Corrosion behavior of Zircaloy-4 cladding with varying tin content in high-temperature pressurized water reactors
- ABB Combustion Engineering, Windsor, CT (United States)
Fuel rods clad with Zircaloy-4 with varying tin contents (1.33 to 1.58% Sn) and annealing parameters (1.0 to 4.1 {times} 10{sup {minus}17} h with Q/R = 40,000 K) were irradiated in demonstration fuel assemblies in a high-temperature pressurized water reactor (PWR) to burnups in excess of 35 giga watt days per metric ton of uranium (GWd/MTU). The same cladding variants were subjected to long-term static water autoclave tests at 633 K of duration greater than 1,100 days. Production fuel rods fabricated with low-tin (1.33 Sn) and high-tin (1.55 Sn) Zircaloy-4 cladding were also irradiated in regular fuel assemblies in two high-temperature PWRs to burnups up to 48 GWd/MTU. Poolside cladding oxide thickness measurements were conducted on 167 high-tin rods and 67 low-tin rods during refueling outages. The measured, circumferentially averaged, peak cladding oxide thickness values ranged from 3 to 113 {mu}m. At high burnups, the oxide thickness on low-tin cladding was 30 to 40% lower than that on high-tin cladding. The long-term autoclave results also showed the beneficial effect of lower tin level on the corrosion rate, although to a lower degree than in PWRs. The 633 K water autoclave test appears to rank the corrosion resistance of the investigated Zircaloy-4 variants in the same order as in PWRs. Hydrogen analysis results indicated that tin level does not influence the hydrogen uptake of autoclave-tested samples. The observed in-PWR influence of tin level on the Zircaloy-4 cladding corrosion rate was incorporated in the ESCORE clad corrosion model by adjusting the pre-exponential term in the post-transition corrosion rate equation. A corrosion rate acceleration at high burnups may be related to either hydride precipitation at the metal oxide interface or to degradation of the oxide thermal conductivity.
- OSTI ID:
- 55682
- Report Number(s):
- CONF-930611--; ISBN 0-8031-2011-7
- Country of Publication:
- United States
- Language:
- English
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