Reactor core for a light water cooled nuclear reactor and control rod for the same

The present invention relates to a control rod (2) to be inserted between fuel assemblies loaded to a reactor core for a boiling water reactor, wherein wings (5) are arranged such that each spacing between the wings is 120 degrees and center lines extending from the respective wings in a horizontal cross section of the control rod constitute a regular triangle. Further the invention relates to a reactor core for a boiling water reactor having hexagonal fuel assemblies (1; 6; 9) containing fuels comprising uranium enriched with plutonium or plutonium and actinoid nuclides and Y-type control rods, wherein the Y-type control rod is a control rod according to claim 1, and the hexagonal fuel assembly has fuel rods (3) arranged in a regular triangular lattice pattern so as to form three sets of fuel rod rows, each set of fuel rod rows are parallel with a pair of opposing sides of the hexagonal fuel assembly, and the number of rows in two sets of fuel rod rows is equal to each other and is greater by one row than that of the remaining one set of fuel rod rows among the three sets of fuel rod rows.