ROLE OF THE OXIDATION RATE ON THE HYDRIDING OF ZIRCONIUM ALLOYS IN GAS ATMOSPHERES CONTAINING HYDROGEN
Mechanism studies showed that the primary factor controlling the hydrogen absorption in zirconium alloys in gas atmospheres containing hydrogen is the rate at which oxidant (water) is transferred to the metal surface from the environment. The oxidation rate of Zircaloy-2 is shown to be pressure independent from 1500 psi to below 1 mm water pressure. When an oxidant is present, remarkable inhibition of gas phase hydriding at 400 deg C occurs even up to 1000 psi hydrogen pressure. However, at sufficiently low oxidant concentrations in the presence of an inert carrier gas, the oxidation rate can be reduced, due to local depletion of the oxidant. Once the oxidation rate is diffusion limited, catastrophic hydriding can occur at low hydrogen pressure (7 mm) and low temperatures (150 deg C), in a few days, with pre-existing autoclave films offering only transitory protection. The electrical resistance of ZrO/sub 2/ corrosion films decreased about 10/sup 6/ ohms when the atmosphere was shifted from oxidizing to nonoxidizing, probably due to an increase in the oxygen anion vacancy concentration. This suggests the initiation of gas phase hydriding may be related to a higher hydrogen diffusion rate made possible by the higher concentration of oxygen vacancies in the film. (auth)
- Research Organization:
- General Electric Co. Hanford Atomic Products Operation, Richland, Wash.
- DOE Contract Number:
- AT(45-1)-1350
- NSA Number:
- NSA-17-036225
- OSTI ID:
- 4640133
- Report Number(s):
- HW-76562(Rev.); CONF-21-3
- Country of Publication:
- United States
- Language:
- English
Similar Records
THE ROLE OF THE OXIDATION RATE ON THE HYDRIDING OF ZIRCALOY-2 BY GASEOUS HYDROGEN. Interim Report No. 3
HYDRIDING OF ZIRCONIUM AND URANIUM IN ORGANIC COOLANTS