded as the indicator attracting most attention on the side of the society; third, the patterns for other indicators are in some (but definitely not all) cases quite similar to those characteristic for the fatality rates. The present work shows that significant differences exist between the aggregated, normalised damage rates assessed for the various energy carriers. One should, however, keep in mind that from the absolute point of view the fatality rates are in the case of fossil sources small when compared to the corresponding rates associated with the health impacts of normal operation. For this reason the evaluation focuses here on the relative differences between the various energy carriers. The broader picture obtained by coverage of full energy chains leads on the world-wide basis 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. In the case of nuclear, the estimated delayed fatality rate solely associated with the only severe (in terms of fatalities) nuclear accident (Chernobyl), clearly exceeds all the above mentioned immediate fatality rates. However, in view of the drastic differences in design, operation and emergency procedures, the Chernobyl-specific results are considered not relevant for the “Western World”. Given lack of statistical data, results of state-of-the-art Probabilistic Safety Assessments (PSAs) for representative western plants are used as the reference values. Generally, the immediate failure rates are for all considered energy carriers significantly higher for the non-OECD countries than for OECD countries. In the case of hydro and nuclear the difference is in fact dramatic. The recent experience with hydro in OECD countries points to very low fatality rates, comparable to the representative PSA-based results obtained for nuclear power plants in Switzerland and in USA. With the important exception of hydro in OECD countries, and coal and oil occasionally switching positions, the internal ranking based on the immediate fatality rates remains the same within OECD and non-OEd> countries as the above cited results based on the world-wide evidence. This is valid both for the straight-forward assessment as well as for the estimates employing allocation schemes. Accounting for delayed fatalities along with the immediate ones preserves this ranking when OECD countries are considered but due to the Chernobyl accident nuclear compares unfavourably to the other chains when the experience base is considered for non-OECD countries only. The allocation procedure considers the trade-based flows of fossil energy carriers between the non-OECD and OECD countries. The OECD countries are net importers of these energy carriers and the majority of accidents occurs within the upstream stages of these chains. Consequently, the reallocation to OECD countries of the appropriate shares of accidents that physically occurred in non-OECD countries leads to smaller differences between the corresponding damage rates for these two groups of countries in comparison with the straight-forward evaluation. The effect is particularly significant in the case of oil. For damage indicators other than fatalities the results must be interpreted with caution due to the incompleteness problems (particularly for injuries and economic losses) and inconsistencies of boundaries in the evaluation of monetary damages. It is, however, clear in spite of the uncertainties that the economic loss associated with the Chernobyl accident is highly dominant. The presentation of results is not limited to the aggregated energy chain specific values. Also frequency-consequence curves are 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. The limitations of the approach used are discussed in this report. They are related to the database (completeness and recording accuracy, quality, use of historical data), to uses of probabilistic techniques (intrinsic and practical limitations, low probability numbers), and to the scope of the present approach (e.g. coverage of current technologies only, risk perception/aversion not explicitly treated). Finally, recommendations for future work are provided. These include: (a) Database maintenance and basic extensions; (b) Coverage of renewable energy sources other than hydro power; (c) Consideration of technological advancements and associated safety improvements; (d) Further applications of probabilistic techniques; (e) Estimation of external costs associated with energy-related severe accidents (beyond the nuclear energy chain); (f) Swiss-specific allocation of accidents in external stages of energy chains; (g) Development of site-specific consequence analysis for hydro power; (h) Refinements and broadening of comparative assessment; (i) User-tailored extensions and corresponding result presentations; (j) Explicit consideration of risk perception/aversion.
报告类型：	科技报告