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Advancements in Probabilistic Approaches for CANDU Components and Systems in Canada

Abstract of the technical presentation presented at:
4th International Symposium on Probabilistic Methodologies for Nuclear Applications (ISPMNA)
November 1-3, 2022

Prepared by:

B. Wasiluk, B. Carroll and J. Riznic
Canadian Nuclear Safety Commission


The CANDU reactor core consists of between 380 and 480 pressure tubes, depending on reactor core design and thermal power output. Each pressure tube contains 12 or 13 fuel bundles containing natural uranium fuel and uses heavy water as coolant. Each pressure tube has an inlet and outlet feeder to transport the coolant to headers and eventually steam generators for heat removal before being returned to the core. CANDU reactors use multiple steam generators, each containing several thousand tubes. The CANDU reactor core experiences heavy neutron irradiation, making performance of the large number of required in-field inspections challenging. Consequently, assessments of the CANDU reactor core and other systems with multiple components are well suited for probabilistic approaches to assess the system's present and predict future conditions. Probabilistic methodologies with associated probabilistic acceptance criteria have gradually been introduced to demonstrate fitness for service. Probabilistic assessments can be accompanied by an uncertainty analysis, including the approaches already standardized by the Canadian Standard Association. The present application of probabilistic approaches to passive components and systems is discussed in the context of the regulatory framework in Canada. This includes steam generator tubes and pressure tubes with consideration of long-term operation.

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