Steam turbine plant

A steam turbine plant comprising:

• a boiler configured to change water into steam;
• an upstream turbine including plural stages of rotor vanes and plural stages of stator vanes, and configured to be driven by the steam from the boiler;
• a downstream turbine including plural stages of rotor vanes and plural stages of stator vanes, and configured to be driven by the steam from the upstream turbine;
• a condenser configured to change the steam exhausted from the downstream turbine into water;
• a collector configured to collect water from the steam which exists upstream of an inlet of the final-stage rotor vane in the upstream turbine, or the steam exhausted from the upstream turbine;
• and
• a collected matter path configured to cause collected matter in the collector to flow into:
• the steam between an outlet of the final-stage rotor vane of the upstream turbine and an inlet of the final-stage rotor vane of the downstream turbine,
• the steam between a collection place of the collected matter and the inlet of the final-stage rotor vane in the upstream turbine,
• the water between the condenser and the boiler,
• the steam extracted from an extraction port of the upstream turbine or the downstream turbine,
• a feed-water heater configured to receive the extracted steam from the extraction port, or
• a feed-water pump driving steam turbine configured to receive the extracted steam from the extraction port.