Investigation of environmentally assisted fracture of metallic nuclear waste package barrier materials in simulated basalt repository environments
Statically loaded corrosion tests, slow strain rate (SSR) tests, and fatigue crack growth rate (FCGR) tests were conducted to evaluate the relative susceptibility of two titanium-base nuclear waste package candidate structural barrier materials Ti-grade 2 and Ti-grade 12-to environmentally enhanced cracking in a simulated repository environment. Statically loaded corrosion tests were done in oxic basalt ground water at 250/sup 0/C; SSR tests were done in oxic basalt ground water at 150, 250, and 300/sup 0/C and in air at 20 and 250/sup 0/C; and FCGR tests were done in basalt ground water, fluoride-ion-enhanced basalt ground water, high-purity water, and air at 90/sup 0/C. The following conclusions can be drawn: the general corrosion rate of statically loaded corrosion coupons was very low in a 3-mo test, and no pitting or cracking of the specimens was observed. Ti-grade 2 and Ti-grade 12 exhibited strain rate dependent ductility diminution in SSR tests. The ductility diminution was most severe in Ti-grade 2 at 300/sup 0/C and in Ti-grade 12 at 250/sup 0/C. For of Ti-grade 12 it was found to be highly orientation dependent. The ductility diminution was also found in tests conducted in air as well as in those conducted in the basalt ground water environment; however, the extent of the degradation was less in air. The ductility diminution cannot be attributed to stress corrosion cracking because the fracture mode was microvoid coalescence in all tests. Evidence obtained in the current study and correlation of the present results with results obtained by other researchers indicate that dynamic strain aging is responsible for the loss of ductility. The FCGR of Ti-grade 2 and Ti-grade 12 was not affected by any of the environmental conditions used in this study, which indicates that no environmental cracking mechanism is operative under the conditions tested (90/sup 0/C, oxic ground water, and frequencies from 0.01 to 5 Hz).
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 6601741
- Report Number(s):
- PNL-4379; ON: DE83005126
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
GROUND WATER
CORROSIVE EFFECTS
RADIOACTIVE WASTE DISPOSAL
GEOLOGIC DEPOSITS
HIGH-LEVEL RADIOACTIVE WASTES
TITANIUM BASE ALLOYS
CORROSION
CRACK PROPAGATION
FATIGUE
STRAIN RATE
BASALT
ENGINEERED SAFETY SYSTEMS
EXPERIMENTAL DATA
MATERIALS TESTING
PACKAGING
ALLOYS
CHEMICAL REACTIONS
DATA
HYDROGEN COMPOUNDS
IGNEOUS ROCKS
INFORMATION
MANAGEMENT
MATERIALS
MECHANICAL PROPERTIES
NUMERICAL DATA
OXYGEN COMPOUNDS
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
ROCKS
TESTING
TITANIUM ALLOYS
VOLCANIC ROCKS
WASTE DISPOSAL
WASTE MANAGEMENT
WASTES
WATER
360103* - Metals & Alloys- Mechanical Properties
360105 - Metals & Alloys- Corrosion & Erosion
052002 - Nuclear Fuels- Waste Disposal & Storage