Safety margins identification

The first step-in plant-system and accident-sequence analysis is the identification of earthquake-induced initiating events. This is done by reviewing the internal analysis initiating events to identify initiating events relevant to seismic risk. For example. Table 5,1 -5 shows the initiating events that were used in the Seismic Safety Margins Research Program for a PWR plant (Smith et al., 1981)... 

Identification of the different barriers against radioactive releases (RRs), for PWRs typically the fuel cladding, the reactor vessel and primary coolant system boundaries and the containment/confinement) Identification of the possible challenges to each of these barriers Definition of a set of plant specific safety functions that are representative of the status/safety margins of each of the barriers Development of a tool — flow diagram, procedure, electronic system — to continuously monitor the status and challenges to each of the safety functions ... 

NOAEL (no-observed-adverse-effect level) is defined as the highest dose at which no adverse effects are observed in the most susceptible animal species. The NOAEL is used as a basis for setting human safety standards for acceptable daily intakes (ADIs), taking into account uncertainty factors for extrapolation from animals to humans and inter-individual variabilities of humans. The adequacy of any margin of safety or margin of exposure must consider the nature and quality of the available hazard identification and dose-response data and the reliability and relevance of the exposure estimations. In some cases, no adverse endpoint can be identified such as for many naturally occurring compounds that are widespread in foods. In that case, an ADI Not Specified is assigned. ... 

The fluorescence-guided identification of human brain tumours and tumour margins during surgery was evaluated to facilitate the accuracy and safety of tumour resection and minimize the probabifity of tumour recurrence. For this purpose, ICG [136], fluorescein [137], 5-aminofluorescein albumin conjugate [131], and ALA [138] have been studied in selected patients or extended clinical trials. 

Identification of risk levels and margins of safety in comparisons with other commonly encountered chemicals do not finally solve the problem whether a particular chemical risk constitutes a socially acceptable risk. This must finally be determined in the social institutions mentioned earlier at the various political jurisdictions. Whether a risk will be socially acceptable depends not only on the level of risk, which we have dealt with here, but on the nature of the risk, on who assumes the risk, who receives the benefit, and one s personal philosophy of accepting any risk versus zero risk. 

ASSESSMENT OF RISKS TO HUMANS EXPOSED TO PESTICIDES 2 The Four Steps in Risk Assessment 2 Hazard Identification 2 Dose-Response Assessment 3 Margin of Safety Approach 3 Quantitative Risk Assessment 3 Exposure Assessment 4 Risk Characterization 4 RISK MANAGEMENT 5 ADVANCES IN DATA INTERPRETATION 5 Probabilistic Approaches 5 Recognition of the Tier Approach 5 Aggregate Exposure 6 Cumulative Exposure 6 Impact of New Scientific Advances 7 Post-Registration Monitoring 7 HARMONIZATION OF REGULATORY APPROACHES SUMMARY 9... 

A proposed change, test or experiment or the discovery or Identification of new Information resulting from analyses of Incidents or accidents, new or Improved analyses or modifications or changes to procedures, processes, operations, structures, systems and/or components, shall be deemed to Involve a USQ If (1) the probability of occurrence or the consequences of an accident or malfunction of equipment Important to safety previously evaluated In the safety analysis report may be Increased or (2) the possibility for an accident or malfunction of a different type than any evaluated previously in the safety analysis report may be created or (3) the margin of safety as defined in the basis for any technical specification Is reduced. 

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