A5-1 - Sedma Nacionalna Konferencija so Me|unarodno U~estvo...

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APPLICATION OF BEST ESTIMATE ANALYSIS AND UNCERTAINTY METHODOLOGY IN NUCLEAR REACTOR SAFETY ANALYSIS AT AECL Nikola K. Popov 1 , Amad Abdul-Razzak 1 , Romney B. Duffey 1 , Harve E. Sills 1 1 Atomic Energy of Canada Ltd., [email protected] , 2251 Speakman Drive, Mississauga, Ontario, L5K 1B2, Canada Abstract – The Canadian nuclear industry has traditionally used a conservative approach in performing licensing safety analysis for CANDU nuclear reactor power plants world-wide. The computer codes used by the Canadian nuclear industry for licensing safety analysis are mostly based on best estimate models, whereas the analysis initial conditions and standard assumptions are selected as boundary values or assumptions to yield very conservative results. Similar to practice used in the US and in many other countries, an alternative approach has been promoted for the past several years based on the best estimate and uncertainty methodology. AECL developed the so-called Best Estimate Analysis and Uncertainty (BEAU) methodology for potential use in licensing applications for CANDU nuclear reactor power plants in Canada and abroad. The BEAU methodology is consistent with the Code Scaling, Applicability, and Uncertainty methodology (CSAU) developed in the early 1990s in the US. This paper provides a summary of the BEAU development effort at Atomic Energy of Canada Ltd. and describes the key elements of the methodology. The paper also presents a summary of the pilot applications of the BEAU methodology along with key results. Keywords – nuclear reactor, safety analysis, best- estimate, uncertainty analysis 1. INTRODUCTION Safety analysis requires use of computer programs, physical models, correlations and modelling experience (engineering judgement), including Probabilistic Safety Analysis and Deterministic Safety Analysis. These approaches require validated methods that include specific statements on the applicability and accuracy for the intended application for a selected power plant and selected transient scenario. To perform safety analysis with acceptable level of credibility for a regulatory review, it is necessary to consider the uncertainties in the safety analysis itself, which includes modelling of the important phenomena, physical representation of the plant, equipment, and plant-specific data. To date, the Limit of Operating Envelope (LOE) approach has been the basis of safety analyses of CANDU ® reactors for Canadian licensing submissions, which requires that input assumptions and parameters used for safety analyses be set simultaneously to pessimistic or bounding values. For certain accident scenarios, such analysis assumptions can lead to predictions of small safety margins and unrealistic results, which can obscure the real margins and may limit operational flexibility.
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This note was uploaded on 02/18/2010 for the course ITK ETF113L07 taught by Professor Popovskiborislav during the Spring '10 term at Pacific.

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A5-1 - Sedma Nacionalna Konferencija so Me|unarodno U~estvo...

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