The high-conversion boiling water reactor (HCBWR) has been studied as one of the next-generation BWRs. The HCBWR can be improved by the use of island-type fuel, which has mixed-oxide rods in the bundle interior and uranium rods only in the small region of the periphery, to have inherently negative void coefficient (i.e., negative void coefficient in infinite lattice configuration). The proposed reactor concept also has the sustainability to extend the light water reactor's period by ~180 yr and the compatibility with a conventional BWR system such that only substitution of fuel bundles and control rods is required. As an example case, the high-conversion advanced boiling water reactor II (ABWR-II) is evaluated.