When preparing the review plan for the Bruce B Risk Assessment (BBRA), the CNSC had identified the construction of a replica using a "standard" PSA methodology and code as a major review tool. Also, the replica should be able to be used by the CNSC inspectors as an independent tool to assess importance of events or licensee's requests. The BBRA replica has been built under the SAPHIRE code, from the systems fault trees electronic models delivered by Ontario Power generation (OPG) and the paper event trees from the paper report. Building the replica has allowed the CNSC to detect several errors in the licensee's model and shortcuts in the documentation. Errors were detected in the fault trees and event trees modeling, in the PSA integration and in the cutsets manipulations. The BBRA replica allows the CNSC staff to perform "what-if' analyses (i.e., to compute the impact of a given modification on the core damage frequency), to assess importance of components and systems and to perform uncertainty and sensitivity analyses.
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