Steam turbine and rotating blade

A blade mountable to a disc, the blade comprising:

• a blade platform;
• and
• a blade root extending from the blade platform, the blade root comprising a first hook and a second hook, a first neck between the first hook and the blade platform, and a second neck between the first hook and the second hook, wherein each hook comprises a contact surface and a non-contact surface and an angle between each contact surface and each non-contact surface is about 80.5°.

A turbine, comprising:

• a turbine blade, the turbine blade comprising a blade platform and a blade root extending from the blade platform, the blade root comprising a first blade hook and a second blade hook, a first blade neck between the first blade hook and the blade platform, and a second blade neck between the first blade hook and the second blade hook, wherein each blade hook comprises a contact surface, a non-contact surface, and an angle between each contact surface and each non-contact surface;
• a rotor disc comprising a slot, the slot comprising a first rotor hook and a second rotor hook, a first rotor neck and a second rotor neck, wherein each rotor hook comprises a contact surface in contact with a corresponding contact surface of the blade and a non-contact surface spaced from a corresponding non-contact surface of the blade, wherein the rotor contact surfaces are angled from the rotor non-contact surfaces at the same angle as the angle between the blade contact surfaces and the blade non-contact surfaces, and the angle is optimized to reduce local and average stresses between the contact surfaces.