Patent Number: 053352521
Section: abstract

A steam generator which finds particular application as a superheater and reheater for transfer of heat from the gas coolant of a nuclear power reactor to a secondary fluid medium. The lower pressure reheater is located inside of the nuclear pressure vessel containing a reactor core, as is the high pressure main steam tube bundle which is comprised of an economizer/ evaporator tube bundle stage and an initial superheater tube bundle stage. The remaining superheater tube bundles which comprise the intermediate superheater and the finishing superheater are located outside of the nuclear pressure vessel, where they are heated regeneratively by reheat steam which is emerging from the nuclear pressure vessel at a temperature higher than required by the reheat turbine, The main steam system can be designed for either subcritical or supercritical pressure operation. The main steam tube bundle, located inside of the nuclear pressure vessel, operates with forced once-through flow while the plant is running at normal load and operates with water recirculation while the plant is running at low load and during start-up to provide satisfactory water velocities in the heat transfer tubes of the main steam tube bundle throughout the operating range. A recirculation system extracts water from a location between the tube side outlet of the initial superheater tube bundle stage and the tube side inlet of the intermediate superheater tube bundle to the tube side inlet of the economizer/evaorator tube bundle stage by means of a recirculation pump.