STP681

    Performance of Irradiated Copper and Zirconium Barrier-Modified Zircaloy Cladding Under Simulated Pellet-Cladding Interaction Conditions

    Published: Jan 1979


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    Abstract

    Expanding mandrel laboratory simulations of the pellet-clad interaction (PCI) mechanism (including argon, iodine, and cadmium environments) were employed to evaluate copper barriers and zirconium-lined tubing performance. Zircaloy-2 and copper-plated and zirconium-lined barrier tube specimens were tested in the unirradiated (cold-worked) and in the irradiated (recrystallized) conditions at about 600 K. Tubing was irradiated at 620 K to a fast (E > 1 MeV) fluence near 2 × 1025 n/m2.

    Brittle PCI-type failures were produced in unirradiated Zircaloy-2 tubing by expanding mandrel loading with iodine and cadmium. Failure strains were further reduced for irradiated Zircaloy-2 tested in each embrittling environment. Fractographic analyses revealed brittle fracture surface features similar to those reported for failed fuel rods. In contrast, high-strain ductile ruptures were produced in both unirradiated and irradiated tube samples tested in argon. These findings support the PCI description for fuel rod fractures. Zirconium-lined Zircaloy was not embrittled by cadmium even after neutron irradiation. High average failure strains and ductile fracture surface features were observed for the zirconium-lined tubing tested with cadmium, analogous to Zircaloy-2 tested in an inert environment. Similar experiments with low-pressure (4 to 40 Pa) gaseous iodine produced brittle cracking in the zirconium liner and in the underlying Zircaloy, both before and after irradiation, but at average strains well in excess of those required for brittle failure of Zircaloy tubing. Copper-electroplated Zircaloy tubing also exhibited excellent resistance to simulated PCI failure for both irradiated and unirradiated conditions when exposed to iodine or cadmium. Average failure strains and fractographic features were similar to results obtained for Zircaloy-2 tested in an inert environment. Mechanisms for the performance of copper zirconium barrier tubing were discussed. It was concluded that, based on laboratory testing, both copper plated and zirconium-lined cladding systems offer significant potential for improved PCI resistance. Reactor evaluations are required to confirm this conclusion.

    Keywords:

    Zircaloy, stress corrosion, barrier cladding, irradiation effects, expanding mandrel testing, copper barriers, zirconium liners, pellet-clad interaction, iodine, cadmium


    Author Information:

    Tomalin, DS
    Metallurgist, Metallurgy Laboratory, General Electric Corporate Research and Development; and manager, Core Materials Testing, General Electric Nuclear Technology Department, Vallecitos Nuclear Center, Pleasanton, Calif.

    Adamson, RB
    Metallurgist, Metallurgy Laboratory, General Electric Corporate Research and Development; and manager, Core Materials Testing, General Electric Nuclear Technology Department, Vallecitos Nuclear Center, Pleasanton, Calif.

    Gangloff>, RP
    Metallurgist, Corporate Research and Development Center, Schenectady, N.Y.


    Paper ID: STP36676S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP36676S


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