BOILING WATER REACTOR AND ITS OPERATION METHOD

摘要

PROBLEM TO BE SOLVED: To provide control rods securing sufficient control rod value without significant modification of a facility and without increase of a production cost. SOLUTION: A long wing control rod 6 having control rod wings extending in four directions is disposed between channel boxes on the opposite angle of a square bundle area constituted of a fuel assembly 2 surrounded the four channel boxes 1. A short wing control rod 7 in which the length of the control rod wing is the same degree as the width of the fuel assembly 2 is disposed between the channel boxes of the center of the square bundle area.