Rotor assembly with independent platforms and method for assembling such a rotor

A turbomachine turbine rotor assembly of axis comprising:

• a rotor disc centred on the axis and having cavities which open out at an outer periphery of the disc, two circumferentially adjacent cavities delimiting a tooth of the disc,
• movable vanes each comprising a root mounted in one of the cavities of the disc and a blade extending from the root,
• a plurality of platforms for holding the movable vanes in the cavities of the disc, each platform being circumferentially mounted between two circumferentially adjacent movable vanes, and
• a flange for holding the movable vanes in the cavities,
• wherein each platform includes:
• a stream wall configured to delimit a gas flow stream of the turbomachine,
• an L-shaped downstream hook with the vertical portion of the L radially extending from the stream wall and the horizontal portion of the L housed in a corresponding holding hook positioned at the top of a tooth of the disc;
• and
• an upstream hook substantially radially extending from an upstream zone of the stream wall and axially held between the flange and the disc.