Patent Number: 
Section: claims

1. A control rod for a pressurized water nuclear reactor, comprising:an absorber rod disposed in a sheathing tube, said sheathing tube surrounding said absorber rod in a gas-sealed manner, said absorber rod having a lower section with a circumferential surface;said absorber rod being formed with at least one recess in said lower section occupying at most only a part of said circumferential surface, to define a free space within said sheathing tube, said at least one recess being a longitudinal groove running on an outer peripheral surface in an axial direction of said absorber rod, said circumferential surface having a surface area adjoining said groove, said surface area of said circumferential surface being spaced from said sheathing tube for defining a gap between said surface area and said sheathing tube. 2. The control rod according to claim 1, which further comprises a noble gas filling the control rod with a filling pressure, measured at room temperature, greater than 1.5 bar.