Thorium-based fuels can be used to reduce concerns related to the proliferation potential and waste management of the conventional light water reactor (LWR) uranium fuel cycle. The main sources of proliferation concern and radiotoxicity are the plutonium (Pu) and higher actinides generated during the burnup of standard LWR fuel. A significant reduction in the quantity and "quality" of the generated Pu can be achieved by replacing the U 238 fertile component of conventional low-enriched uranium fuel by Th 232. A heterogeneous seed-blanket assembly concept for the utilization of thorium in a Russian pressurized water reactor (VVER-1000) has been developed. The concept is based on a seed-blanket unit (SBU) which is a one-for-one direct replacement for a standard VVER fuel assembly. The approach is intended to be retrofittable into a conventional VVER-1000 with no or minor hardware modifications, but improve on the proliferation and waste management performance of a conventional once-through VVER-1000. Studies have been performed to develop a preliminary design, and quantify performance and safety characteristics. Initial thermal-hydraulic experiments and fabrication of fuel samples, and irradiation in the IR-8 reactor at RRC-KI have also been performed. While the fuel has to be designed to withstand relatively high burnup, and there are other challenging issues that need to be addressed in developing a full design, no "show-stoppers" have been identified in the technical, safety and licensing performance of this fuel. This concept is therefore worthy of continuing further investigation.