The Effect of the Trace Impurity Uranium on PWR Aqueous Corrosion of Zircaloy-4

    Published: Jan 1996

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    Commercial Zircaloy-4 specifications control natural uranium to <3.5 ppm by weight. Long-term in-pile corrosion tests were conducted on Zircaloy-4 coupons containing 0.1, 2.1, 10.6, and 24.1 ppm by weight of natural uranium. The objective of this testing was to determine the effect of the trace impurity uranium on the in-pile corrosion of Zircaloy-4. The tests were conducted in the advanced test reactor in Idaho at test temperatures of 355, 332, 310, and 274°C and at fast-neutron (>1 MeV) fluxes of > 1.0 × 1014 n/cm2-s. Limited testing was also conducted at lower fluxes.

    The pre-transition corrosion rates were observed to increase with increasing uranium content and flux level. The transition times were doubled at 2.1 ppm and quadrupled at 10.6 and 24.1 ppm uranium compared to the 0.1 ppm control ingot. Transition time differences were observed to diminish with decreasing fast-neutron flux. Post-transition corrosion rates also increased with uranium levels. The net effect on long-term corrosion is a reduction (X2 to X5) in corrosion film thickness for Zircaloy-4 containing uranium levels at the specification limit (3.5 ppm) compared to the 0.1 ppm control ingot. Based on the data presented, significant differences in PWR corrosion will develop as a result of varying natural uranium levels in ingots.


    Zircaloy-4, in-pile, PWR, corrosion, impurities, uranium, thorium, pretransition, transitory, steady-state, post-transition

    Author Information:

    Peters, HR
    Senior engineers, Lockheed Martin, Schenectady, New York

    Harlow, JL
    Senior engineers, Lockheed Martin, Schenectady, New York

    Committee/Subcommittee: B10.01

    DOI: 10.1520/STP16178S

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