Pressure and Leak-Rate Tests and Models for Predicting Failure of Flawed Steam Generator Tubes (NUREG/CR-6664)

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Publication Information

Manuscript Completed: June 2000
Date Published: August 2000

Prepared by:
S. Majumdar, K. Kasza, J. Franklin

Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439

J. Muscara, NRC Project Manager

Prepared for:
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code W6487

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This report summarizes the models used for predicting failure pressures and leak rates in unrepaired steam generator tubes with axial and circumferential cracks that developed under normal operation and design-basis accident conditions. These models are first validated with failure and leak rate tests at room temperature and at 282°C on tubes with well-characterized rectangular EDM notches and are then applied to the failure and leak rate tests conducted on tubes with laboratory-generated outer-diameter stress corrosion cracks (ODSCC), which have highly complex morphology. A procedure for defining equivalent rectangular cracks for SCC cracks on the basis of Eddy Current +Point™ data is presented. Except for tests that exhibited time-dependent initiation and increase of leak rates, the model predictions are in reasonable agreement with test results. In the second half of the report, a model is presented for predicting failure during severe accidents of Electrosleeved* steam generator tubes with axial cracks in the parent tubes. The model is refined on the basis of high-temperature failure test results on Electrosleeved tubes with electro-discharge-machined notches. It is then used to predict failure of Electrosleeved tubes with cracks subjected to postulated severe accident transients.

* Electrosleeve is a trademark of Ontario Hydro Technologies, Inc.

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