STEAM GENERATOR

PROBLEM TO BE SOLVED: To provide a steam generator that can improve plant efficiency without increasing the power of a primary coolant pump.SOLUTION: A steam generator 1 according to an embodiment includes: a container 10 having a primary-side water chamber 11 and a secondary-side heated part 13; a partition plate 15 which partitions the primary-side water chamber 11 into an intake-side water chamber 16 and an outlet-side water chamber 17; an intake nozzle 18 which guides primary-side fluid to the primary-side water chamber 11; a heat transfer pipe group 12 which guides the primary-side fluid from the intake-side water chamber 16 to the outlet-side water chamber 17 through the secondary-side heated part 13, and exchanges heat at the secondary-side heated part 13; an outlet nozzle 19 which guides the primary-side fluid from the outlet-side water chamber 17 to a primary-side fluid pump 25; and a water collection pipe 21 which is connected to an intake side 19b of the outlet nozzle 19 in the outlet-side water chamber 17. The water collection pipe 21 is formed increasing in internal diameter from an outlet-side end 21a connected to the outlet nozzle 19 toward an intake-side end 21b.