Is mapping a part of common cause failure quantification?
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J. K. Vaurio
Abstract
Important issues in any procedure used for estimating basic event probabilities of common cause failures (CCF) for probabilistic safety assessments (PSA) are: which plants and systems to use, how to combine them, and how to transform data from systems with different numbers of similar components to obtain CCF-rates for a specific group of components. These issues are addressed with focus on the last part called “mapping”. Certain parametric models are considered for transforming CCF event experience from data-source plants to the target plant, the plant of interest. Two sets of rules are reviewed and compared for transforming rates and assessment uncertainties from larger to smaller systems i.e. mapping down. Epistemic uncertainties are taken into account in the estimation. Mapping down equations are presented also for the alpha-factors and for the variances of CCF-rates. Consistent rules are developed for mapping up CCF-rates, uncertainties and alpha factors from smaller to larger systems. These rules are not limited to a binomial CCF model. Consistency requirements are severe and dictate certain limits to possible parametric values. Empirical alpha factors are used to quantify robust mapping ratios of complete CCF-rates. Mapping is critically analyzed and practical recommendations are made.
Kurzfassung
Bei der Schätzung von Wahrscheinlichkeiten für GVA-Basisereignisse in einer Gruppe ähnlicher, redundanter Komponenten im Rahmen von PSA stellen sich stets die wichtigen Fragen, welche Anlagen und Systeme als Datenquellen geeignet sind und zur Verfügung stehen und wie diese Daten – zum Teil aus Systemen anderen Komponentengruppenumfangs stammend – zu übertragen sind. Diese Fragen werden mit Schwerpunktsetzung auf dem letztgenannten Aspekt, dem sogenannten „Mapping“ behandelt. Bestimmte Parametermodelle werden herangezogen, um GVA-Ereignisse aus der Betriebserfahrung anderer Anlagen auf die zu untersuchende Anlage (Zielanlage) zu übertragen. Für die Übertragung der zugehörigen Ausfallraten und deren Unsicherheit von größeren auf kleinere Komponentengruppengrößen (“Mapping down“) werden zwei Vorschriften vergleichend bewertet. Des weiteren wird auf epistemische Unsicherheiten der Ratenschätzungen eingegangen. Es werden Gleichungen für das Mapping Down sowohl für Alphafaktoren als auch für die Unsicherheiten der GVA-Raten angegeben. Auch für das Mapping Up – Übertragung von kleineren auf größere Komponentengruppen – von GVA-Raten, von deren Unsicherheiten und von Alphafaktoren werden konsistente Vorschriften entwickelt, die nicht auf die Annahme eines binomialen GVA-Modells eingeschränkt sind. Dabei bestehen restriktive Konsistenzbedingungen, die mögliche Wertebereiche der Parameter einengen. Empirisch bestimmte Alphafaktoren werden herangezogen, um dem Mapping gut abgesicherte Verhältnisse integraler GVA-Raten zugrunde legen zu können. Das Mapping wird kritisch bewertet. Abschließend wird eine Reihe nützlicher Empfehlungen ausgesprochen.
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© 2006, Carl Hanser Verlag, München
Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Editorial
- Common cause failure analysis within the framework of probabilistic safety assessment
- Technical Contributions/Fachbeiträge
- Updated requirements on PSA methods and data for comprehensive safety reviews in Germany
- OECD/NEA International Common Cause Failure Data Exchange (ICDE) Project – insights and lessons learnt
- Protection against dependent failures, analysis of dependencies and derivation of CCF data
- Extension of the German database for common cause failure events
- International network on incorporation of ageing effects into PSA
- CCF analysis for new reactor designs
- CCF treatment in PSA: insights and recommendations from reviewing procedures
- Is mapping a part of common cause failure quantification?
- Further development of the coupling model
- The Process-Oriented Simulation (POS) model for common cause failures: recent progress
- CCF analysis in PSA applications from a licensee view
- Notes
- Radiation protection of outside workers
- Technical Contributions/Fachbeiträge
- Occupational exposure to natural radiation
Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Editorial
- Common cause failure analysis within the framework of probabilistic safety assessment
- Technical Contributions/Fachbeiträge
- Updated requirements on PSA methods and data for comprehensive safety reviews in Germany
- OECD/NEA International Common Cause Failure Data Exchange (ICDE) Project – insights and lessons learnt
- Protection against dependent failures, analysis of dependencies and derivation of CCF data
- Extension of the German database for common cause failure events
- International network on incorporation of ageing effects into PSA
- CCF analysis for new reactor designs
- CCF treatment in PSA: insights and recommendations from reviewing procedures
- Is mapping a part of common cause failure quantification?
- Further development of the coupling model
- The Process-Oriented Simulation (POS) model for common cause failures: recent progress
- CCF analysis in PSA applications from a licensee view
- Notes
- Radiation protection of outside workers
- Technical Contributions/Fachbeiträge
- Occupational exposure to natural radiation
