This column would absorb incoming neutrons from all directions, except for one, in which neutrons would be allowed to pass through, acting as a neutron diode. I could see this being used to allow for more extreme RBMK fuels to be used without risk of meltdown, for example, having fuels with a linear or negative quadratic flux function to be placed in a row, however, instead of a runaway reaction, death-spiraling as the neutron flux becomes stronger and stronger, the polarized columns allow neutrons to flow in a single direction, going from one dangerous fuel to another without going back. Picture for reference.