a spacer for a fuel element of a boiling water reactor contains cells that are formed by inner partitions , which are disposed in a crisscross manner , and by outer partitions , which surround the inner partitions in a frame - like manner . a guiding device is placed on the spacer and contains a flow - through opening , which is located in an outer partition . the guiding device also contains a guiding element which , when viewed in the direction of flow of the coolant , is located in front of the flow - through opening , and is situated at a distance from the inner side of the outer partition , and interacts with the flow - through opening like a venturi nozzle .