Abstract: The reactor containment structure is provided with a reactor containment vessel, a reactor containment chamber installed inside the reactor containment vessel to contain a nuclear power reactor, a pool installed inside the reactor containment vessel so as to be below the reactor containment chamber adjacently and in which an emergency cooling liquid is stored, an opening part for allowing the emergency cooling liquid to flow from the reactor containment chamber into the pool, a sump installed below the pool, a debris filtering body installed at the sump to filter debris contained in the emergency cooling liquid, a pumping system which sucks the emergency cooling liquid from the sump and discharges the emergency cooling liquid into the reactor containment chamber, and a debris trapping part installed in the pool to trap the debris, wherein the debris trapping part intersects with a flow path of the emergency cooling liquid.

Abstract: In a steam plant, scale adhesion to the inside of a specific device is prevented, while reducing the amount of an agent such as hydrazine to the lowest possible level. A temporary change in the chemical environment or an approximately periodic variation in the chemical environment is brought about in a channel (21) inside the prescribed device, during operation of the steam plant.