Close, rhn, but a close miss is still a miss
320 steam/t for the turbine to go at 100%.
Of course, there is no boiler that outputs exactly 320 steam/t, so you can either use the already suggested 36 LP and have some left over, or use a 27 LP and be a little below 100%.
Don't build a 18 HP though. Those are not a good deal as far as bang for your buck goes.