Conceptual deigns of novel fuel geometries and alternate operating conditions have been evaluated for the purpose of maximizing the power density in BWRs, while maintain similar thermal margins to current BWR. Large assemblies with smaller fuel rods (LASP), annular fuel, and helical cruciform fuel (HCF) geometries were evaluated analytically. In addition, the hydraulics and lateral mixing in the HCF assemblies were studied experimentally. All options were found to allow for increasing the power density by 20% to 30%, under the current operating conditions. An optimization process constrained by using cylindrical square lattice, yielded a BWR with 65% Higher power Density (BWR-HD). It is achieved by utilizing the same number but wider assemblies, with 16x16 pin arrays and 30% shorter active fuel than the ABWR. In a separate investigation, annular fuel was used to allow the BWR to produce superheated steam. In this case water is boiled in the external channels first, then steam is separated and sent through the internal channels of the annular fuel. This allowed the exit steam temperature to reach 550°C, which yields a BWR with a thermodynamic energy conversion efficiency of 45%, well above the current 33%.