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In this paper, microtensile testing is demonstrated to be a viable technique for measuring irradiation hardening and reduction of ductility of ion irradiated hot isostatic pressed SA508 ferritic/bainitic steel. Ion irradiation with He2+ was used as a surrogate for neutron irradiation to reach a damage level of 0.6 dpa (Kinchin-Pease). The mechanical properties of four unirradiated microtensile steel specimens were measured and compared to the bulk properties: when averaged the 0.2% proof stress was 501.6 ± 56.0 MPa, in good agreement with the macrotensile 0.2% proof stress of 456.2 ± 1.7 MPa. On the basis of the agreement between microtensile and standard tensile 0.2% proof stress in the unirradiated material, it was possible to directly measure irradiation induced hardening from ion irradiation performed with He2+ ions to a dose of 0.6 dpa. Microtensile testing of the ion irradiated steel revealed an increase in 0.2% proof stress of approximately 730 MPa. The irradiation hardening measured by nanoindentation was 3.22 ± 0.29 GPa. Irradiation hardening was higher than that previously observed in neutron irradiated low alloy steels exposed to similar doses at low temperatures (

The oxidation mechanism and products of U3Si2 accident tolerant nuclear fuel in flowing air up to 750 °C is reported. Differences between observed and theoretical mass gains for complete oxidation is due to un-oxidised Si that forms nano-crystalline regions of Si. Some Si rich regions are protected by the formation of UO2, which is thermodynamically preferential to oxidise before Si. The UO2 is further kinetically oxidised to form nano-crystalline U3O8. The nanostructure formed, accompanied by large volumetric expansions during oxidation produces pulverisation of fragments into powder, which may have serious consequences for fuel integrity if exposed to oxidative atmospheres.