Spent fuel storage rack for BWR fuel assemblies

This patent describes for the use in storing nuclear fuel assemblies in a storage pool containing a coolant and having a pool floor, a fuel rack module. It comprises: a base plate to be disposed generally horizontally on the floor and having a horizontal surface area sufficient to support a fuel assemblies; uniformly spaced openings in the base plate, disposed in rows and columns throughout the surface area; fabricated cells of rectangular cross section extending over alternate openings along each row of the openings, the fabricated cells of each row being uniformly staggered by one opening with respect to the cells of its just adjacent rows so that the fabricated cells form a checkerboard like array; each of the fabricated cells having elongated walls mounted generally vertically on the base plate; each of the corners formed by the walls of each fabricated cell, which corners are internal of the periphery of the array, being disposed as closely adjacent as practicable to and face-to-face with a corner of an adjacent fabricated cell and joined by weld means so that substantially no space exists between adjacent cells. The cells being welded to their bottom ends to the base plate so that a strong compact modular structure is produced; neutron-absorbing means on the external surface of the fabricated cell walls except on the coextensive sections of the outer wall around the periphery of the array; and leveling pads are mounted under the base plate near the periphery thereof and adjustably engage the pool floor and intermediate leveling pads are mounted under cells within the fuel-rack module, the intermediate pads being uniformly disposed