Nuclear Mpd Gas Turbine Power Plant

In MPD generators employing alkali-metal-seeded inert gases as the working fluid, the possibility of utilizing magnetically-induced non-equilibrium ionization has been established on theoretical grounds and there is supporting experimental evidence. Joule heating of the working plasma preferentially enhances the electron temperature, producing plasma electrical conductivity levels much higher than apply for thermal equilibrium ionization. The effect is increased by increasing the applied magnetic field and (within limits) by reducing the operating pressure level. If high levels of electrical conductivity can be maintained in this non-equilibrium mode, a cycle in which temperature levels are dictated on thermodynamic grounds only can be selected. The optimization of a Brayton cycle in terms of thermodynamic efficiency and specific power is considered. The proposed cycle consists simply of a heat source, MPD generator, recuperator, heat sink and compressor, the latter being driven either electrically or by a turbine in the circuit. The general features of a land-based nuclear, recuperative closed-cycle MPD power plant are presented. An all-graphite prismatic core helium-cooled nuclear reactor is the heat source. A single gas thermodynamic cycle is considered rather than combined gas and steam cycles, to avoid the hazards of water-graphite reactions due to in-leakage from a high pressure steam cycle and to simplify the plant and its control. The detailed plant layout-suggested is given theoretical and practical justification. Detailed parametric surveys on the MPD generator and the cycle thermodynamics have been performed and some of the combined results are presented. With a reactor outlet temperature of 1800°K, gas turbine inlet temperature of 1200°K, single intercooling and cycle losses estimated from present technological data, it is shown that net plant efficiencies of 55-60% can be obtained. Fuel temperatures for a range of reactor and fuel geometries, reactor outlet temperatures, pressure and power densities and plant output powers are presented with reference to the results of the parametric cycle calculations. The MPD generator, turbomachinery, reactor and heat exchanger have been drawn to scale for a number of cases and a tentative layout for a land-based 500 MW(e) plant is shown. No attempt has been made to estimate the commercial viability of this type of plant. Potential approaches to overall power cost minimization are discussed. The technical and economic merits of a nuclear MPD power plant (including safety and control) are compared with other nuclear power generating systems, with special reference to nuclear-gas turbine power plants. (author)