PURPOSE: To improve drain-removing performance by a method wherein a pair of steam guide plates in the shape of a triangle in cross section are arranged in the longitudinal direction of a drum body approximately in the same height as the central axis of a horizontally installed cylindrical drum body, provided with a moisture content separator and a heating pipe group, with a buffer plate therebetween, and a streamline type steam guide plate is arranged in a low temperature heat steam inlet pipe.

CONSTITUTION: A moisture content separation heater applied for an atomic power plant is provided in a horizontal drum body 1 with a moisture content separator, a heating pipe group, and a buffer plate 3 in a U-shape in cross section and at its lower part with a low temperature reheat steam inlet pipe 2. In this case, a pair of steam guide plates 15 in the shape of a triangle in cross section is arranged in the longitudinal direction of a drum body approximately in the same height as that of the central axis of the horizontally-installed cylindrical drum body 1 with the baffle plate 3 therebetween. The steam guide plate 15 is arranged below the upper edge part of the steam inlet partition plate 4 of the inlet of a steam distribution passage A in parallel to the baffle plate 3. A streamline type steam guide plate 16 is installed in the low temperature reheat steam inlet pipe 2. Further, a flow straightening means 17 formed of a lattice-form wire netting is attached on the under surface of each steam distribution passage plate 6.