Small punch testing for irradiation embrittlement. Final report
- Failure Analysis Associates, Inc., Menlo Park, CA (United States)
Fracture mechanics analyses are used to evaluate nuclear reactor vessel integrity. These analyses require knowledge of a range of vessel material mechanical properties, particularly fracture properties. Estimation of vessel material fracture properties is currently made indirectly via correlations between embrittlement and vessel steel chemistry and neutron fluence, and by standard Charpy testing (for transition temperature or RT{sub NDT}) of surveillance material. The small punch test approach is a miniature specimen mechanical test which, based on accumulated experience with fossil plant steels, shows significant application potential for in-service nuclear reactor vessel irradiation embrittlement evaluation. The small punch test specimen is small enough to potentially overcome the surveillance material availability problem (30 small punch test specimens can be easily removed from a single standard half-Charpy bar) and even permit a direct vessel material interrogation by non-disruptive removal of miniature samples from the vessel. An immediate, near-term benefit of the small punch test approach will be the conservation of surveillance material. The results of preliminary feasibility testing on a heat of reactor vessel steel weld metal in the unirradiated, irradiated, and irradiated + annealed conditions show that the small punch test transition temperature correlates with the standard Charpy transition temperature. In addition, application of the small punch test-based fracture toughness (K{sub Ic}, J{sub Ic}) estimation method developed on a previous EPRI project (RP2426-38) produced toughness estimates for the irradiated steel within the {+-}25% accuracy range demonstrated on RP2426-38. The results show that the small punch test can be a viable means of evaluating irradiation embrittlement of reactor vessel steels. Recommendations are provided for further developing the test method for this application.
- Research Organization:
- Electric Power Research Inst. (EPRI), Palo Alto, CA (United States); Failure Analysis Associates, Inc., Menlo Park, CA (United States)
- Sponsoring Organization:
- Electric Power Research Inst., Palo Alto, CA (United States)
- OSTI ID:
- 120932
- Report Number(s):
- EPRI-TR-105131; TRN: 95:007675
- Resource Relation:
- Other Information: PBD: Aug 1995
- Country of Publication:
- United States
- Language:
- English
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