1.4 ANALYTICAL TEM CHARACTERIZATION OF MODIFIED F82H and 14YW UNDER SIMULTANEOUS HELIUM AND NEUTRON IRRADIATION COMPARED TO ONLY NEUTRONS AT

SUMMARY An RAFM steel and an ODS ferritic alloy (F82H.mod3+CW and 14YW, respectively) were irradiated as part of the HFIR-JP27 irradiation experiment conducted in the High Flux Isotope Reactor to explore He effects in structural alloys. The in situ He injection (ISHI) technique is used to implant He up to 9 µm below the surface of a NiAl coated sample at He/dpa levels up to ~50. This report summarizes the current status of TEM characterization of the two irradiated alloys. The He-implanted side of the RAFM alloy exhibited significant swelling due to bubble and void formation - within the matrix, on pre-existing dislocations, and at interfaces within the material. The 14YW alloy exhibited significant swelling even in the absence of implanted He, primarily through large voids that formed on the ODS particles. In addition, significant radiation-induced segregation of the Cr was observed around oxide particles and on lath boundaries, and visible α′ particles could be detected via elemental mapping of the matrix of the 14YW alloy.