Method for cooling down a steam turbine

A steam turbine unit comprising:

• a steam turbine which comprises a steam inlet region, an exhaust steam region and a blading region which is surrounded by a turbine housing and is arranged axially in between,
• a cooling fluid inlet which is closeable and openable by a closure member, and which is arranged upstream of the exhaust steam region with respect to a flow direction of steam,
• a valve comprising a steam inlet and a steam outlet, and
• a drainage device comprising:
• a junction that is disposed downstream of the steam inlet and upstream of the steam turbine;
• and a drainage device line that connects the junction to the cooling fluid inlet and to a drain,
• wherein during normal power operation the steam flows through the valve, through the junction, and into the steam turbine, and the drainage device line leads drainage from the junction toward the drain in a drainage direction, and
• wherein during a cooling operation cooling fluid flows from the cooling fluid inlet, through the drainage device line in a direction opposite the drainage direction, to the junction, and then to the steam turbine.