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Fracture Analysis of Vessels – Oak Ridge FAVOR, v16.1, Computer Code: Theory and Implementation of Algorithms, Methods, and Correlations

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Over the last three decades, there have been significant advancements and refinements in technologies
that have impacted established fracture mechanics and risk-informed methodologies. Updated
computational methodologies have been developed through interactions between experts in
the relevant disciplines of thermal hydraulics, probabilistic risk assessment, materials embrittlement,
fracture mechanics, and inspection (flaw characterization). These methodologies have been
applied in the assessment and updating of regulations designed to insure that the structural
integrity of nuclear reactor pressure vessels (RPVs) is maintained throughout the licensed service
life of the reactor. Contributors to the development of these methodologies include the U.S.
Nuclear Regulatory Commission (NRC) staff, their contractors, and representatives from the
nuclear industry.

These updated methodologies have been implemented into the Fracture Analysis of Vessels –
Oak Ridge (FAVOR) computer code developed at Oak Ridge National Laboratory (ORNL) for
the NRC. The analysis of Pressurized Thermal Shock (PTS) transients in nuclear power plants
was the primary motivation for the initial development of FAVOR; therefore, earlier versions of
FAVOR were limited to performing fracture analyses of pressurized water reactors (PWRs)
subjected to cool-down transients.

An evolutionary process of development sponsored by the NRC has resulted in the latest and
final release of the FAVOR code, v16.1. This release of FAVOR is capable of modeling a broad
range of loadings, including normal operational transients (start-up, shut-down, and leak-test) as
well as upset conditions such as PTS. FAVOR provides the capability to perform deterministic
and risk-informed probabilistic fracture analyses of boiling water reactors (BWRs) and PWRs
subjected to heat-up and / or cool-down transients. This update of the FAVOR code incorporates
a revised stress-intensity-factor influence coefficient database for internal surface breaking
infinite axial and 360◦ continuous circumferential flaws that was derived using techniques
consistent with those used for internal surface breaking finite-length flaws.

This report is intended to document the technical bases for the assumptions, algorithms, methods,
and correlations employed in the development of FAVOR, v16.1, and, as such, is a
companion to the FAVOR, v16.1, User’s Guide.