Storage module for nuclear fuel assemblies

A storage module or rack is disclosed for storage of nuclear fuel assemblies in a water-filled pool comprising an array of storage tubes arranged in a checkerboard pattern and attached to one another along their corners. Each tube thus forms a storage cell for a fuel assembly and the spaces between each four adjacent tubes form intermediate fuel assembly storage cells. The storage tubes are formed with spaced double walls between which is contained a layer of neutron absorbing material to assure that the array of stored fuel assemblies remains subcritical. Provision is made for free circulation of water through the storage cells to extract heat from the stored assemblies. The storage module maximizes the number of fuel assemblies that can be stored in a given space while minimizing the material used in its construction