A conceptual design is presented for an underwater thermoelectric nuclear power plant capable of producing continuous electric power at a 100-kwe level. The inherent advantage of a self-pressurized, natural circulation, pressurized water reactor (PWR) system is combined with a direct-conversion thermoelectric generator to provide a completely static system. The plant is designed for remote startup and completely unattended operation for over five years. Power is produced directly at 40 v; however, utilization of a solid-state inverter and storage batteries provides a peaking capability of several megawatts(e) at higher voltages. A low enriched core, with an inherently high negative temperature coefficient, is used which allows the control rods to be withdrawn completely at plant startup and to remain static throughout design life. No electronic controls, power monitoring, or feedback systems are required for operation or safety. Segmented thermoelectric elements (PbTe and BiTe) are used to obtain optimized performance over the rather small temperature drop available at the couple junctions. Although system weight is strongly dependent on design depth—-80,000 Ib for 18,000 ft'—-advanced pressure balancing concepts would allow weight reductions of 50 to 70% plus higher temperatures for improved thermoelectric conversion efficiencies.