Characterisation of nano-scale precipitates in BOR60 irradiated T91 steel using atom probe tomography

•T91 steel was irradiated in BOR60 reactor at five different temperature/dose conditions.•The number density, volume fraction, size and composition of the early stage Mn, Ni, Si -rich clusters have been characterised by atom probe tomography.•After irradiation, Ni, Mn, Si and P segregation to carbide/matrix interface has been observed.•Fe clustering inside a carbide was observed after irradiation at 524 °C:15.4dpa, which has not been reported before. Atom probe tomography has characterised the microstructural changes in T91 steel after BOR60 reactor irradiation at five temperatures between 376 °C and 524 °C to doses between 14.6 dpa and 35.1 dpa. Irradiation-induced precipitation and segregation to carbide/matrix interface induced by neutron irradiation has been characterised. Atom probe tomography characterisation shows that Mn, Ni, Si -rich (MNS-rich) clusters form in T91 steel irradiated in BOR60 reactor at temperatures between 376 °C and 415 °C, which is not observed at higher temperatures 460 °C and 524 °C. The number density, volume fraction and composition of MNS-rich clusters have been characterised. Ni, Mn, Si and P is found to segregate at carbide matrix interface after irradiation at lower temperature and only P segregation is observed at 524 °C. [Display omitted]