A steam turbine may include a turbine section including a rotor. An inner casing is provided about the turbine, the inner casing including an upstream end, a downstream end and an inner casing exhaust port positioned at the downstream end allowing exhaust steam to exit the inner casing. An outer casing is provided about the inner casing, the outer casing including an upstream end, a downstream end and an outer casing exhaust port positioned at the upstream end of the outer casing. A flow path extends between the inner casing and the outer casing through which the exhaust steam passes in an upstream direction from the inner casing exhaust port to the outer casing exhaust port. A flow barrier may be provided in the flow path between the inner casing and the outer casing.