Turbine for turbomachine

An assembly for a turbomachine of longitudinal axis, the assembly comprising a nozzle carried by an annular part which is fixed to an outer casing surrounding an annular row of moving blades arranged downstream of the nozzle, the nozzle comprising an outer annular platform from which a radial annular wall extends radially outwards, the annular part comprising a first wall extending in a direction comprising at least one radial component and an outer cylindrical wall extending longitudinally downstream from the first wall, the assembly further comprising a cooling circuit which comprises an intermediate annular chamber and an outer annular chamber each delimited longitudinally between the first wall of the annular part and the radial annular wall of the nozzle, the outer annular chamber being formed radially externally to the intermediate annular chamber, the outer cylindrical wall forming a partition radially between the outer annular chamber and the intermediate annular chamber, the outer annular chamber being further delimited, radially externally, by the outer casing, the cooling circuit comprising means of fluid communication between the intermediate annular chamber and the outer annular chamber, the outer cylindrical wall of the annular part resting, in the longitudinal direction, against an upstream face of the radial annular wall of the nozzle, the means of fluid communication between the intermediate annular chamber and the outer annular chamber comprising a plurality of upstream grooves of a first type formed on the upstream face of the radial annular wall, each upstream groove of the first type extending radially from an inner annular portion of the upstream face of the radial annular wall which delimits the intermediate annular chamber, to an outer annular portion of the upstream face of the radial annular wall which delimits the outer annular chamber.