United States Nuclear Regulatory Commission - Protecting People and the Environment

Assessment of Current Test Methods for Post-LOCA Cladding Behavior (NUREG/CR-7139, ANL-11/52)

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Publication Information

Manuscript Completed: October 2011
Date Published: August 2012

Prepared by:
M. C. Billone

Nuclear Engineering Division
Argonne National Laboratory
Argonne, IL 60439

H. H. Scott, NRC Project Manager

NRC Job Code V6199

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

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Abstract

Test methods to assess fuel-rod cladding behavior following a loss-of-coolant accident (LOCA) are compared and evaluated. For non-deformed cladding regions with uniform levels of hydrogen content and oxidation, the three-point bend test (3-PBT) is a very good test for ductility determination of as-fabricated and pre-hydrided cladding subjected to LOCA oxidation and quench. For irradiated cladding, the ring compression test (RCT) has clear advantages over the 3-PBT because the required sample length is only about one-tenth of that needed for the 3-PBT. Overall, the RCT is the best test method for generating ductility data for assessing the effects of irradiation and hydrogen pickup on embrittlement oxidation threshold. However, neither 3-PBTs nor RCTs are useful for evaluating the performance of ballooned and ruptured cladding with significant axial gradients in cladding geometry, oxidation level, and hydrogen content, as well as circumferential gradients in wall thickness and oxidation level within the rupture region. Partially restrained axial contraction tests are useful for determining the fracture/nofracture boundary for ballooned, ruptured, oxidized, and quenched cladding as a function of hydrogen content and oxidation level. The four-point bend test (4-PBT) is best for determining three cladding performance metrics: maximum bending moment (measure of strength), failure energy (measure of toughness), and offset displacement (measure of plastic deformation).

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