In view of the considerable amount of 237Np produced as a by-product in nuclear power reactors, possible utilization of this nuclide in the nuclear fuel cycle has been studied. In particular, the performance of a gas-cooled fast breeder reactor as a neptunium burner was assessed. In a neptunium burner, a major fraction of the 237Np is converted to 238Pu. The 238Pu could be discharged and used to fabricate denatured plutonium fuel elements for light water reactors (LWRs), which are considered to be more proliferation-resistant than ordinary plutonium fuel elements. A strategy was developed and mass flows were computed for a denatured plutonium LWR strategy using uranium, plutonium, and neptunium recycling.