Engineering Risks

1 Introduction.- 1.1 Definition of Risk.- 1.1.1 The Element of "Damage".- 1.1.2 The Element of "Uncertainty".- 1.1.3 Combining Magnitude of Damage and Probability to Risk Numbers.- 1.1.3.1 Individual Risk.- 1.1.3.2 Collective Risks for a Specific Category of Damage.- 1.1.4 Risk Numbers for Rare or Unobserved Events.- 1.1.4.1 Risk Estimates Based on Observations of the Complementary Event.- 1.1.4.2 Risk Estimates Based on Knowledge of Details.- 1.1.4.3 Uncertainties in Risk Assessments Based on Knowledge of Details.- 1.1.4.4 Quantification of Uncertainties in Risk Estimates.- 1.1.5 Formalized Representation of Risk.- 1.1.6 Presentation of Estimated Risk Numbers.- 1.1.7 Problems of Delineation.- 1.2 Potential of Probabilistic Methods for Safety and Risk Valuation.- 1.3 Overview of the Following Chapters.- References.- 2 Methods of Risk Analysis.- 2.1 Plant Systems Analyses.- 2.1.1 Collection of Basic Plant Data.- 2.1.2 Identification of Initiating Events.- 2.1.3 Event Sequence Analysis.- 2.1.4 Reliability Analysis.- 2.1.4.1 Determination of Failure Probabilities and Unavailabilities of Components.- 2.1.4.2 Fault Tree Analysis.- 2.1.4.3 Simulative (Monte Carlo) Methods.- 2.1.4.4 Analytical Methods.- 2.1.4.5 Comparison of the Methods.- 2.1.4.6 Markov Models.- 2.1.4.7 Dependent Failures.- 2.1.4.8 Human Error.- 2.1.5 Determination of Releases of Dangerous Substances or Energy.- 2.2 Determination of Accident Consequences.- 2.2.1 Environmental Transport.- 2.2.2 Calculation of Release Effects.- 2.3 Presentation of Results.- 2.3.1 Generalities.- 2.3.2 Collective Risks.- 2.3.3 Individual Risks.- 2.3.4 Formalized Representation of Risk Assessment.- 2.4 Uncertainty of Results.- References.- 3 Risk Studies for Nuclear Installations.- 3.1 Object and Methods of Risk Analyses for Nuclear Power Plants.- 3.1.1 Plant Systems Analysis.- 3.1.1.1 Initiating Events for Core Degradation or Destruction.- 3.1.1.2 Event Sequence and Reliability Analysis of the Protection and Safety Systems.- 3.1.1.3 Event Sequence Analysis for Core Destruction and Loads on the Reactor Pressure Vessel.- 3.1.1.4 Containment Performance Analysis.- 3.1.2 Accident-Consequence Calculations.- 3.1.2.1 Atmospheric Dispersion and Deposition.- 3.1.2.2 Determination of Radiation Doses.- 3.1.2.3 Determination of Radiation Health Effects.- 3.2 Studies for Light Water Reactors.- 3.2.1 The US Reactor Safety Study.- 3.2.2 Further Studies in the USA.- 3.2.3 NUREG-1150.- 3.2.4 Risk Study for German Nuclear Power Plants.- 3.2.4.1 Phase A.- 3.2.4.2 Phase B.- 3.2.5 Probabilistic Analysis for the Sizewell B Power Station.- 3.2.6 Analyses of Precursors of Severe Core-Damage Accidents.- 3.3 Studies for Fast Breeder and High Temperature Reactors.- 3.3.1 Risk Study for the Sodium-Cooled Fast Breeder Reactor SNR-300 [42].- 3.3.2 Risk Analyses for High Temperature Reactors.- 3.3.2.1 The AIPA Study.- 3.3.2.2 Safety Analysis for the High Temperature Reactor Under German Siting Conditions.- 3.4 Risks of the Nuclear Fuel Cycle.- 3.4.1 Overview of the Fuel Cycle.- 3.4.2 Studies for the Entire Fuel Cycle.- 3.4.3 Studies for Individual Stations of the Nuclear Fuel Cycle.- 3.4.3.1 Facilities for the Fuel Supply.- 3.4.3.2 Plants for the Disposal of Spent Fuel.- 3.4.4 Transportation.- 3.4.5 Decommissioning of Nuclear Installations.- 3.4.6 Summary and Outlook.- 3.5 Conclusions from Risk Studies for Nuclear Reactors.- 3.5.1 Generalities.- 3.5.2 Influence on Research Programmes.- 3.5.3 Influence on Plant Design and Modes of Operation.- References.- 4 Risk Studies for Process Plants.- 4.1 Specific Methods of Analysis.- 4.2 Canvey.- 4.2.1 Originator and Objective.- 4.2.2 Overview of the Industrial Complex and Its Hazard Potentials.- 4.2.3 Investigated Types of Damage.- 4.2.3.1 Explosions.- 4.2.3.2 Release of Toxic Substances.- 4.2.3.3 Fires.- 4.2.4 Damage-Causing Events and Their Quantification.- 4.2.5 Impacts of Accidents.- 4.2.6 Results and Conclusions.- 4.2.7 Canvey - A Second Report.- 4.3 Rijnmond.- 4.3.1 Originator and Objectives.- 4.3.2 Overview of the Industrial Complex and Its Hazard Potentials.- 4.3.3 Types of Damage Investigated.- 4.3.4 Method of Analysis.- 4.3.4.1 Initiating and Undesired Events.- 4.3.4.2 Data for Quantifying Undesired Events.- 4.3.4.3 Fault Tree Analyses.- 4.3.4.4 Determination of Source Terms.- 4.3.4.5 Dispersion Calculations.- 4.3.5 Impacts of Accidents and Counter-measures.- 4.3.5.1 Explosions.- 4.3.5.2 Fires.- 4.3.5.3 Toxic Vapours and Gases.- 4.3.6 Results and Conclusions.- 4.3.7 Uncertainties.- 4.4 Comparative Remarks.- 4.4.1 Canvey-Rijnmon.- 4.4.2 Rijnmond - DRS-A.- 4.4.2.1 Preliminary Remark.- 4.4.2.2 Objective.- 4.4.2.3 Object of the Analyses.- 4.4.2.4 Initiating and Undesired Events.- 4.4.2.5 Data for Quantifying Undesired Events.- 4.4.2.6 Fault Tree Analyses.- 4.4.2.7 Release Processes.- 4.4.2.8 Dispersion Calculations.- 4.4.2.9 Damage Models.- 4.4.2.10 Summary.- References.- 5 Risk Comparisons for Nuclear and Conventional Energy Conversion Systems.- 5.1 Problems, Benefits and Bases of Comparison.- 5.2 Technical Parameters and Data for Environmental Impact of Energy Conversion Systems.- 5.2.1 Preliminary Remarks.- 5.2.2 Coal-fired Power Plants.- 5.2.3 Oil-fired Power Plants.- 5.2.4 Natural Gas-powered Plants.- 5.2.5 Nuclear Power Plants.- 5.2.6 Renewable Energy Sources.- 5.3 Environmental Impact from the Fuel Cycle.- 5.3.1 Preliminary Remarks.- 5.3.2 Coal.- 5.3.3 Natural Oil and Natural Gas.- 5.3.4 Nuclear Energy.- 5.4 Risk Comparisons.- 5.4.1 Preliminary Remark.- 5.4.2 Calculational Procedures.- 5.4.3 Results of the Risk Comparisons.- 5.5 Summary and Recommendations for Further Work.- References.- 6 Appraisal of the Safety of Nuclear Power Plants.- 6.1 Principles of Technical Safety.- 6.2 Outline of Legal Foundations.- 6.3 Procedure of Safety Evaluation.- 6.3.1 Foundations.- 6.3.2 Present Practice.- 6.3.3 Further Development.- 6.4 Probabilistic Characterization of the Present Level of Safety.- 6.4.1 Protection of the Individual.- 6.4.2 Precaution Against Risk.- 6.5 Potential of the Combined Use of Deterministic and Probabilistic Methods.- 6.6 Probabilistic Objectives for Safety.- 6.6.1 Introduction.- 6.6.2 System Reliability and Availability.- 6.6.3 Dangerous Plant Conditions.- 6.6.4 Objectives Concerning Radioactive Releases into the Atmosphere.- 6.6.5 Safety Goals Concerning Radiation Exposure.- 6.6.6 Health Risks of Individuals and Groups of Population.- 6.6.7 Probabilistic Design Objectives on External Events and Fires.- 6.6.8 Probabilistic Safety and Design Objectives in the Federal Republic of Germany.- 6.7 Outlook.- References.- Appendix: Risk Values.