BOILING WATER REACTOR SUBSTRUCTURE

PROBLEM TO BE SOLVED: To reduce vibration stress generated in each structure by fluid exciting force, and to resultantly prevent a damage or a crack having possibility of generation. SOLUTION: In this boiling water reactor substructure, a shroud 5 is provided in a reactor pressure vessel on the boiling water reactor substructure, and a plurality of internal pumps 2 are installed outside the shroud 5, and a coolant is sent to the core part by the pumps. Shroud support legs 17 for supporting the shroud 5 are provided between each internal pump 2 toward the center direction of the reactor pressure vessel 1, and hereby flow disturbance of the coolant caused by a conflict stream between each pump is avoided, and the average flow velocity is lowered by widening the area of an aperture between mutual shroud support leg 17 existing under the shroud. COPYRIGHT: (C)2004,JPO&NCIPI