Superheating steam in a nuclear power station circuit - by water from reactor or steam generator circulation stream

摘要

Method of superheating vapour in a circuit of a nuclear power station, contg. a turbine with high and low press. stages, utilises, as heating fluid in the superheater, water under press, at the vaporisation temp., taken directly from the flow of recirculation or circulation water of the reactor or the steam generator. In a free-boiling steam generator heated by primary water under press. from the reactor, the water for superheating is taken from the generator in the recirculation return zone at a suitable level. In a pressurised water reactor using a steam generator of the once-through type incorporating successively an economiser, a vapouriser and a superheater, the water for superheating is taken at the vapouriser inlet. In a boiling-water reactor, the water is taken in the reactor vessel directly and at a suitable level in the recirculation water. The overall power output is increased by ca. 4%, compared to existing installations, because the whole of the steam from the generator is used in the high press. section of the turbine, and the rate of recirculation of water is increased, improving the heat transfer. In addn. the stability is improved and corrosion is reduced due to increase in circulation rate. The water circuit can be used for cooling if necessary; the risk of thermal shock in the generator is reduced and the power of the pumps can be reduced, of the order of 500 kw for a 1000 MW station.