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[en] This publication discusses the development and application of a hierarchical structure of safety goals encompassing high level goals and detailed technical requirements that may assist in forming a coherent and consistent approach to nuclear safety The suggested hierarchy of safety goals provides a practical approach to consistently embrace the set of safety-related requirements, both qualitative and quantitative, and develop the interconnections between them. Specifically, the structure supports adding country specific safety goals (e.g. risk metrics) to the overall safety considerations in a consistent manner. This process can be aided by reference to the IAEA Safety Standards.
[en] The health and safety regulatory system in the UK is based on a goal-setting approach and nuclear safety follows the same principles that are used in regulating health and safety in industrial situations across virtually all types of work. Thus the regulatory body does not set prescriptive requirements but determines broad safety goals which the licensee has to comply with and hence its own detailed requirements. However, the overall effect of this regulatory approach can be seen to fit the general approach described in this report.
[en] This annex was primarily aimed at tentatively applying the proposed Safety Goals Framework on the situation in Sweden, taking into consideration mainly laws and regulations, but also addressing some utility requirements. It is important to recognise that the application was not aimed to be complete. Still some general conclusions can be drawn. Thus, existing laws and regulations seem to provide a good coverage of the four layers of the Safety Goals Framework, including demonstrating adequate coverage of different types of facilities and covering the entire life span. The application of the Safety Goals Framework to Swedish conditions was quite easily done, i.e., it seems the framework and work process suggested in the TECDOC are quite easily applied.
[en] In a 1986 Safety Goal Policy Statement, the U.S. Nuclear Regulatory Commission (USNRC) described safety goals to help articulate a level of acceptable risk for safe operation of U.S. commercial nuclear power plants. The Commission established two goals that are stated in terms of public health risk – one addressing individual risk and the other addressing societal risk. The risk to an individual is based on the potential for death resulting directly from a reactor accident, i.e., a prompt fatality. The societal risk is stated in terms of nuclear power plant operations, as opposed to accidents alone, and addresses the long-term impact on those living near the plant. In both cases, the Commission based its acceptable level of risk on a comparison with other types of risk encountered by individuals and by society from other causes, applying the rule that the consequences of nuclear power plant operation should not result in significant additional risks to life and health. The safety goals were expressed in qualitative terms, so that the philosophy could be understood by all. In both cases, however, the Commission also expressed the qualitative goals for the safety of nuclear power plants in terms of individual and societal “quantitative health objectives” or “QHOs.” These QHOs were established at onethousandth of the risk arising from other causes presenting the same type of risk.
[en] This annex provides an overview of three examples of safety goals hierarchies developed by expert groups within other projects: •: Western European Nuclear Regulators Association; • Multinational Design Evaluation Project; • Nordic PSA Group
[en] In the past, the safety concept of nuclear power plants as well as licensing and supervising decisions by the competent authorities and their experts in the Federal Republic of Germany were mainly based on deterministic principles. Safety-related decision-making during design and licensing has essentially been based on the verification of compliance with the German regulations pre-describing technical requirements as laid down, e.g., in the German nuclear safety standards. A probabilistic safety assessment has been essentially performed in the framework of the periodic safety reviews as a supplement to the deterministic safety analysis. Currently, no specific probabilistic quantitative safety goals for nuclear power plants or other nuclear facilities and no site-wide safety goals are determined within the German regulatory framework. However, a recent document requires that modifications of measures, equipment or the operating mode of a nuclear power plant, compared with the unchanged condition of this plant, must not lead to an increase in the average core damage frequency and the average frequency of large and early releases, neither for full power operation nor for low-power and shutdown states, considering all plant-internal events as well as all internal and external hazards as well as very rare man-made external hazards.
[en] This annex identifies how safety goals are defined and applied in Canada for nuclear installations. Average safety goal targets and limits have been established as a “measuring stick” to determine if station design, operation and maintenance practices fall within international guidelines for existing nuclear power plants, and to propose and rank modifications to reduce risk estimates. Overall, average risk is managed at the system level through application of reliability targets based on PSA for systems identified important to safety. Further, a decision-making process has been developed when goals or limits are exceeded. As a recent development in Canada, greater interest and consideration is being given to wholesite risk assessment and site-based safety goal definitions within the context of a hierarchal safety goals framework. As well, the topic of whether/how to aggregate risks across different hazard types (internal and external hazards) is being explored. Canada is taking a lead role in these areas, working in consultation with the broader PSA community at both the industry and regulatory levels. (author)