Cooling sidewalls of turbine nozzle segments

A turbine nozzle segment includes at least one nozzle vane 46 extending between an inner band portion and an outer band portion, and at least one cooling channel 80 extending axially at least partially through at least one of the outer band portion and the inner band portion, the or each cooling channel comprising at least one inlet 82 which is isolated from a flow 72 of hot gases of combustion. The band portions may comprise sides surfaces for mating with side surfaces of adjacent segments, each side surface comprising a slot 74 for accommodating a seal, a respective cooling channel 80 being located between the seal slot and the hot gas flow 72. The cooling channel may comprise exit ports 84,88. The cross-section of the cooling channel may be oblong or circular, and two parallel cooling channels may be provided. The inner surface of the cooling channel may be provided with turbulator ribs, which may be angled. The cooling channel may be cast or machined or formed by under-cut and cover plate.