Ultra-fine grain (UFG) metals with a relatively large volume of interfaces are expected to be more radiation resistant than conventional metals; grain boundaries act as unsaturable sinks for neutron irradiation induced defects. Effects of neutron irradiation on conventional and ultra-fine grain structured carbon steel are studied using the PULSTAR reactor at NC State University to relatively low fluence (∼1.15 × 10^-3 dpa). The low dose irradiation of ultrafine grained carbon steel revealed minute radiation effects in contrast to the observed radiation hardening and reduction of ductility in its conventional grained counterpart.