Development of the SharkFin Distribution for Fuel Lifetime Estimates in Severe Accident Codes

Journal Article · Fri Jul 01 04:00:00 EDT 2016 · Transactions of the American Nuclear Society

OSTI ID:23042730

Denman, M. R. ^[1]

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1. Sandia National Laboratories: P.O. Box 5800, Albuquerque, NM 87185 (United States)

Historically, MELCOR has employed models at various degrees of fidelity for evaluating fuel mechanical response to the effects of cladding oxidation, material interactions (i.e., intermetallic formation), Zircaloy melting, fuel swelling, and other processes that occur at very high temperatures. In lieu of detailed models, a simple temperature-based criterion is used to define the threshold beyond which normal ('intact') fuel rod geometry can no longer be maintained, and the core materials at a particular location collapse into particulate debris. The temperature-based criterion reflects physico-chemical processes that affect fuel rod integrity. Using a composite of information, such as from the PHEBUS studies, four data points were log-linearly interpolated to create the rod collapse criteria used in the SOARCA study. This time-at-temperature (TaT) criterion was introduced in an attempt to avoid non-physical cliff-edge effects that are observed during a calculation when fuel temperatures are predicted to hover just below a failure temperature for extended periods. However, the code still models local rod collapse due to high temperature as a discrete and near-instantaneous (over one time step) event at each core cell. This paper introduces the SharkFin statistical model for TaT fuel failure relationships whose median curve has recently been adopted as the default fuel failure criteria in MELCOR. (authors)

• OSTI ID: 23042730
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 115; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
22 GENERAL STUDIES OF NUCLEAR REACTORS
CLADDING
FUEL RODS
GEOMETRY
INTERMETALLIC COMPOUNDS
OXIDATION
PARTICULATES
SEVERE ACCIDENTS
STATISTICAL MODELS
ZIRCALOY