This publication provides information about the master curve approach for assessing the structural integrity of reactor pressure vessels (RPVs) under current and future operation and accident conditions in nuclear power plants (NPPs). This direct measurement of fracture toughness approach is technically superior to the correlative and indirect methods used in the past to assess irradiated RPV integrity. The results in the report should allow utility engineers and scientists to directly measure fracture toughness using small surveillance sized specimens and apply the results using the master curve approach for RPV structural integrity assessment in NPPs.