Redesign of Sliding Pressure Startup System

The redesigned system is schematically described in Fig. 5.69. The startup bypass system in the original design is replaced by the separate recirculation system that consists of a steam drum, a heat exchanger, a circulation pump, and pipes. Neither the inlet nor outlet of the recirculation system are connected to the main lines, rather they are directly connected to the reactor vessel in order to form a closed space for pressurization like the recirculation system of BWRs. 

The role of the steam drum is to provide a water level and form a gas phase that consists of saturated steam. The pressure and hence samrated temperature increase with the amount of steam generated in the core like BWRs. There is no line from the gas phase of the steam dmm to the main steam line because the saturated steam is not used for warming and starting the turbines. In the redesigned system, the system is pressurized to the operating point (25 MPa) first, and then the supercritical steam (thermo-physicaUy similar to superheated steam) is sent to the turbines through the reactor vessel outlet nozzles and the main steam line. 

The circulation pump keeps the coolant flow rate in the loop. The water level in the steam dmm is controlled for stable pressurization. This is done by opening a water level control valve and dumping water from the steam dmm into the condensers. 

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