United States Nuclear Regulatory Commission - Protecting People and the Environment

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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Abstract

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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