FUEL ASSEMBLY AND CONTROL ROD

PURPOSE:To protect a control element of a lower insertion rod cluster type control rod from exposure to a rapid coolant flow. CONSTITUTION:It has a plurality of fuel rods 21 charged with a plurality of fuel pellets and arranged inside of a channel box 32, upper and lower tieplates 22, 23 supporting the upper and the lower ends of the fuel rods 21, spacers 26 which are arranged multiply along the axis to bundle the fuel rods 21, and control element guide sheaths 25a, 25b arranged in between the fuel rods 21 and fixed by the upper and lower tieplates and the spacers 26. The lower inlet of the control element guide sheaths 25a, 25b are arranged remotely from the coolant flow for removing heat from the fuel rods 21. Therefore, the control element does not sustain a hydraulic vibration due to exposure to the rapid flow of the coolant and consequently, fretting corrosion is prevented.