Precipitate Evolution in Low-Nickel Austenitic Stainless Steels During Neutron Irradiation at Very Low Dose Rates
Neutron-induced microstructural evolution in response to long term irradiation at very low dose rates was studied for a Russian low-nickel austenitic stainless steel designated Х18Н9 that is analogous to AISI 304. The irradiated samples were obtained from an out-of-core support column for the pressure vessel of the BN-600 fast reactor with doses ranging from 1.7 to 20.5 dpa generated at 3.8x10-9 to 4.3x10-8 dpa/s. The irradiation temperatures were in a very narrow range of 370-375°С. Microstructural observation showed that in addition to voids and dislocations, an unexpectedly high density of small G-phase precipitates was formed that are not usually observed at higher dpa rates in this temperature range. A similar behavior was observed in a Western stainless steel, namely AISI 304 stainless steel, irradiated at similar temperatures and somewhat higher dpa rates in the EBR-II fast reactor, indicating that irradiation at low dpa rates for many years can lead to a different precipitate microstructure and therefore different associated changes in matrix composition than are generated at higher dpa rates. The contribution of such radiation-induced precipitation to changes in electrical resistivity was measured in the Х18Н9 specimens and was shown to cause significant deviation from predictions based only on void swelling.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 985042
- Report Number(s):
- PNNL-SA-64562; AT6020100
- Country of Publication:
- United States
- Language:
- English
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