The effect of radiation exposure on nano grain structured metals is of immense interest both from scientific and technological points of view. While in conventional metals, radiation produces various defects (point, line, surface and volume), it is not clear how these defects especially dislocations (line defects) and stacking faults (surface defects) can be accommodated in the relatively minute grains of nm-scale. The response of nano grain structured metals to neutron irradiation can be expected to be different from their large grained equivalents and this response could be in terms of the changes in mechanical properties post neutron irradiation or it could be an altered microstructure altogether. Very limited amount of research conducted in this area was a motivation to initiate the proposed study since the few attempts to study the effects of radiation on nano grain structured metals were only limited to observing the developed microstructure, and radiation effects on mechanical properties and the effect of processing routes were considered in only a few cases. This project is proposed to perform post irradiation examination (PIE) of ATR irradiated nc-Ni along with its conventional counterpart. The proposed PIE involves microhardness and tensile tests of 1 dpa samples along with microstructural characterization using X-ray diffraction and transmission and scanning electron microscopes at INL’s MFC and CAES. The expected period of performance is for 3 months starting January 2013. These results on nickel along with those obtained from PULSTAR reactor at NC State to relatively low dpa (~0.001 dpa) will enable us to investigate the influence of neutron irradiation on Hall-Petch relation. Earlier work on fcc Cu revealed decreased source hardening resulting in reduction of the slope of Hall-Petch plot and the current study will shed light on the plausible effect of crystal structure (carbon steel/bcc vs nickel and copper/fcc). Moreover, low dose irradiations of nc-Ni revealed some radiation softening similar to nc-Cu, but in contrast to ultrafine grained carbon steel which experienced insignificant radiation hardening. The softening in nc-Ni is suspected to be due to in-situ grain growth, but this contrasts with previous work which showed grain shrinkage after irradiation. Radiation effects at higher dose will be beneficial in examining these phenomena and providing evidence as to the superior radiation resistance of nano grain sized materials.