Cooling structure for turbine, and gas turbine

A cooling structure for a turbine, comprising:

• disks rotating integrally with blades about a rotational axis in a predetermined rotational direction, the disks being disposed in a plurality of stages along the rotational axis;
• and
• disk holes formed in a plurality in the disks along a circumferential direction, the disk holes supplying cooling air to disks on a downstream side to cool the blades,
• wherein at least one of the disks is a motive power recovery type disk in which at least one of the disk holes is set such that an outlet absolute circumferential velocity vector, which is a component in the rotational direction of a velocity vector of the cooling air at an outlet of the disk hole, is smaller than an inlet absolute circumferential velocity vector, which is a component in the rotational direction of a velocity vector of the cooling air at an inlet of the disk hole,
• wherein the rotational direction of the disk is defined as a positive direction and the direction opposite the rotational direction is defined as a negative direction.