The question, “Where can the generation of new material property data reduce overly conservative design in reactor systems?” presently exists in the nuclear industry. The question is answered by identifying where conservatism exists relative to determining material property variations. Several areas are reviewed to identify conservatism and the sensitivity of structural integrity evaluation results to the property variations. The areas reviewed were fluence dependence of the transition temperature, fracture toughness, the drop in upper shelf toughness, the arrest toughness, the material thermal properties, and the fatigue crack growth rate.