Reactor core with hexagonal fuel bundle cans

The cans of fuel bundles of fast reactors are provided with inlet and outlet sleeves through which coolant flows under pressure into the bundles. The difference between pressures at inlet and outlet acts on the walls of the cans and causes undesirable stress. In order to suppress this stress, coolant is delivered into the space around the cans. With the action of external pressure on the cans, thinner walls can be used and spacing between adjacent cans reduced. The thus obtained space may be filled with further fuel and higher power output thereby achieved. Reduced stress and thereby also reduced deformation of cans makes it possible to leave the fuel in the reactor for a longer period of time. (E.S.)