Liquiducts can carry a crazy amount of steam. (2x a golden pipe, in half the space). Even more when you make them suck.
But more to the point, the buildcraft (glass) tanks can except any liquid flow rate from adjacent objects- so you can build a tall one that physically touching your reactor and pump/duct steam out of there.
(railcraft tanks can only drain fluids from the bottom blocks, so you loose a fair bit of area, glass tanks work at any level)